乏燃料操作大厅的剂量场随屏蔽水位的变化研究

在乏燃料水池完全丧失冷却能力和补水的事故工况下,压水堆核电厂乏燃料操作大厅内的剂量率将随着乏燃料水池水位的降低逐渐升高。本文以一典型压水堆核电厂的乏燃料水池为研究对象,采用QAD-CGGP程序,计算并分析了乏燃料操作大厅内的剂量场分布及其随水位的变化规律。计算结果表明:(1)在3.786～7.736 m水层厚度范围内,操作平台处的剂量率随水层厚度的变化不明显;(2)乏燃料水池上方的剂量率峰值位于高密格架区域上方;(3)在3.436～4.736 m水层厚度范围内,乏燃料水池上方的剂量率峰值在0.914～288 μSv/h范围内变化,并随着屏蔽水层厚度的减小呈指数递增趋势,且操作平台处剂量点的剂量率均满足乏燃料操作大厅辐射分区要求;(4)满足乏燃料操作大厅辐射分区要求所需的最低水位为+15.77 m。

Study on variation of dose field with shielding water levels in spent fuel operating hall

Under the accident conditions in which the spent fuel pool loses cooling capacity and water supply completely,the dose rate in the spent fuel operating hall of the pressurized water reactor nuclear power plant will gradually increase as the water level of the spent fuel pool decreases.In this paper,the spent fuel pool of a typical pressurized water reactor nuclear power plant is taken as the research object,and the QAD-CGGP program is used to calculate and analyze the distribution of the dose field in the spent fuel operating hall and its variation with the water level.The calculation results show that:(1)In the range of 3.786-7.736 m water layer thickness,the change of dose rate above operating platform with water layer thickness is not obvious.(2)The peak dose rate above spent fuel pool locates above the high-density grid area.(3)In the range of 3.436-4.736 m water layer thickness,the peak dose rate above spent fuel pool changes in the range of 0.914-288μSv/h and increases exponentially with the decrease of the thickness of the shielded water layer,and dose rate above operating platform meet the radiation zoning requirements of the spent fuel operating hall.(4)The lowest shielding water level needed to meet the radiation zoning requirements of the spent fuel operating hall is+15.77 m.