Subcriticality of Philippine Research Reactor-1 fuel storage facility
The Philippine Research Reactor-1 (PRR-1) storage facility contains enough nuclear material for which a criticality accident is credible. To meet the objectives of nuclear criticality safety, safety criteria should be based on the value of the effective multiplication factor (keff) where keff < 1 means that the system is subcritical and the neutron fission chain reaction cannot be maintained. We calculated the keff of the storage tank containing the 113 TRIGA fuel rods and other core components of PRR-1 using MCNP5, a Monte Carlo transport code. With a criticality calculation control of 1,000 active cycles with nominally 104 neutrons per cycle, our results show a keff of 0.61403 ± 0.00059 at the 99% confidence level. It was found that the system has a large safety margin of
–62.858% Δk/k due to the design of the storage rack as a passive engineered safety measure that restricts the dimension and shape of the system to a favorable geometry. The results of our study indicate that the current PRR-1 fuel storage facility is criticality safe.