The influence of chemistry concentration on the fracture risk of a reactor pressure vessel subjected to pressurized thermal shocks

• Probabilistic fracture mechanics method was used to analyze a reactor pressure vessel.
• Effects of copper and nickel contents on RPV fracture probability under PTS were investigated and discussed.
• Representative PTS transients of Beaver Valley nuclear power plant were utilized.
• The range of copper and nickel contents of the RPV materials were suggested.
• With different embrittlement levels the dominated PTS category is different.

The radiation embrittlement behavior of reactor pressure vessel shell is influenced by the chemistry concentration of metal materials. This paper aims to study the effects of copper and nickel content variations on the fracture risk of pressurized water reactor (PWR) pressure vessel subjected to pressurized thermal shock (PTS) transients. The probabilistic fracture mechanics (PFM) code, FAVOR, which was developed by the Oak Ridge National Laboratory in the United States, is employed to perform the analyses. A Taiwan domestic PWR pressure vessel assumed with varied copper and nickel contents of beltline region welds and plates is investigated in the study. Some PTS transients analyzed from Beaver Valley Unit 1 for establishing the U.S. NRC's new PTS rule are applied as the loading condition. It is found that the content variation of copper and nickel will significantly affect the radiation embrittlement and the fracture probability of PWR pressure vessels. The results can be regarded as the risk incremental factors for comparison with the safety regulation requirements on vessel degradation as well as a reference for the operation of PWR plants in Taiwan.