Regulators highly critical on EPR control and command system

Nuclear Monitor Issue: 
WISE Amsterdam

Not only the AP1000 is under fire, also the EPR becomes more and more subject of doubts regarding safety questions by the official safety authorities in countries where the reactor is built (Finland, France) or should be built (U.K.) Now the French Nuclear Safety Authority (ASN) has just published a letter to EDF, which questions in the most serious way the ability of the control and command system of the EPR being built in Flamanville to meet safety requirements. Like British and Finnish authorities did before, ASN makes appropriate answers to these doubts a condition to the future operational license of the reactor.

In June, the U.K. Nuclear Installations Inspectorate (NII) wrote to EDF and Areva, to express their concerns about the control and instrumentation (C&I) of Areva’s European Pressurised Reactor (EPR). C&I governs the computers and systems that monitor and control the station’s performance, including temperature, pressure and power output levels. The NII, said the EPR technology was significantly compromised because of the interconnectivity of what were meant to be independent systems designed to operate the plant and ensure its safety.

The Health and Safety Executive, which oversees the NII, said that the EPR design could be rejected for use in Britain if its concerns could not be satisfactorily addressed. “It is our regulatory judgment that the C&I architecture appears overly complex,” the NII letter said. “We have serious concerns about your proposal which allows lower safety class systems to have write access [the ability to override] to higher safety class systems,” it continued.
The letter also highlighted concerns about the absence of safety display systems or manual controls that would allow the reactor to be shut down, either in the station’s control room or at an emergency remote shutdown station.
The NII said that it would grant a license for the EPR reactor only if it was satisfied that the reactor design could be built and operated safely and securely.

That was late June, a few days later, on July 2, the Finnish safety authority raised similar concerns, but the French safety authority ASN remained very silent. It would not comment and said it was on the process of assessing this part of the design itself.

Now, on November 2, the French safety regulator, together with the safety authorities of Finland (STUK) and U.K. (HSE), released a ‘Joint Regulatory Statement on the EPR Pressurised Water reactor’ (letter dated 22 October).

The three authorities consider that "the EPR design, as originally proposed by the licensees and the manufacturer, AREVA, doesn’t comply with the independence principle" of safety and control systems, which is a basic safety principle.

In its letter to EDF, ASN concludes that "the complexity of the architecture proposed by EDF makes it difficult to provide a satisfying demonstration of the safety" and states that its acceptability is subject to changes in the design and complementary justifications. Furthermore, "the analysis of these elements [to be provided by EDF] by ASN and its technical support will be a preliminary condition to the examination of the receivability of [EDF's] future demand of operational license for the Flamanville-3 EPR reactor" [rough translation from French].

The design failure seems to be so deep that ASN even raises doubts on the feasibility of overcoming it and fulfill standard safety principles. The letter to EDF concludes that "given the range and complexity of the demonstrations that remain to be provided in order to justify that [the system] meets these principles, the ASN judges that there is no acquired certainty to build an acceptable demonstration of safety on the basis of the current architecture". Therefore ASN asks EDF, in parallel to trying to provide this justification, to "examine as from now arrangements for different options of conception"[again, rough translation from French].

Sources: Nuclear Monitor: 691, 16 July 2009 / HSE, ASN, STUK: Joint Regulatory Position Statement on the EPR, 22 October 2009 / Letter WISE-Paris, 2 November 2009
Contact: Yves Marignac. WISE-Paris. 31-33 rue de la Colonie, 75013 Paris, France.
Tel.: +33 1 45 65 47 93

WISE Paris