The only operating reactor at Zheleznogorsk Mining and Chemical Combine in Siberia has been out of operation for one week, local daily Segodnashnaya reports. On February 20th, personnel at the reactor central post registered water consumption fall in one of the reactor fuel assemblies. After the water level had reached the critical level, the reactor was stopped.

Similar incident took place at the combine in 1985. At that time five fuel assemblies had to be reloaded, now only one assembly is damaged. The personnel thought the repair works would take a couple of days, but they have been going on for one week since the problem was revealed. The reason of the incident is fuel assembly enlargement. It is extremely rare situation, but sometimes it occurs, plant’s officials said.

The deformation of nuclear fuel assemblies stops normal circulation of the cooling water, therefore the reactor has to be shut down and the damaged assembly reloaded. Otherwise the fuel can melt down.

This time, the combine officials claim the fuel was not melted. The mining combine press centre stated that the event can hardly be called an accident. Even inside the facility radiation levels remained normal.

Zheleznogorsk, also known as “the Iron City”, is situated approximately 50km north of Krasnoyarsk on the eastern side of the River Yenisey in Krasnoyarsk county, Siberia. The city has a population of 90,000 and was known by its code name Krasnoyarsk-26 until 1994. The Mining and Chemical Combine with its three plutonium producing reactors and a radiochemical plant are well shielded 250m to 300m underground. The first reactor was shut down on June 30th 1992, and the second followed on September 29th the same year and the third (AD-2) has been in operation since 1964.

The remaining reactor supplies the facility and residential areas of Zheleznogorsk with electricity and heat. The reactor is one of the three plutonium producing reactors still in operation in Russia. The other two are located in Seversk (former Tomsk-7). The Russian-American intergovernmental program aimed at refitting the reactors to stop plutonium production or their replacement with alternative energy sources has failed so far.

Last year the combine general director stated that the reactor’s operational life time could be prolonged for a period of not less than 10 years. Yury Vishnevsky, head of the Russian Nuclear Regulatory Agency, expressed his disagreement with this point of view. He said that all three reactors exceeded the limits of operation two times and should be taken out of service.