为确定主动中子多重性反应系数对测量精度的影响,对大空腔探测系统主动中子多重性方法测量铀部件质量的全过程进行了直接模拟,基于MCNPX对28组相同浓缩度、相同密度、不同质量的内径1.2 cm的半球壳型铀部件进行了模拟研究,获得了反应系数与样品增殖的关系曲线。对半球型、内径1.2 cm的半球壳型铀部件的模拟测量质量偏差都在1.5%以内,对内径3.2 cm的半球壳型、半径6 cm和8 cm的圆柱型等形状差异较大的铀部件质量也仅偏小5%~10%。

This paper describes all-process direct simulation of active neutron multiplicity counting on New Pile Laboratory—Neutron Multiplicity Counter (NPL-NMC). Twenty-eight hemispheroidal shell uranium components with an inner radius of 1.2 cm were simulated by MCNPX code, which had different mass but the same enrichment and density. The relation curve between coupling and multiplication was obtained. The mass deviation of simulation measurement was within 1.5% for the hemispheroid and hemispheroidal-shell (inner radius 1.2 cm) uranium components, while the mass deviation was lower 5%-10% for the hemispheroidal-shell (inner radius 3.2 cm) and cylinder(inner radius 6, 8 cm) uranium components.