Unit 6 at Russia’s Novovoronezh NPP (also known as unit 1 of Novovornezh II) – the first AES-2006 series generation 3+ reactor – was taken off line on 10 November due to an electric generator failure, RIA Novosti reported on 17 November. The incident was not immediately reported by nuclear utility Rosenergoatom, which indicated that the reason for the emergency shutdown was a short circuit.

According to Rosenergoatom’s description of events, which appeared on November 16, the reactor went off the grid while tests were being conducted and all emergency systems functioned as expected. The site reported that the incident was a zero on the seven-point International Nuclear and Radiological Events Scale, zero being insignificant.

“Unit No 6 is in pilot operation and at this stage the reactor is going through a number of tests, and works in various operation modes with the goal of testing new equipment in all possible situations,” Vladimir Povarov, director of the Novovoronezh NPP said on the Rosenergoatom site. “The failure of specific elements of the equipment is not unusual,” he added. “Our task is the discovery and immediate elimination of all issues.”

The unit began producing energy in August and was brought up to full capacity only on 26 October as part of a field pilot operation. On 15 November, local online publication Bloknot Voronezh cited an anonymous witness who spoke about an explosion at plant’s turbine hall, and a burned out generator. An anonymous plant source was quoted by the site as saying the noise attributed to an explosion was actually steam pressure valves sharply snapping open. The source said the reactor scram was due to an electric generator failure, and that the reactor would return to testing as soon as the defects that led to the failure were eliminated.

Novovoronezh NPP set up an events committee to determine the cause of the failure and decide on the action to be taken. Two options were considered – repair of the on-site generator or replacement of the stator with a new one, previously supplied to Novovoronezh 7. The second option was chosen.

Novovoronezh 6 is the first of the VVER-1200 series to be completed, and the reference plant for other reactors of this type. Others are currently under construction or planned in Belarus. Finland, Turkey, Bangladesh, and Hungary.