硼中子俘获治疗的进展及前景

硼中子俘获疗法(boron neutron capture therapy, BNCT)是一种可以选择性杀伤肿瘤细胞的放射疗法,硼(~(10)B)化合物携带剂注入人体后,会选择性富集于肿瘤细胞,与中子发生俘获反应,释放α粒子和~7Li粒子杀死肿瘤。BNCT以靶向治疗、低毒高效等优势成为了放射治疗领域的新型手段。从上世纪开始,硼中子俘获疗法已在世界各国崭露头角并逐渐发展起来,已经能够成功治疗脑胶质瘤、黑色素瘤等多种疾病。目前,BNCT面临着如何研发创新更高效的含硼药物,建立更为精确的硼剂量测量体系,以及医用中子源如何摆脱核反应堆等问题。本文对BNCT的原理、优势、进展以及所面临的问题进行简要综述与探究。     

硼中子俘获治疗的进展及前景

硼中子俘获疗法(boron neutron capture therapy,BNCT)是一种可以选择性杀伤肿瘤细胞的放射疗法,硼(10 B)化合物携带剂注入人体后,会选择性富集于肿瘤细胞,与中子发生俘获反应,释放α粒子和7Li粒子杀死肿瘤。BNCT以靶向治疗、低毒高效等优势成为了放射治疗领域的新型手段。从上世纪开始,硼中子俘获疗法已在世界各国崭露头角并逐渐发展起来,已经能够成功治疗脑胶质瘤、黑色素瘤等多种疾病。目前,BNCT面临着如何研发创新更高效的含硼药物,建立更为精确的硼剂量测量体系,以及医用中子源如何摆脱核反应堆等问题。本文对BNCT的原理、优势、进展以及所面临的问题进行简要综述与探究。     

硼中子俘获治疗

硼中子俘获治疗(BNCT)的基本原理是应用热中子照射靶向聚集在肿瘤部位的^10B，^10B俘获中子后产生α粒子和^7Li，α粒子和^7Li杀灭肿瘤细胞而起到治疗作用。BNCT在临床上主要用于神经胶质瘤和黑色素瘤的治疗。文章主要对有关BNCT的基础及临床研究进行了简要综述，内容包括BNCT的基本原理、^10B在肿瘤细胞的聚集、中子源、实验研究现状以及BNCT面临的挑战与问题等。     

位置灵敏热中子探测器设计

研究了一种位置灵敏热中子探测器的设计方案.该方案基于热中子与硼-10的核反应10B(n,α)7Li,采用固体硼-10作为靶物质,探测出射粒子α和产物粒子7Li获得中子的位置信息.利用MC-NP软件模拟了α粒子在靶内的分布,从而求出该探测器的靶厚,物理效率以及位置分辨能力.     

快中子与~6Li,~7Li的三体反应

用载锂乳胶对14—18兆电子伏中子与~6Li,~7Li的三体反应——~6Li(n,nd)α与~7Li(n,nt)α作了“运动学完全”的测量。由此得到次级中子能谱以及通过~6Li第一激发态与~7Li第二激发态的非弹性散射中子的角分布。观察到中子与锂核内α集团的准自由散射。用“平面波冲量近似”得到了Li核表面α集团的动量分布,间接地证明了~6Li核中氘集团有收缩效应。     

基于加速器~7Li(p,n)反应的硼中子俘获治疗中子源的优化设计

7Li(p,n)反应以中子产额大、反应阈能低等优点成为硼中子俘获治疗加速器驱动中子源所用中子反应的候选类型之一。本文重点研究了该中子产生反应作为加速器驱动中子源的中子产额及其能谱特性,并对产生的高能中子束流进行慢化,使其满足BNCT治疗要求。首先采用蒙特卡罗程序MCNPX2.5.0模拟加速器7Li(p,n)反应过程,得到1.9 3.0 MeV能量入射质子的中子产额及其能谱,并详细研究了质子入射能量为2.5 MeV的最佳条件下产生的中子束流特性;进而提出中子束流的慢化设计方案,并对慢化所得超热中子束品质进行分析研究。模拟计算结果表明,10 mA流量的2.5 MeV能量入射质子所产生的中子束经过慢化处理后,可以很好地满足硼中子俘获治疗的中子束流要求。     

硼烷化合物的合成：从小硼烷分子到多面体硼烷

硼烷是一类重要的含硼化合物，包含反应性较高的小硼烷分子和较稳定的多面体硼烷化合物，广泛应用于能源、材料、医药，特别是作为硼中子俘获疗法(boron neutron capture therapy, BNCT)潜在的硼载体等领域。在一百多年的硼化学发展史中，合成新型硼烷化合物和优化硼烷合成方法始终是硼烷化学研究的重要组成部分。鉴于此，本文系统总结了从小硼烷分子到多面体硼烷以及碳硼烷的合成方法，提供了硼烷化合物的结构和核磁谱图，以期为对硼烷化学感兴趣的读者提供基础知识以及进一步促进改善硼烷化合物的合成方法和探索硼烷化合物的应用。     

碲锌镉探测器中子探测性能研究

研究了基于碲锌镉可以吸收其与中子的~(113)Cd(n,γ)反应产生的瞬发γ,采用~(241)Am-Be源进行中子探测实验,结果表明碲锌镉探测器对中子有较好的响应,能量分辨率较高;通过探测带电粒子间接探测中子,即在碲锌镉晶体表面涂硼,基于硼与中子反应产生的α和~7Li在碲锌镉中电离进行探测。采用MCNPX及Geant4两种软件模拟硼层厚度及CZT厚度对中子探测效率的影响,设置适当的甄别阈以降低γ射线的影响。模拟结果表明:当硼层厚度为2.7μm,碲锌镉厚度为1.6μm时可达到最大探测效率。对两种探测方法进行了对比研究,证明了碲锌镉应用于中子探测的可行性。     

利用~(11)B(n,α)~8Li(β~-)~8Be(2α)反应测量快中子能谱的乳胶方法

本文提出了一个在强γ本底条件下测量8兆电子伏以上无定向快中子能谱的新方法。利用载硼乳胶中的~(11)B(n,α)~8Li(β~-)~8Be(2α)反应测量了9.97,12.06,14.10和18.12兆电子伏的单能中子谱以及14.1兆电子伏中子经铀球壳后的慢化能谱。     

用于硼中子俘获治疗的碳硼烷多肽衍生物

含碳硼烷多肽衍生物的设计和应用得到越来越多人们的关注，尤其是作为硼中子俘获治疗(boron neutron capture therapy, BNCT)硼携带剂用于治疗恶性肿瘤极具发展前景。BNCT利用¹⁰B与中子俘获反应，放出α粒子杀死肿瘤细胞。作为一种二元靶向疗法，其成功关键就是硼携带剂的靶向性和亲和力的效果，当前如何设计更高效的硼携带剂是BNCT发展的主要问题。多肽作为生物必需物质，增加其衍生物靶向性的同时被肿瘤特异性摄取，是含碳硼烷多肽化合物作为硼携带剂极大的优势。本文首次对已报导的含碳硼烷多肽衍生物进行分类总结，并评估作为硼携带剂应用于中子俘获治疗的发展潜力。对含碳硼烷多肽衍生物的总结，将为新一代硼携带剂设计用于中子俘获治疗发展提供研究动力。     

Voids in boron carbide

Two different void morphologies have been observed in the commercial grades of boron carbide that are currently undergoing assessment as candidates for the control rod material in fast breeder reactors. Some grains in unirradiated powders contain dodecahedral voids which are closely associated with iron-rich precipitates believed to be cementite, and neutron-irradiated powders also contain plate-shaped voids oriented parallel to {110} planes (rhombohedral indices). These latter voids are believed to contain fission gas and their plate-like morphology is attributed to work which the gas can do in elastically deforming the matrix if their shape is changed from spherical to disc-shape.     

Burnup characteristics and performance of boron nitride and boron coated urania and urania-gadolinia fuels

In this research the burnup performance of (1) boron nitride (BN) and (2) boron nitride-boron (B), hybrid coated urania (UO₂) and urania-gadolinia (Gd₂O₃) fuels were studied. The behavior of fuel burnup, depletion of BN and B, the effect of coating thickness and also Gd₂O₃ content on the burnup performances of the fuels were found by using the code WIMS-D/5 for pressurized water reactor (PWR) and boiling water reactor (BWR) fuel assemblies. The optimum thickness ratio of B to BN was found as 4 and their thicknesses were chosen as 4 and 1 μm, respectively. Based on this observation, calculations were performed for the standard fuel assemblies with and without burnable poison and similar assemblies with BN-B hybrid coating with the desired BN-B thicknesses. Results are discussed to make an assessment of the effect of such hybrid coating on fuel cycle characteristics.     

Implanted boron profiles in silicon

¹⁰B and ¹¹B implants into amorphous Si, with energies ranging from 50 keV to 2 MeV and 10 keV to 1 MeV respectively, were profiled by the nuclear reactions ¹⁰B(n, α)⁷Li and ¹¹B(p, γ)¹²C. The projected range R_p and straggling ΔR_p agree within a few percent with recent calculations due to Ziegler, Biersack and Littmark (ZBL). These results show that the ZBL electronic stopping power is adequate to reproduce range parameters resulting from MeV implantations.     

Application of stable boron isotopes

This article presents a brief survey of the basic applications of stable boron isotopes as materials with an altered isotope composition in cases where the differences between the nuclear properties of boron isotopes are used directly. The neutron flux transformation into heavy ionizing particles by means of the B¹⁰ (n, )Li⁷ reaction and the large value of the effective thermal neutron cross section of this reaction make it possible to use B¹⁰ in medicine, nuclear studies, and radiation chemistry. The differences between the neutron cross sections of B¹⁰ and B¹¹ make It possible to use these isotopes in reactor construction and, in particular, to use B¹⁰ in materials for control rods and reactor shields.     

Interaction of tritium with boron carbide

Translated from Atomnaya Énergiya, Vol. 64, No. 6, pp. 441–443, June, 1988.     

Radioactive products from boron CTR reactions

The nuclear reaction rates for ¹⁰B(p, α)⁷Be and ¹⁰B(p, γ)¹¹C have been measured by a thick target technique using proton energies from 75 keV to 3.0 MeV. The results are valid for proton temperatures near 3 · 10⁹K where the ¹¹B(p, 3α) reaction has been suggested for power generation. At this temperature, the rates N_A〈συ〉 are 2.66 · 10₇ and 8.3 · 10² cm³ g^?1 s^?1 for ⁷Be and ¹¹C, respectively. As such, these rates suggest the possibility of serious radioactive contamination in using natural boron as a fuel in CTR devices.     

A renewed study of singly ionized boron

Some energy levels and lifetimes in B II have been studied using classical emission spectroscopy and beam-foil spectroscopy. Revisions are suggested for the excitation energies of the 2s3s ¹S and 2s5p ¹P⁰ levels. The 2p3s ¹P⁰ and 2s6p ¹P⁰ terms have also been located. Lifetimes have measured for the 2s2p ¹P⁰, 2p²¹S, 2s3d ¹D and 2p²³P levels. The results are compared with theoretical data.