Post-Fukushima complementary safety assessment outcomes for French fuel cycle facilities

• Natural events are considered with a higher level than taken into account at design.
• Deterministic loss of cooling and electrical supplies is postulated.
• Strengthen some “key” SSCs, called the “hardened safety core”, is necessary.
• These measures are about to enhance their ability to withstand extreme hazards.
• The emergency organization has to be enhanced to take into account extreme events.

The Complementary Safety Assessments (CSAs), requested in France by the Prime Minister in spring 2011 after the Fukushima-Daiichi accident have been performed by the nuclear licensees in 2011. The facilities have been divided into three categories, depending on their vulnerability to accidents like those at Fukushima and on the importance and the scale of the consequences of any accident affecting them. AREVA nuclear fuel facilities were part of the top priority facilities. The stresses that have to be considered for the CSAs are natural hazards (earthquake and flooding in particular) higher than what is required in the current design standards and the deterministic loss of power supply and cooling functions. The outcome of the studies carried out by the fuel cycle facilities licensees is that these facilities ensure a sufficient safety level. However, the IRSN analysis showed that it is necessary to implement a “hardened safety core” of robust material and organizational measures aiming, for extreme situations, to:-prevent a severe accident or limit its progression,-limit massive discharges resulting from a non-controlled accident,-enable the licensee to fulfill its crisis management duties.The “hardened safety cores” proposed by the fuel cycle facilities licensees have been assessed by IRSN. Even if complements are necessary, regarding the “hardened safety core” provisions and associated requirements, IRSN has estimated that the corresponding equipment and measures are about to enhance the ability of the facilities to withstand extreme hazards or supply losses.