Study on Hyper Thermal Neutron Irradiation Field for Neutron Capture Therapy

1997 Fiscal Year Final Research Report Summary

• Project/Area Number: 08458125
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: エネルギー学一般・原子力学
• Research Institution: KYOTO UNIVERSITY
• Principal Investigator: KOBAYASHI Tooru Kyoto University, Research Reactor Institute, Associate Professor, 原子炉実験所, 助教授 (90089136)
• Co-Investigator(Kenkyū-buntansha): SAKURAI Yoshinori Kyoto University, Research Reactor Institute, Research Associate, 原子炉実験所, 助手 (20273534)
• Project Period (FY): 1996 – 1997
• Keywords: Neutron Capture Therapy / Hyper Thermal Neutron / High Temperature Scatterer / Graphite / Beryllium / Zirconium Hydride

Research Abstract

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 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.