Evaluation of an ADS lead target activation: Comparison of computations and measurements

The measurements and calculations have aimed at the verification of codes and data bases applied in modeling of transmutations in the spallation target and the resulting radioactivity. In experiments cylindrical Pb targets were exposed to the beam of 660 MeV protons. Using γ-spectrometry, a number of radionuclides were identified in Pb and Bi samples irradiated in the targets. Axial and radial distributions of several nuclides production rates were determined. Three types of the distribution shapes were distinguished: Bi isotopes, medium and heavier nuclides. The distributions of Bi isotopes reveal a sharp characteristic peak about 30 cm inside the target. The comparison of experimental results with calculations (MCNPX, FLUKA and LAHET) shows agreement within one order of magnitude, at the worst. Almost always the C/E ratio is between 3 and 1/3. However, no single code and/or reaction model yields good results for all examined nuclides.