快速计算堆芯燃料装载模式的理论

A THEORY OF FAST SEARCH FOR FEUL LOADING PATTERN IN LWRS

根据两群快速节块法理论和堆芯功率分布要求,导出了堆芯反应性分布方程。求得堆芯反应性分布以后,将所提供的燃料组件放置在与其反应性相对应的堆芯位置上,就得到堆芯燃料装载模式。并在CYBER825/170计算机上编制了计算程序。对两维IAEA基准问题作数值检验,表明反应性分布的误差很小,最大的△k约为0.005,花费的CPU时间约为1秒。

In order to fast search for fuel loading pattern without trial and error, a theory for predicting in-core reactivity distribution, according to power necessity and available assemblies, has been develoned on basis of the fast computing nodal method and two group diffusion theory. In that. the fast group flux distribution can be predicted from power necessity and the approximation of fast group constants to be independent of nodes. Then,the thermal group fluxes are expressed by both known powers and predicted fast fluxes. After replacing thermal flux, the thermal diffusion equations turn into some equations that have only unknown group constants. The unknown constants are expressed approximately by making use of some expansions of infinite multiplication factors of available assemblies. In such a way, the nonlinear reactivity equations are developed and then solved, where node reactivities are the only unknown physical quantities. Finally, the loading pattern is obtained by setting some of available assemblies at each node location where corresponds to a closest reactivity of between laid assembly and node. A computer code LOADMP based on the theory has been made. The theory has been tested numerically on IAEA benchmark problem,and gives an accurate prediction of reactivity distribution and loading pattern. The CPU-time for making a loading pattern search is saved very much,about one second on the CYPER-825/170machine.