Workshop on Optimisation: Rethinking the Art of Reasonable

NEA Workshop on Optimisation: Rethinking the Art of Reasonable

13-15 January 2020
Lisbon, Portugal

Hosted by Instituto de Oncologia de Lisboa-Francisco Gentil (IPOLFG) and Instituto Superior Técnico Centro de Ciências e Tecnologias Nuclerares (IST/C2TN)


Over the past 15 to 20 years, the optimisation of radiological protection has gone from being just one aspect to being a major focus of international recommendations. This is true of recommendations from the International Commission on Radiological Protection(ICRP), of requirements from the International Atomic Energy Agency (IAEA) and of Directives from the European Commission (EC). As a result of this evolution, optimisation has become a more significant part of national regulations in many countries around the world. Doses should thus be kept “as low as reasonably achievable” (ALARA), taking into account both social and economic aspects. In practice, however, the optimum protection solution can be difficult to identify.

One factor that has made this identification difficult may be that societal interest in decisions addressing public health issues has greatly increased, and as a result stakeholder involvement has become a significant factor in decision making. Yet, in the practical sense, it is not always obvious which stakeholders should be involved – and to what extent – in decision-making processes that identify and implement optimal protection. Neither is it evident who should decide what protection option to implement. In some circumstances, stakeholder involvement has resulted in the implementation of an optimisation decision that is in fact closer to dose minimisation than to the optimisation of protection.

While it is generally well understood in the radiological protection community that the optimisation concept is not equivalent to minimisation – this is stated clearly in international recommendations such as ICRP 103 – conservative choices nonetheless tend to be the norm in practice. This norm is partly driven by uncertainty in relation to the effects of low levels of radiation exposure. While epidemiological science and data suggest that the linear no-threshold (LNT) assumption fits well with existing human and animal exposure effects data, exposures that could lead to statistically significant, adverse health effects are nevertheless typically above the doses received by most radiation workers, and well above the doses experienced by the public. Biological studies of the effects of radiation provide some evidence that low doses may not lead to adverse effects, but at the same time studies have not yet fully explained complex cellular repair and damage mechanisms, and they cannot yet resolve the issue of what level of exposure can cause damage.

The precautionary principle is thus frequently evoked in the face of such uncertainty, which has in turn lead to conservative protection decisions — indicating that, as suggested by the LNT assumption, any exposure, no matter how small, carries a proportionate risk.

.    ICRP (2007), The 2007 Recommendations of the International Commission on Radiological Protection, ICRP Publication 103, Ann. ICRP 37(2-4),

LNT issues

The LNT assumption is used by regulatory agencies around the world as the basis for the practical management of radiological exposure. Some experts feel that because the system of radiological protection makes use of the LNT assumption and does not establish an exposure level below which it is “safe” (i.e.there is no risk), the reaction of the general stakeholder is generally one of fear because any exposure is in fact dangerous. For this reason, some experts feel that a threshold model, rather than the LNT model, would better address the fearful and overly prudent views of stakeholders.

The science behind radiological risk assessment continues to evolve, and the practical approach to addressing scientific uncertainty in risk assessment has continued to give rise to debate for many years. There has been little movement towards resolution of these conflicting views, and no emergence of a clear regulatory model that would serve as an alternative to LNT.

A 2018 meeting organised by the American Nuclear Society and the American Health Physics Society brought together radiological protection officials, epidemiologists, biological researchers and other experts from around the world to discuss the current scientific understanding of radiation effects and practical approaches to the implementation of optimisation. As discussed at that meeting, the assumption that any dose carries a risk has in many circumstances – including in waste management, clean-up end-state selection, or the consideration of operational effluents – resulted in the choice of optimising protection solutions that can be viewed as extremely conservative in absolute terms. Whether resources are being used optimally has become a significant question, further demonstrating the need to develop a broadly accepted practical approach to how the exposure to low levels of radiation should be managed and regulated.

Prevailing circumstances

In the context of radiological protection decision making, the prevailing circumstances refer to any aspects that could or should be taken into account by the decision maker as part of the decision-making process. In fact, however, the prevailing circumstances provoke the need for radiological protection decisions, and form the situational framework that will drive decision makers to make choices.

Since decisions are made by governments and regulators, engagement with stakeholders is an essential element in understanding how prevailing circumstances should be balanced with the desire to minimise exposure. In addition to radiological aspects (e.g.exposure scenarios, protection options, residual doses, dose distributions), decisions must reflect other public health risk factors, economic aspects and social aspects ( disruption and/or stress, social structure disruption).

For example, in post-accident situations the broader community will have views not necessarily based on scientific analyses, nor on governmental choices that have been made to indicate where the community is  authorised to live, what it is authorised to eat and where it is authorised to work. These societal views cannot be ignored when decisions are being made. In addition to providing input into regulatory or governmental decisions, stakeholders will, in a practical sense, take actions based on their understanding of the situation — for example, members of the public affected by an accident situation may evacuate during an accident and later decide to return home when allowed to do so, or they may choose to move away permanently. Attempts should therefore be made to understand societal views and realities as the decision-making process proceeds.

Decision making

Radiological protection decisions are informed by science but are based largely on a judgement as to which level of protection is “reasonably achievable”. The science of radiological protection continues to evolve and advance, but it does not seem likely that it will quickly and definitively resolve the issue of which level of exposure can cause harm. The need to take radiological protection decisions nonetheless remains, and input is needed to help ensure that protection choices are indeed reasonable. In practice, taking a broad view of assessing and balancing responses to the risks associated with any particular prevailing circumstance can be very difficult to achieve. To help address such situations in a better and more objective manner, the Nuclear Energy Agency (NEA) Committee on Radiological Protection and Public Health (CRPPH) has organised the “NEA Workshop on Optimisation: Rethinking the Art of Reasonable.”


The objective of this workshop is to identify a regulatory and practical approach for assessing radiological protection circumstances and for developing, with appropriate stakeholder participation, the best radiological protection choices under prevailing circumstances.

Young professional participation

Sessions 4, 5 and 6 will highlight the participation and views of young professionals, who will be tomorrow’s radiological protection leaders. To appropriately prepare for these sessions, students and young professionals have been identified in advance, through the International Radiation Protection Association (IRPA) young professionals’ group. Pre-workshop discussions brought together young professionals via webinar to present workshop expectations and to propose topic areas and approaches, as well as possible future directions for framework evolution. The materials presented will be refined to better represent modern approaches, and will be used in Session 6, particularly, in order to develop results.

The path forward

The intention of this workshop is to identify areas where a broader vision of the implications of decisions could facilitate a more widely accepted and sustainable path forward for circumstances that require radiological protection decisions. It is hoped that such discussions will lead to an evolution in terms of how the implementation of the current radiological protection framework is interpreted, while providing direction in the steady evolution of international recommendations and standards. This evolution may include:

  • initiating broad and institutional discussions on how “reasonableness” is understood and on processes to identify “reasonable” protection decisions;
  • studying the situation-specific consequences of radiological protection decisions;
  • identifying approaches to agree on numeric and other decisional criteria;
  • outlining radiological and non-radiological, situational and decisional aspects to consider in regulation and application;
  • determining the extent to which the evolution of optimisation implementation can be easily achieved in practice, and consequently, the longer-term framework evolution that would then be needed.

Poster session

A poster session, particularly addressed at students and young professionals, will be held in-between sessions and during breaks. Students and young professionals will be encouraged to submit posters addressing aspects presented above.


The workshop is taking place in Lisbon, Portugal, and is being hosted by the Service de Radiologie, Institut Portugais. The workshop is being held at the Portuguese Institute of Oncology.

Time frame

This three-day workshop was scheduled from 13 to 15 January 2020.


The result of the workshop will be a short report on the regulatory and practical framework needed to identify acceptable and sustainable radiological protection choices and important aspects to consider in a variety of prevailing circumstances. This report will underline that:

  • prevailing circumstances, understood in the broad sense, will create and drive stakeholder concerns of all sorts;
  • protection decisions to address radiological situations and stakeholder concerns will carry consequences, both positive and negative. All such consequences should be assessed in order to make the optimum protection choice. A broad understanding of the consequences of protection options (whether radiological, political, social, economic, individual, local, regional or national) is needed in order to thoroughly balance the possible options and appropriately identify the full repercussions of such options;
  • A broad, all-hazards approach should be used to characterise the prevailing circumstances as best as possible so as to help ensure that all of the relevant aspects of decision consequences are evident and can be judged in terms of their importance and relevance.

Questions used in breakout sessions

The case studies presented during Sessions 3 and 4 addressed finding the optimum protection solutions for the prevailing circumstances listed below. Each breakout session group is invited to address the following questions for each of the prevailing circumstances listed below and addressed by the case studies:

  • NPP under normal operation
  • NPP under decommissioning
  • nuclear or radiological emergency management
  • nuclear or radiological recovery management
  • post-accident food and drinking water management
  • radiological waste management
  • legacy waste management
  • NORM and radon management
  • Who are the stakeholders that need to be involved, in some manner, in decision-making processes to identify and implement optimal protection?
  • Who is the decision maker?
  • What type of concerns are stakeholders likely to have with regard to the prevailing circumstances and residual exposures following the implementation of optimal protection solutions?
  • What regulatory requirements impact the identification and implementation of optimal protection solutions?
  • Where are protection options, aspects, criteria, or other factors most likely to be conservative in nature?
  • What type of approach(es) to stakeholder engagement would best address stakeholder concerns?
  • What aspects of identifying and implementing optimal protection solutions are likely to support achieving accepted, sustainable decisions?