It was xenon poisoning, positive void coefficient, and general incompetence during the test. Good overview:
http://hyperphysics.phy-astr.gsu.edu...ne/cherno.html

By the way, if you're worried about that one, Chelyabinsk is supposed to be worse. No single incident, but lots of separate incidents.

the chelbinsk one update me on that please

Mayak, the production facilities for plutonium.

Brief overview:
http://www.globalsecurity.org/wmd/wo...nsk-65_nuc.htm

More details:
http://www.nti.org/db/nisprofs/russi...k/nucwaste.htm

thanks i didnt know about this

You're getting Three-Mile-Island mixed up. 3MI had a small amount of hydrogen that exploded. Chernobyl's explosion was caused by the water vaporizing.

And although I mixed up my description a bit, I'm almost certain they didn't use enriched-uranium ("U-235") fuel rods. Uranium is difficult to enrich, and the plutonium is very easy to make and seperate from uranium 238; during any kind of sustained nuclear reaction, large quantities of U238 will be converted into Pu239. This is exactly why North Korea has plutonium to harvest, right now; Clinton gave them the reactors!! :rotfl:

Western countries dislike it (Pu) for this very reason; proliferation is far more difficult to prevent when plutonium is involved. Jimmy Carter felt the same way, which is why he suspended out breeder reactor program in the late 70's.

Graphite isn't used because about the only way you can use it is with a positive-coefficient. Because water flows and vaporizes during a critical event, it's a far safer moderator. If the reactor becomes out of control, vaporizing of the water will immediately reduce the neutron action.

tycho, you didn't learn in this all in chemistry class, now did you? :know:

i learnt nuclear physics in class and school very intresting we even learnt theres radioactive material in smoke alarms :yep: :smug:

I learned that in the hardware store. It didn't take 4 years and I didn't have to pay tuition. :smug:

i didnt pay tuition either school in england is free and is compolsory from 5 to 16 years

it acctualy learnt it all in the 5 years of senior school (11 to 16) i passed with very good grades in physics chemistry and biology my strongest subject being physics i acctualy passed with the highest mark for my course and paper i managed to achive 98% only thing was we all did foundation paper :damn:

i could have got an A* so i was told if i did the higher paper but oh well i got a C well got CC so im happy

Hi all,

Long time reader, first time poster.

I served onboard a US submarine as a reactor operator in the early '90s and we had a really good incident report on the Chernobyl Disaster. Wim Libaers link earlier in the thread pretty much summarizes the technical aspects. Our report was more critical of the design of the reactor. A positive temperature coefficient, very complex piping arrangement (didn't allow for natural circulation with the pumps secured), and aluminum cased graphite control rods were all major contributing factors to the massive human error and several violations of operating procedure that caused the disaster. Turning off emergency cooling systems and reactor safeguards at the same time? It doesn't take a rocket surgeon to figure out that that's not such a good idea... :88)

Basically they were trying to test the ability of residual heat in the core to power the reactor feed pumps until the local diesels came online. They did this with no reactivity control due to the Xenon transient, all the while adding reactivity due to boiling in the core caused by pressure drop due to lowering temperature by using residual heat to power the feed pumps and by reduced flow caused by securing the coolant pumps as per one of the few parts of the they actually followed..

Bad design plus Bad Operators=Disaster, or a car made by Ford. Take your pick; but I'll choose the Ford any day.

Have a great day!

(Just kidding about the Ford...I'd never actually buy one :D )