Lessons learned from the plant-specific pressurized thermal shock integrity analysis on an embrittled reactor pressure vessel

The reference temperature of pressurized thermal shock (PTS) of the reactor pressure vessel (RPV) for the oldest pressurized water reactor in Korea ha d been predicted to exceed screening criteria of 10CFR50.61. To cope with t his issue, a plant-specific PTS analysis had been performed following the m ethodology and procedures suggested in Reg. Guide 1.154. In this paper, the details of the plant-specific PTS analysis were described. To quantify the PTS risk of the embrittled RPV, the PTS-significant transient sequences we re selected and their frequencies were quantified. Then, thermal hydraulics characteristics of the selected transients were analyzed considering fluid mixing in the downcomer region of RPV, The through-wall cracking (TWC) fre quencies of the RPV due to various PTS transients were calculated using the probabilistic fracture mechanics analysis technique. The integrated PTS ri sk, or the total TWC due to all PTS-significant transient sequences, was lo wer than the Reg. Guide 1.154 limit during and beyond its design life. Fina lly, the lessons learned and technical issues found through the analysis ar e described in detail. (C) 2001 Elsevier Science Ltd. All rights reserved.