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The US Nuclear Regulatory Commission (NRC) has approved the design certification for a used fuel metal storage cask developed by South Korea’s Doosan Enerbility and US-based NAC International.

The Metal Storage Overpack (MSO) is intended for international applications and also for the Korea Dry Cask Storage industry as an alternative to concrete storage systems. NAC (Nuclear Assurance Corporation) in 2019 submitted an amendment application to NRC for design certification of a new MSO option for its Magnastor dry cask storage system technology.

The MSO can store up to 37 pressurised water reactor (PWR) fuel assemblies and is the first metal storage cask to have obtained NRC design certification. Doosan Enerbility says that, compared with conventional concrete storage casks, it provides robust radiation shielding and structural integrity, significantly reducing the diameter of the cask. This optimises the cask’s footprint in dry storage facilities, which allows storage of more casks.

The MSO was specifically developed taking into account the characteristics of used nuclear fuel, facility operation environments, and public demand for rigorous safety and radiation protection standards in Korea, Doosan notes. “As the safety management of the used nuclear fuels is very important during dry storage, the casks require the highest level of special technology and experience in design and fabrication.”

Jongdoo Kim, Head of Doosan Enerbility’s Nuclear Business Group, says based on the experience gained in development and licensing of the cask, “we plan to participate in used nuclear fuel dry storage projects in the domestic market and to also contribute to the future development of casks designed for permanent disposal of used nuclear fuel”. He added, “Based on our supply chain built with the leading local manufacturers, we are set to target the global nuclear cask market and will do our utmost to promote growth of the nuclear energy ecosystem and overseas exports.”

In 2015, Doosan signed a technology cooperation agreement with NAC, after which the “Doosan-DSS21,” a Korean dry storage system with the capacity to store and transport up to 21 used fuel assemblies, was developed. This was followed by the upgraded DSS24 and DSS32, with larger storage capacity, and the DPC-24 for both storage and transportation of used fuel. In 2021, Doosan also became the first Korean company to export used fuel storage casks to the USA.

NAC says the NRC approval is, "the first and most widely deployed ultra-high-capacity canister system installed at US PWR commercial nuclear power plants". To date, 211 PWR Magnastor systems have been loaded and are in service storing used fuel at operating and shutdown sites. According to NAC, the new MSO design “is adaptable to existing ancillary equipment, provides flexibility to accommodate new used fuel canister designs and other high level waste contents”. This is consistent with an advanced integrated waste management strategy, which is a core objective of NAC’s technology development efforts. Currently, other amendments are underway as we consistently remain initiative-taking in expanding Magnastor’s capabilities for readiness to meet emerging needs,” says Kent Cole, NAC President and CEO.

Image: Doosan Enerbility Vice President Cho Changyeol (left) and NAC President Kent Cole mark the design certification of the new cask (courtesy of Doosan Enerbility)

Date: Wednesday, 25 January 2023
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