Procedure to prevent temperature rise of primary upper shielding in high temperature engineering test reactor (HTTR)

In a non-nuclear heat up test of the high temperature engineering test reac tor (HTTR), which was conducted in February 1997, the temperature of primar y upper shielding as well as helium gas temperature inside standpipes of th e reactor became much higher than expected. Because it was estimated that t hese temperatures should exceed design values at full power operation of th e HTTR, countermeasures were considered and taken to prevent the temperatur e rise. After applying two countermeasure steps, confirmation tests to demo nstrate the effect of the measures were performed. The test results and ext rapolation by temperature analysis finally showed that the countermeasures are appropriate, and the design temperatures should be observed at full pow er operation. (C) 2000 Elsevier Science S.A. All rights reserved.