RELAP5 model of a small break LOCA in GE's simplified boiling water reactor Conference Paper uri icon


  • The thermal hydraulic simulation code RELAP5/MOD3.1.1 was utilized to model General Electric's Simplified Boiling Water Reactor plant. The model of the plant was subjected to a small break loss of coolant accident occurring from a guillotine shear of the vessel's 2 inch bottom drain line while operating at full power. The accident was compounded by disabling the plants isolation condenser system and as an initial condition, the loss of site power. The ability of the plant's passive safety systems to respond to this type of accident, and the code's ability to accurately predict the accidents phenomena was investigated. The overall conclusion was that the modeled plant maintained all relevant safety parameters within specifications supplied by General Electric (GE) in their Standard Safety Analysis Report (SAR) for the term of investigation (15,500 real time seconds). While no safety related parameters were exceeded, certain trends appearing near the end of the calculation suggest the need for further investigation. Both containment temperature and pressure were increasing when the transient was terminated. The RELAP5 code was able to simulate a representative model of the plant. Calculated steady state parameters for power, flow rates, recirculation ratio, and mass balance were within 1% of those specified in the SAR. However the ability of the code to accurately model low flow, condensation heat transfer, in the presence of noncondensable gases should be verified. It is concluded that the simulation's results seem to pass an intuitive engineering inspection. That is to say, flow and heat transfer data calculated by the RELAP5 code reflect expected values and relational interactions are maintained, but that no quantitative significance could be justified. The uniqueness of the plant's design and the interactive nature of the transient, suggest additional experimental data from test facilities is needed to validate the calculations.

author list (cited authors)

  • Faust, C. R., & Hassan, Y. A.

publication date

  • December 1995