1. 4/2003 Rev 2 IV.1.3 – slide 1 of 46 Part IVPrinciples of Radiation Protection and the International Framework Module 1Conceptual Framework Session 3Justification, Optimization and Dose Limits Session IV.1.3 IAEA Post Graduate Educational Course Radiation Protection and Safe Use of Radiation Sources

2. 4/2003 Rev 2 IV.1.3 – slide 2 of 46  We will discuss the Justification of a Practice  We will also discuss the optimization of protection  Finally we will summarize the individual dose limits Overview

3. 4/2003 Rev 2 IV.1.3 – slide 3 of 46 Justification of a Practice (115) Decisions concerning the adoption and continuation of any human activity involve a choice between possible options carried out in two stages:  examination of each option separately to identify those options which can be expected to do more good than harm - this provides a “short list” from which the preferred option can then be selected  the final selection will often involve the replacement of one existing practice by another

4. 4/2003 Rev 2 IV.1.3 – slide 4 of 46 Justification of a Practice When practices involving exposure, or potential exposure, are being considered, the radiation detriment should be explicitly included in the process of choice The detriment includes all detriments and the costs of the practice - the radiation detriment may be a small part of the total The justification of a practice thus goes far beyond the scope of radiological protection

5. 4/2003 Rev 2 IV.1.3 – slide 5 of 46 Justification of a Practice Justification is limited to the first of the two stages (it requires only that the net benefit be positive) To search for the best of all the available options is usually a task beyond the responsibility of radiological protection agencies (116) The process of justification is required, not only when a new practice is being introduced, but also when existing practices are being reviewed in the light of new information about their efficacy or consequences  Benefits i  Detriments i > 1

6. 4/2003 Rev 2 IV.1.3 – slide 6 of 46 Justification of a Practice This option should be treated in the same way as the justification of a new practice, but the disadvantages of withdrawing a well-established practice may be more obvious than the advantages of introducing a comparable new one and withdrawal of the practice may not result in the withdrawal of all the associated sources of exposure Preventing the further extension of an existing practice that is no longer justified may sometimes be a reasonable compromise

7. 4/2003 Rev 2 IV.1.3 – slide 7 of 46 Justification of a Practice (2.20) No practice or source within a practice should be authorized unless the practice produces sufficient benefit to the exposed individuals or to society to offset the radiation harm that it might cause; that is: unless the practice is justified, taking into account:  social  economic  other relevant factors

8. 4/2003 Rev 2 IV.1.3 – slide 8 of 46 Justification of a Practice (2.22) Except for justified practices involving medical exposures, the following practices are not justified when they result in an increase, by deliberate addition of radioactive substances or by activation, in the activity of the associated commodities or products:  practices involving food, beverages, cosmetics or any other commodity or product intended for ingestion, inhalation or percutaneous intake by, or application to, a human being  practices involving the frivolous use of radiation or radioactive substances in commodities or products such as toys and personal jewelry or adornments

9. 4/2003 Rev 2 IV.1.3 – slide 9 of 46 Optimisation of Protection (117) Once a practice has been justified and adopted, it is necessary to consider how best to use resources in reducing the radiation risks The broad aim should be to ensure that the magnitude of the individual doses, the number of people exposed, and the likelihood of incurring exposures where these are not certain to be received, are all kept ALARA, economic and social factors being taken into account ALARA? Individual Dose Number Exposed Probability of Harm Resources

10. 4/2003 Rev 2 IV.1.3 – slide 10 of 46 Optimisation of Protection If reducing the detriment can be achieved only with a deployment of resources that is seriously out of line with the consequent reduction, it is not in society*s interest to take that step, provided that individuals have been adequately protected The protection can then be said to be optimised and the exposures to be ALARA, economic and social factors having been taken into account

11. 4/2003 Rev 2 IV.1.3 – slide 11 of 46 Optimisation of Protection (118) The methods range from simple common sense to complex techniques of cost-benefit analysis or multi- attribute analysis All these techniques are aids to deciding when sufficient effort has been applied to the reduction of the detriment associated with a practice or with an identifiable component of a practice

12. 4/2003 Rev 2 IV.1.3 – slide 12 of 46 Optimisation of Protection Except when dealing with potential exposures, it is appropriate to use the effective dose as a surrogate for detriment to an individual, because the weighting factors used in calculating the effective dose take account of the whole detriment to the health of individuals and their descendants, not only the fatal detriment The collective effective dose is an adequate representation of the collective detriment

13. 4/2003 Rev 2 IV.1.3 – slide 13 of 46 Optimisation of Protection (119) The judgements involved in optimising protection are not purely quantitative— they involve preferences between detriments of different kinds and between the deployment of resources and health effects (120) The process of optimising protection is essentially source-related and should first be applied at the design stage of any project It is here that dose reductions are most likely to be achievable in cost-effective ways

14. 4/2003 Rev 2 IV.1.3 – slide 14 of 46 Optimisation of Protection At the design stage, the process of optimisation of protection will have some generic aspects Further optimisation of protection should be carried out at the operational level Operational optimisation is usually informal, involving common-sense changes in procedures, but is often very effective (121) Most of the methods used in the optimisation of protection tend to emphasise the benefits and detriments to society and the whole exposed population

15. 4/2003 Rev 2 IV.1.3 – slide 15 of 46 Optimisation of Protection The benefits and detriments are unlikely to be distributed through society in the same way Optimisation of protection may thus introduce a substantial inequity between one individual and another This inequity can be limited by incorporating source- related restrictions on individual dose into the process of optimisation These source related restrictions are termed dose constraints, previously called upper bounds

16. 4/2003 Rev 2 IV.1.3 – slide 16 of 46 Optimisation of Protection A BC Dose Dose to “A” and “B” decreased (A more than B) but the dose to “C” increased Net benefit to society Individual Effects: Benefit to A and B Detriment to C Optimisation introduced an Inequity

17. 4/2003 Rev 2 IV.1.3 – slide 17 of 46 (2.24) In relation to exposures from any particular source within a practice, except for therapeutic medical exposures, protection and safety shall be optimized in order that the magnitude of individual doses, the number of people exposed and the likelihood of incurring exposures all be kept as low as reasonably achievable (ALARA), economic and social factors being taken into account, within the restriction that the doses to individuals delivered by the source be subject to dose constraints. Optimization of Protection

18. 4/2003 Rev 2 IV.1.3 – slide 18 of 46 Optimization of Protection (2.25) The process of optimization of protection and safety may range from qualitative to quantitative analyses, but shall take all relevant factors into account so as to contribute to achieving these objectives:  to determine optimized protection and safety measures, with account taken of the available protection and safety options as well as the nature, magnitude and likelihood of exposures  to establish criteria, based on the optimization, for the restriction of exposures and their probabilities by means of measures for preventing accidents and mitigating their consequences

19. 4/2003 Rev 2 IV.1.3 – slide 19 of 46 Optimization of Protection (2.26) Except for medical exposure, the optimization of the protection and safety measures associated with any particular source within a practice shall be subject to dose constraints which:  do not exceed values established by the Regulatory Authority or which can exceed the dose limits  ensure, for any source that can release radioactivity to the environment, that the cumulative effects of each annual release be restricted so that the effective dose in any year to any member of the public, including future generations, is unlikely to exceed any relevant dose limit, taking into account all other relevant sources and practices under control

20. 4/2003 Rev 2 IV.1.3 – slide 20 of 46 Examples of Optimization of Protection for Medical Exposures (11.11) equipment used in medical exposure shall be so designed that:  failure of a single component is promptly detectable so that unplanned medical exposure of patients is minimized  the incidence of human error in unplanned medical exposure is minimized

21. 4/2003 Rev 2 IV.1.3 – slide 21 of 46 Examples of Optimization of Protection for Medical Exposures (11.11) equipment used in medical exposure shall be so designed that:  failure of a single component is promptly detectable so that unplanned medical exposure of patients is minimized  the incidence of human error in unplanned medical exposure is minimized

22. 4/2003 Rev 2 IV.1.3 – slide 22 of 46 Individual Dose Limits (122) If the procedures of justification of practices and of optimisation of protection have been conducted effectively, there will be few cases where limits on individual dose will have to be applied However, such limits provide a clearly defined boundary for these more subjective procedures and prevent excessive individual detriment, which might result from a combination of practices Dose limits should be applied only in the control of practices

23. 4/2003 Rev 2 IV.1.3 – slide 23 of 46 (123) Any continued exposure just above the dose limits would result in additional risks from the defined practices that could reasonably be described as “unacceptable” in normal circumstances The definition and choice of dose limits involve social judgements which are difficult because the dose limit has to be set at a defined value and there is no discontinuity in the scale of acceptability For ionising radiation with no threshold for some of the consequences, the choice of limits cannot be based on health considerations alone Individual Dose Limits

24. 4/2003 Rev 2 IV.1.3 – slide 24 of 46 (124) Several misconceptions have arisen about the definition and function of dose limits  The dose limit is widely, but erroneously, regarded as a line of demarcation between “safe” and “dangerous”  It is also widely, and erroneously, seen as the most simple and effective way of keeping exposures low and forcing improvements  It is commonly seen as the sole measure of the stringency of a system of protection Individual Dose Limits

25. 4/2003 Rev 2 IV.1.3 – slide 25 of 46 These misconceptions are strengthened by the incorporation of dose limits into regulatory instruments Exceeding a dose limit becomes an infraction of the rules and sometimes a statutory offence Managements, regulatory agencies, and governments all improperly set out to apply dose limits whenever possible, even when the sources are partly, or even totally, beyond their control, and when the optimisation of protection is the more appropriate course of action Individual Dose Limits

26. 4/2003 Rev 2 IV.1.3 – slide 26 of 46 (125) Dose limits are commonly used in two very different ways:  the dose limit is regarded as a limiting restriction on the design and operation of an installation  the dose limit is used in its original function of applying controls on each individual*s accumulation of dose It will never be appropriate to apply dose limits to all types of exposure in all circumstances Individual Dose Limits

27. 4/2003 Rev 2 IV.1.3 – slide 27 of 46 In circumstances for which they were not intended, e.g. emergencies or during special operations of considerable importance, they can often be replaced by specially developed prescriptive limits or by specified levels of dose that call for the initiation of a defined course of action Such levels, often called action, investigation or reference levels, provide a useful way of structuring the procedures of radiological protection (126) The dose limits are discussed on the following slides Individual Dose Limits

28. 4/2003 Rev 2 IV.1.3 – slide 28 of 46 Individual Dose Limits (11-1) The dose limits apply to exposures attributable to practices, with the exceptions of medical exposures and of exposures from natural sources that cannot reasonably be regarded as being under the responsibility of any principal party of the Standards (11-3) The dose limits are not relevant for the control of potential exposures (11-4) The dose limits are not relevant for decisions on whether and how to undertake an intervention

29. 4/2003 Rev 2 IV.1.3 – slide 29 of 46 External Radiation Dose Gamma, beta or neutron radiation emitted by radioactive material outside the body exposing the skin, lens of the eye, extremities & the whole body (i.e. internal organs)

30. 4/2003 Rev 2 IV.1.3 – slide 30 of 46 Internal Radiation Dose Alpha, beta or gamma radiation emitted by radioactive material inside the body exposing internal organs such as: thyroid bone GI System lung

31. 4/2003 Rev 2 IV.1.3 – slide 31 of 46 Individual Dose Limits (11-5) Occupational Limit (adults):  effective dose of 20 mSv per year averaged over five (5) consecutive years  an effective dose of 50 mSv in any single (1) year  an equivalent dose to the lens of the eye of 150 mSv in a (1) year  an equivalent dose to the extremities (hands and feet) or the skin (averaged over 1 cm 2 ) of 500 mSv in a (1) year

32. 4/2003 Rev 2 IV.1.3 – slide 32 of 46 Adult Occupational Dose Limits Whole Body (everything except extremities) 50 mSv maximum per year 20 mSv averaged over 5 years Extremities 500 mSv per year Skin of the Whole Body 500 mSv per year Lens 150 mSv

33. 4/2003 Rev 2 IV.1.3 – slide 33 of 46 The dose to the lens of the eye is measured at a depth of 0.3 cm The shallow (skin) dose is measured at a depth of 0.007 cm The whole body dose is measured at a depth of 1 cm Depths at which External Radiation Dose is Measured

34. 4/2003 Rev 2 IV.1.3 – slide 34 of 46 Individual Dose Limits December 31, 2007 January 1, 2003 1 December 31, 2012 January 1, 2008 2 December 31, 2017 January 1, 2013 3 December 31, 2022 January 1, 2018 4 January 1, 2003 December 31, 2007 1 January 1, 2004 December 31, 2008 2 December 31, 2009 January 1, 2005 3 December 31, 2010 January 1, 2006 4

35. 4/2003 Rev 2 IV.1.3 – slide 35 of 46 Individual Dose Limits December 31, 2007 January 1, 2003 1 December 31, 2012 January 1, 2008 2 January 1, 2003 December 31, 2007 1 January 1, 2004 December 31, 2008 2 5 mSv 10 mSv 15 mSv 20 mSv 50 mSv 5 mSv 10 mSv 15 mSv 20 mSv 50 mSv 5 mSv 10 mSv 15 mSv 20 mSv 50 mSv 20 mSv 15 mSv 10 mSv 20 mSv Avg 29 mSv Avg

36. 4/2003 Rev 2 IV.1.3 – slide 36 of 46 Individual Dose Limits (11-6) Occupational Limit (apprentices and students 16 to 18 years of age):  effective dose of 6 mSv in a year  equivalent dose to the lens of the eye of 50 mSv in a year  equivalent dose to the extremities or the skin (averaged over 1 cm 2 ) of 150 mSv in a year

37. 4/2003 Rev 2 IV.1.3 – slide 37 of 46 16–18 Year Old Occupational Dose Limits Whole Body (everything except extremities) 6 mSv maximum per year Extremities 150 mSv per year Skin of the Whole Body 150 mSv per year Lens 50 mSv

38. 4/2003 Rev 2 IV.1.3 – slide 38 of 46 Individual Dose Limits (11-7) In special circumstances, a temporary change in the dose limits may be approved:  the dose averaging period may be up to 10 consecutive years, and the effective dose for any worker shall not exceed 20 mSv per year averaged over this period and shall not exceed 50 mSv in any single year, and the circumstances shall be reviewed when the dose reaches 100 mSv; or  the temporary change in the dose limitation shall be as specified by the Regulatory Authority but shall not exceed 50 mSv in any year and the period of the temporary change shall not exceed 5 years

39. 4/2003 Rev 2 IV.1.3 – slide 39 of 46 Individual Dose Limits (11-8) The estimated average doses to the relevant critical groups of members of the public attributable to practices shall not exceed the following limits:  an effective dose of 1 mSv in a year;  in special circumstances, an effective dose of up to 5 mSv in a single year provided that the average dose over five consecutive years does not exceed 1 mSv per year;  an equivalent dose to the lens of the eye of 15 mSv in a year; and  an equivalent dose to the skin of 50 mSv in a year.

40. 4/2003 Rev 2 IV.1.3 – slide 40 of 46 Public Dose Limits Whole Body (everything except extremities) 1 mSv per year **Special circumstances** 5 mSv maximum per year 1 mSv averaged over 5 years Extremities 50 mSv per year Skin of the Whole Body 50 mSv per year Lens 15 mSv

41. 4/2003 Rev 2 IV.1.3 – slide 41 of 46 Individual Dose Limits (11-9) The dose limits do not apply to comforters of patients, i.e., individuals knowingly exposed while voluntarily helping in the care, support and comfort of patients undergoing medical diagnosis or treatment, or to visitors of such patients  The dose shall be constrained so that it is unlikely to exceed 5 mSv during the period of a patient’s diagnostic examination or treatment  The dose to children visiting patients who have ingested radioactive materials should be similarly constrained to less than 1 mSv

42. 4/2003 Rev 2 IV.1.3 – slide 42 of 46 Patient Comforter and Visiting Children Dose Limits Children Dose Limits Whole Body (everything except extremities) Patient Comforters 5 mSv per examination or treatment Children Visiting Patients 1 mSv per patient hospital stay

43. 4/2003 Rev 2 IV.1.3 – slide 43 of 46 Dose Limit Summary Whole Body (max) Whole Body (average) Lens of Eyes SkinExtremity Adult5050 20 over 5 yrs 20 over 10 yrs 150500500 Minor6None50150150 Public15None 1 over 5 yrs 1550None Comforter5NoneNoneNoneNone Child Visitor 1NoneNoneNoneNone NOTE: All numerical dose limits have units of mSv in one year except for the limits for comforters and visiting children. The limit for these last two groups is per patient diagnostic procedure or treatment

44. 4/2003 Rev 2 IV.1.3 – slide 44 of 46 (11-10) The dose limits apply to the sum of:  the doses from external exposure in the specified period  the committed doses from intakes in the same period The period for calculating the committed dose shall be:  50 years for intakes by adults  to age 70 years for intakes by children Individual Dose Limits

45. 4/2003 Rev 2 IV.1.3 – slide 45 of 46 (11-1 1) For compliance with dose limits, the sum of:  the personal dose equivalent from external exposure to penetrating radiation in the specified period  the committed equivalent dose or committed effective dose, as appropriate, from intakes of radioactive substances in the same period Individual Dose Limits

46. 4/2003 Rev 2 IV.1.3 – slide 46 of 46 Where to Get More Information  International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources, Safety Series No. 115, IAEA, Vienna (1996)