The long term effects of Chernobyl on the UK, which got a dusting with radioactive particles due to winds, has been calculated as equal to smoking half a cigarette a year... China to Fukushima is not too far off the distance from the UK to Ukraine...
and the Japanese reactors have containment jackets, 6 inches of stainless surrounding the actual steam generation Pressure vessel, and inside the containment jacket, the bases are designed to catch and spread the melt in the case of a meltdown and hold it in a wide flat puddle with maximum surface area, so it can still be cooled before it eats through the base. The explosions only blew off the exterior sheds, nothing more than big raincoats to keep the weather off the machinery.
Chernobyl had no containment jacket, just the pressure vessel and the exterior weather cladding, when the hydrogen blew, just like with the japanese ones over the last few days, the blast blew open the pressure vessels and scattered the fuel around. The japanese ones just knocked out and scattered the weather cladding and left the pressure vessels safe inside their containment jackets...
I'm not worried about a chernobyl happening, I wouldn't like to be within a few Kms of the station in the open with the steam they are venting and the hydrogen bangs going off, but I'd happily be sitting inside a closed room in Tokyo eating sashimi.