Core safety characteristics of high flux safe reactor (HFSR)

Transient analyses are performed for graphite moderated helium-cooled high flux reactor to obtain the high flux safe reactor design. In order to promote the safety of the high flux reactor, the present design adopts the pebble bed reactor and its fuel technology. In the transient analyses, among the postulated off-normal events and accidents, the reactivity accident followed by a loss of helium forced circulation with system depressurization is found to be the severest potential event which may threaten the reactor safety from fission products release point of view. Several neutronic and thermal-hydraulic design parameters are indicated and exploited to promote the reactor safety. Neutronic and core thermal-hydraulic models are proposed and used to simulate the reactor responses to the off-normal events and accidents. As the results of the transient analyses and accident simulation, safe and optimal design parameters are obtained which provide high thermal neutron flux with a desirable spectrum and large usable volume constrained by safety limitations. (author)