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Optimisation of Radiological Protection in ICRP’s New Recommendations Stockholm, 7 December 2006

Optimisation of Radiological Protection in ICRP’s New Recommendations Stockholm, 7 December 2006 Lars-Erik Holm. The System of Radiological Protection. Types of exposure situations Types of exposure Identification of the exposed individuals

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Optimisation of Radiological Protection in ICRP’s New Recommendations Stockholm, 7 December 2006

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  1. Optimisation of Radiological Protection in ICRP’s New Recommendations Stockholm, 7 December 2006 Lars-Erik Holm

  2. The System of Radiological Protection • Types of exposure situations • Types of exposure • Identification of the exposed individuals • Source-related and individual-related assessments • The three fundamental principles of protection • Levels of individual dose that require protective action • Safety of radiation sources • Implementation

  3. Linear-no-threshold (LNT) Model … is the basis for: • Averaging and summing of doses • The concept of effective dose • The concept of collective dose • Individual dosimetry • Keeping dose records

  4. Summary of Radiation Risks • The nominal risk estimates are slightly smaller than in 1990, but in the same order of magnitude. • The overall risk of 0.05 Sv-1 (0.00005 mSv -1) continues to be appropriate for purposes of radiological protection.

  5. Principles of Protection Justification – Source related Optimization - Source related Dose limitation – Individual related

  6. Principles of Protection Justification – Source related Optimization - Source related Dose limitation – Individual related

  7. The Principle of Optimisation of Protection • In relation to any particular source, - the magnitude of individual doses, - the number of people exposed, and - the likelihood of incurring exposures where these are not certain to be received should all be kept as low as reasonably achievable, taking into account economic and societal factors.

  8. The Evolution of ALARA 1954: reduce exposures to the lowestpossible level 1959: keep exposures as low as practicable 1966: keep exposures as low asreadily achievableeconomic and social considerations being taken into account 1973: keep exposures as low as reasonably achievable economic and social considerations being taken into account 1977: keep exposures as low as reasonably achievable economic and social factors being taken into account 2007: keep exposures as low as reasonably achievable economic and societal factors being taken into account

  9. From Practices to Planned Situations ICRP is moving away from • a process-based protection approach to • a situation-based approach

  10. Practices and Interventions No procedural difference because in both cases, • There is a maximum level of dose above which the regulator will demand action • Optimisation of protection will reduce the level of dose at which action is taken • No action to further reduce doses below the optimised level of protection

  11. Types of Exposure Situations • Planned exposure: situations involving the planned introduction and operation of sources, incl. medical exposure of patients, decommissioning and waste disposal • Emergency exposure: unexpected situations that occur during the operation of a planned situation, or from a malicious act, requiring urgent action • Existing exposure: situations that already exist when a decision on control has to be taken, incl. natural backgroundradiation and residues from past practices

  12. Reference Levels and Dose Constraints = Values above which one plans not to go, and below which one strives to reduce all actual doses Planned exposure: Dose constraint Diagnostic reference level Emergency exposure: Reference level Existing exposure: Reference level

  13. Reference Levels and Dose Constraints • Apply to all situations - The value will depend on the circumstances • An integral part of prospectively optimising protection at the source • If a relevant constraint or reference level was not complied with - Further protection options must be considered - Not necessarily a failure of protection

  14. The Use of Dose ConstraintsPLANNED EXPOSURE SITUATIONS • For planned situations: a basic level of protection, less than limits • Set for each source to ensure that the dose limits are not exceeded

  15. Establishing Dose ConstraintsPLANNED EXPOSURE SITUATIONS • For occupational exposure: typically set by operators or, for small companies, by regulatory authorities • For public exposure: typically set by regulatory authorities • For patients’ comforters and carers: typically set by the medical profession

  16. The Use of Reference LevelsEMERGENCY AND EXISTING EXPOSURE SITUATIONS • Prospectively as a level of ambition • Retrospectively for assessing the effectiveness of protection • Not as a mandatory level that must be achieved

  17. Dose Constraints and Reference Levels

  18. Characteristics of Existing Situations • Large distributions of individual exposures • Often affecting places of living • Sometime difficult to control (most often mainly controllable through pathways) • Time is a key parameter (step by step approach) • In many cases, the level of exposure is driven by individual behaviour

  19. Evolution of the Individual Dose Distribution with Time Step 1 Step 2 Step 3 No. of individuals Reference level Individual dose level

  20. Publications 60 and 63 • INTERVENTION and no action below ACTION LEVELS • Recommend values for the AVERTED dose for SINGLE countermeasures where intervention is almost always justified: • Sheltering • Administration of stable iodine • Evacuation • Relocation • Restriction to a single foodstuff ICRP 2007 OPTIMISATION below REFERENCE LEVELS Recommends an upper value of the PROJECTED dose (= reference level) received via ALL pathways below which optimisation is applied.

  21. Application of Reference Levels Prospective Preparedness Retrospective Response Focus particular attention on this part of the dose distribution Select Option B Dose distribution for which planned protection strategy has been implemented Option C Option A Reference level Option B Dose distribution after further optimised protection strategies, if any, have been applied Optimise

  22. Optimisation Below Reference Levels • Consider each option of a protection measure on its own merits. • Consider simultaneously doses that would be incurred via all exposure pathways, some subject to protective actions and some not. • If the total residual dose to some individuals is unacceptablyhigh, the feasibility of additional protective measures should be considered.

  23. Reference level mSv/yr 100 10 1 Time Early Intermediate LatePhase

  24. Conclusion – Reference Levels • Basically, the same approach as for constraints in planned situations: • Characterizing the exposure situation • Setting a level of ambition (reference level) • Optimizing protection taking into account the prevailing circumstances • Iterative process for implementing optimisation • General improvement of the quality of protection for existing and emergency situations

  25. The System of Radiological Protection in the 2007 Recommendations • Emphasizes a strong radiation safety culture through iterative review and assessment to optimise radiation doses • Optimisation involves evaluating and incorporating measures that tend to lower doses to workers, the public or patients • Optimisation also entails consideration of avoidance of accidents and other potential exposures

  26. Optimisation of Protection • The optimisation is a forward looking iterative process aimed at preventing exposures before they occur. • Optimisation is the responsibility of the operating management, subject to the requirements of the authority. • An active safety culture supports the successful application of optimisation by both the operational management and by the authority.

  27. Optimisation of Protection • All aspects of optimisation cannot be codified; optimisation is more an obligation of means than of results. • The authority should focus on processes, procedures and judgements rather than specific outcomes. • An open dialogue must be established between the authority and the operating management to ensure a successful optimisation process.

  28. Practical Implications OPERATIONAL MANAGEMENT • Develop and provide internal policies, priorities, rules and procedures, to • Ensure the existence of a safety culture at all levels of management and the workforce COMPETENT AUTHORITIES • Establish clear policies and processes for decision-making regarding the authorisation of proposed activities • Regulatory requirements should include the need for an active safety culture in both authority and operating management.

  29. The Optimisation Process Evaluation of exposure situations to identify the need for action Optimisation is a forward-looking iterative process aimed at preventing exposures before they occur. Measurement of performances Identification of protection options Selection of the best option under the prevailing circumstances Implementation of the protection option TG OPIMISATION of PROTECTION

  30. The Collective Dose For decision-aiding, more information is often necessary, e.g. for the workforce: • Number exposed, mean dose, dose range, task-related dose, etc. • When, where, how and by whom are exposures received? For decision-making, it may be reasonable to give more weight to doses that are • Moderate or high • Received in the near future

  31. Examples of Dose Weighting

  32. Selecting Protection Options QUANTITATIVE TOOLS Methodology and tools were developed in the 1980s to compare protection options with multi-attributes and characteristics taking into account ethical, social and economical considerations.They are still valid. ICRP warns against an application of these techniques alone. TG OPIMISATION of PROTECTION

  33. Optimisation and BAT • For the control of radioactive emissions to the environment the principle of the best available technology, not entailing excessive costs (BAT), may be used. • The principles of optimisation and BAT complement each other. • The control of exposures in relation to health will be driven by the optimisation of estimated radiation doses.

  34. Optimisation and BAT • Optimisation assumes an object of protection and a defined detriment of radiation exposure. • An optimisation cannot be carried out as simply when the benefit and detriment cannot be quantified, e.g. in connection with a future release • the probability is difficult to define • the consequences for the environment cannot be quantified using the collective dose. • BAT can be used to achieve a high level of protection without quantification of these parameters in greater detail.

  35. Optimisation and BATTHE CASE OF SPENT FUEL REPOSITORY • The difficulty of predicting the future development of society makes optimisation difficult • We do not know what the biosphere will look like • A minor release is better than a major release, even if the society which is affected is unknown. Therefore, the barrier system must be as robust as possible. • Repository barriers fulfilling reasonable safety requirements can be said to meet the BAT requirement.

  36. Optimisation and BAT

  37. Practical Application of Optimisation and BAT • Optimisation is a tool to minimise risk using risk (or dose) calculations • BAT aims to hinder, limit and delay releases as far as reasonably possible • Optimisation and BAT are important regulatory (societal) tools for ensuring an attitude of doing as good as reasonably possible

  38. Time Schedule • December 2006: Main Commission working on final draft of the new recommendations • January 2007: The draft will be put on ICRP’s website as a progress report. • March 2007: Adoption of the new recommendations

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