Two workers were exposed to high doses of radiation at Siberian Chemical Combine reactor no. 4 (AD-4), Tomsk County, on 14 June. The building where the reactor is located was contaminated. The incident ranked 2 at the INES (International Nuclear Events Scale), where 7 is a sever accident.

The workers were tasked to load a fuel element inside the reactor, but miscalculated and opened the lid of a channel with fuel inside. Radioactive gases gushed out, contaminating the reactor construction. One of the workers received 150-160 mSv, while another one was exposed to 70-80 mSv (the maximum permitted annual dose is 50 mSv). They were rushed to the hospital, but were sent home later as their condition was said to be normal. Officials say no radiation escaped into the environment. The two reactors were reportedly being shut down at the time of the incident for routine maintenance and fuel change. The Russian Ministry for Atomic Energy (Minatom) sent a commission to Tomsk to investigate the incident on site. The Russian State Nuclear Regulatory Authority (GAN) will join the commission.

The two reactors, which remain in operation at Siberian Chemical Combine (AD-4 and AD-5), started in 1965 and 1967, respectively. The reactors are located at "Object-45", not far from the radiochemical plant. These graphite-moderated reactors were designed to produce weapons grade plutonium. In compliance with the agreement singed by then Russian Prime-Minister Victor Chernomyrdin and U.S. Vice President Al Gore in June 1994, the reactors were to be shut down by 2000. However, the project seems to be shelved, as Russia says the reactors are the major source of heat and electricity for the neighbouring cities and substitutes have to be built first. Another option, worked out in co-operation with the U.S., was to convert the reactor cores in order to prevent plutonium production, but so far this project received no go as well. Recent reports suggest the reactors will operate beyond the year 2000.

Operate without certification
"We are worried about the condition of these two reactors," Nikolay Filonov, spokesman for GAN in Moscow, told Bellona Web. "They failed to obtain our licence, but still remain in operation," he added.

The Siberian Chemical Combine applied for a GAN licence last year, but they were turned down. GAN was not convinced the reactors would operate safely based on the application submitted. Nevertheless the reactors remained in service.

GAN says it will wait for the findings of the Minatom commission, which has been dispatched to the location of the incident. If the commission itself fails to shut the reactors down, GAN will submit the case to the General Prosecutor Office to force the Siberian Chemical Combine to comply with the law.

Minatom officials would not elaborate on the possible shutdown when reached by Bellona Web for comment today.

Definition of INES 2:

Incidents with significant failure in safety provisions but with sufficient defence in depth remaining to cope with additional failures. An event resulting in a dose to a worker exceeding a statutory annual dose limit and/or an event which leads to the presence of significant quantities of radioactivity in the installation in areas not expected by design and which require corrective action.