CONTROVERSES NUCLEAIRES !
Bases de données Tchernobyl
Rénovation du sarcophage: suivi
Chernobyl "sarcophagus" to be renovated
ADIT, http://en.rian.ru, janvier 2008
MOSCOW
(RIA Novosti commentator Tatiana Sinitsyna) - The safety of the shelter facility at Chernobyl NPP covering the remains of the stricken nuclear reactor will now be greatly enhanced. The contract SIP 07-1-00 for this purpose was signed on January 10, 2008 at Chernobyl.
     Last year, the press prophesied an early caving in of the structure, but today these scare stories no longer carry any weight; specialists plan to do their best to strengthen the structure over the ruined reactor at least for the next 15 years.
     The SIP 07-1-00 contract envisages the repair of the roof over the shelter, installation of physical protection systems, and the reinforcement of supporting beams.
     The contract was signed by Chernobyl NPP as the customer and Stabilization Consortium, led by Russia's Atomstroyexport, as the contractor. The consortium also includes Ukraine's YUTEM-Engineering and Atomenergostroyproekt Institute.
     According to David Whitten, chairman of the evaluation panel of the Shelter Implementation Plan - Project Management Unit (SIP-PMU), the decision to award the contract was motivated by the authority of Atomstroyexport and its team's high level of professionalism.
     Mr. Whitten also pointed out that Atomstroyexport had always used modern and efficient management techniques, making it possible for the consortium to establish a standard of reliability and professionalism and a level of safety and quality.
     Throughout the world, the word Chernobyl now stands for a radioactive wound because of the one inflicted on the planet by a man-made accident at one of the Chernobyl generating units on April 26, 1986. Almost 22 years later, the wound is still not healed: some of its problems keep troubling specialists even today.
     What are these problems? "In order to understand why the shelter is unsafe, it is necessary to return to the days of May 1986 when a Soviet government commission decided that the destroyed unit had to be secured within the shortest period of time possible," said Prof. Alexander Borovoi, of the Kurchatov Institute, who has led research at Chernobyl for twenty years.
     "At that time the designers faced two options: build a giant sealed thick-walled shed to cover the unit completely, or use the unit's surviving structures to support beams carrying a roof of metal tubing and sheeting, and erect walls of steel and concrete."
     Expert estimates showed that the first option would have taken too long and cost too much money. Therefore, the second plan was chosen. Tens of thousands of highly-professional clean-up workers, risking their lives, built a gigantic sarcophagus in an extremely short period of time - only six months.		      But there are no engineering miracles. A gain in one respect, comes with a loss in another. The remote-control methods used due to the high radiation levels could not achieve the required tightness. The total area of cracks in the shelter reached almost a thousand square meters. Every year they let in up to 2,000 cubic meters of rain and melted snow.
     The moisture has steadily found its way into the structures and can spread radioactive material or in a worst-case scenario produce a runaway nuclear reaction.
     Radiation also prevented a reliable check on the actual strength of the structures chosen for support. All information was supplied by pictures taken from a helicopter.
     "The supporting props were a source of constant alarm: after all, they suffered from an explosion and a fire," Prof. Borovoi said. "Should one of them shift for some reason (say, in an earthquake), the domino effect could send the rest crumbling. The result would be what foreign experts call 'a collapse of the shelter': the structures would cave in and release radioactive dust into the environment."
     The Chernobyl structure has not been allowed to collapse. The threat was taken care of by the work carried out at the facility over the past three years (since December 2004). Builders used 750 tons of metal, 245 tons of reinforced steel and falsework, and 4,500 tons of reinforced concrete for the foundation to strengthen the shelter.
     The stabilization program included such measures as the strengthening of the eastern and western pillars of the Mamont beam, the reinforcement of floor panels and the connection of southern shields.
     Viktor Khavrus, head of the stabilization project, has stressed: "No one can call into question the unique and innovatory nature of the work done."
     The SIP 07-1-00 project, which was launched in January, will give the shelter a new lease on life. It will buy time for the next stage: the construction of a new confinement, or arc. That protective shelter must serve as a reliable sarcophagus for the ruins of the fourth reactor.
     The project moderator is the International Chernobyl Shelter Fund, which comprises 28 countries. The project is financed by the G8 and European Union countries. The European Bank for Reconstruction and Development has already accumulated $1 billion for the project.
     The unprecedented international project is called upon to eliminate all risks connected with the containment problem for at least a hundred years into the future.