ASN Report 2020

the ageing of these facilities or the shutdown of the effluent- producing facilities. Examples include the Radioactive Effluent and Waste Treatment Station (STED) at Fontenay-aux-Roses, BNI 37-B at Cadarache, STE2 at the La Hague plant and the Brennilis STE. The difficulties associated with the decommissioning of the STEs are closely dependent on their shutdown conditions, particularly the emptying and rinsing of their tanks. The major difficulties associated with the decommissioning of the support facilities are as follows: ∙ poor knowledge of the operating history and the state of the facility to be decommissioned, which necessitates prior characterisation of the old waste and the analysis of samples of 5. Earthquake considered for the equipment constituting the “hardened safety core” of the facilities. The term “hardened safety core” was defined after the Fukushima Daiichi NPP accident to identify the ultimate equipment controlling the vital safety functions in an extreme situation (earthquake, winds, tornado, extreme flooding, etc.). the sludge or deposits in the STE tanks. This characterisation necessitates firstly the development of methods and the use of specific equipment to take the samples, and secondly the availability of analysis laboratories; ∙ the difficulty in accessing the waste for retrieval was not taken into consideration in the design (silos, trenches, concrete- lined pits, cramped premises, etc.), necessitating the costly construction of infrastructures in conformity with current safety requirements and leading to long retrieval times and unforeseen events; ∙ the deterioration of the containment barriers, for example corrosion of waste drums or pollution of soils resulting from the occurrence of significant events during operation. 3. ASN actions related to facilities being decommissioned: a graded approach 3.1  The graded approach according to the risks of the facilities ASN ensures the oversight of facilities undergoing decom­ missioning, as it does for facilities in operation. The BNI System also applies to definitively shut down facilities. ASN has imple­ mented an approach that is proportional to the extent of the risks or drawbacks inherent to the facility. In this respect, ASN has divided the facilities under its oversight into three categories from 1 to 3 in descending order of the severity of the risks and drawbacks they present for the interests mentioned in Article L. 593-1 of the Environment Code (ASN resolution 2015‑DC‑0523 of 29 September 2015). This BNI classification enables the oversight of the facilities to be adapted, thus reinforcing oversight of the facilities with major implications in terms of inspections and the depth of the examinations conducted by ASN. The risks with facilities undergoing decommissioning differ from those for facilities in operation. For example, the risks of signi­ ficant off-site discharges decrease as decommissioning progresses because the quantity of radioactive substances decreases. The requirements concerning the systems for controlling the risks associated with the decommissioning operations therefore tend to decrease as decommissioning progresses. ASN considers that it is generally not appropriate to undertake reinforcement work to the same extent on a facility undergoing decommissioning as on a facility in operation, provided that the decommissioning is actually carried out and leads to a reduction in the hazard sources within a short period of time. 3.2  Lessons learned from the Fukushima Daiichi accident To take into account the lessons learned from the nuclear accident that occurred at the Fukushima Daiichi NPP in Japan, ASN asked the BNI licensees to carry out stress tests, including on those facilities undergoing decommissioning. The stress test procedure has been divided into three lots according to the safety risks inherent to the facilities. The facilities being decommissioned are essentially in lots 2 and 3. For the facilities in lot 2, the post-Fukushima assessments have led ASN to request the removal of radioactive substances or the reinforcement of emergency management means on centres that often also have facilities in operation (see chapters 11 and 12). For civil facilities undergoing decommissioning, the main challenges concern the La Hague site facilities. For example, the licensee has put in place operational provisions for extinguishing a fire in silo 130 following a “hardened safety core” earthquake (5) . Silo 115 must also be further protected against the fire risk and ASN has asked the licensee to study measures to speed up implementation of this programme. Integration of the lessons learned from the Fukushima Daiichi accident for the facilities presenting more limited risks shall The Covid-19 pandemic caused the stoppage of many decommissioning worksites in spring 2020, due to the travel restrictions put in place by the Government. Some critical decommissioning and Waste Retrieval and Packaging (WRP) worksites, particularly in facilities operated by Orano, like the “High Activity Oxide” (HAO) facility, were nevertheless able to continue some of their activities. These stoppages or slowdowns have pushed back reaching certain milestones by several months, particularly in the taking of samples or the effective conducting of certain decommissioning operations. Alongside this, the widespread recourse to remote working also induced delays in the performance of certain studies and the submission of files required by the regulations. At the end of the first lockdown, the work on the suspended worksites gradually resumed satisfactorily, in compliance with the health rules in effect. During the second lockdown, the licensees implemented protocols enabling the worksites to continue by restricting the number of people present on site, in accordance with the Government’s instructions. This adapted way of functioning enabled the licensees to limit the impacts of the crisis on the course of the decommissioning operations. THE IMPACT OF COVID-19 ASN Report on the state of nuclear safety and radiation protection in France in 2020 347 13 – DECOMMISSIONING OF BASIC NUCLEAR INSTALLATIONS 13