Study on remodeling the heavy water facility of the Kyoto University reactor for neutron capture therapy from the concept of neutron energy spectrum control

In August 1988, there was heavy water leakage from the thermocouple guide pipe of the heavy water tank adjacent to the core of the Kyoto University Research Reactor (KUR). The need for a fundamental reexamination of the Heavy Water Thermal Neutron Facility (HWTNF) has been recognized since the guide pipe was repaired. Clinical irradiation was restarted in February 1990, and as of September 1, 1992, 24 clinical treatments had been carried out. Some improvements for the clinical treatment have been requested by clinicians and other users, especially the ability to use the facility while the reactor is in continuous operations. From the viewpoints of reactor engineering and medical physics, there are four goals for remodeling the present HWTNF: (1) to simplify and secure maintenance, overhaul, and repair, (2) to enable the facility to be used during continuous operation of the KUR, (3) to improve the performances of the irradiation field of thermal neutrons for biomedical uses, and (4) to control neutron energy spectrum. In this paper, an outline for the redesign of the facility is reported