Chernobyl’s arch: the world’s biggest moveable structure
In the early hours of April 26th 1986, a planned test of reactor 4 at Russia’s Chernobyl nuclear plant led to what the United Nations have termed “the greatest environmental catastrophe in the history of humanity”. Now thirty years on, one of the biggest engineering projects in history, designed to slash the risk of another major release of radioactivity, is nearing completion.
The 25,000 tonne protective steel arch (or sarcophagus) is an engineering project of staggering porportions. At 108m tall and 257m wide, the structure is capable of housing the Statue of Liberty, the Stade de France or the footprint of the Eiffel Tower. It also comes with a hefty price tag estimated to be €2.15bn (a substantial increase from the €800m originally estimated), a cost which is being met by more than 40 governments throughout the world.
The arch will replace the current sarcophagus, a metal and concrete structure which was constructed in the months following the disaster in 1986 by emergency workers, who did so at great risk to their own health. This structure is now rusting and in danger of collapse.
As a project of this nature has never been undertaken, every stage of the project has been a step into the unknown. Even before construction of the arch could begin in 2010 the construction site had to be made safe and cleared of hundreds of tons of radioactive topsoil and laid with 8m deep concrete foundations. The reactor building itself is too radioactive for people to work assembling the arch above it – incredibly, approximately 97% of the reactors contents, about 200 tonnes of uranium, still remains inside. Instead the arch is being constructed a few hundred metres aware, at a safer distance from the reactors dangerous levels of radiation.
Measures have been taken to make the area under the arch safe enough for people to work unprotected. However, just a couple of hundred metres away full protective clothing must be worn. All staff working on the arch have an annual allowance of radiation exposure and are continually monitored. Three ways of reaching the annual dose limit would be to spend:
- 50,000 hours at the on-site office
- 2,000 hours in control room unit 4
- 12 minutes above the arch roof
When construction is completed towards the end of next year, the new arch will be pushed over the top of the old structure using a system of specially made tracks, covering the reactor and sealing it from releasing further radioactive particles. Giant cranes inside the arch will then lift out the remains of the reactor and what remains of the fuel.
Sadly, the clear up of Chernobyl doesn’t end there. The Ukrainian government estimate the site will not be completely cleared until 2065 and radioactive particles will remain in the environment for hundreds of generations to come.
Key facts
- 250,000 – people moved to safety
- 30km exclusion zone surrounds the reactor
- 200,000 sq km contaminated with radiation
- 4000 – estimated number of deaths (United Nations)
- 93,000 – estimated number of deaths (Greenpeace)
- 2000 the date Chernobyl plant closed down
Note: The Chernobyl Arc is being constructed by Novarka, a 50/50 joint venture by Vinci Construction and Bouygues Travaux Publics. You can find out more about the project by visiting www.novarka.com
