Maintenance program for a safe prolonged wet storage of the nuclear spent fuel at IFIN-HH Bucharest-Magurele site

Full text: Fuel is considered as spent nuclear fuel regardless of burnup when it is discharged from the reactor core for the final time. It is then normally placed in pools for cooling and interim storage until a final disposition is made. As a result of 40 years of intense utilization of the VVR-S reactor from IFIN-HH, 223 fuel assemblies of burned fuel were produced and stored in special ponds. Some of this aluminum-clad spent fuel has been in water storage for more than 30 years and remains in pristine condition until two years ago. Corrosion concerns on the spent fuel have been minimal over the years of fuel storage. The water in these basins is currently being maintained but no special issues were applied to improve water quality. Some pitting was reported on aluminum outer surface of some fuel assemblies, but this was attributed to material defects and fabrication concern. An intensive effort was made at our department to understand the corrosion problems and to be able to improve the basin storage conditions for extended storage requirements (in accordance with the demands). A complex maintenance program was formalized but due to lack of funds it was delayed to be carried out. Even so, despite financial problems some parts of this program were implemented to improve the water quality. Since March 2003 a completion of the initial programme was possible due to US financial assistance to make it feasible. As part of the contract between National Atomic Energy Agency (ANEA) and Department of Energy (DOE), a scheduled operational maintenance program was issued. This program contains: 1. Baseline characterization and storage life prediction; 2. Formalize water characterization program; 3. Formalize corrosion surveillance program; 4. Visual examination of longest stored assemblies (EK-10 and S-36); 5. Identification and disposition of the failed fuel assemblies in Pool no. 3; 6. Vacuum silt and water change; 7. Relocate fuel from reactor cooling pond to AFR (Away from Reactor) Pool no. 1; 8. Formalize corrosion surveillance program; 9. Pool water level monitoring program; The main goal of this strategy is to ensure that the fuels are maintained in a safe stable state until the shipment to origin country becomes available. (author)