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通过实验测得反应堆停堆时刻裂变产物~(137)CS、~(148)Nd等监测体的浓度值,进而推算出辐照燃料元件的燃耗值是通常采用的方法。它需要若干参数,如裂变产物的平均裂变产额,反应(n,γ)的修正量,放射性裂变产物的堆内衰变修正量,可裂变核素的平均裂变能量等。这些参数都同燃料的辐照历史紧密关联。本文概述了上述参数的计算方法并给出了计算结果。方法的主要特点是:1.以考验元件的实际参数为输入数据;2.根据反应堆实际运行史反复循环模拟计算;3.除计算重核素及所要求的裂变产物的原子浓度和放射性外,仔细计算了~(137)Cs和~(148)Nd等核素(n—1)衰变链中子俘获反应的修正量。
The concentrations of fission products such as ~ (137) CS and ~ (148) Nd were measured experimentally at the shutdown time of the reactor, and then the burnup values of the irradiated fuel components were generally calculated. It requires several parameters such as the average fission yield of the fission product, the correction of the reaction (n, γ), the in-reactor decay correction of the radioactive fission product, the average fission energy of the fissile nuclide, and the like. These parameters are closely related to the history of the fuel irradiation. This article summarizes the calculation of the above parameters and gives the calculation results. The main features of the method are: 1. Taking the actual parameters of the test element as input data; 2. Repetitively calculating the cycle according to the actual operation history of the reactor; 3. Except for calculating the atomic concentration and radioactivity of the heavy nuclide and the required fission products, The corrections for the neutron capture reaction in (n-1) decay chains of ~ (137) Cs and ~ (148) Nd were carefully calculated.