压水堆元件厂核材料衡算与评价的难点分析

Analysis of difficulties in accounting and evaluating nuclear material of PWR fuel plant

依据《低浓铀转换及元件制造厂核材料衡算》导则要求,以我国某压水堆元件厂的核材料衡算与评价数据为基础,对核材料衡算与评价过程中设备管道滞留量测量和不明核材料量评价涉及的随机误差方差、长期系统误差方差和短期系统误差方差对总误差方差的贡献程度等难点进行深入分析研究,并提出可行的建议和措施,为进一步完善和提高压水堆元件厂的核材料衡算与评价工作提供借鉴。

Background： Nuclear materials accountancy must be developed for nuclear facilities, which is required by regulatory in China. Currently, there are some unresolved problems for nuclear materials accountancy of bulk nuclear facilities. Purpose： The retention values and measurement errors are analyzed in nuclear materials accountancy of Power Water Reactor （PWR） fuel plant to meet the regulatory requirements. Methods： On the basis of nuclear material accounting and evaluation data of PWR fuel plant, a deep analysis research including ratio among random error variance, long-term systematic error variance, short-term systematic error variance and total error involving Material Unaccounted For （MUF） evaluation is developed by the retention value measure in equipment and pipeline. Results： In the equipment pipeline, the holdup estimation error and its total proportion are not more than 5% and 1.5%, respectively. And the holdup estimation can be reagarded as a constant in the PWR nuclear material accountancy. Random error variance, long-term systematic error variance, short-term systematic error variance of overall measurement, and analytical and sampling methods are also obtained. A valuable reference is provided for nuclear material accountancy. Conclusion： In nuclear material accountancy, the retention value can be considered as a constant. The long-term systematic error is a main factor in all errors, especially in overall measurement error and sampling error. The long-term systematic errors of overall measurement and sampling are considered important in the PWR nuclear material accountancy. The proposals and measures are applied to the nuclear materials accountancy of PWR fuel plant, and the capacity of nuclear materials accountancy is imoroved.