Speaker
Description
Among the photo-nuclear reactions of light nuclides, the photo-disintegration of deuterium, $^2{\mathrm H}(\gamma,{\mathrm n})^1{\mathrm H}$, is arguably the most important one for nuclear systems with heavy/light water. In multiplying/critical systems, this reaction is also a source of delayed neutrons due to the delayed gamma emission of certain fission products. Therefore, it is important to review the modern evaluations of photo-nuclear reaction data of deuterium, their processability from the ENDF format into application specific ones (e.g., ACE), and from the standpoint of Monte Carlo neutron and gamma transport applications, the sampling of out-going neutron energy and direction by modern Monte Carlo codes. The necessary application of relativistic kinematics vs. non-relativistic limits in sampling of neutrons and protons will be discussed in detail. In addition, a comparison with the $^2{\mathrm H}({\mathrm n},2{\mathrm n})^1{\mathrm H}$ reaction will be made for completeness of the physics background of deuterium disintegration in the coupled neutron and gamma flux.
In studying the time-dependent phenomena in critical systems, a standard tool in nuclear engineering is the application of the point kinetic equations. Some Monte Carlo codes can be used to analyze time-dependent phenomena in neutronics without the assumption that the system of interest is a ``point'' in space. While feasible in theory, coupled neutron-gamma transport with the rigorous inclusion of photo-nuclear reactions is still practically beyond the reach of time-dependent Monte Carlo methods. However, similar to the point kinetics treatment of systems with heavy water/beryllium, extra delayed neutron groups can be added to the existing delayed group data of actinides (6 or 8 delayed groups), but the extra data blocks have to be prepared in the ENDF format. As a result, the treatment of time-dependent phenomena in heavy water systems with a time-dependent Monte Carlo method (and using nuclear data libraries in ACE format) will be possible, and time scale constrained by the delayed photo-neutrons can be reached. The problem of adding extra delayed neutron groups to the nuclear data files of actinides (e.g., $^{235}$U and $^{238}$U in ENDF/B-VIII.0 and JEFF-3.3) and post-processing/testing of the results will be discussed in detail. In addition, some interesting examples of modelling steady-state and time-dependent phenomena in the ZED-2 (heavy water) reactor at the Chalk River Laboratories (Canada) will be discussed from the standpoint of coupled neutron gamma transport and photo-nuclear data applications.