Precision Measurements of {sup 56}Fe Cross Sections for the 847-keV Gamma Transition

At the First Research Coordination Meeting of the IAEA/NDS CRP on Measurement, Calculation and Evaluation of Photon Production Data an experiment to measure with high precision the cross sections of the production of the 847-keV gamma ray due to inelastic neutron scattering with iron was proposed and discussed. The main justification for the proposed improved precision was the need for improved calculations of radiation transport through thick iron components of nuclear reactors. Present evaluated data for the subject reaction in the ENDF/B-VI files have evaluated uncertainties {approx} 10%; consequently, the results of computation of deep penetration of radiation in iron can have quite large uncertainties -- larger than 100%, for example, for an attenuation of {approximately} three orders of magnitude -- which can be a serious problem when one considers the magnitude of the radiation field inside a pressure vessel. This report describes progress toward obtaining more precise data. 13 refs., 1 fig