The principles of radiation protection

The new chapter III "Ionising Radiation" of part III of book III of the legislative part of the Public Health Code aims to cover all "nuclear activities", that is all activities involving a risk of human exposure to ionising radiation, emanating either from an artificial source, whether a substance or a device, or from a natural source when the natural radionuclides are or have been treated owing to their fissile or fertile radioactive properties. It also includes "interventions" aimed at preventing or mitigating a radiological hazard following an accident, due to environmental contamination.

The general principles of radiation protection (justification, optimisation, limitation), established internationally (ICRP) and incorporated in the above-mentioned directive 96/29/Euratom, are enshrined in the Public Health Code (article L. 1333-1). They constitute guidelines for the regulatory action for which the ASN is responsible.

1°) The principle of justification – "A nuclear activity or intervention may only be undertaken or carried out if its health, social, economic, or scientific benefits in relation to the risks inherent in the human exposure to ionising radiation which it is likely to entail so justify."

Depending on the type of activity, decision-making power with regard to justification lies with different levels of authority: it lies with the government for issues of general interest, such as whether or not to resort to nuclear energy, it is delegated by the Minister for Health to the ASN in the case of sources used for medical, industrial and research purposes, it is the competence of AFSSAPS when authorising use of a new irradiating medical device and is the responsibility of the doctors when prescribing and carrying out diagnostic or therapeutic procedures.

Assessment of the expected benefit of a nuclear activity and the corresponding health drawbacks may lead to prohibition of an activity for which the benefit would not seem to outweigh the risk. This prohibition is either generic (for example: ban on the intentional addition of radioactive substances in consumer goods), or the licence required with regard to radiation protection will be refused or will not be renewed. For existing activities, justification may be reassessed if current know-how and technology so warrants.

2°) The principle of optimisation – "Human exposure to ionising radiation as a result of a nuclear activity or medical procedure must be kept as low as reasonably achievable, given the current technological, economic and social factors and, as applicable, the medical purpose involved."

This principle, referred to by the acronym ALARA (as low as reasonably achievable), for example leads to a reduction in the discharge licences of the quantities of radionuclides present in radioactive effluent from nuclear installations, to mandatory monitoring of exposure at the workstation in order to reduce it to the strict minimum necessary, or to supervision to ensure that medical exposure resulting from diagnostic procedures remains close to the predetermined reference levels.

3°) The principle of limitation – "Exposure of an individual to ionising radiation resulting from a nuclear activity may not raise the sum of the doses received beyond the limits set by the regulations, unless this person is being exposed for medical or biomedical research purposes."

The exposure of the general population or of workers as a result of nuclear activities is subject to strict limits. These limits comprise significant safety margins to prevent the appearance of deterministic effects. They are also far below the doses at which probabilistic effects (cancers) have begun to be observed (100 to 200 mSv). Exceeding these limits is considered to be unacceptable and in France, can lead to administrative or legal sanctions.

In the case of medical exposure, no strict dose limit is established in that this voluntary exposure is justified by the anticipated health benefits to the person exposed.