ALARA and Occupational Exposures: Experience and Challenges

1. ALARA and Occupational Exposures: Experience and Challenges J. Lochard ISOE International ALARA Symposium Tsugura, Japan, 13-14 November 2008

2. Content of the presentation • ALARA and the quest for reasonable : an historical perspective • From ICRP 60 to ICRP 103 • Trends in occupational exposures • Radiation risk at the workplace in perspective • Concluding remarks

3. First stage: prudence • Recognition of stochastic effects in the late 40s • "Taking into account uncertainties about the risk and the irreversibility of the effects, it is prudent to reduce exposures to the lowest possible level" (ICRP-1950) • The limit is not anymore a guarantee of the absence of risk

4. Second stage : justification • In a context of uncertainty taking a risk is justified only if their is a benefit in return • If there is a benefit • How far to reduce the risk without endanger the activity? • As low as practicable (ICRP 1-1958) • On which criteria to ground the decision?

5. Third phase: economic and social considerations • Recommendation to keep exposures as low as readily achievable, economic and social considerations being taken into account (ICRP 9 -1965) • The reduction of risk must be compared with the effort to achieve it • Need of quantification for practical application

6. ALARA: balancing costs and benefits • The adverb ‘readily’ is replaced by ‘reasonably’ (ICRP 22 -1973) • Introduction of the cost-benefit model • The decision process is reduced to a few parameters and focused on the avoided dose • Attempt to integrate social values in the quantitative framework (ICRP 37-1983)

7. Evolution of the ALARA principle wording

8. Beyond the cost-benefit model • ICRP 55 - 1988: Return to a more pragmatic approach: the ALARA Procedure • ICRP 60 - 1990: • Need to consider "the magnitude of individual exposures, the number of people exposed and the likelihood of incurring exposures where these are not certain to be perceived (= potential exposures)"in the optimisation process • Equity issue and the tolerability of risk model • Introduction of the dose constraint concept for practices to limit the range of options considered in the optimisation process

9. The tolerability of risk model Individual dose level Unacceptable risk Dose limit Tolerable risk Optimisation process ALARA level Acceptable residual risk

10. ICRP 101- 2005: broadening the process • Optimisation of protection is a forward-looking process aimed at preventing exposure before they occur • Optimisation is a frame of mind always questioning whether the best has been done in the prevailing circumstances • Consolidation of the previous publications and broadening the process "to reflect the increasing role of individual equity, safety culture, and stakeholder involvement"

11. The ICRP 60 system of protection (1) • Practices • Justification, optimisation, limitation (except for medical exposures) • Dose limits • Individual dose constraints • Interventions • Justification, optimisation • Intervention levels

12. The ICRP 60 system of protection (2) Practices Interventions "generic" optimisation Dose limit Dose constraint Action/intervention level Optimisation

13. The ICRP 103 system of protection (1) • Planned exposure situations:situations involving the deliberate introduction and operation of sources. • Justification, optimisation with dose constraints, dose limits (except medical exposures) • Emergency exposure situations:situations that may occur during the operation of a planned situation, or from a malicious act, or from any other unexpected situation, and require urgent action in order to avoid or reduce undesirable consequences. • Justification, optimisation with reference levels • Existing exposure situations:exposure situations that already exist when a decision on control has to be taken, including prolonged exposure situations after emergencies • Justification, optimisation with reference levels

14. The ICRP 103 system of protection (2) Emergency and existing exposure situations Planned exposure situations Dose limit Reference level Dose constraint Optimisation Optimisation

15. The individual levels of protection

16. Dose ranges in ICRP 103 for dose constraints and reference levels (1)

17. Dose ranges in ICRP 103 for dose constraints and reference levels (2)

18. The concept of dose constraint • The concept of dose constraint is used in conjunction with the optimisation of protection • A dose constraint is a source-related restriction on the individual dose from a source used prospectively in planned exposure situations which serves as an upper bound in the optimisation of protection from that source • The term “source” refers to any physical entity or procedure that results in a potentially quantifiable radiation dose to a person or group of persons • Dose constraints are defined at the design stage using past experience

19. Constraints and planned exposure situations • Occupational exposure • Usually set by operator • Small operators may need guidance from regulator • Transient/itinerant workers need special attention • Public exposure • Usually set by regulator

20. The tolerability of risk model Individual dose level Unacceptable risk Dose limit Tolerable risk Dose constraint Optimisation process ALARA level Acceptable residual risk

21. Occupational exposure: number of monitored workers (UNSCEAR 2008) Miscellaneous: educational establishment, veterinary medicine, transport… * Without natural radiation (NORMs)

22. Occupational exposure: annual collective dose (UNSCEAR 2008) Miscellaneous: educational establishment, veterinary medicine, transport… * Without natural radiation (NORMs)

23. Occupational exposure : annual average dose (UNSCEAR 2008 ) Miscellaneous: educational establishment, veterinary medicine, transport… * Without natural radiation (NORMs)

24. Occupational exposure: distribution of individual doses (ESOREX) Study on Occupational Radiation Exposure of Workers in Europe, ESOREX 2005 K. Petrova, G. Frasch, K. Schnuer, S. Mundigl

25. Occupational exposure in the nuclear fuel cycle (UNSCEAR 2008) NR15: fraction of workers with effective dose higher than 15 mSv.

26. Risk associated with ionising radiation - Adult workers - ICRP 103 (2007) Assuming 25 years at work at the limit of 20 mSv the lifetime risk of developing a cancer is increased by 2 %

27. Occupational exposures in electricity generation (PWR) Source: UNSCEAR 2008

28. Annual risk associated with the average exposure in PWRs • Annual risk associated with 1.7 mSv (late cancer after exposure using ICRP 103 coefficient): D = 1,7.10-3*4,2*10-2 = 7,14.10-5 • Annual risk of lethal occupational accident (immediate death): • France: 2.86.10-5 (2005), • USA: 4.10-5 (2006).

29. Detriment associated to radiation exposure and annual risk of fatal occupational injury 3,5 mSv 3,1 mSv 2,2 mSv 1,9 mSv 1,7 mSv 1,3 mSv

30. Radiation risk in perspective • The average level of radiation risk in the workplace is in the same order of magnitude than other risks for workers • The upper exposure levels, particularly those close to the limits, are significantly deviating from the main trends as far as quantitative risk estimate is concerned • Need to pursue efforts to reduce further the exposure of the most exposed workers in all domains = systematic implementation of ALARA

31. The way forward for further improvements in occupational radiation protection • Engaging a reflection on potential exposures (use of incident data basis) • Developing ALARA procedures and tools for dismantling operations • Sharing experience to diffuse the use of dose constraints • Enhancing radiation protection culture • Strengthening existing ALARA networks • Favouring stakeholders engagement in the decision making process • A remaining issue: the situation of transient workers

32. ALARA and dismantling in France • The first dismantling operations at French nuclear installations and NPPs have shown: • A lack of ALARA culture, notably at the level of the formalisation of the process • A weakness of dose estimations for the preparation of the work • A lack of reactivity of the teams when the first data become available at the beginning of the operations • Missing records concerning the description of the installations and their life time history • The non adaptation of "classical" technical procedures used for operation and maintenance • The lack of commitment and engagement of all concerned parties

33. The way forward for further improvements in occupational radiation protection • Engaging a reflection on potential exposures (use of incident data basis) • Developing ALARA procedures and tools for dismantling operations • Sharing experience to diffuse the use of dose constraints • Enhancing radiation protection culture • Strengthening existing ALARA networks • Favouring stakeholders engagement in the decision making process • A remaining issue: the situation of transient workers