KIEV, Sept. 17 - French nuclear engineering concern Novarka will build a $505 million state-of-the-art cover around the damaged nuclear reactor of Chernobyl Nuclear Power Plant, according to a contract signed Monday.

The construction of the cover, or confinement, is financed by the G-7 through the European Bank for Reconstruction and Development and is to be completed within the next five years.

The construction will cover the damaged reactor No. 4 at Chernobyl, the site of the world’s worst nuclear civilian accident in 1986, in order to ensure its safety for the next 100 years.

“Its main task is to ensure safety for at least 100 years,” Oleksandr Chaliy, deputy chief of staff of President Viktor Yushchenko, said at a press conference.

The construction of the confinement has been planned for more than a decade, with the G-7 most industrialized nations raising money following Ukraine’s pledge permanently to shut down the Chernobyl Nuclear Power Plant. Ukraine shut Chernobyl, which had produced up to 5% of the country’s power, in December 2000.

The new 105-meter-tall construction, made of steel and other materials, will have a shape of a semi-sphere that will cover the existing sarcophagus, hastily built from concrete several months after the nuclear accident in April 1986. The construction will weigh about 20,000 metric tons.

“This event is of planetary importance,” Yushchenko said after the contract was signed between Novarka and Chernobyl.

Ukraine has been seeking to build the new cover amid concerns that the existing sarcophagus may one day become unstable and even collapse, sending radioactive clouds to the atmosphere.

Ukrainian companies have been working over the past several years to reinforce the existing sarcophagus to extend its lifespan until the new cover is completed.

Ihor Hramotkin, the general director of Chernobyl, said the recent improvements will ensure its safe operation during the next 15 years. Once the new cover is finished, the existing sarcophagus will be dismantled, he said.

Holtec International of the U.S. will build a $200 million dry spent nuclear fuel storage facility at the site of the Chernobyl Nuclear Power Plant to accommodate the nuclear waste currently buried under the sarcophagus.

Chernobyl and Holtec signed the contract on Monday.

The facility is supposed to be erected and completed within the next 52 months, according to Hramotkin.

The storage facility will be used after the existing sarcophagus is dismantled, allowing access to the massive amount of spent nuclear fuel that is buried beneath.

The facility is needed to prevent the shipment of the spent nuclear fuel across Ukraine to Russia, which is currently accepting the spent fuel from its operating nuclear power plants.

Holtec was earlier awarded a contact to build a major spent nuclear fuel storage facility in Ukraine to would accept the waste from three Ukrainian nuclear power plants. The facility is supposed to be ready by the end of 2009. (cp/ez)