London, 28 April 1999 (RFE/RL) -- International nuclear safety experts say they are worried about a mysterious increase of radioactive dust inside the protective shelter that covers Chornobyl's reactor number four, the unit where an explosion 13 years ago caused the world's worst civilian nuclear catastrophe.
The experts are apprehensive that if a fire ignites inside the sarcophagus, a huge cloud of the contaminated dust could be released into the air and spread radioactive fallout on a magnitude not seen since the Chornobyl disaster itself.
With evidence that part of Chornobyl's protective encasement also is crumbling, international experts are issuing an urgent call for emergency repairs to prevent another major nuclear disaster there.
Lars Larsson, the nuclear safety director for the European Bank for Reconstruction and Development, said the concerns were raised in Ukraine this month by an International Advisory Group that guides funding decisions for Chornobyl safety projects:
"For some reason, the quantity of this dust has been increasing. Whereas a couple of years ago, the estimate was that there was approximately one ton of the dust, the most recent report suggests that we now have between 30 and 40 tons of radioactive dust within the (existing) shelter. This structure is in very bad condition and the reason we are concerned is really what this structure contains."
Speaking at the EBRD's board meeting in London this month, Larsson said there is now "enormous time pressure" to reinforce the protective structure over reactor four at Chornobyl.
The hastily built concrete sarcophagus covers 160 tons of molten nuclear fuel -- a mixture of radioactive waste, concrete and graphite debris left over from the disaster in 1986. Like the growing amount of radioactive dust inside, Larsson described this deadly molten mixture as an "unknown substance" that has never before been dealt with by mankind. But he said it is known that tons of material inside the shelter are combustible.
In the bottom areas of the sarcophagus, there also are thousands of cubic meters of radioactive water. According to the latest studies, this water has not contaminated the ground water supply around Chornobyl. But Larsson warned that the consequences of any water leakage would be catastrophic for Ukraine.
The nearby Dnipro River supplies drinking water to 70 percent of the Ukrainian population as it flows from Chornobyl past Kyiv and on to the Black Sea.
Larsson said many of the problems with Chornobyl's existing shelter stem from the difficulty of building it quickly in an emergency situation during which workers were subjected to deadly radiation.
"It has been built in a typical Soviet 'super-human' style, engaging approximately 400,000 people -- experts, soldiers, workers. It was built without any design basis because (under the emergency situation of 1986) the design basis simply was not there. It (also) was built using remote technologies because the radiation was too high to really come close to the structure."
In the last 18 months, a 10-year repair project has been launched to make the giant sarcophagus safer and more stable. The project is being financed through the Chornobyl Shelter Fund. Although that fund is administered by the EBRD, it is not a commercial project and draws no money from the bank. The estimated $760 million for the repairs is to come in the form of grants. The largest contributors so far are the United States, the European Union and Ukraine. About 20 other countries also are contributing.
About $400 million already has been received by the Chornobyl Shelter Fund --enough for the planning phase and emergency repairs to get underway. The EBRD says there is enough money to keep the work going until the year 2001. By then, the bank hopes the rest of the financing will have been made available.
During the last year, broken support beams for the shelter's huge ventilation stack already have been repaired, and designers have drawn up plans for the critical task of reinforcing the roof of the sarcophagus.
The first of several enormous cranes has been erected at the site. Contracts also have been signed with 30 firms from Russia, Ukraine and western countries on engineering, licensing and managing the project.
But EBRD Vice President Joachim Jahnke says some steps still must be taken before major repair work can begin. He said contractors still need guarantees about the nuclear materials their workers will be exposed to while repairing the shelter. Insurance companies also must be found that are willing to underwrite the health risks to engineers and construction workers.
Meanwhile, the EBRD-administered Nuclear Safety Account has been extended for another three years in a move that clears the way for disbursing about $130 million in aid already committed for decommissioning other units at Chornobyl.
Neither Lithuania's Ignalina nuclear plant nor Bulgaria's Kozloduy power station will get additional money under the extension. The EBRD also says none of the funds will be used to extend the service of nuclear plants that are scheduled for closure.
Larsson said European officials still expect Ukraine to close Chornobyl entirely by the end of next year and to finish decommissioning the facility by the year 2002.
But the government in Kyiv has demanded loans to complete new reactors at Khmelnitsky and Rivne to replace electricity production lost by the closure of Chornobyl.
The EBRD has not yet decided whether to disburse any loans for Khmelnitsky and Rivne. Bank Vice President Charles Frank says the earliest that Kyiv could meet criteria to receive EBRD financing for those projects is mid-July. He said barter payments must be reduced for electricity usage in Ukraine, where only about two percent of electricity from nuclear plants is paid for in cash. The low ratio of cash payments raises concern about corruption in the energy sector, as well as doubts about Kyiv's ability to repay the loans.
The EBRD also is demanding what Frank called "real privatization" of energy distribution firms before approving loans for Khmelnitsky and Rivne.