Decommissioning at Chernobyl

26 April 2007

Ground preparation work is underway for the New Safe Confinement of Chernobyl 4, while dismantling progresses at unit 1, and defuelling at unit 3.

On 26 April, 21 years ago, Ukraine's Chernobyl plant suffered the worst nuclear accident in history when a power runaway event wrecked reactor 4, leading to a hydrogen explosion that destroyed the reactor building and exposed the core of the ruined reactor.

Work on constructing two more RBMK 1000 units at the site came to an immediate halt, but the three remaining reactors continued to operate for some years, unit 2 was shut down in 1991, unit 1 in 1996 and unit 3 in 2000. Their contribution to Ukraine's electicity supply was only recently replaced by the start-up of Khmelnitsky 2 and Rovno 4 in late 2004.

Several major projects are underway at the contaminated site. Most important is the work to isolate the dangerous remains of unit 4 from the environment. Toward that end, a $1 billion international project will see a New Safe Confinement constructed over the decaying Object Shelter erected in the disaster's immediate aftermath by Soviet authorities. Groundwork is underway to prepare for the construction of a massive arch structure which will cover unit 4's reactor building and its section of the shared turbine hall.

At the other units, more conventional decommissioning activities are in progress. The first batch of dismantled equipment from the turbine hall of unit 1 was sent to the Kompleks waste handling facility at the start of April, over 30 months after work began. Only outdoor equipment has been dismantled so far, this providing a relatively simple introduction to the decommissioning of contaminated plant equipment. In addition, preliminary work has been done towards dismantling the insides of the turbine hall.

Around 10 t of equipment from unit 1 is shipped off site each day, and at that rate, work could be complete by 2020-2.

Meanwhile, defuelling - the first stage in the decommissioning of a nuclear power plant - is taking place at unit 3. After nuclear fuel assemblies have been left to cool in the reactor core for a few years, they can much more easily be removed for storage and eventual recycling or disposal. At unit 3, nine of the reactor's 1000 assemblies are removed by rail each day for interim storage at the nearby INF SF-1 dry storage facility. However, the facility does not have sufficient space to hold all the fuel, and some must be kept in buffer pools until a second store is constructed.

Defuelling of units 1 and 3 began in December 2005. Unit 1 was defuelled by the end of November 2005 while unit three should be defuelled by late June this year.

Further information

WNA's Nuclear Power in Ukraine information paper
WNA's Chernobyl Accident information paper

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