"There are enough serious questions regarding the safety of the sea transport of vitrified high level waste to justify a postponement of the first shipment, pending the results of further investigation," warned Dr. Edwin S. Lyman, a physicist who conducted the study at Princeton University's Center for Energy and Environmental Studies. The dangers, Lyman found, arise from normal conditions of storage and transport of the waste as well as from extreme conditions that could develop during a severe shipping accident.
"Vitrified high level waste" refers to highly radioactive liquid residues that are condensed, solidified into glass logs and contained in stainless steel canisters for purposes of storage, shipment and final disposal. Radioactive decay of the waste generates enormous amounts of heat, causing the glass logs under normal conditions to be as hot as 510 degrees Centigrade (950 degrees Fahrenheit)---well in excess of the melting point of lead. Thousands of the glass logs, each weighing about a half-ton, are to be shipped to Japan over the next two decades from France and Great Britain, where the wastes are produced in reprocessing plants that extract plutonium from the radioactive spent fuel of Japanese nuclear reactors.
Dr. Lyman made the following principal findings:
-- "The level of safety provided by current international standards governing the sea transport of vitrified high-level waste is highly uncertain."
-- "The maximum allowable storage and transport temperatures are too high and appear to compromise safety."
-- "The procedure for determining the maximum allowable [radioactive] leak rate [from shipping casks] is obscure."
On the basis of these findings, Dr. Lyman called for an independent review of the nuclear- waste storage and transport system before the shipments are allowed to begin. Such a review, he said, should be undertaken "by the competent authority of one of the potentially affected nations along the route of the shipments---a category which includes the United States. To facilitate this process, industry must provide considerably more information than is presently available."
The 72-page report was released by three public-interest organizations---Greenpeace International, based in the Netherlands, the Nuclear Control Institute in Washington D.C., and the Citizens' Nuclear Information Center in Tokyo. They commissioned the report after France, Japan, the U.S. and the European Union had failed to act on their request, made with the World 1 Information Service on Energy in Paris (WISE/Paris), for a full safety analysis and environmental impact statement prior to the start-up of the waste shipments. The U.S. government also has not been responsive in meeting requests by Representative Neil Abercrombie (D-Hawaii) and all other Pacific and Caribbean members of the U.S. House of Representatives for further study of safety and security issues.
"The Lyman Report makes clear that it would be irresponsible for Japan and France to proceed with the radioactive waste shipment without first performing the full safety and environmental analysis we have demanded," a spokesman for the three organizations said.
In 1992, an international uproar greeted Japan's plan to transport one and a half tons of weapons-usable plutonium from France for use in its civilian nuclear power industry. A freighter and lightly armed escort vessel finally proceeded despite concerns about the adequacy of security and safety arrangements and about the stockpiling of surplus plutonium in Japan. The shipment took a circuitous route around the tip of Africa that avoided the territorial waters of most of the 45 nations that expressed concerns about the shipment. Now Japan is expected to follow a more direct and heavily populated route for its inaugural shipment of radioactive glass logs---one that will go through the Caribbean Sea and the Panama Canal and pass near Hawaii.
Dr. Lyman's report warns that exposure of the radioactive cargo to a prolonged hot fire could lead to a breach of all three containment barriers---the glass matrix itself, the stainless steel canister surrounding it, and the outer shipping cask---resulting in the release of highly toxic radioactive material. In such an accident, radioactive release rates of cesium alone could be hundreds of times greater than international limits for accident conditions, Dr. Lyman found. "If molten glass were to flow out of a breach in the canister, much greater releases would be possible," he reported.
"If releases of [this] magnitude occurred near a populated area, they could prove to be extremely hazardous to nearby communities," according to his report. "This would be the case either if an accident took place in a harbor or close to shore, or if the ship made an emergency port call following an accident."
Radioactive cesium, which is contained in the glass logs, was one of the principal contributors to the widespread contamination caused by the Chernobyl accident. The average shipment "will include many times the quantity of cesium estimated to have been released by Chernobyl," according to Dr. Lyman. He noted that radioactive cesium gives off deep-penetration gamma rays, can irradiate humans externally and internally, emit radiation from the ground for many years, and enter the food chain. Emergency measures are difficult and costly, especially for countries lacking technical and financial means.
He found that in the event of an extremely severe accident, such as a collision with an oil tanker in which a cargo hold is broken open and the casks exposed to an 1,100 degree Centigrade (2,000 degree Fahrenheit) fire typical of such accidents, exposure to the heat could cause failure of the outer cask seal, rupture of the inner steel canister and substantial release of radioactive gases from the glass in less than a day. The Department of Energy, in a report prepared during the Bush Administration, has claimed that such a sustained, below-deck fire is not credible. "If the industry believes such scenarios to be incredible," Lyman asserted, "it should provide at least computer demonstrations to that effect. Until this is carried out, DOE's assertions remain in the realm of speculation."
DOE, which had prepared the report pursuant to a law sponsored by Abercrombie, agreed recently to a request by Abercrombie and his colleagues to further explore accident possibilities and consequences---only to reverse course and cancel the project after objections were raised by other Federal agencies and representatives of Japan.
Dr. Lyman also found that the very high temperatures encountered during normal storage and transport could actually increase the probability that all three barriers would be breached during a severe accident, leading to significant releases.
First, the intense, internal heat given off by the radioactive glass logs presents a problem since, at the permitted level of 510 degrees C, there is only a "narrow safety margin" of less than 100 degrees C below the level at which the glass starts 2 to become unstable. Above 610 C, but still well below the melting point of 1,150 degrees C, the glass begins to become prone to physical changes ("devitrification") and give off radioactive materials, especially cesium gas, the report warns.
Second, even at 500 degrees C the glass may activate mechanisms that can cause the integrity of the stainless steel canisters surrounding the glass to deteriorate--- including a process known as "sensitization," according to Dr. Lyman. This condition causes rapid deterioration of the corrosion-resistance of the steel and also reduces the resistance of the steel to fracturing upon impact, even in the absence of corrosion, Dr. Lyman found. "In corrosive environments, sensitized metals experience severe loss of strength and ultimately can literally fall apart," he reported.
In the event of a rapid increase in temperature from a fire during a severe accident, the expanding glass could cause the weakened canister to rupture, releasing deadly cesium vapor and other radioactive particles. Shipboard fires typically burn for one-day's duration at a flame temperature of 1,100 degrees C, he noted. The canister could be further weakened by the thermal shock of cold water used to quench a fire. The steel canisters also would be subject to rapid corrosion by salt water if a waste shipment were lost at sea, he found.
To avoid hot glass weakening the steel canisters, he suggests the vitrified high-level waste may have to be cooled for longer periods before transport; the concentration of wastes put into the glass may have to be reduced; or the casks may have to be loaded to less than full capacity. He also recommends immediately undertaking a program to determine if deterioration already has occurred in canisters during storage because of the corrosive effects of the radioactive glass. If so, then an alloy would have to be found that is less susceptible to such corrosion.
Third, during a fire, the ability of the outer shipping cask to contain the radioactive vapors and particles rapidly building up inside could be compromised. An O-ring seal similar to the type that contributed to the space shuttle Challenger disaster is used to prevent leakage of radioactive gases and particles from the lid of the shipping cask. "These O-rings are the most vulnerable sites on the cask," the report points out, because they are prone to damage in high radiation fields and prone to failure at temperatures above 230 degrees C. Normal operating conditions can subject the seals to temperatures of 150-200 degrees C, providing a safety margin of less than 100 degrees below the maximum allowable seal temperature.
Dr. Lyman recommended that the casks be subject to a test beyond the required 30-minute fire at 800 degrees C, in order to determine the duration and heat of a fire that would likely cause seal failure. Casks designed to transport German high-level waste use more expensive metal seals, he notes, which are more resistant to radiation and can operate at both higher and lower temperatures than the rubber-like elastomeric seals used on casks for Japanese waste.
In September, the three sponsors of Lyman's report, along with WISE/Paris, had called on France, Japan, the U.S. and the European Commission to provide such information by conducting an immediate evaluation and full disclosure of the dangers to en-route countries and the marine environment posed by the shipment of radioactive nuclear waste. In an open letter to the governments, they demanded all technical data on the radioactive waste and on tests performed to ensure that the shipping containers will not leak or rupture in the event of a severe accident. They also asked for details about the ship's route and emergency planning with nations along the route. When it became clear that no such information would be forthcoming, the three organizations commissioned Lyman's report.
The first sea shipment is to consist of a single, 112 metric ton cask
containing 28 glass logs of high-level nuclear waste in steel canisters. Eventually, 3,200
canisters will be
returned to Japan in 15 to 30 sea shipments over a 15-to-20-year period---an
average of six to
seven casks per shipment. "The total amount of long-lived radioactive material
(with a half-
life exceeding 10 years) in each cask [is] quite large," the report notes,
consisting of 11 to
15 million curies of radioactivity---about three to four times the amount
released by long-lived
radionuclides in the Chernobyl accident.
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