In terms of the tsunami and even the earthquake, Tokyo is far from the disaster area, with much credit to its preparedness, e.g. its building codes. In terms of nuclear radioactivity, Tokyo is extremely close to the two nulcear plants in question.
It's not just nuclear explosions such as the atomic bombs or the Chernobyl incident that are immensely dangerous. Any exposure to nuclear radiation will have severe lingering health effect often passed on to the future generations. The disastrous effects of Chernobyl is well known but in the US, the effect of so called depleted uranium deployed in the Middle East by both Presidents Bush's military, are deliberately obscured, even denying the suffering of the returned veterans, when even their wives report being burnt by their semen! Just google "depleted uranium". While cancers and birth defects in far away land may be ignored, the depleted uranium is being wind blown all over the world and it will take billions of years to actually deplete.
There is nothing funny about radioactivity leaks or explosions. I'm not trying to alarm anyone but nuclear safety cannot be overemphasized. In fact, I'm hopeful on new nuclear technology, such as the meltdown proof pebble-bed nuclear technology in China and possible backyard nuclear cells to come. Of course, great strides are being made in other ways of generating or garnering energy. The Japanese plants in question are far from the Chernobyl design but I believe are still relatively old models with much better and added precautions against disasters such as just happened.
I hope and pray it is a good system and all dangers are controlled and contained and such good news will be confirmed soon.