(523.5123) WISE Amsterdam - Several buildings at the Blayais nuclear power plant, north of Bordeaux located on the Gironde estuary, were flooded on December 27, and an internal emergency was declared early December 28. Two units will still be down for a while, due to inspection and repair of safety systems and concrete structures. The storm has shown the terrible vulnerability of the centralized French electricity system, due mainly to the large nuclear power plants.
The waters of the Gironde were pushed by the winds over the protective dike around Blayais, which houses four reactors. Units 2 and 4 were stopped in the evening of December 27, unit 1 around 12.00 on December 28; unit 3 was already shut for maintenance. Invading the site through underground service tunnels, the waters flooded the pumps of unit's 1 Essential Service Water System (ESWS). This disabled the residual heat removal system, which is necessary to cool the reactors. Shortly afterwards the flood waters reached the spent fuel buildings for units 1 and 2, knocking down their safety inspection system and containment spray system too. After the internal emergency was declared, firefighters from nearby town Blaye assisted Blayais' own flood-fighting team. On December 30, the ESWS resumed operation and Blayais-4 was restarted. Electricité de France (EDF) needed its power badly to power the southern grid, which was no longer connected to the north.
When safety authorities learned that one ESWS was unavailable, that the waters had possibly
affected a pump of the second ESWS and that two other safety systems were also out of order, they
became very nervous. After all, the safety system is called essential. EDF said that the level of
the Gironde river during the storm had been higher than the millennial level against which the dike
around Blayais was designed.
EDF has been busy for some weeks now to remove mud, to inspect the equipment for damage and to
restore units 1 and 2.
The French national safety agency DSIN allowed EDF to repair provisionally the pumps, motors and
valves of the safety inspection system and the containment spray system of units 1 and 2. Since the
incident, the two reactors had been cooled through steam generators. After the provisional repair,
EDF brought units 1 & 2 to cold shutdown, to allow installation and qualification of the new
equipment and the repair of the safety systems. EDF first planned to restart units 1 & 2 by
early January. But plant management later declared that other piping and concrete structures were
being checked.
According to Quintin of the regional inspectorate and Goelnner, assistant director of DSIN, the dike was inadequate, the service tunnels were not protected against flooding and the equipment was simply not correctly designed. Safety authorities will require redesign of safety systems, to make sure that such an incident does not happen again. DSIN said that EDF would not convince anyone that the level of the Gironde waters exceeded historical levels. Compared to the requirements of original safety report for Blayais, the dikes were insufficient. An inspection at Blayais on November 10 1999, made DSIN to ask EDF why work on the dikes was delayed. Before the incident, EDF declared that the underground tunnels also were perfectly safe. DSIN required that the site's flood protection system was improved before it would give the green light for restart of units 1 and 2. It could take some months before EDF has done all required repairs and redesign work.
Incident rated at INES level 2
The flooding event was originally rated at Level 1 of the International Nuclear Event Scale, but
on December 29, it was uprated to Level 2. There was no doubt of its severity because multiple
safety systems failed. The impact of the December storms on Blayais' core melt frequency is being
calculated by the Institute of Protection & Nuclear Safety (IPSN).
The main reason why the national electricity grid was hit so hard by the storm is that the masts of the grid were not designed to withstand such heavy storms but also because the middle-voltage grid lines are mainly aboveground and thus very vulnerable. In other countries a larger part of the lines are underground. EDF will do research after the possibility to put more power lines underground, but to put high tension lines underground is ten to twenty times more expensive than above-ground lines. The research is expected to take some ten years.
Sources:
- Nucleonics Week, 6 January
- De Standaard (Belgium), 8 January 2000
Tel: +33-4-7828 2922; Fax: +33-4-7207 7004
Email: rezo@sortirdunucleaire.org
WWW: www.sortirdunucleaire.org
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