Self-limiting power excursion characteristics of light water reactor, (1). Doppler-limited pulse operation tests on HTR

The Doppler limited power excursion characteristics of a light water reactor and the shutdown mechanism by scram were analyzed on the Hitachi Training Reactor (HTR). For the purpose of the pulse operation tests, modifications were applied to the HTR to provide pulsing capability; a pulse rod was added, together with a back up device for shutdown, and provision of three instrumented fuel assemblies, equipped with thermocouples; the Al-clad fuel rods were replaced by stainless steel clad rods. About 100 runs of pulse operation tests were performed in fullest security with reactivity insertions ranging up to 1.0 % Δk/k, in which last case the peak power reached 38 MW, with a reactor period of 29 msec. (author)