Field Notes Wolsung Low and Intermediate Level Waste Repository at Gyeongju, South Korea

A national plan for radioactive waste management should consider all levels of radioactive waste, from low and intermediate level waste (LILW) to high level waste (HLW) and spent nuclear fuel. Stimson experts Cindy Vestergaard and Trinh Le continue their exploration underground at the repository for LILW in the Republic of Korea – Wolsung LILW Disposal Center (WLDC). The facility has a unique combination of underground silos and near-surface disposal facilities. These are their field notes.

WLDC sits in sediment-filled Gyeongju Basin on the east coast, 370 km southeast from Seoul. The area is approximately 1.1 km long by 1.8 km wide. The phase 1 underground disposal facility was completed in 2014 at 130 m below sea level and embedded in granodiorite. There are 6 silos that can hold up to 100,000 drums. The phase 2 near-surface disposal facility with a capacity of 125,000 drums has been under review due to a change in license to accommodate a 7.0-magnitude scale. The repository has an operation tunnel for unloading waste and has a construction tunnel for maintenance. On average, 32 waste drums have been placed into silos daily since 2015.

The facility is operated by the Korea Radioactive Waste Agency (KORAD), which is responsible for the safe and effective management of radioactive waste in accordance with the 2008 Radioactive Waste Management Act.

Disposal of LILW waste

How to define LILW?

LILW in Korea is classified as activity below 4000 Bq/g of alpha-emitting radionuclides with a half-life of more than 20 years and/or a heat-generating capacity less than 2 kW per cubic meter. Examples of low-level waste (LLW) are clothes, filters, and equipment used routinely at nuclear sites, such as nuclear power plants. Intermediate level waste (ILW) contains resins, chemical sludges, radioactive sources and metal fuel claddings from hospitals and research centers which have higher levels of radioactivity. The WLDC only accepts solid waste. All ILW is stored in drums which are sealed and placed in underground silos. Employees at the WLDC experience very low radiation of average 0.0112 mSv/yr which is well below the regulatory limits of average 20 mSv/yr (maximum is50 mSv/yr).

Waste Transportation

All LILW is placed in drums and transported to the Wolsung site by the Hanjin Cheong Jeong Nuri – a specially designed ship with state of art navigation and leakage prevention equipment. Each transport container has a radio-frequency identification (RFID) and each drum barcoded for tracking by a waste tracking system (WTS). The system uses GPS, RFID and barcoding to record entire transportation routes in a database, from original shipping locations to the acceptance and storage building to disposal silos in WLDC.

Waste Inspection

Initial inspections take place at nuclear power plants before the waste is shipped to KORAD. Upon arrival at the WLDC, KORAD officers conduct a 7-step inspection procedure from visual to X-ray inspections. As defined by Radioactive Waste Management Act, permanent disposal of radioactive waste in Korea means the waste is irretrievable. Since the WLDC disposes of LILW, there are no IAEA safeguards to be applied.

Korea Institute of Nuclear Safety (KINS) is the regulatory body monitoring inspections at KORAD. The repository is estimated to close by 2074 with a potential extension to 2094 due to phase 2 near-surface disposal project. After the closure, the repository will be monitored for 300 years including 100 years of particle monitor.

The LILW waste silos are back filled with crushed rock.

HLW Management Plan

As of December 2018, there were 23 NPPs in operation, 2 NPPs in shutdown, and 5 APR1400 units under construction. As defined in the Nuclear Safety Act, there are two categories of radioactive waste: LILW and HLW. The latter is currently made up of spent nuclear fuel (SNF) only. The inventory of HLW was around 16,000 MTU as of 2017 and is expected to reach 37,000 MTU by 2080. All wet storage pools for SNF are currently full. The Wolsung site –the biggest dry storage with the capacity of 499,632 bundles –reached 91% of its capacity by December 2018. In Wolsung, all dry storages will reach full capacity by 2021, creating an urgent need for action today.

According to the national plan for HLW management established at the 6th Atomic Energy Promotion Council in July 2016, a DGR will start operating around 2053. Preliminary R&D programs for SNF disposal started in 1997 with the construction of the KAERI’s Underground Research Tunnel (KURT) in 2007. According to KAERI, a conceptual geological repository for Korea direct disposal system of SNF generated from PWRs and PHWRs is based on the Swedish KBS-3 design at 500 m underground in a granite bedrock. This reference concept includes a multiple barrier system/defense-in-depth, including embedding SNF in bentonite blocks. An alternative disposal system for HLW is the deep borehole disposal (DBD). These disposal concepts are currently under study along with the 2016 national basic plan for HLW management. A revised version of the plan is expected in the near future.In the meantime, KAERI is developing validation technologies and studying disposal environment to show long-term safety of a geological disposal of HLW.

Public Engagement

The public plays an important role in site selection and construction of disposal facilities. In 2005, 90% of the voters approved the designation of Gyeongju as the site for low and intermediate radioactive waste disposal. In 2016, the Public Engagement Commission on Spent Nuclear Fuel (PECOS) provided the government with recommendations for a national plan on HLW management.With the new government launched in May 2017, the existing 2016 HLW management policy has been reconsidered through public engagement. In the 5-year national operation plan, the Ministry of Trade, industry and Energy (MOTIE) composed a high-level radioactive waste re-review preparation team who will report to the government the purpose and content of policy re-review process, and constituent of human resources and operation period for re-review organization. In late spring of 2019, the entirely new team was set up to propose the national plan for the spent nuclear fuel management.

The site visit to Wolsung LILW Disposal Center is part of Stimson’s “Back-end to the Future” project to learn national approaches to radioactive waste disposal. Technical and societal experiences with existing repositories for low and intermediate level waste will be valuable as a country designs and operates a future deep geological repository for high level waste and spent nuclear fuel disposal. For radioactive waste management, South Korea governmental parties will join forces in the next phase of the national R&D program starting in 2021.

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