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28 March, 2012

Safety Check

The results of stress tests run at Ukraine’s nuclear power stations are comforting but fail to explain why the facilities' equipment malfunctions so often

The need to thoroughly re-evaluate the country's existing nuclear power stations became apparent in the aftermath of the Fukushima-1 accident. Europe decided to run stress tests in March 2011, and Ukraine immediately declared it was joining the initiative.

The European programme has three stages: first, re-evaluation is carried out by national operators (Enerhoatom in Ukraine). Second, these reports are checked by national regulators, i.e., government bodies that regulate everything having to do with nuclear engineering and radiation safety (the State Inspection for Nuclear Regulation in Ukraine). At the third and final stage, reports of national bodies are studied on the European level and final conclusions are worked out for each nuclear plant. Public discussion of stress tests in late 2011 completed the first stage and ushered in the second.

The main conclusion drawn by Enerhoatom is comforting: “Everything is normal. There is no reason to worry. Events similar to what happened at Fukusima-1 are, first, impossible in Ukraine and, second, even if they were possible, our nuclear plants would withstand them.” It should be said for the sake of justice that this statement is very much like those made by national operators in other countries – they have all reported that their nuclear plants are as safe as possible and ruled out any major accidents. But we could see that coming. It is hard to imagine that a company that owns nuclear plants would admit they are unsafe and should be stopped immediately. Consequently, not everyone in Ukraine or elsewhere is buying the official re-evaluation results.

Stress tests have largely been carried out on paper only – models have been built to assess the impact of external forces, the reliability of the equipment and its ability to withstand extremely high stress. Benchmark scenarios included combinations of earthquakes, floods, extreme temperatures, tornadoes and hurricanes. But this assessment is purely theoretical. It remains ultimately unclear how the equipment will react in real situations. Large-scale tests modelling a massive failure of the equipment have not been performed.

On 24-25 May 2011, accident-counteracting training took place at the Europe’s biggest nuclear power plant located in Zaporizhzhia. It was presumed that the plant was hit by a combination of an earthquake, a flood caused by a wave coming from the Kakhovka reservoir and a loss of diesel generators in the 6th unit. The model predicted that electricity supply would be resumed using diesel generators in other units. But events at Fukusima-1 show that it is quite possible that the cooling systems of three units may fail at the same time, followed by reactor storage pools. The stress tests did not answer the question: How can long-term cooling be secured for three to four units and storage pools at the same time?

Incidentally, the second unit at the Zaporizhia Nuclear Power Plant was disconnected from the grid by the emergency protection system on 12 November 2011. It was tentatively suggested that the equipment malfunctioned due to old age and outdated technology. Two days later, the unit was back in operation, but malfunctions occur at this plant regardless of stress tests. At the very least, this means it is impossible to foresee every event that could cause an accident.

The Fukusima-1 accident once again proved that there is no such thing as a safe reactor. Representatives of the nuclear sector keep repeating the mantra that the threat of a large-scale accident is extremely small. But history contradicts mathematic probability. In a little over 30 years, humankind had to deal with as many as five meltdowns – one in the USA (1979), one in Ukraine (1986) and three in Japan — an average of one every six years.

Furthermore, the economy of nuclear power engineering is also rather dubious. The safety-enhancing programme for Ukraine’s nuclear power plants will alone cost €1.5 billion. Nuclear power engineering is always a compromise between safety and economy, and it is becoming increasingly hard to strike the right balance after Fukusima-1.

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