锰浴法测量中子源发射率中各修正因子的蒙特卡罗计算

Monte Carlo Calculation of Correction Factors for Radionuclide Neutron Source Emission Rate Measurement by Manganese Bath Method

在采用锰浴法对放射性同位素中子源的发射率进行测量时,MnSO4溶液中55 Mn仅俘获部分源中子,故需考虑对未被55 Mn俘获部分的修正。用蒙特卡罗粒子输运程序MCNP对中子源强标准装置的锰浴系统进行模拟计算,对实验测量结果进行修正,并通过由国际计量局(BIPM)组织的中子源强度国际比对,验证了计算所建立模型的可靠性。利用MCNP程序的微扰计算功能,通过考虑MnSO4溶液的密度、源及其承托物材料的密度、源的位置、锰浴半径以及反应截面的改变对计算结果的影响,对模拟计算结果的不确定度进行了详细评定,提供了一种蒙特卡罗模拟计算结果不确定度的评定方法。

The manganese bath method for measuring the neutron emission rate of radio-nuclide sources requires corrections to be made for emitted neutrons w hich are not cap-tured by manganese nuclei .The Monte Carlo particle transport code MCNP was used to simulate the manganese bath system of the standards for the measurement of neutron source intensity .The correction factors were calculated and the reliability of the model was demonstrated through the key comparison for the radionuclide neutron source emis-sion rate measurements organized by BIPM .The uncertainties in the calculated values were evaluated by considering the sensitivities to the solution density ,the density of the radioactive material ,the positioning of the source ,the radius of the bath ,and the inter-action cross-sections .A new method for the evaluation of the uncertainties in Monte Carlo calculation was given .