Draft ICRP RecommendationsDraft ICRP Recommendations

Peter BurnsPeter BurnsARPANSAARPANSA

15th PBNC - October 2006

ICRP 2006 RecommendationsICRP 2006 Recommendations

ICRP Publication 60

Recommendations of the International Commission

on Radiological Protection, 1990.

Widely adopted internationally - Basis for the IAEA BSS

Draft Recommendations of the International

Commission on Radiological Protection - 02/276/06

- 5 June 2006.

ICRP 2006 RecommendationsICRP 2006 Recommendations

The ICRP has decided to issue 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.

ICRP 2006 RecommendationsICRP 2006 RecommendationsFoundation documents:

• Biological and Epidemiological Information on Health Risks

Attributable to Ionising Radiation (C1)

• Basis for Dosimetric Quantities Used in Radiological Protection (C2)

Building blocks:

• Low-Dose Extrapolation of Radiation-Related Cancer Risk (C1)

• Radiological Protection in Medicine (C3)

• Optimisation of Protection (C4)

• Assessing Dose to the Representative Individual (C4)

• The Scope of Radiological Protection Regulations:

Exclusion and Exemption (MC)

ICRP RP 06 - MICRP RP 06 - Major Featuresajor Features

• Maintaining the fundamental principles of

radiological protection, and clarifying how they

apply to sources and the individual;

• Updating the weighting factors and the radiation

detriment;

• Maintaining the dose limits;

• Extending the concept of constraints in the

source-related protection to all situations.

Why the need for change?

• The Commission emphasises that it is not a change but a clarification of the existing system, which has its origin over 50 years ago

• In London in 1950 ICRP recognised that the world of radiation protection had changing

Changes in radiation protection

• Development of nuclear reactors and nuclear weapons in the 1940s led to:

– Atmospheric weapons tests– Nuclear power– Artificial radioisotopes for medicine and industry

• These developments meant a greater potential for wide scale exposures of populations

Changes in radiation protection

By 1950 there was clear evidence that

• cumulative doses from chronic exposure had caused leukaemia in radiologists

• hereditary effects had been demonstrated in animals

Changes in radiation protection

• Long term cumulative exposures were significant for carcinogenic and hereditary effects

• The probability of developing these effects was proportional to cumulative doses

• Previously limits had been designed to prevent superficial effects by keeping exposures below a rate of 1 R per week

ICRP - London 1950ICRP lowered exposure rate from 1R w-1 to 0.3R w-1

"While the values proposed for the maximum permissible exposures are such as to involve a risk that is small compared to the other hazards of life, nevertheless in view of the unsatisfactory nature of much of the evidence on which judgements are based, coupled with knowledge that certain radiation effects are irreversible and cumulative, it is strongly recommended that every effort be made to reduce exposures to all types of ionizing radiations to the lowest possible level."

Evolution of recommendations1950 “as low as possible”

1958 “as low as practicable”

1966 “……readily achievable, economic and social considerations….”

1973 “……reasonably achievable……”

1976 “……economic and social factors…”

ICRP 60 - 1990• In 1960 the Commission introduced the concept

of Optimisation to sit with Justification and Limitation as the main principles for radiation protection

• Dose Constraints were introduced as benchmarks in the Optimisation Process

• There has been much confusion about what Dose Constraints are and how to apply them and the new recommendations are attempting to address this

DRAFT ICRP RecommendationsDRAFT ICRP RecommendationsThe General System of Radiological Protection

• The probabilistic nature of stochastic effects means a clear distinction between 'safe' and 'dangerous‘ is impossible.

• Fundamental principles are:Justification, Limitation and Optimisation.

• Dose Constraints in the Optimisation Process are the primary tool in managing radiation safety.

Additional Radiation Dose and RiskAdditional Radiation Dose and Risk

UNACCEPTABLE RISKUNACCEPTABLE RISK

TOLERABLE RISKTOLERABLE RISK

OptimisationOptimisation

Protection optimizedProtection optimized

ACCEPTABLE RISKACCEPTABLE RISK

TRIVIAL RISKTRIVIAL RISK

DOSE CONSTRAINT

DOSE LIMITDOSE LIMIT

DRAFT ICRP RecommendationsDRAFT ICRP RecommendationsThe General System of Radiological Protection

• Strong radiation safety culture through a cycle of continuous review and assessment to optimise doses for practices using a single source.

• Optimisation involves evaluating and incorporating measures that tend to lower doses to the public and workers.

• It also entails consideration of avoidance of accidents and other potential exposures.

DRAFT ICRP RecommendationsDRAFT ICRP Recommendations

• Dose constraints are used as an integral part of the process of prospectively optimising radiological protection at the source.

• If an assessment shows a relevant constraints was not complied with,further consideration of protection options in an optimisation procedure is required,this should not necessarily be regarded as a failure of protection.

DRAFT ICRP RecommendationsDRAFT ICRP Recommendations• It is the process of prospectively optimising

radiological protection that is important

• Constraints should be set according to well managed practices and should be monitored and modified if necessary– Reference or Action Levels - Level of Ambition

• It is not about compliance with a number

Application of Dose ConstraintsApplication of Dose Constraints The optimisation of protection is a forward looking iterative

process aimed at preventing exposures before they occur.

• Operators and the appropriate national authorities have

responsibilities for applying the optimisation principle.

• Optimisation of protection 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.

Application of Dose ConstraintsApplication of Dose Constraints

• 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.

DRAFT ICRP RecommendationsDRAFT ICRP RecommendationsThree exposure situations are identified:

• Planned Situations are everyday situations involving the planned operation of practices.

• Emergency Situations are unexpected situations that occur during the operation of a practice requiring urgent action.

• Existing Situations are exposure situations that already exist when a decision on control has to be taken, including natural background radiation and residues from past practices.

DRAFT ICRP RecommendationsDRAFT ICRP Recommendations

• For planned situations:constraints represent a basic level of protection

• In emergency or existing controllable exposure situations:constraints represent a level of dose or risk where action to reduce that dose or risk is almost always warranted.

Band of Projected Effective DoseBand of Projected Effective Dose0.01 - 1 mSv - Acute or Annual0.01 - 1 mSv - Acute or Annual

Characteristics of the Situation

Radiological Protection Requirements

Examples

Individuals are exposed to a source that gives them no direct benefit but benefits general society.

Exposures are usually controlled by action taken directly on the source for which radiological protection requirements can be planned in advance.

General information on the level of exposure should be made available.

Periodic checks should be made on the exposure pathways to check on the level of exposure.

Constraints set for public exposure in planned situations.

Band of Projected Effective DoseBand of Projected Effective Dose1 to 20 mSv - Acute or Annual1 to 20 mSv - Acute or Annual

Characteristics of the Situation

Radiological Protection Requirements

Examples

Individuals will usually receive direct benefit from the exposure situation but not necessarily from the exposure itself. Exposures may be controlled at source or, alternatively, by action in the exposure pathways.

Where possible, general information should be made available to enable individuals to reduce their doses.

For planned situations, individual monitoring or assessment and training should take place.

Constraints set for occupational exposure in planned situations.

Dose constraint for radon in dwellings.

Band of Projected Effective DoseBand of Projected Effective Dose20 to 100 mSv - Acute or Annual20 to 100 mSv - Acute or Annual

Characteristics of the Situation

Radiological Protection Requirements

Examples

Individuals exposed by sources that are either out of control or where actions to reduce doses would be disproportionately disruptive.

Exposures are usually controlled by action on the exposure pathways. Individuals may or may not receive benefit from the exposure situations.

Consideration should be given to reducing doses.

Increasing efforts should be made to reduce doses as the doses approach 100 mSv. Individuals should receive information on the radiation risk and on the actions to reduce doses.

Assessment of individual doses should be undertaken.

Constraint for evacuation in a radiological emergency.

ICRP Radiation Protection 06

• Minor changes to:– Radiation weighting factors– Tissue weighting factors– Risk coefficients

• Caution on the use of: – Effective Dose– Collective dose

Main Conclusions on BiologyMain Conclusions on BiologyDose-response for stochastic effects: A simple proportionate

relationship between dose and risk at low doses.

DDREF: 2.

Genomic instability, bystander effects, adaptive response: Still insufficient knowledge for protection purposes.

Genetic susceptibility: Known disorders too rare to distort risk estimates; impact of weak genetic determinants cannot be judged.

In-utero cancer risk: Life time risk similar to that of young children (a few times higher than that of the whole population).

Main Conclusions on BiologyMain Conclusions on Biology

Nominal probability coefficients for cancer: Based on incidence and not mortality.

Nominal probability coefficients for heritable diseases: Based on UNSCEAR 2001

- up to 2nd generation

Tissue reactions in adults: Revised judgements but no major changes.

Risks of non-cancer diseases (A-bomb LSS): Great uncertainty on dose response below 1 Sv; no judgement on low dose risk possible.

Radiation Weighting Factors, Radiation Weighting Factors, wwRR

Type and energy range

Publication 60 2006

Photons, all energies 1 1

Electrons and muons, all energies

1 1

Protons 5 2

Alpha particles, fission fragments, heavy nuclei

20 20

Neutrons Stepwise function

Continuous function

Tissue Weighting FactorsTissue Weighting Factors• Determine lifetime cancer incidence risk for radiation

associated cancers.• Apply DDREF.• Transfer risk estimates across populations (ERR:EAR weights).• Apply weighted risk estimates to and average across seven

Western and Asian populations to provide nominal risk coefficients.

• Adjust for lethality, quality of life and for years of life lost to obtain the radiation detriment for each type of cancer.

• Normalize to unity and obtain the relative radiation detriments.• Group into four categories broadly reflecting the relative

detriments, i.e. the tissue weighting factors.

Tissue Weighting Factors, Tissue Weighting Factors, wwTT

Tissue wT ∑ wT

Bone-marrow, breast, colon, lung, stomach, remainder tissues1

0.12 0.72

Gonads 0.08 0.08

Bladder, oesophagus, liver, thyroid 0.04 0.16

Bone surface, brain, salivary glands, skin 0.01 0.04

1 Nominal wT divided equally between 14 tissues.

Nominal Nominal RiskRisk Coefficients for Coefficients for Stochastic EffectsStochastic Effects ((% Sv% Sv-1-1))

Exposed population

Cancer Heritable effects

Total

1990 2006 1990 2006 1990 2006

Whole

population

6.0 5.5 1.3 0.2 7.3 6

Adult 4.8 4.1 0.8 0.1 5.6 4

Use of Effective Dose (E)Use of Effective Dose (E)

• E is calculated by using reference values for a reference person or group. Weighting factors are averaged over age and gender.

• E should be used only for compliance of constraints and dose limits to control stochastic effects.

• E should mainly be used for planning in prospective situations.

• E should not be used for more detailed retrospective dose and risk assessments on exposure of individuals.

• E should not be used for epidemiological studies.

Use of Collective DoseUse of Collective Dose• Is an instrument for optimisation, 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.

UNSCEAR 2006 Report

United Nations Scientific Committee on the Effects of Atomic Radiation

• 2006 Report to be submitted to the General Assembly on 25 October

UNSCEAR 2006• 5 Annexes on biological effects of radiation

– Sources-to-effects assessment for radon in homes and workplaces

– Epidemiological studies of radiation and cancer

– Epidemiological evaluation of cardiovascular disease and other non-cancer diseases following radiation exposure

– Effects of ionizing radiation on the immune system

– Non-targeted and delayed effects of exposure to ionizing radiation