  The radiobiological effect on the human health of CANDU spent fuel is
assessed using Monte Carlo shielding estimates. The examination of spent fuel
occurs after it has been discharged from the reactor. A specific cooling
interval is considered, with the radiation dose rates that characterize the
used fuel being of interest. Two kinds of fuel were studied in a CANDU standard
fuel bundle with 37 fuel components: natural uranium (NU) fuel and slightly
enriched uranium (SEU) fuel. The fuel burnup was simulated using the ORIGEN-S
algorithm, and the photon sources describing the wasted fuel were retrieved. A
generic stainless steel shipping cask type B was used for spent fuel transfer,
and radiation doses at the cask wall and in the air up to 8 m away from the
shipping cask were computed using the Monte Carlo MORSE-SGC algorithm. To
ensure nuclear safety and radiation protection, spent fuel must be maintained
in temporary wet cooling storage for six months. The projected dosage rates
were modest, allowing for the safe handling of the used fuel shipping cask. The
corresponding dosages on human body organs for the two considered spent fuels
were estimated without and with shielding. Due to the varied sensitivity and
reaction of organs/tissue, the effective dosage was evaluated for the human
body by applying a tissue-weighting factor; these weighting factors are not
equal, and functional coefficients specified by ICRP are used. The equivalent
doses calculation modeling findings for the present study underlined the
complete effectiveness of the applied shielding and attained the acceptable
dose level.
