Design of serpentine cask for Ghana research reactor-1 spent nuclear fuel

• Temporary Spent fuel casks have been designed to manage the irradiated fuel.
• The main component of the cask is serpentine which is abundant in Ghana.
• Keff of 0.01717 ± 0.00001 was recorded for the most effective cask design.
• The casks have radii of 60 cm hence making it relatively portable but effective.
• The average dose rate of the cask is 3.26E-01 ± 0.0007 Gy/h.

Ghana Research Reactor-1 (GHARR-1) core is to be converted from HEU fuel to LEU fuel in the near future; a storage cask will be needed to store the HEU fuel. Notwithstanding the core conversion process, it is also important for the facility to have a storage cask available when the spent fuel finally reaches its end of cycle to temporarily store the fuel until permanent storage is provided. WIMS-ANL (Deen et al, 2000), REBUS (Olson, 2001), ORIGEN2 (Croff, 1980) and MCNP5 (Briesmeister, 2000) codes were used to design six casks. WIMS-ANL was used in generating cross sections for the REBUS code which was used in the burnup calculations. The REBUS code was used to estimate the core life time. An estimated core life of approximately 750 full-power-equivalent-days was obtained for reactor operation of 2 h a day, 4 days a week and 48 weeks in a year. Serpentine concrete of density 5.1385 g/cm3 and thickness 21.94 cm was used as the main gamma shield. Other composite of the concrete shield which were used were Lead (two thick layers of 1.91 cm and 2.50 cm respectively), boron carbide (two layers of 2.00 cm thick each), resin (2.00 cm thick), stainless steel (two thick layers of 2.63 cm and 1.17 cm respectively) and aluminium (2.00 cm thick). Serpentine was chosen as the main material because of its availability in certain parts of Ghana and hence making it cost effective. The casks were designed to be cooled by natural circulation and to have radii of approximately 60.00 cm and a height of 75.46 cm hence making them relatively portable (in all six casks with different material and material arrangement were investigated). The results obtained for the cask with the most suitable shielding capability (Cask F) is presented in this paper. Effective multiplication factor of 0.01717 ± 0.00001 was recorded for the spent fuel cask design labeled Cask F. This showed that the design was capable of keeping the spent fuel sub critical. The dose rates were also reduced from the source to the surface of the casks for all six designs. The cask, had the best neutron and gamma shielding effect (from 1010 to 105 n cm2 s−1 for neutron and 10−1 Gy/h for gamma), therefore, the cask is recommended.