Source term evaluation for the upgraded LEU Pakistan Research Reactor-1 under severe accidents

Evaluation of source term has been carried out for the upgraded LEU PARR-I system taken as a typical material test reactor (MTR). The modeling and simulation of release of radioactivity has been carried out by developing a Matlab based computer program which uses the ORIGEN2 code for core inventory calculations. For post 180 full-power days continuous operation, various accident scenarios, with instantaneous release of radioactivity to containment, have been considered including the startup, fuel loading, and loss-of-coolant accidents. For noble gases, iodine and for aerosols, the release rate studies have been carried out for the normal, emergency and for the isolation states of containment. The values of source term as well as that of containment retention factor show rapid increase followed by an approach towards saturation values as the exhaust rate values are increased. The isotope-dependency of the containment retention factor has been studied and the results indicate strong sensitivity for 85Kr, 137Xe, 138Xe and 138Cs towards exhaust rate values.

Research highlights▶ Evaluation of source term was done for an upgraded LEU based PARR-I system with a Matlab based computer program having ORIGEN2 code as subroutine for core inventory calculations. ▶ Various accident scenarios, with instantaneous release of radioactivity to containment, have been considered including the startup, fuel loading, and loss-of-coolant accidents. ▶ The source term and containment retention factor values show a rapid increase followed by an approach towards saturation values as the exhaust rates are increased. ▶ The isotope-dependency of the containment retention factor indicates strong sensitivity for 85Kr, 137Xe, 138Xe and 138Cs towards exhaust rate values.