Safety fears raised at French reactor

Safety fears raised at French reactor

Anti-nuclear activists are seeking to halt construction of France’s latest-generation nuclear power plant at Flamanville, on the Normandy coast, arguing that changes introduced to solve problems with the reactor’s fuel pellet cladding have invalidated the plant’s original building permit.

Didier Anger, head of the anti-nuclear action committee Crilan, and a former member of the European parliament, said the bid to block, or at least delay, construction of the EPR reactor had been made in a letter from the committee to the French nuclear safety authority, the ASN.

Areva, the state-controlled French nuclear engineering company, is already battling construction delays and cost overruns at both Flamanville and Olkiluoto, in Finland, where it is building the first of its EPR plants. EPR originally stood for European Pressurised Reactor, a name that Areva subsequently changed to Evolutionary Power Reactor when it sought US certification.

Areva has said that it would book a 400 million euros, or $516 million, first-half charge against cost overruns on the Olkiluoto project, bringing its total write-downs on the facility to 2.7 billion euros-- close to the 3 billion euros it estimated in 2005 as the cost of the entire job. The plant was originally due to go online up last year but is now expected to be operational in 2013.

Power output

Areva and EDF say the EPR represents a giant leap forward in terms of reactor design, performance and safety. They say that it can achieve an operating output of 4,500 megawatts - far more than earlier designs, so unit production costs will be lower; that it uses a type of fuel that will extend the fuel cycle; and that it can operate more flexibly, allowing power output to be reduced so that some reactor maintenance work can be carried out at low power, cutting down on shutdowns.

Asked to comment on the significance of safety and performance issues highlighted in the leaked documents, an EDF spokeswoman played down their importance, describing the documents as merely ‘working papers.’

Yet, among the leaked documents, one dated February 2007 — just before the construction of the Flamanville plant was approved — reported that technical studies by EDF had shown that the EPR’s original core design had failed to meet safety criteria for a control rod ejection accident at high power.

In the scenario defined as a serious accident, the zirconium alloy used to clad the radioactive fuel will melt, producing hydrogen, which — if it comes into contact with the core’s cooling water — can cause an explosion violent enough to breach the reactor vessel and release radioactive materials beyond the containment building.

Accident conditions

Radiation, especially in accident conditions, can cause equipment to malfunction. Equipment required to ensure reactor safety must be qualified to keep working under accident conditions involving the breaking of 10 per cent of the fuel rods. But according to an April 2009 document, some equipment used in the EPR design would fail if 1 per cent of the rods were to break, leaving the plant vulnerable in an accident.

The ASN will soon issue limitations on radioactive and other wastes for the Flamanville reactor, based on the 2006 application, Wack said. Yet, changes to the core have modified and increased the amount and types of radioactive and chemical waste produced.

Both EDF and the security regulator insist that safety is a top priority. Yet Wack acknowledged that the use of mixed oxide, or MOX, fuel — a blend of plutonium and uranium oxides, for which the EPR reactor is designed — is intrinsically more risky than the uranium oxide fuel used in most nuclear plants. Because it is more highly radiated, it is more complicated to use, store, transport and manage in case of an accident.

EDF papers dating from 2007 pinpointed MOX fuel use as partially responsible for poor safety test results relating to reactor operations in both high-power and very low-power conditions. Operations in those conditions would not be allowed unless EDF could demonstrate that the safety criteria were met. That, however, raises the issue of how to determine the worst-case scenarios to be taken into account.

Nuclear operators would like to modify the existing methods to give more weight to statistical risk assessment, to argue that some scenarios are so improbable that they can be discounted. The problem with that, however, is that the probability of events is determined somewhat arbitrarily by industry experts.