Korean repository realised22 July 2014 Caroline Peachey
Thirty-six years after South Korea’s first nuclear power plant started-up, the country’s low- and intermediate-level waste repository has been completed and is set to begin accepting waste later this year.
Since its first nuclear power plant, Kori 1, began operation in 1978, Korea has successfully built up a strong domestic nuclear capability and nuclear power has become a pillar of the country's energy policy.
Today, state-owned Korea Hydro & Nuclear Power (KHNP) operates a fleet of 23 reactors (21.7 GW net), which supply around 30% of the county's electricity needs. The country has also committed to nuclear power as part of its future energy mix and energy plans envisage over 30 units providing almost 50% of Korea's electricity by 2022. Five reactors totalling 6.8 GW are under construction at existing sites and six more have been announced.
But in addition to the large amounts of power generated (138.8 TWh during 2013), Korea's large nuclear power programme has produced a significant amount of radioactive waste and spent nuclear fuel and the amount of waste is steadily growing. The 23 units in operation today and the 11 planned are together expected to generate almost a million drums of radioactive waste from operations and decommissioning.
Until recently there has been no repository for radioactive waste in the country. The start-up of the first underground phase of the Korean repository for low and intermediate level waste (LILW) is expected in the October-December 2014 period. The project has been almost three decades in the making and it comes at a time when plant-based storage for LILW is nearly full.
HLW and LILW
Under Korea's Nuclear Safety Act, there are two categories of radioactive waste: high-level (HLW), and low- and intermediate-level (LILW).
HLW is officially defined as a radioactive material with a specific activity = 4000 Bq/g of a-emitting radionuclides with a half-life of more than 20 years and a heat-generating capacity of 2 kW/m3 or greater. Given that there is no reprocessing in South Korea, only spent nuclear fuel arising from nuclear power operations is in the HLW category. Korea produces around 700t of spent nuclear fuel annually, which is stored at the nuclear power plant in either wet or dry storage facilities.
However plant storage is expected to run out of space beyond 2016 and an interim storage facility will be required before a national decision on spent fuel management policy is taken. In the short-term spent fuel pools are being re-racked and spent fuel is being shipped to other plants where there is storage space.
Korea Radioactive Waste Agency (KORAD) is responsible for interim storage and management of spent fuel (before 2013 it was known as Korea Radioactive Waste Management Corporation). KORAD also supports a 15-member Public Engagement Commission on Spent Nuclear Fuel Management, whose main purpose is to draw up a consent-based national plan for spent fuel management.
Strictly speaking, materials other than HLW belong to the LILW category, but in December 2013 the Nuclear Safety and Security Commission (NSSC) approved a draft revision of the radioactive waste classification system, which splits LILW further into very low level (VLLW), low level (LLW) and intermediate level radioactive waste (ILW). This is a response to International Atomic Energy Agency (IAEA) recommendations from 2009, which advise engineered geological disposal (hundreds of metres below ground) for ILW; engineered vault-type near-surface disposal (around 30m below ground) for LLW and trench-type near-surface disposal for VLLW.
Initial efforts to develop a repository
Korea's plans to develop a low and intermediate level waste repository were first launched in 1986, but insufficient public understanding and intense political disputes hampered the site selection process.
Finally, after a twenty-year effort, a site in Gyeongju was chosen in November 2005. It is about 370 km southeast of Seoul, adjacent to the existing Wolsong nuclear power station, and it had overwhelming support from the local population.
KORAD will be responsible for construction and operation of the Wolsong LILW Disposal Centre (WLDC), which will have a final capacity of 800,000 drums in an area of about 2,100,000 m2.
Phase 1 construction
Construction of the first phase, six underground silos with capacity for 100,000 drums, began in November 2007. The repository was originally due for completion in 2010, but the construction period was extended twice, by about 30 months in 2009 and 18 months in 2012, because of rock reinforcement and groundwater problems discovered during construction. This phase of the WLDC is due to be completed imminently (in June 2014).
The first phase of the project also included construction of surface facilities: a waste inspection and storage building, a radioactive waste treatment building, main control centre and equipment maintenance shop. These facilities have been completed and waste drums are being stored in the waste inspection & interim storage building, awaiting final disposal in the vertical silos.
The six silos are 80-130 metres below sea level, with a diameter of 25m and height of around 50m. The underground facility comprises a construction tunnel (1950m), operation tunnel (1415m), access shaft (207m) and the silos themselves. Excavation of the disposal silos started in February 2011 and was completed in November 2013.
The 100,000 drums in the six silos (16,700 in each) will contain 35,200 m3 of waste. For loading efficiency the 200 litre waste drums are placed inside 16-pack (4×4) disposal containers, which are handled with remote equipment such as a crane.
Since completion of the silos, work has focused on installation of the silo cranes for disposal of the waste, installation of fire protection, radiation monitoring and ventilation systems.
Phase 2: a near-surface facility
Plans for a second phase of the repository - a 71,014 m2 near-surface disposal facility with capacity for 125,000 waste drums - were launched in 2011. KEPCO Engineering & Construction has been selected to design this phase following a competitive tendering process, beating Hyundai Engineering and Daewoo Engineering & Construction in the final stage of bidding. The near-surface disposal facility is expected to be finished by the end of 2016, KEPCO says.
KEPCO E&C says the Wolsong disposal centre will be the world's first repository to host both silo-type and near-surface radioactive waste repositories on the same site, which will help improve the efficiency of radwaste storage. A trench disposal facility is also planned for VLLW, the largest volumes of which will be produced when the nuclear plants are decommissioned. The final disposal capacity will be 800,000 drums, after stepwise expansion.
KORAD says on its website that its goal is to have a storage capacity of 350,000 drums at the LILW repository by 2020.
Caroline Peachey is assistant editor of Nuclear Engineering International