Investigation on transient characteristics of fuel assembly in particle bed reactor core
To achieve orbit transfer and maneuver,the nuclear thermal propulsion(NTP)system should not only release the expected heat like the traditional power reactor but also have the capability of rapid start and thrust regulation.Therefore,transient analysis is important for system design,operation strategy,and integrated test of NTP.In this paper,a one-dimensional transient thermal hydraulics model of the Particle Bed Reactor(PBR)fuel assembly was established and the response performance was analyzed under a condition of power raising.It was observed that during the start-up procedure,the delay between heat transfer on the particle surface and heat release in the fuel kernel was minimal due to the strong heat removal by the coolant and the low heat capacity of the fuel particle.The effect prevented the over temperature and high thermal stress resulted from thermal storage,which benefits the rapid start.Under rated operating conditions,introducing a reactivity step change results in a thermal response that delays behind the variation in neutron density by about 0.1 s,which also benefits the system power and thrust rapid adjustment.Furthermore,the PBR core resistance rapidly increases with the elevation of core power.Therefore,further research is needed to optimize the matching of reactivity insertion and propellant supply during startup and thrust regulation processes.This study can inform the operation and control strategies of nuclear thermal propulsion systems.
particle bed reactornuclear thermal propulsionfuel assemblytransient modelrapid start
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