Nuclear reactors spark concerns over lack of safety/control separation

London - The UK nuclear safety regulator (HSE ND), the French nuclear regulator (ASN), and the Finnish nuclear regulator (STUK) have all raised issues with AREVA regarding the control and instrumentation (C&I) systems of its flagship nuclear reactor. AREVA’s Evolutionary Power Reactor (EPR) pressurised water reactors are currently being built in France and Finland, while EdF plans to deploy the units in the UK.

The issues concern the adequacy of the safety systems that maintain control if the EPR nuclear reactor goes outside normal conditions and their independence from the control systems used to operate the plant under normal conditions, according to HSE ND.

“Although the EPR design being developed for each country varies slightly, the issues we raised with the current C&I system are broadly similar, our aim being to collectively obtain the highest levels of safety from the EPR,” said a joint statement from the three authorities.

According to the HSE, independence of the safety and control systems is important there should be no possibility that the systems could fail together. The EPR design, as originally proposed by the licensees and the manufacturer, AREVA, doesn’t comply with the independence principle, as there is a very high degree of complex interconnectivity between the control and safety systems, it said.

The licensees and AREVA, have agreed to make architectural changes to the initial EPR design which will be reviewed, added the regulators. As the designs for use in each country are similar, it is likely that the solution will be similar, although not necessarily identical, taking into account individual licensees’ requirements and national regulatory requirements or practises, they said.

“As an example, in providing defence-in-depth, different solutions could be proposed to back-up safety systems. In all cases, however, the solutions will lead to equivalent high levels of safety,” said the regulators’ joint statement.

For its part, AREVA said the regulators’ concerns were part of the “constant dialogue” between operators, constructors and nuclear safety authorities is an integral part of the certification and construction processes for new reactors. “The safety of the EPR reactor has not been called into question and AREVA is currently working with the regulators in each country to make the necessary adaptations to meet local standards,” insisted a company statement.

According to AREVA,  STUK had requested further information on the C&I of the EPR and the documentation, back in December 2008. An AREVA/Siemens consortium, it said, met these requests, providing all further general information which had, furthermore, been validated by the customer, TVO.

In the UK, the HSE ND brought up various points relating to the proposed configuration of the C&I system and AREVA and EDF are working together to adapt it to meet local requirements. The UK regulators, EDF and AREVA are confident that they will find a solution, said the company. In October, the French ASN sent a letter to EDF requesting additional information on the C&I system. AREVA and EDF say they will provide the requested answers by year-end.

AREVA claims its EPR reactor is the most powerful reactor in the world and meets the highest safety standards. EPR reactors are currently being built in Finland, France and China and the certification process is underway in the U.S. AREVA is working closely with the authorities in each country to determine how its model can respond to various local issues. The company says it also aims to introduce a global standardisation for its C&I model.