A Criticality Safety Study Of Dense Storage Of AP1000 Spent Fuel Based On Burn-up Credit

In order to obtain higher safety margin, when designing the management system of the spent fuel, such as the design of storage pool, transportation and reprocessing facility of spent fuel in nuclear power plants, we currently intend more likely to assume spent fuel as new fuels. However, it is a so conservative way of ignoring economy that the storage capacity for spent fuel of the container is greatly compressed. Burn-up credit is an analytical method of nuclear criticality safety that involves analyzing the changes of composition of spent fuel after irradiation can result in decrease reactivity and effectively improve the storage and transport of spent fuel economically.Theoretical calculation for burn-up credit is carried out in two steps: burn-up calculation and critical calculation. The purpose of the burn-up calculation is to accurately predict radionuclide compositions, the results of which will be used to next step, critical calculation, namely criticality safety analysis. In this work, according to the designs and the operation characteristics of the advanced nuclear power plants, the author analyses how the changes of assemblies burning process affect the reactivity of fuel-intensive storage system, and eventually calculates the simulation load curve of the spent fuel storage pool through critical calculation.First, STARBUCS module within SCALE program package is used in this paper. The validated analysis of benchmarks :Phase-IA and Phase-IIA published by OECD / NEA show that we can get reliable results through STARBUCS program calculation, which can serve as the tool to analyze burn-up credit criticality safety. The paper also focus on the study on the sensitivity analysis of different trust levels, and the envelope conditions of each factor within critical calculations in spent fuel storage pool can be got. The paper employs STARBUCS module and obtained each envelope parameters' values make a critical preliminary calculations on AP1000 nuclear power plant spent fuel storage pool. Finally,The lowest fuel consumption limits when different initial enrichment of spent fuel are placed in pool II district can be obtained. And the load curve of spent fuel storage pool has been worked out and the corresponding rules and conclusions of the paper has been obtained.The results show that if the spent fuel storage pools critical situations can be ensured safe,the load capacity of pool II region burnup credit theory increased 60% more than the new fuel pool I area, and the economy is greatly promoted.