Deterministic assessment of reactor pressure vessel integrity under pressurised thermal shock

Numerical investigations were carried out to assess the integrity of reacto r pressure vessels under pressurised thermal shock (PTS). The 4-loop reacto r pressure vessel with cladding was subjected to thermo-mechanical loading owing to loss of coolant accident. The loss of coolant accident correspondi ng to small break as well as hot leg breaks were considered separately, whi ch led to axisymmetric and asymmetric thermal loading conditions respective ly. Three different crack configurations, 360 degrees circumferential part through, circumferential semielliptical surface and circumferential semi-el liptical under-clad cracks, were postulated in the reactor pressure vessel. Finite element method was used as a tool for transient thermo-elastic anal ysis. The various fracture parameters such as crack mouth opening displacem ent (CMOD), stress intensity factor (SIF) nil ductility transition temperat ure (RTNDT) etc. were computed for each crack configuration subjected to va rious type of loading conditions. Finally for each crack a fracture assessm ent was performed concerning crack initiation based on the fracture toughne ss curve. The required material RTNDT was evaluated to avoid crack initiati on. (C) 1999 Elsevier Science Ltd. All rights reserved.