Third quarter of 2001

A blind re-start

The Safety authority gives the green light for the re-start of Cattenom 3. (12 pages, 97 Ko)

WISE-Paris, 28 September 2001

[Posted 28/09/2001]

After a 7-month shutdown, during which the Operator discovered damage to the fuel on a scale that had never been experienced before on any French reactor, Unit 3 at the Cattenom nuclear power station restarted on 9 September 2001. France's Nuclear Safety Authority actually gave the green light for its restarting on 31 August 2001, despite the fact that the enigma of the phenomenon that caused the damage has not been solved yet.

After intervention by members of the parliament of Luxembourg, Luxembourg's Minister of Foreign Affairs stressed to the French authorities "that a meeting of the Joint Franco-Luxembourg Commission on Nuclear Safety should be convened as quickly as possible."

In all, 92 fuel rods -containing uranium and constituting the first level of containment of radioactive material- were damaged. Some were completely broken, allowing radioactive material to be disseminated into the primary cooling fluid. This represented a "first" in the numbers of sealing faults, given that five to ten faults are observed on average per year in all of the 58 reactors in the France. The usual annual figure of 0.1 rods was multiplied by 1000.

Serious damage to fuel elements can lead to risk of jamming of the control rods and therefore to loss of control of the chain reaction, with potentially grave consequences for reactor safety.
In October 1999, just a month after restarting of the reactor, an abnormal level of radioactivity was detected in its primary cooling water and, on 6 September 2000, the "Serious Cladding Failure" level was reached. The safety authorities were only informed of this situation on 18 October 2000, a delay judged "inadmissible" by the authorities.

In spite of the high level of leakage and recommendations from the safety authorities to bring forward shutdown of the reactor, the management of the Cattenom power station preferred to keep it running. Prior to shutdown of the reactor, the power station's management was unable to provide an accurate assessment of the number and gravity of faults. This error of foresight will have long-term repercussions, especially for radiological protection and management of the Unit 3 buildings.
Several hypotheses have been put forward to explain the appearance of these faults. In addition to wear and vibration, the presence of a possible "migrating body" or even the possibility of a "manufacturing defect" have been suggested. And, while "the immediate cause linked to vibration fatigue" has been identified, this does not make it possible to "confirm or exclude potential factors with certainty."

In parallel with this situation, EDF informed the Safety Authority, on 12 March 2001, that it had detected a generic fault in valves in the emergency cooling system in 12 reactors in the 1300 megawatt-of-electricity (MWe) series (including those of Cattenom); a fault that could affect their satisfactory operation in case of accident. More precisely, this flaw affected the re-circulation system supplying the emergency spray and injection systems, of fundamental importance in the concept of nuclear safety. EDF's analyses led to the conclusion that there was a risk of jamming in case of "serious accident or high-magnitude earthquake."

Shortcomings in the area of nuclear safety on EDF sites, characterized by a "persistent lack of rigor" have been observed on numerous occasions by the Safety Authority. The case of Cattenom appears to constitute a serious example.

To download the briefing in English: 010928BriefCAT-v1-Ang.pdf (12 pages, 97 Ko)
To download the annexes in French : Part 1 (12 p., 550 Ko) and Part 2 (10 p.,711 Ko)

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