There is new news today of note -- the single most potentially dangerous situation at Dai-ichi, the spent fuel pool at reactor #4, has achieved an increased margin of safety, putting us largely into the cleanup phase. That will be plenty of work. Here's the update:
Tokyo Electric Power Company (Tepco) started setting up an alternative circulation system, utilizing a heat exchanger, at unit 4 in mid-July. The system is designed to pump warm water out of the pool, cool it, and then return the water to the pool. The company said that it began a test run of the system at 0:44 am on 31 July. The temperature of the pool at that time was between 86°C and 87°C. Tepco said that following the successful trial run of the system, it had now put it into full operation.
By 5:00 pm on 31 July, the temperature of the pool had fallen by a few degrees, but by 8:00 am on 1 August the temperature had reportedly dropped to 63°C.
Tepco said that it intends to reduce the temperature of the pool of unit 4 to between 30°C and 40°C within one month.
5/4 -- TEPCO has managed to get a remote controlled camera to inspect the spent storage pool at building 4, and it appears to be holding water reasonably well, which significantly reduces the risk from that particular pool. The pool is holding the offloaded core of reactor #4 and had concerned engineers and raised speculation of high risks, such as highlighted by the US NRC's Jaczko in a dramatic March 16th news conference that raised intense concern among those knowledgeable about reactor design.
Unlike the reactors themselves, spent fuel pools have no hard containment, and normally hold only spent fuel. But when the tsunami struck, the pool #4 had the recently offloaded core of reactor #4, which was undergoing maintenance. Seeing that the pool holding this relatively potent and still very heat-producing core is holding water, instead of only being sprayed with water, allays a major concern.
While paranoid-style blogs speculated all manner of frightening scenarios -- even that the EPA was falsifying or hiding data, no less -- the better informed and more realistic blogs and discussions eschewed paranoia and were concerned about certain precise aspects of the Dai-ichi situation, and the spent fuel pool at #4 was by far the foremost of these to my mind.
4/12 -- NYTimes on the radiation releases (though the headline is overly dramatic, the details in the article are worthwhile). Note you cannot reach solid conclusions just from the headline and first paragraph, but must read through the article.... Much of the releases have been in water, most of which is on site and needs to be stored and cleaned later. --> Most of the releases are still at Daiichi.
The majority of the airborne (portion of) releases to date were in mid-March, and the most significant fallout (on land) went to the northwest (including some beyond the evacuation zone, resulting in the new expansion to some areas to avoid long-term, gradual exposure).
Can the highly contaminated water be cleaned and discharged? Yes:
US Nuclear Regulatory Commission on the 3-Mile Island accident and cleanup. "Today, the TMI‑2 reactor is permanently shut down and defueled, with the reactor coolant system drained, the radioactive water decontaminated and evaporated, radioactive waste shipped off‑site...and the remainder of the site being monitored. ..."
For those wishing an excellent review of health effects at Chernobyl, which although larger in magnitude (to date), is still indicative of effects if one reduces the scale, see this from the WHO.
4/11 -- Is existing Nuclear Energy a Net Good? I've spent a fair amount of time here on this post trying to give readers more accurate information than they would get unless they read very widely with good discrimination (though the NYTimes is really up-to-speed now) and some knowledge of physics and nuclear stuff.
But a larger issue is whether nuclear power in the form we have subsidized and tolerated so long is a good idea to begin with.
This is a complex question, and without trying to review all of the factors in how we got here (but for those that wish for some of that here's a good Fresh Air interview), we can apply a powerful concept to discriminate whether this kind of nuclear power, or future kinds, are really worthwhile.
It is the wisdom of the crowd combined with the maximization of utility and the internalization of externals.
Simply put, every source of electric power for businesses and consumers should have its true, full costs put into the final price the consumers of electricity pay. The same should apply to oil products like gasoline.
This would look very different than what we have now.
For example, about 45% of US electricity comes from coal, but that is in part because we subsidize coal electricity production by allowing coal burning utilities to emit harmful emissions without paying their true health and environmental costs. We subsidize coal burning profoundly.
The degree of subsidy would be a surprise to many, no doubt.
We know we have subsidized nuclear power in several ways also, including costs of emissions.
In short, we subsidize the wasting of energy by making energy prices artificially cheap compared to true costs.
The full costs of an energy source includes all the costs -- health costs such as asthma and deaths from coal burning, coal-emitted mercury contamination of soil and people, massive climate change costs of carbon burning, nuclear contamination and storage costs, the costs of naval fleets and operations in the Persian Gulf to protect oil shipping lanes, and....finally, direct subsidies.
If all the true costs of every energy source -- nuclear, coal, oil, wind, solar -- were fully included in the final prices consumers pay, then we would all be able to choose more wisely and choose how to conserve, and which source to use.
True pricing would drastically alter our energy use for the better, and greatly aid the environment, and greatly improve the lives of our children through direct health effects.
How to do this? End all subsidies of all kinds for all energy sources now, and include in oil taxes the true full costs of defense and climate change, and in coal the true full costs of pollutants and climate change directly as taxes/fees on the users (mostly utilities) in proportion to emissions, all the costs of nuclear that haven't been included like disposal and health costs (one way to figure health costs for a reactor type is to use a global average of health costs per year to date for that reactor type), and even all the costs of solar panel production pollutants, and for wind energy the electrical transmission build out costs. Simply include the costs in the price to each source!
Likely most of our existing nuclear plants in the US would be viable under this true cost regime due to the fact that so much of their subsidies were already paid in the past by taxpayers. Meanwhile, current operational costs are low, while future spent fuel storage costs are diluted due to the sheer fact of an already existing necessity to store large amounts of spent fuel from decommissioned reactors and military sources (the marginal cost for new electricity generation creating more spent fuel doesn't add much to the existing large (overhead) costs all nuclear activities have already incurred.). In short, the storage costs are already here, and a little more doesn't amount to much, so most reactors would be economic still. The more interesting and significant consequence of including future costs based on risk assessments and storage costs would be that some types of reactors might need significant modifications to reduce risks and reduce calculated risk-based costs/fees to remain economically viable, and some reactors might do worse or even become uneconomic and get shut down. The true cost effects would be a more careful and rapid change in improving backup systems and strategies. It's one thing to be regulated, another thing to have to pay for risk-costs in actual dollars. It's a stronger incentive.
Finally, as wind power transmission and storage technology improves some of the plants might become uneconomic and get shut down earlier than they would have before. True costs make this timing rational and economic.
Once we approach that true pricing, the wisdom of the crowd will take over and make wise choices. People will conserve due to higher costs becoming finally visible -- you pay in your electric bill instead of in your tax bill or in your health insurance bill. Conservation will sharpen and quicken.
This would be a major needed change in our public policy, and deserves more than just an update on the Daiichi crisis, so I'll put this on my short list for a post.
Update 4/8 AM -- Interesting stuff today --"Isolated spikes in radiation inside reactor 1 containment have been associated with possible fuel movement during the April 7 aftershock, but radiation dose rates elsewhere at the site continue to decline." (from the NEI update today , in blue highlight beneath my comments below) Also, this frankly encouraging info from the NYTimes. (Another bit: the American firm which worked on closing down 3 Mile Island is also involved now on working out what to do later).
...800 of Toshiba’s engineers are helping the Tokyo Electric Power Company, which operates the Fukushima Daiichi plant, with the more pressing problem of cooling the reactors and reducing the radioactivity there. About 250 engineers are stationed in Fukushima, and an additional 500 are working at Toshiba’s nuclear engineering center in Yokohama, Japan.
They are helping to re-establish electrical power to pumps and motors and to install power panels; draining contaminated water; and acquiring desalination equipment, underwater pumps and air purifiers to filter radioactive dust. Westinghouse has provided Tokyo Electric with boron, fuel, spare pumps and other supplies.
Update 4/7 PM -- I thought it might be useful for many readers to have a general summary of points that are missing from most news articles, but are central to the situation at the Daiichi complex. (Also see the 4/7 NEI update in blue highlight, below my comments, and some more on the current situation from NYTimes.)
- Reactors 1-3 almost certainly had partial meltdowns, and not full meltdowns, with reactor 1 believed to have had the larger degree of melting. It's thought likely neither pressure vessel of reactors 1 or 3 (the interior steel vessels that hold the reactor cores) were melted through, but it is thought that possibly some fuel at reactor 2 found a route to leak down from the pressure vessel into the "drywell" (the strong concrete containment vessel which is the primary defense against a major escape of fuel material in a situation like this (and which Chernobyl did not have)).
- The partial meltdowns imply loose fuel fell to the bottom of the pressure vessel at reactor 1 and other reactors, into new, random groupings of fuel. Since the control rods are still in place and rise up from the bottom of the pressure vessels, the new groupings of fuel in reactor 1 are likely able to create only modest and/or intermittent amounts of fission, and new fission products (Iodine-131, Cesium, etc.). This amount of fission is unpredictable but won't be of a large magnitude (these partially melted cores have water on them, unlike Chernobyl, which had more powerful explosions, uncontrolled meltdown, and an open graphite fire without water or containment).
- Since the normal cooling systems of the reactors are not yet back on line, the reactors continue to be cooled only by injecting fresh water, which is then heated by the in-place rods and any partially melted cores, resulting in radioactive steam (radioactive both from meltdown piles and from remaining rods that are cracked open and leak radionuclides). This steam is then directed by design into the suppression chambers, the torus of water at the base of each reactor that exists for this express purpose.
- The excess of water due to the injections must eventually be removed or escape from each reactor system, else the pressures would rise to levels above the design strength of the containment. Earlier in this crisis pressure was relieved by direct venting of steam into the atmosphere.
- Excess water has been escaping by leaks. The leaks are of very radioactive water.
- These leaks could be ongoing until normal cooling systems are back on line, even if water is intentionally removed through piping, since it is believed the suppression chamber at reactor 2 is damaged and the containment at reactor 3 is damaged -- and both of these imply a route for leaks. Such leaks likely account for the large amounts of radioactivity in the water in trenches and loose in buildings at the Daiichi site. As leaked water accumulated and rose, it progressed finally into the ocean nearby and measured levels in the ocean near the plant spiked (even before the intentional releases).
- Relatively less radioactive water has lately been intentionally released into the ocean to clear room in containers on site to store more highly contaminated water from around the complex.
- The unintentional leaks' pathways to the ocean are now said to have been stopped.
- Room for storage of highly radioactive water on site is crucial, as water in some trenches and in the basements of the turbine buildings must be removed to allow work to proceed to restore the primary reactor cooling circulation systems. Primary cooling is key to reducing emissions long term, as it will end the necessity of endlessly injecting new water.
- More concerning to me than the reactor cores at this point in time is the exact situation of the spent fuel pool at reactor 4, which had the entire core from reactor 4 added to the pool for maintenance at the time of the earthquake/tsunami. Some or possibly a significant amount (a speculation) of all the airborne contamination in the evacuation zone and near the zone could have come from this pool, if the water level got low enough. It's unknown whether pool 4 accounted for much emissions, since radioactive steam was being vented from reactors at about the same time. This was the most frightening possibility raised by the US NRC, as these pools have no strong containment structures to slow or trap radionuclide emissions should they run dry, only the weak external shells of the buildings, and you know what those look like now. Two fires occurred in building 4, and were claimed by TEPCO to not have been from the pool itself. These pools are said officially to be "under control" (see quote below), but one open question to me is whether pool 4 holds enough water to mostly cover the rods, or something less good such as holding little water and needing constant spraying of water just to keep heat down, in which case it's possible that pool 4 could be an ongoing source of newly contaminated water. This is a speculative possibility, but I also would not be surprised to learn, in contrast, that the pool is able to cover or mostly cover the rods with water after all. I will be looking for news/information on this. (NYTimes 4/7: "Tokyo Electric said it was unsure of the status of the damaged No. 4 reactor because it has not been able to station workers there." This suggests several possibilities, but one of the more plausible possibilities is that there is significant radiation in the building near the pool. If so, the implication would be there are at least seriously damaged rods at pool 4, if not worse.)
- Overall, progress is being made at Daiichi, odd as that sounds with the recent reports of newly discovered contamination in the ocean. Compared to the the worst case -- radioactivity levels rising so high workers are forced away from the area except for self-sacrifice missions -- we can still reasonably hope for progress at the moment.
While the program proceeded at first with some simplified explanations, soon there began a series of fascinating details and considerations. What would be the effect of eating fish and seaweed from near the reactors for a year?--not as much as we'd think (for instance a possible dose of 1/4th of normal background radiation! -- see NEI 4/4 update in blue beneath my own updates). One of the highlights was a discussion really about the town that has gotten one of the denser falls of radiation just NW of the expanded evacuation zone. An amazing graphic came up -- a figure representing what level of radiation exposure might be...politically? socially? healthwise? um, tolerated, you might say...before evacuating more land. The graphic showed an actual number for cancer risk at the high end of its scale -- 100 milli-Sieverts (mSv) is expected to increase one's cancer risk (above the existing level) by 0.5%. 10mSv is thought to have little discernible effect (try telling that to people afraid of drinking milk that had magnitudes less). 50 mSv is thought to indicate evacuation.
The mental disconnect about magnitudes we have over here has been undone over there by the urgency of the situation. They have to figure it out.
The Japanese are doing the most difficult kind of social/economic calculus, in real time, and under time pressure, with many unknowns. It's about as challenging as decisions can get. And they are working their way through this. May luck be on their side.
Update 4/3 PM -- In the blizzard of details on the nuclear reactors, the most significant point might not be clear or may have disappeared in the blizzard -- that if normal cooling systems are restored for reactors 1-3, then whatever damage exists on the reactor #2 suppression torus or reactor #3 containment vessel suddenly becomes less dangerous. Once normal cooling systems for the reactor pressure vessels (which now contain the partially melted cores) are restored, then these pressure vessels will be cooled by circulating cool water, so that the heat, pressure and steam in those vessels would be reduced, in turn reducing or ending the need to vent radioactive steam, and reducing or ending the pressure that drives any leaks at #2 and #3.
A steady circulation of cooling water into the reactors would be so much better. For this reason, the updates of progress reported by the NEI (in blue below) are quite significant. Each bit of progress is one of many necessary steps to achieve reactivating the normal cooling systems.
Update late PM 4/1 -- Just saw this new article at NYTimes, where Energy Secretary (and Nobel laureate in physics) Steven Chu, who has the best access to information, military monitoring data, and nuclear experts who work under him says "70%" of the core of reactor 1 suffered severe damage (thus implying there was no full meltdown!). Further: "the best information the United States had received from the Japanese authorities indicated that water was once again covering the cores of the stricken reactors and that pools of spent fuel atop the reactor buildings were “now under control.”
In addition to the severe damage at Reactor No. 1, the Energy Department said that Reactor No. 2 had suffered a 33 percent meltdown. Mr. Chu cautioned that the figures were “more of a calculation” because radiation levels inside the plant had been too high for workers to get inside, and sensors were unreliable.Note that reactor 2 is thought to have damage to it's condensation torus (the steam control torus of water at the bottom of each of these reactors through which steam from the reactor pressure vessels is released). One emission possibility is leaking water from the #2 torus. There are assertions reactor 3 has a crack in it's containment vessel, which might or might not then leak significant fluid (the containment vessel is the 3rd area water from a core travels to in an overheating situation -- 1rst it vents from the pressure vessel as steam if pressure is too high, then this steam is directed into the suppression chamber which is the torus of water to control such steam, and then if pressure and heat builds in the suppression chamber sufficiently then it would bleed into the containment vessel, which is a major line of defense. Note that a major crack in this 3rd vessel, the containment vessel, would allow faster leaking of radiation (only faster, as an overpressurizing vessel is to be vented to release pressure, ergo radioactivity) if the situation was that reactor (#3) had significant ongoing fission, which is an unknown.)
Update 4/1 PM -- Some minor clarifications and extra detail added to the 3/31 summary below due to reading a technical scenario. My piecing-together aligned surprisingly well with the professional analysis.
Update 3/30 PM, 3/31 noon: This is a good time for a general summary, as news tends to make it appear the situation has fundamentally changed for the worse. It has, and it hasn't. It's been widely speculated that at least one core (reactor #1) and likely more have had at least partial meltdown(s). It remains plausible and reasonable to speculate either way about full meltdowns -- that there may be or may not be any fully melted core.
A partial meltdown means that portions of fuel rods were above water long enough to melt some of the upper sections, resulting in at least some significant amount of fuel falling to the bottom of the pressure vessel(s). In such random regrouping of fuel at the bottom of a pressure vessel, the resulting unstructured masses of fuel are potentially able to emit significant amounts of fission products. They might emit a lot, or they might emit relatively less, depending on their random new geometry. But since it is unknown how much fuel has melted down, we can say little that is definite, except that the amounts of fission products resulting, that have been created and will be created, are unpredictable and a significant portion of these radioactive products escaped from the cores are likely in water (and water leaks), while some escaped during the steam venting.
We can say some simpler, broader generalizations, such as pointing out that an intense, lasting fire that lofts large amounts of radioactive material such as Chernobyl had seems ruled out due to the very different structure of these reactors. We can also point out that it is very likely that much of the resulting new fission products have been entrapped into water, for now, and of course this means that the amounts of radioactive fission products eventually and randomly released outside of the reactors and pools will be variable (rising and falling) as water escapes the confines of the piping and containment.
One of the most important and simple generalizations is that any result like Chernobyl is very unlikely here -- an ongoing, open fire to loft radionuclides seems ruled out. Still, on a smaller scale, fires that did happen, such as in the building of reactor #4, likely did loft some radioactive material. Further, some lofting happens without smoke or ash simply due to the effects of hot air rising. But without ongoing fire and lofting ash flakes, emitted (with steam) heavier particles will tend to fall sooner (on average) and thus travel less than at Chernobyl. Thus, while some will travel far, that amount will be less than at Chernobyl. The degree of propagation is still significant near the plant and for tens of kilometers, dependent on wind, and quite random. We'd expect to see some areas in the exclusion zone with more contamination, while many areas would have relatively little.
We can only measure to discover how much and where.
All of the above generalizations have been true all along, so in an important sense, the fundamentals are much the same as a week ago. Otherwise, this situation remains, as it always has been, unpredictable, and the worst case scenarios remain concerning but less probable (due to the containment structures and the water). The spent fuel pool in reactor 4 was a very concerning wildcard -- and still is under some question(!) -- as the pool held the entire offloaded core from reactor 4, and no containment structures protected that core except the water in the pool alone. (It was frightening to hear the prediction by our NRC that pool 4 was going dry!) It's unclear how low the water level got, whether the pool liner had/has any leaks, etc. That is a large wildcard, but the pool was said to have water (presuming it can hold water, which seems plausible as there is no ongoing nuclear fire, no obvious huge release), so thus the size of any release of fission products from pool #4 (which if water is now covering most of the rods in the tank would now be finished most likely) is unknown to my knowledge. Finally, regarding speculations of reactor core full meltdowns and penetrations (melt-through) of the pressure vessels (the interior vessel but not the 'containment vessel'), this seems possible for one core, but no sure thing -- it's also possible it did not happen. So long as reactor cores always held at least some water, then those vessels would not have a melt-through (as the water would simply boil and remove heat from the new masses at the floors of the vessels).
Only a few possibilities have been entirely ruled out. We can't predict overall emissions of radioactive particles. We can only monitor and try to be accurate in our assessments of what the actual levels are, so as to respond when and where needed. One further generalization is that with multiple agencies and groups monitoring radiation levels (such as in the US), we can trust the public findings.
The official reports of radiation levels are going to be generally reliable. Here and over there.
Update 3/29 PM: There's plenty of fear of the unknown, and the headlines at the NYTimes (sometimes the subtitles, e.g.-- "Bad news has undermined optimistic statements about the nuclear crisis by officials") and of most media are taking full advantage of peoples' general lack of mathematical and technical knowledge. Plutonium is widely used as a hook for readers, in a sensational way. One thing to consider is that the tiny amounts detected could have come from *any* and all of the reactors, as normal reactor fuel mixes produce Plutonium and likely all 3 of the troubled reactors and the pool at the 4th have emitted fission products, and thus Plutonium.
There is still a shortage of information.
Update 3/27 PM: It now appears the leak is more likely to be from either piping or from a possible cracked suppression chamber of reactor #2 (the doughnut shaped chamber of water that helps control venting of steam from the reactor pressure vessel). Either of these is less worrisome than a crack in the reactor pressure vessel itself. Update 3/25 PM: The possibility I mentioned this morning of the new leak happening through pipes (instead of the reactor itself) seems more likely due to the new update below -- see 7PM March 25 update in blue beneath.
Update 3/25 AM: It appears that some route or routes exist to allow a more significant degree of radiation (though still far smaller than Chernobyl -- by many orders of magnitude) to leak from reactor 3 (and 2?), including one view which suggests the plausible possibility of a leak from one of the reactor water circulation/cleaning systems. This would explain radioactivity in the water in the adjacent building where these pipes travel. Another source asserts the reactor vessel itself has a crack (but it is unclear if a reactor crack alone would result in the water contamination in a different building).
The New York Times at the moment has a better quality of reporting than it did early in this ongoing drama, having come more up to speed and found some good sources to interview. To add to the linked article, let me point out that A) if the leak is solely from piping, it would be less serious than if the reactor were leaking more directly; and B) in spite of the problems posed by either such leak, it remains possible that the majority of fuel in the core has remained in rods and thus cooled in it's residual nuclear fission reactions (by the passage of time) and thus in its heat production. Of course it remains possible much of the fuel has melted down also. It appears to me at the moment that the more dangerous scenario of a full meltdown is unlikely, as I would expect more steam and radioactivity to air emissions. Either way, it remains to be seen. More later.
Update 3/18 early PM: As suggested in this blog days ago, the nuclear problems in Japan are far from the catastrophic events (Chernobyl like) suggested by so many headlines of the last few days. While I will follow developments further, I doubt further daily updates will be cogent. Let me say I had no crystal ball, simply some physics courses (for majors) in college in which I paid attention and a willingness and ability to read technical analysis.
Bloggers and the reporters and editors of various newspapers have only given us the level of comprehension they have -- clearly not adequate here -- and failed to make the effort to delve into technical stuff in depth, even when the stakes justified the effort. Perhaps some of the sensational headlines and writing may have been cynically gauged to take readers on a ride (to hook readers), but I suspect simple ignorance and lack of effort was the more predominate factor. It's worth remembering next time you read a headline.
Update 3/17 AM: Little decisive information as of late morning (central time, US). One of the primary concerns to me is that the fuel rods in the storage pool at reactor 4 included the off-loaded rods from reactor 4 which may not be spent, and may even be quite potent, with nuclear fuel inside that would react significantly (and then emit significant radioactive products into the air) if they could melt down in an empty (empty of water) storage pool -- but many crucial factors are not clear: how potent the rods are, how much water is in the pool, and the central one: how hot would the rods get without water (likely not as hot as fully potent rods more recently used than these). In short, there is a lack of important information. Further, it gets quite technical even if there were more information, and so it's not all that predictable to an engineer from another field, in spite of reading various discussions (so far).
One thing I've seen is some speculation by some with some technical knowledge (but not real expertise) that is self-reinforcing, psychologically. That is, once one has a scenario in mind, the mind tends naturally to look for information to validate that particular scenario, and downplays most information that suggests other possibilities.
Basically, we don't know what is going to happen, and probably an expert with sufficient information to make a more likely scenario (than others) isn't motivated to disclose his thoughts, as there is no gain in taking a position that is moderate. All the possible gain -- to one's career -- can only come from foreseeing reasonable dangers and prioritizing them and suggesting ways to mitigate or eliminate such dangers. In other words, by thinking of possible catastrophes, and recommending appropriate actions to reduce the likelihood or the consequences of such possibilities.
In a sense, we are in something a lot like the fog of war.
Some popular blogs about economics that I've glanced at today have shown a (quite natural) reliance on mainstream news media for their information about the Japanese nuclear situation. This approach is wanting. As I have a background in Engineering Physics, I've been able to read technical discussions and I can tell you they are much less alarming than the headlines of 3/15 or early 3/16 -- including some headlines at the New York Times.
This doesn't mean the situation cannot deteriorate. There are ways it could deteriorate seriously.
While no one expects the first-rate reporters at the New York times -- among the best in the world -- to be able to distinguish whether an official or expert is simply covering bases in a field like nuclear physics, I am still disappointed in clear sensationalism in headlines lately at NYTimes.com. Blogs on the other hand depend on the familiarity of the writer with the material, so that they rely on the quality of their input sources. In the area of technical physics/nuclear physics/nuclear engineering, we really need writers that are able to follow the technical details.
Since the popular blogs I have glanced at at the moment fail to discern the overly-cautious quality of statements from officials and experts -- designed to protect themselves from even small possibilities of being wrong or underestimating events -- I offer readers a more accurate site for a few-times-a-day (but not hourly) review of information: Expert information can at times be much better information. This is one such time. From the Nuclear Energy Institute (who will not profit from understatement, but only from accuracy -- they must maintain credibility, and that means giving out accurate information):
UPDATE AS OF 10 A.M. EDT, WEDNESDAY, APRIL 13:Workers at the Fukushima Daiichi nuclear power plant are pumping radioactive water from the concrete enclosure near reactor 2 into a turbine condenser. A series of aftershocks that rattled the area Tuesday has put the work behind schedule. Tokyo Electric Power Co. (TEPCO) is inspecting another storage facility on the site to determine if it can hold contaminated water from the basement of the reactor 2 turbine building. Radioactive water in the turbine buildings is hampering efforts to restore cooling operations at the plant.
TEPCO continues to inject cooling water into reactors 1, 2 and 3 and to spray water as needed into the used fuel pools for reactors 1-4. TEPCO also continues injection of nitrogen gas into the containment vessel of reactor 1 to prevent a possible explosion of hydrogen that may be accumulating inside.
UPDATE AS OF 11:30 A.M. EDT, MONDAY, APRIL 11: No damage to Japan's nuclear power plants was reported today after another strong aftershock hit the northeast coast. The temblor, measured at magnitude 6.6 by the U.S. Geological Survey, rocked the country one month after the magnitude 9.0 earthquake and tsunami struck March 11, damaging the Fukushima Daiichi nuclear power plant. A magnitude 7.1 aftershock rattled Japan April 7. The Monday earthquake prompted the temporary evacuation of workers at the plant and interrupted the offsite electric power supply for less than an hour. Injection of cooling water to reactors 1, 2, and 3 resumed within an hour. Officials reported no new damage or increased radiation levels. Workers continued to spray water into the spent fuel pools of reactors 1-4 as needed. As an additional safety measure, Tokyo Electric Power Co. (TEPCO) has brought additional diesel generators to the site as a backup in case offsite power is disabled. Preparations are being made to transfer highly radioactive water from reactor 2 to a water storage tank. Workers are inspecting the tank to ensure there will be no leaks. TEPCO is injecting nitrogen gas into the reactor 1 containment vessel to reduce the possibility of a hydrogen explosion. TEPCO plans to inject nitrogen into the containment vessels of reactors 2 and 3, the Japan Atomic Industrial Forum reported. TEPCO used a drone helicopter to take aerial pictures of reactor buildings that are highly contaminated. TEPCO also is using remote-controlled heavy equipment to remove radioactive debris. Japanese authorities announced that residents of some municipalities outside the 12.5-mile radius evacuation zone will be relocated to reduce long-term radiation exposure. Radiation can accumulate in some places based on weather and geographical factors. The relocation orders will apply to areas where there is a possibility of residents receiving a dose of 2,000 millirem over the course of a year. UPDATE AS OF 11:30 A.M. EDT, FRIDAY, APRIL 8: No nuclear power plants were seriously damaged in the heavy aftershock that rattled northeastern Japan Thursday, the International Atomic Energy Agency reported. The epicenter of the 7.1 magnitude earthquake was 12.5 miles from the Onagawa nuclear power plant and about 75 miles from the Fukushima Daiichi site, where engineers are working to restore fuel cooling capabilities that were lost in the original March 11 temblor and tsunami. Fukushima Daiichi At Fukushima Daiichi, the injection of cooling water into the reactor pressure vessels of reactors 1, 2 and 3 continued Friday, along with injection of nitrogen gas into the containment vessel of reactor 1. The nitrogen will prevent possible ignition of hydrogen that may be accumulating in the containment. Tokyo Electric Power Co. is continuing the discharge of low-level radioactive water from a waste storage tank into the Pacific Ocean to make room for highly radioactive water pooled in the basement of the reactor 2 turbine building. Isolated spikes in radiation inside reactor 1 containment have been associated with possible fuel movement during the April 7 aftershock, but radiation dose rates elsewhere at the site continue to decline. The government lifted restrictions on shipments of raw milk and some produce from municipalities near Fukushima Daiichi. An official said tests show the food is safe to consume. The aftershock of April 7 caused minimal, if any, disruption at other nuclear power plants. UPDATE AS OF 1:00 P.M. EDT, THURSDAY, APRIL 7: Tokyo Electric Power Co. continued to inject cooling water into reactors 1, 2 and 3 at the Fukushima Daiichi nuclear power plant, despite a 7.1 magnitude aftershock that hit 70 miles north of the plant..... Fukushima Daiichi Seawater radiation levels, while still significantly higher than government safety limits, have decreased near the power plant since TEPCO blocked a leak of highly radioactive water into the ocean. TEPCO said it is too early to credit stopping the leak with the decline. Workers continued to inject nitrogen gas into the containment vessel of reactor 1, a process that began Wednesday. Inert nitrogen gas is used in reactor containment vessels to stabilize the atmosphere. The nitrogen injection is to prevent possible ignition of the hydrogen that is believed to be accumulating inside the reactor 1 containment. It is expected to take six days to complete the process. Spraying water onto the used fuel storage pools at reactors 1-4 was interrupted briefly because of the earthquake. TEPCO continued its controlled discharge of low-level radioactive water into the Pacific Ocean to make room in storage tanks for more highly contaminated water on the site. The highly radioactive water in turbine building basements is hampering efforts to restore cooling systems, particularly for reactor 2, where the radiation is highest. Before the highly radioactive water is pumped into the wastewater storage tank, the facility must be inspected for damage, the Japan Atomic Industrial Forum reported. Inspection could take up to a week. The Japanese government is evaluating possible evacuation of some residents from areas within 12.5 to 18.5 miles of the Fukushima Daiichi site. Residents in the 12.5-mile zone were evacuated early in the emergency. Those within the outer area have been advised to stay indoors. The additional evacuation would be from areas where radiation has accumulated since March 11. UPDATE AS OF 11:30 A.M. EDT, TUESDAY, APRIL 5: Tokyo Electric Power Co. (TEPCO) continued efforts Tuesday to stop the flow of radioactive water from the Fukushima Daiichi nuclear power plant into the Pacific Ocean. On Saturday, workers found a crack in a concrete enclosure used to carry electric cables near reactor 2. Since then, TEPCO has attempted to seal the crack with concrete and with an absorbent polymer, with no success. A colored liquid tracer was injected into the system of enclosures Monday to determine the flow path of the water. The test showed that the radioactive water may be leaking from a cracked pipe, and then seeping through gravel into the concrete enclosure. Today, TEPCO is taking a new approach: sealing gravel under the enclosure with liquid glass. TEPCO has not yet announced the outcome. To free up storage space for highly radioactive water in a waste disposal tank, TEPCO has begun to discharge 11,500 tons of low-level radioactive water into the ocean. The utility will use the tank to hold highly radioactive water that has accumulated in the basements of the reactor 1, 2 and 3 turbine buildings. Small fish caught in waters south of Fukushima prefecture have been found to contain radioactive cesium. The Ibaraki Prefecture government said 14 picocuries of radioactive cesium was detected in one kilogram of sand lances. The acceptable limit is 13.5 picocuries per kilogram. This is the first time radioactive cesium has been found in fish at a level above the government limit. Workers continue to inject cooling water into reactors 1, 2 and 3. In addition, spent fuel pools for reactors 1-4 are sprayed with fresh water as needed to keep them cool. (See NEI's video, "Spent Fuel Storage in Pools at Nuclear Energy Plants," for more information about how these pools work.) UPDATE AS OF 11:30 A.M. EDT, MONDAY, APRIL 4: Workers at the Fukushima Daiichi nuclear power plant continued searching Monday for sources of contaminated water leaking from the site into the ocean. Attempts to seal a crack in a concrete enclosure for cabling in reactor 2 are ongoing after initial efforts failed. Tokyo Electric Power Co. (TEPCO) injected a color tracer into the enclosure in an effort to track the flow of water. That test confirmed the radioactive water is from multiple sources. TEPCO is planning to install underwater silt barriers near the intake for reactor 2 to help contain the contaminated water. Japan's Nuclear and Industrial Safety Agency (NISA) and Nuclear Safety Commission both said it will take several months to restore permanent core cooling for the damaged reactors. NISA said it will take that amount of time to remove contaminated water from the turbine buildings and restore damaged plant equipment. To free up storage space for highly radioactive water in a waste disposal tank, TEPCO is seeking approval to discharge 11,500 tons of low-level radioactive water into the ocean. The utility said the radiation level in the water to be discharged is very low. TEPCO estimated that someone eating fish and seaweed from the adjacent water every day for a year would receive a total exposure of 60 millirem, less than a quarter of the average annual exposure from natural radiation. Workers continue to inject cooling water into reactors 1, 2 and 3. In addition, spent fuel pools for reactors 1-4 are sprayed with fresh water as needed to keep them cool. Radiation dose rates at the Daiichi site continue to fall. Recent readings showed 12.4 millirem per hour at the main gate, 7.4 millirem per hour at the west gate and 78 millirem per hour on the side of the administration building facing the reactors. UPDATE AS OF 3 P.M. EDT, SUNDAY, APRIL 3: Tokyo Electric Power planned Sunday to inject water-absorbing polymer into a cracked concrete enclosure near the reactor 2 water intake at the Fukushima Daiichi nuclear power plant in an effort to stop radioactive water from leaking into the ocean. Yesterday, pouring concrete into the concrete enclosure, which carries electric cables, failed to seal the crack. TEPCO said it had not found water leaking from the concrete enclosures at other reactors, the Japan Atomic Industrial Forum reported. Following detection of the reactor 2 leak, the power company began testing radiation levels in sea water 15 kilometers (about 9.5 miles) from the facility. A U.S. Navy barge has begun supplying fresh water as injection continues to cool reactors 1, 2, and 3. TEPCO is using a motor-driven pump powered by an off-site transmission line. A second barge with more fresh water has arrived at the site. Electric power has been restored to lighting in the turbine buildings of reactors 1, 2, and 3. Radiation Measurements After consultations with nuclear experts from the United States, TEPCO has begun to measure radiation levels inside the nuclear power plant's 20-kilometer (12.5 mile) evacuation zone. Measurements have been taken routinely outside the zone, but TEPCO has been reluctant to conduct tests closer to the plant because of anticipated radiation exposure to workers taking those measurements. Radiation levels off site and at the site boundary are generally decreasing, although localized areas with elevated levels are being identified for further analysis. Protective action recommendations for food and water are gradually being lifted in many locations, but some remain pending further analysis. The government is looking carefully at how and when to allow evacuees to return to their homes. The situation remains difficult for evacuees, especially the elderly and ill among them, but the government is escalating efforts to accommodate those who have evacuated. The government is monitoring children up to 15 years old in some prefectures for possible iodine-131 exposure. Based on preliminary results, iodine-131 has not been found at levels that exceed action levels, and in many areas there has been no exposure. UPDATE AS OF 12 P.M. EDT, SATURDAY, APRIL 2: Recovery efforts continue at the Fukushima Daiichi nuclear plant in Japan, as aid pours in from the international nuclear community in the form of technical expertise, protective equipment for workers, storage tanks for contaminated water and other measures. Today, Tokyo Electric Power Co. (TEPCO) said it has identified one likely source of contaminated water reaching the Pacific Ocean, accounting for some of the radiation readings in seawater samples taken over the past several days. The crack is in a two-meter-deep concrete "pit," or trench, that contains power cables near the reactor 2 water intake. Water measuring between 10 and 20 centimeters deep was found in the pit with radiation levels of more than 1,000 milliSieverts per hour. TEPCO plans to pour concrete to patch the crack while continuing to search for other potential leak paths. The Nuclear Industrial and Safety Agency says iodine-131 will be diluted in seawater and does not pose a threat to the public. Additionally, iodine-131 has a short half-life-about eight days-and will decay to harmless levels fairly quickly. (See NEI's fact sheet to learn more about the health impacts of iodine-131.) The Japan Atomic Industrial Forum said TEPCO is obtaining a "massive, hollow floating platform" from Shizuoka City and will use it to store contaminated water from the Fukushima site. The float can store up to 18,000 tons of water. Meanwhile TEPCO and the Japanese government are working to identify safe methods for transporting and storing contaminated water. UPDATE AS OF 12:30 P.M. EDT, FRIDAY, APRIL 1: Japan's nuclear safety agency has reprimanded Tokyo Electric Power Co. for not providing radiation monitors to all emergency workers at the Fukushima Daiichi nuclear power plant. Each worker is supposed to have an individual radiation monitor, but some emergency teams have had to share monitors, the Japan Atomic Industrial Forum reported. TEPCO said that low-priority work will be suspended if employees do not have monitors. TEPCO said that only 320 of the 5,000 radiation monitors were available after the earthquake and tsunami, JAIF said. Radiation Found in Beef Radiation that exceeds safety standards has been found in beef in Fukushima and three neighboring prefectures, JAIF reported. Radiation also was found in spinach and other vegetables grown in the area. Japan's health ministry said the beef and vegetables have not been shipped and are not on the market. Fukushima Daiichi A U.S. Navy barge containing freshwater to cool the reactors and used fuel pools at the Daiichi site has been towed to the pier. It will be connected to the pumps with hoses. Meanwhile, injection of freshwater continues at reactors 1-3 and workers continue to spray freshwater on the used fuel pools for reactors 1-4. TEPCO is evaluating the use of a synthetic resin that would be sprayed over debris at the site to prevent the spread of radioactive dust. Additional equipment, including the biggest concrete pump in the world, is being provided by U.S. companies. The pump's 70-meter boom can be controlled remotely. It has been in use at the Savannah River Site, helping build a U.S. government mixed oxide nuclear fuel plant. Concrete pumps are already in use at the site to assist with spraying water into the used fuel pools. UPDATE AS OF 11:30 A.M. EDT, THURSDAY, MARCH 31: A minuscule amount of radioactive iodine was detected in milk in Spokane, Wash., the U.S. Environmental Protection Agency reported. The agency said the level detected-0.8 picocuries per liter-is more than 5,000 times lower than the level that would prompt any action by the U.S. Food and Drug Administration to pull milk from grocery stores. "These types of findings are to be expected in the coming days and are far below levels of public health concern, including for infants and children," the EPA said. The EPA has increased its nationwide monitoring of milk, rain water and drinking water (see the agency's website for information on radiation air monitoring). Fukushima Daiichi Tokyo Electric Power Co. is increasing its efforts to remove radioactive water that has pooled inside concrete vaults that house pipes near the reactors at the Fukushima Daiichi nuclear plant. Maintaining cooling water flow to the reactors and used nuclear fuel storage pools and containing and removing the contaminated water continue to be priorities for workers at the site. Contaminated water was found in the basements of the turbine buildings at reactors 1-4 and in the concrete vaults outside the buildings. Workers finished pumping water from the reactor 3 turbine building and are removing water from the reactor 1 tunnel into a storage tank. Today, TEPCO has been pumping contaminated water from the reactor 2 turbine building into a storage tank. Freshwater injection continues to cool reactors 1, 2, and 3. The company also is spraying cooling water into the used nuclear fuel storage pools at reactors 1-4. (For information on how spent fuel pools work, see NEI's video.) Fukushima Daini All reactors at the Fukushima Daini site remain in safe condition. Smoke seen at reactor 1 at the Daini site on Wednesday resulted from a short circuit in a sump pump at the reactor. The smoke stopped after workers at the facility opened the power supply to the breaker for the pump. The cause of the short circuit is being investigated. UPDATE AS OF 6:30 P.M. EDT, TUESDAY, MARCH 29: Tokyo Electric Power Co. said that cooling water is being added to the spent storage fuel pools at reactors 2 and 3. Reactor 2 was using a temporary motor-driven pump and reactor 3 was using a truck to pump the freshwater into the fuel storage pools. The International Atomic Energy Agency (IAEA) said that plans are being made to begin pumping freshwater into the fuel storage pool at reactor 4 starting today. IAEA said that 63 food samples taken March 24-29 in eight prefectures (Chiba, Fukushima, Gunma, Ibaraki, Miyagi, Niigata, Tochigi and Yamagata) were below regulatory limits set by the Japanese government for iodine-131, cesium-134 and cesium-137. New analyses of seawater about 1,000 feet from the discharge point of reactors 1 through 4 show "a significant decrease" in radiation levels from March 26, IAEA said. Readings for iodine-131 went from 2,000,000 picocuries (1 picocurie is one-trillionth of a curie) per liter on March 26 to 297,300 picocuries per liter on March 27. Readings for cesium-137 went from 324,324 picocuries per liter on March 26 to 51,351 picocuries per liter on March 27. IAEA said that radiation readings in seawater "will be quite variable in the near future depending on water discharge levels." [note this prediction was shown on the 29th and 30th to be quite true, as levels spiked up] Japan's National Research Institute of Fishery Science has analyzed five fish samples from the port of Choshi in Chiba prefecture and found concentrations in the fish to be "far below any concern for fish consumption." Four of five samples showed cesium-137 concentrations below the limit of detection. In the remaining sample, cesium-137 was found to be slightly above detectable levels. IAEA said the situation was evolving, but that concentrations of radionuclides in seawater would soon drop to lower values by dilution and that the levels in marine food would most likely not reach levels above regulatory limits set for consumption. In the United States, the U.S. Environmental Protection Agency's daily data summary from its RadNet radiation air monitors across the United States show typical fluctuations in background radiation levels as of 8:30 A.M. EDT. "The levels detected are far below levels of concern," EPA said. UPDATE AS OF 9:30 A.M. EDT, MARCH 27: Tokyo Electric Power Co. workers on Sunday were using pumps to remove highly contaminated water from the basement of the turbine building of reactors 1 and 2 at the Fukushima Daiichi nuclear power plant. TEPCO also was preparing to remove water from the turbine building of reactor 3. Removal of the contaminated water is necessary to continue power restoration to the plant. By Sunday, water injection to the pressure vessels at reactors 1, 2 and 3 had been switched from seawater to freshwater. Off-site power has been restored to all units and work to connect equipment is ongoing. Progress is being slowed by high radiation levels and wet equipment. TEPCO said that earlier reports of extremely high radiation levels measured in the water in the basement of the reactor 2 turbine building were inaccurate, according to news reports. UPDATE AS OF 7:00 P.M. EDT, MARCH 25: Fresh water is being injected into the reactor pressure vessel at reactor 3 at Fukushima Daiichi nuclear power plant, Japan's Nuclear and Industrial Safety Agency said. TEPCO said that radioactive materials discovered at the reactor 3 turbine building possibly came from water from the reactor system, not the spent fuel pool. TEPCO made that statement after collecting samples of contaminated water in the reactor 3 turbine building and conducting a gamma-emitting nuclide analysis of the sample. The reactor pressure and drywell pressure at reactor 3 remained stable on Friday, leading TEPCO to believe that "the reactor pressure vessel is not seriously damaged. Cooling efforts at Reactor 1 already had switched back to fresh water cooling. Reactor 2 is still being injected with seawater, but is expected to switch to fresh water soon. Tokyo Electric Power Co. said that crews continued spraying water into the used fuel storage pools at reactors 3 and 4 on Friday to keep the used uranium fuel rods safe. Also on Friday, the heat removal system at reactor 6 was switched to a permanent power supply, NISA added. TEPCO said it was assessing the radiation dose to two workers who were contaminated while laying cable in the turbine building of reactor 3. TEPCO said it had instructed its employees and contract workers to pay attention to their personal radiation dosimeter alarms and evacuate when necessary. On-site radiation monitoring at the Fukushima Daiichi nuclear power plant indicates that radiation dose rates continue to decrease, the International Atomic Energy Agency said. Radiation Monitoring Update Air and seawater sampling continues by the Japanese government. Measurements in the ocean were taken 30 kilometers off-shore and 330 meters from the discharge points on March 23 and March 24. Results indicate concentrations of iodine-131 at 2,162 picocuries per liter and cesium-137 at approximately 703 picocuries per liter. Adult consumption of 1,000 picocuries (1 picocurie is one-trillionth of a curie) per liter concentration for 30 days will result in 24 millirem of radiation dose. For comparison, a typical dose from a chest x-ray is 10 millirem. The concentrations found in the seawater samples are most likely "due to atmospheric fallout rather than just ocean currents," IAEA said. Dilution is expected to rapidly decrease this surface contamination, IAEA added. Iodine-131 was detected in drinking water in 13 prefectures and cesium-137 was detected in drinking water in six prefectures. All results remained below the limits set by the Japanese government, IAEA said. Iodine-131 levels in drinking water in Tokyo are now below limits for consumption by infants set by the Japanese authorities and restrictions have been lifted. On March 25, the IAEA radiation monitoring team made additional measurements at distances from 34 to 62 kilometers from the Fukushima Daiichi nuclear power plant. At these locations, the radiation dose rate was at extraordinarily low levels, ranging from 0.073 millirem per hour to 0.88 millirem per hour. UPDATE AS OF 9:30 A.M. EDT, MARCH 25: Japanese officials are investigating the source of higher radiation readings at reactor 3 at the Fukushima Daiichi nuclear power plant after two workers were contaminated while laying cable in the turbine building. Tests of the water in which the workers were standing contained a concentration of radioactive material many times the level normally found in water circulating in the reactor, the Nuclear and Industrial Safety Agency said. "When we looked into the composition of the water, the source...seems to be the reactor core," said NISA's Hidehiko Nishiyama. "Another possibility is the spent fuel, and we cannot rule out that possibility either." Several possibilities could account for the presence of radioactive materials in the turbine building. Seawater sprayed onto the fuel pool area may have washed over the floor of the fuel pool area onto the turbine building and leaked through the damaged roof into the basement of that building. Other possibilities include a problem with an interconnected system to the primary containment, such as the main steam system, or a small opening in the reactor containment structure. Japanese authorities recommended residents within 30 kilometers of the plant evacuate voluntarily, extending the recommendation from 20 kilometers. Damage to infrastructure in the area from the earthquake severely limits the ability to provide water, food and other necessary supplies to people sheltering in their homes for the coming weeks. Tokyo Electric Power Co. is stepping up efforts to switch from sea water to fresh water for cooling the reactors and used fuel storage pools. The United States government has urged the switch to fresh water as soon as possible and is providing two U.S. Navy barges, each of which can carry up to 1,000 tons of water. The ships are scheduled to reach port about 60 kilometers from the Daiichi plant in about three days. Japanese workers at the site will install pipes and hoses to carry the water to the plant. .... UPDATE AS OF 11:20 A.M. EDT, FRIDAY, MARCH 18: Reactors 1, 2 and 3 at the Fukushima Daiichi nuclear power plant are in stable condition, with workers continuing to provide seawater cooling into the reactors. Containment integrity is believed to be intact on reactors 1, 2 and 3, and containment building pressures are elevated but are within design limits. Site radiation doses have been decreasing since March 16. Radiation dose rates are fluctuating based on some of the relief operations, such as adding cooling water to the used fuel pools. Recent readings at the plant boundary are about 2 millirem per hour. Radiation dose rates at reactor 3 range between 2,500 and 5,000 millirem per hour. The Japanese Self-Defense Force restarted cooling water spray into the Unit 3 reactor building and spent fuel pool at around 1 a.m. EDT on March 18. Plans are to spray 50 tons of water on the reactor 3 reactor building/spent fuel pool using seven fire-fighting trucks. A diesel generator is supplying power to reactors 5 and 6. TEPCO is installing high voltage cables from a nearby transmission line to reactors 1 and 2. Once electricity supply is re-established, priority will be given to restoring power to reactor heat removal systems and cooling water pumps. Workers are seeking to install electrical cables to reactors 3 and 4 components in about two days. UPDATE AS OF 10:20 P.M. EDT, THURSDAY, MARCH 17: TEPCO continues to install cables, transformers and distribution equipment to restore offsite grid power to Fukushima Daiichi reactors 1 and 2. Reactor 1 has now been included in the power restoration plan. Chief Cabinet Secretary Edano said in a recent conference that plans are in place to use 30 water cannon trucks and fire engines to spray water into the reactor 3 spent fuel pool, and TEPCO is discussing whether to do the same for the reactor 1 spent fuel pool. The spraying work is to be done in the next few hours, after the cable work is completed. UPDATE AS OF 9:15 P.M. EDT, THURSDAY, MARCH 17: Tokyo Electric Power Co. said it hopes to activate the cooling system for Fukushima Daiichi reactor 2 "as early as Friday night" (Japan time). The company said it could restore power from the electric grid to reactor 2 by Thursday night (U.S. time). The International Atomic Energy Agency reported that TEPCO completed connecting electrical cable from a makeshift transformer to reactor 2 at 4:30 A.M. EDT. Engineers were waiting to complete spraying sea water into the reactor 3 fuel pool before they restore power through the cable to the reactor 2 cooling system. TEPCO says that if it can provide power supply to the other reactors, it could begin restoring some cooling functions. The company said that after fire trucks injected water into reactor 3's fuel pool, radiation levels at the plant's west gate dropped from 31 millirem per hour to 29 millirem per hour at 10:00 A.M. EDT. UPDATE AS OF 5:00 P.M. EDT, THURSDAY, MARCH 17: It is unlikely that radiation released from the nuclear reactors in Japan will harm anyone in the United States, President Obama said in a press briefing this afternoon. "We do not expect harmful levels of radiation to reach the United States, Hawaii, Alaska or U.S. territories in the Pacific," Obama said. He added that the Centers for Disease Control and Prevention "does not recommend that people in the U.S. take precautionary measures other than staying informed." Obama said "our nuclear plants have undergone exhaustive study and have been declared safe for any number of contingencies." However, he said that when there is an event such as the Fukushima accident, "we should learn from that. That's why I have asked the NRC to do a comprehensive review of our nuclear plants" in light of the natural disaster that has happened in Japan. In a briefing earlier on Thursday, Gregory Jaczko, chairman of the U.S. Nuclear Regulatory Commission, said, "There can't be any harm to anyone in the United States" from the Japanese nuclear power plant. Dan Poneman, the deputy secretary of energy, said today that two U.S. flights to Japan collected information on radiation levels. These readings informed the decision to recommend that Americans evacuate an area 50 miles from the Fukushima Daiichi nuclear energy facility. Poneman expressed confidence in the safety of U.S. nuclear power plants, saying they're evaluated on a "minute by minute" basis. Taking safety precautions "goes back decades," he said. Tough safety standards have been in effect and upgraded since 1979, he said. Status of Fukushima plants In Japan, engineers have laid a power line that can connect reactor 2 of the Daiichi facility to the off-site power grid, the International Atomic Energy Agency reported. Workers are working to reconnect the power to reactor 2 after they complete spraying water into the reactor 3 complex to provide additional cooling to the used fuel pool. Reconnecting to the power grid is expected to enhance efforts to prevent further damage at the plant. Japan's Nuclear and Industrial Safety Agency reported on Thursday that the backup diesel generator for reactor 6 is working and supplying electricity to reactors 5 and 6. TEPCO is preparing to add water to the storage pools that house used nuclear fuel rods at those two reactors. UPDATE AS OF 1:30 P.M. EDT, THURSDAY, MARCH 17: Radiation readings at the Fukushima Daiichi site boundary were measured today at a lower level, between 2 and 3 millirem per hour. UPDATE AS OF 11:35 A.M. EDT, THURSDAY, MARCH 17: Fukushima Daiichi The reactors at the Fukushima Daiichi plant are in stable condition and are being cooled with seawater, but workers at the plant continue efforts to add cooling water to fuel pools at reactors 3 and 4. The status of the reactors at the site is as follows: Reactor 1's primary containment is believed to be intact and the reactor is in a stable condition. Seawater injection into the reactor is continuing. Reactor 2 is in stable condition with seawater injection continuing. The reactor's primary containment may not have been breached, Tokyo Electric Power Co. and World Association of Nuclear Operators officials said on Thursday. Access problems at the site have delayed connection of a temporary cable to restore off-site electricity. The connection will provide power to the control rod drive pump, instrumentation, batteries and the control room. Power has not been available at the site since the earthquake on March 11. Reactor 3 is in stable condition with seawater injection continuing. The primary containment is believed to be intact. Pressure in the containment has fluctuated due to venting of the reactor containment structure. TEPCO officials say that although one side of the concrete wall of the fuel pool structure has collapsed, the steel liner of the pool remains intact, based on aerial photos of the reactor taken on March 17. The pool still has water providing some cooling for the fuel; however, helicopters dropped water on the reactor four times during the morning (Japan time) on March 17. Water also was sprayed at reactor 4 using high-pressure water cannons. Reactors 5 and 6 were both shut down before the quake occurred. Primary and secondary containments are intact at both reactors. Temperature instruments in the spent fuel pools at reactors 5 and 6 are operational, and temperatures are being maintained at about 62 degrees Celsius. TEPCO is continuing efforts to restore power at reactor 5. Fukushima Daini All four reactors at the Fukushima Daini plant have reached cold shutdown conditions with normal cooling being maintained using residual heat removal systems. UPDATE AS OF 9:00 P.M. EDT, WEDNESDAY, MARCH 16: Crews began aerial water spraying operations from helicopters to cool reactor 3 at Fukushima Daiichi shortly before 9 p.m. EDT on Wednesday, March 16. The operation was planned for the previous day, but was postponed because of high radiation levels at the plant. News sources said temperatures at the reactor 3 were rising. Each helicopter is capable of releasing 7.5 tons of water. Spokesmen for TEPCO and Japan's regulatory agency, Nuclear and Industry Safety Agency, on March 17 Japan time refuted reports that there was a complete loss of cooling water in the used fuel pool at Fukushima Daiichi reactor 4. The spokesmen said the situation at reactor 4 has changed little during the day today and water remained in the fuel pool. However, both officials said that the reactor had not been inspected in recent hours. "We can't get inside to check, but we've been carefully watching the building's environs, and there has not been any particular problem," said TEPCO spokesman Hajime Motojuku. At about 7 p.m. EDT, NISA spokesman Takumi Koyamada said the temperature reading from the used fuel pool on Wednesday was 84 degrees Celsius and that no change had been reported since then. Typically, used uranium fuel rods are stored in deep water pools at temperatures of about 30 degrees Celsius. Recent radiation levels measured at the boundary of the Fukushima Daiichi plant have been dropping steadily over the past 12 hours, Japan's Nuclear and Industrial Safety Agency said on Wednesday night (U.S. time). At 4 a.m. EDT on Wednesday, a radiation level of 75 millirem per hour was recorded at the plant's main gate. At 4 p.m. EDT, the reading at one plant site gate was 34 millirem per hour. By comparison, the Nuclear Regulatory Commission's annual radiation dose limit for the public is 100 millirem. Radiation readings are being taken every 30 minutes. Japan's Chief Cabinet Secretary, Yukio Edano, said earlier today a radiation level of 33 millirem per hour was measured about 20 kilometers from the Fukushima Daiichi plant earlier this morning. He said that level does not pose an immediate health risk. Edano said that TEPCO has resumed efforts to spray water into the used fuel pool at the damaged reactor 4. TEPCO also continues efforts to restore offsite power to the plant, with up to 40 workers seeking to restore electricity to essential plant systems by Thursday morning, March 17. UPDATE AS OF 5:45 P.M. EDT, WEDNESDAY, MARCH 16: U.S. Nuclear Regulatory Commission Chairman Gregory Jaczko told members of Congress today that there is no water remaining in the fuel pool at reactor 4 at Fukushima Daiichi nuclear power plant. Jaczko told members of the House Energy and Commerce Committee that "we believe that secondary containment has been destroyed and there is no water in the spent fuel pool�radiation levels are extremely high, which could impact the ability to take corrective measures." There is no updated information available from either Tokyo Electric Power or Japanese safety or regulatory officials on the status of the Fukushima plant. Japan's Nuclear and Industrial Safety Agency said it also is concerned about the spent fuel storage pool at reactor 3 at the Fukushima Daiichi site. Also testifying before the House committee, Energy Secretary Steven Chu restated the administration's commitment to nuclear energy. "The American people should have full confidence that the United States has rigorous safety regulations in place to ensure that our nuclear power is generated safely and responsibly," Chu testified. "Information is still coming in about the events unfolding in Japan, but the administration is committed to learning from Japan's experience as we work to continue to strengthen America's nuclear industry. "Safety remains at the forefront of our effort to responsibly develop America's energy resources, and we will continue to incorporate best practices and lessons learned into that process." Chu said. "To meet our energy needs, the administration believes we must rely on a diverse set of energy sources, including renewables like wind and solar, natural gas, clean coal and nuclear power." The administration and Nuclear Regulatory Commission on Wednesday said that they believe it is appropriate for U.S. residents within 50 miles of the Fukushima reactors to evacuate. In response to nuclear emergencies, the NRC works with other U.S. agencies to monitor radioactive releases and predict their path. All the available information continues to indicate Hawaii, Alaska, the U.S. Territories and the U.S. West Coast are not expected to experience any harmful levels of radioactivity. UPDATE AS OF 4:30 P.M. EDT, WEDNESDAY, MARCH 16: Japanese authorities have reported concerns today about the condition of the used nuclear fuel pools at Fukushima Daiichi reactor 3 and reactor 4. Officials also are preparing to spray water into reactor 4 from ground positions and possibly later into reactor 3. Some debris on the ground from the March 14 explosion at reactor 3 may need to be removed before the spraying can begin. Most plants store used fuel in steel-lined, concrete vaults filled with water, which acts as a natural barrier for radiation from the used fuel. The water also keeps the fuel cool while the radiation decays-or becomes less radioactive. The water itself does not leave the used fuel pool. Used nuclear fuel at the Fukushima-Daiichi plant is stored in seven pools (one at each reactor and a shared pool) and in a dry container storage facility (containing nine casks.) The used fuel pools are designed so that the water in the pool cannot drain down as a result of damage to the piping or cooling systems. The pools do not have drains in the sides or the floor of the pool structure. The only way to rapidly drain down the pool is to have structural damage of the walls or the floor. For more information on used fuel pools, see our new fact sheet, "Used Nuclear Fuel Storage at the Fukushima Daiichi Nuclear Power Plant." The U.S. government on Wednesday recommended that Americans within 50 miles of the Fukushima Daiichi plant evacuate the area. The Nuclear Regulatory Commission has posted this news release on its website regarding the evacuation recommendation. The information contained in NRC's recent press release is new and industry is still evaluating the radiation dose calculations since there is little context for the numbers provided in the press release. On the surface, the estimated doses look to be extremely conservative, but we have no additional information on which to evaluate them. UPDATE AS OF 10:00 A.M. EDT, WEDNESDAY, MARCH 16: News reports that high radiation levels led to the evacuation of all workers from the Fukushima Daiichi nuclear power station are not accurate (emphasis added). Workers were evacuated for about an hour but returned to the site to continue efforts to restore safe conditions at the plant. Restoration of electrical power to the site was under way at the Daiichi plant as of 6:00 a.m. EDT Wednesday. A temporary cable was being connected between an off-site power line and Daiichi reactor 3. Off-site power has not been available at the site since the earthquake on March 11 Reactors 1, 2 and 3 at the plant are being cooled with seawater. There is some level of uranium fuel damage at all three units, and containment structure damage is suspected at reactor 2 Before the earthquake, reactor 4 had been in refueling and was completely defueled. Attempts to provide cooling water to the used fuel pool at reactor 4 by helicopter were not successful. Preparations are being made to inject water into the fuel storage pool using a high-capacity spray pump. There have been two fires inside the reactor containment building at reactor 4, but they have been extinguished. Although the reactor containment building at Unit 4 was damaged, the primary containment vessel remains intact At the Fukushima Daini site, all four reactors are safely shut down and cooling functions are being maintained.