Dosimetric quantities

Draft document: Dosimetric quantities
Submitted by Raymond Kowe, NDAWG
Commenting on behalf of the organisation

NDAWG comments on ICRP foundation documents The National Dose Assessment Working Group (NDAWG) was established in the UK in 2002. The aim of NDAWG is to bring together people and organisations with responsibility for, and/or an interest in, the assessment of radiation doses from the operation of the nuclear industry and from minor users of radioactivity. Further information on the work of NDAWG, including the current membership, is available on the website, Members of NDAWG have considered the draft Foundation document of the International Commission on Radiological Protection (ICRP) as published on the ICRP website. The following set of comments represent the views of the majority of members but not necessarily the organisations that they represent. ICRP Committee 2, Basis for Dosimetric Quantities used in Radiological Protection, Draft of April 14, 2005. This is a will written document supporting the recommendations of ICRP. The use of reference values for anatomical and physiological characteristics and the averaging over both sexes ‘clearly show that the quantity effective dose is not designed to provide an individual dose value for a specific person considered but for a reference person or group’. We support the view that effective dose should be used predominantly for assessing exposure and controlling exposure in the low dose range for regulatory purposes (Section 5.4). However, we think that the ICRP are unduly restrictive in the final paragraph of Section 6 when they state that the ‘described reference values for models and parameters should be predominantly used for prospective radiological protection purposes’. It is valid to use effective dose retrospectively, for example when demonstrating compliance with a dose limit or dose constraint and when assessing doses associated with measured values. Important considerations are the level of the dose (well below thresholds for deterministic effects) and the purpose of the assessment but not whether it is prospective or retrospective. The discussion on uncertainties in Section 6 is helpful and we welcome the ICRP view that the reference models and values for determining doses from quantitative information about radiation fields and intakes of radionuclides should not be considered to be subject to uncertainty. However, there is also a need to inform interested individuals and groups of the magnitude of such uncertainties. The neglect of such uncertainties should be clearly tied to the requirement to demonstrate compliance with deterministic criteria, such as limits and constraints. It may be necessary to explore such uncertainties, to a degree commensurate with the magnitude of the assessed doses, to inform judgements on radiological safety. There may be circumstances where knowledge of local conditions might make it desirable to adopt conversion factors other than the ICRP reference values. Where such alternative approaches are used, there could be an encouragement to compare the results with the ICRP reference case and to justify any substantial differences that are identified.