nowhere close to Chernobyle in terms of radiation linked, but same threat level.
Chernobyle involved an explosion, which sent irradiated gas into the atmosphere and poisoned large swathes of eastern and northern Europe, as well.
The Range in Japan is not, and will not be nearly as severe.
The only thing that remains to be seen is if there will be significant ground water contamination.
Atmospheric contamination meant that, while some sank to ground level and has kept many ground-surfaces near the site of the incident irradiated at unsafe levels to this day. Then again, the worst impacts were further away, where wind was able to carry it and drop off the little radiating buggers near more populated areas, and the doses only kept flowing and flowing downwind, and contaminated just about everything. And in the end, it wasn't really enough to even kill all that many (most sources state a surprisingly low death rate)... but then again, sometimes death is the better way out of some scenarios. So, in simple numbers, Chernobyl actually doesn't seem
that bad, until one takes into consideration how many children across every single generation since that tragedy, have been handed a terrible card in life. The radiation doses weren't enough to make that many people ill, but it was just enough to mutate some genetic material, and this has impacted children born even in this decade, iirc.
The biggest concern with Japan is groundwater contamination. You get a significant portion of the country's ground water irradiated to some degree, and we'll be documenting the country's health problems for the next few decades. Ground water contamination isn't simply a problem regarding drinking water. Ground water will hold onto the radiation for a fair bit of time, it will soak into the soil, and then likely get taken up in plants... and then there's the concern as to whether or not the ground water will carry the contamination all the way into the aquifer. I'm not that educated as to the depth, age, or location of any aquifers in Japan... so this may or may not be a realistic problem.
And of course, if there is no total meltdown where it leaks through into the ground, there isn't a serious concern about that then is there?
I haven't been following the disaster that much as of late, so other than the emergency level getting upgraded, I don't know the status at the moment. Last I knew, a total meltdown was almost entirely improbable, simply due to the way things were designed and the physics of the problems at hand. Total meltdown, where the fission material turns into a molten soup, and actually burns its way through the floor of the reactor head and containment building (so, melt through some steel/metal alloy that is multiple inches thick, and then continue to chew through about a foot or so of concrete.)... is incredibly hard to happen, it would essentially have to be a deliberate act and a conspiracy. As long as some options remain on the table, it's very hard to get to the point that it can run away so much and not stop heating up until it's through all of that material. Partial melts, where some material pools on the floor of the reactor, can and have happened... but a full-blown meltdown has never occurred. Never (iirc
😛). Three Mile was a partial melt with a controlled release, Chernobyl might not have even melted at all. Insane pressure buildup, and an insanely terrible nuclear facility design and management, led to that disaster. It simply blew the roof off the reactor, and hell iirc, I think the facility was essentially one containment building for two or three individual reactors.