A bit of good news from Fukushima Daiichi this morning: the extremely radioactive water that was spilling into the sea appears to have stopped flowing. But the situation at the plant remains grim, and could get far worse, according to a new assessment published in the New York Times.

First, the good news: For several days, extremely radioactive water has been flowing from the unit 2 reactor into the sea. The levels of activity have been staggering high, and have already begun affecting marine life in the area. Earlier today, the Tokyo Electric Power Company (TEPCO) announced that it had successfully injected some 5,000 litres of “coagulant” into the pool. I’m not sure what this coagulant is, but it’s been reported as some sort of hardening agent other than concrete.

That doesn’t mean there aren’t other leaks. In a press conference this afternoon, Chief Cabinet Secretary Yukio Edano told reporters that there could be other leaks from unit 2 or the other nearby reactors. TEPCO says it is investigating the possibility further. Meanwhile, the company is dumping tonnes of low-level waste water into the ocean in order to make room in storage vessels for high-level waste that must be cleared from the reactor buildings and the adjacent turbine halls, which have become radioactive cesspits. The decision to dump has angered locals and other nations like South Korea, who feel that they were not adequately consulted. Edano apologized and promised a more open discussion in the future.

The bad news is that new evidence suggests the situation inside the reactors themselves could be far more grim than what the Japanese have so far let on. The New York Times article this morning cites a confidential US Nuclear Regulatory Commission assessment that the reactors are really in terrible shape. It suggests that the fuel inside the cores is so melted down that cooling water has not been able to adequately circulate. The continued leaking of highly-radioactive water is also complicating the situation and raises questions about how long the current emergency cooling can continue. Adding to the problems is the revelation that old fuel from the spent fuel pools in units 1-3 may have spread as far as a mile after hydrogen explosions rocked the reactors. Buldozers were apparently used to at least temporarily cover hot fuel between two of the reactor buildings, but the discharge will make cleanup much more difficult.

The NRC remains extremely concerned about events that could further destabilize the reactors. For one thing, the extra mass of the water flooding the containment vessels could make them more vulnerable to an aftershock. Hydrogen build-up, caused by steam reacting with fuel rods, could also cause another catastrophic explosion. And apparently the threat of the reactors accidentally restarting remains real, as we discussed in our piece from yesterday.

To mitigate these dangers the NRC has made some recommendations, such as purging the containment vessels using unreactive nitrogen gas, and pouring more boric acid onto the reactor cores to stop a further meltdown. TEPCO’s latest statement on the reactors suggests that it is considering nitrogen injection.

For full coverage of the Fukushima disaster, go to Nature’s news special.

Credit: AP Photo/AIR PHOTO SERVICE