PWR Medium Break LOCA source term analysis using ASTEC code

Abstract

a b s t r a c tDuring a hypothetical severe accident in a nuclear reactor most of the radioactivity would be released from the damaged core and the broken primary circuit in the form of aerosols and chemical vapours and gases. However the effective radio-toxicity per unit release from the fuel depends both on the released mass and on the chemical form as well. The fission products release and transport in the circuit has been analysed for a Medium Break cold leg Loss Of Coolant Accident (MBLOCA) combined with the total loss of electric power supply (Station Black Out) for a reference PWR 1000 reactor using the severe accident integral code ASTECV1.3 rev2. A detailed description of the reactor model is given. Sensitivity analyses were performed in terms of break location and accumulator availability. The break location has an impact on the carrier gas temperature and in turn on the chemical speciation of the fission products. Also retention is influenced by the different flow pathways establishing in the circuit. The accumulator availability extends the duration of the core degradation process affecting the total production of hydrogen and the cumulative released mass of low, semi and highly volatile fission products. In agreement with the ASTEC equilibrium chemistry model, the Mo/Cs (Rb) molar ratio has the most influence on the fraction of iodine which can reach the containment in the gaseous or highly volatile form. Due to the surplus of Cs, the predicted dominant iodine species to the containment are CsI and its dimers. A 3e4% of iodine which reaches the break exists in gaseous (HI) and highly volatile metal-iodides (I 2 MoO 2 , SnI 2 , SnI 4 ) species.

Research Progress on Thermal Hydraulic Characteristics of Spent Fuel Pools: A Review

“…Compared with RELAP5, MELCOR is more simplified in terms of model processing, but both programs need to be improved with regard to the accuracy of their calculation models [81,[98][99][100][101]. Moreover, TRACE [83,84], ASTEC [85,101,102], MAAP [99] and CFD [77,[89][90][91] software have gradually become the tools of accident analysis for researchers.…”

Synthesis and Characterization of Cesium Silicate to Determine Its Detailed Properties as Chemisorbed Onto Structural Materials of Light Water Reactor During Severe Accident Conditions

“…Source terms transport evaluation is an important part of Nuclear Power Plant (NPP) safety measurement, both during normal operation, accident scenarios, as well as decommissioning preparation [1]. Several codes had been developed to predict source terms inventory and their transport behavior [2][3][4][5][6]. However, most of the currently available codes are overestimated and could not catch several physical events, i.e., late-release phenomena due to the chemisorption [7].…”