Calculation of the Residual-Photon Dose Rate Due to the Activation of Concrete by Neutrons from a 3-GeV Proton Beam in Iron

Calculations have been carried out to determine the time dependence of the residual-photon dose rate inside an accelerator tunnel due to a 3-GeV proton beam located on the axis of an iron cylinder. The photon dose rate produced by the activation of the concrete tunnel wall is calculated and combined with the results from a previous calculation for the dose rate contributed by the iron to obtain the total photon dose rate inside the tunnel. The effectiveness of lowering the total photon dose rate by reducing the ²⁴Na production in the concrete is evaluated. The development of the nucleon-meson cascade, the residual nuclei production, and the photon transport are calculated using Monte Carlo methods.