What does decommissioning a retired Czech nuclear power plant cost? – Part 2

Anti-nuclear activists’ materials often argue that the decommissioning of no retired nuclear reactor has yet been completed. However, this is not true. It is therefore interesting to look at the real situation in this area.

This is Part 2 of the article; Part 1 is available here.

Decommissioning power units in France and Spain

Let us also look at France and Spain, where the first decommissioned units have likewise reached an advanced stage. France’s Brennilis plant serves as an example of the decommissioning process for a nuclear power unit. It was a prototype gas-cooled, heavy-water-moderated reactor. The reactor started up in 1966 and had an output of 70 MWe. However, France also abandoned the use of this type and focused on pressurised water reactors. The plant operated until 1985. During the first stage of its decommissioning, the fuel was removed and the cooling circuits were drained. The second stage, which began in 1995, involved dismantling equipment and decontaminating all buildings except the reactor itself. The accumulated radioactive waste was also removed. This stage ended in 2005. The third stage then saw the dismantling of equipment inside the containment, such as the steam generators and the reactor pressure vessel itself. It is due to conclude with the demolition of the containment itself. Ultimately, the entire area of the former plant should be released. The total cost of decommissioning the plant is estimated at €480 million.

The first pressurised water reactor to begin decommissioning in France was Chooz-A. It was a 320 MWe reactor that operated from 1967 to 1991. In 1995, the fuel assemblies were transported to the recycling plant at La Hague. Since 2014, the reactor vessel has been dismantled underwater. The entire decommissioning process was expected to be completed in the first half of the 2020s.

The decommissioning of Spain’s first nuclear power plant has also made considerable progress and is being carried out by Enresa. This is the José Cabrera plant, also known as Zorita. It is a first-generation pressurised water reactor with an output of 142 MWe. It began operation in 1968 and was shut down in 2006. Preparations for decommissioning were carried out between 2006 and 2009 by the operator, which dealt with the spent fuel and determined the radioactivity levels of various components. The spent fuel was temporarily placed in a dry interim storage facility at the plant site. Enresa then took over the plant and will dismantle it. First, the turbine hall equipment was dismantled and disposed of. This did not differ from the dismantling of any thermal power plant. Radioactive components began to be dismantled in 2011. The reactor pressure vessel and internal piping were cut up underwater, which shielded the radiation. This most demanding part of the plant decommissioning work began in 2012, and the dismantling of the reactor vessel, steam generators and biological shielding was completed by 2016. The buildings then underwent full decontamination. Their gradual demolition began in 2018. Dismantling of the containment could therefore begin in 2019. Everything was expected to be completed in 2020. Around 104,000 tonnes of waste were expected to arise from the plant’s decommissioning. Only around 4% of it will be radioactive. Conventional waste is sent to processing plants. Low- and intermediate-level waste is periodically transported to the El Cabril repository.

It is clear that Europe also has extensive experience with decommissioning shut-down nuclear units. In this case, it is often advantageous that spent fuel can be sent for recycling. The first permanent nuclear waste repositories are also being built in Finland and Sweden.

Czechia and Slovakia – Jaslovské Bohunice A1 and V1

No unit has yet been shut down in the Czech Republic, so there has so far been no need to address their decommissioning. Just for interest, a nuclear facility has already been completely decommissioned successfully in Czechia. It was the small ŠR-0 research reactor in Plzeň; entirely different activities are now carried out at the site, and no trace of the reactor remains. However, it was a very small facility compared with power reactors.
Three reactors have, however, ceased operation at Slovakia’s Jaslovské Bohunice plant. These include the A1 reactor, which was a special Czechoslovak design. It was a 110 MWe reactor moderated by heavy water and cooled by carbon dioxide gas. Czechoslovakia selected this type because it enabled the use of unenriched fuel. In principle, it would thus have enabled full independence for Czechoslovakia, given its uranium ore reserves. As was apparent from the previous part of the text, Germany, France and other countries also tested similar reactor types. However, it later became clear that this more complicated technology could not compete at the time with reactors cooled and moderated by light water. They therefore did not progress from experimental prototypes to commercial models. Czechoslovakia had thus effectively decided to use VVER reactors even before the A1 reactor was commissioned. The A1 reactor entered service in 1972. The first two VVER440 reactors, as Jaslovské Bohunice V1 units, also began to be built that year. Unit A1 was experimental, so a number of problems had to be overcome. Two serious accidents also occurred. Fuel assemblies could be replaced while the plant was in operation. During one such replacement in January 1976, the sealing plug of a fuel channel was not fully locked, and it was ejected from the reactor into the reactor hall. Carbon dioxide was released and spread through part of the plant. Plant workers later used breathing apparatus to reinsert the fuel assembly. There was no release of radioactivity, but two workers died after suffocating on carbon dioxide. In February 1977, silica gel beads from a moisture absorber entered a fuel assembly, causing it to overheat and melt. The moderator entered the primary circuit, damaging the fuel cladding and allowing fission products into the primary circuit. Radioactive substances also entered the secondary circuit through leaks in the steam generator. The plant was shut down as a result of this accident.

Decommissioning the plant is more demanding because of the accident and contamination. Its project was prepared in the 1980s and 1990s and is being implemented by JAVYS (Jadrová a vyraďovacia spoločnosť a. s.). It comprises five stages and is expected to last until 2035. The first took place between 1999 and 2008. The most important step in this stage was the removal of spent fuel to Russia. At the same time, new process lines for treating liquid radioactive waste were prepared, while the solidified radioactive material was placed in special fibre-reinforced concrete containers. A radioactive material repository at Mochovce was also commissioned, allowing the containers to be transported there. Some of the most radioactive waste was processed on a vitrification line. A number of areas were decontaminated. The most important task was to ensure the solidification of radioactive waste, particularly liquid waste, and prevent its release. This eliminated the radiological risks.

During the second stage, which took place from 2009 to 2016, equipment in the external buildings was decontaminated and dismantled. The dismantling and disposal of a range of equipment outside the buildings, pipelines and unnecessary tanks were also secured. Contaminated soil was removed and radioactivity monitoring was ensured. The refuelling machine and other equipment were dismantled.

In the transition to the third stage, equipment such as the heavy-water loop was dismantled, cooling-water tanks were cut up, and the oil management system, oil tanks and pump system were dismantled. The vacated rooms were cleaned, adapted and prepared for use during subsequent decommissioning stages, mainly for the temporary storage of some more active components. During the third and fourth stages, which are expected to last until 2025, work will focus on activities in the main production block, namely the primary circuit and related technological components. Highly contaminated equipment used to prepare spent fuel for transport will also be dismantled, as will steam generators, turbocompressors and other associated primary-circuit equipment. In the fifth stage, the reactor itself and other equipment in the reactor shaft will be dismantled, along with the equipment installed for the decommissioning process.

The ultimate objective of the decommissioning, which is expected to end around 2035, is the complete clean-up of the site and buildings and their conversion into a technology centre that would in future serve as a base and support facility for the decommissioning of the Jaslovské Bohunice V2 and Mochovce nuclear power plants.

The two VVER440 reactors at Jaslovské Bohunice V1 began supplying electricity in 1978 and 1980. Mainly under pressure from Austria, they were shut down in 2006 and 2008 after Slovakia joined the European Union. Before decommissioning could begin, the spent fuel had to be removed. In January 2011, the last fuel assemblies from the second V1 unit were transported to an interim spent fuel storage facility. JAVYS has therefore also been decommissioning this plant since 2011. During the first stage, which ran until 2015, non-active systems and equipment were dismantled, structures were demolished, and radioactive waste from decommissioning was processed. Non-active material, mainly metals, was sent for recycling. Turbine hall equipment and diesel generator sets were dismantled. An integrated radioactive waste repository was prepared.

During the second stage, which is expected to end in 2025, full decommissioning of the plant began. Demolition of all four cooling towers was completed in October 2018. Work on the primary circuit has also begun. The first steam generator was removed in March 2019 and the last in July of the same year. The steam generators weigh 145 tonnes and are 11.8 m long. All are now located in a storage facility, where they will be gradually segmented. Special cutting equipment was developed for this purpose. Cutting began towards the end of 2019. There are now 1872 tonnes of material, from which approximately 1360 tonnes of metal can be recycled. Total costs of decommissioning the V1 plant are expected to reach €1.1 billion.

Conclusion

There is now also experience with decommissioning a nuclear power plant after an accident. This is the case of Unit 2 at the Three Mile Island nuclear power plant. In the end, even the partially melted core, which was 15 cm short of melting through the reactor vessel, was removed from the reactor and the containment was decontaminated. The accident occurred in 1979, and by 1985, 90 tonnes of partially melted fuel and 150 tonnes of other highly radioactive material resulting from the accident had already been removed. Remediation work officially ended in 1993 and cost around $1 billion. Dismantling of the reactor building itself was postponed until the shutdown of Unit 1. It was shut down in 2019. The current decommissioning of both units will be cheaper.

As regards spent nuclear fuel, funds are set aside on the assumption that it will go to an underground repository, which is in fact the least efficient and most expensive option. If advanced reactors use this fuel to generate energy and only its fractional remaining part ultimately goes underground, most of the funds set aside will be saved. Construction of Finland’s first permanent Onkalo repository is already at a very advanced stage, and a similar facility is also being prepared in Sweden.

It is clear that decommissioning a retired nuclear power plant is not a simple matter. Nevertheless, there is already some experience with it, and reasonably sound estimates of its cost can be made and reflected in the price of electricity. In addition to the sources already mentioned, useful materials, analysis and links are available here and here. Costs vary across a fairly wide range. They depend on whether this is a standalone unit or several units being decommissioned simultaneously. The size of the unit and the intended subsequent use of the site are also important. Broadly speaking, a 1 GWe unit requires around €1 billion in a conservative estimate. As already mentioned, in most cases the operator must accumulate decommissioning funds and include them in the price of electricity. A large proportion of materials are non-active or low-level radioactive and can be recycled. The advantage is that they are concentrated in one location with a very limited area and are subject to very careful oversight by national and international institutions. If these costs are to be discussed, this must also be done in the context of the costs associated with electricity generation from other sources (see, for example, an earlier article).