AP/Wideworld

Lack of containment was Chernobyl Unit 4 powerplant’s fatal flaw when it exploded in 1986.

After 21 years of precarious service, the “sarcophagus” hurriedly erected by Soviet engineers around Chernobyl’s exploded reactor in Ukraine has undergone a major structural upgrade. Now, at least four years must pass before a final containment is completed to enclose the intensely contaminated facility.for a century, following the for a century, following the construction contract’s scheduled signing on Sept. 17.

The Novarka project consortium will immediately start detailed design and site preparation for a steelwork vault 150 meters long x 257 m wide x 105 m tall, costing over $500 million. To minimize workers’ radiation exposure, the estimated 20,000-tonne, double-skin vault will be built away from the reactor, then fitted out and slid over the sarcophagus, says a Novarka engineer.

State-owned plant operator ChNPP was empowered to sign the much-delayed contract following this July’s agreement by about 30 donor governments to release $450 million to start work.

Related Links: At Chernobyl, French Contractor Nears the Start-Finish Line, Sept. 14, 2007 Contract To Cap Damaged Chernobyl Nuclear Plant Delayed, April 10, 2006 U.S. Company To Build in Ukraine, Jan. 16, 2006 Steel Vault Over Chernobyl's Unit 4 Will Cost $250 Million, July 28, 2003

Donors, including the U.S., had awaited the outcome of an unsuccessful challenge last year to the contract’s award by the runner-up, says Axel Reiserer, spokesman for the European Bank for Reconstruction and Development, the fund’s manager . Novarka’s price, lodged two years ago, was 25% lower than a consortium led by CH2M-Hill, Englewood, Colo.

Headed by Paris-based Vinci Group, Novarka includes France’s Bouygues S.A. and Nukem Ltd., U.K., plus local contractors. Germany-based Hochtief has withdrawn from Novarka since the initial award.

Chernobyl’s new vault is the largest element in a $1.39-billion multipronged Shelter Implementation Plan (SIP), agreed upon internationally 10 years ago. SIP included a $50-million project, completed last year, to stabilize the sarcophagus, which went up within months of the April 1986 disaster.

In the chaos following the reactor’s explosion, teams risked their lives installing 400,000 cu m of concrete and 7,000 tonnes of steelwork. They repaired the north side with a massive, stepped wall, propped the west side with 50-m-high buttresses and built a steel-plate roof supported by 27 1.2-m-diameter tubes. Built under extreme conditions with a 30-year design life, the sarcophagus contained inherent flaws and was soon deemed vulnerable to collapse.

EBRD

EBRD

Nuclear plant’s shelter will be built away from site and rolled into place.

In the current stabilization work, the consortium, led by Russia’s JSC Atomstroyexport, fielded some 2,500 workers during 18 months to cut radiation-exposure times. So far, 138 contracts have been signed for Chernobyl valued at nearly $490 million, with 86 completed.

Among other Chernobyl projects is the stalled construction of interim storage for some 22,000 fuel assemblies from shut-down reactor units one, two and three. Work stopped early this year when ChNPP and a consortium led by Paris based Areva NP failed to agree on nuclear processing specifications and terminated their contract, signed in 1999.

With Areva’s 232 concrete storage modules and processing building in place, ChNPP on Sept. 17 was scheduled to sign a nuclear-component turnkey contract to finish the fuel facility with Holtec International, Marlton, N.J. Holtec values the five-year contract at about $275 million.