摘要
目的研究裂变中子谱照射中国参考人单位中子注量在血液中产生的24Na比活度AB/φ，并分析实验场所地板、墙壁和天花板等的散射中子对测量结果的影响。方法利用强度约3×10^8中子／s的252Cf中子源对中国参考人模体进行照射。模体躯干尺寸按中国参考人制作，外壳由4mm有机玻璃制成，内有人体组织当量液，主要元素的重量比为H：N：O：C=10．6：2．5：63．2：23．7，密度1．007g／cm2（20℃）。中子源到模体长轴的照射距离d（m）分别为1．1、2．1、3．1和4．1。中子源和模体的剑突部位离地面1．6m。结果单位中子注量照射在模体内产生的34Na平均比活度与照射距离有关，根据实验结果推导出的AB/φ的最大值（AB/φ）约为1．85×10～Bq·cm2·g-1。结论AB/φ相当于252Cf中子谱平行射线照射的情况，这一数据比文献报道的BOMAB模体的实验结果大3％。实验表明，在照射场所的地面、墙壁散射中子对^24Na比活度有显著的贡献，但对入射中子的剂量贡献却相对较小。因此，在实际的中子照射事故中，利用血液^24Na比活度估算受照者的中子剂量时，事故场所散射中子的贡献将导致过高估计中子剂量，需要进行修正。
Objective To investigate the specific activity of 24Na per unit neutron fluence,AB/φ, in blood produced for Chinese reference man irratiaded by 252 Cf neutron source, and to analyze the effects of scattering neutrons from ground, wall, and ceiling in irradiation site on it. Methods A 252Cf neutron source of 3× 10^8 n/s and the anthropomorphic phantom were used for experiments. The phantom was made from 4 mm thick of outer covering by pcrspex and the liquid tissue-equivalent substitute in it. The data of phantom dimensions fit into Chinese reference man. The weight ratios of H, N, O and C in substitute equal to 10. 6： 2.5： 63.2： 23.7, and its density was 1. 006-1. 008 g/cm3 （20℃）. The irradiation-distances, d, from source to long axis of phantom were 1. 1, 2. 1, 3. 1 and 4.1 m, respectively. Both the neutron source and the position of xiphisternum of the phantom were 1.6 m above the floor. Results The average specific activity of 24Na per unit neutron fluence was related to the irradiation-distances, d, and its maximum value ,AB/φ, deduced by experimental data was about 1.85 × 10 -7 Bq·cm2· g-1. Conclusions The AB/φ corresponds to that of phantom irradiated by plane-parallel beams, and the value is about more 3% than that by BOMAB phantom reported in literature. It has shown that floor-（wall-）scattered neutrons in irradiation site have significant contribution to the specific activity of 24 Na , but they contributed relatively little to the induced neutron doses. Consequently, using the specific activity of 24Na for assessing accidental neutron doses received by an individual, the contribution of scattered neutrons in accident site will lead dose to be overestimated, and need to be correct.
出处
《中华放射医学与防护杂志》
CAS
CSCD
北大核心
2011年第1期67-70,78,共5页
Chinese Journal of Radiological Medicine and Protection
基金
后勤系统重点科研项目（99-3302）
