Decommissioning small Nordic reactors

BETWEEN 1951 AND 1966, A dozen small reactors went into service in the Nordic region. Of these, seven continued to operate into the 2000s. The last two to close were both in Norway: the Halden reactor and Joint Establishment Experimental Pile (JEEP) II in Kjeller. They were permanently closed in June 2018 and April 2019, respectively.

Research reactors in all four Nordic countries are now being decommissioned or preparing to be decommissioned. Funding of NKS, the Nordic nuclear safety research forum, includes research areas related to decommissioning and management of their reactor waste and spent fuel.

Kjeller and Halden

The first reactor in the Nordic countries, JEEP I in Kjeller, Norway, went critical as early as 1951. The site of this heavy-water research reactor later also housed JEEP II and a zero-power reactor, NORA. JEEP I and NORA were both closed and decommissioned in the 1960s, to the standards at the time.

In December 2018, JEEP II was shut down for control and scheduled maintenance. Corrosion was discovered on several components important for safety. After assessment, the owner concluded that the cost to repair was beyond what was feasible, and on 25 April it announced that JEEP II would not restart.

On a different site, close to the Swedish border, the Halden Boiling Water Reactor (HBWR) went into operation in 1959. Halden was used for a wide range of safety-related research as part of an OECD-NEA run project. The reactor was licensed to operate until 2020. But in June 2018, while temporarily shut down due to a safety valve failure, it was decided that licence renewal would not be pursued and the reactor would not be restarted for economic reasons.

The Norwegian reactors are owned and operated by the Institute for Energy Technology (IFE), an independent research foundation. To undertake the decommissioning, in February 2018 Norway established a separate state agency, Norwegian Nuclear Decommissioning (NND). The new agency is currently in the build-up phase, and among the first priorities is to outline how work will be distributed between NND and IFE. “We have established a close cooperation, and NND and IFE are working side by side to make this phase of nuclear operations run as smoothly as possible,” says Pål Mikkelsen, chief executive of NND.

The scope of NND’s activity is to manage nuclear infrastructure on behalf of the Norwegian government, for the purpose of decommissioning. This includes further decommissioning of JEEP I and NORA, since many of the structures left in place when they were decommissioned in the 1960s contain radioactivity above today’s release limits. 

Apart from decommissioning the four reactors and related facilities, NND will be responsible for spent fuel and radioactive waste management. Spent fuel from all four reactors is currently stored at the IFE sites in Kjeller and Halden. For low- and intermediate-level waste, Norway has a combined storage and disposal facility, in Himdalen, which has been in operation since 1999. To accommodate the volumes that will arise during decommissioning, this facility will have to be expanded or a new one built.

Sweden’s early reactors

Sweden’s Reactor 1 (R1) was the second reactor to reach criticality in the Nordic region and the first to be fully decommissioned. R1 was a heavy-water reactor, located in a rock cavern beneath the Royal Institute of Technology in Stockholm. Since 1998, the underground reactor hall has been used as a venue for activities such as art installations, concerts, media research, live theatre and film productions. (See NEI, December 2018 p42).

Next, two adjoining reactors were built at the Studsvik site: a tank reactor (R2) and a pool reactor (R2-0). These reactors had a wide range of uses, including education, research, materials testing and radioisotope production. A few critical assemblies were also built at Studsvik, but these were shut down and decommissioned early.

R2 and R2-0 were both closed in 2005, due to lack of commercial viability. As an interim use, new equipment was installed inside the building for conditioning and packaging of legacy plutonium, to enable subsequent shipment to the USA.

Dismantling of R2/R2-0 began in 2015 and is nearing completion. Christoffer Ellmark, project manager for the decommissioning, says: “Once the remaining structures have been free-released, the building will be demolished. Reuse of the building was considered but assessments concluded that it would be too costly to refurbish.” The Studsvik site as a whole will continue to host facilities for various nuclear-related activities for the foreseeable future.

The third reactor site in Sweden is Ågesta, in the Stockholm suburb of Huddinge. The Ågesta prototype reactor was a combined heat and power plant (10MWe). Following closure in 1974 the spent fuel, heavy water and two heat exchangers were removed. The facility has since been in ‘care and maintenance’, but parts of it are used to train fire fighters from the greater Stockholm area.

A few years ago, preparation for decommissioning of Ågesta began. Some stakeholders wanted to keep the facility for its architectural value, but consensus has now been reached to proceed with decommissioning the areas that contain the reactor and other radiological inventory. Ellmark, who is also responsible for Ågesta decommissioning, says: “Necessary upgrades, such as of the ventilation system and main crane, are now in progress. Pending regulatory approval, dismantling is scheduled to commence around new year. Once the radiological inventory has been removed, the rock cavern in which the reactor is housed will be sealed by grouting plugs in all the openings. The control room and other areas outside the final sealing can be made available for other uses.”

The power utilities are responsible for all nuclear decommissioning and waste management in Sweden. This includes legacy facilities and wastes. A jointly owned company dedicated to this purpose, SVAFO, was formed in 1992. SVAFO’s responsibilities include decommissioning the Studsvik reactors, whereas Ågesta’s licence-holder is the state-owned utility Vattenfall and it is responsible for its decommissioning.

Spent fuel from Sweden’s early reactors is in different locations. Most of the R1 fuel, which was metallic uranium, has been reprocessed in the UK. The R2/R2-0 fuel has been returned to the USA. Fuel assemblies from Ågesta are stored in Sweden’s central interim storage facility (Clab) in Oskarshamn, along with spent fuel from the country’s full-scale reactors. All fuel in Oskarshamn will eventually be encapsulated and transported to a planned deep geological repository in Forsmark. The majority of low- and intermediate-level waste from R2/R2-0 and Ågesta will also be sent to Forsmark, but disposal will be in the existing shallow repository for short-lived waste (SFR) after it has been expanded to accommodate decommissioning waste.

The Risø research reactors

Between 1957 and 1960, three research reactors of varied types and sizes went into service on the Risø site in Denmark. The last of the three, Danish Reactor (DR) 1, was taken out of operation in 2001.

Danish Decommissioning (DD) — a state agency for decommissioning and waste management — was formed in 2003. Dismantling began at DR 1 the following year. After removing the reactor and other radiological inventory, the building was released from regulatory control in 2006. The building lease has been transferred to the Danish Technological University, and the building is now used for research on large vanadium batteries.

DR 2 was dismantled in 2006/7 but the building remains in use for handling waste from the decommissioning of DR 3 and an adjacent hot cell facility.

The internal parts of DR 3 have been removed and the next step is wire cutting of the biological shield. Dismantling of DR 3 is scheduled for completion in 2022, after which clearance measurements will be performed and the final reports written. Once decommissioning is complete, the plan is to release both the DR 2 and DR 3 buildings for unrestricted use.

As decommissioning of the Risø reactors nears completion, valuable experience has been gained. Lene Elmegaard, DD’s communications advisor, says: “The majority of decommissioning staff should be ‘from the outside’ — not the same people that operated the reactors. KISS (‘keep it simple, stupid’): don’t turn a decommissioning project into a major R&D project, but aim at using industry standards, such as tools and machinery used in conventional construction or demolition projects. And, finally, do not have other types of work going on in the same building where decommissioning work is done.”

Most of the Danish spent fuel has been repatriated to the USA, except DR 1 fuel and a small amount that remains on site from experiments involving spent fuel. Denmark is seeking an international solution for this waste but a domestic option is also considered.

Low- and intermediate-level waste remains in on-site storage, in four main locations.

In the next few years, DD will construct a new waste storage facility that has capacity to store Risø’s entire radiological waste inventory for a period of up to 50 years. In the meantime, DD will pursue a disposal solution for low- and intermediate-level waste. A thorough political process, involving municipalities and other relevant stakeholders, will be initiated later this year. The aim is to find two sites in willing communities, and to conduct geological surveys to determine whether they are suitable for hosting a deep repository for the entire inventory stored at Risø. By 2073, a permanent solution for Denmark’s radioactive waste has to be in place.

Talking about the site’s long-term prospect, Lene Elmegaard says: “Risø is a beautiful peninsula that has been closed off to the public since the late 1950s. By decommissioning the current nuclear facilities and gathering radioactive waste into one storage facility, we hope to open up parts of the site for public access. We also plan to build a visitor centre on radioactive waste, on both its history and the road to a permanent solution.”

Finland’s FiR 1

Located at the Aalto University campus in Otaniemi, Espoo, Finnish Reactor 1 (FiR 1) has had a wide range of uses including education, research and radiotherapy. This TRIGA Mark II reactor was licensed to operate until 2023, but it was permanently shut down in 2015 due to insufficient funding (see NEI, December 2015). Responsibility for decommissioning rests with the reactor owner and operator, VTT Technical Research Centre of Finland Ltd.

Following an environmental impact assessment, VTT submitted a licence application to decommission FiR 1 in June 2017. “In April 2019, the regulator gave a positive statement, and we anticipate that the government will grant a licence after the summer,” says Markus Airila, project manager at VTT.

The scope of FiR 1 decommissioning is to remove the radiological inventory and release the building from regulatory control. Following that, the building will be made available for other uses. VTT is renting the building, and its future use will be determined by the building owner.

Spent fuel and radioactive waste from FiR 1 are currently stored on site, and different options are explored for long-term management. The main plan for the spent fuel is to return it to the USA, under a repatriation programme. Operational and decommissioning wastes will be disposed of in Finland, in one of the two existing disposal facilities for low- and intermediate-level waste.

FiR 1 is the first reactor to undergo decommissioning in Finland and is viewed as an opportunity to practice and learn, in preparation for decommissioning the country’s nuclear power reactors. Contingent upon repatriation of the spent fuel, dismantling is scheduled to commence in 2021 and be complete in 2022.  

Author information: Kristina Gillin, Principal Consultant at Lloyd’s Register