Orano USA has completed the first loading of used nuclear fuel into the first three upper modules of the two-tiered NUHOMS MATRIXTM horizontal dry storage system installed at the Wolf Creek Nuclear Operating Corporation site in Kansas. Wolf Creek is a single-unit 1200 MWe (net) pressurised water reactor. Orano and Wolf Creek collaborated to complete the three loadings, which were achieved with no safety events.

In 2018, Wolf Creek Nuclear Operating Company contracted Orano TN – a subsidiary of Orano USA – to design, construct and commission an interim used fuel storage facility, and to transfer used fuel from the plant's storage pool to the new dry storage facility.

Over three weeks, three consecutive Extended Optimised Storage (EOS) 37PTH canisters were each filled with 37 used nuclear fuel assemblies in the reactor’s used fuel pool before being transferred into the upper modules of the onsite MATRIX dry storage system. The canisters join the five others loaded into the lower tier in 2022, filling eight of the available 11 modules in the system. Future loading campaigns will be conducted after expanding the MATRIX system with additional modules beginning in Spring 2024.

Orano said that, compared to other dry storage technologies, the compact two-tiered horizontal MATRIX design reduces the footprint requirements for an Independent Spent Fuel Storage Installation (ISFSI) by as much as 45% to store the same amount of used fuel. An ISFSI is a US Nuclear Regulatory Commission-licensed facility for the storage of used fuel that has been allowed to cool for several years in a reactor's used fuel pool before being transferred to dry storage.

For extended interim used fuel storage and ageing management requirements, the MATRIX system integrates new design features and devices which enable the complete inspection of the stored canister without removing it from the module.

The universal MATRIX overpack also meets all storage requirements for shutdown and operating US reactors, including storage of high-burnup short-cooled fuel. It is also designed to accommodate used fuel storage canisters with different diameters and fuel lengths.

Before the loading campaign began, the Orano and Wolf Creek teams trained together conducting dry runs with the equipment onsite and on the full-scale MATRIX mock-up located on Orano’s TN Fabrication (TNF) facility in Kernersville, North Carolina. The TNF facility also manufactured the eight EOS 37PTH canisters for storing the used nuclear fuel.

Inlets at the bottom of each round module of the storage opening allow inspection equipment to thoroughly examine the stored canister when the module is closed. Each module also has an inspection port to aid in visual inspection of the canister.

Image: A sealed used fuel canister is moved remotely from the transfer cask into a MATRIX module (courtesy of Orano)