ASN Report 2017

421 ASN report on the state of nuclear safety and radiation protection in France in 2017 Chapter 15  - Decommissioning of Basic Nuclear Installations 2.1.3 The Gas-Cooled Reactors Bugey 1, Chinon A1, A2 and A3, Saint-Laurent-des-Eaux A1 and A2 constitute the Gas-Cooled Reactors (GCR). These first- generation reactors functioned with natural uranium as the fuel and graphite as the moderator. They were cooled by gas. There are two types of GCR: “integrated” reactors, whose heat exchangers are situated beneath the reactor core inside the pressure vessel, and “non-integrated” reactors whose heat exchangers are situated on either side of the reactor pressure vessel. Bugey 1 reactor (BNI 45) The Bugey 1 reactor is an “integrated” GCR. Complete decommissioning of the installation, for which final shutdown became effective in 1994, was authorised by Decree of 18th November 2008. The corresponding scenario involved decommissioning the reactor pressure vessel “under water”. If the change of scenario envisaged by EDF (“in air” instead of “under water”) is accepted, a new decree will be necessary: the Bugey 1 reactor was to be the first EDF reactor of the GCR type to be decommissioned, but EDF wants to change decommissioning strategy, which will push back the end of decommissioning of the Bugey 1 reactor by about fifty years with respect to the initially prescribed date. ASN is examining EDF’s new strategy for the decommissioning of its gas-cooled reactors (see point 2.1.1). ASN considers that the current decommissioning work on the Bugey 1 reactor is proceeding with a satisfactory level of safety over the short term. However, the event in 2107 where a package fell during handling shows that EDF must be particularly attentive to the handling of components and packages. In 2017, EDF did not resubmit its file concerning the operations to extract operational waste from the reactor pressure vessel, in which radiation protection was to be explicitly taken into account. During its inspection of the head office departments on 14th December 2017, ASN asked EDF to provide justifications for this postponement. In 2017, ASN examined the periodic safety review guidance file for Bugey 1, for which the conclusions report must be submitted before the end of 2018. The main demands of ASN concern the ageing of the structures and their behaviour over time, and the behaviour of the reactor pressure vessel with respect to seismic stresses. Chinon A1, A2 and A3 reactors (BNIs 133, 153 and 161) The Chinon A1, A2 and A3 reactors are “non-integrated” GCRs. They were shut down in 1973, 1985 and 1990 respectively. Reactors A1 and A2 were partially decommissioned and transformed into storage facilities for their own equipment (Chinon A1 D and Chinon A2 D). These operations were authorised by the Decrees of 11th October 1982 and 7th February 1991 respectively. Chinon A1 D is currently partially decommissioned and has been set up as a museum since 1986. Chinon A2 D is also partially decommissioned and accommodates the Intra EIG (Economic Interest Grouping) (robots and machines for intervening on accident-stricken nuclear installations). The complete decommissioning of the Chinon A3 reactor was authorised by the Decree of 18th May 2010 with an “under water” decommissioning scenario. The change of scenario envisaged by EDF will necessitate a new decommissioning decree. This is because the Chinon A reactors were initially to be decommissioned last, whereas with the new strategy, Chinon A2 would be decommissioned first. EDF considers that the decommissioning of a “non- integrated” GCR would present fewer difficulties than that of an “integrated” GCR. ASN is currently analysing the overall acceptability of this change of strategy (see point 2.1.1). Decommissioning of the heat exchangers (first step in the decommissioning of the facility) of the Chinon A3 reactor began several years ago and is now continuing after an interruption of several months due to the presence of asbestos. With regard to the Chinon A2 reactor, further to the results of the first analyses of the components removed from the reactor systems, additional analyses are going to be carried out to determine the treatment strategy for this waste. The depollution of chemically polluted soils is in progress. Groundwater monitoring has been stepped up and completion of the complementary characterisation of the gaseous discharges is planned for early 2018. Decommissioning of the Chinon A3 heat exchangers.