MEASUREMENT OF LOW-ENERGY NEUTRON-SPECTRUM BELOW 10 KEV WITH THE SLOWING-DOWN TIME METHOD

No general-purpose method of neutron spectrum measurement in the energ y region around eV has been established so far. Neutron spectrum measu rement in this energy region was attempted by applying the slowing dow n time (SDT) method, for the first time, inside two types of shield fo r fusion reactors, type 316 stainless steel (SS316) and SS316/water la yered assemblies, incorporating with pulsed neutrons. In the SS316 ass embly, neutron spectra below 1 keV were measured with an accuracy less than 10%. Although application of the SDT method was expected very di fficult for SS316/water assembly since it contained lightest atoms of hydrogen, the measurement demonstrated that the SDT method was still e ffective for such shield assembly. The SDT method was also extended to thermal flux measurement in the SS316/water assembly. The present stu dy demonstrated that the SDT method was effective for neutron spectrum measurement in the energy region around eV.