Effect of Photonuclear Reactions on the Photon Deep Penetration Problem for Buildup Factor Calculation

Photon deep penetration calculations were conducted to create a buildup factor database for a new point kernel code. The calculations included the effects of photonuclear reactions, which were not considered in previous buildup factor calculations, and the target energy was extended up to 30 MeV. For media with large photonuclear cross sections, the contribution of the neutron dose becomes significant. For example, in iron at 80 mean free paths, the total dose is 10²⁴ times larger than when the photonuclear reactions are not considered. On the other hand, it was found that if photonuclear reactions are ignored, the calculation results are not necessarily conservative in media with a significant neutron shielding capacity, such as water.