Nuclear labor issues the most dangerous tasks within the industry is intensified by nuclear secrecy. On May 22, 1986, a nuclear fuel reprocessing plant at La Hague in Normandy, sustained a mechanical malfunction. Five workers were exposed to unsafe levels of radiation and hospitalized. On April 12, 1987, the Tricastin Nuclear Power Plant fast breeder reactor coolant leaked contaminating seven workers. In July 2008, approximately 100 workers were exposed to a radiation leak. The Chernobyl nuclear reactor meltdown occurred on April 26, 1986, in the Ukraine, during a test of the Unit 4 reactor systems. The explosion and fire caused by human error
Ryanggang explosion popular speculation that the explosion was nuclear in origin. United States Secretary of State Colin Powell said there was "no indication" that it was nuclear, and South Korea similarly said that it did not appear to be nuclear. It would be some days before the effects of a nuclear explosion would be unequivocally visible to apolitical authorities. It would not be possible to hide the nuclear nature of such an explosion for long, as the radioactive isotopes created by a nuclear explosion would be detectable to outside observers around the world. North Korea initially denied that the explosion was nuclear.