A key issue in the analysis of Large Break Loss of Coolant Accident (LB LOCA) in Pressurized Water Reactors (PWR) is the prediction of Peak Cladding Temperature (PCT). PCT value is mainly connected with maximum initial core linear power and with transient cooling. Current licensing approaches impose the use of peaking factors for linear power and conservative methods for predicting reactor cooling. Adopted Best Estimate (BE) approaches allow substituting conservatism with uncertainty analysis, but limited attention is given to the possibility of decreasing peaking factors. The present activity has the objective of presenting an approach dealing with the best use of peaking factors in case of LB LOCA. This is achieved by using Thermalhydraulics (TH) - 3D Neutron Kinetics (NK) coupled tools. The origin of the performed study is a BE plus uncertainty analysis of a LB LOCA in a four-loop PWR nuclear reactor by RELAP5/mod3.2.2 gamma code stand-alone and code with internal assessment of uncertainty (CIAU) methodology. The related results are compared with results from RELAP5/mod3.2.2 gamma code coupled with PARCS v.2.7 3D NK code. The analysis demonstrates that the coupling with 3D NK code has the potential to cause a substantial decrease in PCT prediction value, thus increasing margins for Nuclear Power Plant (NPP) power operation.
Analysis of LB LOCA in PWR through TH-3D NK Coupled Code
D'AURIA, FRANCESCO SAVERIO;
2009-01-01
Abstract
A key issue in the analysis of Large Break Loss of Coolant Accident (LB LOCA) in Pressurized Water Reactors (PWR) is the prediction of Peak Cladding Temperature (PCT). PCT value is mainly connected with maximum initial core linear power and with transient cooling. Current licensing approaches impose the use of peaking factors for linear power and conservative methods for predicting reactor cooling. Adopted Best Estimate (BE) approaches allow substituting conservatism with uncertainty analysis, but limited attention is given to the possibility of decreasing peaking factors. The present activity has the objective of presenting an approach dealing with the best use of peaking factors in case of LB LOCA. This is achieved by using Thermalhydraulics (TH) - 3D Neutron Kinetics (NK) coupled tools. The origin of the performed study is a BE plus uncertainty analysis of a LB LOCA in a four-loop PWR nuclear reactor by RELAP5/mod3.2.2 gamma code stand-alone and code with internal assessment of uncertainty (CIAU) methodology. The related results are compared with results from RELAP5/mod3.2.2 gamma code coupled with PARCS v.2.7 3D NK code. The analysis demonstrates that the coupling with 3D NK code has the potential to cause a substantial decrease in PCT prediction value, thus increasing margins for Nuclear Power Plant (NPP) power operation.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
