1. Optimization in ICRP Recommendations
Experience and New Developments in Implementing ALARA in Occupational, Public and Patient Eposures
Optimization in ICRP Recommendations
- Broadening the Process
10th European ALARA Network Workshop
Prague 12 September 2006
Lars-Erik Holm
Chairman of ICRP

2. ICRP’s 2006 Recommendations
The Commission has decided to issue the revised recommendations having three primary aims in mind:
To take account of new biological and physical information and of trends in the setting of radiation safety standards;
To improve and streamline the presentation of the recommendations; and
To maintain as much stability in the recommendations as is consistent with the new scientific information.

3. There is more continuity than change!
What Is New?
There is more continuity than change!
Most recommendations will remain - because they work
and are clear.
Some recommendations are to
Be explained - because more guidance is needed;
Be added - because there has been a void; or
Differ - because understanding has evolved.

4. The System of Radiological Protection
Types of exposure situations;
Types of radiation exposure;
Identification of the exposed individuals;
Source-related and individual-related approaches;
The three fundamental principles of protection;
Levels of individual dose that require protective action;
Conditions for the safety of radiation sources; and
Implementation of the recommendations.

5. Linear-no-threshold (LNT) Hypothesis
… is the basis for:
Averaging and summing of doses
The concept of effective dose
The concept of committed and collective dose
Individual dosimetry with integrating detectors
The system of keeping dose records

6. The System of Protection - Major Features
Maintaining the fundamental principles of radiological protection, and clarifying how they apply to sources and the individual;
Updating the weighting factors and the detriment;
Maintaining the dose limits;
Extending the concept of constraints in the source-related protection to all situations.

7. Nominal Risk Coefficients for Stochastic Effects (% Sv-1)
Exposed population
Cancer
Heritable effects
Total
1990
2006
Whole
6.0
5.5
1.3
0.2
7.3 6
Adult
4.8
4.1
0.8
0.1
5.6 4

8. Summary of Radiation Risks
The nominal risk estimates are now slightly smaller than in 1990, but the risk is in the same order of magnitude as before.
The overall risk coefficient of 0.05 Sv-1 continues to be appropriate for purposes of radiological protection.

9. Tissue Weighting Factors , wT
Take account of
- Cancer incidence
- DDREF
- Different populations
- Lethality, quality of life, and years of life lost
Normalise to unity
Bin into 4 groups broadly reflecting relative detriments

10. The Use of Effective Dose, E
For compliance of constraints and dose limits to control stochastic effects
Mainly for planning in prospective situations
Not for detailed retrospective dose and risk assessments after exposure of individuals
Not for epidemiological studies

11. Practices and Intervention in ICRP 60
Optimization
Intervention Level
Limit
What happens below the intervention level?
No further optimization?
Constraints
Optimization

12. Are Practices and Interventions Different?
In both cases:
There is a maximum level of dose above which the regulator will demand action;
Optimization of protection is seen to reduce the level of dose at which action is taken;
No action to further reduce doses is taken below the optimized level of protection.
CONCLUSION: There is no procedural difference

13. Types of Exposure Situations
Replacing ‘practice’ and ‘intervention’ with three exposure situations:
Planned exposure: everyday situations involving the planned operation of practices.
Emergency exposure: unexpected situations that occur during the operation of a practice requiring urgent action.
Existing exposure: situations that already exist when a decision on control has to be taken, including natural background radiation and residues from past practices.

14. Principles of Protection SOURCE RELATED
OPTIMIZATION
The level of protection should be the best under the prevailing circumstances, i.e., maximising the margin of good over harm.
Optimization of protection is always constrained by a level of dose (constraint) where action is almost always warranted, and involves keeping the magnitude of individual doses, the number of people exposed, and the likelihood of incurring exposures where these are not certain to be received as low as reasonably achievable, taking into account economic and societal factors.

15. The Evolution of ALARA 1955 To reduce exposures to the lowest
possible level
1959
To keep exposures
as low as
practicable
1966
readily achievable
economic and social considerations being taken into account
1973
reasonably achievable
1977
economic and social factors being taken into account
2006
economic and societal factors being taken into account

16. Optimization and Equity
Dose constraints were introduced in 1990 as a means to ensure that the optimization process did not create inequity
The view in RP06:
In planned situations, individual dose limits are adequate to ensure reasonable dose equity

17. Limits and Constraints
From all regulated sources
only in planned situations by
THE DOSE LIMITS
From a single source in all exposure situations by
THE DOSE CONSTRAINTS

18. The Use of Dose Constraints, 1
The basic level of protection for the most exposed individuals from a source within a type of exposure
Apply to all situations
Used prospectively at the start of the optimization process
Not a form of retrospective dose limitation
Established at national or local level, by regulator or by operator
- The value selected will depend on circumstances

19. The Use of Dose Constraints, 2
For planned situations: a basic level of protection, less than limits
In emergencies and in existing controllable exposure situations: a level of dose or risk where action to reduce that dose or risk is almost always warranted
An integral part of prospectively optimizing radiological protection at the source
If a relevant constraint was not complied with
- Further protection options must be considered in optimization
- Not necessarily a failure of protection

20. The Use of Dose Constraints, 3
Numerical criteria recommended in Publication 60 and thereafter can be regarded as constraints
The values fall into three bands: mSv, 1-20 mSv and mSv
Comparison with these three bands facilitates selection of appropriate constraints for situations not addressed explicitly by ICRP

21. Projected Doses of 0.01 - 1 mSv/year
Planned exposures, no direct benefit to them but a benefit to society
There should be general information and environmental surveillance or assessment
Doses represent a marginal increase above natural background
Exposure of members of the public from a planned operation

22. Projected Doses of 1 - 20 mSv/year
Individuals receive direct benefits from the exposure situation but not necessarily from the exposure or source
Individual surveillance or dose monitoring or assessment
Individual training or information
Occupational exposure in planned situations
Radon in workplaces and homes
Countermeasures in the event of an accident, e.g., sheltering and iodine prophylaxis.

23. Constraints for Radon 10 mSv per year
Basis: Setting a level of effective dose from radon where action would be warranted:
10 mSv per year
ICRP constraints: set where action is almost always warranted:
Home Bq m-3 (or 500 Bq m-3 ?)
Work Bq m-3 (or 1200 Bq m-3 ?)
National constraints: set by regulators using optimization of protection, can be below the ICRP constraints

24. Projected Doses of 20 - 100 mSv/year
Unusual, often extreme situations
Actions to reduce exposures would be disruptive or the source is out of control
Or, benefits from the exposure situation are commensurately high
Action to reduce exposures in an emergency
Exposure to abnormally high levels of natural background radiation

25. Application of Dose Constraints OCCUPATIONAL EXPOSURE
Individual doses in well-managed operations can be used to establish a dose constraint
Occupation should be specified in fairly broad terms
- x-ray diagnostic departments,
- operation of nuclear power plants, or
- the maintenance of nuclear installations
Usually dose constraints set at the national or local level
Sources should be specified to avoid confusion
Constraints should ensure that dose limits are not exceeded

26. Application of Dose Constraints OCCUPATIONAL EXPOSURE IN EMERGENCY SITUATIONS
Workers could incur higher doses than in planned situations, relaxation of controls could be permitted
No dose restrictions recommended for rescue operations to prevent serious injury or catastrophic conditions
Every effort should be made to keep doses < 1000 mSv to avoid serious tissue injuries (ideally < 100 mSv)
For other immediate and urgent rescue operations dose should be kept < 100mSv
Long-term recovery operations should be treated as part of planned occupational exposure

27. Setting Dose Constraints
For occupational exposure in planned situations: typically set by operators or, for small companies, by regulatory authorities
For public exposure in planned situations: typically set by regulatory authorities
For patients’ comforters and carers: typically set by the medical profession

28. Additional Radiation Dose and Risk 1 mSv – also public dose limit
UNACCEPTABLE RISK
1 mSv – also public dose limit
TOLERABLE RISK
DOSE CONSTRAINT
Optimization
Protection optimized
ACCEPTABLE RISK
(TRIVIAL RISK)

29. Additional Radiation Dose and Risk
1 – 20 mSv
UNACCEPTABLE RISK
20 mSv – also occupational dose limit
TOLERABLE RISK
DOSE CONSTRAINT
Optimization
Protection optimized
ACCEPTABLE RISK

30. Additional Radiation Dose and Risk
20 – 100 mSv
UNACCEPTABLE RISK
100 mSv
TOLERABLE RISK
DOSE CONSTRAINT
Optimization
Protection optimized
ACCEPTABLE RISK

31. ICRP 2006 Recommendations The System of Radiological Protection
Emphasizes a strong radiation safety culture through a cycle of continuous review and assessment to optimize radiation doses
Optimization involves evaluating and incorporating measures that tend to lower doses to workers, the public or patients
Optimization also entails consideration of avoidance of accidents and other potential exposures

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

33. Optimization of Protection
All aspects of optimization cannot be codified; optimization 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 optimization process.

34. Dose to the Public: Identify Exposed Person
The system of protection uses individual dose criteria
Doses to members of public cannot be measured directly
- Often not at all
Doses depend on age, location, eating habits, etc.
Thus, we must characterise an exposed individual
- Dose should be representative of the more highly exposed members of the population

35. Formerly: The Critical Group
The concept defined in 1977
Dose limits and constraints were applied to the mean dose in a ‘critical group’
Dose assessment methods have evolved, e.g., probabilistic techniques
‘Critical’ has the connotation of a crisis (never intended)
‘Group’ is confusing (the assessed dose is to an individual)

36. Now: The Representative Person
Characterises an individual who is representative of the more highly exposed individuals
This ‘representative person’ replaces ‘the average member of the critical group’
Assess prospective dose
- 3 age groups may be sufficient
- Deterministic or probabilistic approach
- Useful to involve stakeholders

37. The Collective Dose
Is an instrument for optimization, for comparing radiological technologies and protection procedures.
Is not intended as a tool for epidemiologic risk assessment. It is therefore inappropriate to use it in risk projections based on epidemiological studies.
The computation of cancer deaths based on collective doses involving trivial exposures to large populations is not reasonable and should be avoided. Such a use was never intended and is an incorrect use of the collective dose.

38. 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

39. Examples of Dose Weighting

40. The Optimization Process
Evaluation of exposure situations to identify the need for action
Optimization 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

41. Basic Structure of Dose MatrixL o c a l R e g i n G b S h r t m M d u I v x p s ( , É ) L o c a l R e g i o n a l
Group dose G l o b a l I n d i v i d u a l e x p o s u r e S h o r t M e d i u m L o n g c h a r a c t e r i s t i c s t e r m t e r m t e r m ( g e n d e r , a g e É )
TG OPIMISATION of PROTECTION

42. 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

43. 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.