There is currently a great deal of speculation over whether or not they even tested a nuclear device. The only nation to agree that it was definitely a nuclear test is Russia. The U.S., China, and South Korea have not yet scientifically, conclusively determined that there truly was an atomic detonation on the weekend. The detonation on the scale that was detected at the time could have been created by a large-scale detonation of conventional bombs. No one will know for sure if what Kim Jong-il claims is true or not until all of the scientific data has been collected and analyzed.