基于加速器的硼中子俘获治疗装置束流整形体的设计及其临床参数研究

在硼中子俘获治疗（BNCT）中,束流整形体是BNCT装置产生高品质中子束的关键部件之一,其设计至关重要。本文基于25 MeV质子打锂靶产生中子的过程,对加速器驱动的BNCT中子源的束流整形体进行了可行性方案设计,研究了慢化体厚度差异对出口束流品质、头部模型中的剂量分布和临床参数等方面的影响。研究表明,可行性方案设计在30 mA质子束流驱动下,可达到IAEA对束流品质的要求;在本文3种慢化体厚度设计下,随着慢化体厚度的增加,出口超热中子束流强度减小,快中子份额减小,进一步导致优势深度变浅,正常组织最大剂量率减小,治疗时间变长。     

硼中子俘获疗法在医疗船上的应用与可行性设计研究

硼中子俘获疗法（BNCT）是一种能选择性地阻击癌细胞的生物靶向放射治疗方法,该治疗方法在医疗船上的应用设想是基于IAEA癌症关怀项目,旨为非洲等发展中国家提供癌症医疗援助及其他医疗服务。本文介绍了医疗船的中子照射治疗模块,该模块以国内已建成的医院中子照射器-1型（IHNI-1）为设计原型,根据船用反应堆的特殊环境和工况要求,对反应堆水池的外形、屏蔽材料的选型、堆本体系统和设备的结构以及中子照射治疗模块的总体布置进行设计优化。分析表明该设计理念和方案具备一定的开发价值和应用可行性。     

用于硼中子俘获疗法治疗束的光子谱仪设计

实验确认治疗束的谱源项参数是硼中子俘获治疗（BNCT）物理剂量学研究的重要环节之一,全面细致地掌握相关信息,对精准制定临床治疗计划进而准确评估患者的给予剂量十分重要。为验证理论计算源项光子能谱的可靠性,设计适用于BNCT治疗束特点（宽能量范围、高强度n/γ混合束）的新型光子谱仪。通过蒙特卡罗模拟方法优化探测器内的中子注量率、光子计数率及次级光子占比（次级光子计数率/初级光子计数率）三个重要参数,在降低辐射强度以避免探测器的辐射损伤和死时间过大的同时,尽可能抑制中子诱导次级光子的产生,将次级光子占比降至5.45,以实现BNCT治疗束光子谱的快速准确测量。同时,开展谱仪对不同能量光子响应的校准方法研究,以便得到准确的响应函数,为光子谱的解谱工作奠定基础。     

硼中子俘获治疗人头开颅模型内宏观吸收剂量分布

应用MCNP 4B程序模拟计算了硼中子俘获治疗(BNCT)人体头颅等效模型开颅时的宏观吸收剂量分布.采用含有肿瘤体的双椭球结构的等效模型,模拟了深部肿瘤、浅部肿瘤和表层肿瘤3个算例,计算了正常组织及肿瘤体内的宏观吸收剂量分布.计算结果表明,照射后部分网格的吸收剂量低于治疗标准18 Gy,但在同一网格中,肿瘤越靠近表层,吸收剂量越大,治疗效果越好.     

Usefulness of Single-Crystal Bismuth and Silicon for Neutron Radiography Facility

The atom ratios of Pu/U, ¹³⁴CS/¹³⁷CS and ¹⁵⁴Eu/¹³⁷CS of all the spent fuel assemblies in the full-core of JPDR-1 were calculated. These results were examined through comparison with the values measured by nondestructive γ-ray spectrometry. There were some differences between the calculated and the measured atom ratios of Pu/U and burnup. The calculated atom ratios of ¹³⁴CS/¹³⁷CS and ¹⁵⁴Eu/¹³⁷Cs were slightly less than the measured values for almost all the fuel assemblies. The most probable production amount of Pu, estimated on the basis of the calculated and the measured atom ratios and their accuracies, agreed well with the amount recovered from the reprocessed fuel assemblies.     

Analysis of Neutron and Secondary Gamma-Ray Transport in Air-Over-Ground Geometry by PALLAS-2DCY-FC Code

Comparisons are made between PALLAS calculated with meaured neutron and γ-ray doses above the ground in an air-ground medium for HENRE accelerator and BREN reactor, yielding good agreements except for a 8.23-m height of HENRE source, in which the calculation overestimates the neutron dose by a factor of 1.5 due to the use of a rough angular quadrature set. Disregard of the ground results in a decrease by a factor of 2 in both neutron and γ-ray doses compared with those for the presence of the ground, while for an infinite-air medium both these doses increase with distances from the source, which indicates that the ground should not be. ignored in the neutron and secondary p-ray transport calculation. For assumed neutron skyshine calculations disregard of the ground results in a decrease in the neutron dose by a factor of 1.5 and 1.7 and also in the secondary γ-ray dose by a factor of 1.35 and 3~5 respectively for a 14-MeV source and a fission source. In addition to the importance of inclusion of the ground in neutron skyshine calculations, an additional essential factor is the secondary γ-ray production due to neutron inelastic scattering interaction with nitrogen for the 14-MeV source, or the one due to neutron capture interactions in both ground and air for the fission source.     

Effect of Polynomial Expansion Order of Intranode Flux Treatment in Nodal SN Transport Calculation Code NSHEX for Large-Size Fast Power Reactor Core Analysis

The nodal discrete ordinates (S_N) transport calculation code for three-dimensional hexagonal geometry NSHEX treats intranode flux distribution using a polynomial series and considers the angular dependence of flux by the SN method. For the improvement of calculation accuracy of NSHEX for practical use to large-size fast reactor plants, the maximum order of the polynomial series is extended from two to six. In order to check the effect of the polynomial expansion order, NSHEX is applied to the intermediate-size fast power reactor core “Monju” and the large-size one “Super Phenix,” including various control rod insertion conditions. From the application, it is found that extension of the polynomial expansion order is effective especially for the large-size core “Super Phenix” under the control-rod-inserted condition.