Which material is the most radioactive?
The poor Firefighters who arrived first. Scientists calculated that they where exposed to a dose of 15Sv, thats 50 times the livetome dose of a material tester like me. :-(
Anyway metal, im sorry if i insulted you on the space station save, how about joining with a spaceship given credit to.
Sorry, Graphite... (i forgot the word)
@Nathan-65: Not granite, GRAPHITE. This is also a common problem with control-rods made of graphite, 'cause they don't absorb neutrons, they decelerate them, the excess energy from the deceleration will exposed as heat.
Then the reactor core exploded, launching the reactor lid into the air.
Also the control rods were inserted into the core, but it made an effect different than in a normal reactor, also the ends of control rods were made from granite.
@Nathan-65: It was both. There was a test to simulate a full energy black out, to see if the most important systems still can be supported until complete shut-down. For this there must be a little "rest-reaction" left. They where far below this minimum reaction rate as they started the test, so the reactor wasn't able to support itself, to compare that, the crew increased the reaction rate of the already overheating reactor, so it get's complete out of control and finally blows up.