MHI Delivers Dry Cask to Ikata NPPs

On January 17, Japan’s Mitsubishi Heavy Industries (MHI) announced that it had completed manufacturing and delivering two dry casks for the transportation and storage of spent fuel, part of an order for 15 casks. The casks were delivered to the Ikata Nuclear Power Plants (NPPs), operated by the Shikoku Electric Power Co., which is currently constructing a dry storage facility at the site, with operation slated to begin around July of this year.

With the progressive resumption of operation of those domestic NPPs meeting the country’s new regulatory standards, electric power utilities in Japan are considering storing their spent nuclear fuel at various NPPs until eventually transporting it to the Rokkasho Reprocessing Plant for longer-term storage.

Shikoku Electric Power’s Ikata-3 is currently in service. In September 2020, the power company obtained approval for a reactor installation modification to set up a dry storage facility (500t) at the site, with installation work currently underway, as mentioned above.

Following the giant earthquake that struck Japan on March 11, 2011 (known officially here as the Great East Japan Earthquake), the robustness of the dry-cask storage program being advanced by domestic electric power firms was confirmed, including the one at Fukushima Daiichi. The Nuclear Regulation Authority (NRA) of Japan has thus recommended the program’s widespread use.

The dry casks delivered by MHI are of the MSF-32P model, measuring 2.6m in diameter and 5.2m high, and weighing a total of approximately 120t. They will be used to store 32 spent fuel assemblies from Ikata-1 and -2, both of which have already been decommissioned.

According to Shikoku Electric Power’s latest announcement, it carried out a series of safety verification tests on a full-scale dry cask—including rolling it down a 9-m slope—and confirmed its safety. Long-term material verification and soundness tests similarly demonstrated that the four safety functions of containment, criticality prevention, shielding, and heat removal could be sustained for 60 years.

Going forward, MHI will continue to manufacture the remaining 13 dry casks for the Ikata NPPs one by one. Thanks to the success of the recent delivery, the firm plans to establish a dedicated factory to assemble the casks, so as to automate the manufacturing and inspection processes. MHI is thus leveraging its expertise in manufacturing nuclear equipment for pressurized water reactors (PWRs) to establish a mass-production system.

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