Reactor radiation skyshine calculations with TRIPOLI-4 code for Baikal-1 experiments

Neutron and photon fluxes generated from the operation of fission reactors and fuel cycle facilities are normally well attenuated with the shielding and ceiling walls. However, skyshine dose rates were observed at 1.5 - 2 km away from the JCO criticality accident site at Tokai-mura. In this study reactor neutron and photon skyshine calculations of Baikal-1 experiments have been performed with the TRIPOLI-4 Monte Carlo transport code. Baikal-1 experiments were carried out with the 300 kW RA research reactor. The 85 cm thick concrete shielding plug in the upper direction of the RA reactor was removed during the experiments. Various distances up to 1500 m from the reactor were considered for skyshine radiation measurements. To study the neutron and photon skyshine dose rates off the reactor with TRIPOLI-4 code, both photon and coupled neutron-photon calculations were performed so as to include primary photons, primary neutrons, and secondary photons contributions. TRIPOLI-4 perturbation calculations on the ground density and on the hydrogen concentration contained in the ground composition were also applied to study the groundshine. (author)