to what extent, we don't really know now. as they're unfolding very rapidly on an hour by hour, day by day basis and there are conflicting reports. >> reporter: if the reactors aren't too badly damaged and if the nuclear fuel tank can be refilled with water, control can be re-established. but the next few days are critical. david shukman, bbc news. >> as energy secretary was saying there, there are a lot of unknows, but we've been watching a lot of these flyovers from the helicopters trying to pour water on. there was discussion about doing acid and also just cement to entomb the reactor. >> that's right. and of course, the pilots of those helicopters trying to douse the danger, so to speak, are still facing a possible threat, too, even hovering about that area. no doubt a fluid situation and something we'll stay on top of. but for the moment, we're going to turn away from our top story for a bit. >> just a quick minute we're going to start our own march madness as president obama gets into the game as well and makes his picks, his bracket picks. i'm already losing. >> that's not a good way to start out. i know. >> what's going on? i know. >> what's going on? . >> that's not a good way to start out.