France’s nuclear safety authority (Autorité de Sûreté Nucléaire - ASN) has asked Areva NC to increase its oversight of evaporators at the La Hague nuclear fuel processing facility after greater levels of corrosion than expected were found. In February, ASN asked Areva NC to increase supervision of the evaporators and to install isolation facilities and advanced detection systems to limit the consequences of a leak or rupture. ASN has now imposed a number of additional measures. Areva NC has been asked to define the criteria that would require permanent shutdown of the evaporators, such as the minimum thickness of their walls. Areva NC must also strengthen controls and checks on the thickness of the evaporator walls.
ASN said there should be increased monitoring of maintenance shutdowns, and plans must be prepared to deal with any emergency resulting from the development of a hole in an evaporator. Results of all tests must be compiled in reports to be sent to ASN twice a year. The evaporators are used to increase the concentration of fission products in liquid waste produced from processing. They were commissioned between 1989 and 1994 and designed for an operating lifetime of 30 years. This liquid is highly radioactive. The evaporators are in the UP3-A processing plant, which has a processing capacity of around 800t a year of used nuclear fuel. La Hague has an overall capacity for the annual processing of used fuel from 80 to 100 nuclear reactors, amounting to 1,700t.