LES ACTIVITÉS NUCLÉAIRES : RAYONNEMENTS IONISANTS ET RISQUES POUR LA SANTÉ ET L’ENVIRONNEMENT 3.1.6 – The optimisation principle The optimisation principle, defined by Article L. 1333‑2 of the Public Health Code, states that: “The level of exposure of persons to ionising radiation […], the probability of occurrence of this exposure and the number of persons exposed must be kept as low as is reasonably achievable, given the current state of technical knowledge, economic and social factors and, as necessary, the medical objective in question”. This principle, known as the ALARA(7) principle, requires exposures and discharges to be kept as low as reasonably achievable by applying the best available techniques without compromising the activity, or the level of safety or radiation protection. In practical terms, this means, for example, reducing the quantities of radionuclides present in radioactive effluents from nuclear installations, requiring monitoring of occupational exposure in order to limit it to the strict minimum necessary, and ensuring that medical exposure for diagnostic purposes is within the expected range with regard to the reference level, which serves as a benchmark for optimisation, unless justified by the expected benefits or technical constraints. 3.1.7 – The limitation principle The limitation principle, defined in Article L. 1333-2 of the Public Health Code states that “[…] exposure of a person to ionising radiation […] may not increase the sum of the doses received beyond the limits set by regulations, except when the individual is exposed for medical purposes or for the purposes of research as mentioned in 1° of Article L. 1121-1”. 7. The ALARA principle (As Low As Reasonably Achievable – at the lowest level that can reasonably be achieved) first appeared in Publication 26 of 1977 by the International Commission on Radiological Protection. It was the culmination of a reflection on the principle of optimising radiation protection. Acceptance and implementation of the ALARA principle have evolved significantly in Europe over the last thirty years, with close involvement of the European Commission which resulted in the creation of a European ALARA network in 1991. The exposure of the general public or of workers as a result of nuclear activities is subject to strict limits. These limits include significant safety margins to prevent deterministic effects from appearing, as well as aiming to reduce the appearance of probabilistic effects in the long term to the lowest level possible. Exceeding these limits leads to an abnormal situation and one which may give rise to administrative or criminal sanctions. In the case of medical exposure of patients, no dose limit is set, provided that this voluntary exposure is justified by the expected health benefits for the person exposed. 3.1.8 – The prevention principle To anticipate any environmental damage, the prevention principle, defined in Article 3 of the Environment Charter, stipulates the implementation of rules and measures which must take account of “the best available technology at an economically acceptable cost”. In the nuclear field, this principle underpins the concept of “Defence in Depth”, presented below. 3.2 Some aspects of the safety approach The safety principles and approaches presented below were gradually implemented and incorporate the lessons learned from accidents. Absolute safety can never be guaranteed. Despite all the precautions taken in the design, construction and operation of nuclear facilities, an accident can never be completely ruled out. Willingness to move forward and to create a continuous improvement approach is thus essential if the risks are to be reduced. 3.2.1 – Safety culture Safety culture is defined by INSAG, an international consultative group for nuclear safety which reports to the Director General of the IAEA, as that complete range of characteristics and attitudes in organisations and individuals which establishes that, as an overriding priority, nuclear plant safety issues receive the attention warranted by their significance. Safety culture therefore determines the ways in which an organisation and individuals perform their duties and assume their responsibilities with respect to safety. It is one of the key fundamentals in maintaining and improving safety. It commits organisations and individuals to pay particular and appropriate attention to safety. The organisation must take steps (training, mentoring, preparation and planning of work, etc.) enabling the safety culture to be expressed at all levels of the organisation through a rigorous and prudent approach and a questioning attitude, allowing compliance with the rules to be shared and initiatives to be taken. In operational terms, the concept underpins daily decisions and actions relating to activities. 3.2.2 – The “Defence in Depth” concept The concept of “Defence in Depth” consists in implementing a series of levels of defence based on the intrinsic characteristics of the installation, material, organisational and human measures and System of interdependent fundamental principles, the three sub-culture aspects of ASNR’s organisational system and the three regulation and oversight performance criteria System of fundamental principles Sub-culture aspects Performance of oversight Vigilance Reflexive practice Primacy of experience Mission commitment Hierarchy of issues Subsidiary Authority Structural stability Approach to oversight and regulation Relationship to time Robust decisions Efficient inspections Effective incentives 116 ASNR Report on the state of nuclear safety and radiation protection in France in 2025
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