Safety Analysis Code for Supercritical Pressure Condition

1 Safety Analysis Code for Supercritical Pressure Condition 

The plant transient analysis code SPRAT-DOWN, described in Sect. 4.2, is extended for the analyses of abnormal transients and accidents. The calculation model is shown in Fig. 6.12. The models of the equipment, i.e., the AFS, SRV, MSIVs, and turbine bypass valves, are added for safety analyses. A hot chaimel, where the linear heat generation late and maximum cladding surface temperature are the highest in the core, is modeled as well as the average channel in order to calculate the highest values of cladding temperature and pellet enthalpy. The flow chart is shown in Fig. 6.13. 

The coolant entering the RPV is divided into the downcomer flow (70%) and the water rod flow (30%) at the normal operating conditions. The pressure drops of those two paths are balanced by means of orifices. At abnormal conditions, flow-redistribution would occur between those two paths due to the loss of pressure balance. The flow-redistribution is considered along with calculation of the pressure drop balance and momentum conservation. The pressure drops of each flow path are calculated as follows. 

SPRAT-DOWN Stea(dy-state at supercritical pressure Abnormal transients or accidents, mclnding small LOCA without depressurization 

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