Банкеръ Weekly



The final rating of the incident that occurred in block V of the Kozlodoui nuclear power station on March 1 is second level on the INES scale, the Nuclear Regulatory Agency (NRA) announced on May 8. The confession came just a few days after NRA Chairman Sergey Tsochev repeated his assurance that the failure was at zero or first level and it wasn't therefore necessary to inform the International Atomic Energy Agency (IAEA). But now the situation is changing radically and the agency will have to explain in writing the reasons that caused the accidental suspension of the 1000 megawatt reactor. The branch leaders and the managers of Kozlodoui will also have to explain why they hid the gravity of the incident from the people for two months and even misled them.
Let's recall the chronology in brief. It was written in the unique announcement published on the NRA website on March 14: According to preliminary information from the Kozlodoui EAD nuclear power station, the event is classified at zero level on INES. Eleven days later the regulator informed the IAEA that in its preliminary report the Kozlodoui power station assessed the incident as first level on the INES scale. Since both announcements were based on the preliminary report of the nuclear power plant, someone might think that the plant made two different assessments - one on 14 and another on 25 March. But according to art. 11, paragraph 1 of the Regulation on the order and terms for informing about events in nuclear facilities, the preliminary report is to be sent to the NRA within 24 hours after the event is registered. Therefore, the existence of two preliminary assessments is impossible and it turns out that the nuclear regulator used two different standards: one for domestic use and another - for usage abroad.
It was also surprising to hear a statement that in accordance with the above mentioned regulation the agency received on April 28 the final report on the Kozlodoui event in which the incident is classified at first level. However, art. 12, paragraph 1 of the same regulation reads that this document on the investigation results and the analyses made is to be sent within one month from the date on which the event is registered. It means that the final report was one month late, but the NRA fails to comment on this fact.
The Energy Minister Roumen Ovcharov appeared in a similar situation. He repeated many times on 25 and 26 April that nothing special happened in block V and the people were correctly and thoroughly informed through the NRA release. Four days later, after visiting the plant, the Minister already thought the incident would rather be classified at second level. Taking into account the INES guidance, a second level is to be given when in case of a real failure in the course of working with a damaged safety system a grave injury of the active zone would happen.
The one-level increase in the rating of the incident is mainly provoked by the failure of a large number of elements for the same reason and a defect of the procedures, Sergey Tsochev told journalists. On May 4, the Kozlodoui plant management finally announced in public that the incident occurred because of sticking of 22 of all 61 elements for plugging in the reactor protection management system and that the sticking was provoked by the long trouble-free operation of block V.
According to Borislav Stanimirov, Deputy Chairman of the NRA, if the main constructor, the Russian Hydropress company, fails to prove the elements safety and does not propose correcting measures, the block may not be put in operation after the summer repair. Still, it seems strange why the regulator is demonstrating such strictness only now and not before allowing the replacement of the disastrous sheaves of rods that are put into the reactor to stop its operation. Conceding guarantees is obligatory for the issuance of such permission, the Law on the Safe Use of Nuclear Energy stipulates. Moreover, the NRA regulations themselves require several documents before such replacement begins: a licence for the change in the reactor project (issued by the main constructor of the facility), a reactor safety certificate, as well as a certificate of the producing company issued by the respective national regulator to prove its ability to make nuclear equipment elements. The only thing that is clear today is that the system for drive of the replaced 61 sheaves has no safety operation certificate. We failed to find out whether there is a licence issued by the main constructor of the VVER-1000 reactors and whether the producer, the Russian Hydropress company, is certified to produce nuclear equipment. The only answer NRA Chairman Sergey Tsochev gave to all questions was that permission had been issued to Kozlodoui nuclear power plant to fulfil the repair works and that it expired in the end of 2005.
The nuclear power plant managers put all the blame on Hydropress. According to them, the sheaves supplied by the Russians had not been tested for their ability to endure long enough without being stirred. The sheaves have remained outside the active zone for 197 days because of the trouble-free operation of block V. No Russian reactor has remained plugged in for so long - their record lasts 55 days, Kozlodoui Deputy Executive Director Ivan Genov explained. According to him, it was the inertness of the rods that made the mobile and the immobile parts of the mechanism which moves them stick.
The sheaves have a perfectly polished surface and the fact that they remained adjoined for so long caused the passing of atoms from the surface of one part to the other, the Kozlodoui Board of Directors member Yordan Georgiev added. This phenomenon is known from the metallography but was not taken into account by the Russian specialists during the projects tests. A designer, especially in the nuclear energy, must not design elements without considering how a nuclear plant operator can act in every situation, Georgiev underlined. In fact, the same sheaves have been operating without failure for five years in the Balakovo nuclear power plant, for three years in the Kalininska nuclear power plant, and for one year - in the Zaporozhska nuclear plant. They have only shown defects in Bulgaria and because of the damages endured Bulgaria will now insist that Hydropress pay the 3% performance guarantee arranged by the agreement. The entire value of the contract amounts to USD24MN, therefore the Russians will have to pay USD720,000. Moreover, the Kozlodoui managers will insist that they are compensated for five of the sheaves destroyed for the purposes of analysis and for finding out the reasons for the failure of the moving mechanism.
According to the plant director Ivan Ivanov, the first two financial claims will be satisfied easily since they have been arranged by the agreements signed. However, much more furious debates are expected with Hydropress for the funds lost because of the decommissioning of the 1000-megawatt block. The National Electricity Company (NEC) already requested that Kozlodoui nuclear power plant pay a BGN2.8MN forfeit for the energy amounts not delivered during the ten-day break. We are probably going to go to court with the Russians for this amount, Ivanov predicted. By the way, NEC may lay additional claims for the losses it missed because of the disturbed schedule for export of electricity to neighbour countries.
In practice, by making such statements the plant managers ruled out throwing the blame on Bulgarian experts or on the teams that were on duty when the incident occurred. Once received, the sheaves have been tested on the ground, then installed by Bulgarian technicians under the supervision of the Hydropress chief engineers, Yordan Georgiev said. They haven't been tested for staying immobile for a long time, but they could not have been tested since that has not been written in the project specification. According to Ivan Ivanov, the staff has acted properly and no one will be held personally responsible. I may be the only one to be punished for not having learned to behave with the media properly, he assumed.
A small detail seems to have remained unnoticed in all this noise - it is not yet known exactly why the rods did not descend in the zone of the reactor. And, respectively, is it possible that this happens again? The Deputy Director of the plant Ivan Genov said that it was impossible for the sheaves to stick again, because they would be stirred every week. Such advanced practice may be working in kinesitherapy for old people, for example, but we are talking about nuclear energy here. And it is an area where all possible scenarios must be rehearsed in advance and adequate reaction must be prepared.
Anyway, the Kozlodoui plant managers are no longer positive about the Russian equipment. The same sheaves must be installed in block VI in the summer, but they will remain packed for some time at least. We are talking with Hydropress and insist that they prove their new construction is stable. The solution they will propose us must be tested by the time, Ivan Ivanov said. However, this creates another serious problem - will block VI be able to work with the present rods since their guarantee is to expire at year-end? The plant managers assure that the Russians will conduct a research and if the results fail to be positive and there is no firm guarantee, they will not let block VI operate. Therefore, it seems possible that at the beginning of 2007 the Kozlodoui plant will lose not only blocks III and IV but also one of its 1000-megawatt reactors.

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