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Assessment of the EU stress tests

Wenisch and Becker

The March 2011 accident at the Fukushima I nuclear power plant proved that highly unlikely incidents cannot be excluded. Contrary to accepted practice Probabilistic Safety Assessments (PSA) do not constitute a sufficient basis to declare a plant operation safe. Safety of nuclear power plants needs to be backed by deterministic assessments, which excludes initiating events and accident scenarios only if they are proven to be physically impossible.

Events at Fukushima compounded public mistrust towards nuclear power worldwide. In Europe, the European Commission welcomed a suggestion by the government of Austria to conduct stress tests at all nuclear power plants in the European Union. The EU nuclear safety regulators –ENSREG –took over this task. The tests were introduced to improve confi-dence in the safety of European nuclear power plants (NPPs). In particular, they should examine the consequences of earthquakes and floods, and the com-bination of events previously excluded. However, the tests would be limited in scope: safety features such as ageing or design faults would not be taken into account.

Assessment of stress tests
An assessment of the stress tests –by Antonia Wenisch and Oda Becker, commissioned by Greenpeace- is published recently: Critical Review of the EU Stress Test performed on Nuclear Power Plants. 

The EU stress tests are not a safety assessment of the European nuclear power plants. They represent a limited analysis of the vulnerability of such plants with respect to natural hazards. The accident scenarios are focused on external events: the quality of the struc-tures, systems and components and the degradation of the oldest nuclear power plants in Europe are not subject of the analysis. The peer review team did not consider all safety issues that could trigger or aggravate an accident situation (e.g. ageing, use of MOX fuel, safety culture).

The design of the plants with respect to natural events varies, therefore the safety margins can only be assessed through an engineering judgment. In December 2011, the IAEA has published a new guide for extreme weather hazards. Greenpeace recommends that all plants make an assessment of weather hazards according to the new IAEA guide.

Severe accident management, espe-cially regarding spent fuel pools and multi-unit accidents like at Fukushima, is an issue everywhere, but the way it is tackled varies immensely. Only one country (Slovenia) has a simulator for severe accident management.

The peer review team has not assessed the current safety level of the European nuclear power plants, but only the potential increase in the level of safety in the next decade. Currently, there are several known shortcomings with respect to the protection against earth-quake, flooding and extreme weather. Furthermore, it is well known that it will be impossible to cope with a severe accident,  especially if it is accompa-nied by earthquake or flooding. The reviewers only described the weaknes-ses they identified, but not an overall assessment of all facts, which would allow a risk

The EU stress tests have no direct effect on the European nuclear power plant fleet. ENSREG has no say on the lifetime extension applications of even the oldest plants with the most obvious problems (Mühleberg, Doel, Rivne etc.). To gain an accurate picture of nuclear risk, EU decision makers should add a third leg to the nuclear stress tests - a full assessment of emergency response preparedness, which examines the viability of emergency response plans, address weaknesses and purpose improvements.

Far from restoring faith in the safety of nuclear power in Europe, the stress tests and ENSREG report published in April 2012 serve to further undermine it. At their most basic level, nuclear plants are concrete shielding to a fission process that creates large quantities of energy. Energy Commissioner Oettinger has acknowledged that the elimination of risk at such facilities is impossible, with efforts limited to merely minimising the threat. Across Europe, the stress tests have revealed some unacceptable failures in risk management. Serious gaps have repeatedly been found in readiness for emergencies. No guarantee can be given that plants operating in earthquake zones will remain safe in the event of serious seismic activity. Many lack any form of safe containment for their spent fuel pools and some have entirely inadequate access to emer-gency power. In short, the lessons from Fukushima are clearly yet to be learned in Europe.

Yet some plants are located just 10 kilometres from major urban populations like the city of Antwerp, raising the question why evacuation plans were not considered as part of the stress tests. The tests also failed to consider the impacts of multiple disaster scenarios as experienced at Fukushima in 2011 - the very crisis that originally prompted the stress tests. On top of these questionable omissions, the test results are not standardized in any way, making comparisons effectively impossible. The results are lack of any kind of pass or fail criteria and the partiality of those carrying and vetting the tests and falls short of providing the relevant authori-ties with the necessary information to draw proper conclusions.

When EU heads of state and government meet in autumn 2012 to discuss the results of this exercise, they can only conclude that the stress tests and peer review fall far short of expectations. They should recognise that nuclear power will always remain a dangerous technology. This is why all European governments should develop a credible phaseout plan for nuclear power 
in Europe, starting with the most risky reactors.

Source: Critical Review of the EU Stress Test performed on Nuclear Power Plants. Study commissioned by Greenpeace. Authors: Antonia Wenisch, Oda Becker, May 2012 (Published 14 June 2012)
Both the full report and the executive summary are available at:
Ing. Antonia Wenisch, Mail: antonia.wenisch[at]
Dipl. Phys. Oda Becker, mail: oda. becker[at]