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Science

Details hazy with criteria for nuclear stress tests

Despite calls for a stress test, it may take months to define the precise criteria to be examined. In the meantime, some scientists have a few ideas of what elements should be considered.

Günther Oettinger, EU energy commissioner

Oettinger called for nuclear stress tests across Europe

On Tuesday, following an ad-hoc meeting of European environment ministers, nuclear safety chiefs and industry leaders, the EU energy commissioner announced a series of “stress tests,” of all the entire continent's 143 nuclear reactors.

"We want to look at the risk and safety issues in the light of events in Japan," said Günther Oettinger, the commissioner, after the meeting in Brussels.

But, no one - including the European Commission itself - seems to know exactly what a nuclear stress test is. In fact, it may be weeks, or even months, before precisely what criteria are examined, or which experts will be consulted.

"We have an agreement to do these stress tests, but how and when - these will be discussed in a high-level meeting next week," said Nicole Bockstaller, a spokesperson at the European Commission, who noted that the meeting was just a first step.

Experts meeting in Brussels

Nuclear safety cooperation across the European Union is unprecedented, experts say

"It has been agreed to work on stress tests on the basis of certain criteria: exposure to floods, earthquakes, backup systems of power supplies and reactor type and age," she told Deutsche Welle. "Of these criteria, these are still questions that need to be decided in the [coming] weeks."

'Nuclear stress test' dismissed as rhetorical device

However, nuclear experts agreed that this type of pan-European examination was unprecedented across the continent, where previously, nuclear regulation has been exclusively controlled at the national level.

"I don't know what is meant by the concept of 'stress test,'" said Riku Mattila, a senior inspector of nuclear reactor and safety systems at Finland's Radiation and Nuclear Safety Authority (STUK).

Mattila also told Deutsche Welle that 20 percent of electricity in Finland is produced by four nuclear power plants, with a fifth plant currently under construction.

On Wednesday, the Czech state-owned power company CEZ - which is planning to spend $25 billion on five new nuclear reactors over the next decade - dismissed such calls as hysterical.

"We continue to check the safety and integrity of our nuclear stations, but 'stress test' is a political phrase with no meaning," Kriz told the Dow Jones news service, noting that his company would assist any further European safety tests of its two existing nuclear plants.

The Fukushima Daiichi nuclear power station

The Fukushima Daiichi station is at risk of spewing further harmful materials into the air

Other experts, like Laurence Williams, a professor of nuclear safety at the University of Central Lancashire in the United Kingdom, and the former British Chief Inspector of Nuclear Installations, agreed, adding that they have yet to be consulted on such stress tests.

"I don't know how they're going to judge the ability to pass the stress test," he said, pointing out that all nuclear power states were already members of the International Atomic Energy Agency. This requires them to report the level of their plants' safety at both a national and international level.

Possible starting points

Williams suggested that a starting point might be checking the existing reports and records that are already on file to see if those match up with accepted regional norms.

Other scientists suggested re-examining the ability of nuclear reactors to function under significantly reduced power, which is usually required to keep the nuclear material cool during a shutdown procedure.

In the recent case at the Fukushima Daiichi nuclear power station, normal access to the power grid was knocked offline, as was a diesel backup. The electrical battery secondary backup was not sufficient, which has already led to some amount of radioactive leakage.

"If [a] flood were to overcome the diesel generators as it did in Fukushima, what would our response be?" asked Neil Hyatt, a professor of nuclear materials chemistry at the University of Sheffield in the UK. "Is there something now that we hadn't anticipated with Fukushima that we can deal with?"

Fukishima reactor

Europe is unlikely to experience the same magnitude of earthquake as Japan

Other scientists noted that while much of Europe is not likely to sustain a magnitude 9.0 earthquake of the type that recently hit Japan, it is not immune to seismic activity, which could cause damage to nuclear power stations.

Frank Scherbaum, a seismology professor at the University of Postdam in Germany, urged European policymakers to focus at least some of their stress tests towards the probability of seismic movements.

"It answers the question: how likely is a particular level of ground motion to be exceeded?" he told Deutsche Welle. "It's my belief that probabilistic seismic risk analysis for nuclear power plants would be a much better way to deal with risk."

He noted that it is possible to combine certain known conditions about the ground upon which nuclear power plants were built with historical seismological record to come up with a "hazard integral," which can then be compared against what the building was designed to withstand.

"If this kind of analysis would identify where the design value is exceeded [by a high amount], there would be a problem with the design safety," he said. "We don't know what the relative safety of our plants is."

Author: Cyrus Farivar
Editor: Andrew Bowen

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