VALIDATION OF INDUCED RADIOACTIVITY CALCULATIONS FOR CANDIDATE FUSIONMATERIALS THROUGH MEASUREMENTS IN A GRAPHITE-CENTERED ASSEMBLY

Induced radioactivity measurements were carried out jointly by the USA and Japan in a graphite-centered assembly, in the framework of ITER T ask T-218 entitled 'Shielding Blanket Neutronics Experiments'. An inte nse, accelerator-based D-T rotating target neutron source at JAERI, wi th a nominal intensity of 5 x 10(12) s(-1), was used. Two locations, p roviding different neutron energy spectra, were chosen for irradiating samples of a range of materials of interest to ITER. Three independen t experimental campaigns were conducted so as to accommodate a large n umber of samples, on one hand, and as many short and long half-life pr oducts as possible, on the other. The total neutron fluence ranged fro m 4.7 x 10(11) to 1.5 x 10(14) n cm(-2). Altogether, samples of Mg, Al , SiO2, Ti, V, Cr, Mn, Fe, Co, Ni, FH82 steel, SS316LN steel (ITER gra de), Cu, Zn, KCI, Zr, Nb, Mo, Ag, In, Sn, Dy, Ta, Hf, Re, Au, Ir, and Pb were irradiated. The irradiated samples were cooled for variable pe riods ranging from 30 s to 250 days before their decay gamma-ray spect ra were counted on high purity intrinsic germanium detectors. The half lives of the observed radioisotopes have ranged from 18.7 s (Sc-46m f rom Ti) to 5.3 years (Co-60 from Ni). The neutron energy spectra for t he two locations were calculated using Monte Carlo code MCNP with FEND L-1 and ENDF/B-VI data libraries. The analysis of isotopic activities, expressed in Bq cc(-1), of the irradiated materials has been carried out using REAC-3 radioactivity code, with FENDL-2A and FENDL-1A activa tion cross-section and decay data libraries. Typically, C/E lies in a band of 0.5-1.5 for the results being reported. (C) 1998 Elsevier Scie nce S.A. All rights reserved.