The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) is the Australian Government’s primary authority on radiation protection and nuclear safety. ARPANSA protects the Australian people and the environment from the harmful effects of radiation through understanding risks, best practice regulation, research, policy, services, partnerships and engaging with the community.
- ARPANSA welcomes the approach by the ICRP to fill an existing gap by publishing dose coefficients for external exposure. ARPANSA relies on evidence based approaches, such as this document, to provide a basis for dose assessments. This was an area that ARPANSA previously relied on other documents, such as FGR12 or published journal articles, to complete assessments.
- Is the air kerma and ambient dose equivalent calculated for each radionuclide in the electronic supplement tables?
- Some discussion on the differences between this document/methodology/values in comparison to recently released FGR15 would be beneficial in the introduction (or as an annex). In the past ARPANSA has relied on FGR12 for this information and was considering updating to FGR15.
- The focus in this document is on soil, and the lowest depth soil includes a ground roughness factor to reduce the exposures by around 0.7 for Cs137. Could some comment be made on the applicability of these factor for urban environments, where surface roughness is different. Would paved areas or asphalt offer the same ground roughness shielding as agriculture or grassed areas? Perhaps one of the radionuclide tables could assume no shielding due to the ground surface.
Specific Comments
- Definitions: Air Kerma could be added to this section.
- P8 L428. Change the word soil to ground. This is a broader definition that would cover other surfaces such as an urban environment.
- P8. Consider using a time dependant migration factor for external exposure. This is used for calculating operational intervention levels in recent IAEA documentation (IAEA 2017).
- P9. It could be made clearer that using these values close to the release point where plume is narrow can lead to overestimates of the external dose.
- P15. A brief explanation of the difference of infinite and semi-infinite sources would be useful in this section. It is explained later in documentation, but may be worthwhile expanding here as well.
- P18. Is it possible to provide additional tables (or modifying factor) for newborn and 1 year old being on the ground rather than in an upright posture? IAEA (2017) OIL documentation used the FGR12 values and then added a simple modifying factor for converting from Adult to Child and assumed the child was on the ground.
- P71 L1127-1129. This section is unclear. The relationship of air kerma to air density is shown in Figure 5.6. However, does the statement in L1129 refer to the air kerma rate coefficient as shown in Table 6.7 column 9? If this is the case L1129 should read ‘….kerma decreases with increasing density’. Or, is this describing the relationship when converting from air kerma to effective dose? If this is the case, then the statement may be correct, however wouldn’t the effective dose rate also decrease with increasing density?
- Figure 5.5. What is the significance of the two figures on the right? The description should indicate which figure each sentence is referred to, e.g. left, top right, bottom right.
- Tables 6.1 to 6.6 and 8.1 to 8.7 should be added to the electronic supplement rather than being part of the document. The figures in section 6 provide the same information as tables 6.1 to 6.6. As an end user the radionuclide specific tables that should be in the annex are much more important.
- An example calculation could be added to the annex, or as part of the electronic supplement. See FGR15 Appendix D pages 319-323
References
IAEA (2017) – Operational Intervention levels for reactor emergencies and methodology for their derivation. EPR-NPP-OILs.
FGR12 (1993) – External exposure to radionuclides in air, water, and soil.
FGR15 (2018) – External exposure to radionuclides in air, water, and soil.