Storm shutdown at Cruas

02 December 2009

One reactor at France's Cruas nuclear power plant was forced to shut down this morning when rainstorm debris affected cooling water intakes.


An automatic shutdown occurred at around midnight on 1 December after debris washed in from the Rhone river, which provides cooling water for the four reactors on site. An intake was shuttered automatically, with the rest of the reactor systems following. Only Cruas 4 was affected due to its position upstream of the other power units.


Cruas' four reactors use cooling towers as well as river water
enabling operators to balance effects on the Rhone


The loss of some cooling capability is serious for nuclear power plants given their operational requirement for a major heat sink. The possibility that debris floating along a river could cause coolant intakes to close is anticipated, and under French regulations requires the activation of an internal emergency plan including a coordination centre to liaise with local authorities and national regulators. This facility was closed down after around five hours, when the intake had been cleared and normal cooling restored.


The Nuclear Safety Authoirity (Autorité De Sûreté Nucléaire, ASN) categorised the event at Level 2 on the International Nuclear Event Scale, an 'incident' which involved a degradation of safety margins but with no consequences.