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• Tsunami survivors struggle for food and fuel as snow falls • Helicopter mission to cool spent fuel rods abandoned • Emperor says he is ‘deeply worried’ in rare TV address • Read the latest summary of events • Read the Guardian’s latest news story 2.31pm (11.31pm JST): It seems that a small number of people are benefiting from the nuclear scare: Adam Gabbatt reports here how sales of potassium iodide supplements, intended to limit the risk from radiation, have soared in the US and Canada. 2.23pm (11.23pm JST): The New York Times has gone big today on comments by Yukio Edano, variously described as the chief cabinet secretary or the government’s chief spokesman, that a cloud of steam rising from the No 3 reactor at the Fukushima nuclear plant indicated that the reactor’s containment vessel, designed to keep in radiation, might have been ruptured. At a subsequent press conference he said that there was little chance of serious damage. But as the NYT notes, the “rapid and at times confusing pronouncements” by Japan’s government are far from reassuring. 1.58pm (10.58pm JST): James Randerson has sent through some more interesting nuclear context, from the UK’s Institution of Mechanical Engineers . He particularly highlights this snippet: A concern for the people not just of Japan but the Pan Pacific area is whether Fukushima will turn into the next Chernobyl with radiation spread over a big area. The answer is that this scenario is highly unlikely, because of the wildly different design of the two reactors. The reason why radiation was disseminated so widely from Chernobyl with such devastating effects was a carbon fire. Some 1,200 tonnes of carbon were in the reactor at Chernobyl and this caused the fire which projected radioactive material up into the upper atmosphere causing it to be carried across most of Europe. There is no carbon in the reactors at Fukushima, and this means that even if a large amount of radioactive material were to leak from the plant, it would only affect the local area. The Japanese authorities acted swiftly and decisively in evacuating people living within 20km of the plant, and ensuring people living within 30km of the plant remained in their homes, with windows and doors closed. The radiation measured so far at Fukushima is 100,000 times less than that at Chernobyl. 1.46pm (10.46pm JST: My colleague Martin Shuttleworth has updated the Guardian’s before and after pictures showing the devastation caused by the Japanese tsunami . The images show a lot of is yet to recede from the worst hit areas. 1.41pm (10.41pm JST: Ian Sample, the Guardian’s science correspondent, has been talking to Andrew Sherry, director of the Dalton Nuclear Institute at Manchester University, about steam seen rising from the reactor 3. Ian says the fact steam is escaping does not necessarily mean any of the “serious containment structures” within reactor 3 have been damaged: Specifically, I wondered how the steam could be radioactive, given all the containment systems that surround the reactor core. This is different to the steam that is released regularly when the engineers vent the pressure vessel after pumping it full of seawater. One likely scenario is this: high pressures in the reactor vessel can cause it to dump steam into what’s called a torus beneath it. This is a metal donut half-filled with water. That torus was thought to be damaged in yesterday’s explosion, so steam might be leaking from that. Crucially, the torus is outside any of the serious containment structures – only the outer building can hold the radioactive steam in, but the outer building was torn apart in an explosion. Another source of the steam is water boiling at the spent fuel rod pools. 1.30pm (10.30pm JST): Good afternoon, welcome to the Guardian’s live coverage of the Japanese humanitarian crisis and latest updates on conditions at the Fukushima Daiichi nuclear power plant. Here’s a summary of the days events so far: • Authorities are struggling to control the situation at the Fukushima Daiichi nuclear plant , where the situation in reactors No 3 and No 4 remains fast-moving and perilous. Reactor 3 is a particular worry – Japan’s government said today that there a “possibility” that the reactor’s primary containment vessel for radiation had been damaged after steam was seen rising into the air. Attempts to drop water from helicopters was abandoned due to radiation levels. The latest mooted plan involves a police water cannon truck. Staff dousing reactors with seawater were forced to evacuate part of the building for a period this morning after radiation levels surged. These later receded and staff returned. French government ministers have urged the country’s nationals in Tokyo to leave Japan or else head south in case radiation is blown onto the capital, saying Japanese authorities had “visibly lost control”. • The country faces an increasingly desperate humanitarian crisis caused by the direct effects of Friday’s huge earthquake and resultant tsunami, one made worse by freezing weather. The official death toll has now hit 4,255 deaths, with 8,194 people registered as unaccounted for. Survivors, many of them homeless, are struggling with a wave of cold weather forecast to last well into this week, with night time temperatures dipping to -5C in some places. • Japan’s emperor, Akihito, has made a rare TV appearance to express his condolences to his people and his worry at the nuclear situation. • Following its precipitous plunge yesterday, Tokyo’s stock market bounced back nearly 6%. Japan’s central bank has injected a further $40bn into the financial markets. You can read our previous live blog following Wednesday’s developments here . Japan earthquake and tsunami Japan Natural disasters and extreme weather Nuclear power Fukushima plant status Adam Gabbatt Peter Walker guardian.co.uk