The Core Melt Stabilization System for Hinkley Point C2 December 2020
Bilfinger is a ‘tier one’ contractor for Hinkley Point C in the UK and is working to design the fourth generation core melt stabilisation system
Above: Hinkley Point C unit 1 pictured in September, four years after receipt of a site licence (Photo credit: EDF Energy)
AT BILFINGER, PLANNING ACTIVITIES ARE in full swing. Ten engineers from subsidiary Bilfinger Noell in Wu¨rzburg, Germany have been studying construction plans, improvements and alternatives, pooling worldwide experience, evaluating and testing materials and analysing production processes. Their objective is to improve the core melt stabilisation system (CMSS) and make the UK’s Hinkley Point C plant, currently under construction, even safer.
NNB, a subsidiary of French energy group EDF, commissioned the design and construction of CMSSs for the site’s twin EPR reactors.
Managing director of Bilfinger Noell, Roland Pechtl, explains that the company has already provided CMSSs for Flamanville 3 in France, Olkiluoto 3 in Finland and Taishan 1 and 2 in China. “We are now combining the experience and knowledge gained from these successful projects and putting it to work in the design and construction of an even more advanced CMSS for Hinkley Point C.”
The CMSS limits the consequences of a core meltdown in the event of an accident. If a meltdown occurs, the CMSS directs the melt into a specially shielded area, instead of allowing it to spread uncontrolled. The components consist of melt plugs, support frames and the associated transport system. For inspections, the melt plug can be unlocked by a remote-controlled transport system, lowered onto the trolley and moved through the channel into the melt collection basin. This also creates a maintenance opening for work on the reactor pressure vessel. During operation, the melt plug is attached to the support frame below the reactor pressure vessel.
“Every CMSS is individually designed in accordance with the requirements of the respective power plant. We are, of course, constantly learning, incorporating the latest findings, technologies and processes and constantly enhancing the systems,” says Johannes Kessler, head of the nuclear technologies product division at Bilfinger Noell. “The basic design, however, has not changed in recent years”. He does not expect any fundamental changes in the CMSS for Hinkley Point C. “The functionality of the CMSS is established, its practicality proven many times over. Naturally, however, we are incorporating recent experience — especially the events in Fukushima — into the design of the two CMSSs for Hinkley Point C. After the CMSSs for Olkiluoto, Flamanville and Taishan, they are essentially the fourth generation.”
Technical detail improvements for this generation include testing materials and simplifying assembly of the CMSS on the power plant site. Production efficiency will also be improved further.
“A major part of our work will also be to ensure that all British legal requirements are implemented in line with regulations, especially with regard to nuclear standards, and also to consider the implementation of all occupational safety regulations as early as the design stage,” says Kessler. Until the CMSSs are completed and delivered — at the end of 2022 for unit 1, and the middle of 2023 for unit 2 — many more engineering hours will flow into the design, development and construction of the systems.
Tier 1 responsibilities
Expectations for the project and the attention it will generate are immense; Hinkley Point C is the first new nuclear power station to be built in the UK in over 25 years. First nuclear concrete was poured for the unit 1 reactor base in December 2018, and the basemat was completed on schedule in June 2019. The same ‘J0’ milestone was achieved on schedule at unit 2 this summer, despite the pandemic and a reduced number of workers on site.
Bilfinger’s order volume for the work on Hinkley Point C already exceeds half a billion euros. The industrial services provider, headquartered in Mannheim, Germany, has been awarded Tier 1 supplier status by EDF, a partner in managing the project strategically and one of the preferred suppliers for future projects. The relationship with EDF is the result of many years of successful collaboration on various projects in the nuclear industry.
Among Bilfinger’s Hinkley Point responsibilities is design and construction of a waste treatment centre for solid and liquid radioactive waste. The centre will collect and treat radioactive waste generated during reactor operation while minimising the space required. Specifically, Bilfinger is responsible for the design and delivery of the cementing plant as well as other equipment such as the sorting box, dosage measurement, shredder and in-drum compactor. The order also includes equipment for a hot cell including radiation protection windows, shielding gates and remote handling equipment. In addition, the company is responsible for equipment needed to cover and uncover and transport shielded waste containers.
Meanwhile, Bilfinger UK, Bilfinger Engineering & Technologies and Bilfinger Peters Engineering, have taken on the detailed design, prefabrication and supply of piping for the Balance of Plant package. Bilfinger UK, Bilfinger Engineering & Technologies Germany and Bilfinger Peters Engineering France have been commissioned with the detailed design, procurement, supplier management as well as the manufacture and installation of piping and equipment for the nuclear steam supply system. These companies are also responsible for detailed design, procurement, supplier management as well as the procurement and manufacture of piping for the balance of nuclear island system. In total, Bilfinger will lay a total of 340km of piping at Hinkley Point C and put in around 400,000 person-hours of work.