Located at Culham, UK, JET (Joint European Torus) is an experimental fusion energy device in which, by creating temperatures greater than that of the sun (around 100 million°C) and applying magnetic confinement, fusion of atomic nuclei takes place. The next stage of fusion technology development has started with the building of ITER, which is eight times larger in volume than JET. ITER is one of the most challenging scientific experiments ever undertaken, leading initially to a trial generating station followed by full-scale generators, supplying fusion energy to the grid by the end of this century.

The business benefits that Dassault Systèmes methodology delivers to the ITER supply chain derive from using 3D model technology to develop and communicate information.

Some of the most complex elements of JET are the remote handling systems. These emulate human movement controlled from remote stations several hundred meters away and are developed by JET operator UKAEA in conjunction with Oxford Technologies staff.

Simon Mills, Oxford Technologies' Engineering Director explained the system's operation. "A force reflecting master manipulator transmits a human operator's motions and forces to a remote slave manipulator inside the tokamak* chamber. The system performs maintenance tasks without the need for engineers to enter the hostile tokamak environment. Some 20000 tasks have been performed at JET over the last 12 years. These include installing components, changing configurations and updating systems inside the tokamak. Maintenance and enhancement periods occur at intervals of 3-4 years and may last from a few months to more than a year. Between these 'engineering breaks', the remote handling systems are used to develop techniques for performing future maintenance tasks."

Once ITER is operational, there will be no human access to the tokamak or other areas of the plant containing highly active systems. All maintenance and future upgrades will then be carried out remotely.

All companies in the ITER and JET engineering supply chains use CATIA, DELMIA, 3DVIA Composer and other Dassault Systèmes PLM software and methodology. One company that is involved with both JET and ITER technology provision is Oxford based, Desktop Engineering (DTE).

Managing director Geoff Haines talked about the company's role. "JET and ITER bring together many engineering and scientific specialists who need to communicate and operate in a concurrent and collaborative way. DTE provides design to manufacture PLM software and support services to companies involved with both the buildings and structures as well as the systems that they house."

Simon Mills added: "DTE helps us to derive maximum engineering and commercial advantage from our Dassault Systèmes technology with ongoing training and support. They have introduced us to the newest methodologies which save time and money by increasing productivity and overall efficiency.

"One example of this was the introduction, by Desktop Engineering, to Oxford Technologies, of 3DVIA Composer to animate CATIA generated 3D imagery. This not only allows them to refine their designs through the better cognition that kinetics enables, but also gives all stakeholders a clear understanding of the equipment in its context and detail."

Communication in 3D is the norm since the deployment of 3DVIA Composer allows non-CATIA users visual access and interaction with 3D digital models of Oxford Technologies' remote handling systems.

Geoff Haines commented: "The production efficiencies derived from specifying Dassault Systèmes technology throughout JET and ITER supply chains are augmented by the introduction of 3DVIA Composer. It provides simple access to 3D data and lets people understand how complex systems operate and interact."

Oxford Technologies' contribution to JET and ITER relies on the ability to develop and integrate innovative engineering solutions. These must operate reliably in the harsh yet delicate environment of the tokamak.

Simon Mills concluded: "Devising articulated boom type devices, and ancillary components, to operate within the tokamak at maximum efficiency, safety, precision and speed, requires an engineering design platform that allows our full creativity and ingenuity to flourish. It also needs a technology partner, in this case Desktop Engineering DTE, to work with us and introduce and support economical, scaleable and fully compatible software."

Geoff Haines added: "The results of today's fusion engineering will secure the world's energy future. Its PLM foundation is optimised to assure future-proof scientific, engineering and commercial success for the project and the enterprises that it comprises."

Nick Lerner is with Oxford Technologies, Abingdon, Oxon, UK. www.oxfordtechnologies.co.uk. For more information, visit www.fusion.org.uk; www.dte.co.uk; www.3ds.com/isa

* tokamak: a toroidal apparatus for producing controlled fusion reactions in hot plasma.

Like all power generation plants, the Browns Ferry Nuclear (BFN) Plant, in northern Alabama, USA, faces many challenges to meet the power demands of a growing and urbanising population. With Alabama's frequent and intense storms, the challenges posed by lightning had proven to be especially trying due to repeated strikes to the off-gas stack.

Today, BFN prides itself on safe, efficient, and affordable electric power generation for its customers. As the first nuclear power plant of the Tennessee Valley Authority (TVA), the nation's largest public power company, BFN was the first nuclear plant in the world to generate more than 1 billion watts of power and was the world's largest when it began operation in 1974. In 2006 BFN helped TVA achieve 99.999 per cent operational reliability for the fifth year in a row. But a decade ago, lightning strikes to BFN's off-gas stack were hampering reliability.

"The off-gas stack was originally protected by Franklin rods, but equipment on the stack and around its base (was) routinely damaged during lightning storms," says Rick Brehm, a TVA manager of electromagnetic interference and instrumentation, and control systems. "Lightning strikes to the stack were observed."

The damage from strikes required considerable equipment replacement and repair. While the automated monitoring equipment was offline, extended periods of human monitoring were necessary, which increased the workload and expense.

To improve reliability and reduce downtime, BFN turned to Lightning Eliminators & Consultants, Inc (LEC), which specialises in lightning prevention technology, a relatively new innovation in the lightning protection industry. BFN's move is not uncommon; a growing number of respected power generating utilities have successfully reduced costs by choosing engineered lightning prevention systems to avoid storm-related damage.

Unlike antiquated lightning rods, which collect and direct lightning at a site, charge transfer technology prevents direct strikes by reducing the local electrical field to below lightning-collection potential. LEC's charge transfer device, the Dissipation Array System or DAS, has been installed at industrial facilities around the world and is custom-engineered to interface with almost any structure.

To design a comprehensive protection scheme, LEC took into account factors such as the off-gas stack's location, size, shape, equipment, geography, and exposure to lightning activity. They then engineered, and deployed an integrated lightning prevention system for BFN, which included DAS strike prevention. Spline Ball Terminals (SBTs), a form of hybrid preventer/collector, were used to augment the protection for the sensitive equipment around the off-gas stack's landings.

"The result has been no known lightning strikes to the off-gas stack in almost 10 years," says Brehm. "Instead of using our resources to repair broken equipment and pay emergency overtime, we're preventing the problem in the first place."

As part of an internal review process, BFN consulted a database of lightning activity to determine the number and location of lightning strikes around the off-gas stack in the three years before and after DAS implementation. They compared the number and location of lightning strikes within 500 metre, 3, 6, and 10 mile radius circles of the off-gas stack for these periods (Figs. 2 and 3).

"Following DAS implementation, we found an 80 per cent reduction in lightning strikes within 500 metres of the off-gas stack," explains Brehm. "The weighted data for strikes in the wider areas showed no change of statistical significance, though lightning frequency increased by almost 63 per cent in a 10 mile radius around the stack in the three years after DAS implementation. The data shows us the DAS system works. It has undoubtedly saved us from tons of potential lightning strikes since it's been implemented.'

In another test of DAS's effectiveness, BFN recently monitored the voltage drop on a ground cable downcomer from the DAS array on the off-gas stack down to the ground via a voltage sensor. The monitoring lasted about six months, during which time they detected no lightning strikes and current flow remained in the milli-amp range.

"We saw milli-amps of current flowing up and down the downcomer," says Brehm. "This indicated that DAS was making the stack a less attractive strike target. The data showed DAS functioning as intended."

"It's preventing strikes to the protected area and proving to be an effective long-term solution." Because of the DAS prevention system's success in protecting the off-gas stack from lightning strikes, BFN is looking into extending the area of protection to a nearby intake pumping station, which recently sustained motor damage due to lightning.

LEC has used Dissipation Array protection systems to provide engineered areas of protection in a variety of public utilities and facilities.

Del Williams is a technical writer based in Torrance, California. LEC Inc is based in Boulder, Colorado, USA. www.LECglobal.com.

The energy and power generation markets have rarely left the spotlight, whether it is the price of crude oil or plans to instigate or reinitiate nuclear expansion programmes.

The main driver behind such media attention is consumer and business demands for affordable energy accompanied by the negative aspects of global warming caused by carbon dioxide (CO2) emissions.

As published by the Nuclear Energy Institute (NEI), Nuclear generation offers operators the lowest operating cost per MWh accompanied by minimal CO2 emissions when compared with fossil fuels but still suffers from lengthy refuelling outages.

To combat this drawback, efforts to maximise generator productivity in nuclear plants have focused on reducing plant refuelling outages.

There have been many advances in reactor shutdown techniques with the NEI recently reporting that average outage times had fallen by 64 per cent from over 100 days (1990) to around 40 days (2007).

Refuelling outages are typically completed every 15-18months with reactor shutdown and start-up as the start- and end-points.

During reactor shutdown and start-up, accurate measurements of both oxygen (O2) and hydrogen (H2) within the reactor coolant system (RCS) are critical before the reactor is depressurised and opened for maintenance to avoid an explosive mix.

Most new methods to accelerate this process rely on continuous real-time oxygen and hydrogen measurement using Orbisphere instruments rather than intermittent sampling using gas chromatography or other offline methods.

During recent trials, a top five global nuclear operator evaluated a number of different methods used in Pressurised Water Reactor (PWR) shutdown and start-up in order to find a balance between speed, efficiency and safety.

The results were staggering when considering how each could be implemented and the benefits it could bring across a nuclear fleet. The two methods discussed here are physical degassing and hydrogen-peroxide (H2O2) injection.

The first method, physical degassing using nitrogen, was an earlier method used to remove excess hydrogen but can be slow and costly due to the cost of storage and treatment of the nitrogen and other radioactive waste gases before release.

For a 1300MW block with a theoretical reactor shutdown time of 10-13hrs dependent on nitrogen flow rate, it is generally accepted that 24hours is required - this is obviously faster for smaller (900MW) reactor blocks.

Hydrogen peroxide injection, the second of those trialled, absorbs hydrogen to create water. This can be used to reduce the level of hydrogen (illustrated in Fig.1) however it relies on the use of real-time instrumentation for precise feedback on oxygen and hydrogen levels within the RCS. It has been demonstrated that rather than a 24 hour shutdown window, it is possible to complete this step within a two hour window (four hours being the adopted norm by tracking oxygen and hydrogen real-time within the reactor). This significantly reduces plant shutdown timeframes whilst balancing safety and maximizing operator control of the shutdown process.

The Hach Ultra Orbisphere instrumentation line has been developed over the years with nuclear requirements in mind and all instrumentation is nuclear certified (hence tried and tested in highly radioactive environments).

The most recent breakthrough in oxygen measurement is the Orbisphere G1200 - a luminescent ppb oxygen sensor certified and validated for use within radioactive environments.

Promoting ALARA principles (As Low As Reasonably Achievable) to limit human radiation exposure, the sensor only requires five minutes maintenance every 18 months (maintenance can be co-ordinated with plant outages giving a 100 per cent sensor uptime).

For hydrogen measurement, the patented Orbisphere TC (Thermal Conductivity) sensor was developed to give continuous, real-time ppm or ppb hydrogen readings in a gas or liquid phase with the sensor requiring an annual maintenance.

During a plant shutdown or start-up sequence, a significant margin of error is introduced during time lapses on periodic sampling thus increasing risk.

These unique features of Orbisphere sensors combined with the fact that Orbisphere sensors are designed to last for many years (ie: sensors are not consumables/disposable) reduces any radioactive waste to be handled by plant personnel and reduces disposal costs for the plant.

hen considering operation in nuclear plants, Orbisphere instruments for oxygen and hydrogen measurement have been installed in all operational plants in the USA with 90 per cent of EDF's plants in France and in over 350 plants globally.

And what does reduced outage mean for operators: primarily more time connected to the grid and with that, more generating dollars or generating capacity available.

But how much more can the use of Orbisphere instrumentation for real-time oxygen and hydrogen measurement bring to plant operators?

Using recent figures from the EDF 2008 H1 Financial Report (average realized base-load prices), a 20 hour uptime gain results in $2.5m of generating revenue for every plant shutdown on a typical 1330MW reactor in France.

So considering EDF's generating fleet of 58 reactors, that's a staggering $145m of additional revenues over 18 months through faster plant shutdown during plant outages; or the equivalent of 117MW additional capacity at near zero cost.

Hach Ultra - a wholly owned subsidiary of Danaher Corporation - service offices and authorised distributors operate in more than 80 countries. The company has four research and development centers located in Europe and the United States.

The company's research programmes ensure that customers meet regulations and optimize quality throughout their processes.

Enter 63 or XX at www.engineerlive.com/ipe

Stephen Bell is Market Manager - Power, Hach Ultra - Orbisphere Vésenaz, Switzerland. www.hachultra.com

One of the most costly aspects of decommissioning a nuclear licensed site is the management and interim storage of radioactive waste until ultimate disposal. How best to meet these medium-long term storage requirements (including safety, security, transport and final disposability) within limited budgets is an on-going challenge.

Radioactive waste is required to be stored in passively safe (physically and chemically stable) conditions in transportable and ultimately disposable packages, while ideally minimising the need for control and safety systems, maintenance, monitoring and human intervention. The construction of new waste treatment facilities or shielded stores is costly at a time of restricted budgets and expenditure constraints, and in the on-going drive to find the most cost-efficient and effective means of interim storage (generally assuming a storage period of up to 100 years) for Intermediate Level Waste (ILW), in line with all regulatory guidance, self-shielded packages are now becoming a popular concept.

Self-shielded packages, also known as 'ministores', offer a number of benefits, being suitable for interim storage in an unshielded building allowing man-entry and providing weather-proof cover - requiring considerably less capital expenditure than building and storing waste in conventional remote-handled stores. There may still be a need for some environmental control, but the self-shielded approach certainly simplifies storage requirements and, by avoiding the need to build a shielded store, is said to provide greater flexibility in the decommissioning programme. However, the wide and expanding range of self-shielded options, with widely differing capacities, construction materials and costs, and each with their own advantages and disadvantages, makes selection of the optimum design challenging.[Page Break]

Factors to consider

There are various considerations to take into account. Factors such as assured containment of the waste for the required lifetime, the handlability, transportability, and suitability for ultimate geological disposal (including mass and dimensional limits) are clearly fundamental requirements of any radioactive waste packaging. Added considerations include the amount of size reduction required to package the waste in the containers. Minimising the need for waste size reduction of decommissioning wastes will decrease worker dose exposure and associated risk, so the size of the waste package internal volume and the container lid opening are important.

Whether or not the waste is to be encapsulated is a further consideration which will influence the container selection. A non-encapsulation strategy will be more suitable for some wastes than others, depending on how passively safe the unencapsulated waste is. Solid activated materials which only corrode very slowly (bulk steel or graphite for example) are potentially suitable for non-encapsulation, whereas surface-contaminated or mobile materials such as plutonium-contaminated material or sludges are less so. The ability to store solid unencapsulated ILW without requiring a shielded store is seen as a potential advantage of self-shielded packages, retaining flexibility (with the potential to re-sort, re-pack or encapsulate in future, allowing for changes in storage and disposal options), and saving the immediate cost of an encapsulation plant. On the other hand, encapsulating the waste avoids the need for double handling (reducing worker exposure), provides added shielding, simplifies the transport safety case, can improve or simplify security during storage, and is generally ultimately needed to achieve the passively safe waste package expected to be a requirement for geological disposal. Moreover, in a decommissioning programme encapsulation at a later date may be more complex and costly if much of the infrastructure of the site needed to encapsulate or process the waste has been removed.

Ultimately cost (based on total cost of procurement and storage for 100 years) is a primary consideration in reviewing package options. Minimising cost while ensuring cost-effectiveness and/or value is one of the key challenges in selecting the optimum waste package option.[Page Break]

Package options

Shielded package designs available include 2m or 4m boxes, Ductile Cast Iron Containers (DCIC), Tru-Shield drums, and WAGR boxes, as well as overpacking options such as the ModuCube.

The 2m and 4m boxes (with wasteform volumes of 4.9m3 and 10.9m3 respectively, with 200mm concrete shielding included) are essentially robust freight containers, and can be used for encapsulated or unencapsulated waste. Made of austenitic stainless steel, the cost of both initial procurement and storage needs to be considered (stainless steel being susceptible to localised corrosion so a ventilation system is usually required to maintain a set humidity and minimise chloride contamination). The large opening lid minimises the waste reduction needed to pack these containers, although care must be taken, particularly of the 4m box, with dense metallic waste that the total container mass does not exceed permissible transport weight limits.

The cuboid or cylindrical DCICs, made from ductile cast iron, were developed in Germany as ILW storage, transport and disposal containers. Although relatively high cost to procure (two or three times that of the 2m or 4m boxes) they can be stored without requiring either a shielded building or stringent environmental controls (the lid seal integrity would need to be monitored, but is said to be designed to last at least 40 years), and do not require the waste to be encapsulated. The Type VI DCIC, (commonly referred to as the 'yellow box'), with an approximate 2.9m3 internal volume, is considered particularly suitable for fuel element debris, sludges, resins, sand and gravels. Its considerable weight (18 tonnes empty) again means care is needed to avoid container mass exceeding transport limits. The cylindrical container (approximately 500 litres volume), comes with optional additional lead shielding to store higher dose items and weighs between 5-10 tonnes depending on shielding.

The WAGR box, another alternative, is a reinforced concrete box designed to meet requirements for transport of radioactive materials on public roads and rail. The boxes come in two variants, normal and high density, according to the shielding requirement, with a conditioned waste volume of 5.6m3. With a container mass of 14-20 tonnes, depending on shielding, they are typically not as heavy as the Yellow Boxes, and the lid opening is large, facilitating efficient packing (with care again needed to keep within allowable transport weight limits). The WAGR box is closed by casting a concrete lid which is integral to the strength of the package, so the waste must first be encapsulated. Significant benefits include the low procurement cost (about half that of the 2m and 4m boxes, and around a sixth of the cost of the DCIC boxes), and minimal storage control, essentially needing only a weather-proof building. The box also has a proven track record, having been used for packaging of operational and decommissioning wastes from the WAGR reactor since the late 1990s.[Page Break]

As a further option, an innovative approach by Babcock is driving a development of the Tru-Shield container model to meet UK requirements as a self-shielded waste package for interim storage and disposal. The design is based on the concept of a lead-lined stainless steel drum, with a lead thickness of 50-75mm as required. With a 1.75 tonne container mass, and payload volume up to 305 litres, these containers are relatively small, easily handlable, and potentially suitable for transport on public roads. Waste can be encapsulated or unencapsulated, and the containers would be particularly suitable for specific purposes such as smaller quantities of waste from, for example, a re-processing, plutonium or fuel manufacture plant where fissile content is a concern. The containers could also be used for liquid wastes, with integral mixing paddles. Waste could either be directly loaded into the Tru-shield or into a drum liner if later removal may be required.

Procurement costs are not high, with a cost per m3 of wasteform estimated in the region of just under two thirds that of a DCIC box. These self-shielded containers do not require storage in a shielded building, although some environmental control would be required. A further benefit of Tru-Shield containers is the potential to use waste lead (clean or previously surface contaminated) for the lead shielding, providing recycling opportunities for reducing or eliminating site inventories of lead waste.

A different approach is the ModuCube ministore; an 'overpack' providing a shielded enclosure able to receive four unshielded 500 litre drums or one 3m3 box. This is not designed for use as a transport or final disposal package, its main benefit being to provide re-useable shielding and interim storage of encapsulated waste in pre-existing approved disposal packages. The design is relatively simple and hence cheaper than the DCIC if the DCIC benefits are not required.[Page Break]

To summarise, while the benefits of avoiding the high capital expenditure associated with building and storage within shielded stores are evident, there are arguments for and against each self-shielded package option to be weighed up. Each has its benefits and relative 'best use'. While a single approach may be tempting to enable use of common infrastructure, in reality there will always be a need for a range of designs for different needs. The WAGR concrete box, for example, provides a considerably less costly alternative to the newer steel designs, with benefits such as reduced storage requirements. Unlike their steel counterparts the waste must be encapsulated, but if there is no clear benefit to delaying encapsulation then the WAGR box can provide a good, inexpensive, practical solution. For smaller volumes of waste, especially fissile contaminated materials, the Tru-Shield container not only offers a good solution but also the added advantage of re-using waste lead for shielding. Ultimately, the primary focus should always be on 'fit for purpose', along with maximising cost efficiency.

Val Drake is head of science and technical services, Babcock, London, UK. www.babcock.co.uk/nuclear

The Babcock-Bechtel joint venture Bechtel Babcock Nuclear Solutions (BBNS) has been contracted by Sellafield Ltd to move into phase two of the Pile Fuel Cladding Silo Retrieval Project, Silo Doors & Retrieval Modules (SDRM), having successfully completed phase one.

Retrieval of the fuel cladding and other intermediate level waste (ILW) from the Pile Fuel Cladding Silo is a high priority for Sellafield Ltd – the company responsible for safely delivering decommissioning, reprocessing, and nuclear waste management activities on behalf of the Nuclear Decommissioning Authority.

BBNS was awarded the SDRM contract last year, covering detail design, procurement, manufacture, works testing, delivery to site, installation and commissioning of silo doors and retrieval and waste handling modules, together with a hole cutting system. The three-phase project will take around six years to complete.

Successful delivery of phase one (mobilisation and project familiarisation) ahead of schedule and under budget has now facilitated the move into phase two, involving completion of the design, specifications, procurement packages and safety case support. This phase is expected to take 18 months, and, if successful, will be followed by procurement, manufacture, works testing, construction, installation and commissioning under phase three.

Finalising the complex retrieval design will be a key challenge in this second phase, involving a significant design resource to meet the project’s demanding timescales. Additionally, the BBNS team are accelerating a key design element of the project, the Retrievals Access Penetration, so that the operational requirements of the design can be tested and confirmed as early as possible.  

The BBNS team, which combines the skills and expertise of two nuclear industry leaders, is fully integrated with Sellafield Ltd’s own to deliver this contract, working together to deliver the SDRM project successfully on-schedule, in-budget, and in full compliance with all safety and quality standards.  The BBNS and Sellafield Ltd teams are co-located wherever practicable to further aid effective close working.

For more information, visit   www.babcock.co.uk

Nigel Blackaby discusses how Germany will fare without a new generation of nuclear power plants and the phasing out of the existing fleet, coupled with growing opposition to coal-fired generation, and analyses the steps that Germany will need to take to reach a fully integrated energy future.

In the wake of Fukushima disaster, energy experts now agree that securing Europe's future electricity supply will require an increasing convergence between existing fossil fuel sources and the fast-growing renewable generation sector. Nowhere is this fusing of interests required more than in Germany, in the light of the government's decision to phase out all nuclear power by 2022. The case for integration is now compelling and is something that an increasing number of countries are going to have to consider.

The current debate among those in the power industry is how Germany will fare without a new generation of nuclear power plants and the phasing out of the existing fleet, coupled with growing opposition to coal-fired generation. Many in the industry feel that the technology most likely to benefit in the short term is gas fired generation, but that the recent nuclear-free policy offers Germany a chance to be a pioneer in a new energy system, which matches a substantial green energy sector with a conventional generation base. Chancellor Merkel has already said that her country's 'fundamental' rethink of energy policy could set an example for other countries. If this is to be the case, significant new infrastructure will be required, not only in the area of power generation, but also in the transmission grid and the way that the grid interacts with these power sources.

Germany's offshore wind potential is large but its prime location is a long way from the main load centres. In addition, protest groups are already expressing their fears that the unspoiled, forested centre of the country will become a north-south 'energie autobahn' of pylons and high-voltage cables.[Page Break]

However, renewable energy groups in Germany such as the BDEW Association remain optimistic. They say that Germany is unlikely to experience blackouts in the next decade as the country currently enjoys a surplus energy capacity, has a good potential for energy efficiency savings and has strong border interconnections in place. On the other hand, RWE chief executive Jürgen Grossman has argued that, until low-carbon energy sources improve, Germany will struggle to meet its greenhouse gas reduction targets in the absence of nuclear power. His colleague Volker Beckers, Group CEO of RWE nPower said recently that "Germany has a romantic view of energy policy", and described this policy as misplaced and damaging.

Whatever your position on this issue, it is clear that Germany's power sector will experience a period of change and that traditional power sources will need to be integrated with renewable sources such as wind and solar to create a smart energy solution. The decision on nuclear power may be the catalyst needed to jump-start this revolution.[Page Break]

If the lights are to be kept on at all times, the smart energy system of the future needs to provide the necessary flexibility to allow new low or zero carbon power generation sources to be added to the grid. Technology development is being geared toward providing flexible solutions that enable integration of variable renewables and conventional power and these solutions are now being brought to market. Technologies addressing the challenge of integration include flexible gas turbines, fast-ramping gas and diesel engines, hybrid power plant designs, energy storage, new HVDC designs and smart grid technology.

At a strategic level, Europe's utility companies and equipment suppliers need to communicate and collaborate in order to design the integrated power system of the future. The renewable power generation market now recognises the need for close co-operation and integration with the mainstream as green power becomes big business for the major power generating companies across Europe.[Page Break]

European energy policy is also being driven by a need for further integration between national energy policies, neighbouring grid systems, future R & D efforts and long-term strategy. A pragmatic approach is going to be vital. While a zero-carbon, 100 per cent renewable power grid is the dream for many, for the foreseeable future the power sector in Europe is going to have to work with the sources it has available. The time has come for the all the major actors to join forces in order to deliver a cleaner, reliable and affordable electricity supply for future years.

Nigel Blackaby, Chairman of the Advisory Board, POWER-GEN Europe 2012 This year POWER-GEN is being held at the KolnMesse in Cologne Germany from the 12-14th June 2012. www.powergeneurope.com.

Bo Wier looks at the challenges involved to complete one of the world's deepest nuclear clean-ups, and at some of the innovative approaches being deployed to accelerate the programme whilst minimising cost.

A vertical shaft, excavated in the 1950s for the removal of rock spoil during construction of an undersea tunnel for the Dounreay site's effluent discharge pipes, and authorised in 1958 as the UK's first Intermediate Level Waste (ILW) disposal facility, now represents one of the biggest challenges in the UK's nuclear decommissioning portfolio.

This major project, to decommission the shaft (and wet silo also used for ILW storage) including recovery and packaging of over 1500 tonnes of radioactive waste, is now the focus of 'renewed emphasis' for the new Babcock Dounreay Partnership management team at Dounreay. The team, which is responsible for the decommissioning, demolition and clean-up of the Dounreay nuclear site (the first major closure project in the UK), having taken over in April this year, is taking the decommissioning programme at Dounreay to its interim end state, and has committed to accelerate the programme (by up to 16 years over previous estimates of two years ago) and reduce project costs by well in excess of a billion pounds. The shaft and silo project is one of the key projects being accelerated within this programme.[Page Break]

Current status

Waste disposal in the shaft (measuring up to 4.6m across and 65.4m deep) ceased following a chemical explosion in 1977, thought to have resulted from an accumulation of hydrogen. By this time most of the waste was being consigned to a nearby wet silo (a concrete lined and roofed box built just beneath the surface with an approximate storage capacity of 720m3), which was used until 1998 as a storage facility for the site's ILW.

ILW consigned to the shaft and silo now comprises items of solid waste plus sludge from the pond clean-up and decomposition of some of the solid waste, and covers a broad chemical and radiological spectrum. A decision was taken in the 1990s, as a result of advances in technology, to empty the shaft and silo, and a major programme is now underway to decommission them.

The first step (completed in 2008) was to isolate the shaft to reduce the ingress of ground water, minimising potential contamination. Up to 400 boreholes were drilled around the shaft in a boot shape (to a depth of 80m around the vertical shaft and nearly 20m long side tunnel - the former liquid effluent discharge tunnel). A fine grout was injected at high pressure into the boreholes, to form a barrier and create a giant containment around the shaft and side tunnel, considerably reducing the amount of water getting into the shaft.

The next stage is the highly challenging removal, treatment and storage of the waste, estimated to total approximately 1220m3 of mixed solid and liquid ILW. Waste is to be recovered from both the shaft and silo and processed for long-term interim storage within shielded containers on site.[Page Break]

Innovative approach

Concept designs are being developed for waste retrieval, treatment and storage facilities, evaluating the techniques that can be utilised and the equipment needed, and a number of innovative approaches have been introduced by the new management team at Dounreay, helping to accelerate the project while minimising cost.

Two independent retrieval facilities are to be developed for the shaft and silo, each having its own waste processing capability to minimise the potential for processing pinch points. Novel features include the use of limited life construction in preference to heavily engineered long-term structures, being less costly to build and decommission, and the use of modularised plant and equipment systems, for ease of commissioning and enabling critical items of plant to be more easily substituted in the event of a failure, allowing work to continue. Additionally, the use of self-shielded waste containers for on-site storage also helps to optimise cost-efficiency by avoiding the need for high capital investment to construct shielded waste stores with remote handling.

A key feature of the team's approach is the use of proven, commercially available off-the-shelf (COTS) equipment wherever possible, rather than designing and developing bespoke systems (at, inevitably, higher cost and greater risk), and adopting methods and techniques used in the nuclear and other sectors such as water treatment and mining industries. This approach is being applied to multiple aspects of the project, from shredders, remote vehicles, remotely operated equipment, and cranes, to waste treatment, waste containers, and assay and monitoring systems.[Page Break]

Major challenges

Work on the shaft will commence with construction of the waste recovery headworks, with a combination of industrial grabs and robotic mechanisms that can be lowered into the shaft to recover the waste. The challenges faced are considerable. High radiation levels preventing man access for routine and remediation operations, and the difficulties of retrieval from a vertical shaft down to a depth of 65m are two examples, as is the need to deploy equipment almost 20m into the side tunnel.

The technical issues are also significant. For example, as the retrieval depth increases and the water level within the shaft is progressively lowered, the differential pressure between the water table and shaft water level will increase, causing an increased inflow into the shaft, in turn placing a greater burden on the downstream liquid effluent treatment plant.

Further, managing the retrieval of the waste matrix and ensuring that the grab does not snag on the waste is difficult to achieve remotely. This is in addition to the challenges associated with the supply of hydraulic and electrical power, as well as lighting, camera systems and monitoring equipment, which become greater as the retrieval point gets deeper. The equipment must also be radiation tolerant to withstand the radiation fields encountered.

Deployment of a remotely operated vehicle (ROV) from a platform into and along the side tunnel, along with all the ancillary power and control systems required, and the retrieval of waste back to the shaft, will inevitably be a complex and time-consuming procedure. Additionally, the recovery of sludge and free liquid from a depth of up to 65m is a further challenge, requiring specialist suction or jetting systems to overcome the height over which the active waste will have to be transported.

The physical location of the facilities brings its own additional challenges. A reinforced concrete working platform has been built that will provide protection from the encroachment of the sea, as well as providing a secure base on which to mount the retrieval structure, plant and processing equipment. The selection and design of the overbuilding will take into consideration the location and harsh weather conditions that prevail at the Dounreay site.[Page Break]

Retrieval methodology

In line with programme policy, a limited-life structure will be erected, incorporating shielded areas for waste retrieval, waste processing and packaging, waste characterisation, and sludge conditioning. This will include an industrial crane, a modularised ventilation extraction system with HEPA (High Efficiency Particulate Air), and modularised processing plant and equipment. Wherever possible COTS equipment previously successfully deployed within a nuclear decommissioning process or harsh industrial environment will be specified. The high ambient dose conditions will require these systems to be remotely controlled and specified to withstand prolonged exposure within high radiation fields. Plant and equipment will be modularised enabling the systems to be manufactured and tested off-site, thereby minimising on-site installation and commissioning timescales and, later, decommissioning time.

Petal and clam shell grabs will be deployed to retrieve waste from the full depth of the shaft, with the crane having X-Y traverse capability to ensure complete coverage of the cross section of the shaft. The crane will also be specified to ensure that it can retrieve any weight of waste likely to be encountered. An ROV will be transported down the shaft from a deployment platform, with the ability to remove any obstructions on the side walls and recover waste from the side tunnel into the shaft, for retrieval back to the headworks using the crane.

Waste retrieved from the shaft will then be segregated, characterised, and processed for interim storage. The waste will be sorted using ROVs with power manipulators and various end effectors for sizing and handling waste items, and segregated into solid and effluent waste streams, using equipment including a shredder and size-reducing tooling to shred and screen the debris and cut large items. Product trials of the processed waste will be conducted to ensure that the wasteform meets regulatory requirements. All wastes retrieved will be conditioned and encapsulated or immobilised within self-shielded containers using a cementitious matrix, and the containers transported for intermediate storage on-site in full compliance with regulatory requirements.

Recovery and processing of waste from the silo will follow a similar procedure, with variations to meet the silo-specific requirements (for example, there will be no requirement to deploy a platform-mounted ROV into the silo but removal of the roof slab will be required to improve access to retrieve the waste). Waste from the silo will also be characterised and encapsulated.

The retrieval of radioactive waste and sludges from a narrow vertical shaft and from the silo represents one of the biggest projects in the Dounreay decommissioning and clean-up programme, involving numerous unique and significant challenges. Key milestones include achievement of concept design at the end of this year, completion of detail design in autumn 2013 and initial operations in mid-2015, with a view to ultimate completion of retrieval actions for this project, one of the UK's most significant nuclear decommissioning and engineering challenges, by the end of 2020.

Bo Weir is Babcock Dounreay Partnership's Shaft & Silo Project Director, Dounreay, Caithness, Scotland. www.dounreay.com

Dealing with the coolant when decommissioning liquid metal cooled reactors, is a demanding and hazardous challenge. Jason Casper looks at how this may be addressed to complete the timely decommissioning of the UK's Dounreay reactors.
 
Standfirst: Last year saw the disposal of 57 tonnes of alkali liquid metal successfully completed at Dounreay, representing the destruction of one of the most hazardous legacies of Britain’s earliest atomic research. Now, parent body organisation Babcock Dounreay Partnership (responsible, for the decommissioning, demolition and clean-up of the Dounreay nuclear site), working with the Dounreay Site Restoration Limited team, face a further, significant challenge; to tackle the destruction of the hazardous alkali metal remnants inside the reactors vessel, which could not be extracted for disposal in the purpose-built chemical processing plant.
 
To address the challenges, the project will apply innovative approaches, while drawing on proven techniques and experience, and lessons learned, from other sites worldwide. Equally, the approach taken and knowledge gained from the Dounreay programme will be able to contribute valuable experience and expertise to future alkali metal breeder reactor decommissioning.

Potential hazards

Dealing with the nature of the coolant – commonly sodium or the sodium-potassium alloy NaK – is a major consideration in decommissioning liquid metal cooled reactors. Sodium metal reacts vigorously when exposed to water, releasing hydrogen and large quantities of heat – thereby providing not only an explosive gas mixture but also a source of ignition.  The products of combustion are also toxic, and can cause severe caustic and thermal burns on coming into contact with skin, as well as being hazardous to ingest or inhale. Methods of destruction or disposal can range from a purpose-built sodium disposal plant (which essentially treats and neutralises the sodium to produce salt water) to high temperature incineration, among others.
 
The challenges involved in treating the sodium or NaK in such decommissioning programmes are considerable and will be encountered at various stages. At the defuelling phase, for example, the assembly will be covered by a residual film of sodium that has to be removed before storing the elements in the pond. Every component extracted from the reactor will also be covered by a film of sodium, and can sometimes retain larger amounts of sodium, which is best removed before dismantling the components.  Additionally, the metallic coolant from the primary and secondary circuits has to be chemically treated to transform what could be several tonnes or several hundred tonnes of metallic radioactive product into a stable form, while the primary and secondary vessels (when drained of the primary and secondary coolants) will have some residual liquid metal stuck to the surface or retained inside the structures as non-drainable retentions. Several secondary wastes may also contain sodium, such as cold traps (which clean the alkali metal coolant of impurities) or caesium traps. [Page Break]
 
First stage success
 
At Dounreay the two reactors are both the fast breeder type using alkali metal coolant; the Dounreay Fast Reactor (DFR) using approximately 130 tonnes of NaK, while the larger Prototype Fast Reactor (PFR) used around 900 tonnes of sodium. The first stage in dealing with these was to remove the hazardous inventory of radioactive contaminated alkali metal in a safe, environmentally responsible and cost-effective manner, leaving the reactor primary circuits and vessels in a safe state ready for the next phase.
 
The PFR was the first to be addressed (sodium being slightly easier to work with than NaK). A dedicated sodium disposal plant (SDP) was constructed in the former PFR reactor turbine hall, and operated from 2004 to 2008 to process over 1500 tonnes of sodium metal and a small quantity of NaK from the PFR. The SDP reacts small quantities of sodium with large quantities of aqueous sodium hydroxide which, following neutralisation with hydrochloric acid, produces salt water. The salt water passes through an ion exchange process to remove caesium radionuclides before it is discharged to sea, in accordance with the site’s waste disposal authorisation.  
 
To treat the NaK coolant from the DFR, a dedicated NaK disposal plant was constructed in the DFR sphere. This began operating in 2008 and completed its role to destroy 57 tonnes of primary (radioactive) NaK in April 2012.  An estimated 1000 trillion becquerels of caesium-137 was removed from the coolant during the chemical process, which again turned the liquid metal into 20,000 tonnes of salty water.  Liquid metal was lifted in small batches, the alkalinity neutralised with acid, and the caesium extracted via ion exchange. (Designers thought the plant would decontaminate the effluent by a factor of 1000, but decontamination rates of up to 4 million were achieved during the operation, reducing levels of radioactivity in the effluent to below the limit of detection).  The resin columns used to trap the caesium will now be cemented up and managed as higher-activity waste.
 
The challenge ahead
 
With the bulk volumes of sodium and NaK now removed from the reactors and dealt with safely, in a readily controlled manner, attention now turns to the remaining element. It is estimated that around 3.5 tonnes of residual NaK remains inside the pipes and vessel of the DFR, with a further 9 tonnes of sodium still estimated to be in the PFR reactor vessel, which needs to be cleansed and/or destroyed. In both cases this is extremely difficult to access, and the destruction therefore more complex than the sodium and NaK destruction projects to date.  
 
The project to deal with this residual sodium/NaK presents numerous challenges. Those associated with dealing with alkali metals include the potential for violent reaction, particularly in high humidity, and hydrogen production with its potential for ignition if oxygen is present (which is avoided with the use of inert purge gases), in addition to radiological challenges associated with the high dose involved (up to 400 sieverts in the PFR core, and around 240 in the DFR).
 
Among the variety of techniques that could be used to address these issues, with varying degrees of success and risk, a proven innovative approach is being taken to treat as much of the sodium and NaK as possible in-situ.  This minimises the hazards and risks associated with cutting into the reactors to remove the affected components and, importantly, although not used before in the UK has been proven at other sites around the world, in projects such as the Experimental Breeder Reactor II in Idaho, USA, of which the team has direct experience and knowledge of the processes and the risks and safety issues to be considered.
 
Detailed development of the project methodology is now underway and will involve a number of techniques.  The first is to inject superheated steam (which is above water’s boiling point to avoid any condensation) into an inert gas system at 340°C that contains alkali metals. The alkali metal is converted into hydroxides and at these temperatures the hydroxide remains molten and sinks through the molten sodium, always leaving a fresh layer of sodium to react. Once the alkali metal has been converted to hydroxide the system is flushed with an acid solution to remove any residual salts.  This approach has been tried and tested a number of times for single or groups of components, and has proven to be very controllable and safe.  Application on a larger scale, however, can be more complicated, due to the difficulty of getting the entire system up to the high temperature required.  
 
An approach that does not require the very high temperatures is to use low concentration wet vapour nitrogen, which again reacts with the sodium in a series of ‘bubble and pops’ to prevent the build up of significant sodium hydroxide layers.  Any hydroxides and salts are then flushed out of the system. In this case the complexities include getting exactly the right balance to control the process, without allowing a sufficient build-up of hydroxide crust (which builds on the sodium at lower temperatures) to cause shutdown of the reaction, or potential break-through of the hydroxide layer resulting in violent sodium and water reactions.[Page Break]
 
A third approach, which has been proven in the decommissioning of the Idaho Experimental Breeder Reactor II, is to use water jets to spray a low volume acidified liquid solution directly into the reactor on sodium layers, resulting in small controllable excursions and removal of the hydroxide layers. The acid promotes the reaction and reacts with the hydroxide preventing the crusting. Once the sodium has reacted, the vessel is then filled with liquid and flushed. This has been shown to be extremely effective, although it again involves challenges, in particular the need for careful control of liquid dosing and monitoring to avoid large violent reactions.
 
The approach for the Dounreay reactors is likely to involve elements of all three of these methods. Additionally, it is likely that some portion of the alkali metal will be extracted and then treated in specific pressure vessels (using either the superheated steam or wet vapour nitrogen technique), given that a suitable and safe removal method can be identified. While this approach does have a precedent (for example smaller liquid metal reactors in Germany have been entirely dismantled and treated externally), the process has been found to be laborious, time-consuming and carry greater risk compared to the in-situ methods, so will only be used at Dounreay to a limited extent.
 
The optioneering phase to identify the exact methodology to be implemented for the PFR was completed in 2012, with designs sufficiently complete to enable skid systems for the selected treatment to be ordered. These will be installed in 2014 for treatment of the PFR to begin in 2016.   
 
For the DFR there is a requirement to remove 1000 or so breeder elements from the vessel, a number of which are swollen, split or stuck, before commencing treatment. Some of these will need to be cut out of the reactor grid using tools on a deployment arm while others can simply be pulled out, and if many are stuck a contingency measure will be to deploy a further long arm manipulator. The items will then be removed through an inert flask and then through an inert cell where they will be washed to remove the NaK, before being packed in a flask for shipment. Meanwhile, the optioneering phase for the residual Nak removal will be completed over the next two years, including characterisation and system design, with system installation scheduled for 2016 (subject to removal of the fuel) and the NaK treatment to start in 2017. The treatment of both the PFR and DFR will be followed by reactor and vessel sizing and ultimately building demolition in 2022 and 2023.
 
In short, the next phase of the metal reactor decommissioning at Dounreay is complex, but it is achievable, and while the proposed approach is innovative, the methods have been proven to be safe and successful at other sites internationally. The experience of the Dounreay team brings world class expertise together to address the challenge. Moreover, as two significant liquid metal fast breeder reactors, the experience at Dounreay will also be invaluable as a contribution of highly specialist expertise, technique development and demonstrable experience, to other metal reactor decommissioning and sodium or NaK disposal projects around the world.

Jason Casper is Reactors Project Director at Dounreay,  Caithness, Scotland.  www.dounreay.com

Two leading organisations for the nuclear industry in the UK, the National Skills Academy for Nuclear and the National Nuclear Laboratory have committed to working collaboratively on the development of high level skills to support future R&D capability for the sector.

The relationship has been cemented by the signing of a Memorandum of Understanding (MoU) which formally marks the collaboration to ensure a streamlined and collaborative approach to ’Subject Matter Expert’ development, providing maximum impact and value for the industry between the organisations.

The Nuclear Energy R&D Roadmap: Future Pathways report produced by Government described the availability of skilled R&D personnel and Subject Matter Experts as a critical issue. It is critical not only for the experience required to build robust safety cases for nuclear operating plant, but also to provide the leadership and expertise necessary to implement the longer-term R&D that is in turn needed to inform future nuclear pathways and to provide strategic advice on emerging nuclear issues.

The National Nuclear Laboratory has a specific remit from the Department of Energy and Climate Change to maintain and develop key skills and capabilities in the nuclear R&D sector and is currently operating a small Subject Matter Expert development model with Sellafield Limited.  The National Skills Academy for Nuclear is the lead strategic skills body for the nuclear industry and as such will aid in the standardisation of such activity building it into a formal programme for use across the UK.

Alongside industrial expertise, experience and development, the development of Subject Matter Experts also requires post-doctoral study with HE institutions like The University of Manchester and its Dalton Nuclear Institute. This helps provide a background which bridges academia, National Laboratories and industry. Having contributed to recommendations on Subject Matter Experts and high level skills development Dalton Nuclear Institute is committed to providing continuing support and works alongside NNL and NSA Nuclear on this agenda.

Dr Fiona Rayment, Fuel Cycle Solutions Director at NNL, said: “Among the many thousands of skilled people playing vital roles in our industry, I'd say there are 100 or more "Subject Matter Experts" who each possess virtually irreplaceable levels of knowledge in their specialist fields, often accumulated over decades. These people are the "gurus" of their particular technical areas and it is vital that we develop tailored programmes to help them to transfer their skill and insight to the next generation. I'm delighted that NNL will be leading this activity, working closely with the National Skills Academy for Nuclear."

Jean Llewellyn OBE, CEO National Skills Academy for Nuclear, added: “It is well reported that one of the major skills issues facing the nuclear industry in the UK is the ageing workforce, with over half of the workforce expected to retire in the next ten years. With Subject Matter Experts requiring 10 to 15 years train it is vital that a strategic approach commences with urgency.  This is an urgent skills area for action and is intrinsic to the success of the future nuclear programme in the UK.   To effectively address this area, a collaboration between NSA Nuclear, NNL, industry and academia is required.”

Professor Andrew Sherry FREng, Director of The University of Manchester’s Dalton Nuclear Institute, said: "The nuclear skills challenge is a major factor in the UK maximising its contribution to the domestic nuclear programme as well as enhancing international export and inward investment.  The role of NNL and NSA Nuclear in addressing this challenge for higher level nuclear skills is critically important, and we look forward to working together with other academic institutions on this important agenda."

For more information, visit www.nuclear.nsacademy.co.uk

Specially designed for pumping large quantities of critical cooling water within fossil and nuclear power generation applications, the CUP-CVP, concrete volute pump, from ClydeUnion Pumps, an SPX Brand, offers exceptional performance and efficiency, whilst providing extremely high plant availability.

Power used in the generation of electricity reduces the overall power plant efficiency. Reducing the power consumed for major applications such as cooling water pumps therefore offers significant sustained increases in plant efficiency and profitability.  Availability of the cooling water pump is also critical to plant running times and production capacity.

The CUP-CVP pump is designed to provide higher flow rates than conventional vertical bowl pump designs, thus reducing the number of pumps required. The CUP-CVP design operates at higher efficiencies and experiences minimal wear during operation due to its low running speed, resulting in exceptionally high reliability and availability approaching 100 per cent.

The pump has been shown to exhibit no noticeable deterioration in efficiency over 100,000 hours of operation in power generation applications, with a minimum service life of 10 to 12 years between internal maintenance inspections. Compared with metallic pumps, this long-term efficiency saves kilowatts and provides prolonged, maintained power plant performance.

Furthermore, the specific SPX design of the volute ensures the concrete is in compression which improves sealing. This design also enables a single concrete pour to produce the casing, which minimises any air entrainment and further reduces the risk of leakages. The single pour also makes installation easier and more economical.

As the pump casing is predominantly produced in concrete this eliminates potential corrosion problems often experienced with suspended bowl pumps (especially in hot sea water). The lower specific speed of concrete volute pumps results in a slower running speed and shorter submerged setting depth which significantly reduce the depth of civil dig and overall land area excavation required for the intake and pump house structures.

The CUP-CVP can be provided for flow rates up to 120,000 m3/hr and delivery heads up to 50m. It is engineered for hydraulic efficiency and its non-corrosive ‘cast-in’ casing is manufactured to suit the onsite civil construction programme.

Once installed, the design incorporates a packed gland with a pneumatically operated inflatable seal (to prevent flooding when the packing is replaced) and a removable inner cartridge for ease of maintenance. Journal bearings are oil bath lubricated and tilting pad thrust bearings are used to improve reliability and increase bearing life. An efficient, balanced impeller reduces thrust loads and increases stability.

The large flow rate of a single concrete volute pump will achieve a duty equivalent to several vertical bowl type pumps, reducing the number of pumps required on site, and with typically two points higher efficiency than alternate technologies, it offers long term power savings.

SPX and ClydeUnion Pumps have proven experience in providing these exceptionally reliable and efficient pumps which are ideal for pumping large volumes of cooling water. The special shape of the volute and single concrete pour ensure maximum robustness to protect metallic innards from damage and further makes these units easier to install than equivalent multi-pour designs. The pump design and low speed operation also ensures very low wear, minimum maintenance and high reliability in order to maximise power generation over long periods. The high reliability of the CUP-CVP also eliminates the need for a standby unit.

Overall, the CUP-CVP offers long term power savings through higher, maintained efficiency over many years of service and is supported by the impressive global engineering and service provided by SPX.

For more information, visit www.spx.com

Imtech UK’s Capula business division has won two contracts with Shepherd Engineering Services (SES) for work at the Drax Power Station in North Yorkshire.

As part of the first contract, Capula, which specialises in advanced automation and real-time business intelligence, will design, manufacture, configure, supply and commission the Schneider-based control system for the new biomass storage facility.

The second contract will involve Capula also providing a Schneider-based control solution for the boiler distribution system, which consists of two sections – the Common Systems and Unitised Systems. The Common Systems will deal with the reception of fuel from storage, while the Unitised Systems will control the eventual transport of the fuel to the boilers of the three converted generating units.

New receipt, storage and distribution systems are being constructed at Drax Power Station. This development is part of its transformation into a predominantly biomass-fuelled generator through the burning of sustainable biomass in place of coal.

Phil Willett, Capula’s Business Sector Head for Power & Renewables, said: “The solutions Capula is implementing will integrate existing systems with the new control systems.”

For more information, visit www.imtech.eu/uk

Systems integration specialist Hima-Sella is to develop and provide a two-tier, fail-safe Instrument Protection System (IPS), for use in the nuclear industry, with the primary level of protection implemented using HIMA’s Planar4 solid-state logic solver. Earlier this year, and under the rigorous EMPHASIS assessment methodology, the modules of the Planar4 logic solver secured approval for use in safety systems in the nuclear industry.

The secondary level of protection within the IPS will be implemented using plug-in relay logic. Also, and in accordance with IEC 61508, the solutions for the two IPS levels will be developed by two independent engineering teams, using separate production facilities, within Hima-Sella.

Through interfacing with temperature, pressure and other sensors, as well as valve actuators and pumps, the two-tier IPS will be able to perform automatic emergency shut downs as well as respond to manual trips. The IPS project also includes the provision of a number of HMI matrix panels, to enable operators to view and respond to process and alarm conditions.
 
For more information, visit www.hima-sella.co.uk

The Windscale chimneys have been a major part of the UK's Sellafield skyline since the 1940s and work on decommissioning the last remaining chimney is now progressing in earnest.

The chimney has been opened up for the very first time in over 17 years, which is a tangible sign that real decommissioning progress is being made. The filter dismantling access gantry, which is made up of 52 tonnes of structural steel work, was pulled apart to open the chimney to the elements in preparation for dismantling.

Jeremy Hunt, Head of Decommissioning Projects said: “The decommissioning challenges posed by the pile chimney are unique and no other structure in the world provides the same complexity in terms of both radiological and conventional decommissioning constraints. Bringing the chimney down will be a real visual demonstration of our commitment to cleaning up Sellafield.”

The original two pile chimneys were built at Windscale between 1947 and 1950. They were actually ventilation shafts, rather than chimneys, and discharged cooling air from the Windscale Pile Reactors. The Piles were conceived in the aftermath of the war, as part of the drive to develop a nuclear deterrent. Their primary purpose was to provide nuclear materials and the heat generated was released to atmosphere rather than harnessed to generate electricity.

The remaining pile chimney worked as a ventilation shaft for Windscale Pile One which caught fire in 1957 and the filters fitted at the top of the chimney prevented much of the contamination escaping to the local area. The decision was then taken to shut down both Windscale Piles.

Nobel prize-winning physicist John Cockcroft famously insisted that the Windscale Pile chimneys be fitted, at great expense, with high performance filters. Since this was decided after the stacks had been designed and partially built, they produced iconic bulges at the top of the structures - known as the Cockcroft’s Follies – which prevented the Windscale Fire disaster from becoming a catastrophe.

Steve Slater, Head of Decommissioning said: “Over 50 year after the Windscale Pile reactors ceased operation, the familiar landmarks of the West Cumbrian skyline are disappearing. The chimneys were a real technical achievement in terms of construction, which minimised the effect of the fire in 1957 and are testament to the nuclear pioneers who built them.

“Today, we’re using the considerable nuclear expertise built up at Sellafield to safely bring the final chimney down. The plan is to remove the filter gallery by the end of next year and then the chimney diffuser by 2018 to meet the requirements of our customer the Nuclear Decommissioning Authority. A tower crane will be built alongside the chimney and the chimney barrel itself will then be dismantled and lowered down in sections.”

Work is now underway for the major demolition of the filter gallery structure. Some 66 tonnes of brickwork have been removed from the filter gallery external walls and all of this has been transferred from the top of the chimney in a small goods hoist which runs up and down the outside of the chimney.

Chris Wilson, Pile Chimney Demolition Manager: “It’s taken many years of real effort and energy to develop a robust, safe and effective plan for the chimney demolition. For the first time in decades, we are able to confidently progress the safe dismantling and demolition of this historic and iconic UK nuclear legacy.

“There have been many significant challenges to overcome in preparing for the physical demolition of the chimney, not least coming up with an agreed plan with the neighbouring nuclear plants on the congested Sellafield site. We are also working hard to put in place a sizable workforce with the right skills to carry out the job.”

The chimney is 110 metres tall and there is approximately 500 tonnes of structural materials including steel work, bricks and masonry in the filter gallery section of the chimney, with over 5000 tonnes of materials in total to be removed during full demolition of the chimney to ground level.

The two chimneys were identical in structure comprising a 14 metre diameter reinforced concrete structure.

They consisted of seven major sections: foundations; main shaft; diffuser; filter section with plant rooms; concentrator section; upper section and access shaft.

Following the fire, the chimneys were sealed at the top, the contaminated filters removed and air inlet ducts isolated. Radiation levels had to reduce significantly before decommissioning work could start. The first chimney was reduced to the level of the adjacent reactor building in 2001, however the second chimney posed more of a challenge due to radioactive contamination from the fire.

Decommissioning progress on the remaining chimney has also involved: stripping out the thermal insulation lining; taking down the concentrator; dismantling the filter in-fills; removing the four 10 tonne winches that were used to raise and lower the head gear platform inside the chimney on which a remotely operated demolition vehicle was deployed to remove the chimney lining and steel work.

A combination of manual and semi remote tools and techniques will be used to provide the safest demolition approach. This will include concrete and steel cutting techniques, lifting capability through cranes and standard lifting apparatus, climbing platforms commonly used to access chimney stacks.
Sellafield Ltd.

For more information, visit www.sellafieldsites.com

Oerlikon Leybold Vacuum has received a double-digit million Euro order for vacuum technology from a global manufacturer of uranium centrifuges for nuclear power facilities.

Oerlikon Leybold’s vacuum solutions will play a key role in a nuclear plant presently under construction in the United States. Oerlikon Leybold Vacuum will deliver vacuum equipment for 12 different systems and will offer customised service to fit the customer’s needs, including assembly, testing and documentation in accordance with requested standards.

The RUVAC roots pumps have been modified to withstand prevailing conditions and comply with the high requirements of their application.

Uranium centrifuge technology is used not only in modern energy solutions and civil power generation, but for medical and industrial purposes as well. U-235 is the uranium isotope used in nuclear fission.

Nuclear reactors require a 4-5 per cent U-235 content for safe and efficient operation, but natural uranium ore only has a 0.7 per cent U-235 content ratio.

The uranium for use in reactors must therefore be mined, milled and converted to the appropriate gaseous chemical form, which allows those molecules with higher amounts of U-235 to be selected out. This process is known as uranium enrichment, and it requires the use of special centrifuges. The process involves forcing pressurised uranium hexafluoride gas through a series of porous membranes or diaphragms. As U-235 molecules are lighter than U-238 molecules (a similar isotope that exists alongside U-235), they move faster and have a slightly better chance of passing through the pores in the membrane.

The UF6 that diffuses through the membrane has higher levels of U-235, while the gas that did not pass through has depleted levels of U-235. This process is repeated over and over in a series of diffusion stages called a cascade. Each stage involves a compressor, a diffuser and a heat exchanger to remove the heat of compression.

Finally, the enriched UF6 product is withdrawn from one end of the cascade and the depleted UF6 is removed at the other end. The gas must be processed through some 1,400 stages to obtain a product with a concentration of 3 per cent to 4 per cent U-235. The plants typically achieve only modest levels of isotope separation in each individual stage of enrichment; they compensate for this by having the capacity to handle large volumes of gas. The process requires a robust, stable vacuum.

For more information, visit www.oerlikon.com/leyboldvacuum

Generation III power technology and advances in small modular reactors are driving developments in the nuclear power generation market. Sean Ottewell reports.

Rolls-Royce is to collaborate with Rosatom and Finnish nuclear utility company Fortum on an initial project to assess the feasibility of introducing Russian Generation III+ VVER nuclear reactor technology to the UK new build market. The UK government and Rosatom signed a memorandum of understanding (MoU) to facilitate this commercial work in September.

Rolls-Royce and Rosatom have been working closely together since 2011. This latest contract will see Rolls-Royce undertake engineering and safety assessment work for Rosatom ahead of its Generation III+ VVER reactor technology potentially entering the first step of the UK's formal regulatory approval process which is called generic design assessment.

Rolls-Royce is also supporting US-based NuScale Power in its submission to the US Department of Energy's (US DOE) funding opportunity announcement to bring scalable, small modular reactor (SMR) technology to market by 2025.

The development of clean and affordable nuclear power options is a key element of the DOE nuclear energy R&D roadmap. High priority is placed upon accelerating timelines for the commercialisation and deployment of SMR technologies through its SMR licensing technical support programme.

The latest US DOE funding opportunity announcement is focused on optimising SMR efficiency, operations and designs through innovative and effective solutions for enhanced safety, operations and performance. The US DOE aims to solicit proposals for cost-shared SMR projects that have the potential to be licensed by the Nuclear Regulatory Commission (NRC) and achieve commercial operation around 2025.

NuScale Power has developed novel and proprietary breakthrough technology for an innovative, simple, safe, economic, and scalable SMR. Using proven light water reactor technology, the NuScale Power Module is cooled by natural circulation, is entirely self-contained and is installed underwater and underground to maximise safety.

Generator packages to China

Alstom has signed a co-operation agreement with China's Dongfang Electric Corporation (DEC) for the supply of turbine and generator packages for future Chinese AP 1000 projects.

This agreement has a strategic importance for both Alstom and DEC as China resumes building nuclear power plants and moves towards Generation III nuclear power technology. It is also in line with the Chinese government's commitment to steady growth in the sector under the current five year plan, with a top level of safety which fully meets the standards of the International Atomic Energy Agency (IAEA).

According to the agreement, DEC's turbine and generator packages related to future AP 1000 projects will be based on Alstom's Arabelle technology. The Arabelle steam turbine is suitable for all types of nuclear reactors including AP 1000 and is renowned globally for providing higher efficiency and reduced installation and maintenance costs. AP 1000 belongs to the Generation III pressurised water reactor (PWR) and has been identified as one of the major standards for China's future nuclear development.

This agreement also marks the first introduction of the long last-stage blade Arabelle LP69 module in China. This proven technology will provide a significant advantage to the customers in the Chinese market, says Alstom. The first contract under this agreement is expected to be signed shortly.

In terms of the China's current nuclear activities, Ningde 1, the first of four home-designed CPR-1000 PWRs being built at a site in Fujian Province, began commercial operation this April after a 58-month construction period. The 1080 MWe unit was connected to the grid in late December last year and underwent a 168 hour trial operation before it began commercial operation.

In other news, Turkey has chosen Japan as its partner to develop the Sinop nuclear power project in the Black Sea province which would see the installation of four units of ATMEA1 Generation III reactors.

Having got governmental agreement, an international consortium of Japan's Mitsubishi Heavy Industries (MHI), Itochu Corporation, French utility group GDF Suez and the Turkish Electricity Generation Company Incorporated (EUAS) will now undertake further development and negotiation towards the contract to build and operate the 4400 MWe nuclear plant. Commercial operation of the first nuclear unit is targeted at 2023.

Enriched uranium

The research, development and demonstration (RD&D) programme to advance USEC's American Centrifuge - America's next generation of uranium enrichment technology - continues to make solid progress in achieving its milestones.

Five of the programme's nine milestones have been completed and certified by the US DOE. USEC successfully completed the sixth milestone to test the effects of a power loss to the uranium centrifuge machines earlier in the summer, and DOE certification of that milestone is pending. The three remaining milestones are scheduled for completion by the end of the programme in December.

Over the course of this summer, the integrated systems testing programme was completed for the 120-centrifuge commercial cascade, which would be duplicated 96 times in a proposed commercial plant. All of the commercial-grade centrifuges are now spinning individually at target speed, and the process of conditioning the centrifuges and related piping on uranium hexafluoride gas is underway. USEC expects to operate the centrifuges as an interconnected cascade later in the year (Fig. 1).

Beyond proving the reliability and readiness of the American Centrifuge technology, the RD&D programme will ensure that the USA has its own indigenous uranium enrichment technology to meet national security needs. With the recent cessation of enrichment at the gaseous diffusion enrichment facility in Paducah, Kentucky, the country for the first time in more than 60 years is without its own technology in operation to enrich uranium.

Entergy go-ahead to continue operations at Indian Point

Entergy has received US Nuclear Regulatory Commission's (NRC) formal notice that, while the licence renewal process is ongoing, it can continue operating Indian Point unit 2 under its existing NRC licence.

Since purchasing the plants, the company has invested more than US$1 billion (EUR752 million) upgrading and enhancing the facility and preparing it for continued safe operation during the 20-year period of a renewed operating licence.

Through the period of extended operations, Entergy will be operating unit 2 in accordance with NRC requirements and commitments made in the license renewal proceedings, a process initiated by the company in April 2007 when it filed its application for license renewal. As it always does, the NRC will provide continuous oversight through this period, and has performed many thousands of hours of inspections and reviews beforehand specifically to ensure appropriate safety preparations were made for this period.

NRC staff had previously recommended that the licences for the two operating units at Indian Point be renewed for an additional 20 years of operation, noting the plants can be operated safely and that there are no environmental impacts that would preclude licence renewal.

Additionally, while not part of the license renewal review process, Indian Point's security programme is regularly inspected by the NRC through established oversight programmes. Entergy has invested more than US$100 million (EUR75 million) at the site since 9/11 to strengthen security, and its security programme meets all NRC performance review and inspection criteria.

Resolve Optics Ltd has supplied a number of non-browning zoom lens to Custom Cameras Ltd (Wells, UK) to enable the company to supply fully integrated radiation tolerant camera systems for monitoring applications in the nuclear industry.

In highly radioactive environments where camera servicing or replacement is not an option - Custom Cameras sought a proven supplier of high performance, radiation tolerant zoom lenses.  

Tony Moon, Sales Director of Custom Cameras, commented: “Over the last 10 years we have purchased non-browning 3x and 6x zoom lens from Resolve Optics enabling us to provide optimised remote camera systems for applications including inspection of nuclear fuels rods for oxidation, deterioration or damage; checking the integrity of nuclear fuel chambers and monitoring low level radioactive storage containers.”

All optical elements within  Resolve Optics radiation tolerant lens designs are made using cerium oxide doped glass or synthetic silica enabling them to withstand radiation doses of up to 100,000,000 rads and temperatures up to 55°C without discoloration or degradation of performance.

All Resolve Optics  non-browning lenses provide high image resolution and minimum geometric distortion from 400 to 750nm.

For further information, visit  www.resolveoptics.com

Sellafield Ltd removes 100 tonnes of contaminated equipment from world’s biggest open-air nuclear store

Nuclear experts at Sellafield in the UK have successfully removed one hundred tonnes of contaminated redundant equipment from the oldest fuel storage pond at Europe’s oldest and most complex nuclear site.

The 60-year-old pond, known as the Pile Fuel Storage Pond (PFSP), has to be emptied carefully as part of a plan to clean-up and decommission the oldest nuclear facilities in the UK.

The metal waste retrieved from the ageing facility is the equivalent in weight of a blue whale or a Boeing 757 aeroplane.  Although there remains a further 650 tonnes of contaminated metal to be retrieved from the pond,  removal of the first 100 tonnes demonstrates great progress on the programme to successfully decommission the facility.

The pond was initially constructed to store fuel from the Windscale Pile reactors, whose primary focus was producing plutonium for the UK’s nuclear deterrent.

The storage pond stopped receiving fuel in the 1970s, but to this day the PFSP remains the largest open air nuclear storage pond in the world, at 100 metres long.

Dorothy Gradden, head of programme delivery in the Pile Fuel Storage Pond, said: “Our nuclear forefathers developed a technology that helped the UK secure a seat at the global power table in the aftermath of the Second World War. The oldest plants at Sellafield were built in a time before computers existed and with little thought given to how they would be decommissioned. The challenge for this generation of nuclear pioneers is to safely decommission those earliest facilities as cost effectively as we can.

“When you are decommissioning a facility as old as this, issues can and do arise which mean that carefully laid plans and schedules need to be changed – and this happened frequently for us and the operations team has developed additional skills to meet all new challenges."

Derek Carlisle, PFSP head of projects said: “Sometimes it’s difficult to appreciate the decommissioning progress being made, because by the very nature of what we are doing things can take a long time and seem to cost a lot of money.

“However, when you think about 100 tonnes of equipment – the size of a whale or a Boeing 757 – it really does give you some scale as to the difficulty in removing that much mass from the biggest, and one of the oldest, nuclear storage ponds in the world.”

The PFSP was the very first nuclear fuel storage pond constructed at Sellafield. Construction started in 1948 and the pond was commissioned and started to receive fuel in 1952.

Originally nuclear fuel from the Windscale piles – constructed specifically to make plutonium for the UK’s nuclear deterrent – was received, de-canned and cooled in the facility.

Later in the 1950s the pond was adapted to receive fuel from Magnox power stations, the first of which in the world, Calder Hall, was opened at Sellafield in 1956.

Following the closure of the Windscale Pile reactors and the commissioning of the new First Generation Magnox Fuel Storage Pond, operations in PFSP were scaled down.  When decanning in the plant stopped in 1962 the pond continued to be used as storage for fuel, contaminated items, and operational waste.

Derek added: “The 100 tonnes of contaminated metal we have removed so far has been cleaned up for disposal in the national Low Level Waste Repository near Drigg.”

Highlights in the retrievals programme to date include:

* Removal of the very last remaining pile fuel decanner, weighing in at over one tonne;  
* Recovery of two tall tools or masts – similar in height to an average two-storey house - lifted from the pond and size reduced in situ;
* Eight of the 30 waste and transport flasks recovered each weighing 2-3 tonnes;
* Stripping out and export of redundant metal structures above and below the water line in the pond bays.
 
For more information, visit www.sellafieldsites.com