贫铀球壳中D-T中子诱发的铀反应率的测量与分析

为校验次临界能源堆的概念设计,在R19.4/30.0 cm的贫铀球壳装置上采用活化法开展14 MeV中子学积分实验.布放6片贫铀活化片于球壳中与入射D离子束90°方向上的不同位置处活化,用HPGe探测器测量238U(n,γ)反应、238U(n,f)及235U(n,f)反应和238U(n,2n)各反应产物发射的特征γ射线,得到了相应的反应率.238U(n,γ)反应率的不确定度为3.6％-3.7％,238U(n,D和235U(n,f)反应率的不确定度为5.1％-5.9％,238U(n,2n)反应率的不确定为4.3％-4.7％.用MCNP5程序在ENDF66c数据库下进行模拟计算,238U(n,γ)反应率的计算值/实验值(C/E)为0.972-1.034,238U(n,f)和235U(n,f)反应率的C/E为0.983-1.058,238U(n,2n)反应率的C/E为0.979-1.019.

Measurements and analyses of uranium reaction rates on a depleted uranium shell with D-T neutrons

Aiming at checking the conceptual design of the subcritical reactor, an experiment using activation technique was carried out on a depleted uranium shell of R19.4/30.0 cm with D-T neutrons. The 6 depleted uranium foils were activated at 90° with respect to the incident D beam in the shell, and distributions of ²³⁸U (n, γ) reaction rates, ²³⁸U (n, f) reaction rates, ²³⁸U (n, f) reaction rates and ²³⁸U (n, 2n) reaction rates were obtained, by measuring characteristic γ rays generated by corresponding uranium reactions. The relative uncertainties are 3.6%–3.7% for ²³⁸U (n, γ) reaction rates, 5.1%–5.9% for ²³⁸U (n, f) reaction rates and ²³⁸U (n, f) reaction rates, and 4.3%–4.7% for ²³⁸U (n, 2n) reaction rates. The experiment was simulated using MCNP5 code with ENDF66c library, and the calculation-to-experiment ratios are 0.972–1.034 for ²³⁸U (n, γ) reaction rates, 0.983–1.058 for ²³⁸U (n, f) reaction rates and ²³⁸U (n, f) reaction rates, and 0.979–1.019 for ²³⁸U (n, 2n) reaction rates.