Nuclear decommissioning: plans, challenges, and innovations20 October 2021
Speakers at a recent event highlighted several difficulties facing nuclear decommissioning projects and discussed some of the R&D and technical innovations that are supporting decontamination, remediation, and radioactive waste management. Caroline Peachey reports
The virtual event, Nuclear Decommissioning – Plans and Innovations, was opened by Douglas Kerr, nuclear decommissioning consultant at Jacobs and a representative of the World Nuclear Association’s working group on Waste Management and Decommissioning.
Kerr shared the findings of the WG’s report Methodology to Manage Waste from Nuclear Decommissioning, which aims to bring together knowledge and expertise regarding management of material and waste and to provide guidance for those facing new decommissioning challenges. Kerr gave an overview of the three main strategies for nuclear power plant decommissioning — immediate dismantling, deferred dismantling, and entombment — and discussed the cost, risk and regulatory factors associated with each approach.
He explained why the site end-state and decommissioning strategy should be clearly defined early in project planning: they both affect numerous factors including radwaste inventories, waste routes, costs, and schedule. Immediate dismantling is the preferred strategy, both from a public acceptance and cost driver perspective, Kerr said. However, he did suggest that this could potentially be an issue on sites with multiple reactors undergoing decommissioning at the same time. Kerr also identified waste management as a ‘typical bottle neck’. This was also highlighted during the subsequent panel discussion between European utilities.
Plans for nuclear decommissioning in Belgium, Finland and Sweden
During a panel discussion, Mats Ahlström, programme manager at Vattenfall (Sweden), Peter Berben, head of decommissioning and radioactive waste management, ENGIE Corporate (Belgium) and Matti Kaisanlahti, leading specialist, decommissioning, Fortum Power and Heat Oy (Finland), all shared updates on their nuclear decommissioning plans. While there is no ‘common strategy’ for decommissioning in Europe, there were common themes and challenges experienced by the three organisations involved. These were discussed in detail in their presentations and the following Q&A session with moderator Kristina Gillin, principal consultant, nuclear waste and decommissioning at Vysus Group.
All three countries are adopting the immediate dismantling approach. Ahlström, who is programme manager for decommissioning of the Ringhals 1 BWR (shut in December 2020) and the Ringhals 2 PWR (shut in December 2019), presented the decommissioning roadmap. He said that preparatory work is currently underway on site to split Ringhals 1&2 from operating units 3&4 and that the plan is for D&D to start in September 2022. D&D of special items including the reactor pressure vessels and steam generators is expected to run from April 2023 until 2027. This will run in parallel to ‘bulk’ D&D of the other radiological items. Conventional demolition is planned for the early 2030s.
Peter Berben from ENGIE noted that Electrabel operates seven pressurised water reactors in Belgium at the Doel and Tihange sites, which are scheduled to close by 2025. The first unit to be shut down will be Doel 3 in October 2022 followed by Tihange 2 in February 2023. Electrabel, too, has opted for an immediate dismantling strategy — at least for the first two units — and is currently in the preparation phase for the 20-year decommissioning programme, Berben said. The focus in the initial five-year post-operational phase will be on removal of the fuel from the reactors and operational radioactive waste from the spent fuel pools, as well as chemical system decontamination. Once this has been completed and a dismantling licence received, the 13-year dismantling phase can begin.
Kaisanlathi from Fortum outlined the plans for decommissioning Finland’s Loviisa nuclear power plant, which comprises two VVER-440 reactor units. In Finland there is a six-year licensing period that follows closure of the reactor (due to start in 2022 for Loviisa 1). This will be followed by a three year ‘transition period’ during which all the systems are prepared for decommissioning. Dismantling of Loviisa 1 is expected to start in 2031 and last until mid-2034, Kaisanlathi said. The plan is to start this work at Loviisa 2 at the beginning of 2034 and it will run until mid-2037. In terms of the technology that will be used, Kaisanlathi explained that Fortum will use “well known, conventional technology”, including sawing, plasma cutting, diamond wire cutting, and remote-controlled equipment, in some cases.
Another site that is planning to embrace robotics and remote technology is Sellafield. During the third session of the day Rav Chunilal, head of Robotics & Artificial Intelligence at Sellafield Ltd outlined the UK Nuclear Decommissioning Authority’s plan to achieve a “50% reduction in decommissioning activities carried out by humans in hazardous environments by 2030,” bringing about benefits of cost and schedule reduction.
Radioactive waste management remains key challenge
Peter Berben told delegates the biggest challenge ENGIE faces is radioactive waste management, as in Belgium today there are no final disposal solutions for nuclear waste. Berben said he hopes that ‘in a few years’ a near-surface repository will be available for low-level waste. For category B (high and intermediate-level waste) such as activated metal or waste with long-lived radioisotopes there is ‘no policy in Belgium’ and it is currently in intermediate storage at sites. Berben concluded by saying that “due to the lack of clear evacuation routes for radioactive waste, planning and the execution of decommissioning is not an obvious task in Belgium.” He did however say that ENGIE is looking to mitigate this by splitting nuclear decommissioning activities from radioactive waste management, which means that dismantling can continue, with interim storage of waste on site pending availability of disposal solutions. This means that waste won’t become a ‘bottle-neck’ in the process.
Echoing this and Kerr’s observations from the first session, Kaisanlahti noted that waste generation, dismantling, cutting, characterisation, packing, intermediate storage, transport and disposal should be designed as “not to impact the time schedule”. Having an on-site diposal facility at the Loviisa site helps to mitigate this, he said.
Ahlström, who is managing decommissioning at Ringhals highlighted the “cost challenge” being faced by the project. He identified the bulk decommissioning phase as the ‘biggest chunk of work’ and said that Vattenfall is aiming to ensure it has efficient processes in place on a small scale before execution. Also critical is ensuring waste management routes, in order to avoid any ‘bottle necks’ as well as the need to create interim storage on site. Finally, Ahlström said that Vattenfall is looking to build some flexibility into its programme so it can begin work on different work packages, should any delays occur.
Organisational issues were also raised, with speakers noting that decommissioning will affect the number of personnel, the required skills and change attitudes of those working at the plant.
Innovations for nuclear decommissioning: from robots at Sellafield
The final sessions of the event highlighted some of the innovative solutions that are being developed for nuclear decommissioning and radioactive waste management.
Speakers from Sellafield highlighted how robotics and artificial intelligence are supporting the decommissioning challenges on site and beyond. “We are not just looking at the challenges at the Sellafield site, but also across the NDA group’s UK sites. This is a growing field, we need to pick up the pace and embed this work into business as usual in a safe and secure manner,” said Chunilal.
Sellafield Ltd already has a robotics framework in place, which groups air-, land- and water-based robotics and AI, and a range of case studies were presented. Pete Allport, remote handling manager, engineering & maintenance, specialist equipment services, Sellafield Ltd, explained how drones supported both external and internal inspection of a stack on site. He also discussed efforts to develop beyond visual line of sight (BVLOS) capabilities that will be utilised to conduct semi-autonomous inspection and survey missions in a routine manner.
Chris Hope, capability development manager, remediation, Sellafield Ltd, gave examples of technologies that have been used on site, including snake arm robots (eg LaserSnake back in 2017), ground-based ROVs (e.g. Curieosity developed with RED Engineering) and quadrupeds (the Boston Dynamic Spot, which was first demonstrated on site just a few weeks ago).
Keith Pickup, legacy ponds ROV manager, described the fleet of remote operated vehicles used in the legacy ponds and silos for activities such as fuel consolidation, skip cleaning, sludge and floor clearance.
Chris Ballard, robotics and AI manager introduced plans for a Robotics and AI Collaboration (RAICo). Partners in the venture include the University of Manchester, Sellafield Ltd, UKAEA, the National Nuclear Laboratory (NNL) and the NDA. “The Robotics and AI Centre will enable us to collaborate with our partners on innovation and R&D in solving real challenges under one roof, bring together the work being done by robots across Sellafield and build on the opportunities they offer,” he said.
Innovations in nuclear waste treatment and characterisation
On the nuclear waste treatment and characterisation side, Ansaldo Nuclear explained how it is committed to the development and delivery of more effective solutions for nuclear decommissioning and radwaste management. Alan Beven gave an overview of the company’s activities in European research and development projects including:
- INNO4GRAPH – development of a multi-joint manipulator for graphite blocks retrieval and handling.
- CLEANDEM – mechanical design and system integration of an unmanned ground vehicle for dismantling activities.
- PREDIS – development of a data handling, processing and fusion platform for pre-disposal storage.
Charles Mendes, key account manager, Ansaldo Nuclear, then discussed in detail a selection of innovative processes, including Wet oxidation (WOX), Phosphoric acid decontamination (PHADEC) and Iron-phosphate vitrification technology.
Helen Beddow from Nuvia also introduced a range of characterisation and waste management solutions that can support land remediation. These include surface radiation mapping using the Groundhog detector, rapid screening technology for excavator buckets using a Gamma Excavation Monitor (GEM) and high-resolution gamma spectrometry. Beddow also presented a case study on remediation of the Harwell Liquid Effluent Treatment Plant (LETP) in the UK.
Finally, Akira Ono, chief decommissioning officer at Tokyo Electric Power Company Holdings, Inc. shared an update on decommissioning progress at Fukushima Daiichi. His presentation also included a short video showing factory performance testing of a robotic arm that will be used for fuel debris removal from reactor 2 in 2022.
You can view the event on demand until 31 October. Please register here