ChernobylOn April 26th 1986, the most serious nuclear accident in history took place at Unit 4 of the Chernobyl power plant located 130 km north of Kiev, Ukraine. The site had four RBMK-1000 reactors. These reactors are graphite moderated boiling water reactors and did not have a containment structure. Reactor containment is the large and thick concrete and metal structure surrounding the nuclear reactor. Its purpose is to protect the reactor from external damage, and to contain radioactivity in case of a significant reactor failure. By regulation, all western BWR and PWR reactors have to have a containment. Additionally, the RBMK design also had a very large and positive coolant void reactivity coefficient, meaning that as the coolant (i.e. water) temperature increases, the reactor power increases. This positive coefficient is not present in BWRs or PWRs.
A brief summary of the events is presented here, a detailed description can be found at http://www.world-nuclear.org/info/chernobyl/inf07.html. The following document (http://www.iaea.org/Publications/Booklets/Chernobyl/chernobyl.pdf) also includes information about the health and environmental effects of Chernobyl accident.
and Socio-Economic Impacts
Recommendations to the
Governments of Belarus,
the Russian Federation and Ukraine