Central to applying the principle of optimisation in the system of radiological protection is the evaluation of what level of radiation exposure should be considered ���as low as reasonably achievable��� (ALARA) in a given circumstance. Determining what is ���reasonable��� is an abstract although somewhat intuitive concept with many potential answers depending on both the situation and those involved, whether individuals or organisations. There are common themes across exposure scenarios and within existing radiation protection guidance related to the determination of reasonableness. However, despite the fairly consistent and agreeable nature, there remains a gap in how to apply these themes in real situations. For example, without measurable goalposts (or a transparent process for setting such goalposts) for determining what constitutes ALARA, we can find ourselves misinterpreting the optimisation process as keeping exposures ���as low as possible.��� We thus propose herein, by consolidating and building on existing ideas, an easily understandable and actionable ���reasonableness��� framework. This simple, yet broadly applicable tool is intended to help radiation protection practitioners systematically reflect on all of the factors that make up ���reasonable��� before making a decision, although the process and decision itself will necessarily retain the complexity of the prevailing circumstance. The proposed ���Rs��� of Reasonable represent Relationships (stakeholders, transparency, and empathy), Rationale (contextual, scientific, and ethical justifications), and Resources (technology/technique, finances, time).

License: Creative Commons Attribution Non Commercial No Derivatives 2.5 Generic Funding: I would like to leave it blank.