June 14, 1996
STATUS REPORT ON PLUTONIUM AIR SHIPMENTS
The IAEA is revising its regulations for the transport of radioactive material. For the first time, its guidelines (Safety Series 6) will include separate criteria for an air-shipment cask. At present, the same criteria apply for all forms of transport --- road, rail, sea and air --- even though the IAEA has acknowledged the regulations offer less protection against air accidents than they do for surface transport.1 The IAEA relies on the shipping cask to prevent a radioactive release in an accident, rather than specifying different regulations for different types of transport. The new Safety Series 6 was expected to be issued in 1996. However, an extended review process may delay its publication until 1997.
Safety Series 6 is now under review by a new IAEA Advisory Commission on Safety Standards. If approved by the Commission, the revised Safety Series 6 will be sent to the IAEA Board of Governors for final approval in the fall. A technical advisory committee approved Safety Series 6 in September 1995 and forwarded it to the Board of Governors. However, the Board took no action and instead sent it to the new Commission for review.
At the September meeting in Vienna, a technical arm of the International Atomic Energy Agency approved a German proposal to weaken the new standard for air transport of plutonium- based nuclear fuel, despite opposition by the U.S. government and international civil aviation associations. The German delegation won agreement to exempt plutonium-uranium, "mixed-oxide" (MOX) fuel from the requirement to use a new, air-transport, shipping cask. The new (Type C) cask is intended to prevent release of intensely toxic plutonium in severe air crashes that existing casks could not survive.
With the startup of the THORP reprocessing plant in England, the recent cancellation of the Siemens fuel-fabrication facility at Hanau, and expansion of the fuel-fabrication facility in England, shipments of MOX (mixed-oxide plutonium/uranium) fuels by air to Germany are likely. Japan, too, may initiate air shipments of mixed-oxide fuel once the IAEA approves a new transport standard.
Air shipments pose environmental and public-health risks because of the possibility of a release of highly toxic plutonium in the event of an accident. Plutonium, if inhaled, is a dangerous carcinogen. Releases of plutonium in two military aircraft accidents in the 1960s required massive, hazardous and costly cleanups.
German experts contend MOX fuel is a "very low dispersible material" and essentially self- containing. In addition, in an air crash, they insist, existing casks are likely to remain sufficiently intact to limit releases of plutonium to an acceptable level. These casks "would only fail substantially in very severe accident conditions," according to a German working paper, which adds, "Serious aircraft accidents are quite rare." The German government justifies the exemption for MOX by claiming that the MOX fuel pellets themselves can withstand conditions more severe than the IAEA's air transport thermal test because of the way they are manufactured, so that the plutonium they contain would not be dispersed even if the shipping cask failed in a plane crash. Nevertheless, the IAEA regulations permit a far higher release rate of plutonium from the MOX pellets than they do for the cask-pellet system.
A technical analysis by Nuclear Control Institute finds a number of mechanisms that could result in dispersal of plutonium in the event of a severe accident. A high-velocity impact that breached the fuel cladding, followed by a fire of moderate temperature that burned for several hours, could cause substantial releases.
The U.S. government, in a position paper prepared for the Vienna meeting last September, warned the proposed exemption "negates the original intent for developing [separate] air transport standards." The U.S. paper expressed concern that the allowable radioactive release proposed by the Germans "is not based on any defined model or rationale and that no risk analysis has been conducted on this proposal."
Beyond the question of whether to exempt MOX fuel shipments from Type C casks, the adequacy of the IAEA Type C cask itself has been challenged by U.S. and international civil aviation officials. The key international air associations [International Civil Aviation Organization, International Air Transport Association, International Federation of AirLine Pilots Associations] take the position the standards are not adequate. Representatives of these organizations urge adoption of the higher performance standard required in the U.S. for plutonium air shipments, NUREG-0360.
The IAEA criteria for certifying an air-shipment cask ("Type C") differ from U.S. licensing requirements in two key respects, impact speed and test sequence. The U.S. test requires a cask to be propelled onto a hard target at a speed of 129 meters/second, as compared with the proposed IAEA test of 90 meters/second.2 The U.S. test requires the same cask to undergo both impact and fire tests, the latter defined as 800 C for 1 hour. The IAEA test does not. The Agency is prepared to allow separate casks to be used for the impact and fire tests because "high speed impact and long duration fires are not expected to be encountered simultaneously . . . "3 But the facts suggest otherwise. In 1992, an El Al cargo plane crashed into an apartment complex shortly after take off from Schiphol airport, near Amsterdam. According to FAA investigators, the plane's indicated speed at impact was 335 mph (150 m/s).4 The crash site burned for many hours.
A committee of the ICAO found that IAEA impact test criteria represented "less than half the energy" required for testing the "black box" flight recorder. The ICAO black box impact test corresponded to an impact speed of 130 meters/second, compared to the IAEA test of 90 meters/second. The ICAO also found that "the sequence of tests as presently proposed for Type C packagings did not replicate what was likely to happen in an aircraft accident." The ICAO called for sequential impact and fire tests on the same cask rather than the separate impact and fire tests on different casks that the IAEA will require.
Under U.S. law, the Nuclear Regulatory Commission must certify that a container will not rupture under crash and blast-testing equivalent to the crash and explosion of a high-flying aircraft."5 There is an obvious economic explanation for the lesser IAEA testing criteria. Conceding it "would be relatively simple" to devise a performance test for a package "which would guarantee that no package would ever fail in an accident situation," the authors of the new regulations maintain such a test "would exact a tremendous economic toll from world economies."6 They anticipate a package will fail "gracefully" and that it "will limit releases to accepted levels until the accident environments are well beyond those provided in the performance standards and then only gradually allow increased release as accident environments greatly exceed the performance test levels. . . "7 [emphasis added].
The experts concede, however, "there are only very limited data available on packagings tested to failure to see how release increases with severity of the accident environment."8
Germany has been the strongest advocate of exempting fresh MOX fuel elements from the pending air-transport requirements, thus allowing MOX to be transported by air in Type B casks. In 1992, 82 unused fuel elements intended for the abandoned German Kalkar breeder-reactor were flow from Belgium to Scotland. Germany intended to follow suit by flying 123 Kalkar fuel assemblies from Frankfurt airport to Scotland in 1993. Nuclear Control Institute publicized the risks of these shipments at a joint press conference in Wiesbaden in April 1993 with Joschka Fischer, Environment Minister of Hesse. The shipments did not take place. Now, with the shutdown of Siemens' fuel-fabrication facility at Hanau, some of Germany's mixed-oxide fuel could be fabricated in England and flown to Germany. The British have expressed a preference to the Germans for air shipment.9 Also, as recently as last year, mixed-oxide fuels were flown from Britain to Switzerland.
The IAEA's revision process got underway in the late 1980s. At that time, a number of nations were embroiled in a controversial plan to send plutonium reprocessed in France to Japan by air. Because the planes would refuel in Alaska, the shipping containers had to be licensed by the U.S. Nuclear Regulatory Commission. The plan was quashed when the shippers failed to design a cask that could meet U.S. standards. Our institute disclosed that a prototype package developed jointly by Japan's PNC and the U.S. Battelle-Columbus was tested at Sandia National Laboratory and failed.10 The impact of this disclosure was substantial. In 1988, the U.K. Advisory Committee on the Transport of Radioactive Material (ACTRAM) asked the IAEA to initiate a review of the IAEA's transport package criteria "in view of the different requirements of the USA."11
Now, nearly a decade later, the IAEA and the U.S. government have been unable to reconcile their different standards. The alternative --- shipment of plutonium by sea --- has turned out to be highly controversial. With tons of plutonium still to be returned to Japan from France and England (as well as from England to Germany, Switzerland and Belgium), will air shipments once again look attractive?
Decisions now taking place mostly behind closed doors needs to be opened up to public scrutiny. Sea shipments of plutonium have embroiled Japan and France in controversy. Is air transport of plutonium and mixed-oxide fuels a realistic alternative?
End Notes1. IAEA TECDOC 702, "The air transport of radioactive material in large quantities or with high activity," p. 11. Back to document
2. The impact speed of the reference worst- case crash, Pacific Southwest Airlines Flight 1771, on December 7, 1987, was 282 meters/second, as determined by the U.S. Nuclear Regulatory Commission. Back to document
3. IAEA TECDOC 702, p. 22Back to document
4. Personal conversation with National Transportation Safety Board investigator. Back to document
5. Public Law 94-79, introduced by Rep. James Scheuer, banned air transport of plutonium into or out of the U.S. until a crashworthy cask had been developed and licensed. Back to document
6. IAEA TECDOC 702, p. 15.Back to document
7. TECDOC 702, p. 15. However, elastomer seals in use in many Type B package designs will not fail gracefully under thermal conditions only slightly more severe than the Type B thermal test, but may fail abruptly, resulting in increases in leak rates of many orders of magnitude. Dr. Edwin Lyman, Princeton University Center for Energy and Environmental Studies, "Questions/Comments Concerning the Air Transport of 'Very Low Dispersible' (VLD) Material," May 8, 1995. Dr. Lyman recently joined the Nuclear Control Institute as its Scientific Director. Back to document
8. Ibid., p. 15 Back to document
9. German Bundestag Printed Matter 12/5448, July 19, 1993. Transmitted in a letter from the Federal Ministry for the Environment, Environmental Protection and Reactor Safety, dated July 14, 1993. Response to questions from delegates Dr. Klaus Kubler, et al. Back to document
10. "Air Transport of Plutonium Obtained by the Japanese from Nuclear Fuel Controlled by the United States," by Paul Leventhal, Milton Hoenig and Alan Kuperman, March 3, 1987, p. 5. Back to document
11. "The Transport of Civil Plutonium, by Air," Advisory Committee on the Safe Transport of Radioactive Material, May 1988, p. 2. Back to document
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