TG 114: Reasonableness and Tolerability in the System Of Radiological Protection: ICRP TG114 On-Going Reflections

The model of reasonableness and tolerability of radiological risk is a conceptual framework for the implementation of the ICRP principles of optimisation of protection (guided by constraints and reference levels) and application of dose limits, based mainly on the level of exposure, and closely related to the level of risk. Discussions about reasonableness and tolerability have been part of ICRP publications for many years, including the introduction of a model of risk tolerability in Publication 60. More recently, Publication 101 developed the approach to address the implementation of the optimisation process including the involvement of stakeholders and the way to elucidate what is reasonably achievable. Further considerations have been addressed while examining the ethic, identifying four core values underpinning the system of radiological protection (Publication 138). In 2019, ICRP has set up a dedicated task group (TG114) to review the historical and current perspectives on reasonableness and tolerability in order to consolidate and clarify Publication 103, and to prepare the considerations and basis needed for development of future recommendations.

The ICRP on-going reflections on reasonableness and tolerability in the system of radiological protection have started to addressed a series of questions including, for example: What is the link between tolerable and reasonable? What are the considerations and criteria on which the concepts of tolerability and reasonableness are based? What are some strategies to assist in balancing competing values in determining what is tolerable and/or reasonable?

For addressing these questions, the model of reasonableness and tolerability of radiological risk is revisited with the following objectives:

• Investigate the rational for the application of the tolerability of risk as well as the borders with unacceptable level of risks and compare with the approaches adopted for managing other risks.
• Better articulate the link between tolerability and reasonableness in the process of implementation the radiological protection system, with clarification on the criteria to be considered for defining “where we don’t want to go above” and which process could be put in place for evaluating “what is reasonable”.
• Refine the radiological criteria to be considered and their link with dose limits and reference levels, relying on the radiological detriment as benchmark for tolerability and reasonableness as well as using risk comparison but without limiting to numerical criteria.
• Emphasize the importance of the application of the model for the different exposure situations, including the deliberative process with the stakeholders for the implementation of the optimisation principle, referring to good judgement, fairness, practicability, and moderateness.

Presented by Thierry Schneider on behalf of the whole Task Group.