- 129 - insufficient to damage the structures or civil engineering works performing a safety function or housing systems or equipment participating in such a function. Only the IPS equipment situated outside buildings is liable to be damaged by such projectiles. The majority of the equipment important for safety is situated inside the buildings and thus protected from any risk of damage. Moreover, as a general rule, light objects (weighing less than about 2 kilos) or low rigidity items (heat insulation, branches, etc.) are not likely to damage outdoor IPS equipment. Nonetheless, on the occasion of the latest periodic safety reviews, EDF defined a baseline for safety requirements concerning protection against projectiles generated by extreme winds. This baseline defines heavy and lightweight projectiles considered at all altitudes and in all directions, according to a speed taking account of past events and the regulations. This baseline also defines "targets" to be protected and stipulates a combination of loss of site electrical power supplies with loss of the heat sink. However, EDF did not include the IPS-NC equipment situated outside the civil engineering structures in this baseline, something that ASN has asked EDF to remedy in the next periodic safety reviews. Hail In its CSA reports, EDF states that hail was not considered in the design of the units. Lightning In its CSA reports, EDF states that the protection of the facilities against lightning is in conformity with the ministerial order of 15th January 2008 (concerning lightning protection of certain classified facilities) abrogated and replaced by the order of 19th July 201131. According to the approach to lightning protection adopted by EDF, the preventive measures and protection systems must ensure that the consequences of a lightning strike on the safety of the facilities are encompassed by those defined in the initial design of the reactors with regard to category 2 incidents (frequency of less than 10-2 per reactor and per year). In accordance with the above-mentioned order, an analysis of the lightning risk was carried out to demonstrate the environmental acceptability of the consequences of a lightning strike, using an approach based on standard NF EN 62305-2 of 2006 ("Lightning protection: risk evaluation"). EDF states that further to this study, preventive measures and protection systems will be defined, with a view to implementation on 1st January 2012. Before this date, the equipment installed in compliance with the prior regulations32 is monitored in accordance with standard NF C 17-100. Lightning can have direct effects (when the impact is directly on the building's structure) as well as indirect effects (lightning strike in the vicinity of the structure or the building). With regard to direct effects, the buildings and structures of the NPPs comprise at least level II protection as defined in standard IEC 61024 or NFC 17100. Protection is provided by a mesh cage. Pipes and tanks are by their very nature protected against lightning. With regard to the indirect effects, various measures are implemented by EDF (antennas and piping grounded, measurement cables shielded and connected at one end, etc.). With regard to the lightning hazard, the EPR is designed in accordance with the "lightning safety baseline applicable to the EPR". Adequate steps are thus taken to ensure that the safety functions of the systems and equipment necessary to bring the unit to a safe state and to prevent and mitigate radioactive releases are not unacceptably affected. The chosen hazard characteristics are those concerning protection level I, as defined by standard NF EN 62 305-1, or NF C 17-100. Given the lighting protection measures taken, EDF considers that the consequences of a lightning strike on the safety of the facilities are effectively covered by those defined at the initial design of the units with regard to a category 2 incident. 31 Order of 19th July 2011 amending the order of 22nd October 2010 concerning the classification and paraseismic construction rules applicable to "normal risk" class buildings 32 Article 35 of the order of 31st December 1999 as amended, stipulating the general technical regulations for preventing and mitigating nuisances and external risks arising from the operation of basic nuclear installations Order of 28th January 1993 concerning lightning protection of certain classified facilities
RkJQdWJsaXNoZXIy NjQ0NzU=