Evaluation of potential induced radioactivity in medical products as a function of electron energy in electron beam sterilization

Commercial sterilization of medical devices may be performed using electron beam irradiators at various electron energies. The potential for activating components of the devices has been discussed, with current standards stating that electron energy greater than 10 MeV requires assessment of potential induced radioactivity. This paper evaluates the potential for induced activity in medical products sterilized in electron beam as a function of the electron maximum energy. Monte Carlo simulation of a surrogate medical device was used to calculate photon and neutron fields resulting from electron irradiation, which were used to calculate concentrations for several radionuclides.The experiments confirmed that 10 MeV is a conservative assumption for limiting induced radioactivity. However, under the conditions as evaluated, which is a limited total quantity of metal in the material being irradiated and absent a limited number of elements; the amount of induced activity at 12 MeV could also be considered insignificant. The comparison of the sum-of-fractions to the US Nuclear Regulatory Commission exempt concentration limits is less than unity for all energies below 12.1 MeV, which suggests that there is minimal probability of significant induced activity at energies above the 10 MeV upper energy limit.

► This study estimates induced radioactivity for electron irradiation as a function of energy.
► MCNPX was used to model systems from 8 MeV up to 13 MeV.
► Under conditions given, energies up to 12 MeV may create insignificant activation.
► Measured concentrations were within a factor of two of those calculated.
► Depth dose profiles show good agreement with the model.