Intervention for Chronic and Emergency Exposure Situations General Principles and Types of Events Prolonged (Chronic) Radiation Exposure Lecture IAEA Post Graduate Educational Course in Radiation Protection and Safety of Radiation Sources

Module X.1 - General Principles and Types of Events2 Introduction l Prolonged (chronic) exposures are adventitiously and persistently incurred by the public over long periods l This lesson provides guidance on the application of the ICRP’s system of radiological protection to situations of prolonged (chronic) exposure

Module X.1 - General Principles and Types of Events3 Content l Prolonged exposure l Basic framework l The ICRP System for radiological protection l Specific reference levels l Generic reference levels l Specific prolonged exposure situations l Summary

Module X.1 - General Principles and Types of Events4 Prolonged Exposure l Delivered by the “natural” sources n Cosmic radiation n Terrestrial n Indoor radon n NORM from extractive industries l Delivered by the “artificial” sources n Current practices n Past activities and events n Accidents n Commodities

Module X.1 - General Principles and Types of Events5 Basic Framework Radiation quantities l The relevant dosimetric quantity: n annual effective dose [mSv] l The subsidiary quantities: n existing annual dose n additional annual dose n averted annual dose n avertable annual dose n projected dose n residual dose

Module X.1 - General Principles and Types of Events6 Basic Framework Radiation Induced Health Effects l The annual dose for common prolonged exposure situations: well below the threshold for deterministic effects l The stochastic effects are the only radiation-induced health effects of concern

Module X.1 - General Principles and Types of Events7 Basic Framework System of Radiological Protections l Scope: the ICRP system of radiological protection applies to controllable exposures l Aim: to provide an appropriate standard of protection for humans l Categorisation: practices and interventions

Module X.1 - General Principles and Types of Events8 Practices l A practice may add annual doses to the existing annual dose n Transitory exposures (direct irradiation and short-lived radionuclides) n Prolonged exposures (long-lived radionuclides) l The ICRP system of radiological protection for practices is concerned with the additional annual dose attributable to practice

Module X.1 - General Principles and Types of Events9 Additional Annual Dose

Module X.1 - General Principles and Types of Events10 Application of the ICRP System Practices l Justification of the practice n Justifying practices involving prolonged exposure l Optimisation of radiological protection n Optimising protection of sources delivering prolonged exposure l Limitations of individual doses n Limiting individual doses attributable to prolonged exposure (dose constraints and dose limits)

Module X.1 - General Principles and Types of Events11 Recommended Levels Individual Dose Restrictions

Module X.1 - General Principles and Types of Events12 Interventions in prolonged exposure situations l Interventions are intended to reduce the existing annual dose (averting annual dose components) by n Removing existing dose n Modifying pathways n Reducing the number of exposed people

Module X.1 - General Principles and Types of Events13 Averted Annual Dose

Module X.1 - General Principles and Types of Events14 Application of ICRP System Interventions - Prolonged Exposure l Justification of intervention l Optimisation of protective (remedial) actions

Module X.1 - General Principles and Types of Events15 Justification l Two extremes n The existing annual dose is low enough to make intervention unexpected (not likely to be justifiable) n The existing annual dose is so high as to justify intervention under almost any circumstances l Justification is crucial somewhere between these extremes

Module X.1 - General Principles and Types of Events16 Disadvantages l Without intervention n the existing individual and collective annual doses n the anxieties they cause n the consequent political pressures to remedy the situation

Module X.1 - General Principles and Types of Events17 Disadvantages – Cont’d l Intervention will in addition introduce n costs, harm, and inconveniences n the social disruption n the occupational doses incurred by those implementing the intervention

Module X.1 - General Principles and Types of Events18 Advantages of Intervention l Averted individual and collective doses (reduction in the existing annual doses) l Consequently n reduction in the risk of radiation health effects n reassurance gained by the population n decrease in the political pressure and in the anxiety created by the population

Module X.1 - General Principles and Types of Events19 Optimisation l Not only a positive net benefit, but also a maximised net benefit l Conceptually no difference from optimising protection of sources within practices l The optimum form, scale, and duration of the protective actions should be selected from the justified options of intervention

Module X.1 - General Principles and Types of Events20 Specific Reference Levels l Intervention levels l Action levels l Intervention exemption levels

Module X.1 - General Principles and Types of Events21 Generic Reference Levels l The existing annual dose – conceptually can be used to establish generic reference levels for intervention l The quantity should be used with caution l Preference is given to specific reference levels based on avertable doses

Module X.1 - General Principles and Types of Events22 Recommended Generic Reference Levels l Generic reference level below which intervention is not likely to be justifiable: n existing annual dose about 10 mSv l Generic reference level for establishing protective actions under nearly any conceivable circumstances: n existing annual dose rising towards 100 mSv

Module X.1 - General Principles and Types of Events23 Perspectives

Module X.1 - General Principles and Types of Events24 Specific Prolonged Exposure Situations l High levels of prolonged exposure to natural background radiation l Long-lived radioactive residues in human habitats l Discontinuation of intervention after an accident l Radioactive substances in commodities

Module X.1 - General Principles and Types of Events25 High Levels of Prolonged Exposure to Natural Background Radiation l Radon in dwellings l Natural gamma radiation emitters in building materials l Natural gamma radiation emitters in the ground

Module X.1 - General Principles and Types of Events26 Long-lived Radioactive Residues in Human Habitats l Radioactive residues from practices l Radioactive residues from past human activities and events l Situations of potential exposure

Module X.1 - General Principles and Types of Events27 Discontinuation of Intervention After an Accident l When exposures have decreased to the action levels that would have prompted the intervention or l When the generic reference level of existing annual dose below which the intervention is not likely to be justifiable could provide a basis for discontinuing intervention

Module X.1 - General Principles and Types of Events28 Radioactive Substances in Commodities l Radionuclides may be of natural or artificial origin l As a result of natural processes or as direct result of human activities l A generic intervention level of around 1 mSv is recommended for the individual annual dose l The control of commodities after an accident

Module X.1 - General Principles and Types of Events29 Summary l The ICRP system of protection of the public against prolonged (chronic) exposures provide the radiological protection philosophy for these topics l The numerical values for specific and generic reference levels are just starting points for the discussions leading up to the decisions needed l Quantitative recommendations for prolonged exposure situations must be interpreted with extreme caution

Module X.1 - General Principles and Types of Events30 Where to Get More Information INTERNATIONAL COMMISION ON RADITION PROTECTION Protection of the Public in Situations of Prolonged Radiation Exposure Annals of the ICRP, ICRP Publication 82, Pergamon, 2000