基于矩阵谱的反应堆屏蔽仿真计算

Simulation of Reactor Shielding Based on Matrix Fission Spectrum

研究了热中子反应堆屏蔽准确性优化设计问题。由于传统的反应堆屏蔽计算并未考虑引发裂变的中子对裂变能谱的影响,使得燃耗加深时仿真计算结果与实际情况差别较大。针对上述问题,提出从与入射中子能量相关的Maxwell谱出发,对入射中子的能量进行分群,构造出矩阵谱,然后确定了仿真计算中对裂变中子能量的抽样步骤,并在中子输运计算软件MCNP程序上进行了仿真计算。结果表明,根据矩阵谱计算得到的结果能够反映出燃耗变化对屏蔽计算的影响,能够为反应堆屏蔽设计提供更为准确的依据。

The shielding problem of thermal reactor is studied. Because the influence on fission spectrum caused by the energy of initial neutron is not considered in traditional calculation of reactor shielding, the difference between calculation result and actual situation is huge when the burn -up level is growing. To solve this problem, matrix fis- sion spectrum is constructed based on the energy - related Maxwell spectrum. And then the sample steps of energy of fission neutron based on matrix fission spectrum are given. At last, the flux on inner surface of pressure vessel is sim- ulated by MCNP code. The results show that the result of matrix fission spectrum can reflect the influence of variation of burn - up in shielding calculation. And matrix fission spectrum can afford high accurate basis for reactor shielding design.