Verification of the Results of Benchmark Experiments on Measuring the Spectra of Neutron Leakage from the Surface of Iron Balls with Radionuclide Sources Placed Inside

At the present time with relation to the development of nuclear power and advancements in computer capabilities, the codes of ionizing radiation field calculation in the design and operation of nuclear power plants and other installations with applied nuclear sources have been improved. It is now feasible to solve complicated three-dimensional problems with more stringent requirements and to refine errors from the results obtained. The libraries of constants of neutron interaction with nuclei of various isotopes used in the calculations as a rule make the most appreciable contribution to refinement of these errors. These libraries take a long time to build, consisting of experimental measurement cross-sections of interactions of neutron with nuclei, their analysis and estimation and, finally, creation of the neutron constants libraries that need final experimental verification. The simplest geometry is chosen for such experiments. For this purpose the materials under investigation are formed in a ball, and small-sized radionuclide sources are used so that they may be modeled in the calculations by point and isotropic sources are located in the center of the balls. The selected geometry of experiments allows the energy distribution of neutron currents from a unit of sphere surface to be fairly reliably measured, and simple codes to be used in order to obtain their calculated values. The reliability of such benchmark experiments is often checked by means of additional calculations of their results with the use of codes and libraries of neutron constants showing good results in practice. The purpose of our work (with the results described in the paper) was a comprehensive substantiation of the results of earlier benchmark experiments on measuring the energy spectra of neutrons escaping from the surface of iron balls because iron is one of the main elements for structural materials used in nuclear power engineering. The benchmark experimental results validated in this way are assumed to be reliably used for the final check of improved or newly created systems of neutron constants.