Steam explosion major cause of human fatalities in volcanic eruptions. The 1986 Chernobyl nuclear disaster in Soviet Union was feared to cause major steam explosion (and resulting Europe-wide fallout) upon melting the lava-like nuclear fuel through the reactor's basement towards contact with residue fire-fighting water and groundwater. The threat was averted by frantic tunneling underneath the reactor in order to pump out water and reinforce underlying soil with concrete. When a pressurized container such as the waterside of a steam boiler ruptures, it is always followed by some degree of steam explosion. A common operating temperature and pressure for a marine boiler
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.