Measurements of gamma-ray heating in lithium-oxide, graphite and iron slab assemblies bombarded by D—T neutrons

Abstract

Measurements of the γ-ray heating rate distribution were made in simulated fusion blanket assemblies using thermo-luminescent dosimeters (TLD). The interpolation method, which needs to knowledge of the γ-ray spectrum, was applied using four kinds of TLDs ( 7 LiF, Mg 2 SiO 4 , Sr 2 SiO 4 , and Ba 2 SiO 4 ). To subtract the neutron contribution from the total dose, we calculated the neutron responses of these TLDs by a computer code based on the kerma calculations. Neutron responses of these TLDs were measured at two energy points using FNS at JAERI and FNG at ANL in order to examine the validity of the calculated results. The measurements were performed for lithium-oxide, graphite and iron slab assemblies bombarded by D—T neutrons. The overall experimental error was about 20 – 30%. It is suggested that development of new TLDs of low Z and low neutron sensitivity is desirable. The experimental results were compared with the calculated ones with the transport code DOT3.5 and two coupled neutron and γ-ray cross section sets GICX40 and GICXFNS to test the secondary γ-ray production cross section. It is shown that the accuracy of the calculational prediction of γ-ray heating is quite insufficient.