用MCNP程序计算水平辐照孔道屏蔽

Shielding calculation of horizontal radiation ducts using the MCNP code

研究堆中水平辐照孔道用以从堆芯附近引出高能中子流。由于水平辐照孔道的几何形状比较复杂 ,采用两维输运计算模型将会引入较大的误差 ;同时 ,在计算过程中由于粒子穿行的距离比较长 ,所需的计算时间也是很大的。讨论了如何用 Monte Carlo方法的 MCNP程序进行水平孔道的屏蔽计算 ,引入了分段 -衔接计算方法 ,着重介绍了与 MC-NP的接口和表面源的设置问题。计算结果表明 ,分段 -衔接的 MCNP方法能够大大的改善 Monte Carlo方法的抽样 。

Horizontal radiation ducts in research reactors are used to reduce the high energy neutron flux from near the core. Since the duct geometry is very complicated, large errors will be introduced if a two dimensional transport code is used. Also, a large amount of computing time is needed because of the long distances the particles have to penetrate. This paper introduces a method to calculate the shielding of a horizontal duct using the MCNP code (Monte Carlo Neutron Photo Code) using the subsection method with emphasis on setting the surface sources for the MCNP code. The calculated results show that the subsection method in MCNP can greatly improve the Monte Carlo sampling and that the MCNP code can effectively solve the horizontal duct shielding problem.