The Effects Of The Shape Function And Weighting Function In Parameters On The Kinetics Of ADS Subcritical Reactor

The sub-critical reactor of Accelerator Driven System(ADS)will exhibit the intense ‘time-space-energy' inhomogeneity in neutron kinetics when the accelerator beam transient occurs and the extraneous source changes rapidly,because of the interference by the strong extraneous source and the deep sub-criticality.It brings challenge for the development of neutron kinetic analysis.The point reactor kinetic model and the spatio-temporal kinetic model are the most commonly used neutron kinetic analysis method.In the Improved Point Reactor model and the Improved Quasi-Static(IQS)method,the kinetic parameters,which are the convolution of the weighting function,the kinetic operator and the shape function,are necessary for the calculation of the amplitude function.In traditional neutron kinetics,the ? fundamental neutron flux density is used as the shape function and the ? fundamental adjoint neutron flux density is used as the weighting function,which is applicable for the reactor system without the extraneous source and around the criticality.Whether it can apply to the ADS system is waiting for the verification.This paper takes the shape function and the weighting function as the object of the research,using the ? and prompt ? fundamental neutron fluxdensity as well as the ADS steady neutron flux density as the shape function and the ? and prompt ? fundamental adjoint neutron flux density as well as the ADS steady adjoint neutron flux density as the weighting function.Different shape functions and weighting functions are adopted for the calculation of kinetic parameters in the point reactor kinetic model and the spatio-temporal kinetic model by IQS method respectively.Those kinetic parameters are used to calculate and simulate the starting characteristic of the ADS subcritical reactor.And then,the effect of the kinetic parameters on the starting and beam-loss characteristics can be analyzed by comparing the calculation with the result obtained directly by the spatio-temporal kinetic equation.The result shows that: in the point reactor kinetic model,the shape function is the main influencing factor on the kinetic results and it is better to use the ADS steady neutron flux density as the shape function for the starting progress and the prompt ? fundamental neutron flux density as the shape function for the beam-loss condition;in the IQS spatio-temporal kinetic model,the weighting function is the main influencing factor on the kinetic results and it is better to use the ? fundamental adjoint neutron flux density as the weighting function for the starting progress and the ADS steady adjoint neutron flux density as the weighting function for the beam-loss condition.Based on the comparison,a improved weighting function model called Local Weighting Function of Kinetic is proposed and a coefficient is introduced to describe the effect by the inhomogeneous distribution ofexogenous neutrons on the adjoint source term.The results shows that the Local Weighting Function is suitable for the physic meaning and is benefit for the improvement of the accuracy.