Research On Simulation Of Fast Reactor Core Physics Based On The Point Reactor Model

The development of fast reactor technology is essential to the long-term sustainability ofthe world’s energy. For the advantages of the simulation technology in the field of nuclearenergy technology, we can speed up the fast reactor technology research by providingimportant technical means. It is needed through the introduction of different reactivity toachieve the close-to-start，and power changes for the reactor. If the reactivity inserted into thereactor is not proper, it could result in the reactivity accidents and then endangering the safetyof the reactor. Therefore, it is an important part of the reactor safety analysis to study thepower variation with inserting reactivities.The reactivity disturbance of fast reactor is more quickly than the light water reactor,andthe effects of reactivity are more complex. In order to ensure the safe operation of the reactor,it requires the operator can quickly determine the transient process of reactor with the reactorrunning. It is practically significant to develop accurate, effective, fast simulation model andcalculation methods for the simulation of reactor physics.In this paper, China Experimental Fast Reactor (CEFR) was selected for the simulationstudy. It established CEFR reactor core physics simulation model with considering variousreactivity feedback effects.Core physics calculations used point reactor neutron kineticsmodel with six groups of delayed neutron, and made use of Gauss precise time-integrationmethod to solve point reactor equations. Gauss precise time-integration method requires lesstime step, and it has more obvious advantages in the aspects of the calculation accuracy andcomputational speed than other commonly used numerical integration methods.This paper also established the calculation model of major CEFR reactivity feedbackeffects, CEFR average core coolant temperature and fuel temperature and the power afterreactor shutdown.To study the power and reactivity changes after the reactor shutdown, it used theempirical formula for the calculation of decay heat power. In addition, this paper alsoconsidered the fuel consumption impact on the reactor. It made a reasonable simplifiedassumption here. It only considered the impacts of the reactivity caused by burn-up changeson the core, but there was not detailed fuel consumption calculation. It develops programs of CEFR reactor core physics simulation in this paper, and theresults have a good match to the actual reactor conditions. These programs can well reflect theCEFR power, temperature, and reactivity changes, and it also can be used for safety analysisand evaluation of CEFR.