Today's Update
Fukushima has largely fallen off the news, but when it re-emerges it tends to be in some sort of panic-laden title that doesn't actually say anything. Nevertheless the crisis continues. At first we were worried about the reactors exploding, then about the Spent Fuel Pool burning to the ground. Now we're down to high-radiation water leaking out into the ocean. We've pretty much run the gamut from super-critical down to merely urgent.
Nevertheless, radiation is still spreading out there, so if you're concerned about friends and family in Japan, here's the word:
By Land: Radiation levels next to the plant are still high, but decreasing. The latest JAIF status reports are available on their website, and indicate that radiation levels at the main gate, which had gone up over 3000 &mu Sv/hour at the height of the crisis, are now down to 144 &mu Sv/hour. Radiation levels beside the building, which were unspeakably high, are now down to 910 &mu Sv/hour. For reference, in the US you are expected to get over 3000 &mu Sv per year normally - factors of two or three higher are not unknown. Plutonium was found in the soil, but it's unclear whether this was background plutonium (there's a lot of that in the soil ever since some people detonated a bunch of nuclear weapons in the open air).
By Air: The main worry is that radiation will spread by air. The immediate release of Nitrogen-16 with the steam is long gone by the time is leaves the evacuation zone, but other isotopes, like Tritium and the heavy metals, are there for duration. If a cloud of those particles makes it out into the mainland of Japan it can contaminate everything.
The best monitoring tool available right now is this crowd-sourced website, which lists radiation readings from official and independent sources all over Japan. Radiation levels are compared to the official Japanese yearly radiation exposure (a bit over 700 &mu Sv/year), and the US average rate (about 3000 &mu Sv/year). Radiation levels are in the normal stage south of Tokyo. North of Tokyo we've managed to inch above the Japanese limit, but it's not until you get to the coast that you get above the US average radiation dosage. Fukushima, of course, is basically on fire.
The worry is that we're going to get heavy metal particles from the spent fuel pools, which store used fuel rods that have already been used in the reactor, that will burn off as the spent rods overheat, in the atmosphere. Those particles will then combine with other heavy metal particles from the cooling steam that was pushed through the reactors themselves, which will float over Japan like a cloud of doom until they get rained down on the countryside. Increased incidence of cesium discovery has confirmed that there is something getting out of the reactor/SFP system and into the air.
By Water: Water is the big scare now. Iodine levels in Tokyo drinking water rose over the allowable point earlier in March for a day, before dropping down. Iodine still in the reservoirs will decay rapidly, dropping in strength by a factor of 1000 roughly every eighty days, and overall iodine levels have been decreasing ever since the reactors stopped on March 11th.
However, at the reactor complex itself there has been an accumulation of very radioactive water. The water may come from the tsunami, but it's unclear where the radiation has come from. The radiation levels, which are lethally high, are too high to be standard runoff from the breach in the wetwells, but almost too low to be from a massive corium breach of the Reactor Pressure Vessel. The water is not only making the basement of unit two inaccessible, but it's also close to the ocean. This is a secondary worry, since the amount of radiation leaked to the ocean would be relatively benign anywhere but near the plant, but it's definitely a worry. In the meantime, the main problem is that the radioactivity indicates that there may in fact be some sort of leak in the reactor vessel, and it's also keeping them from fixing a lot of the reactor machinery down in the basement, but they might be building some concrete dams just in case the water level rises. They would really like to pump all that water somewhere, but I don't know where they would put it.
The Good News: Power has been connected to several of the reactors. Additionally they're returning the cycling in the reactors from saltwater cooling to freshwater cooling, which is better for them. Attempts using fire trucks and other devices to increase the water level in the SFPs are continuing, and no major change in the SFP has been observed. Pressure levels in the Reactor Pressure Vessels are remaining stable. Overall radiation levels are continuing to drop, although the evacuation zone is still in place and likely will be for some time. Furthermore, despite worries, radiation counts in the rest of Japan, while high, are remaining within reasonably healthy levels, so there's no need to evacuate Tokyo.
In short, the crisis level has decreased significantly, but the long-term worries about radiation leakage remain. Additionally there's still a chance for things to go catastrophically wrong, but with each passing day it might actually be less.
Nevertheless, radiation is still spreading out there, so if you're concerned about friends and family in Japan, here's the word:
By Land: Radiation levels next to the plant are still high, but decreasing. The latest JAIF status reports are available on their website, and indicate that radiation levels at the main gate, which had gone up over 3000 &mu Sv/hour at the height of the crisis, are now down to 144 &mu Sv/hour. Radiation levels beside the building, which were unspeakably high, are now down to 910 &mu Sv/hour. For reference, in the US you are expected to get over 3000 &mu Sv per year normally - factors of two or three higher are not unknown. Plutonium was found in the soil, but it's unclear whether this was background plutonium (there's a lot of that in the soil ever since some people detonated a bunch of nuclear weapons in the open air).
By Air: The main worry is that radiation will spread by air. The immediate release of Nitrogen-16 with the steam is long gone by the time is leaves the evacuation zone, but other isotopes, like Tritium and the heavy metals, are there for duration. If a cloud of those particles makes it out into the mainland of Japan it can contaminate everything.
The best monitoring tool available right now is this crowd-sourced website, which lists radiation readings from official and independent sources all over Japan. Radiation levels are compared to the official Japanese yearly radiation exposure (a bit over 700 &mu Sv/year), and the US average rate (about 3000 &mu Sv/year). Radiation levels are in the normal stage south of Tokyo. North of Tokyo we've managed to inch above the Japanese limit, but it's not until you get to the coast that you get above the US average radiation dosage. Fukushima, of course, is basically on fire.
The worry is that we're going to get heavy metal particles from the spent fuel pools, which store used fuel rods that have already been used in the reactor, that will burn off as the spent rods overheat, in the atmosphere. Those particles will then combine with other heavy metal particles from the cooling steam that was pushed through the reactors themselves, which will float over Japan like a cloud of doom until they get rained down on the countryside. Increased incidence of cesium discovery has confirmed that there is something getting out of the reactor/SFP system and into the air.
By Water: Water is the big scare now. Iodine levels in Tokyo drinking water rose over the allowable point earlier in March for a day, before dropping down. Iodine still in the reservoirs will decay rapidly, dropping in strength by a factor of 1000 roughly every eighty days, and overall iodine levels have been decreasing ever since the reactors stopped on March 11th.
However, at the reactor complex itself there has been an accumulation of very radioactive water. The water may come from the tsunami, but it's unclear where the radiation has come from. The radiation levels, which are lethally high, are too high to be standard runoff from the breach in the wetwells, but almost too low to be from a massive corium breach of the Reactor Pressure Vessel. The water is not only making the basement of unit two inaccessible, but it's also close to the ocean. This is a secondary worry, since the amount of radiation leaked to the ocean would be relatively benign anywhere but near the plant, but it's definitely a worry. In the meantime, the main problem is that the radioactivity indicates that there may in fact be some sort of leak in the reactor vessel, and it's also keeping them from fixing a lot of the reactor machinery down in the basement, but they might be building some concrete dams just in case the water level rises. They would really like to pump all that water somewhere, but I don't know where they would put it.
The Good News: Power has been connected to several of the reactors. Additionally they're returning the cycling in the reactors from saltwater cooling to freshwater cooling, which is better for them. Attempts using fire trucks and other devices to increase the water level in the SFPs are continuing, and no major change in the SFP has been observed. Pressure levels in the Reactor Pressure Vessels are remaining stable. Overall radiation levels are continuing to drop, although the evacuation zone is still in place and likely will be for some time. Furthermore, despite worries, radiation counts in the rest of Japan, while high, are remaining within reasonably healthy levels, so there's no need to evacuate Tokyo.
In short, the crisis level has decreased significantly, but the long-term worries about radiation leakage remain. Additionally there's still a chance for things to go catastrophically wrong, but with each passing day it might actually be less.