US-based Holtec International’s Global Site Services Unit, with support from Holtec Do Brasil has transferred used fuel from unit 2 of Brazil’s Angra NPP into a HI-STORM FW dry storage overpacks. Angra NPP has two operating pressurised water reactors (PWRs) – the 640 MWe Angra 1, supplied by US Westinghouse Electric Company, which was connected to the grid in 1985 and the 1,350 MWe Angra 2, supplied by Siemens, which began operation in 2001.
The loading campaign at unit 2, which involved placing 480 used nuclear fuel assemblies into 15 HI-STORM FW dry storage casks, was completed ahead of schedule and without injuries or human performance errors during completion of this project.
During this campaign, the Holtec International Fuel Repair Device (FRD) technology was used to repair 125 damaged used fuel assemblies. The FRD technology renders a damaged fuel assembly that cannot be handled by normal means into one that can be handled in a normal manner using the plant’s existing fuel handling tooling.
Certain types of PWR fuel assemblies suffer from top nozzle separation issues caused by intergranular stress corrosion cracking damage. This makes them structurally-incompetent to allow their handling, impeding the ability to return them to the reactor core or move them into dry storage. FRD is the only fuel repair technology available in the industry that involves no welding or introduction of any foreign material in the fuel pool. Holtec first employed the innovative FRD technology at its Indian Point Nuclear plant during the plant’s last defueling campaign about a year ago.
Under a 2017 Client-Assisted Turnkey contract, Holtec designed and built the dry storage infrastructure, which included construction of the Complementary Dry Storage Unit for Spent Fuel ISFSI pad as well as modification of the plant cask handling cranes and equipment to facilitate loading and storage of casks at Angra 1&2.
The HI-STORM system contains MPC-32ML a multi-purpose canister made of steel and concrete, which features a specially designed and licensed Metamic-HT fuel basket optimised for Angra 2 fuel. The storage facility is designed to receive fuel elements after they have been cooled in the reactor used fuel pools. The facility was constructed because the storage pools of both Angra units were reaching full capacity. It is designed to hold up to 72 modules, with the capacity to receive used fuel until 2045.
Holtec’s team will return to Angra 1 site to load 18 HI-STORM FW systems with 75 damaged fuel containers in early 2025. Angra 1 used fuel will be stored in HI-STORM FW system containing MPC-37 canisters, each storing 37 PWR spent fuel assemblies. Following this campaign, a total of 48 HI-STORM systems will be in storage at the Angra nuclear station. During previous campaigns in 2021-2022, Holtec loaded 15 casks to store used fuel from both Angra units.
