US approval for metal storage cask

19 January 2023

A metal overpack for cask storage of used nuclear fuel, jointly developed by Doosan Enerbility of South Korea and NAC International of the USA, has received design certification from the US Nuclear Regulatory Commission (NRC).

Representatives from NAC and Doosan Enerbility mark the design certification of the new cask (Image: Doosan Enerbility)

A ceremony was held to mark the design certification of the MSO-37 overpack at NAC's corporate headquarters in Atlanta, Georgia. Among those in attendance were Changyeol Cho, Vice President of Doosan Enerbility's Nuclear Business Group, and Kent Cole, President and CEO of NAC International.

The MSO was conceptualised by NAC and Doosan Enerbility for international applications and applies to the Korea Dry Cask Storage industry as an alternative to concrete storage systems. The Doosan Enerbility and NAC teams cooperatively designed and engineered the solution; and, in December 2019, NAC filed an amendment application with the NRC for design certification.

The MSO (Metal Storage Overpack) is used with transportable canisters that can store up to 37 pressurised water reactor (PWR) fuel assemblies. According to Doosan Enerbility, it is the world's first metal overpack to have obtained design certification from the NRC.

NAC said the NRC approval is for a new MSO option for its Magnastor dry cask storage system technology, "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 safely storing used fuel at operating and shutdown sites.

"Compared with conventional concrete storage casks, this newly-developed metal overpack option provides robust radiation shielding and structural integrity, significantly reduces the diameter of the cask, thereby optimising the storage cask's footprint in dry storage facilities, which in turn allows storage of more casks in the same locality," the company said.

Doosan Enerbility said the MSO was developed taking into account "the characteristics of spent nuclear fuel, facility operation environments, and public demand for rigorous safety and radiation protection standards in Korea". 

"With the technical capabilities recently acquired from the development and licensing experience of the metal overpack, we plan to actively participate in spent nuclear fuel dry storage projects in the domestic market and to also contribute to the future development of casks designed for permanent disposal of spent nuclear fuel," said Jongdoo Kim, Head of Doosan Enerbility's Nuclear Business Group.

He added: "Based on our supply chain built with the leading local manufacturers, we are set to actively target the global nuclear cask market and will do our utmost to promote growth of the nuclear energy ecosystem and overseas exports."

In October 2015, Doosan and NAC announced the signing of a cooperation agreement for the joint development of a used nuclear fuel storage system to be deployed in Korea. 

In 2017, Doosan completed development of the DSS-21, a dry storage system that has the capacity to safely store and transport up to 21 used fuel assemblies. Since then, the DSS-24 and DSS-32 models, upgraded versions with larger storage capacities, were developed, along with the DPC-24, a cask that can be used for both storage and transporting of used fuel.

In 2021, Doosan became the first Korean company to export used fuel storage casks to the USA, supplying five sets of a vertical concrete cask to the Three Mile Island nuclear power plant in Pennsylvania.

Researched and written by World Nuclear News