Study on Hyper Thermal Neutron Irradiation Field for Neutron Capture Therapy

本研究的目的是通过实验和模拟计算，阐明超热中子对生物体的辐照特性，以及超热中子辐照场的可行性（平成8号），一个“试验型”超热中子发生器，是根据以模拟计算为主的基础研究结果设计的，并组装“高温散射体”部分。该发电机的设计目标是可达到的最高温度几乎为1200摄氏度（1500K）。从高温试验安全第一的角度出发，选用耐热、耐腐蚀性能好的不锈钢作为结构框架的主体材料。采用钼高温加热器电加热，钼热反射器散热，R型热电偶测温。选择石墨散射体是因为它的刺 ...更多信息 在高温下的能力。1997年（平成9年）制作了“控制器”部分，并与高温散射体部分组合，最终完成了发电机。在将发生器投入中子辐照场使用前，进行了发热试验。从试验结果可以确认，散射体的最高温度可达到1200 ℃，在高温使用时的热稳定性、热控制性和安全性没有问题。作为特性估算的实验之一，利用京都大学研究反应堆研究所（KURRI）的电子直线加速器（LINAC）中子发生器，通过飞行时间（TOF）方法估算了散射体温度对中子能谱的影响。还进行了模拟计算的估计。从实验和计算结果可以确认，中子温度随着散射体温度的升高而升高。目前，为了估算生物体中的中子剂量分布，正在计划在KUR（京都大学反应堆）重水装置上进行体模实验，假设将超热中子辐照应用于实际的NCT。少

The purpose of this research is to clarify the irradiation characteristics of hyper-thermal neutrons for a living body, and the feasibility of hyper thermal neutron irradiation field, by experiments and simulation calculations.In 1996 (Heisei 8), a "test-type" hyper-thermal neutron generator was designed from the results of the basic researches mainly with simulation calculations, and the "high-temperature scatterer" part was assembled. The design goal of this generator was that the attainable maximum temperature was almost 1200 degrees centigrade (1500K). From the standing-point of safety first at high-temperature experiments, stainless steal, which has good characteristics of heat-proof and corrosion-proof, was selected as main material of the structural frame. The electric heating using molybdenum high-temperature heaters, the heat remove by molybdenum heat reflectors, and the heat measurement by R-type thermo-couples were applied. Graphite scatterer was selected because of its stab … More ility at high temperature. The scatterer is possible to be replaced with the other scatterer.In 1997 (Heisei 9), the "controller" part was made and combined with the high-temperature scatterer part, and finally, the generator was completed. Before the employment of the generator at neutron irradiation field, the heating tests were performed. From the test results, it was confirmed that the scatterer maximum temperature was attainable to be 1200 degrees centigrade, and that there was no problem for thermal stability, thermal controllability and safety at the high temperature employment. As one of the experiments for the characteristics estimation, the neutron energy spectrum dependent on the scatterer temperature was estimated by TOF (time of flight) method using the LINAC (Electron Linear Accelerator) neutron generator at KURRI (Kyoto University Research Reactor Insitute). The estimation by simulation calculations were also performed. From the experiment and calculation results, it was confirmed that the neutron temperature shifted to be higher according to the scatterer temperature.At present, phantom experiment at the KUR (Kyoto University Reactor) Heavy Water Facility are planning in order to estimate the neutron dose distribution in a living body, on the assumption of the application of hyper-thermal neutrons irradiation to actual NCT. Less