At 20, Chernobyl sarcophagus fitted with set of new braces

As part of a project to strengthen its structures until a more permanent confinement can be built, the concrete-and-steel "sarcophagus" covering the destroyed Chernobyl-4 reactor has a new frame of gray and yellow metal braces over it.

November 30 is the 20th anniversary of the technical acceptance (licensing) of the sarcophagus, built under extreme conditions and designed to last 30 years. The Ukrainian Institute for Nuclear Power Plant Safety, however, considers it impossible to define a service life for the facility, which is formally known as the Shelter, since its structures included unstable supports with uncertain durability. A number of projects are under way to strengthen it within the international Shelter Implementation Plan (SIP), administered by the European Bank for Reconstruction & Development and funded by several countries and the European Commission.

According to Chernobyl station management, 90% of planned operations for strengthening the sarcophagus are already completed, thanks to activity within the last two years. The sarcophagus's western wall and other places are now coated with a web of metal braces, which Chernobyl experts said can retain all of the western wall even if it were separated from the rest of the structure.

On November 9, Igor Gramotkin, director general of Chernobyl, told a press conference at the Chernobyl site that the strengthening work will be completed next year. Vladimir Kashtanov, deputy director for Shelter issues, told Platts that at present, about 100 contract workers in addition to 80 plant staff work daily on the sarcophagus. Twelve people remain inside the sarcophagus around the clock. In 2005 there were sometimes as many as 500 people under the sarcophagus on a single day, Kashtanov said.

The reinforcement work will considerably reduce the risk of the sarcophagus's roof collapsing, an event that was calculated to result in a dose to staff 100 times higher than the annual 2-rem limit.

The next stage in the Shelter work is erection of a so-called New Safe Confinement. A French-led consortium called Novarka and a group led by CH2M Hill of the US are vying for the job. Plant manager Gramotkin in September declared invalid a preliminary decision awarding the work to Novarka and unilaterally cancelled the tender.

A western official said, however, that last month the Assembly of Donors backing the SIP had unanimously supported the EBRD's position that procurement should proceed on the basis of precontract discussions with Novarka. If they are successful, then Novarka will get the contract; if not, discussions will begin with the US-led consortium, he said. A bid by Ukraine for more influence in the EBRD's Project Management Unit, he said, is not central to the fate of the Novarka bid. Ukrainian representation in the PMU will be adjusted as the project proceeds, he said, provided enough qualified Ukrainian candidates can be hired.

At the press conference in Chernobyl, a representative of the PMU said the NSC tender, initiated in 2004, will be completed by the end of this year and the contract could be signed in February 2007. He said that "the winner will be chosen in accordance with all rules and procedures." But another source close to the EBRD said that schedule represents a best-case scenario, cautioning that until the negotiation process is completed there is no way to say when the contract could be awarded.

According to the PMU, 88 of the SIP projects worth $273 million have been completed, and contracts have been concluded worth $308 million. Planned operations for the sarcophagus account for another $426 million. Including construction of the new confinement, the estimated cost of SIP projects exceeds $1 billion.

Risks remain

Ukrainian experts said strengthening of the sarcophagus and erection of a new shelter do not remove the existing threats completely.

Alexander Kluchnikov, corresponding member of the Ukrainian Academy of Sciences and director of the academy's nuclear plant safety institute, told the press conference that the basic source of risk at Chernobyl was fuel-containing materials, i.e., remnants of nuclear fuel, sometimes mixed with other materials.

The institute's research has traced 150 metric tons uranium equivalent of fuel, out of 190.2 mt in the reactor before the explosion. It has so far been impossible to find the remaining 40 mt, he said. It is impossible to enter some areas under the sarcophagus because of obstacles or high radiation levels. Kluchnikov noted that collapse of structures, fuel being transformed into dust, and moisture ingress could still result in a "nuclear incident" or a small explosion if a chain reaction occurs.

That could happen, he said, if fuel materials migrated after collapse of structures. Radioactive dust -- about 30 mt of fuel has now been transformed into particulate size -- could gather in a single part of the plant, he added. In addition, studies showed that water leaches transuranic elements from fuel materials and collects under the reactor. About 3,000 mt of water gets into the sarcophagus annually. In recent years, concentration of uranium and transuranic elements in water under the reactor has constantly increased, especially in the sediment which collects there. Part of this contaminated water diffuses to the turbine room of unit 3, where it is cleaned. No diffusion into the geologic environment has yet been found, but data on the beginning of such a process have been collected, Kluchnikov said.

He said that in recent years, there has been a retreat from the original strategy accepted in the framework of the SIP and approved by Ukraine, and that technology development for extracting fuel-containing materials and testing of such technology were eliminated from the list of priority tasks. Kluchnikov said his institute is nonetheless developing technology for extracting fuel materials from the pressure suppression pool underneath the destroyed reactor.

Kluchnikov expressed fear that after erecting the new confinement, Ukraine will decide to resolve the fuel materials problem on its own, without any international help. He argued that extraction and safe storage of high-level nuclear waste are the main reasons for transforming the Shelter and that development of waste technology should take the precedence once the confinement is built.

Despite all the problems, Ukraine considers construction of the sarcophagus an important victory thanks to the heroism and feats of hundreds of thousands of "liquidators," or accident recovery workers. On November 10, Ukraine President Victor Yushchenko issued a decree establishing December 14 as an annual holiday called "Liquidators' Day."

On December 14, 1986, the Soviet government officially declared completion of the first step to eliminate the consequences of the Chernobyl disaster.

Created: November 27, 2006

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