Impact of the updated dose coefficients from the new radiation protection regulation

On December 20, 2022, Royal Decree (RD) 1029/2022 was published approving the new Regulation on protection for health against risks arising from exposure to ionizing radiation. The new RD replaces the earlier Regulation on health protection against ionizing radiation of RD 783/2001 previously in force. Accordingly, in its resolution of January 17, 2023, the Nuclear Safety Council set out new dose coefficients for external exposure in accordance with publications 116 and 144 of the International Commission on Radiological Protection (ICRP). These publications are based on the recommendations of publication 103 where, for the first time, emphasis is placed on the need to assess equivalent dose coefficients for different organs by using more detailed human models that take into account the particularities of each sex.

The purpose of this work is to assess the impact of the updated dose coefficients on typical radiological analyses carried out in the Radiological Protection Section at Empresarios Agrupados – GHESA.

Specifically, this paper analyzes the change in the coefficients for equivalent dose to the skin and effective dose with respect to the ones in RD 783/2001. It goes on to evaluate the differences in dose coefficients between different sexes, and then calculates their impact on the total dose for typical releases from effluents in normal and accident operation. To complete the analysis, the change in energy-dependent dose coefficients for photons and neutrons from ICRP 116 compared to those from ICRP 74 is evaluated, analyzing the impact on doses calculated with the SCALE 6.2.4 MAVRIC program for different sources and typical shielding configurations.

The difference in coefficients of equivalent dose to the skin between the two sexes depends on the path of external exposure and on the radionuclide considered. As a general conclusion, if the exposure is from a radioactive cloud or from immersion in water, coefficients for females are mostly higher than those for males. However, if the exposure is via deposits in soils, the trend is the other way around. The maximum differences between both coefficients are 5%.

In the examples analyzed to assess the impact of these changes in dose coefficients, it can be concluded that doses in normal operation and in accidents decrease when using the new coefficients from ICRP 144 instead of the coefficients featured in FGR 13, which was the reference used previously for these calculations. Nevertheless, it is important to highlight that this result depends on which isotopes are considered in the effluent inventory.

Doses due to radiation from photons remain equivalent whereas doses from neutrons go down, provided that shielding is used to lower the energy of the neutrons released by spent fuel.

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