Methodological features to justify nuclear safety for irradiated fuel rods temporary placement in hot cells

Methodological features to justify nuclear safety for irradiated fuel rods temporary placement in hot cells.

Akimov A. V., Malkov A. P., Samokhvalov R. V., Fraaz E. S.

The article presents methodological features of nuclear safety analysis in the handling of fuel elements, their fragments, as well as waste after work with them (chips, powder, trimmings) inside radiation-protective chambers. Fuel elements, their fragments and waste after work with them can be placed in various packages (canisters, containers) in specially designated places (racks, whatnots and countertops of chambers). Nuclear safety analysis was carried out in accordance with the requirements of the main regulatory documents in the field of nuclear safety. To determine the values of the effective neutron multiplication factor, the results of calculations obtained using the MCU-RFFI/A program were used. Situations were considered both for normal storage conditions for packages with fuel elements (air environment inside and outside the packages), and possible emergency situations (filling the packages with water, exceeding the load rate, displacement of packages from their regular positions, spilling the contents of the packages). Based on the results of the computational analysis, the importance of taking into account the reflection of neutrons from concrete building structures (walls, floors, ceilings) is shown. The dependence of the change in the effective neutron multiplication factor in the case of water entering the chambers and equipment of different densities was determined. Based on the results of neutron-physical calculations, restrictions were determined when handling packages loaded with fuel elements inside radiation-protective chambers (permissible quantity, placement geometry and loading rate for fissile nuclides).

Keywords: nuclear safety, storage of irradiated nuclear fuel, nuclear fissile materials, fuel rod, effective neutron multiplication factor, MCU-RFFI/A software, hot cells, neutronic calculations.

Article language: Russian. Pp. 28–37. DOI: 10.26277/SECNRS.2022.105.3.003.