ICRP: What It Does and Why Dr Jack Valentin

Transcription

1 ICRP: What It Does and Why Dr Jack Valentin Scientific Secretary, ICRP International Commission on Radiological Protection ICRP: Who, why, what? The 2007 Recommendations Justification (political) optimisation limits & constraints Focus on the exposure situation; include non-human species Related guidance Recent reports; work in the pipeline Topical advice Recent reports; work in the pipeline

2 About ICRP

3 ICRP, an Independent Registered Charity Established to advance for the public benefit the science of Radiological Protection, in particular by providing recommendations and guidance on all aspects of protection against ionising radiation.

4 Structure of ICRP, Main Commission Chair: Dr L-E Holm, SE 12 other members Scientific Secretariat Dr J Valentin, SE C1- Radiation Effects Dr R J Preston, US C2- Doses from Radiation Exposure Dr H Menzel, CH C3- Protection in Medicine Dr C Cousins, UK Task Groups C4- Application of ICRP Recommend:s Dr A Sugier, FR Working Parties C5-Prot. of the Environment Prof J Pentreath, UK

5 Structure of ICRP,

6 Structure of ICRP,

7 ICRP In The Cosmic Scheme Basic Scientific Studies Scientific Evaluations (UNSCEAR, BEIR etc.) ICRP Recommendations Regional (PAHO, EC, NEA) & Topical (ILO, WHO, FAO) Stand s International Safety Standards: BSS (IAEA) Industry Stand s (ISO, IEC) National Regulations Demonstration of Compliance

8 The 2007 Recommendations of ICRP

9 Why Are We Updating New biological & physical information Validity of the LNT model? (Linear, No Threshold) Increasing use of radiation in medicine Increase professional awareness? Post-Chernobyl lessons; inclusion of natural exposures Coherent, consistent implementation of ICRP Publication 60? Protection of the environment Scientific proof of adequate protection?

10 ICRP 1990 Rec s: Logical But Complex

11 Aims of the Revision Take account of new science Feed back experience of current radiation safety standards Improve & streamline the presentation Use an open, transparent process (9 years gestation!) Maintain as much stability as is consistent with the new information

12 To Get the Recommendations Buy printed or electronic copies IRPA Associated Societies are eligible for a discount Developing countries: free download at HINARI Junior staff: summary in JRP For all of this, see Or translate them

13 In Brief, the Recommendations Retain the fundamental principles of protection Clarify how they apply to sources and the individual Change the focus from process (practice/intervention) to exposure situation (planned/emergency/ existing) Extend the concept of source-related constraints to all situations Update weighting factors and detriment Maintain the current dose limits And for more details, welcome to Background Plenary II, tomorrow afternoon!

14 In Support of The 2007 Recommendations

15 Publication 99: Low-Dose Cancer Risk Focus on doses below dose limits Validity of the LNT model? (Linear, No Threshold) LNT: Scientifically plausible but not unambiguous (cf. Central Limit Theorem, i.e., valid at the population level) Fractionation / protraction of dose lower risk For low dose, divide solid cancer risk by DDREF (Dose, Dose rate REduction Factor) = 2 Uncertain possibility of a threshold uncertainty in DDREF Anyway, evidence not in favour of a universal threshold

16 Publication 101: (a) Representative Person Replaces average member of the critical group Representative of the 5% more highly exposed not the most extreme Check: Reasonable? Sustainable? Homogeneous? Dose assessment: deterministic or probabilistic Prospective (hypothetical person) or retrospective (can be real person) Simplified age averaging Intake coefficients: 6 age groups Modelling Repr. Person 3 groups (age 0-5, 6-15, 16-70) Remember: age-specific biokinetics, but age-averaged cancer risk Involve stakeholders to identify characteristics Improves quality, understanding, and acceptability

17 Publ. 101: (b) Optimisation of Protection Source-related process to keep doses / number exposed / probability of accidents as low as reasonably achievable With individual doses below appropriate constraints Taking account of economic & social factors An ongoing, cyclical process A frame of mind have I done all that I reasonably can? Applies to all exposure situations: Planned-Emergency- Existing Extends and updates, but does not cancel, old advice Involve stakeholders But do not surrender responsibility for final decision!

18 Publ. 101: (b) Optimisation, cont d Decision-aiding techniques are, just, useful tools Optimisation is sound judgement, not mathematics Collective dose: a useful, but not sufficient, input use matrix! E.g., local-regional-global; short-medium-long term; low-medium-high doses A key parameter (at least in worker protection), but we usually also need: average dose, number exposed, range, etc Perhaps give more weight to a few large doses than to many small doses doses now than to doses in the far future

19 Publ. 104: Scope of Radiological Protection Exclusion: Uncontrollable exposures E.g., natural radionuclides in the body; cosmic radiation at ground level Exemption from specified requirements: If unwarranted In planned situations Activities conducted justified Individual risk acceptably small Protection optimised No appreciable probability of failure to meet these conditions <10 usv/y often exempted but NOT the sole criterion; exempt on basis of optimisation, not triviality of dose Clearance: a sub-case of exemption When material/site changes so that a regulatory requirement is no longer warranted

20 Publ. 104: Scope of Radiol.Protection, cont d

21 Publ. 104: Scope of Radiol.Protection, cont d Generically derived exemption / clearance levels Exemption levels: basically, a national regulatory decision International intergovernmental organisations: useful standardisation Activity Activity concentration in low amounts Activity concentration in any amount (in a given situation / for unrestricted release) Emergency situations: exclusion / exemption irrelevant Existing situations: is an intervention justified? Is protection optimised? There is no single look-up number! Regulatory control should achieve net benefit Requirements should be applied such that protection is optimised

22 Publ. 105: Radiation Protection in Medicine Focus on justification and optimisation Justification for a defined purpose; for an individual patient Limits and constraints could do more harm than good Medical condition often more critical than the radiation exposure Diagnostic and interventional radiology Equipment should facilitate dose management Diagnostic Reference Levels (national/regional/local) for peer achievement Radiation therapy Accident avoidance Reduction of side effects (including 2nd cancers) Comforters / carers, and volunteers in research Dose constraints appropriate

23 Publ. 107: Nuclear Decay Data (in press) An electronic database: half-lives, decay chains, yields, etc Supersedes Publication radionuclides of 97 elements, of which 329 with halflives <10 min. Publ. 38 had 820 radionuclides, of which 56 with half-lives < 10 min Data are provided on a CD-ROM in the report Data presented in a format suitable for dosimetrists Continuous energy distributions of beta and fission neutrons are given Tabulation of emitted radiations not restricted by page size!

24 Publ. 108, with ICRU: Reference Phantoms (in press) Voxel-based, sex-specific Adjusted to agree with Reference Man and Woman Phantom data provided on a CD-ROM in the report To permit your own calculations Will be the basis of dose [conversion] coefficients for internal [and external] exposure Some examples given in the report Fetus and child phantoms are in the pipeline

25 And in Due Course. Dose coefficients for intakes of radionuclides For occupational and public exposures Including fetus and breast-feeding infants Replacing Publ. 30 / 56 / 72 / etc. Dose conversion coefficients for external exposures Together with ICRU Replacing ICRP Publ. 74 = ICRU Report 57

26 Topical reports

27 Recent & Current Reports Publication 100 the Human Alimentary Tract (HAT) Supporting Guidance 5 Criteria behind ICRP levels Publ 102 Multi-Detector CT Publ 106 Radiopharmaceuticals, P 53 Add. 3 (in press) Publ XX Reference Animals and Plants Publ XX Radiological protection in cardiology Publ XX 2nd cancers and new radiotherapy techniques Publ XX Avoiding accidents with new radiotherapy

28 and ICRP Work Continues Thank You!