BENCHMARK EXPERIMENT ON COPPER WITH D-T NEUTRONS FOR VERIFICATION OF SECONDARY GAMMA-RAY DATA IN JENDL-3.1

Copper is a very important material for fusion devices because it is u sed as material for the first wall and the superconducting magnet. Nuc lear heating of these components is a critical issue in the design of ITER. In order to verify secondary gamma-ray data in evaluated nuclear data libraries, a clean benchmark experiment on copper with D-T neutr ons was carried out at the FNS facility. Gamma-ray spectra and heating rates were measured at several points in a experimental assembly of 6 29 mm in diameter and 608 mm in thickness along with neutron spectra a nd reaction rates. The experiment was analyzed by using MCNP-4 and DOT -3.5 with cross-section libraries based on JENDL-3.1. It is pointed ou t from the results that the secondary gamma-ray data for threshold rea ctions is good. The probability of direct transitions in JENDL-3.1 fro m the capture state to the ground state for keV neutron capture should be increased. It is also found that energy balance of secondary gamma -ray data for the neutron capture reaction is inconsistent in an incid ent neutron energy range between 0.01 and 10 keV. Excess of released g amma-ray energy in JENDL-3.1 results in larger gamma-ray heating rates .