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French regulator to EDF: don't assume new reactor model is accident-proof

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French regulator to EDF: don't assume new reactor model is accident-proof
FILE PHOTO: An EDF worker is seen on the construction site of the third-generation European Pressurised Water nuclear reactor (EPR) in Flamanville, France, November 16, 2016. REUTERS/Benoit Tessier   -   Copyright  Benoit Tessier(Reuters)
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By Geert De Clercq

PARIS (Reuters) – French nuclear regulator ASN warned state-controlled utility EDF that it may have to review parts of the design of its new nuclear reactor model if it hopes to get clearance to build it.

EDF’s current “European Pressurised Reactor” (EPR) model – the world’s largest reactor with 1,650 megawatt (MW) capacity – has suffered years of delays and billions of euros of cost overruns at construction sites in France and Finland as its size and many safety features make it unwieldy to construct.

In a bid to make it easier to build, EDF unit Framatome – formerly called Areva – is now designing a new “EPR 2”, which will be cheaper and less complex, most notably because of the single steel-lined concrete hull for its containment building as opposed to the EPR’s double hull.

In initial talks with the ASN, EDF <EDF.PA> had proposed to design the new EPR 2’s cooling circuit pipes with the same “break preclusion” concept as in the old EPR, of which EDF is building two at Hinkley Point, Britain.

This means that components are manufactured to such a high standard that breakage is ruled out and the manufacturer therefore does not have to make plans for what to do in case of accident.

This break-preclusion concept – which is inherently dangerous according to anti-nuclear organisations – has shown its limits at the EPR under construction in Flamanville, France where badly executed weldings on the main steam lines will lead to new delays and extra costs.

The ASN said in a statement on Thursday that while the overall design of the new EPR 2 seemed to be safe, EDF would have change certain elements for it to be approved, notably the break-preclusion concept for its cooling circuit.

“Given what has happened in Flamanville, the IRSN is not in favour of the application of this concept on the main steam line of the EPR 2,” Karine Herviou, in charge of new reactor designs at IRSN, the technical arm of the ASN, told Reuters.

Following disasters in Chernobyl, Ukraine in 1986 and Fukushima, Japan in 2011, reactor safety design has been tightened at every level, beginning with component design, manufacturing and maintenance.

Operators must be able to detect all anomalies so that incidents do not turn into accidents, and reactors must have features to mitigate serious accidents such as cooling water leaks or core meltdown.

Since the first pressurised water reactors were built in the United States in the 1970s, manufacturers have applied the break preclusion concept to reactor vessels and steam generators, manufactured to such high standards that breakage was ruled out.

In France, this accident-proof concept was also applied to parts of the secondary cooling circuits of EDF’s 58 reactors, and for the EPR to an even larger area of these circuits.

If EDF is not allowed to apply the concept, it will have to provide additional safety features such as safeguards to prevent the steel pipes flailing around and damaging other equipment if they buckle under the 80-bar pressure.

A source at EDF said the utility would respond to the ASN’s concerns about the EPR 2 design by 2020.

(Reporting by Geert De Clercq; editing by David Evans)

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