The Russian State Nuclear Corporation Rosatom’s Crisis Management Centre has issued a short statement on the incident, reporting discontinuation of power supply to the grid at Reactor Unit 4 of Kursk NPP, which occurred on the night of October 20: “Reactor Unit No. 4: Unit disconnected from the grid. At 02:33 a.m. on October 20, 2010, the unit was disconnected from the grid while operating at a capacity of 1,040 megawatts.”

On the following day, a warning signal came from the plant’s automatic background radiation monitoring system. According to Rosatom, “On October 20, 2010, one event was entered into logs with values exceeding the ‘warning alarm’ setpoint of the gamma radiation control detectors of the automatic radiation monitoring system in the monitoring area of Kursk NPP.” The statement proceeded to say, however, that the exceeding radiation levels were related to a “detectors calibration test.”

But the Russian NPP operator company, Concern Rosenergoatom, went ahead with a more confident assertion that radiation levels were within safe limits at the plant, as it said in a statement of its own: “On October 20, 2010, at 02:33 a.m., power unit No.4 of Kursk NPP was shut down by [the actuation of the automatic protection system], caused by generation of a false signal. The reasons are being studied. The shutdown was performed in accordance with [procedure]; no shutdown deviations [were] detected.”

Rosenergoatom said the event was classified as a zero level (below the scale) event on the International Nuclear Events Scale (INES), namely, that it had no impact on the plant and personnel safety.

It also said “no violations of limits and conditions of safe operation of Kursk NPP power units have been registered. The radiation background at the plant and in the adjacent territory is not changed and corresponds to […] natural environmental values.”

On October 25, Rosenergoatom reported on its Russian website that Reactor No. 4 of Kursk NPP had been taken back online three days after the emergency shutdown. The statement, however, offers no explanations of the incident other than saying the scram had occurred owing to a false signal that triggered the activation of the protection and safety system.

Was there a radiation release?

The Rosatom statement does not make it exhaustively clear whether the monitoring system’s warning signal was a false positive – or if after the reactor was scrammed normal gamma radiation levels were indeed exceeded at the plant. Another explanation is possible as well, which is that certain actions were undertaken by staff while running the calibration test on the radiation levels detectors which may have led to the system generating a false signal.

In a surprising turn of events, a call from Bellona Web to the town of Kurchatov in Kursk Region, where the plant is located, revealed that the press service of Kursk NPP was unaware that the warning signal had been sounded in the first place.

“The [monitoring system] functions in an on-line mode, with all the information going to Moscow, to [Rosatom’s Crisis Management Centre]. It can get processed faster over there,” Kursk’s press service said.

The case of two Internet doubles

As far as the scramming incident itself, brief information about it did appear in the Russian press, but no official information was available on Rosenergoatom’s Kursk NPP website at http://kunpp.rosenergoatom.ru/eng/ at the time the Russian original of this story was posted on Bellona’s website on October 21.

Kursk NPP’s press service explained to Bellona that the plant had a second website – at http://kunpp.info/ – which did offer information about the October 20 scram.

There is little clarity as to which of the two websites is the “more official” source of information about the plant. Several years ago, almost all of Russia’s ten nuclear power plants each had a website of their own, which they would maintain with the help of their own resources. The “doubling” of Internet sites – aside from the obvious reason of the operator company providing, on its official web pages, basic information about its subsidiaries to the public – can also be explained by the presumed need on Rosenergoatom’s part to control what information about the plants actually reaches the public.

The kinds of facts that can make their way onto the “unofficial” websites maintained by the nuclear power plants, or the little “nuclear towns” that they operate in – accidents, incidents, and various operational violations (of which there are many year in, year out, according to the Russian federal oversight authorities), alcohol abuse problems among the staff, or social woes plaguing the host town – could be meant as simple, straightforward coverage of the NPP’s day-to-day life, but may in theory turn out damaging to the concern’s interests in keeping up an attractive public image for the industry.

After Rosenergoatom, for reasons of “streamlining” the flow of information about its subsidiaries, ordered all “unofficial” websites to be transferred under Moscow’s purview, the sites started slanting heavily toward such “filtered” content as nuclear officials’ exchange visits, sporting events, or “Miss Atom” competitions.  

Another emergency that involved a Chernobyl-type reactor

Before any information was posted on Rosenergoatom’s website, a short report appeared on Kursk NPP’s own website, which was later re-posted in the official domain – and said only that the generation of a false emergency protection system signal caused a reactor shutdown.

The notable detail is that this was a scram event – a full shutdown, rather than reducing the reactor’s load to a minimum controlled power level. The language is different from that of the Rosatom report, which said only that the reactor had been unplugged from the grid.

The main concern remains with the fact that the reactors operated at Kursk NPP are graphite-moderated models of the RBMK-1000 series – the infamous design used at Ukraine’s Chernobyl.

The 1986 catastrophe at Chernobyl revealed a disastrous defect that characterises this type of reactor: Because of a phenomenon called an “iodine pit,” at least several days must pass before it is safe to take the reactor back online again. An iodine pit, or an iodine hole or xenon pit, occurs when neutron absorbers with a short half-life build up in the reactor core and temporarily disable the reactor due to so-called “reactor poisoning.” The main isotopes responsible for this are iodine-135 and xenon-135, hence the name.

Their presence in the reactor is one of the main reasons for its power fluctuations in reaction to changes of control rod positions. Because an iodine pit can severely undermine reactor control, time must be allowed to pass before the iodine and xenon isotopes are fully decayed.

A scram of an RBMK reactor means, essentially, that the reactor will have to remain offline for at least several days – Kursk NPP took it back online three days after the latest shutdown – costing the grid millions of kilowatt-hours in lost energy. In the case of Kursk NPP, that’s 24 million kilowatt-hours daily.

Kursk NPP declined to comment on when the reactor was planned to resume operation at the time Bellona Web reached the plant’s press centre shortly after the incident.

“There is a schedule for grid synchronisation, but we do not divulge it,” Kursk NPP’s press service said.

Energy losses

Kursk NPP operates four RBM-1000s with thermal power capacity of 3,200 megawatts each, and nominal power capacity of 1,000 megawatts.  

Each of the Kursk NPP reactors has an efficiency factor of 31.25 percent – in other words, over 60 percent of the heat emitted during the nuclear reactions taking place in the power unit is absorbed by the environment, in particular, heating up the 22-square-kilometre pond from which cooling water is taken for the plant.

Reactor Units 1 through 4 were launched in 1976, 1979, 1983, and 1985, respectively. New reactors are being built at the site, but despite the design-basis expiration dates that have come and gone for the first and second reactors – the 30 years of engineered operational lifetime ran out for these reactors in 2006 and 2009, respectively – the units were not decommissioned accordingly and continue operation.

Another set of troubling issues associated with the operation of these reactors is that spent nuclear fuel generated in RBMKs is not subject to reprocessing and keeps accumulating in storage. Over 10,000 tonnes of this highly toxic nuclear waste has been amassed in Russia from RBMK reactors alone.

Reactor maintenance and a possible radiation release aside – assuming that the alarm alerting of elevated radiation levels at the site was in fact caused by a faulty detection system – a disruption in a nuclear power plant’s operation is bound to harm the energy system first and foremost: Without a warning, the grid in Central European Russia experienced a loss of 1 gigawatt’s worth of electricity.

According to Rosenergoatom, Kursk NPP is an important part of the United Energy System of Russia. Its key consumer is the Central Energy System, which supplies electricity to 19 regions of Russia’s Central Federal District, and Kursk NPP produces 52 percent of the total output of all electric power plants of the Chernozemye – or Black Earth Belt – region (“without Kursk NPP, the region would hardly develop,” Rosenergoatom says), including covering 90 percent of the energy needs of Kursk regional industry and exporting electricity to nearby Ukraine.

The outage of October 20, however, is not an isolated incident – the previous emergency shutdown took place at Kursk NPP on July 22, 2010 – and on the whole, reactor scrams or cases when reactors are taken off the grid are not uncommon at Russian NPPs. 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 the energy system, this spells additional costs: Spending on new high-voltage lines to carry output, maintaining so-called “cold” and “hot” reserve capacities, kept on standby in case they are needed to pick up the extra load, building pumped storage plants…

According to Rosenergoatom, in September 2010, Kursk NPP produced 2,171.4 million kilowatt-hours of electricity. If all of its four reactors worked non-stop, the energy system would have received 2,880 million kilowatt-hours, or almost a third over what it did receive.

A déjà-vu all over again

The new incident at Kursk resembles strongly the events of late last July at the same site – a scram followed by a lack of clear information about what had in fact happened at the plant. On July 22, Reactor No. 1 of Kursk NPP was shut down by the emergency protection system and was under repairs for over a month before it was taken back online. Information that elevated radiation levels were picked up by detectors surfaced after the incident, but the authorities denied all such reports.

On August 4, Greenpeace Russia made an attempt to get to the bottom of the accidental radiation discharge reports in a letter it addressed to Russian Prosecutor General Yury Chaika: “According to information made available to us, an increase in background radiation levels was picked up by background radiation sensors at the moment the scram was initiated. Our information says one of the control channels of Reactor 1 was destroyed, accompanied with damage occurring to the graphite stack. The likelihood is very high that this could have led to an accidental discharge of some of the radioactive water and a release of radiation beyond the plant’s premises.”

Greenpeace urged the Prosecutor’s office to look into the matter and verify – or disprove – the authorities’ assurances that no consequences implying a release of radiation had taken place during the event.

The only response Greenpeace has so far received was of October 21 – and rather than from Prosecutor General’s office, it came from regional prosecutors in Kurchatov, Kursk NPP’s hometown. A two-paragraph letter, written in a mangled, seemingly hurried Russian and signed by a deputy regional prosecutor, informed Greenpeace that its request for information had been received and processed.

“It has been established that on July 22, 2010, at 00:23 a.m.,” the letter said, “Reactor Unit No. 1 of Kursk NPP was shut down by the emergency protection system. Radiation monitoring sensors were activated, but values of radiological parameters at reference points were lower than the established reference levels. No violations of limits and conditions of safe operation as per radiation safety parameters have been registered.”

The last phrase mirrors, almost word for word, the standard statement accompanying all Rosenergoatom reports on various incidents at its sites.

Given the tortured spelling and punctuation of the prosecutors’ response (in its Russian original; to view, please follow the link on the right), it is hard to interpret the missive as anything but a standard run-around. It is likely that in the two months that have passed since the incident, the prosecutors did not trouble themselves much with finding out the truth.  It is just as likely they had attempted no investigation to begin with – and, as evidenced by the last sentence in their response, simply cut-and-pasted the safety assurances from a Rosenergoatom press release.

Kurchatov is a small place. It would stand to reason that in the face of an offensive mounted by some tree-huggers from Moscow, prosecutors would close ranks to defend their fellow townspeople, the nuclear workers.

But questions do linger. However incompetent their reply, the prosecutors confirmed that the radiation detectors had alerted the staff to elevated radiation levels at the site. But what about those reference points? And what about elsewhere on the premises? If not at those points, where was the radiation discharge picked up? And what were the factual levels shown by the sensors? How much radiation was in fact released this time, if any?

“We are not satisfied with the answer,” Vladimir Chuprov, who heads Greenpeace Russia’s energy unit, told Bellona Web. “Prosecutors should take a more serious approach toward looking into reports of a potential cover-up involving discharges of radionuclides into the surrounding environment.”

Chuprov suspects the letter’s author may have indeed chosen to attempt no investigation and simply copied the nuclear authorities’ information into his response to Greenpeace.

“His answer contains no data whatsoever – how can one talk about background radiation levels without citing any specific radiation dose values? It is possible that no investigation has been carried out at all, and such an approach may create a sense of impunity for the nuclear workers. This will take us on a direct route to a new Chernobyl,” Chuprov said.