CEZ, a.s. : Czech Republic Completed Its National Report on Nuclear Power Plant Stress Tests

On October 31, 2011, ?EZ submitted its "Final Reports" on stress tests conducted at Czech nuclear power plants. After their evaluation, the State Office for Nuclear Safety prepared a "National Report" and submitted it to the European Commission.

The Final Reports on the safety of both nuclear power plants in the Czech Republic have over 400 pages in total. They were prepared by tens of CEZ' experts over a period of six months, who also consulted specialists from other institutions, such as the Nuclear Research Institute in ?e? and the Czech Technical University in Prague. The evaluation procedure confirmed the power plant's resistance and did not reveal any safety fault that would require immediate action.

In their analyses, the experts assessed the resistance of the Temelín and the Dukovany NPP's to very unlikely external influences. For example, they evaluated how both power plants would handle an earthquake stronger than they are designed for, temperatures dropping to -46°C for an entire month or, on the other hand, long-term hot weather with temperatures reaching 46°C. Water was also in focus as experts analyzed what would happen to the Temelín NPP if a ten-thousand-year flood occurred on the nearby Vltava due to a collapsed dam at the Lipno reservoir, or if precipitation had reached the maximum over the past ten thousand years.

"The design plans of both power plants are very robust and still have a buffer to withstand even such extreme natural influences," Vladimír Hlavinka, Member of ?EZ' Board of Directors and Production Division Director, recapitulates the conclusions of the reports in respect of natural influences. "The stress test results are consistent with our philosophy of proactively dealing with nuclear power plant safety; we continuously check and improve the relevant plans. Based on our own evaluations or recommendations made based on international audits, we have in the past implemented tens of improvements on both power plants," Vladimír Hlavinka added. The staff training level is also very high, with personnel in both power plants regularly practicing the handling of various non-standard situations including coping with accidents beyond the design plans.

In their safety analyses, which were the basis for the final reports, the experts purposely simulated the failure of safety systems and their additional security levels, and they assessed how the units would handle serious accidents. "Everything was of course conducted in line with safety studies and engineering calculations. It was not real-life testing. The results showed us some opportunities for further improving the resistance of nuclear units, even to extremely unlikely scenarios and unforeseeable conditions," Hlavinka continued.

The new measures will also aim at further strengthening our safety systems and equipment. For example, units at Temelín will be equipped with a further back-up power supply source. Additional mobile diesel generators will represent the eleventh source of power supply. Additional levels of safety will also be implemented in the hydrogen elimination containment system. Recombiners prevent hydrogen from accumulating up to a concentration that becomes explosive in combination with air. "We have recombiners available that can handle accidents for which the plant is designed, and we are going to increase their number to cope with accidents beyond the design levels," Milo? ?t?panovský, Temelín NPP Director, briefly pointed out on additional measures.

The hydrogen elimination containment system will also be strengthened in Dukovany. The number of recombiners there will also be increased to cope with accidents beyond the design plans. "At the Dukovany NPP, we are going to complete our current ongoing projects to further improve the power plant's resistance to earthquakes, and we will also finalize and practice procedures for accidents beyond the scope of design plans. Since 2007 we have been taking similar steps in respect of a beyond the scope of design-basis black-out of the site," Tomá? ?ák, Dukovany NPP Director, commented on the additional measures to be implemented.

The Czech "National Report" prepared by State Office for Nuclear Safety together with analogous reports from other EU Member States will now be examined by international nuclear power experts in the EC. The Commission is going to announce the stress test results in mid 2012.

Ladislav K?í?, CEZ Spokesman

Published: 2. 1. 2012