>> well, i think that they are trying everything they can possibly do, and it's appropriate. they need to try every possible measure. but the fact that the radiation levels are prohibitive for carrying out the measures is disturbing. i wonder how long it can be sustained. >> the u.s. government today gave a more dire technical assessment of what's going on in japan than we've been hearing from the japanese government. the u.s. then changed advice to u.s. citizens,{ advising americans to evacuate further from the reactor area than japan had been advising. do you know why that shift happened? >> well, the nrc apparently published some calculations on its website that shows that there would still be significant doses 50 miles away from the site if all four reactors meltdown. this is really no surprise.