不同级钚材料的衰变放热功率计算分析

钚材料中放射性核素会不断衰变并释放能量,改变钚材料及周围部件的温度。为研究不同级钚材料在其整装存储及运输过程中衰变放热功率随时间的变化规律,依据不同级钚材料的放射性核素组分,在分析核素级联衰变规律的基础上,并在物理模型中考虑衰变时的能量分支比,计算得到了武器级钚、反应堆级和混合级钚材料中各核素的衰变放热功率和总热功率随时间的演变规律。计算结果表明,1 kg不同级的钚材料,其衰变放热功率最大的是混合级钚,放热最少的是武器级钚;武器级钚材料衰变放热功率主要来自于~(239)Pu,而反应堆级与混合级钚材料的衰变放热功率主要来自于~(241)Pu和~(238)Pu。三种不同级钚材料中,~(242)Pu的衰变放热功率均很小。考虑能量分支比后,可更准确地计算给出钚材料的衰变热功率。

Analysis of decay heat power generation for plutonium with various grades

Background: Radioactive nuclides contained in plutonium material will continually decay and release energy, which will change the temperature of plutonium materials and the surrounding components. Purpose:This study aims to analyze the releasing heat power of various grades plutonium materials in the process of bulk storage and transportation of plutonium. Methods:According to the isotopic quality composition of various grades plutonium, the time evolutions of decay heat power of each radioactive nuclide contained in weapons grade plutonium, reactor grade plutonium, and mixed oxide grade plutonium are obtained. And the total decay heat power of various grades plutonium as a function of time is also calculated, on the basis of the analysis of radionuclide decay cascade regulation, with the energy branching ratios during decay in the physical model taken into consideration. Results:The calculation results showed that the decay heat power varied with the grades of plutonium material. For 1-kg different grades plutonium material, the maximum decay heat power quantity is released by mixed oxide grade plutonium, while the weapons grade plutonium releases the least decay heat power quantity. The heat power released by weapons grade plutonium is mainly from 239Pu, while the main heat power is from 241Pu and 238Pu for the reactor and mixed oxide grade plutonium material. The decay heat power released by 242Pu is few compared with other nuclides for the three grades of plutonium materials. Conclusion: The releasing decay heat power of plutonium materials can be calculated more accurately by considering the energy branching ratios.