Disposal plans (part 1: spent fuel)

Developments in the radioactive waste sector in 2011 have included the adoption of a new radioactive waste law in Russia, a new EU directive that means countries need to draw up national radioactive waste management plans by 2015, and the publication of recommendations for the management of the USA’s used nuclear fuel from the US Blue Ribbon Commission on America’s Nuclear Future.

More than 230,000 tons of spent (or used) nuclear fuel had accumulated worldwide by the end of 2010. Of this, the majority was in either wet or dry storage facilities, while around a third had been reprocessed. By 2020, when most of the presently operated nuclear power reactors will be nearing the end of their licensed operating lives, the International Atomic Energy Agency estimates that total quantity of spent fuel generated will be approximately 445,000 tHM (IAEA-TECDOC-1587, 2008).

The long-term strategy for management of spent nuclear fuel varies from country to country. It depends on the country’s attitude to reprocessing (see part 2). There is currently no operating civil geological disposal facility for spent nuclear fuel anywhere in the world (see part 3). However, plans in some countries (for example, Sweden and Finland) are well- advanced and target dates for repository operation before 2030 are looking possible.

There are a range of different scenarios for interim storage of spent fuel, including: individual storage facilities at each nuclear power plant site; a single facility at one site dedicated to several NPPs, or an off-site interim storage facility for several stations.

Most of the radioactivity in a nuclear power plant is in its fuel. Spent nuclear fuel is extremely toxic and extremely concentrated. The United States’s 104 operating reactors produce between 2000 and 2400 tU of spent nuclear fuel each year, compared with 1150 tU in France (58 reactors) and 350 tU/year in China (14 operating reactors).

Although less radioactive, low- and intermediate-level waste (L/ILW) is far more voluminous than spent fuel. The IAEA estimates that the generation of electricity from a typical 1000 MWe nuclear power station produces approximately 300 m3 of low- and intermediate-level waste per year and some 30 tonnes of high-level solid packed waste per year. Nuclear power generation facilities produce about 200,000 m3 of L/ILW and 10,000 m3 of HLW (including spent fuel designated as waste) each year worldwide.?The graphs (right) show the principal sources of high-, medium-, low- and very low-level waste in 2010, for nuclear countries (excluding Russia, India and China), in volume terms, according to IAEA?NWMD.

Nuclear countries can be divided into those that do, and those that do not have operational L/ILW repositories (see part 4).

Spent fuel

Pools remain the dominant form for initial cooling of spent fuel at most operating reactor sites today. They are also used for centralized long-term interim storage in some countries (Belgium, Bulgaria, Russia, Sweden and Switzerland) and are often coupled to reprocessing facilities (La Hague in France, Rokkasho in Japan and Mayak in Russia).

Pools circulate water that is filtered and cooled. Over several years, the fuel assembly temperature drops as the activity produced by short-lived fission products drops due to radioactive decay.

Spent fuel is typically stored in pools at the reactor sites for at least five years before being sent for reprocessing or to interim storage, but can remain there for decades (as in the USA).

Generally speaking, dry storage units use natural ventilation to cool spent fuel that has been placed in metal and/or concrete containers. Dry storage can be expensive, so re-racking of spent fuel pools by installing new grids to increase storage density is widely carried out, but requires addition of neutron poisons to mitigate the risk of recriticality.

Reactor spent fuel pools were not designed for long-term storage; an issue that the Fukushima accident recently highlighted. A number of improvements to spent fuel pool instrumentation and cooling capability have already been proposed in response to Fukushima. The US regulator’s Fukushima near term task force (NTTF) said that installing spent fuel pool instrumentation that can withstand design-basis natural phenomena for key parameters should be carried out ‘without unnecessary delay,’ and proposed issuing a new rule on spent fuel pool cooling water makeup capability in 2015. The NTTF also said that the transfer of spent fuel to dry cask storage was an issue ‘worthy of further consideration’ before July 2012.

Onsite SFP

Brazil, Finland, Pakistan, Slovakia, Slovenia and Taiwan currently use pool storage only. In most cases, however, additional capacity will be needed in future.

In Brazil, the spent fuel pool storage capacity at Angra 1 (2252 assemblies) is sufficient to accommodate all the fuel generated over the lifetime of the unit; it is currently around one-third full. Storage space at Angra 2 is only enough for about 15 years of operation so an additional store will be needed in the medium term. Construction of a wet storage facility for Angra 1-3 is foreseen and an offsite dry storage facility is also being considered.

Spent nuclear fuel from Finland’s four operating reactors is currently stored in interim pool storage on site. Storage capacity at Loviisa is sufficient until the end of the plant’s operating life, but will need to be expanded at Olkiluoto by 2014. In late 2010, TVO awarded a contract for the construction of three new storage pools at the Olkiluoto site to a Finnish consortium. They are expected to begin operation in 2013.

Re-racking of the spent fuel pools at Slovenia’s Krsko carried out in 2003 means that storage capacity is sufficient for the planned lifetime operation (until 2023). Following this, the long-term strategy foresees a move from pool to dry storage casks between 2024 and 2030, with transfer to a geological repository from 2065.

The capacity of the fuel storage bay at Pakistan’s Karachi nuclear power plant (KANUPP), in particular, is nearing capacity and will not be sufficient to store the fuel from the extended operation of the plant to 2019. To handle the storage problems, the plant has carried out spent fuel pool re-racking and plans to construct a spent fuel dry storage facility within the plant premises. An allocation of Rs 70 million ($700,000) was made towards the dry storage project in FY2011-2012, according to the Pakistan Atomic Energy Commission. At the Chasma site the spent fuel storage facility can meet requirements for 15 years of operation at both nuclear power plants. A new facility is planned for Chasma 1 by 2015, and one will be built for Chasma 2 after eight years of plant operation, near 2020.

Most of the spent fuel pools in Taiwan are almost full. As of March, 3321 tHM of spent fuel was in storage at Chinshan, Kuosheng and Maanshan, with pools at 91%, 88% and 56% capacity, respectively. The operator of the three plants, Taiwan Power Company, is planning to build dry stores at the two of the three sites, with operation expected in 2013 at Chinshan and 2016 at Kuosheng, according to the Taiwanese regulator. The new facility at the Chinshan nuclear power station will provide dry storage for 1366 spent fuel assemblies. When combined with the pool capacity this will be sufficient to store all fuel generated during the 40-year licensed operation of the station. The facility, being built by the Institute of Nuclear Energy Research (INER), will use concrete storage casks (INER-HPS) that are based on technology transfer from US firm NAC International. A new facility at Kuosheng will comprise 27 MAGNASTOR casks, capable of storing 87 spent fuel assemblies each. Safety studies are currently underway and Taipower is expected to submit an application for a construction licence for the Kuosheng independent spent fuel storage installation (ISFSI) to the Taiwanese nuclear regulator this year.

Italy is somewhat of a unique case in that it abandoned its nuclear power programme in 1987, following the Chernobyl accident. Most of the country’s spent fuel has been sent to the UK or France for reprocessing. A small amount remains in storage pools at the Trino plant (a 260 MWe PWR) and at the Avogadro pool storage facility in Saluggia, however this is due to be shipped for reprocessing in 2012.

Onsite dry

The move towards dry storage began in the 1990s. Today, 22 countries currently have some dry spent fuel storage in operation. Recently a large centralized dry storage facility was completed in Russia and facilities are under design and/or construction in a number of other countries.

Argentina transfers the spent fuel from its Embalse nuclear power plant from spent fuel pools to dry storage in concrete silos after at least six years. Fuel from Atucha 1 is stored exclusively in the spent fuel pool, which has sufficient capacity to March 2015. A modular facility for dry storage at Atucha is under design and construction, with operation planned for 2014.

Armenia has two VVER-440 reactors at the Metsamor site (one operating; one undergoing decommissioning). In the past, spent fuel was sent for reprocessing in the former Soviet Union. Dry storage (based on Areva’s NUHOMS technology) was installed at the Metsamor site in 1998.

In Belgium, spent fuel is initially stored in reactor spent fuel pools at the country’s two nuclear power plant sites. Then, one of two options is adopted: dry storage in metallic dual-purpose (transport/storage) casks has been underway at Doel since 1995 and a centralized storage pond at Tihange has been in operation since 1997.

Spent fuel from Hungary’s Paks NPP is currently stored in reactor cooling ponds or in an interim fuel storage facility (vaults), 5km south of the reactor site. As of the end of 2010, just over a fifth of Hungary’s spent fuel (1800 assemblies) was in pool storage with the remainder (6500 assemblies) in the interim store. In the past, Hungary has also sent fuel to Russia for reprocessing.

Spent fuel arising from South Africa’s Koeberg plant is currently stored in used fuel pools on the site as well as in purpose-designed storage casks. The Koeberg site has enough storage capacity for the used fuel that will be generated during the current operational lifetime of the two-unit power station.

Romania initially stores the spent fuel from its natural uranium-fuelled Cernavoda reactors in spent fuel pools and then transfers it to a dry spent fuel storage facility also located on the site. The facility uses AECL’s air-cooled modular storage technology (MACSTOR).

All operating US reactors store spent fuel on site in spent fuel pools. However, with pools nearing capacity, many operators have begun transferring the oldest spent fuel to on-site air-cooled storage casks. Today all but eleven of the 65 nuclear sites have built or applied to build on-site ISFSIs, according to the US regulator (www.nrc.gov/waste/spent-fuel-storage/locations.pdf).

By the end of 2010, the US Department of Energy estimated that there was around 65,000 tHM of spent fuel in storage, with just under a quarter in dry casks. The US spent fuel inventory will be double that by 2055, assuming 20-year life extensions for each reactor and could reach 210,000 tHM by 2050 if there is a significant expansion of nuclear power in the USA, based on DOE projections.

One of the recommendations for the Blue Ribbon Commission (BRC) was that the US should begin prompt efforts to develop one or more consolidated storage facilities as well as a deep geological repository for high-level waste. Currently US legislation (the Nuclear Waste Policy Act) allows the government to construct one consolidated storage facility with limited capacity, but only after the construction of a nuclear waste repository has been licensed. The commission recommended that this act be modified to allow for a consent-based process to locate, licence, and construct multiple storage facilities with adequate capacity when needed and to clarify that nuclear waste fee payments can be used for this purpose.

Centralized

French and Dutch fuel that is waiting reprocessing is stored in spent fuel pools at the reactor sites for at least three years before being shipped to Areva’s La Hague plant in France for further pool storage and subsequent reprocessing. Four storage pools at the La Hague plant have a total capacity of 14,000 tU and have been in operation for the last two decades.

French law requires formal agreements for the return of high-level waste to be in place before it can accept any spent fuel for reprocessing. This led to the suspension of shipments from the Borssele plant in the Netherlands between 2006 and mid-2011, which meant the fuel pools at the Dutch plant neared capacity, until governmental agreements were put in place.

Russia has a large centralized spent fuel pool at its Mayak reprocessing plant, which accepts fuel from VVER-440 reactors in Russia, Ukraine and Bulgaria for reprocessing. In the past Russia has also reprocessed fuel from Armenia, Finland, Hungary and Germany.

Ukraine is an interesting case in that it continues to ship spent fuel from most of its nuclear power plants to Russia for storage (Khmelnitsky & South Ukraine) or reprocessing (Rivne 1-4). Only one Ukrainian NPP— Zaporizhzhya—currently has an on-site spent fuel storage facility, which was licensed for operation in 2004.

Ukraine plans to build a centralized dry spent fuel storage facility for the other units based on the technology used at the Zaporizhzhya site. In 2009, Holtec International (USA) won the tender to build the facility. Work to design the storage facility (casks) is now underway and safety cases are under development. After completion of the technical design, modeling will be started and prototype casks will be manufactured.

After storage in reactor spent fuel pools, fuel from Slovakian reactors is transported to an interim wet storage facility in Bohunice where it will be stored for at least 50 years. The facility was extensively refurbished during 1997-2000 and its capacity was increased from 4030 to over 14,000 fuel assemblies (approx 1700 tU). At the end of 2010 the IFSF was at 70% capacity. Its capacity is expected to be sufficient until 2021. Beyond that, the construction of a dry storage facility is anticipated, and ultimately geological disposal.

Mix of wet and dry

Storage of spent fuel in Japan is predominantly wet, although there are some dry storage facilities at the Tokai and Fukushima Daiichi nuclear power plants. At the end of March 2011, 16,714 tHM of spent fuel was in storage at nuclear power plant sites in the Japan or at the Rokkasho reprocessing facility, which was at 96% of its 3000-tonne capacity.

An interim dry storage facility is currently being built at Mutsu City in Aomori prefecture by a TEPCO-JAPCO joint venture: the Recyclable-Fuel Storage Company. Construction of the 3000 tU facility resumed in March 2012, according to the Japan Times, after being suspended in the wake of the Fukushima accident. Operation is slated to begin in October 2013. A second facility was envisaged, bringing the total capacity to 5000 tU, however it remains to be seen if this will go ahead following Fukushima.

Switzerland, too, has both wet and dry interim storage facilities. An interim wet storage facility at Gösgen nuclear site has the capacity for 1000 spent fuel assemblies. The Beznau site also hosts a dry storage facility (Zwibez) for spent fuel and high-level waste, which has been in operation since 2008. Moreover, Zwilag, a company owned by the four Swiss nuclear utilities operates a central storage facility in Würenlingen. It has capacity for 200 casks containing spent fuel or vitrified waste; 11,000m3 of intermediate level waste and 27,000m3 of waste arising from NPP decommissioning.

The Canadian natural uranium used fuel inventory is stored at six sites across four provinces. As of June 2011, around two-thirds is in wet storage, with the remainder in dry storage. Each nuclear power plant in Canada has enough storage space to store all the spent fuel produced during its operating life.

Mainland China also stores most of its spent fuel in pools on site. While capacity at most sites is sufficient until the mid 2020s, the Qinshan and Daya Bay sites are facing the biggest fuel storage challenges. As a result, a dry storage facility is now in operation at the Qinshan III site, and since 2003 fuel from Daya Bay nuclear power plant is shipped to the pilot reprocessing plant in Gansu Province for interim storage. The spent fuel pool storage facility in Gansu Province can store up to 500 tonnes of fuel from commercial reactors and 50t from research reactors.

At the end of 2009, some 10,761 tU of spent nuclear fuel was in storage at the four Korean nuclear power plant sites, equal to around 80% of capacity. Pressurized water reactor fuel is stored in spent fuel pools, while dry storage is used for the Candu fuel. Spent fuel will continue to be stored on site until interim storage facilities are constructed by 2016.

This article was first published in the June 2012 issue of Nuclear Engineering International