South Korea’s Ministry of National Defense has responded to assertions of doubt over the Cheonan investigation results raised by Professor Lee Seung Hun of the University of Virginia’s Department of Physics.
Professor Lee, having conducted some experiments based on the evidence released by the Joint Civilian-Military Investigation Team, made claims that the evidence was false on June 17th.
Choi Moon Soon, a Democratic Party (DP) lawmaker, subsequently took Professor Lee’s work to be crucial evidence and submitted it to the UN Security Council. Pressian and Media Today, left-wing media outlets, also reported on Professor Lee’s paper extensively and themselves rejected the Joint Investigation Team’s work.
However, the Ministry of National Defense said on the 21st that it believes Professor Lee’s suspicions were based on inappropriate test conditions for the oxidation of aluminium at the time of the explosion.
Professor Lee’s evidence was based on the results of experiments into the oxidation of aluminium under very high temperatures. He asserts that only a part of the aluminium was oxidized, while the majority maintained its crystalline structure.
In other words, even if aluminium were oxidized during the explosion, it would not change to a 100% non-crystalline structure, he said. Therefore, an aluminium peak should appear during XRD (X-Ray Diffraction) analysis; however, he asserts that it was absent from his tests.
His logic follows that the absence of an aluminium peak proves that the material did not exist in the explosion in the first place.
However, the Ministry of National Defense asserted, “Professor Lee Seung Hun’s electric furnace experiment is one in which aluminium is simply heated (1100℃, 40 minutes) then tempered (cooled within 2 seconds), therefore it is obvious that a portion of the surface should be oxidized while most other parts are left as aluminium.”
“Generally, the explosives containing the aluminium explode within fractions of a second to temperatures higher than 3000℃ and pressures higher than 200,000 atmospheric pressures. Under such extreme conditions, aluminium quickly reacts with the oxygen within the explosives and mostly becomes aluminium oxide, a non-crystalline structure,” it went on.
“An electric furnace experiment cannot create such an extreme situation, which means that non-crystalline aluminium oxide cannot be formed. Therefore, this experiment cannot be used as a comparison.”
Regarding Professor Lee’s added assertion that an aluminium peak was not reflected in XRD analysis of the substance found on the surface of the vessel by the Joint Investigation Team, the Ministry explained, “When the aluminium oxide in the explosive is in a non-crystalline structure, it can be sighted by EDS (Energy Dispersive Spectroscopy). But in XRD data, an aluminium oxide crystal peak is not visible.”
Therefore, under conditions where most of the aluminium is a non-crystalline, there is the possibility of the substance avoiding detection in XRD. In a supplementary investigation, the Ministry of National Defense reported that in three complexes discovered, both crystalline (at a level which can be ignored) and non-crystalline structures were both found. Therefore, EDS analysis can show aluminium components which are not reflected in XRD analysis.
Therefore, the Ministry asserted in its explanation, “The absence of an aluminium oxide peak in XRD data cannot prove the absence of aluminium components in the substance on the surface of the vessel.”
Reacting to the controversy, a scientist from the Joint Civilian-Military Investigation Team stated, “Professor Lee is a physician, which allows him to approach the situation from a theoretical perspective, but I doubt whether he has the ability to research the chemical components based on an explosion under high temperatures and at high atmosphere pressure, and within one second to tens of thousandths down to hundreds of thousandths of a second.”
