Source term evaluation of two loop PWR under hypothetical severe accidents

Abstract During the severe accidents in a commercial nuclear power plant (NPP) large amount of fission products releases into the containment with the accident progression, which includes in-vessel and ex-vessel sources. In a severe accident, evaluation of the source term is demanding to alleviate the radiological hazards to public risk. Source term countermeasures to containment states are studied for two-loop 2720 MWt PWR considering TMI 2 reactor as the reference reactor. SBO, LOCA, SBLOCA and Feedwater accidents are selected as the typical accidents initiating severe accidents. For post 1100 reactor operation days, the core inventory is calculated under core design constrains. A MATLAB program is developed for modeling and simulation of release of radioactivity that use core inventory. Runge–Kutta method and Simpson Rule have been implemented for numerical simulation. Assuming in-vessel and instantaneous release of radioactivity into the containment, simulation outcomes are verified for noble gasses. For noble gasses, iodine, cesium, and for Aerosols, the release rates are studied in normal, emergency and isolation state of containment. The source term value shows rapid increase followed by an approach towards saturation as the exhaust rate value increases. The radioisotope’s dependency on exhaust rate and containment retention factor (CRF) is also studied.

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