Lessons Learned Decommissioning the UK

By Jean FLECHER, Vice-President, Recycling & Waste Management, AREVA UK Ltd.

Building on more than three decades of experience in nuclear site decommissioning for sites in the United Kingdom, AREVA was awarded a new contract in July 2015 by the Nuclear Decommissioning Authority (NDA) to provide engineering services to no less than 15 decommissioning sites across the UK. The contract includes awards to AREVA and its British partner Atkins for engineering and design services at decommissioning projects, as well as studies for waste management from nuclear site decommissioning to be performed by AREVA’s British safety and environmental risks assessment consultancy subsidiary, AREVA RMC.

With so many sites involved, there will be diverse challenges and situations that have never been encountered before. The strategies and solutions to these projects will have to be adapted to the situation at each site.  AREVA’s long and diverse experience in this field will be a key asset to ensuring the smooth and successful delivery of this decommissioning project.

AREVA has accumulated over 40 years of experience in deploying and managing Decommissioning and Dismantling (D&D) projects at fuel cycle facilities and at nuclear power plants. This includes, for example, the company’s own La Hague site and as the prime contractor for the French Atomic Energy Commission (CEA) at the Marcoule used fuel facility, both located in France. On an international level, AREVA has provided support to E.ON for the Stade and Würgassen nuclear reactor projects in Germany, the U.S. Department of Energy at the Hanford site in Washington, and to TEPCO as part of the Fukushima Daiichi site rehabilitation, among others.

In 2008, a dedicated business unit was created within AREVA to capitalize on this experience and to concentrate the specific skills required to optimize the economics of decommissioning projects in one division. AREVA’s clean-up activities later joined this organization in 2014. This business unit reflects a key lesson learned over the past few decades that decommissioning is a significantly different business compared to the day-to-day operations of a nuclear facility. Project functions need to be viewed from a different angle, challenged and consequently adapted in order to optimize costs and schedule. A clear understanding of the local market and regulatory procedures is also critical. Therefore, the development of strategies and solutions for the UK sites will be made from the UK, by AREVA’s UK Engineering & Operation organization in partnership with Atkins for the concerned segments or by AREVA RMC.

Three examples are developed in this article to illustrate these specificities. Safety management needs to be taken into account for the ever-changing configuration of a plant under D&D, which is a rather new situation for authorities. Also, the production of waste is significantly different in terms of volume, activities, conditioning and the disposal path. Lastly, technology is important, but technical issues are often less critical than good management and planning.

Vast Experience to Serve New Projects

AREVA has long and sound experience in creating and adapting dismantling and decommissioning (D&D) strategies to a variety of nuclear fuel cycle facilities, processes and working conditions. These include highly contaminated fuel cycle facilities containing mechanical and chemical processes, hot cells, glove boxes, fuel pools, vaults and tanks. This experience also covers used fuel recycling/reprocessing plants, mixed oxide (MOX) fuel fabrication plants and various radio-chemical plants as well as power production and research nuclear reactors containing large contaminated and activated equipment. The scope includes uranium processing facilities such as former mining site remediation, uranium enrichment plants and uranium fuel production plants. In addition, various types of legacy waste are often present at the sites which need to be retrieved, repackaged and sent for disposal. Some of the most challenging projects are those involving the presence of very high levels of contamination from fission products (Cs, Sr) as well as actinides (U, Pu).

The involvement in a decommissioning project usually starts long before the actual end-of-life of the facility. At this time, the preliminary decommissioning scenario is developed and corresponding cost estimates are provided to help the owner/operator to establish the provision for future D&D.

When (or preferably before) the facility shuts down, the first task consists of establishing a detailed diagnostic to first refine the overall scenario, confirm the schedule and cost estimate and then prepare the license application for dismantling. Engineering studies are performed to define the detailed approach, analyzing technologies, processes and equipment that were used in the facility, type and quantity of nuclear materials contained, and waste management strategies. In this phase, a particular attention is devoted to the optimization of the scenario in terms of cost, schedule and risk management.  The two main factors here are waste management (final form, volume and destination) and optimization of fixed costs.

The next phase consists of retrieving and recovering any significant quantity of nuclear material remaining in the plant, and then decontaminating/cleaning the rooms and equipment in order to facilitate the subsequent dismantling phase by significantly reducing residual activity and hot spots. The dismantling phase generally entails cutting piping and other internal equipment and demolishing the building if required. The waste produced is very carefully sorted, processed and packaged before being sent to dedicated storage and disposal locations. Then, a special effort is put forth to eliminate residual activity from liquid and solid waste through final cleanup. After final inspection by the authorities, the buildings and recovered areas can be fully decommissioned for re-use of the land and assets.

These five major steps are implemented consistently throughout AREVA’s D&D projects, usually in order to bring facilities to contamination levels compatible with International Atomic Energy Agency (IAEA) stage II.

This section details the approaches developed and results obtained at selected facilities such as the UP1 recycling plant at Marcoule, UP2-400 recycling plant at La Hague and the MOX plant at Cadarache, comparing these D&D projects, with a special focus on the development and application of lessons learned.

Approaches and Results – Concrete Examples
Marcoule UP1 Plant

From 1958 to 1997, the UP1 plant at Marcoule – located in the south of France – reprocessed and recycled nearly 20,000 tons of used fuel for special defense application reactors as well as fuel from the first generation of electricity generating reactors in France (natural uranium fuel, CO2 cooled, graphite moderated). Cleanup and dismantling of the UP1 plant and the associated units started in 1998. Since 2005, the UP1 facility has been operated by AREVA as a Management & Operation contractor to the CEA (Atomic Energy Commission). This is a huge decommissioning project with 14 main facilities, over 1,000 rooms and cells to dismantle and cleanup, 700 tanks, 21,000 tons of equipment (of which 2% are High Level Waste). The end of this D&D project is planned for 2040.

To date, the project is well on track with 95% of the radioactivity already removed from the high-level areas through rinsing operation.

To date:

  • The vast majority of the fuel decladding facility equipment has been dismantled.
  • The entire plutonium and batch dissolution lines have been decontaminated and dismantled.
  • Uranium/plutonium separation and continuous dissolution lines are currently being dismantled and detailed design is being conducted for D&D of fission products evaporators. Specific rinsing operations are being conducted on former fission products storage tanks prior to dismantling.
Fig. 1 Plasma torch for cutting the bottom of a dissolver from the dissolution line

Cleanup & dismantling operations at Marcoule consist mainly in rinsing the circuits, using conventional reagents (that were used during the operational life of the plant) as  well as more specific and aggressive chemical reagents that are more efficient to remove the encrusted material (while ensuring that such new chemicals are still compatible with  the effluent and waste processing lines). For example, a program of specific rinsing operations of fission product tanks was developed in order to reach a level of 95% of low level waste when the equipment was subsequently dismantled. Then operations consisting of decontaminating, cutting and dismantling the equipment are performed on pumps, filters, tanks, pipes, glove boxes, etc. to condition them for disposal. Many challenges were faced to operate in an old and complex facility at Marcoule, and it required the design and/or improvement of specific tools & processes while carefully balancing the pros and cons. The use of plasma torches for cutting scrap metal is a good example of a best practice deployed on projects after successful trials. It was not obvious to qualify such a high temperature technology in a highly active environment, but the pay-back in efficiency and speed of operation is significant. For example, the highly contaminated dissolvers from the batch dissolution line were dismantled using plasma torch cutting tool (see Fig. 1) with a reduction of a factor two of the cutting time while providing significant additional as-low-as-reasonably-achievable (ALARA) benefits. This plasma cutting technology is now used in other D&D projects.

Fig. 2 Remote controlled tool carrier equipped for intervention inside the ventilation duct

In another area, the chemical decontamination technologies and methods were systematically adapted to the equipment to be processed. A large number of cells and highly contaminated areas required the development and adaptation of remotely operated devices to conduct decommissioning operations in fully remote conditions for the most complex cases. For example, in a highly contaminated ventilation duct, AREVA developed a small robot able to scrape and vacuum cleanup the uranium nitrate powder (Pu contaminated) inside the duct (see Fig. 2).

One of the key factors of project success was and remains the “social management.” This consists of training former operators to evolve from an operational culture (40 years of activity) to a decommissioning and project management culture. Former operators are well-trained to continue operating the site infrastructure that is still used to support the decommissioning activities (such as utility supply, waste conditioning and storage, effluent treatment stations…). The historical knowledge of former operators is also critical to maintain continuity and memory of past activities when the plant was in full operation. However dismantling, cleanup and closure is a very different business than standard operation of a plant. A dedicated project and contract management systems has to be set up. When the workforce cannot be transferred to another plant, extensive training of former operators is mandatory to obtain optimal operational performance while ensuring an irreproachable level of safety. To create a mixed team that includes newcomers and project managers together with existing personnel and trainers is a key factor.

An integral element is to make safety the priority. Personnel safety needs to continuously improve. An aggressive plan was put in place in 2005 and effectively deployed in the field with engagement from all personnel. The team improved its safety results to achieve a zero-accident rate level over the year 2010.

Fig.3 UP2 400 plant of La Hague
La HAGUE UP2-400 Plant

UP2-400 was AREVA’s first commercial used fuel recycling plant (see Fig. 3). Between 1966 and 1998, UP2 400 processed nearly 5,000 tons of natural uranium used fuel from graphite-gas power reactors, 4,500 tons of fuel from pressurized water reactors, and a few tons of used fuel from breeder research reactors. UP2 400 was shut down in late 2003 and replaced with two new plants: UP2-800 and UP3.

The decommissioning project was launched in 2009 and is expected to take place over a 25-year period. This is another large D&D project with a significant amount of legacy material to retrieve (hulls, end pieces, resins, sludges…) prior to starting the actual dismantling operations. There is about 32,000 cubic meters of waste to remove and process. The operation will involve 500 staff at its peak.

The project is currently in the detailed planning and licensing phase. Extensive studies were performed to optimize the final scenario. A task force was established in 2008 to systematically challenge the baseline. As the owner and operator, AREVA is directly responsible for the dismantling operations which are funded through the provision set aside during its operational life.

Three major progress areas were identified leading to a 25% reduction of the lifecycle cost of the project. The first progress area focused on the management of the waste and its processing. Detailed assessment showed that the past tendency was to use the techniques already in place while the facility was in operation to process the waste. However, dismantling is different because it produces more waste than standard operations. The induced cost of processing and disposal of D&D waste is a very important contributor to the final cost. New techniques were developed, for example, to process sludges (drying and pelletizing) instead of immobilizing in a conventional matrix, which leads to much larger volume of final waste for disposal. The extent of segmentation of the solid waste was also challenged and optimized. Cutting equipment in small pieces can be very labor intensive, a trade-off must be made between reducing the volume of the waste – and hence its disposal cost – versus increasing the processing cost in such a way that it may become much more expensive to cut it into pieces.

The second area of major progress was the reduction of the fixed costs. These are the expenses related to the support facilities around the core buildings that are being dismantled (such as the utilities supply, the effluent and waste treatment plants) and the general support functions of the project (maintenance, health physics, procurement, controls …). When switching from operations to D&D, a number of usual practices can be challenged and streamlined.

The third area of progress was to optimize the supply chain. It was demonstrated from previous experience that simplifying the procurement process, reviewing the work packages allocation and involving the subcontractors from very early in the strategy development should lead to another set of significant cost reductions.

The project is currently waiting for administrative authorizations to enter into the operating phase.

Cadarache MOX Plant

Between 1962 and 2003, the Cadarache MOX plant initially fabricated fuel for fast neutrons reactors and then recycled MOX fuel for French, Swiss and German electrical utilities.

Following five years of preparatory studies, material retrieval and cleanup, the dismantling operations began in 2009. Since then, AREVA has been conducting these activities as the Management & Operation contractor for the CEA, which owns the facilities. As part of this project, 422 glove boxes or glove box equivalents and 38 tanks are planned to be dismantled over a period of about 10 years. The dismantling activities are mostly manually-operated and, therefore, primarily depend on worker reliability, operating expertise and training. To date, 90% of the glove boxes, tanks and pipes have been actually dismantled (see Fig. 4).

Fig. 4 Cell 1 of the ATPu facility of Cadarache (before and after)

The challenges ahead will be to manage safety; maintain cost and schedule while working on a first-of-a-kind D&D project; managing human resources; manage waste; and manage contractors. Specific approaches were successfully developed to handle these challenges.

Nuclear safety in a decommissioning project is challenging by nature. The configuration of the facility is changing almost every day when the D&D operations are in progress. As the situation is thus continuously evolving, it is a new challenge for safety authorities. The key to obtaining authorizations in due time is to prepare the D&D plan early and to share it with the regulators as soon as possible. The plan needs to be flexible enough to accommodate for unexpected events as much as possible (such as the discovery of material inventory in areas impossible to investigate accurately without actually dismantling the glove box). The scenario should avoid a monolithic technical approach, and plan A and plan B should be developed concurrently in order to prepare for the unexpected. If the license is granted on the basis of one approach only, it is difficult and costly to change later.

Maintaining project life cycle cost is a constant concern for such first-of-a-kind-project. The estimated cost can be stabilized thanks to exhaustive diagnostics and good knowledge of the plant history. Other important factors to avoid surprises include preparation work, training operators, waste management and an integrated supply chain.

Managing human resources was and remains quite challenging because in this project it was necessary to integrate the entire, existing workforce from the beginning. This challenge was identified early and taken into account as a high priority for the project from day one. Specific measures were taken to transition staff from the operational to dismantling culture. The strategy was to begin with the cleanup and material recovery step because it is similar to the normal activities with which plant operators are familiar. In the meantime, a systematic training program was set up to qualify and certify operators to become dismantlers. This included coaching, a “plutonium school” and long hours working on scale-one mock-ups. Finally, a thorough re-allocation plan was put in place to progressively transfer former operators to other operating plants within AREVA and to switch to specialized workers for the main decommissioning activities.

Waste management is crucial to maintaining cost target. Costs related to waste management and disposal represent more than 50% of the total project costs. Efforts are made continuously to minimize the quantity of ‘High Level’ or ‘geological waste’ which are the packages that are too active to be disposed of in a surface repository, as is done for ‘Low Level’ and ‘Very Low Level’ category. The project’s High Level Waste has been limited successfully to less than 10% of the total quantity of waste for disposal to date.

Managing the supply chain is another important factor for success. Integration of the subcontractors is a key point to ensure their appropriate level of training and safety culture. However, the contractualization is still competitive and reward is still based on performance. Consequently, asking sub-contractors to challenge themselves and contribute to the continuous improvement of the global project performance is necessary.

Lessons Learned Summary
  • The management of safety and personnel in a continuously changing environment is critical to success.
  • The management of such D&D program requires the creation of specific project management tools and processes as well as the creation of dedicated skills and disciplines. Relevant training programs must be developed.
  • The facility infrastructure must be maintained in operation after the shut down, especially ventilation system and handling devices are crucial for D&D works.
  • The knowledge of the initial conditions is crucial to define a credible D&D scenario. Additional investigations are often necessary but the constraints surrounding operations in a nuclear facility lead to limitations on the ability to conduct them. A compromise must be found by weighing costs and benefits of the technical complexity, feasibility, and safety.
  • The definition, production, flow, transportation, interim storage, evacuation and final storage of waste package from a facility are the backbone of the D&D projects.
Conclusion

AREVA has a long and vast experience in the clean-up and dismantling of large and complex nuclear facilities. This was gained initially through work for the company’s own plants and has since expanded to external customers. In 2008, the establishment of a dedicated business unit concentrating these important skills and lessons learned provides the best avenue to offer to our customers optimized safety, performance, cost and schedules. Transitioning nuclear sites from operations to D&D is a quantum leap. The assistance from specialised teams is paramount to ensuring successful and smooth project delivery.

 

About the Author:
Jean Flecher has an engineer degree in Chemical Engineering. His early career at AREVA involved a variety of roles in design, development and commissioning of nuclear fuel processing facilities, as well as various non-nuclear projects.

Jean then moved to the nuclear material transport business as Contract Director in charge of negotiating and implementing transport contracts, which notably included contracts with Japanese utilities for the transport of MOX fuel from Europe to Japan (in partnership with BNFL).

Jean has been most recently developing back-end market for AREVA in the UK. In addition to his work for a number of Tier-2 contractor projects, Jean has been involved with the country’s Low-Level Waste Repository and Sellafield bids, as well as the company’s proposal for a new MOX plant to recycle the UK’s plutonium stockpile, known as the AREVA Convert project.