LOFT Reactor Vessel Head Instrument Penetration, Flange Thermal Analysis

摘要

A redesign of the LOFT instrument penetration necessitated a reanalysis of the thermal conditions existing in the nozzle and flange during a Loss of Coolant Experiment (LOCE). The maximum temperature gradient existing in the instrument flange will be used to determine the thermal stresses and maximum number of allowable cycles for the instrument flange. Based upon the specification and thermal conditions predicted by RELAP4/MOD5, the maximum temperature gradient through the flange will not exceed 216 exp 0 F. The thermal conditions predicted by RELAP4/MOD2 for the nozzle head penetration assembly were less severe than those used in the original thermal-stress analysis, so only the flange was analyzed here. If the thermal stresses are marginal with the 216 exp 0 F delta T, a more detailed analysis should be done as the heat slab model used in RELAP is only one dimensional. Conservative hand calculations were performed for a heatup rate of 100 exp 0 F per hour and it was determined that the worst temperature gradient through the flange will be less than 81 exp 0 F. (ERA citation 03:052769)