April NPP chronicle – RBMK units hiccup in Russia, a bird shuts down a reactor in Ukraine

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A three-day outage at Kursk NPP

Just as the 25th anniversary of the 1986 tragedy at Ukraine’s Chernobyl was approaching, Reactor Unit 4 at Kursk NPP – which is located in Kursk Region, in Central European Russia, and runs RBMK-1000 reactors, of the same design that exploded at Chernobyl – was shut down by the automatic protection system. According to a statement by the Russian State Nuclear Corporation Rosatom’s Crisis Management Centre, “on April 25, 2011, at 08:49 a.m., the unit, while operating at a capacity of 1,035 megawatts, was shut down by the automatic protection system actuated following a false emergency alarm.” A statement to the same effect also appeared on the website of the Russian NPP operating organisation, Concern Rosenergoatom, complete with a standard assurance that “no violations of the limits [or] terms of safe operation of Kursk NPP power units were detected. The radiation background at the NPP and on the nearby territory is unchanged.” 

Reactor Unit 4 had been commissioned in 1985; its useful service life expires in 2015. The outage at Kursk lasted for three days, from 08:49 a.m. of April 25 to 09:10 a.m. of April 28. During this time, around 72 million kilowatt-hours of power was undersupplied to the grid.

Operating load reduced at Leningrad NPP

Just like Kursk NPP (as well as Smolensk NPP), the Leningrad station – which is located in Sosnovy Bor, near St. Petersburg – runs RBMK-1000 reactors. According to Rosatom’s Crisis Management Centre, “on April 27, 2011, at 19:42 p.m., as the unit was operating at a capacity of 1,026 megawatts, a 2PEN-2 feedwater electric pump shut down. A 20-percent reduction in operating load was performed manually at the unit in accordance with the design-basis operation algorithm. At 20:05 p.m. of April 27, 2011, a reserve 2PEN-5 pump was engaged. At 00:30 a.m. of April 28, 2011, load was restored to 1,020 megawatts.”

No information about this incident was posted on Rosenergoatom’s website.

The unit was operating at reduced capacity for almost five hours. The grid lost around 1 million kilowatt-hours in undersupplied electricity.

According to Rashid Alimov, a St. Petersburg-based environmentalist and co-chairman of the ecological group Ecoperestroika, incidents like this are not uncommon and testify to a lack of due control on the part of the Russian Federal Service for Ecological, Technological, and Atomic Supervision, Rostekhnadzor, which is Russia’s federal industrial safety oversight authority.

“The old and dangerous reactors of Leningrad NPP are not reliable. Their useful service lives have been extended unlawfully, without proper state environmental impact evaluations. This latest incident is a consequence of Rostekhnadzor’s indulgence toward the atomic industry,” Alimov told Bellona.

Birds as a nuclear event risk factor

The incident that occurred at Ukraine’s Rovno (Rivne) NPP on April 5 is more of an anecdotal variety, though there is hardly any amusement to be found in it.

Ukraine, another former Soviet state, has four nuclear power plants (not counting Chernobyl). All were built either during the time that Ukraine was part of the Soviet Union or by Russia after the USSR disintegrated. Ukraine is heavily dependent on nuclear power, which accounts for almost half of all energy produced in the country.

A statement with preliminary information about the incident at Rovno has been published on the Ukrainian page of the website of the State Nuclear Regulatory Inspectorate of Ukraine. The event, registered at 12:17 p.m. of April 5, 2011, was caused by the differential bus protection engaged following a malfunction at the busbar, which tripped generator circuit-breakers and a number of other electrical devices at the plant’s Unit 2 – a VVER-440 reactor of Russian make – and led to its emergency shutdown.

Traces of soot were detected at the place where the malfunction occurred. An electric arc was also reported by witnesses. A ground fault is named as a possible underlying cause of the incident, likely brought on… by a foreign object dropped by a bird.

In other words, a bird – something that one would hardly think a candidate for risk assessment in an industry that has to take immense safety precautions against earthquakes, plane crashes, terrorist threats, or operational errors, among other major risk factors – can essentially take a nuclear power plant out of operation.

It took the unit a week to restore operating capacity after the scram.

“The incident at [Rovno NPP] with a foreign object that led to the actuation of the emergency protection system and a reactor shutdown is another testimony to the fact that it is impossible to predict all potential external impacts that can affect a reactor’s equipment. Therefore, absolute safety is impossible for an NPP, even theoretically,” Artur Denisenko, energy programmes coordinator at the National Ecological Centre of Ukraine, told Bellona. “It is also symbolic that power supply [was at the time] discontinued from the two oldest reactors [in Ukraine], Reactor Units 1 and 2 of Rovno NPP, on which enormous funds were spent to extend their operational lifetimes. If old nuclear power reactors cannot be protected from foreign objects brought by birds, these reactors must be taken out of operation.”

Someone flew over Kursk NPP

Back in Russia, a violation of air passage regulations was registered in the area of Kursk NPP on April 27. Rosatom’s Crisis Management Centre reports this incident with an unsanctioned passage of a plane over the nuclear power plant’s premises:  “On April 27, 2011, at 12:40 p.m., a flyover of a twin-engine plane was registered over the NPP’s territory, which is closed for aircraft passage. An inquiry into the incident showed that the plane had been performing a planned flight, approved in an established order, and was carrying a foreign delegation on board. While in flight, the plane deviated from its course and flew over the NPP’s territory. An investigation is under way.”

RBMK-running nuclear power plants in Russia are old stations. A number of alterations were made to the design after the Chernobyl tragedy, but these reactors still operate without containment vessels, which are among the main protection features of newer reactor models. But newer stations or those under construction, however, are not adequately protected against a plane crash either. And planes do fly over nuclear power plants in Russia – military and test aircraft, as well as passenger jets. That a plane crashing onto one of Kursk’s reactor buildings or an on-site spent nuclear fuel cooling pool would have caused major nuclear and radiation safety consequences is, alas, without doubt.

Andrey Ozharovsky

idc.moscow@gmail.com

Maria Kaminskaya