April 1986 saw the world’s worst nuclear disaster as an explosion at the Chernobyl nuclear power plant allowed radiation to spread over large parts of the continent, causing extensive pollution and long lasting ecological damage. Following the explosion, the reactor was encased in concrete to prevent the further spread of radioactive dust, but poor design and the passage of time have both seen the original cocoon deteriorate, meaning there is once again a heightened risk of radioactive leakage.
Against this background, the Ukrainian government invited tenders for a new solution to prevent future radiation leakage as early as 1992, but it took a further 15 years before the design was agreed and the contract awarded to Novarka, a joint venture between Vinci Grand Projects and Bouygues Travaux Publics. Steel for the new structure is being fabricated in Italy by Cimolai with 750,000 Greenkote Tension Control Bolts needed to hold the structure together being installed by steel erection teams from all over Europe.
Greenkote has licensed its coating process to Tension Control Bolts, a designer, manufacturer and worldwide distributor of the most efficient high strength friction grip and pre-loaded bolting system. TCBs, as they are commonly known, are replacing conventional high strength friction grip bolts and swaged collar rivets simply because they are quick and easy to install and offer guaranteed tension which, together with visual inspection, removes the likelihood of operator error and ensures that connections are tightened in accordance with specifications. Nowhere is this more important than in the construction of the new safe confinement shelter (NSC), where speed of assembly is also an important factor, to minimise workers’ exposure to radiation dangers.
Greenkote’s coating system offered NSC designers important advantages, as it removes the risk of hydrogen embrittlement in bolts, is harder wearing than galvanising, offers excellent corrosion protection and readily accepts all paint systems.
Tim Stokes, managing director of Tension Control Bolts commented: “Our ability to offer the combination of a fast and effective pre-loaded assembly system with bolts protected by Greenkote was a significant factor in determining the decision to use our product. Moreover, we are able to give a 150 years life time guarantee.”
Mark Gore, CEO of Greenkote added: “Greenkote’s thermal diffusion process offers exceptional corrosion protection and longer wear and it outperforms many other traditional coating processes such as zinc plating, hot dip, metal flake and sherardizing as well as PVD and CVD. The Chernobyl project is a high point for us, as there can be few other applications where a high performance coating and protection system is so important when it comes to guaranteeing the structural integrity of a design.”
Protecting the local and wider population from further radiation leaks is a top priority for the Ukrainian government, with the impact of the 1986 accident still being felt today amongst the local population. Large tracts of land are still heavily polluted and remain dangerous, following the accident.
Now, however, with the new shelter nearing completion, designers are expecting the structure to last for at least 100 years, by when it is hoped the technology of cleaning up after a nuclear disaster will have advanced significantly.
