The Chernobyl reactor differed in many ways from power reactors operating in the U.S. and other nations. The Russian acronym, RBMK, stands for heterogeneous water-graphic channel type reactor. This reactor type uses graphite rather than a light water system. Design peculiarities of this kind of plant contributed to the accident.
Unlike other reactors, the RBMK had no containment structure to prevent release of contamination. Furthermore, there was no water environment or chemical mixing to capture the iodines and particulates.
Such a design would not be licensed by the Nuclear Regulatory Commission in this country, nor in most countries of the world. Studies done since the Chernobyl accident have shown that its releases would have been successfully contained by a U.S. type reactor. As a matter of fact, a test of a 37-foot tall scale model of a nuclear plant containment building was made at Sandia National Laboratories in New Mexico. The test showed that the type of light water reactor containment used at U.S. nuclear plants could withstand more than three times the pressure it was designed for without rupturing or fragmenting.
Both accidents were caused by Operator error and became huge media events. At TMI unit 2 the operator error of turning off cooling water came after the reactor was shut down. The core partially melted, but stopped when cooling was restored, proving that there is no such thing as a "China Syndrome." No excess amount of radioactive gas and particles was released from the plant, although a large amount escaped from the reactor piping system and was kept in the Containment. Containments (the garbage can over the tea kettle) exist in all non Soviet design plants to protect the public from this type of accident. There were no deaths, injuries or over exposures.
At Chernobyl unit 4 the Operator errors were made to keep the reactor running, to repeat some non-nuclear data. A nuclear energy burst equal to about 160 lbs of TNT occurred which led to a chemical reaction between the fuel and graphite (like charcoal), which is a design for producing weapons grade Plutonium and electricity at the same time. TMI-2 had metal and fuel only, since it was designed to produce only electricity. A large explosion followed, blowing the reactor top off, making a hole in the roof and throwing burning fuel and graphite up on the roof.
Radioactive gas and particle release went on for several days, causing widespread fear in Europe. Thirty six people were killed, many exposed to excess amounts of radiation, and a large area was evacuated.
Last updated June 27, 2012, 8:50am CDT.