One issue with the review of previous nuclear disasters: Chernobyl was qualitatively different than Three Mile Island and Fukushima. The latter 2 designs were both water cooled and water moderated; both suffered loss of coolant (LOC) events which resulted in the core melting from residual decay heat as described in the article, with Fukushima experiencing subsequent detonations of hydrogen gas formed from reactions with the heated fuel rods (some have claimed that this happened at TMI as well, but clearly not to the same scale). The Chernobyl design (http://en.wikipedia.org/wiki/RBMK) is also water cooled, but is moderated by graphite, which is much more dangerous (and scary that there are still many of these in operation). Instead of a loss of coolant event, Chernobyl experienced an exponential power spike which pushed operating power up to 10 times normal, resulting in a series of steam explosions in the coolant lines that blew off the 2000 ton cover of the reactor, sprayed part of the core out the top to contaminate the immediate vicinity (i.e. large chunks of the graphite moderator lying on the ground outside the reactor building), and set the graphite moderator on fire. The fire then spread many more fission products into the atmosphere with the smoke to share the fun with people in a much wider area.
Despite what has been written about Fukushima recently, I expect that it was a couple of orders of magnitude worse than Three Mile Island, which did not result in significant amounts of radioactive material escaping from the site (depending on whose analysis you believe); Chernobyl was between 1 and 2 orders of magnitude more severe than what we know about what happened at Fukushima at this point as far as I can tell.
I'm told that Xe poisoning played a major role in Chernobyl. MSRs have a major advantage here because the Xe can easily be removed. In a solid fuel, it is not really possible to remove it, and it can cause instability because it causes time lag between control input and reactor response output.
Good review but "qualitatively different" is a bit of an understatement.
tl;dr: Chernobyl/RBMK reactors are inherently dangerous in nuclear design and in operation without suitable containment structures, unlike Western reactors like TMI or Fukushima.
TMI and Fukushima are comparable to a degree but it is important to note that TMI is a Westinghouse pressurized water reactor whereas the Fukushima plants are GE boiling water reactors. TMI had a LOC event due to a stuck pressurizer vent valve that went undetected after a reactor scram which, combined with incorrect assumptions in the operating procedures, led to a core melt. Fukushima experienced station black out which means loss of both offsite and backup power. The reactors shutdown and operated as designed for this scenario but the design basis assumption is that power would be restored in 4 or 5 days (don't know the exact number). It actually took more than a week to restore power due to the devastation of the earthquake and tsunami. Core cooling was maintained by discharging steam into the containment cooling pools but this method can not be run indefinitely and as the pools overheat it threatens the containment. Without a source of power the H2/O2 recombiners could not safely burn off the hydrogen which led to explosions of the reactor service buildings.
In contrast, the RBMK reactors are graphite moderated but water cooled. The reason for this design was they were developed for civilian power generation by scaling up military reactors used for plutonium production for nuclear weapons (graphite moderator allows fuel extraction without shutdown). During low power operation, the RBMK design has a positive reactor power void coefficient. What this means is that an increase in power lowers the density of the water coolant which allows more neutrons to escape into the graphite moderator where they are slowed down and thus split more atoms. In other words these reactors have an inherently dangerous operating region where an increase in power can lead to more power in a positive feedback cycle. This is what destroyed the Chernobyl reactor. (Note that water moderated reactors such as TMI or Fukushima have a negative power void coefficient where an increase in power reduces the density of the coolant and moderator which allows neutrons to escape the core without causing a fission thus dropping power, the opposite of an RBMK)
Of course the designers were aware of the positive power void coefficient, so they added safety systems to prevent reactor operation in bad regions. On the night of the accident, a maintenance shutdown was scheduled but on scram the operators wanted to run a turbine spin down test, i.e. after the scram, see how long the residual steam could drive the turbines before backup systems had to be operational. Previous attempts to run these tests had failed and the operators were pressured by Moscow to get it done or else (Siberia?). To maximize the chance of a successful test the operators maneuvered the reactor into the low core flow, low power region of the reactor's operating domain with the dangerous positive void coefficient and thus positive power feedback. To get the reactor into this state the operators had to override numerous safety systems designed to prevent such operation. At the commencement of the test there was a power excursion that led to a power runaway that cause a steam (not a nuclear) explosion that blew the lid off the reactor.
One final important point, the Chernobyl reactors (and all RBMKs) are not housed in any containment structure like Western reactors (they are too big). The containment buildings of reactors like TMI or Fukushima are designed to withstand and contain the operating energy and nuclear material should anything go wrong and as these accidents have shown, they work. The Chernobyl accident was made much worse because the lack of containment allowed widespread dispersion of radioactive material due to the explosion and subsequent graphite fire.
By qualitatively different I mostly meant to point out that TMI and Fukushima were both LOC accidents at water moderated reactors, while Chernobyl was of a much more dangerous variety. This was motivated by the fact that the OP glossed over that important point, and now you have filled in even more of the blanks; thanks.
Yes, I just wanted to expand on how completely different these reactors and accidents were. Also, it was a minor point but LOC Accident (TMI) is different than a Station Black Out (Fukushima), these are defined accident scenarios in the design basis documents for the reactors.
Despite what has been written about Fukushima recently, I expect that it was a couple of orders of magnitude worse than Three Mile Island, which did not result in significant amounts of radioactive material escaping from the site (depending on whose analysis you believe); Chernobyl was between 1 and 2 orders of magnitude more severe than what we know about what happened at Fukushima at this point as far as I can tell.