- 8 - The law also makes provision for interim measures taken to safeguard public security, safety and health or to protect the environment. ASN may therefore: temporarily suspend the operation of a BNI, immediately informing the Ministries responsible for nuclear safety, in case of any serious and imminent risk; at any time, stipulate the evaluation and the implementation of the measures necessary in the event of a threat to the above-mentioned interests. In parallel with ASN's administrative actions, reports can be drawn up by the ASN inspectors and forwarded to the public prosecutor's office. 6. The French approach to the complementary safety assessments (CSAs) As with the Three Mile Island and Chernobyl accidents, detailed analysis of the experience feedback from the Fukushima accident could take about ten years3. The Fukushima accident, triggered by an earthquake and a tsunami on an exceptional scale, confirmed that despite the precautions taken in the design, construction and operation of the nuclear facilities, an accident is always possible. In this context, and given its knowledge of the 150 French nuclear facilities, through its regulation and oversight, ASN considered in the days following the accident that a complementary assessment of the safety of the facilities, with regard to the type of events leading to the Fukushima disaster, should be initiated without delay, even if no immediate emergency measures were necessary. These assessments were carried out in addition to the safety approach performed permanently and described previously. These complementary safety assessments are part of a two-fold approach: on the one hand, performance of a nuclear safety audit on the French civil nuclear facilities in the light of the Fukushima event, which was requested from ASN on 23rd March 2011 by the Prime Minister, pursuant to article 8 of the TSN Act and, on the other, the organisation of "stress tests" requested by the European Council at its meeting of 24th and 25th March 2011. 6.1 Specifications consistent with the European specifications In order to manage the complementary safety assessments, ASN issued twelve decisions on 5th May requiring the various licensees of the nuclear facilities to perform these complementary safety assessments in accordance with precise specifications. The complementary safety assessments concern the robustness of the facilities to extreme situations such as those which led to the Fukushima accident. They complement the permanent safety approach followed. To ensure consistency between the European and French approaches, the French specifications for the complementary safety assessments were drafted on the basis of the European specifications produced by WENRA4 and approved by ENSREG5 on 25th May 2011. The provisions of the French specifications are consistent with those of the European specifications. The complementary safety assessment thus consists of a targeted reassessment of the safety margins of the nuclear facilities in the light of the events which took place in Fukushima, that is extreme natural phenomena (earthquake, flooding and a combination of the two) placing considerable strain on the safety functions of the facilities and leading to a severe accident. The assessment first of all concerns the effects of these natural phenomena; it then looks at the loss of one or more systems important for safety involved in Fukushima (electrical power supplies and cooling systems), regardless of the probability or cause of the loss of these functions; finally, it deals with the organisation and the management of the severe accidents that could result from these events. 3 It should be remembered that after the Three Mile Island accident, it took six years to evaluate the proportion of the reactor core which had melted. 4 WENRA: Western European Nuclear Regulators Association 5 ENSREG: European Nuclear Safety REgulators Group
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