ASN Report 2017

381 ASN report on the state of nuclear safety and radiation protection in France in 2017 Chapter 13  - Nuclear fuel cycle installations ASN considers that the operation of the facilities located within the perimeter of this Areva NC BNI includes satisfactory management of the risks and detrimental effects. The commissioning of the new “emission zone” (EM3), intended to replace the existing emission facility, where the depleted UF 6 will be heated so that it can be injected into the W plant process, is envisaged for 2018. ASN considers that the steps taken by the licensee to manage the operational risks of the EM3 facility are on the whole acceptable. ASN considers that the sizing of the facility and its equipment with respect to external hazards and extreme natural hazards, as presented in the stress tests, is satisfactory. ASN considers that the TU5 and W facilities continue to be operated with a relatively satisfactory level of safety. Relations with the licensee are sustained and constructive The Areva NC uranium conversion plants – BNI 105 BNI 105, which notably transformed reprocessed uranyl nitrate into UF 4 or U 3 O 8 , is being decommissioned (see chapter 15). ICPEs not necessary for operation of the BNI are included within its perimeter with respect to the risks that they create for the safety of the BNI itself. These ICPEs carry out fluorination of UF 4 into UF 6 so that it can be subsequently enriched. Each year, they produce about 14,000 tonnes of UF 6 from the UF 4 coming from the Areva NC Comurhex facility in Malvési. Their status is that of an ICPE subject to licensing with institutional controls (“Seveso” installations) and they are subject to the system of financial guarantees for ensuring the safety of the installations and, finally, to Directive 2010/75/UE of the European Parliament and Council of 24th November 2010, known as the “IED Directive” on industrial emissions (integrated pollution prevention and reduction). The new fluorination unit, called “Comurhex 2”, scheduled for commissioning at the beginning of 2019, will be replacing the fluorination unit of the Comurhex 1 plant which was shut down at the end of 2017 as it no longer complied with current safety standards. ASN had authorised its continued operation until this deadline and required the performance of work to reinforce this plant, in particular mitigation means to limit the consequences of a major hazardous gas leak in the process buildings, the anticipated shutdown of the installations (storage of propane and ammonia, recycling of the hydrofluoric acid), extension of the gas knock-down system and improvement of the safety system to make it independent of the control system. Reinforcement work was carried out in 2017 after the discovery of a seismic resistance fault on the “gravel” embankment of the Donzère-Mondragon canal site, so that the mitigation means can carry out their functions in the event of an earthquake (see box below). FOCUS Fault in the seismic resistance of the Donzère-Mondragon canal embankment On 22nd August 2017, Areva notified a significant event concerning the inability to demonstrate the resistance to a Safe Shutdown Earthquake (SSE) of a portion of the Donzère-Mondragon embankment. The Tricastin site could thus be flooded in the wake of an earthquake. The main risks concerned the Comhurex 1 and W former chemical facilities, in which the toxic gas knock-down spray systems could become unavailable in such a situation. In its resolution CODEP-CLG-2017-039439 of 28th September 2017 ASN asked Areva to reinforce these provisions before 31st October 2017. For Comurhex, the improvements made consisted in installing water pumping equipment on a floating barge moored to concrete blocks to prevent it drifting when the water rises, in positioning spray-guns producing a water curtain on weighted raised blocks to maintain them above the flood level and in prepositioning these guns according to the wind direction such that the water curtain is correctly oriented to protect the populations and so that the operators do not have to intervene in the field under any releases. For the W plant, ASN asked Areva NC to guarantee the operability of the means used to mitigate the consequences of a release of hydrofluoric (HF) acid gas in the plant’s “emission zone” in the event of a flood following a breach in this portion of the embankment after a SSE. Areva NC therefore built a protection wall around the equipment designed to produce a curtain of water to knock-down any toxic cloud. EDF also undertook reinforcement work on the embankment to ensure its seismic resistance (see chapter 12, point 2.4.5). Reinforcement of Comurhex spray systems following the event notified on 22nd August 2017.