Effects of pressure condition for LOCA acceleration test profile on equipment integrity

All equipment related to safety in nuclear power plants must perform their safety functions under defined condition, including postulated DBA condition as well as normal environmental condition. LOCA (Loss of Coolant Accident) of the DBA is the severest condition of high temperature, high pressure and sprayed chemicals during approximately 6 months. Since the perfect qualification of equipment in such LOCA test requires a long time and highly reliable test facility, the realistic LOCA simulation test for equipment qualification is performed with modified shortened test profile enveloping temperature and pressure condition of specific NPP. The detailed process for modification of this LOCA test profile are proposed by Park et al. (2006), based on the Arrhenius equation. However, the shortened test profile may cause quite unfavorable effects on equipment integrity during and after LOCA test. In this paper, we have found that failure possibility of limit switch during LOCA test may be greatly increased due to elevated test pressure in the modified test profile. Therefore, we suggest the refined modification method of LOCA test profile, which is applicable for pressure-vulnerable equipment. (author)