Comparison of external dose coefficients used by the European Model for Inhabited Areas (ERMIN) and ICRP Publication 144

Hirouchi, Jun; Charnock, T.*

JAEA-Research 2023-013, 57 Pages, 2023/12

JAEA-Research-2023-013.pdf:2.28MB

The recent ICRP publication of dose coefficients for external exposures to environmental sources, ICRP Publ. 144, provided an opportunity to evaluate and improve the dose coefficients and dose conversion factors used by the European Model for Inhabited Areas (ERMIN). ERMIN contains several idealised built environments with the "open area" environment being very similar to the ICRP Publ. 144 "planar sources on and within the ground" situation. The study compares the values given in ERMIN with those derived from ICRP Publ. 144 for the external gamma dose coefficients, the dose conversion factors to convert from air kerma to effective dose and the beta dose coefficients. This study has enabled ERMIN to be improved in several ways. A new "open area" environment was developed based on ICRP Publ. 144. New dose conversion factors were developed moving from a single radionuclide specific one to nine that account for depth in the soil. The dose coefficients for Cs-137, Pr-143, Pr-144, Ru-106, Sr-89, Sr-90, Y-90, and Y-91 were significantly different between ERMIN and ICRP Publ. 144 because bremsstrahlung was not considered in ERMIN. 144, dose coefficients considering bremsstrahlung were developed using correction coefficients based on ICRP Publ. 144.

Influence of differences in model parameters observed in Europe and Japan, on the effective dose predicted by the European model for inhabited areas (ERMIN)

Hirouchi, Jun; Charnock, T.*

Proceedings of 14th International Conference on Radiation Shielding and 21st Topical Meeting of the Radiation Protection and Shielding Division (ICRS-14/RPSD 2022) (Internet), p.195 - 198, 2022/09

ERMIN (EuRopean Model for Inhabited Areas), which was compared and validated with other models by EMRAS II program, is a code that provides a module to two European nuclear accident decision support systems and calculates doses for people in inhabited areas contaminated by radionuclides. Parameters in ERMIN are principally based on observations after the Chernobyl accident. However, these parameters may differ among countries. In order to understand the uncertainty and variability of calculated doses when applying ERMIN elsewhere, it is important to investigate the degree of influence of each parameter on doses. Therefore, in this study, the parameters in Japan obtained by our literature surveys were compared with those used in ERMIN. We calculated doses using the values and uncertainties of those parameters and investigated the differences in doses and the influence of each parameter on doses. The results showed that the retention parameters, soil migration parameters, air exchange rate, and indoor deposition rate have a significant influence on the dose assessment.

Assessment of doses in contaminated urban areas; Modelling exercise based on Fukushima data

Takahara, Shogo; Charnock, T. W.*; Silva, K.*; Hwang, W. T.*; Lee, J.*; Yu, C.*; Kamboj, S.*; Yankovich, T.*; Thiessen, K. M.*

Journal of Radiological Protection, 42(2), p.020517_1 - 020517_13, 2022/06

https://doi.org/10.1088/1361-6498/ac7088

State-of-the-art dose assessment models were applied to estimate doses to the population in urban areas contaminated by the Fukushima Daiichi Nuclear Power Plant accident. Assessment results were compared among five models, and comparisons of model predictions with actual measurements were also made. Assessments were performed using both probabilistic and deterministic approaches. Predicted dose distributions in indoor and outdoor workers from a probabilistic approach were in good agreement with the actual measurements. In addition, when the models were applied to assess the doses to a representative person, based on a concept suggested by the International Commission on Radiological Protection (ICRP), it was evident that doses to the representative person obtained with a deterministic approach were always higher than those obtained with a probabilistic approach.