Faulty transformer halves output of new reactor under test operation at Rostov NPP

Publish date: October 20, 2010

Written by: Andrey Ozharovsky

Translated by: Maria Kaminskaya

MOSCOW – A transformer failure at Rostov Nuclear Power Plant (NPP), in Southern European Russia, is said to have been the cause of a 60 percent load reduction in the newly built Reactor Unit 2, still under trial operation, on October 14. Two days later, the faulty transformer was replaced and the reactor taken to projected output levels. The resulting outage – on which information was scarcely made available – cost the grid 28 million kilowatt-hours in lost energy.

According to the Russian top nuclear authority, the State Nuclear Corporation Rosatom, a generator at Rostov NPP’s Reactor Unit No. 2, currently under trial operation pending official commissioning, lost connection to the grid owing to a transformer failure: “At 09:56 pm on October 14, 2010,” Rosatom’s official report said, “Generator G-2 went offline during reactor operation proceeding in pilot production mode at 1,000-megawatt capacity. The unit’s capacity was brought down to 40 percent compared to nominal capacity.”

A standard phrase that accompanies all similar reports on incidents at Russian NPPs concluded that “the limits and conditions of safe operation of the equipment have not been violated.”

The statement was circulated among the members of Rosatom’s Public Council, but it never appeared in the press. None of the Rostov-based ecologists with whom Bellona spoke about the incident said they were aware it had taken place.

The Russian NPP operator company, Concern Rosenergoatom, likewise, offered no report on the incident. The only information posted on Rosenergoatom’s website for October 14 is a report on a tour around the plant organised for local preschoolers.

Information vacuum

Similarly, no information on the incident has been made available on Rostov NPP’s website. The plant’s press secretary Igor Kuksin, when Bellona reached him on the phone, declined to comment, referring all questions to Rosenergoatom’s head office in Moscow.  

“I recommend that you speak to the concern. This is the order of things we have – everything goes through Moscow,” Kuksin said on the telephone from Volgodonsk, where the plant is located, in Rostov Region.

That the press officer at a site where a significant enough operational disruption took place should be so reticent in his dealings with the media as to direct all questions to Moscow begs the question as to what role might be reserved for a press service whose employees are essentially forbidden to talk to the press.

Rosenergoatom’s instinct to control the media cycle and only provide such information as it deems fit to appear in the press is understandable – and even expected in cases when operational hitches amount to mundane occurrences only and represent no significant risk to a nuclear power plant’s safe operation.

A 60 percent reduction in load does not, however, fall into that category. The public and local authorities need to be assured that in case an event of considerable significance occurs at a nuclear power plant, they will be informed duly and in reasonable timeframes, with no further risks to population health and safety brought by either delays or attempts to sweep such information under the rug.

What happened at Rostov NPP?

Bellona managed, however, to obtain more details on the incident from Olga Brednikova, Deputy Head of Rosenergoatom’s Information and Public Relations Department.

Brednikova said the reactor load reduction at Rostov NPP was caused by a “short to ground at a 24-kilovolt generator, which shut the turbogenerator down.”

“A reduction in load to 38 percent of nominal capacity took place, though the reactor remained plugged to the grid. This is a run-of-the-mill occurrence that has no relation to reactor operation,” Brednikova said. “On October 16, at 03:49 pm, after the voltage transformer was replaced, the turbogenerator was taken online; at 09:00 pm, reactor load was restored in full.”  

This means the incident only led to a reduction in the reactor’s output: The energy system experienced a sudden loss of around 600 megawatts’ worth of electricity, which was likely compensated for by redeploying power supply from other regions.

Each of Russia’s 32 nuclear reactors goes off the grid on average 1.5 times a year due to sudden failures in either the electrical or reactor-related systems in operation at the plant. For a reactor operating in a test mode, incidents like this are even more common.

“The equipment is being tested. The reactor unit is considered to be under trial operation,” Brednikova said. “Such episodes fall outside the scope of public information procedure.”

“Successful” trial run – and failure after launch

Rostov Nuclear Power Plant, renamed in 2010 from Volgodonsk Nuclear Power Plant, is located on the left bank of the Tsimlyansk reservoir in the lower stream of the Don River near Volgodonsk, and for now only fully employs one 1,000-megawatt reactor – of the Soviet-designed pressurised-water reactor series VVER-1100 – which was launched in 2001.

A project conceived as far back as the late 1970s to provide energy to Russia’s North Caucasus region, this was the first Russian NPP to be taken online since the tragedy at Ukraine’s Chernobyl. Rostov NPP is now responsible for about 15 percent of power supply in Southern Russia, an area with a population of 17.7 million people.

Construction of the second unit of Rostov NPP, also a VVER-1000 reactor, has seen a fair share of delays and halts after the first brick was laid in 1983 and was finished a year behind schedule in 2009.

Reactor Unit 2 was taken to design-basis power output levels in August this year, and on October 11, Rosenergoatom reported that the reactor had successfully completed its trial operation period, after operating at 100-percent capacity for 15 days. That procedure, a statement on Rosenergoatom’s website said, had “started right after [the] completion of the dynamic trial [and was] the final one at the experimental-industrial operation stage.”

Rosenergoatom also cited Rostov NPP’s Deputy Chief Engineer for Operation Alexei Zhukov, who said the comprehensive testing of the second unit had been carried out in line with the testing programme and confirmed that the reactor equipment was good to operate at nominal capacity under the base load.

“The trial proved [the reactor’s] readiness for bearing the nominal load,” Rosenergoatom quoted Zhukov as saying.

Are construction defects at fault?

As it frequently happens, however, it only took a few days after the celebratory statements before the newly launched equipment failed, proving it was only ready to operate at partial capacity.

Because substandard construction quality and lack of equipment reliability at Russian NPPs are scarcely a secret, it cannot be ruled out that sub-quality equipment or assembly works may have been the underlying cause of the recent generator failure at the site.

In fact, it was only recently that Rostov NPP – and its second reactor – ended up among those nuclear power plants that were red-flagged by the Russian Federal Service for Ecological, Industrial, and Atomic Supervision, or Rostekhnadzor, for using counterfeit materials during construction works.

In its yearly report for 2009, Rostekhnadzor wrote: “Supervisory measures undertaken led to the discovery of 959 units of counterfeit concrete reinforcement supplied to Reactor Unit No. 2 of Rostov NPP. The company […] responsible for the delivery of the mentioned concrete reinforcement had [its] licence revoked.”

Just a legal hiccup

The reactor unit is nonetheless being prepared for fully commercial operation. A process is under way to have all the paperwork ready for the inspection board, which is to rule on commissioning the reactor for commercial production. Before the incident, October 16 was reported as the date when Rostov NPP’s second reactor was expected to have its official launch.

According to Brednikova, however, the current delays are caused by external circumstances:

“The postponement of the date when the commissioning act is to be signed has to do exclusively with legislative matters. There has been no change in plans. The unit is operating stably, if you don’t count dispatch limitations and technical adjustments of the equipment,” Brednikova said.

The legislative matters in question have to do with a recent reorganisation in Rostekhnadzor, which left unclear the issue of which agency is now responsible for commissioning a reactor once it has undergone its pilot production period.

It has apparently been so long since Russia last launched a new reactor that the industry has been left with no legislative basis to lean on when it has a new nuclear power unit to take online.

This provides a certain loophole for Rosenergoatom, the operating company: De facto, the new reactor is online and supplying energy to the grid, but the legal situation is murky enough that should failures occur – as it happened at Rostov NPP – the company has no obligation to inform the public, an advantage afforded by the trial period status.

Reactor Units 3 and 4 are being built to an obsolete design

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Reactor Units 3 and 4 of Rostov NPP are now in initial stages of construction. However, both are still being built to a thoroughly obsolete project – namely, without the now obligatory molten-core catcher (a system that, should serious, Chernobyl-scale damage occur to the reactor core, will be the last line of defence in a severe accident, as it will localise the spread of damage and prevent the worst radiological consequences of the event), on piles installed as long back as twenty years ago, and using parts and structural components that are just as old.   

In the 1990s – a hectic time that was generally marked in Russia by a more pronounced exercise of civil rights and freedoms, as reforms promised to take the country through the transition period from an authoritarian Soviet state to a democratic one – public protests forced the authorities to heed expert opinion and freeze the construction of the first reactor unit, which by then had been completed almost to 95 percent.

But the government has since concentrated enough power in its hands to choose, if it wishes, to dispense with public sentiments or independent expert advice altogether.  

The official launch dates of Reactor Units Nos. 3 and 4, for which construction licences were issued in 2009, are planned for 2014 and 2015, respectively.