Development of High Temperature Isolation Valve for the HTTR Hydrogen Production System

Japan Atomic Energy Research Institute (JAERI) has been carried out research and development on the high temperature engineering test reactor (HTTR) hydrogen production system. One of the key components in the HTTR hydrogen production system is a high temperature isolation valve (HTIV) installed on the hot helium gas piping penetrating the reactor containment vessel. Angle valve with inner thermal insulator was selected for HTIV and conceptual design was performed. The structural integrity of HTIV was clarified by the stress analyses. Allowable helium leak rate of HTIV was discussed. Helium leak tests using small-scaled valve seat models were performed to decide the seat surface shape and valve closing force. The test results show that the leak rate of wedge shape seat increased in proportion to the number of simulated temperature and stress cycles loaded on the seat models before helium leak test, however that of flat seat did not depend on the number of cycles. So flat seat is adopted for HTIV. It was found that the seat closing force of 30MPa is reasonable to meet the allowable helium leak rate.