hankyoreh

co-chief of the civillian-military joint investigation team into the sinking of the Cheonan reports the result of the team’s investigation

Scientists have been questioning the findings of the joint civilian-military investigation team that investigated the sinking of the Cheonan. Controversy is expected as the scientists raised issues regarding the analysis of materials adhering to the vessel’s hull and a torpedo fragment, a central piece of evidence in the team’s conclusion that the sinking resulted from a torpedo attack.

During an interview with the weekly Hankyoreh 21, to be published Monday, Dr. Panseok Yang, manager of the Microbeam Laboratory in the Department of Geological Sciences at Canada’s University of Manitoba, said that the material adhering to the Cheonan was “not the aluminum oxide (Al2O3) you would expect in an explosion.” Previously, Professor Seung-Hun Lee of the Physics Department at the University of Virginia in the U.S. pointed to errors in the team’s analysis findings on the substance, based on his own experimental results.

Previously, the team announced that it had concluded, based on an energy spectrometer analysis, that the three substances found on the Cheonan’s hull and the torpedo fragment and in an experimental explosion were all aluminum oxide, which materializes during explosions. The explanation was that the white substance burned onto the hull and torpedo propeller as aluminum powder in the torpedo’s explosive detonated (oxidized) in a reaction with oxygen.

Dr. Yang noted that the percentages of aluminum and oxygen found in the team’s findings differ from the ordinary percentages seen with aluminum oxide. The ratios of oxygen to aluminum in the team’s report were 0.92 for the substance adhering to the hull, 0.90 for the substance on the torpedo fragment, and around 0.81 in an underwater explosion simulation.

“During a simulation analyzing aluminum oxide with an energy spectrometer, the National Institute of Standards and Technology in the U.S. found that the ratio of oxygen to aluminum was 0.23, and the aluminum melting and rapid cooling experiment conducted by Professor Lee Seung-Hun gave a ratio of 0.25,” said Dr. Yang. “A ratio of 0.11 appears in a paper printed in the May 2009 issue of the Journal of the European Ceramic Society.”

Dr. Yang also said, “On this basis, we cannot say that the substance adhering to the Cheonan was the explosion byproduct of aluminum oxide.”

Yang acknowledged that the team’s work has been difficult, but said that they “need to be able to explain why their figures show abnormally high levels of oxygen.”

Previously, Professor Lee addressed the team’s announcement that the substance on the Cheonan’s hull and the torpedo propeller was noncrystalline aluminum oxide, with its molecules arranged irregularly, which appeared as the result of a torpedo explosion. He conducted an experiment that called the findings into question, saying that it was impossible for all of the aluminum to be noncrystalline or oxidized even after going through an explosion.

In response to his claims, the Ministry of National Defense said, “The detonation of explosives containing aluminum occurs within hundreds of thousandths of a second under high temperatures of more than 3,000 degrees Celsius and high pressures of more than 200,000 atm, and most of it becomes noncrystalline aluminum oxide.”

“Professor Seung-Hun Lee’s electric furnace experiment differed in its experimental conditions because it was not an explosion environment, so noncrystalline aluminum oxide could not be produced,” the ministry explained.

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