Is it true that both work on the same principle of operation: the interactive fission chain reaction 235U/239Pu and the bombardment of uranium-235 by fast neutrons produce a fission chain reaction accompanied by an enormous thermal energy in addition to beta and gamma radiation?
The most probable fission products are known to be 94Sr amu and 140Xe amu plus two fast neutrons. If both reactions are a chain reaction and almost instantaneous, then why not?
Best Answer
A nuclear reactor cannot explode like a nuclear weapon.
For a thermal reactor -like Chernobyl or Three Mile Island- the neutron generation lifetime is too long.
For a fast reactor (and a thermal reactor) there is no mechanism for creating and maintaining a super prompt critical assembly sufficiently long for significant release of energy from fission.
You have to really work hard to assemble the correct material to create a nuclear weapon; you need to create a system that is super prompt critical using fast neutrons and remains so sufficiently long for the chain reaction to produce enough energy before pressure causes dis-assembly into a non-critical configuration. By super prompt critical is meant super critical on the prompt neutrons alone without having to wait for the delayed neutrons to contribute. See the Los Alamos Primer by Serber, available from Amazon: the early notes on the physics of a fission weapon from Los Alamos at the beginning of the Manhattan project.
The explosions at Chernobyl were a steam explosion, and a chemical explosion caused by oxygen reacting with aerosolized graphite. (At Three Mile Island the explosion was from oxygen reacting with hydrogen released from oxidation of the over-heated zircalloy fuel cladding.)
For a nuclear reactor, the safety concern is the removal of decay heat from the radioactive decay of fission products after the fission process is terminated. Decay heat is about 5% of full power at shutdown.
A major problem with the Chernobyl design is the core was over-moderated. Specifically, the graphite was the moderator and the cooling water was not needed as a moderator and in fact acted as a neutron poison. So when the cooling water was lost the reactor power increased: positive feedback. The old N reactor in the US was a graphite moderated, water cooled reactor used to produce Pu for the weapons program, but was specifically designed to not have this problem.
Also, Chernobyl did not have a robust reactor containment system, it had a reactor confinement system.