Nakamura T, Horiguchi H, Kishi T, Motohashi J, Sasajima F, Kumada H
Department of Research Reactor and Tandem Accelerator, Japan Atomic Energy Agency, Tokai, Ibaraki, Japan.
Appl Radiat Isot. 2011 Dec;69(12):1932-5. doi: 10.1016/j.apradiso.2011.05.015. Epub 2011 May 24.
The clinical trials of Boron Neutron Capture Therapy (BNCT) have been conducted using Japan Research Reactor No. 4 (JRR-4) at Japan Atomic Energy Agency (JAEA). On December 28th, 2007, a crack of a graphite reflector in the reactor core was found on the weld of the aluminum cladding. For this reason, specifications of graphite reflectors were renewed; dimensions of the graphite were reduced and gaps of water were increased. All existing graphite reflectors of JRR-4 were replaced by new graphite reflectors. In February 2010 the resumption of JRR-4 was carried out with new graphite reflectors. We measured the characteristics of neutron beam at the JRR-4 Neutron Beam Facility. A cylindrical water phantom of 18.6 cm diameter and 24 cm depth was set in front of the beam port with 1cm gap. TLDs and gold wires were inserted within the phantom when the phantom was irradiated. The results of the measured thermal neutron flux and the gamma dose in water were compared with that of MCNP calculation. The neutron energy spectrum of the calculation model with new reflector had little variation compared to that with old reflector, but intensities of the neutron flux and gamma dose with new reflector were rather smaller than those with old reflector. The calculated results showed the same tendency as that of the experimental results. Therefore, the clinical trials of BNCT in JRR-4 could be restarted.
硼中子俘获疗法（BNCT）的临床试验是利用日本原子能机构（JAEA）的日本研究堆4号（JRR - 4）进行的。2007年12月28日，在反应堆堆芯的石墨反射层焊缝处发现了一条裂缝。因此，对石墨反射层的规格进行了更新；减小了石墨的尺寸，增大了水隙。JRR - 4所有现有的石墨反射层都被新的石墨反射层所取代。2010年2月，JRR - 4使用新的石墨反射层重新启动。我们在JRR - 4中子束设施中测量了中子束的特性。在束流孔前方设置了一个直径18.6厘米、深度24厘米的圆柱形水模体，两者之间有1厘米的间隙。当水模体被辐照时，将热释光剂量计（TLDs）和金线插入水模体内。将在水中测得的热中子通量和γ剂量的结果与蒙特卡罗N粒子输运程序（MCNP）计算结果进行了比较。与旧反射层的计算模型相比，新反射层计算模型的中子能谱变化不大，但新反射层的中子通量强度和γ剂量强度比旧反射层的要小一些。计算结果与实验结果显示出相同的趋势。因此，JRR - 4中BNCT的临床试验可以重新启动。
