There is an obvious effort to increase the burn up of used fuel assemblies in order to improve fuel utilization.A more effective operation can be realized by extending the fuel cycles or by increasing the number of re...There is an obvious effort to increase the burn up of used fuel assemblies in order to improve fuel utilization.A more effective operation can be realized by extending the fuel cycles or by increasing the number of reloadings.This change is nevertheless connected with increasing the uranium enrichment even above 5% of 235U. Burnable absorbers are widely used to compensate for the positive reactivity of fresh fuel. With proper optimization, burnable absorbers decrease the reactivity excess at the beginning of the cycle, and they can help with stabilization of power distribution. This paper describes properties of several materials that can be used as burnable absorbers. The change in concentration or position of the pin with a burnable absorber in a fuel assembly was analyzed by the HELIOS transport lattice code. The multiplication factor and power peaking factor dependence on fuel burn up were used to evaluate the neutronic properties of burnable absorbers. The following four different materials are discussed in this paper: Gd2O3, IFBA, Er2O3,and Dy2O3.Gadolinium had the greatest influence on fuel characteristics. The number of pins with a burnable absorber was limited in the VVER-440 fuel assembly to six. In the VVER-1000 fuel assembly, 36 pins with a burnable absorber can be used as the assembly is larger. The erbium depletion rate was comparable with uranium burn up.Dysprosium had the largest parasitic absorption after depletion.展开更多
基金supported by the Technology Agency of the Czech Republic(No.TE01020455)
文摘There is an obvious effort to increase the burn up of used fuel assemblies in order to improve fuel utilization.A more effective operation can be realized by extending the fuel cycles or by increasing the number of reloadings.This change is nevertheless connected with increasing the uranium enrichment even above 5% of 235U. Burnable absorbers are widely used to compensate for the positive reactivity of fresh fuel. With proper optimization, burnable absorbers decrease the reactivity excess at the beginning of the cycle, and they can help with stabilization of power distribution. This paper describes properties of several materials that can be used as burnable absorbers. The change in concentration or position of the pin with a burnable absorber in a fuel assembly was analyzed by the HELIOS transport lattice code. The multiplication factor and power peaking factor dependence on fuel burn up were used to evaluate the neutronic properties of burnable absorbers. The following four different materials are discussed in this paper: Gd2O3, IFBA, Er2O3,and Dy2O3.Gadolinium had the greatest influence on fuel characteristics. The number of pins with a burnable absorber was limited in the VVER-440 fuel assembly to six. In the VVER-1000 fuel assembly, 36 pins with a burnable absorber can be used as the assembly is larger. The erbium depletion rate was comparable with uranium burn up.Dysprosium had the largest parasitic absorption after depletion.
