Hot News Nuclear

Fukushima Nuclear Accident – 17 March update

The crisis at the Fukushima Daiichi nuclear power station is approaching a weeks’ duration. The on-site situation remains extremely serious, with glimmers of hope being shrouded by a shadow of deep uncertainty.

If you’ve not been following the situation on BraveNewClimate, and want to recap, please read these recent updates:

Japan Nuclear Situation – 14 March updates

Further technical information on Fukushima reactors

Fukushima Nuclear Accident – 15 March summary of situation

Fukushima Nuclear Accident – 16 March update

These are assumed knowledge for understanding the rest of this post. The preparation of the material below was aided greatly by the private advice of my acquaintances in the nuclear engineering field.

As predicted yesterday, attention over the last 24 hours has focused on the critical situation with the ponds used for temporary storage of spent nuclear fuel at the individual reactor units, before it is moved to a centralised facility on site. Although this old fuel has lost much of its original radioactivity, the decline is exponential (see this figure) which means that thermal energy must continue to be dissipated for months.

This figure shows the location of the spent fuel ponds:

The problem, as is explained in this updated fact sheet by the NEI, is that as these ponds heat, their deep covering of water (which acts as a radiation shield and a cooling mechanism), starts to evaporate. If they reach boiling point, because of lack of operational maintenance systems, the evaporation rate will accelerate. If exposed, the there is a potential for these old fuel rods and their zirconium cladding to melt, and radiation levels will rise considerably. The heat generated in spent fuel depends on a number of parameters, including: (1) level of build-up of fission products (burn-up) and (2) length of time after having been taken out of the reactor.

The spent fuel pool temperature has been rising gradually since last Friday due to the loss of cooling pump (presumably no power source). As we know from previous updates, the side of the Reactor 4 building has been lost (it’s the left-most of the 4 buildings in the following image):

The Unit 4 reactor was already shut off for periodic maintenance when the earthquake struck. IF the fire was caused by hydrogen,  its only plausible source would be spent fuel degrading in steam. Under this scenario, initial inventory was probably reduced by sloshing during the earthquake, and heat generation and resulting evaporation/boiling would thereafter be more than double that in other pools due to it containing freshly off loaded fuel. Temperature indications in the absence of water would be that of the mixture of steam and air in the location of the thermowell.

Nothing can be confirmed at this stage. As has been the case throughout this crisis, information is hard to come by and must be pieced together.

Are the spent fuel in the pools in Units 3 and 4 are now uncovered? TEPCO claims that NRC Chief Jaczko was wrong in claiming this, that the spent fuel pools in both Units 3 and 4 need some refilling but are NOT dry. (The Japanese authorities are apparently saying they’ve seen water still in the Unit 4 pool.) The big concern here is that unlike the releases from damaged fuel in the reactor cores of Units 1, 2, and 3, which were largely filtered by scrubbing in the containment suppression pools (wetwell torus), releases of volatile fission products (e.g., cesium and iodine) from these spent fuel pools have direct pathways to the environment, if they remain dry for an extended period.

Efforts to deliver water to these pools have proven to be very difficult, and fuel damage may be occurring.  If they are exposed, then the use of the evaporation of salt water as a heat sink over periods of more than a few days is not viable because the quantities of salt deposited as the water evaporates becomes large in volume and plugs the flow paths through the fuel, degrading heat removal. Everything that is cooled becomes a heat sink to condense anything volatilised. Unfortunately, a fresh water supply seems difficult to come by.

One option is to bring fresh water by helicopter, but the amounts needed imply a large number of flights and gamma radiation levels are high above the pools making overflights hazardous. NHK has reported a number of  successful water dumps using helicopters today. If radiation levels on the ground increase further, personnel access will become more challenging. Additional spent fuel is stored in pools in Units 5 and 6 and in a large centralized storage pool. A key issue is how to continue to make up water to these pools in the longer term, particularly if site access becomes more difficult.

It was announced at a press conference that a total of 11 specially-equipped vehicles will be used to spray water on the crippled reactors at Fukushima-1 after an access path is cleared using bulldozers. The big advantages of fire trucks over helicopters is that their water cannons can be better aimed, from the side rather than the top, and their operation is continuous rather than in batches so they can deliver vastly more water. It is clearly an appealing option. An additional 130 personnel have also been moved back on site to help with work.

Some additional key information from NEI:

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 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.

Based on the information coming out of TEPCO, it appears that units 1,2 and 3 remain critical but stable. Partial melting has almost certainly occurred in all three cores. There was definitely a period of no water injection because of a pressure buildup caused by stuck relief valve — always a potential issue for in high pressure systems. This figure illustrates the current state of play with the reactor units and spent fuel ponds:

The following is the latest status report, with timelines, from the Federation of Electric Power Companies of Japan (FEPC) Washington DC Office.


• Radiation Levels

o At 6:40AM (JST) on March 16, a radiation level of 400 milli sievert per hour was recorded outside the west side of the secondary containment building of the Unit 3 reactor at Fukushima Daiichi Nuclear Power Station.

 At 6:40AM on March 16, a radiation level of 100 milli sievert per hour was recorded outside the west side of the secondary containment building of the Unit 4 reactor at Fukushima Daiichi Nuclear Power Station.

o At 8:47AM on March 16, a radiation level of 150 milli sievert per hour was recorded outside the secondary containment building of Unit 2 reactor of Fukushima Daiichi Nuclear Power Station.

 At 8:47AM on March 16, a radiation level of 300 milli sievert per hour was recorded between the exteriors of the secondary containment buildings of Unit 2 reactor and Unit 3 reactor of Fukushima Daiichi Nuclear Power Station.

 At 8:47AM on March 16, a radiation level of 400 milli sievert per hour was recorded outside the secondary containment building of Unit 3 reactor of Fukushima Daiichi Nuclear Power Station.

 At 8:47AM on March 16, radiation level of 100 milli sievert per hour was recorded outside the secondary containment building of Unit 4 reactor of Fukushima Daiichi Nuclear Power Station.

o At 10:40AM on March 16, a radiation level of 10 milli sievert per hour was recorded at the main gate of the Fukushima Daiichi Nuclear Power Station.

o At 4:10PM on March 16, a radiation level of 1530 micro sievert per hour was recorded at the main gate of the Fukushima Daiichi Nuclear Power Station.

o For comparison, a human receives 2400 micro sievert per year from natural radiation in the form of sunlight, radon, and other sources. One chest CT scan generates 6900 micro sievert per scan.

• Fukushima Daiichi Unit 1 reactor

o At 6:55AM on March 16, the pressure inside the reactor core was measured at 0.17 MPa. The water level inside the reactor core was measured at 1.8 meters below the top of the fuel rods.

• Fukushima Daiichi Unit 2 reactor

o At 6:55AM on March 16, the pressure inside the reactor core was measured at 0.043 MPa. The water level inside the reactor core was measured at 1.4 meters below the top of the fuel rods.

• Fukushima Daiichi Unit 3 reactor

o At 8:37AM on March 16, white smoke was observed emanating from the vicinity of the secondary containment building.

o At 9:55AM on March 16, the pressure inside the reactor core was measured at 0.088 MPa. The water level inside the reactor core was measured at 1.9 meters below the top of the fuel rods.

o At 11:32AM on March 16, the Japanese government announced that the possibility of significant damage to the primary containment vessel was low.

• Fukushima Daiichi Unit 4 reactor

o At 4:08AM on March 15, the temperature of the spent fuel pool was measured at 183 degrees Fahrenheit.

o At 5:45AM on March 16, a fire occurred in the vicinity of the third floor of the secondary containment building.

o At 7:26AM on March 16, no flames or smoke was observed and thus it was concluded that the fire extinguished on its own accord.

• Fukushima Daiichi Unit 5 reactor

o At 4:00AM on March 16, the temperature of the spent fuel pool was measured at 141 degrees Fahrenheit.

• Fukushima Daiichi Unit 6 reactor

o At 4:00AM on March 16, the temperature of the spent fuel pool was measured at 137 degrees Fahrenheit.

• Rokkasho Reprocessing Plant and Accompanying Facilities

o As of 12:00PM on March 15, power generation of all facilities was restored to the commercial electricity grid from backup power generation systems. It was confirmed that no fire, damage to equipment, injuries to personnel occurred. Radiation levels were measured at a normal level of safety.


Further important information can be read at World Nuclear News, especially Problems for units 3 and 4 and Attempts to refill fuel ponds. Some key extracts:

The Japan Atomic Industry Forum reports that the level of water in unit 4’s fuel pond is low and damage to fuel stored there is suspected. Efforts are underway to refill the pool, including an abandoned attempt to douse the building with water from an army helicopter, hoping to get some to go through the damaged building. The temperature of the pond was last known to be 84ºC on 14 and 15 March, said the International Atomic Energy Agency. There was no data for today…

Efforts to cool the partially exposed cores of units 1, 2 and 3 continue. So long as radiological conditions allow, a team of workers pumps seawater into the reactor vessels. This boils away, raising steam pressure which must later be vented. Fuel assemblies are exposed by between one and two metres at the top, but the high thermal conductivity of the zirconium alloy rod casings helps cooling with just the lower portion of the rods submerged. This process is set to continue until the heat produced by the core has reduced so that the entire core can be covered.

The lack of recent temperature data may stem from a broken gauge. Please read the above WNN links for further details.

In sum, this accident is now significantly more severe than Three Mile Island in 1979.  It resulted from a unique combination of failures to plant systems caused by the tsunami, and the broad destruction of infrastructure for water and electricity supply which would normally be reestablished within a day or two following a reactor accident. My initial estimates of the extent of the problem, on March 12, did not anticipate the cascading problems that arose from the extended loss of externally sourced AC power to the site, and my prediction that ‘there is no credible risk of a serious accidenthas been proven quite wrong as a result. It remains to be seen whether my forecast on the possibility of containment breaches and the very low level of danger to the public as a result of this tragic chain of circumstances will be proven correct. For the sake of the people there, I sure hope it does stand the test of time.

By Barry Brook

Barry Brook is an ARC Laureate Fellow and Chair of Environmental Sustainability at the University of Tasmania. He researches global change, ecology and energy.

334 replies on “Fukushima Nuclear Accident – 17 March update”

I did learn something from all this. The word Fubuki which is Japensese for Blizzard. It would seem they were hit with a Fubuki of beyond design basis events for these units.


Red Blue I would tend to believe that Unit 4 pool with the full core offload is significantly low even if intact without makeup for this long. Unit 3 pool seems to be the focus though by the efforts…. which means something… reading between the lines it may be damaged and also leaking? Have to have on the ground real time information to make that kind of assessment though.

Based on unconfirmed information to date here or publicly there are issues with both pools affecting water level significantly….. I suspect both pools have structural leaks, extent yet defined.


“The concern with reactor 3 appears to stem from an explosion on Monday that is thought to have damaged the primary containment facility around the reactor’s core. If the storage pool at the reactor runs dry, radiation levels could soar so high that engineers cannot approach the reactor to try and bring it under control. David Lochbaum, a nuclear physicist for the Union of Concerned Scientists and a former Nuclear Regulatory Commission safety instructor, said the level of radiation beside the exposed rods would deliver a fatal dose in 16 seconds.

The frantic attempts to refill the leaking storage pool came as engineers installed a kilometre-long power cable to replace those destroyed in last Friday’s earthquake and reconnect the power plant to the grid. Engineers said the power supply would first provide electricity to reactor 2. Japan’s Nuclear and Industrial Safety Agency (Nisa) said three of the plant’s six reactors – numbers 1, 5 and 6 – were relatively stable.

The fresh power supply will be used to drive pumps that are needed at three of the reactors to circulate seawater and prevent their nuclear cores from going into meltdown. The water levels in all three reactors are dangerously low, exposing between 1.4m and 2.3m of the fuel rods, according to Nisa. The fuel rods should be covered with water at all times to prevent meltdown.

The UN nuclear watchdog said engineers were able to lay an external grid power cable to reactor 2 and would reconnect it “once the spraying of water on the unit 3 reactor building is completed”.


Red Blue, do you have technical knowledge of the Mark 1 Containment vent modification or subsequent BWR containment vent designs?

If the ultimate primary containment vent path is not directly to the stack it goes through Reactor Building ventilation in later designs standby gas (non operational in a blackout due to loss of ventilation fans).

Ventilation ducts leak…. without fans to provide dilution air due to station blackout….. hydrogen migrates to the upper elevations. It seems quite credible to me…


I know there is a lot of chaos right now but I thought I’d toss this in. Would it be viable to drag via robot or fly and drop via heli -hoses that are connected to pumps pulling water from a refillable pool outside the plant. Or drive the hose trucks up there with a long feeder hose from this refillable reservoir aim the stream and get out of there?


Shelby, do you have a solid report of a leaking fuel pool at 3. I knew they had a potential torus breach due to hydrogen explosion. Obviously they are concerned with vessel cooling based on that along with containment. Please link if you have any public data on actual fuel pool liner damage too.


Did the homework on the subsidence and thanks for the picture. Its probably me, but i fail to see where that would become a problem. Little if any point to make it survive more than the pond would, right? Still, do you know if the seawater thing is SOB? Thats really what i wanted to know.


I’ve found the gold star article (Free online at link) that others reference in regards to spent fuel pool dranage which is relevant since it seems the crticial issue now is what is happening with the spent fuel pools @ reactors 3 and 4.

Spent fuel heatup following loss of water during storage. [PWR; BWR]
Benjamin, A.S. ; McCloskey, D.J. ; Powers, D.A. ; Dupree, S.A.

It’s rather long so I’m reading it now, they have a lot of data and go through many scenarios since how long the fuel has been in the pool is of course a critical factor long with others. They seem to look at it all systematically.


Well I see my earlier comment seems to have survived here and thus must give credit where credit is due.

Still don’t seem to see much here on TedCo’s blacking out of level readings from around the plant, which is indeed being reported in the U.S. media. Is that in fact the case? And, to be fair, is there any good reason for same, esp. given that the immediate area already seems evacuated?


Although the NYT article is somewhat hyped, it is worse case as far as spent fuel cladding fire etc…

Where we are now in this event is the spent fuel pools through loss of level are now inhibiting critical access due to radiation levels to address the situation.

This could be another lessons learned from this event for the industry.


MOX fuel is not the issue in my opinion. No matter what fuel you load, you make plutonium through fission. The enemy is as it always was, decay heat and it’s removal….


A factual alternative to the media panic about the Japanese nuclear problems

Radiation released is no danger to public health. The fact that CNN, FoxNews and other TV broadcasters continue to promote fear is simply a drive for ratings, and should be ignored.

By Zbigniew Jaworowski, M.D., Ph.D., D. Sc. (He has been a member of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR)since 1973, and served as its chairman from 1980-1982.

Japan, perched on the so-called Pacific “Ring of Fire,” is one of the most seismically unstable countries. In the 20th Century, about 158,280 persons died there in nine major earthquakes, with Richter magnitude 6 and above. The Japanese had that in mind when building 55 nuclear reactors for 17 nuclear power plants, which supply the country with 34.5% of its electricity. They made them sturdy enough not to release any dangerous radioactivity outside the plant limits, even due to the worst earthquakes. The quake of March 11 2011, of magnitude 9.0, the greatest in the Japan history, proved that the plants operated almost as expected. No dangerous radioactivity was reported to escape from the destroyed Fukushima nuclear power plants into the environment outside the plants’ limits, and nobody was seriously harmed by radiation among the public.

However, even though the power plants evidently withstood the 9.0 magnitude earthquake, they appeared to be sensitive to the enormous tsunami, with the waves up to 7 meters high, which flooded their emergency diesel power generators, intended to provide back-up power for the pumps that cooled the reactor core. This was evidently an effect of the poor original design of the 40-year-old power plant, as the generators were located just behind a sea wall on low-lying coastal ground. The tsunami overwhelmed the 6-meter high barrier. The result was an overheating of the cores of the reactors. Like Chernobyl 25 years ago, Fukushima now brings important lessons for the only 56-years-old nuclear power.

In the heavily affected prefectures of Miyagi, Fukushima, and Ibaraki, there are 11 nuclear power reactors. Those which operated during the earthquake were automatically shut down when tremors started, and the crews started standard procedures of cooling the “residual heat,” i.e., pumping the water to the pressure vessels of the reactors. However, after an hour, the emergency power generators at Fukushima Daiichi plant were destroyed by the tsunami; the high pressure emergency cooling was lost, and before the mobile generators were supplied, the temperature of the core in the Unit 1 reactor increased to a level where the zirconium cladding of the fuel rods reacted with water, producing hydrogen gas. When the gas was released from the pressure vessel on 12 March, outside the primary containment, a hydrogen explosion occurred in the reactor building, outside the primary containment vessel, which remained intact. This technically aggravated situation injured several persons, but did not cause a large release of radioactivity to the environment. Cesium-137 and iodine-131 levels increased initially after the explosion, but these levels have been observed to lessen a few hours later.

On 14 March, this was repeated with an explosion at the Unit 3 reactor at the Fukushima Daiichi plant. The reactor building was destroyed, but again, the primary containment vessel remained intact and kept inside the radioactivity released from reactor fuel. And on 15th March at 6 a.m. local time, a third hydrogen explosion occurred inside the plant’s Unit 2 reactor. Pressure readings indicated that the reactor’s containment vessel may have been damaged.

In addition to these three hydrogen explosions in four days, radiation has also spread into the atmosphere from the spent fuel pond at the Unit 4 reactor at this plant. A dose of up to 400 mSv per hour has been reported from a single location between reactor 3 and 4; later this dropped to 11.9 mSv per hour, and after six hours, to 0.6 mSv. The fire was probably caused by a hydrogen explosion. As a precaution, the workers have been evacuated from the vicinity of this reactor. The fire was extinguished early on 15th March, and according to a spokesman for the Prime Minister, the fuel in the pond did not cause the fire.

All four reactors in the Fukushima Daini nuclear plant have now achieved cold shutdown, where coolant water is at less than 100oC, with full operation of the cooling system. Water levels are now stable in all four reactors and offsite power is available. According to Metropolitan Government’s Office in Charge of Health and Safety the radiation readings in Tokyo were by 11 a.m. on 15 March 0.147 microSv, i.e. at natural level. This was in agreement with the data reported by American 7th Fleet operating in the Tokyo area showing very low levels of airborne radiation.

Precautionary Measures

Several precautionary measures were taken by the authorities. More important among them were evacuation of about 200,000 residents of ten towns near the affected nuclear plants, and distribution of 230,000 units of stable iodine to evacuation centers from the area around the Fukushima Daiichi and Fukushima Daini nuclear power plants. The iodine has not been yet administered to residents, as this measure is not necessary.

The situation at the Fukushima nuclear plants is still unpredictable. However, one may imagine what would happen in the (rather improbable) case of a total reactor meltdown of all Fukushima Daiichi and Fukushima Daini power plants. We know what happened after a partial reactor meltdown in 1979 Three Mile Island event and a full meltdown in the 1986 Chernobyl catastrophe. In Japan, the result would be probably similar as in the Three Mile Island power plant accident, where the reactor was protected by a thick concrete containment which efficiently retained fission products: There was almost no emission of radionuclides into the atmosphere, except innocuous radioactive noble gases, and practically zero radiation exposure of population.

There is a zero possibility of repeating in Japan the scenario from the Chernobyl nuclear power plant. The Chernobyl plant, an engineering pathology – a hybrid of a military plutonium factory and a power station, was not fitted with a containment vessel, and for ten days the radioactivity was freely escaping from the melted reactor, roasting in the burning graphite used for its construction. But even if by a magic miracle the containments of the Japanese plants perished completely in the quake or tsunami, the residents around them would not be harmed by radiation.

This is what we learned from the Chernobyl disaster, in which not a single person died among the affected populations of Ukraine, Belarus, and Russia, as according to a recent report of United Nations Scientific Committee on the Effects of Atomic Radiation, a body most authoritative in radiation matters (UNSCEAR 2011), the radiation doses from Chernobyl fallout (of about 1 mSv per year) were below the natural radiation, too small to produce any effect. Even after ten times higher doses, the result would be the same.

See: UNSCEAR. 2011. Sources and Effects of Ionizing Radiation. Vol. II. Annex D. “Health effects due to radiation from the Chernobyl accident”, pp. 1-173. United Nations


> American
redo that with “TEPCO” — still can’t support your reading; I’d bet you searched on the typo, or were seeing referrals to the electrical power rolling blackouts. If you do have a source for what you say you found, please post it and why you think it reliable if it’s second hand.

> Pool wall/liner
Apparently someone’s interpretation from that helicopter overflight; does the cooling pool share a common wall with the outside of the building at any point? As I read this I think it probably means:
——- begin interpretation by me ———-
The _building_ _outside_ _wall_ collapsed (as we know) and the pool is not visible from the helicopter; no flood of water was observed, so by inference the steel liner is intact — even IF the concrete around it is damaged.
——– end interpretation —-

The original text I’m trying to interpret is:

“TEPCO officials say that although one side of the concrete wall of the reactor 4 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;


Is it possible for TEPCO to have used SF Pool water for emergency reactor cooling. It seems to me they would been reluctant in the early stages to use sea water in the pressure vessel. Just a thought.

The IRSN French post did compute 4 days to uncover the fuel in the No 4 pool. So maybe vaporization is enough by itself, as would be major crack/leaks.


I know of no other current alternatives and the following is based on my knowledge only. I could be wrong….

You have to move exposed fuel under water from the core to the spent fuel pool. Due to radiation shielding etc.

Current guidelines in the US require that it must stay there for 5 years for radioactive decay under water before it can be safely loaded into dry inerted fuel canisters for land based, called dry fuel storage.

There is alot of things involved with land based dry storage that I will omit here as they are not relevent to the current situation….

Bottom line is dry fuel storage of bundles less than 5 years is not approved or analyzed…. in the US at least. Which is equivalent to the issue we are seeing with loss of fuel pool levels in a laymens terms.


Thanks hank, I hope what you reported is true. I read it as the concrete walls are damaged, Spent Fuel Pool liner questionable but visable level observed… Correct me if I am wrong….
I have struggled all day with media reports that level was lost in unit 4 spent fuel pool, the one with the full core offload…. I hope your report is correct…


So the CH-47 air drops aren’t doing it. Not least because they’re dropping from comically ineffectual altitudes.

Let’s brainstorm a bit.

Build a large rectangular frame of metal pipe dotted with nozzles. Any good industrial supply house would have everything you would need.

Place numerous nozzle crossbars within the frame. Plumb it for a fire hose connection.

Trained men could do this in a single afternoon: pipefitters, machinists, welders, any of these disciplines could handle the rather simple assembly job. If it leaks a bit, no one will care.

Attach a long hose to the nozzle frame from one of the onsite fire engines.

Use a CH-47 to carry the nozzle frame, dry, trailing the hose, to the top of a reactor building. Drop it on top. Precise positioning and close approach not required.

You may also want to trail some long steel cables from the nozzle frame. These could be secured by vehicles on the ground in order to tug the frame back and forth, and to secure it in place once the hose fills and becomes heavy.

Turn on the water from the fire engine.

This should flood the entire rooftop.

Most of the water will presumably be lost down the sides of the building (inter alia carrying some fission products down to ground level).

But if you have a high enough density of nozzles per square meter of roof, you will end up putting some of that water effectually into the interior and presumably into the spent fuel pool.

This scheme only exposes the helo crew to roof proximity once. And it does not rely on offsite grid power showing up.

Plus it provides continuous delivery of water to compensate for ongoing boiloff and leakage, unlike the previous air drop scheme.


Joe, there are no accicent managment strategies I know of that tell you to add water via lowering the spent fuel pool to a BWR containment or vessel. That’s all I can add on that and it’s doubtful that any knowlegable operator would consider that as a success path …


>Hank Roberts, on 18 March 2011 at 2:13 AM said:
>Their seawall was sized to protect them from the >“potential tsunami” — reality exceeded design spec.

That’s potentially forgivable. But putting power circuits that are critical to operation below ground so near the ocean… Seems fishy. Even if you don’t suspect a Tsunami will breach your wall, it’s still below ground, a significant flood could cause problems. Perhaps there are reasons I’m not aware of to do this. Seems like you’d put your backups above the tsunami wall though, just in case.


Jeremy there will be lessons learned from this event about the importance of water intrusion below ground level before this is over. Either from flooding or tsunami…. Hardened structures are no good if there are leaks allowing water intrusion….


>Hank Roberts
My experience with concrete is that it doesn’t ‘collapse’, meaning if it is partially no longer there, it must have been blown out by explosive force. The odds of the steel liner surviving a blast strong enough to rip a hole in the concrete are slim to my estimation. The idea of the combination of concrete and steel liner it merely to ensure that a crack in the concrete does not result in a leak. Its like blowing a hole in a brick wall and leave the wallpaper intact. Its a liner, the literal meaning of the quote doesn’t make sense.


Hank Roberts:

Yes, USA Today newspapers is saying that here:

Oddly they did not attribute this alleged news even to any unnamed source, but did then talk about some U.S. guy complaining about a general lack of info coming from the Japanese. Not good reporting, for sure, but it’s a little much to expect footnotes to every statement given the nature of the situation, no?

For what it’s worth some other reporting I found interesting:

It is said there’s kind of a disagreement between the Japanese on the one hand and the U.S. and the Brits on the other concerning the Japanese claimed primary focus on the storage pool at #3, and the other countries saying that no, the concentration ought to be on the pool at #4 which they believe is either dry or terribly low.

Further interesting then is the report from an Atlanta paper saying that TepCo has “moved closer” to agreeing with the assessment that water in #4 is low if not gone:

From the paper: “‘Considering the amount of radiation released in the area, the fuel rods are more likely to be exposed than to be covered,’ Yuichi Sato [from TepCo] said.”

One question that may have been discussed here that I may have missed: Aren’t lots if not all of the proposed solutions to the holding tank problems assuming that the tanks are indeed still intact? (And thus can still hold significant water at all?) So, anyone have any idea of how good that assumption is?

Wonder if that has any relation to the news that GB seems to be shipping tons and tons of boron over.


From ParetoJ’s post at 7:16 AM, the document

“Spent fuel heatup following loss of water during storage. [PWR; BWR] Benjamin, A.S. ; McCloskey, D.J. ; Powers, D.A. ; Dupree, S.A.

indicates that the typical thickness of the SS liner is 1/4″. Collapse of a concrete wall during explosion could well tear a liner this thick at attachment points.

Importantly, reading the documents introduction & conclusion section seems to indicate that there is a “decay time” of 5 to 150 days after the BWR fuel assemblies are put in the spent fuel pond, after which the fuel assemblies do not reach the critical 850-950C following a complete water drain.

Would somebody else please read and verify my interpretation.


What are the chances of the pool itself being leaky ? What is it constructed out of – afterall there were explosions …


That was an interesting read, ParetoJ.

It seems that natural air convection is enough to keep the fuel from melting. I wonder if the guidlines for improving cooling in partial drainage were followed as a completely dry pool was said to be better than a partially filled pool.

Though they did talk about spraying the fuel as being highly effective and a rate of about 100 gallons per minute (tiny!) asuming 70% spray efficiency was enough to keep temps under 500C.

As long as the fuel hasn’t fallen into a critical configuration there really shouldn’t be any problems other than the massive unshielded radiation. ie things shoudln’t get worse.


> bchtd1parrot

I agree, the literal text we see doesn’t make sense.

> em1ss
You’re reading me right, and that is just my guess, from reading the English original and — stand back, I’m attempting to use logic — I don’t see a wall that’s common to both the outside and the tank.

There must be little spy helicopters on the US Navy ships if not in the Japanese police and military — someone should be trying to get a better view in here.

I have the sad thought that the agencies are always reluctant to publicly reveal how good their imagery can be — remember this confusion:

But if there’s a tool out there that can buzz in an open window and photograph what’s on someone’s desk (I’m making this up, people, not disclosing something, just wishful thinking) — if there is anything like that, it should be used.

Briefing on the Fukushima Nuclear Emergency (17 March 14:00 UTC)

“… Radiation Monitoring

We are now receiving dose rate information from 47 Japanese cities regularly. This is a positive development. In Tokyo, there has been no significant change in radiation levels since yesterday. They remain well below levels which are dangerous to human health.

As far as on-site radiation levels at the Fukushima Daiichi and Daini nuclear power plants are concerned, we have received no new information since the last report.

In some locations at around 30km from the Fukushima plant, the dose rates rose significantly in the last 24 hours (in one location from 80 to 170 microsievert per hour and in another from 26 to 95 microsievert per hour). But this was not the case at all locations at this distance from the plants.

Dose rates to the north-west of the nuclear power plants, were observed in the range 3 to 170 microsievert per hour, with the higher levels observed around 30 km from the plant.

Dose rates in other directions are in the 1 to 5 microsievert per hour range…..”


Emergency Diesel Generator (1 unit) for Unit 6 operable. Supplying
electricity to Unit 5 and 6. Water injection to Spent Fuel Pool through
the Make up Water Condensate System (MUWC) progressing. Schedule
to inject water to the Reactor Pressure Vessel (RPV) after the recovery of
external power source.

Click to access en20110318-1.pdf


My understanding was that they were concentrating on SNP #3 because it was open at the top, and not on #4 because most of the roof is still there. The roof obviously gets in the way of dropping water from above.

Is this not correct? Is the roof no longer over the SNP of #4 ?


Hank… “But if there’s a tool out there that can buzz in an open window and photograph what’s on someone’s desk (I’m making this up, people, not disclosing something, just wishful thinking) — if there is anything like that, it should be used.”

There is, certainly in prototype…


Importantly, reading the documents introduction & conclusion section seems to indicate that there is a “decay time” of 5 to 150 days after the BWR fuel assemblies are put in the spent fuel pond, after which the fuel assemblies do not reach the critical 850-950C following a complete water drain.
Would somebody else please read and verify my interpretation.

Unfortunately Unit 4 pool’s fuel is not “spent”. The fuel was waiting for reinsertion into the core following maintenance.


I do not understand how a hydrogen explosion blew out a concrete wall in the spent fuel pond. That sounds more like you would need high explosives. The sheet metal of the building around all this mess, sure, but not concrete. Could the tsunami have undercut the wall? Don’t know enough about the layout, but that doesn’t seem that possible either. The concrete wall that has colapsed may not be the SFP wall. The building wall? That would not be as thick.


BBC is reporting Unit 4 cooling pool as empty, but it’s not clear on what basis. “Official confusion” … “too radioactive to check” … “an American drone flying over … concluding it was now empty … extremely dangerous …”


@Jason: To the extent that reactor 4’s fuel assemblies are not fully”spent” or may have some fresh rods, isn’t that a good thing? I thought the fuel assembly heat was generated more by radioactive decay of fission byproducts instead of the U235. Am I right?


I’ve seen some pretty unimaginal pictures of destruction from around Japan including an obliterated sea wall…just saying.


Jason, on 18 March 2011 at 8:29 AM said:
“Unfortunately Unit 4 pool’s fuel is not “spent”. The fuel was waiting for reinsertion into the core following maintenance.”

Is this fresh fuel or partly burnt fuel? If fresh there would be no fission products, you could pick it up in your hand. Even if partially burnt the radionuclide load would be much less than fully burnt which would be good. There may be a mixture of fuel waiting to go in and spent fuel from the last unloading. Maybe this is where the confussion is.


Can’t they use some kind of thermal imaging camera to figure out what is going on in fuel pools without getting too close?


@Steven Moss
There is at least something between open air and the structure at nr4. On Sat pics this is clearly visable. The units number sequence seen from sea is 432165 with only the roof of unit 2 intact day before yesterday.

Putting a camera on a buzzer of some sort is no problem. Its the controling of it so close to so much radiation thats challenging. Otherwise it would have been done already. It takes one trip to a radio shack and a toystore to get what it takes.
@Geoff Russell
170mSv at 30 miles. Where would that put the reading at the plant? If that reading is true it would support the story on the empty pool, but it would make any human presence on the site itself impossible.


One thing I don’t think they should have done is throw buckets of salt water at the reactor. Unlikely to get much in the SPF and from that height you may destroy more required infrastructure from kinetic impact and now you have radioactive water running who knows where. They didn’t do this that much before they tried the firehoses. Why did they bother?

On the same topic. Is there no way to get to the heat exchangers or pumps for the SPF and pore water in there. I believe all that infrastructure is above the top of the pool. Gravity would do the rest of the work. I assume it is just too radioactive there as well.


Now we get the recognition:

…my prediction that ‘there is no credible risk of a serious accident‘ has been proven quite wrong as a result.

[unsubstantiated personal opinion deleted]

Now we must consider the flow of information.

If at 6:55 on 16 march the water level inside the reactor cores of units 1, 2, and 3 were all at least 1.4 metres below the top of the fuel rods, when was this information provided by TECO, the Japanese government or IAEA?

Anyway, it is all over now, I suppose the only useful thing we wait for now is news that power has been connected to all pumps and all pumps and pipes are functioning.

Notice too, how we get reports of radiation readings but never accompanied with wind direction. Off course you will get low readings by moving your monitoring west, if the breeze blows east.

Again the access to, and flow of, information is the key determinate and one of the key reasons (along with commercial competitive pressures) this form of energy production must be closed down.
[unsubstantiated personal opinon deleted]


Any chance of presenting the radiation numbers as a graph Barry? I know you’re busy as a busy thing, but reading that list gives me a headache.


Hasn’t it already been said that a complete unloading of core #4 was done Nov. 30? That means some or all of the fuel is not spent — had been destined to go back in, after spring inspections were done — and all of it has been irradiated. None is new. If it were, as above said, it would not be part of the problem at all. Indeed, they wouldn’t keep it in the SFP.


A quick scan of the Morse paper suggests the dose rate should allow someone to quickly advance a fire hose into the pool if they crouch down and don’t get too close. Ergo, there are other, extreme sources of radioactivity en route to the SFP besides (potentially) exposed fuel rods.


@William Fairholm,
@Leo Hansen

Good questions about the specific Unit 4 fuel load.

I’m sorry I can’t find the post with the specific link to unit 4’s fuel load, the comments here have grown unwieldy. Other posters have been repeating this information and basing calculations on it.

I’m sorry if i’m repeating inaccurate information. Moderators feel free to delete my original post if inaccurate.


@bchtd1parrot, on 18 March 2011 at 9:00 AM said:

>170mSv at 30 miles. Where would that put the reading at the plant?

The units are uSv/h.

It’s a mountainous region. Some areas will be like wind tunnels.


harrywr2, on 18 March 2011 at 9:24 AM said:
“@bchtd1parrot, on 18 March 2011 at 9:00 AM said:

>170mSv at 30 miles. Where would that put the reading at the plant?

The units are uSv/h.

It’s a mountainous region. Some areas will be like wind tunnels.”

Any radioactive plumes from the reactor are going to come down in a very patchy manner, depending on wind patterns, local geography and precipitation. A few hundred meters could make quite a difference. That is why I take all these radiation measurements with a grain of salt. They are spot measurements and may or may not give some idea of the average contamination in an area. They will have to eventually do a detailed survey of the radiation pattern. Not going to happen any time soon.


I think that anyone observing the events of the past six days would have to acknowledge that the design assumptions and technology involved are never the sum total of what makes a catastrophic accident. There are people, institutions, culture, and circumstances, which all factor in; human frailty should be accounted for in the design.

Clearly, there is weak independent oversight over Tepco — just observe the government’s frustration with the company’s almost total lack of candor.
Second, there is the Tepco culture, clearly one of secrecy, non-disclosure, and closed doors. In 2002, Tepco suffered a system-wide shutdown (17 plants) , according to Wikipedia:
“TEPCO was guilty of false reporting in routine governmental inspection of its nuclear plants and systematic concealment of plant safety incidents. All seventeen of its boiling-water reactors were shut down for inspection as a result….. The utility “eventually admitted to two hundred occasions over more than two decades between 1977 and 2002, involving the submission of false technical data to authorities”

Regular deception over a quarter of a century. You don’t cure that merely by firing executives. In 2005, Tepco disclosed more false reporting. The 17 plants in question were closed for three years.

In 2007, ” a severe earthquake (measuring 6.8 on the Richter scale) hit the region where Tokyo Electric’s Kashiwazaki-Kariwa Nuclear Power Plant …and radioactive water spilled into the Sea of Japan; as of March 2009, all of the reactors remain shut down for damage verification and repairs; the plant with seven units was the largest single nuclear power station in the world.[8]”

According to the Wikipedia article I got this from there seems to have been another earthquake generated incident, to a cooling tower, in 2008, but there was no additional info on where it was. Bottom line: no one can claim that such events — earthquakes impacting NPPs — are unexpected in Japan.

[unsubstantiated personal opinion deleted]
Another thing: what does it matter if these reactors are nearing the end of their design lives? So what? Do you think their licenses would not have been renewed had they not self-imploded? Has their safety not been upgraded over the 30+ years they have been in operation to meet growing knowledge and understanding of what is needed? Do you suggest that regulators would let them continue if they were not safe? In the US, most reactors that have reached the end of their 40 year licenses have had them renewed for another 20 years, and no doubt, if they are proved worthy, they will be renewed again. Saying that the future of nuclear safety is in new designs is nonsense — we have 100 of the old designs, and they are the only reactors we are certain to have in 20 years, and not one of the new plants that has been propsoed will replace them. To suggest otherwise is dishonest.

This is not a time where any kind of hubris looks good. To suggest that it was unreasonable to plan for a 9.0 earthquake is hubris. How long have we measured earthquakes? How long have they happened? What is the frequency of big ones? Do we know whether smaller ones (the 2007 one was “only” 6.8) can do more damage. Damage in earthquakes is very catch as catch can, depending on many factors, and what falls and doesn’t is due to a lot of factors, the most significant being that we cannot predict with any accuracy where an earthquake will strike, forget about when.

I love the info you have provided, but find the defensiveness of many commenters detrimental to understanding theis unprecedented accident (multiple meltdowns), which ironically helping to explain the incompetence of Tepco to manage a disaster of this magnitude, a disaster which has cost them three or four reactors. All we know is what they tell us, and when they tell us that there was a loud noise and a bang while we watch a building blowing up, their credibility sinks to new lows.

I hope it doesn’t get worse, mostly for the sake of the people whose health long- and short-term will be impacted by human decisions over which they had no control or input. But if we have seen the worst already, can the promoters hold off on braying about how everything came out ok?


Get these 50 workers some gasoline driven pumps ASFP from the steel mills to the south and stop pissing around with these chopper drops !!!


Interesting to learn that the US has been overflying the Fukushima plant with an “Aerial Measuring System.” I guess because the key isotopes emit photons of fairly distinct peak energy, this device overlay the emissions data on an aerial photograph and map each isotope. Given a known altitude from the flight instruments, they can even get a semi-quantitative assessment of Ci amounts.


@William Fairholm,

>>hey will have to eventually do a detailed survey of >>the radiation pattern.

Already being done. The US is doing aerial radiation assessments. The imagery should already be in the hands of the appropriate Japanese ministries.


Thanks for admitting that you were wrong previously. That takes courage and really helps with credibility. You are a far better source than all the folks who are simply saying that everything is okay.


I read at kyodo news that power lines are prepared to bring power to the pumps at the reactor 3.
Can anyone have more actual data about this?
Seems to me that this is the only solution that can calm down that monsters.


Madisonian suggests that someone crawling quickly and low enough could get a firehose close enough to the reactor. Rather you than me!

I’m much more curious why no robots have been used? I understand the lack of power could be a problem, but.. still, this doesn’t seem to be too hard! If Mythbusters can convert a full sized car into remote control then surely the Japanese can so that and strap a firehose to the roof?


If the ultimate primary containment vent path is not directly to the stack it goes through Reactor Building ventilation in later designs standby gas (non operational in a blackout due to loss of ventilation fans).

The normal secondary containment (reactor building) air circulation system has inlet filters, and exhaus processing flow which normally requires grid or emergency bus power for the fans and heaters, as well as and some particulate filters, then the stack.

I don’t believe you need the exhaust fans in a situation where high pressure steam and hydrogen is vented from pressurized primary containment directly to this exhaust filtration plant. The most important function would be the particulate and active carbon filters to screen the steam/hydrogen and those don’t require power. I guess without the dryer you would get some damage from steam though eventually.

The valves in the containment vent lines should work from the battery bus on control room command, like the valves of the vent lines to secondary containment, but there are obviously some other valves before the stack that might be on other buses. However, all of them should be operable with pressurised air or as the final backup by turning a wheel manually.

Just as a comparison, in most European plants this functionality of secondary containment overpressure protection is achieved by overpressure disk valves (that open automatically and then stay open until replaced) and a filtration system before the stack which is spesifically designed to handle high pressure steam, requiring no controlled valve operation whatsoever.

I don’t think anyone except TEPCO know exactly how the modification was implemented in Japan, but I have read some recent US reports (probably coming from GE) that they did implement it somehow.


There is an important difference between the two problem areas in these nuclear power plants.

The radioactivity from the reactor core is from the release of steam containing gaseous fission products and particles from the primary containment. The primary containment concrete provides shielding from direct gamma radiation from the fuel assemblies in the core.

The water in the spent fuel ponds within the secondary containment provides cooling and shielding. The bottom and walls of the ponds are part of the concrete section of the containment but the top is open. As the water level in the ponds falls, as well as reduced cooling, the shielding is reduced. The concrete bottom and walls will prevent gamma radiation towards the reactor area but there will be a direct shine path of gamma radiation upwards. This is probably the main contribution to the high radiation levels above the reactors detected by the helicopters.

Dose rates decrease proportionally to the square of the distance (inverse square law) .

My estimates of the number of fuel assemblies in the reactor SF ponds, based on Te figures and ~ 170kg U in BWR FA;

Unit 1 – 294
Unit 2 – 581
Unit 3 – 523
Unit 4 – 756
Unit 5 – 872
Unit 6 – 1503

With an estimate of 6291 in the common poll and 408 in dry casks this gives a total of 11,229 – close to the recent figure of 11,195 stored on site.

The unit 4 includes the 548 FA full core unload during the current Unit 4 maintenance. This will have a range of burnup from 1-3 years.
In common with many power plants, SF capacity is nearing full (common pool capacity 6840 FA), therefore more SF have to be stored in the reactor SF ponds – not just the last few unloads.
There will be a time limit for decay before SF is transported from the reactor SF pool to the common fuel because of transport cask limitations.
Fuel weight is normally given in TeHM – heavy metal – ie the uranium content.


There is now some interesting additional information available:

Reactor 1 has last refueled 357 days ago (I believe that’s the day of last criticality of the hottest fuel in the SFP)
Reactor 2 has last refueled 182 days ago
Reactor 3 has last refueled 268 days ago (34 MOX assemblies then added)
Reactor 4 was last refueled 107 days ago (entire core in the pool)
No data about reactor 5 and 6 refuelings, but pool temperatures around 60 C and can take more week from today without boiling even if no water added (and the water that is there is being cooled with diesel backup power, just that no water has been added)


duh, still trying to master inserting graphics here

NCRP data (National Council on Radiation Protection, set up by Congress to gather and provide radiation data to the public, etc.)

Average American’s exposure to radiation, including background, medical, occupational, the works, 1980s

360 millirem

Average, all sources, by 2009

620 millirem

Almost 1/2 of which, i.e. 300 millirem is medical imaging. Medical imaging increases so fast NCRP has announced it now exceeds 1/2 of all exposure, i.e. it more than equals what used to be called normal background on average.

NCRP was displaying a report I think it was Massachusetts indicating around 100 millirem of the 300 millirem that is medical was “defensive medicine”.

We’re glowing in the dark because our doctors are afraid of our lawyers.

Well, not actually, these are low levels, but it alarms the NCRP that they are rising so quickly. Prehistoric humans would have gotten close to the dose we got in the 1980s.

Consider that 100 millirem that has been added unnecessarily to the received average dose of the entire US population due to defensive medicine when the dose rates start being announced for whatever someone says you are exposed to. Call for getting rid of the lawyers, keep the doctors and nuclear power.

Someone who says a plume coming from Japan that makes it over the US causes some cancer will have to admit that flying to Copenhagen to attend that climate conference also causes cancer by the same reasoning, i.e. you get a dose up there in a plane, said to be in the 2 to 5 millirem range, said to be 1/2 a chest xray per transcontinental flight.

And saying experts have trouble finding the cases and come up with calculated numbers of cases may even be proven to have been a wrong idea one day. A lab is said to be going into a very low radiation area where a guy Gomez is looking for answers.


This is for Barry if he is awake or when he gets up. In the link

you claim that they are not injecting salt water into the reactor pressure vessel and the primary heat transport system and I think your source is TEPCO. However, when I look at the JAIF pdf on reactor status

Click to access ENGNEWS01_1300368041P.pdf

it says they are continuing to inject seawater into the Core AND the Containment Vessel. What am I missing here? What is the Core, but the pressure vessel? And if they are not putting seawater into the pressure vessel where is the makeup water coming from as the water in there is turning to steam and being periodically vented?

If you have a explaination, please provide it.


William, this is actually Luke’s claim (he was the author of this article). I think you are right, it is my understanding that they have been injecting salt water into the reactor vessel itself due to a chronic lack of onsite fresh water. This also explains the use of the boric acid, as a neutron poison and heat dissipater.


Importantly, reading the documents introduction & conclusion section seems to indicate that there is a “decay time” of 5 to 150 days after the BWR fuel assemblies are put in the spent fuel pond, after which the fuel assemblies do not reach the critical 850-950C following a complete water drain.

Would somebody else please read and verify my interpretation.

There is some delay of several days after a shutdown before the unloading operation starts, but probably never 150 days for scheduled reloading, instead of stop for maintenance issues and the expedited reloading as a result.

Also, I think the concern of Alvarez, Lochbaum et all is that since the NRC studies about this in the 1990s, the packing densities and used capacity in SFPs have gone up, excarberating the problem.

I think this may be relevant to the Fukushima situation because TEPCO had to build a secondary wet storage facility because they couldn’t get spent fuel to dry storage or to reprocessing fast enough. So even without exact knowledge of how many and how old rods they have in those pools, evidence points more to the direction of more than the NRC 1997 numbers would assume for a typical BWR/3/4 plant.


Luke Weston wrote:

The level of water in the used fuel pool is normally 16 feet above the top of the fuel assemblies. With the water level evaporating at the rate described above, the water level will drop by 2 feet per day.

Uncovery of the fuel assemblies will take eight days. (Beginning from the point where the water level reached boiling point, after active cooling ceased.)

(Working assumption which you may subject to some skepticism: That there is no form of leakage or other water loss pathway from the used fuel pool.)

Additional assumption: the spent fuel pool didn’t lose a significant amount of water due to sloshing during the quake. I note this from the NYT article:

Mr. Lahey said that much of the water may have sloshed out during the earthquake. Much smaller earthquakes in California have produced heavy water losses from sloshing at storage pools there, partly because the pools are located high in reactor buildings.

“It’s like being at the top of a flagpole, and once you start ground motion, you can easily slosh it,” he said.


I know one probably could have gathered this from all the previous tech talk here, but while I gather that “radiation” is measured in some consistent way I also know that there’s different kinds of radiation, and that gamma rays especially are very bad, right?

So anyway I then read this from a Guardian (U.K.) paper concerning those holding ponds:

“Richard Wakeford, an expert in epidemiology and radiation at Manchester University’s Dalton nuclear institute. ‘If the water goes you’ve got no shielding and it’s like having a great gamma-ray searchlight shining into the sky and that is presumably what the helicopters are seeing.'”

So, for instance, are all “millisieverts” or whatever just … “millisieverts” so that all are equally dangerous? Or are there “non-gamma-ray” millisieverts and then “gamma-ray” millisieverts, so that the latter are much worse than the former?

Even just articulating it I guess it seems a dumb question because it would seem dumb for them to mean different things, but, still, I’ll ask.


Sorry, had things to attend to but will try and answer a couple questions based on knowledge and experience, not necessary specific design facts of the multiple units involved ….

First, adding any kind of water is a strategy in an accident like this…. When normal clean makeup is unavailable.

Second, I believe the thickness of the concrete and the steel liner of the typical spent fuel pool is about as hardened as it gets, inside the secondary containment structure called the reactor building.

I also don’t believe the hydrogen generated and that collected there was from the spent fuel pool proper. It was from primary containment venting operations…. Meaning the pool was initially full and cool when the events occurred. This is supported by how many days we are into this event without makeup or cooling to the pool….

Decay heat eventually wins though in the core or the pool….

Based only on knowledge of the typical designs, level the fuel pool would at most leak, not completely fail due to the hydrogen explosion.

This is based on failure of alot more less hardened walls at that elevation of the typical design as seen in the photos. Essentially blow out and failure of the weakest saves the strongest.

There is a significant thickness (approximately 5 feet) of concrete around that steel liner for the pool. A lot less for many of the building walls, especially at the refueling floor elevation…

Keep on pumping water and try to make up to those pools…. Radiation levels should drop allowing access to determine the next strategy.


So, points to Mr. Lahey for knowing what to look up, and knowing what actually happens

He also says:
Richard T. Lahey Jr., a retired nuclear engineer who oversaw General Electric’s safety research in the early 1970s for the kind of nuclear reactors used in Fukushima, said that the zirconium cladding on the fuel rods could burst into flames if exposed to air for hours when a storage pool lost its water.

Zirconium, once ignited, burns extremely hot and is difficult to extinguish, added Mr. Lahey, who helped write a classified report for the United States government several years ago on the vulnerabilities of storage pools at American nuclear reactors.

That report has been much mentioned and its existence discussed but apparently the content is still classified


Do we know which ” spent fuel pools” contain plutonium? Does this pose more of a danger than the uranium fuel rods since it has a lower melting point (641 deg C) than Uranium?


There is more than one kind of science, probability and chance are not the same thing. People do actually win the lottery despite the probability even the the smallest chance can eventuate.


Gavin, all exposed fuel contains plutonium. Some Plutonium is generated by fission of uranium always. See the fission yield process and curves….


American: my understanding is that the millisieverts reflect alpha, beta and gamma rays as absorbed by the body – i’d like to know how the mixture is calculated from fallout or if it can be. anyone know?


What is the absolutely worst case possible scenario? Why is it so bad to discuss that subject? Because people are afraid. Fear can motivate us to save our lives. If the fear of tsunami was greater this may not be happening. Randomness and anarchy are a part of nature and we are not apart from nature.


…I think the concern of Alvarez, Lochbaum et all is that since the NRC studies about this in the 1990s, the packing densities and used capacity in SFPs have gone up, excarberating the problem.

The anti nukes, i.e. Nader vowed to “constipate” the nuclear industry by finding a way to demonize waste repositories to stop creation of them or delay. This resulted in increased packing densities in the SFPs in the US. I’m not sure what’s happening in Japan.


That report has been much mentioned and its existence discussed but apparently the content is still classified

That report which Lahey indeed did help write is available online Its an online searchable and readable thing, not a pdf you can download.

Quoting from itt: “This report is based on a classified report that was developed at the request of the U.S. Congress with sponsorship from the Nuclear Regulatory Commission and the Department of Homeland … . This report contains all of the findings and recommendations that appear in the classified report. Some have been slightly reworded and other sensitive information that might allow terrorists to exploit potential vulnerabilities has been … security. Nevertheless, the National Research Council and the authoring committee believe that this report provides an accurate summary of the classified report, including its findings and recommendations…”


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