选取Pu-238为放射源,采用简化的级联衰变链对其进行源项分析,得到放射源各衰变子体原子数及放射性活度的变化曲线,在此基础上,采用MCNP程序,对放射源进行了精确建模,对放射源辐射场及其有效屏蔽问题进行了模拟计算,得到放射源周围中子、γ能谱及辐射场分布,辐射场计算值与参考实验剂量吻合较好,屏蔽体的采用可有效降低放射源的辐射剂量,其中,γ剂量降低为裸源的0.1％左右,中子剂量降低为裸源的13％～17％.%Calculating the dose around radioactive source by simulation is an important way of radiation analysis and application. It is widely used in engineering. The paper uses a simple decay cascade to analyze the Pu-238 source, and obtains the varying trends of atomic number and activity for the source and its daughters. In view of the above-mentioned situation, it sets up an elaborate model by MCNP code, calculating the radioactive field and the problem about shield and getting the gamma and neutron energy spectra around the source. The result agrees with the reference, the shield used can reduce the dose effectively. Concretely, the dose of gamma is reduce to about 0. 1%, and the neutron, 13%~17%.
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