Jeffrey LewisFEPC Statement on Fukushima

Am pleased to be back in the US, safe and sound with my family. (Note to reporters: Stop sounding disappointed; it pisses me off.)

The Federation of Electric Power Companies of Japan (FEPC) — which arranged for my trip — has released a detailed statement that provides basic timeline of what has happened at the Fuskushima nuclear reactor site and the efforts to prevent a contain the damage.

I applaud the heroic efforts of the workers at the site, four of whom were injured in the explosion.

Follow the jump for the full-text.

Information Sheet Regarding the Tohoku Earthquake
The Federation of Electric Power Companies of Japan (FEPC) Washington DC Office
As of 4:30PM (EST), March 13, 2011

At 2:46PM (JST) on March 11, 2011, a 9.0-magnitude earthquake occurred near the Tohoku region of Northeast Japan. The epicenter of the earthquake lies 17 miles below the earth’s surface in the Pacific Ocean, 81 miles off the coast from Sendai City.  Intense shaking could be felt from Tokyo to Kamaishi, an arc of roughly 360 miles.

The earthquake generated a tsunami with waves of more than 30 feet that caused widespread damage to a swath of the northeast Japan coastline. In addition to the significant destruction of buildings, infrastructure, and human property, two of Japan’s 17 nuclear power stations (sites)—Fukushima Daiichi and Fukushima Daini—suffered damage due to the tsunami.  All three of the six operating reactors at Fukushima Daiichi Nuclear Power Station and all four reactors at Fukushima Daini Nuclear Power Station, both operated by Tokyo Electric Power Company (TEPCO), shut down automatically in response to the earthquake.  TEPCO is one of ten member companies of The Federation of Electric Power Companies of Japan (FEPC).

A state of emergency was declared at Fukushima Daiichi at 7:03PM March 11.  Unit 1 and 3 reactors at Fukushima Daiichi lost primary reactor cooling because of a loss of all electrical power. Emergency cooling systems were engaged to lower the core reactor temperature.  In order to alleviate the buildup of pressure, slightly radioactive vapor, that posed no health threat, was passed through a filtration system and emitted outside via a ventilation stack from Unit 1 reactor vessel at 9:07AM on March 12 and Unit 3 reactor vessel at 9:20PM on March 13.  At 3:36PM on March 12, an explosion occurred at Fukushima Daiichi Unit 1 reactor damaging the roof of the secondary containment building. The explosion—caused by the interaction of hydrogen and oxygen vapor between the primary containment vessel and secondary containment building—did not damage the primary containment vessel or the reactor core.  Four workers who were injured by the explosion were transported to a nearby hospital.

In order to control the pressure of the reactor core, TEPCO began to inject seawater and boric acid into the primary containment vessels of Unit 1 (8:20PM, March 12) and Unit 3 (1:12PM, March 13).  There is likely some damage to the fuel rods contained the reactor core of Unit 1 and 3 reactors.  The water level in the reactor vessel of Unit 2 reactor is steady. Personnel from TEPCO are closely monitoring the status of Unit 1, 2, and 3 reactors. The highest recorded radiation level at the Fukushima Daiichi site was 1557 micro sievert (1:52PM, March 13).  The most recent reported level at Fukushima Daiichi is 44 micro sievert (7:33PM, March 13).

While representatives of the Japanese government have acknowledged the potential for partial meltdowns at Fukushima Daiichi Unit 1 and 3 reactors, there is no danger for core explosion, as occurred at the nuclear power station at Chernobyl in 1986.  Control rods have been successfully inserted at all of the reactors, thereby ending the chain reaction.  The reactor cores at Fukushima Daiichi and Daini power stations are surrounded by steel and concrete containment vessels of 40 to 80 inches thick that are designed to contain radioactive materials.

At 7:45AM on March 12, a state of emergency was declared for Fukushima Daini. There is electricity available at all four of the reactors at Fukushima Daini, including Unit 3 reactor.  Although there is limited availability of the cooling water pumps at Unit 1, 2, and 4 reactors, TEPCO is working effectively to maintain constant cooling in the primary containment vessels.  TEPCO confirms that no radioactivity has been recorded outside of the secondary containment buildings at Fukushima Daini.

Two other plants in the Tohoku region, Onagawa Nuclear Power Station and Tokai Nuclear Power Station, were automatically shut down in response to the earthquake.  The four reactors at these plants have functioning cooling systems and are being monitored by plant operators.  The Rokkasho Reprocessing Plant and accompanying facilities, located far north of the tsunami zone in Rokkasho Town, is operating safely on backup power generation systems.  Japan Nuclear Fuel Limited (JNFL), which operates the Rokkasho facilities, drained a 600-liter spill from the containment pool for spent fuel through a specialized wastewater treatment system.  Two casks of low-level nuclear waste (LLW), which were being prepared for transport from Mutsu Ogawara Port when the earthquake occurred, have been successfully received at the Rokkasho facility.

Japanese nuclear facilities are built to exacting safety standards.  They are designed to withstand powerful seismic events, such as earthquakes.  In this earthquake—the strongest recorded over the past 100 years in Japan—the containment structures of Fukushima Daiichi maintained their structural integrity.  These facilities were designed to withstand tsunamis within a range of assumed strength. In this event, however, the force of the tsunami exceeded the assumed range and flooded diesel generators at Fukushima Daiichi power station, thus precipitating the loss of power for the reactor cooling systems.

In order to minimize adverse health effects of any potential radioactive release, the Japanese government issued an evacuation order at 9:23PM on March 11 for a radius of 1.86 miles around Fukushima Daiichi.  By 6:25PM on March 12, the evacuation area has been enlarged to cover the approximately 70,000 residents within 12.5 miles of Fukushima Daiichi and 6.2 miles of Fukushima Daini.

In addition to supporting the evacuations near Fukushima Daiichi and Daini nuclear power stations, TEPCO is collaborating with the Japanese government to ensure the safety of the all people in the affected region.  Iodine tablets, to counteract the effects of radioactivity on the thyroid gland, have been distributed to people at the boundary of the evacuation zone.  Sophisticated radiation screening equipment has been mobilized to measure radiation exposure for people close to the evacuation area. The Japanese Nuclear and Industrial Safety Agency said that as many as 160 people may have been exposed to radiation around the Fukushima Daiichi station.  TEPCO and the Japanese government will continue to use their full professional and technological resources, as well as those offered by international organizations, to ensure the safety of those displaced by the earthquake and tsunami.

The automatic shutdown of the 11 operating reactors at the Onagawa Nuclear Power Station, Tokai Nuclear Power Station, Fukushima Daiichi and Daini, represents a loss of 3.5% of electric generation capacity for Japan.  In addition, several thermal power stations were damaged in the earthquake and are currently under repairs.  In order to compensate for this loss of electricity production, TEPCO has instituted rolling blackouts, information about which can be found on the TEPCO website.  The Japanese government is also urging all residents in Japan to minimize their electricity use in order to support the relief and recovery effort in Tohoku.

FEPC, in cooperation with TEPCO and related organizations, will continue to work tirelessly to provide the public with the most accurate and timely information on the situation at the Fukushima Daiichi and Daini nuclear power stations


  1. archjr (History)

    Thanks. The hyperventilating in the community (you know who you are), and the old MSM, has been disappointing, to say the least. “The End of the Nuclear Renaissance” is already being broadcast, and there are a lot of lessons being learned that stand on pretty shifty ground.


  2. MWG (History)

    I’ve been tying to understand the radiation levels, and have been frustrated to see them listed in the nonsensical units of microSieverts. Do they mean microSieverts per hour? Has anyone seen a report in units that make sense, and with more information on location?

    • Jeffrey (History)

      I presume it is per hour. I think most detectors are set to measure in one-hour increments. (I wonder if it rolls, or just does the the equivalent of calender years?)

      The nuclear industry loves microsieverts. When I went to Pierrelatte and Marcoule, all I got was a lousy microsievert.

      Seriously. 1. I was the only one, too. I guess I shouldn’t have licked the fuel ports.

    • wasd (History)

      You can get English language press releases from the nuclear and industrial safety agency at
      Here is the Fukushima Dai-ichi Nuclear Power Station reading from the latest press release, they are in microSv/h:

      MP2 (Monitoring at north- northwest of Unit1 and northwest of the End of Site Boundary for Unit 1 ) :
      450 microSv/h(20:10 March 13)
      →680 microSv/h(3:50 March 14)
      MP4 (Monitoring Car at North West Site Boundary for Unit 1)
      44.0 microSv/h(19:33 March 13)
      →56.4 microSv/h(04:08 March 14)
      (Surveyed by MP2 as MP1 is in the top of the cliff)
      MP6 (Monitoring at the Main Gate)
      5.2microSv/h(19:00 March 13)
      →66.3 microSv/h(02:50 March 14)

      I have seen >1000 microsieverts an hour measurements on either Reuters, the BBC and/or NHK world. This was IIRC before the explosion at reactor 1. I think they were at the front gate of the plant. Early on there was increased radiation measured in the turbine building and there was reports about radiation being to high to safely operate valves manually.

      I cant vouch for the link or NISA myself and dont know who collected these measurements but their information has tracked with what I have seen on NHK World which I assume is what ACW readers are watching anyway, how else would they keep up with North Korean missile test news?

  3. TRH (History)

    Thanks for this. It’s nice to get real information.

    I just suffered through CNN and Bill Nye the Science Guy giving informed commentary, including references to The China Syndrome …

    It seems that the news organisations want another Chernobyl badly – one can only postulate that they are completely out of touch with the tragedy of such a disaster and only interested in selling ads.

  4. Jeffrey (History)

    Well, I’ve been having this argument with myself.

    On the one hand, I understand why afficionados of nuclear power are irritated that radiation risks are held to a different standard than other risks. (I mean, really, have you tried to breathe in coal-powered China lately?)

    But too many of the afficionados treat that as a license to just flat out lie — to say that there are no safety risks (ahem), that you can’t render reactor grade plutonium into a bomb (just false), no environmental costs (same), etc.

    Generating energy is dirty. You pick your poison. Nuclear reactors will fail. Is that better or worse than pumping CO2 and pollutants into the atmosphere with coal plants?

    I don’t know.

    The hyperventilating community sees this as a chance to stick it to nuclear power. And NEI flack is making ridiculous statements like ““But in the scheme of things, is it a disaster? We don’t think so.”

    Yeah, pal, this is pretty much the fucking definition of “disaster.”

    All of them egged on by a media that is openly enjoying this disaster. (One reporter expressed disappointment that I had made it back to the United States because it is a better story if I am Japan. She pointed out that Dianne Sawyer had just flown to Tokyo. How exciting!)

    It’s just a total pundit shit-show.

    • Eve (History)

      Green plant energy is not so dirty, they have been round a couple of 100 million years :0). I hope they invest more in this research.

      I also agree with some of your comments, but then again I was totally dismayed that the IAEA website of all pages could not respond to an 11 X increase in traffic and was out for several hours. To me that was a disaster.

  5. Ben (History)

    Come back safely Jeffrey

  6. archjr (History)

    I believe and certainly hope the previous record bullshit quotient has been eclipsed, at least on things nuclear. Waders: ON!

  7. Red_Blue (History)

    There are pretty big questions raised by the initial timeline. For example, why did it take them two days to hook up the Diesel fire pumps for direct low pressure injection to the cores of Daiichi reactors 1 and 3? I remember that initially they reported using RCIC for both reactors with steam powered turbo pumps and battery power for control of valves. Something strange must have happened during saturday, before running out of battery power and before the explosion in Daiichi 1.

    TEPCO also reported several occasions of discharging steam from the suppression pool filtered vent lines and out of the stacks to reduce pressure in the suppression pools, which should have allowed them to reduce RPV pressures enough to start injection with the plant fire pumps (or even pumps of fire trucks brought in) before the explosion of the reactor 1 building upper levels.

    It stands to reason that they must have had, and continue to have, some other problems as well, most likely causedby the quake or tsunami, to explain why they are only now being able to pump fresh water with new connections to the reactor pressure vessels (and apparently also seawater to the dry/wetwells?).

    Other questions of interest are such as when was reactor 1 refueled previously? Were there any fuel rods in the spent fuel pool (located next to reactor well head, within likely pressure effects of the explosion and currently probably in the open air)?

    • rwendland (History)

      Re spent fuel pool – there is a shared pool for Units 1 to 4, located just north of units 3 & 4 – according to a MSN plan of the site.

      So out of the way of the first Unit 1 explosion, but maybe it has suffered in this second Unit 3 explosion, which looks more powerful than the first. Unit 3 is 170% the MWe of Unit 1, so a larger explosion would not be unexpected.

    • Allen Thomson (History)

      > with steam powered turbo pumps and battery power for control of valves

      Out of curiosity, how much battery power, maximum and average load, are we talking about?

    • Red_Blue (History)

      The spent fuel storage pool outside the reactor buildings is a separate longer term storage than the temporary storage pool inside the reactor building, next to and above the reactor containment structure.

      My understanding is that spent fuel is first lifted with the crane (now destroyed in reactor 1 and 3 buildings) to the adjacent pool for cooling and later to the pool outside the building. After this second cooling stage it goes to the dry storage (and from there to reproseccing and perhaps final entombment decades later).

      The immediate concern is the pool inside the destroyed structure, now without roof over it (two reactors). There might have been spent fuel in those pools or only very low activity water. After such explosions so close and with the size of the steam/dust clouds, the pools are now probably completely dry.

  8. rwendland (History)

    That FEPC statement isn’t being as clear as you might hope for by saying this:

    “The reactor cores at Fukushima Daiichi and Daini power stations are surrounded by steel and concrete containment vessels of 40 to 80 inches thick that are designed to contain radioactive materials.”

    The concrete top of the BWR Mark I Containment Building, as used in Units 1 to 5, is not continuous concrete (like most PWRs) as you might be led to believe by the above. It has a large removable lid many metres wide, called the BWR Drywell Head. Tests in the 1980s showed it unseated itself at 27 psig and at 117 psig created a leakage area of between 35 and 63 inch^2.

    The lid is there so they did not have to make the concrete containment large enough to permit refuelling within the containment. Instead they lift the Drywell Head and refuel from above the concrete containment, under that steel roof structure you saw blow off in the first explosion.

    If you look closely at the TV video of the second explosion you will see something substantial go a few hundred feet into the air, and appear to come down again. My guess is that is the Drywell Head – which means the steel pressure vessel is now directly exposed to the sky. Hopefully the steel pressure vessel head is still in place. The concrete to the sides is strong and with two containments, so site staff will hopefully still be fairly well protected from direct gamma and neutron shine, as long as they do not fly overhead!

    If you want to find out more about the BWR Containment Building read: (basic info and diagrams pages 6-21)

    • rwendland (History)

      … forgot to say I copied the nice cutaway drawing of a BWR Mark I Containment Building from the Sandia/NRC report to Wikimedia Commons, so it is easier to access. That drawing really helps understand what is happening. You can see the Drywell Head plug above the pressure vessel:,_cutaway.jpg

    • thermopile (History)

      The Fukushima Daiichi #1 plant is a GE BWR-3 with Mark 1 Containment. It was scheduled for decommissioning on March 26th. Seriously.

      The plant at Oyster Creek, NJ, is a nearly identical BWR-2 with Mark 1 containment, and is the oldest operating plant in the US today.

      See some really cool drawings and schematics here:

      (As for microSieverts per hour, most detectors actually aggregate on a 1-second basis, and then multiply by 3600 to get a per-hour reading.)

  9. Wramblin' Wreck (History)

    “The hyperventilating community.” – I like that.

    I don’t think the design engineers ever thought about how well the safety equipment would work when it is knocked around in a tsunami and then covered in mud and conductive, corrosive sea water.

    This was most definitely a situation requiring out of the box solutions. It must have been real interesting in the control rooms.

  10. George William Herbert (History)

    I don’t know that an explosion inside the containment itself explains the explosion. The amount of air inside isn’t sufficient to explain the dynamics. I believe that the flying object was steel roof of the upper structure.

    This is an educated guess right now – I have the tools to model the explosions but I haven’t had the time or inclination to yet.

  11. Andrew Tubbiolo (History)

    Unit 1 and 3 are have blown out now. Can anyone comment on the state of the other 4 units reported to be suffering cooling problems? Are we going to see 4 more large explosions? Before I form a opinion I’m going to wait a few months to see what really is happening right now. But I have to admit seeing these reactors pop off in sequence is pretty darn creepy.

    • rwendland (History)

      Those four are at Fukushima II Nuclear Power Station (aka Fukushima Daini Nuclear Power Station), 7 miles to the north. These four are of a more modern BWR/5 design. This design uses the more recent BWR Mark II Concrete Containment Building, but following the same principles as the Mark I version where we saw the explosions – the change is mainly simplifications to reduce cost.

      They have offsite power at this site, which is a huge help. They are suffering from cooling problems, but backup cooling systems are I think working, and reactor water level is stable. They have prepared to vent gasses to cope with over-pressure, but seem not to have done this yet. It looks much more hopeful at this site.

      The latest TEPCO technical press notice is here (8pm JST March 13th).

  12. JDF (History)

    3 of 6 shown here were shut down for maintenance:

  13. Muskrat (History)

    They say there’s no such thing as a stupid question, so here goes:

    –What happened to all the vaunted backup systems, including the steam generators? It sounds as if once the backup generators got soaked, the plants were doomed. The batteries, the steam generators, bringing in relief efforts, none of that was sufficient. It’s not multiple redundant systems if only one is actually sufficient to keep the system from failing.

    –Why didn’t they import generators from off site? Surely there must have plans to do so, right? Were all the contingency plans based on the assumption that the rest of the country would be fine and able to restore outside power ASAP? Clearly the assumption that no tsunami could come over the sea wall was the primary factor, but was that it? Did everything fail because of that, or were there other unforeseen issues?

    –Why is this hydrogen always being vented into confined spaces where it can blow the roofs off things? I understand the legal/political/PR liability of designing a vent to allow radioactive hydrogen into the open air, but as an emergency matter, wouldn’t it be better to vent it to the sky rather than into what is essentially a concrete bomb casing?

    –That timeline is suspiciously quiet about the early hours. If the real problem is inability to get power to move water around, I find it hard to believe that even a quake-ravaged Japan couldn’t rustle up some diesel generators and a helicopter or two to move them. I’d like to know how the information flowed inside the company and between the company and the government, particularly whether they tried half-measures or hid the truth early on. I know that’ll take months or years to sort out, but still, that report goes from “tsunami” to “explosion” awfully fast.

    Does this count as hyperventilating? Part of me suspects somebody screwed up, and I’m angry. Part of that anger comes from not understanding. We were promised flying cars, robot butlers, and multiple layers of protection on each reactor. What we got were multiple meltdowns.

    • Andrew (History)

      … can we be a little careful using the term “meltdown”. Media usage is already shockingly exaggerated.

    • rwendland (History)

      I’ll have a stab at answering some of those (from memory, without checking). But the real answer will be from the full investigation.

      – They brought in mobile generators, but failed to successfully connect them up to the cooling system for some reason. They tried hard, but there were insurmountable difficulties. The batteries have been misreported I think; they just ran the control systems and valves, not the cooling pumps which would require far more power.

      – They did have an unfiltered venting system, that is what the extremely tall chimneys are for. It was I think retrofitted at some point when they realised the other systems might be inadequate. Don’t know if that was used, but they were just pressure relief, doubt they had blowers to clear all the hydrogen.

      I suspect we will find this was an accident waiting to happen. NIRS state, in a 1996 written critique of the BWR:

      “In 1986, Harold Denton, then the NRC’s top safety official, told an industry trade group that the “Mark I containment, especially being smaller with lower design pressure, in spite of the suppression pool, if you look at the WASH 1400 safety study, you’ll find something like a 90% probability of that containment failing.” In order to protect the Mark I containment from a total rupture it was determined necessary to vent any high pressure buildup. As a result, an industry workgroup designed and installed the “direct torus vent system” at all Mark I reactors. Operated from the control room, the vent is a reinforced pipe installed in the torus and designed to release radioactive high pressure steam generated in a severe accident by allowing the unfiltered release directly to the atmosphere through the 300 foot vent stack.”

    • Jeffrey (History)

      I don’t know, I think we might see one or more containment vessels breach.

      The Sandia study puts the risk of that at 42 percent. If you assume that is accurate (there are so many details that will matter, of course), then there is a less than twenty percent chance all three containment vessels hold.

      Maybe the venting and seawater improves the odds, but it sounds like they are really struggling to keep water in them.

      And I don’t know what to make of the uncertain status of the spent fuel pond(s).

      I don’t want to encourage hysteria, the most likely outcome is a horrible local contamination. But TEPCO is fighting tough odds.

    • Hairs (History)


      1960’s BWRs are not really my thing, but here goes:

      1. The level of redundancy is immaterial if the reactor – or any other industrial facility for that matter – experiences an event outside of its design envelope. My understanding is that the Fukushima plant was designed for the size of earthquake it experienced, and in respect of the quake the plant shut down exactly as it was supposed to. The problem came with the size of the tsunami, which was greater than the design basis. One can argue of course that the design basis for tsunamis should have been bigger – but that’s the wisdom of hindsight. I’m sure that the plant’s designers (and regulators) made very good statistical analysis of what they thought an extreme tsunami would be like in that location but unfortunately they miscalculated.

      Naturally we can now look back and say the tsunami protection was too small, but looking ahead to the future what should we retrofit to existing plants? 10m protection? 20m protection? 30m tsunami protection?! The engineering is eminently possible, but is it worth the crippling electricity prices to build a plant that can withstand a 40m tsunami or a once in, say, 10 million year event? I don’t know the answer to the optimum level of protection and neither does anyone else. In my view it’s a question of making the best judgement on the risks we have (or can realistically project for the future); tragically the judgement for Fukushima was wrong

      2. Importing generators is not so easy. First of all is the size: the sort of generator that can drive the multi-megaWatt pumps that we’re talking about is not small. A typical diesel engine in a locomotive is a few MW, so we’re talking about “importing” engines equivalent to several freight train locomotives. (For equivalence, the primary circuit pumps in PWRs can easily exceed 20 MW – and there are four of them on a good sized reactor – so you’d be talking about flying in 16 diesel locomotives if you were to run a PWR circuit at full flow).

      Secondly, even if you can fly in the main mover you still have to have a generator with appropriate voltage, winding, phase sequence, etc. Plus you’ll need an auto-paralleling device to synchronise it to the busbars. Plus the controls to control it. Etc etc.

      All in all the import of generators in anything less then weeks or months is something that is very difficult unless it has been planned and rehearsed in advance – and even then it requires appropriate equipment to be on permanent standby plus the logistical ability to bring it onto site (something that would probably have been impossible given the state of the roads and railways in the tsunami hit area).

      3. Venting steam into the containment building is part of the designed response to over-pressure in the pressure vessel. If the steam has contacted zircaloy cladding at a high enough temperature then some of that steam is converted to hydrogen, and so the plant design allows for hydrogen entering the containment building in certain accidents. Accordingly most containment buildings (and I assume this applies to Fukushima, although I don’t know for a fact) have a hydrogen igniter / recombination system to safely remove the hydrogen. They work rather like glow plugs behind a mesh (same principle as a Davy lamp) so that the hydrogen is recombined with oxygen to form water without the prooduction of a flame.

      However, such igniters are usually electrically heated, so if there was a loss of electrical power at Fukushima then any igniters may have been useless, or at the least insufficient. The technicians then had the unenviable choice of venting – with the risk of ignition – or allowing the pressure vessel to fail because of over-pressure. In the event, preventing rupture of the pressure vessel (even at the cost of an explosion in the containment building) was probably the least worst option.

      4. As described above, I suspect that it wasn’t feasible (in fact I’d say it was physically impossible) to fly in the sort of generators that were needed.

      Last point: I agree that someone screwed up, but probably only inasmuch as the designers in the 1960’s under-estimated how big a tsunami might inundate the plant. That’s regrettable, but I’m sure it was an error of genuine / scientific ignorance and not one of malice.

  14. tokyo_requiem (History)

    So can someone tell me, in any case, how long it takes to cool these things down, assuming they are covered in water?

    • Red_Blue (History)

      That would be very difficult to estimate, because they have been operated (or rather been uncontrolled) way beyond normal envelope of temperature and pressure.

      I think proper comparisons would be 34 hours for the BWR 5 plants in Daini (Fukushima II plant 10 km from plant I) using partially damaged cooling systems but intact reactor to achieve cold shutdown (primary coolant temperature below boiling point of water) and TMI-2 partially melted core took a month (March 28th to April 27th) to reach cold shutdown.

      Even if the melting is not as bad as in TMI, we should expect several more days until the situation is finally and completely under control.

    • Hairs (History)


      How long it takes to cool down a tripped core obviously depends on how much heat it is generating (from decay heat) plus how much heat you can remove.

      In the case of Fukushima it’s hard to say how much heat is / was being removed because of the loss of pumps, etc. I guess we’ll just have to wait and see what the post-accident investigations say about it.

      Regarding the heat production, for light water reactors you can use the rule of thumb that decay heat (in kW per tonne of fuel) is:

      D = 650 * t^(-0.266), where t is hours since the trip.

      Thus a few seconds after the trip the heat is about 5,700 kW per tonne, or about 4,600 MWth for an 800 tonne fuel load. After an hour the reactor “power” is down to about 520 MWth, and this falls further to 220 MWth after a day and 130 MWth after a week. Even after a month it’s still about 90 MWth.

      Of course, the calculation is only rough – but it gives a reasonable idea of what Fukushima has to contend with i.e. after the first few days the cooling requirement doesn’t change very much, but that cooling requirement still necessitates the removal of about 100 MJ/s of heat for many, many weeks.

    • Jeffrey (History)

      For those of you so inclined, this is a handy reference:

  15. yousaf (History)

    That a major earthquake was going to happen here soon was predicted btw:

    “This source (Mw=8.1 to 8.3) is much larger than the anticipated Miyagi-oki earthquake (M~~7.5) with 99% probability in the next 30 years. ”

    Hope the nuclear industry is doing a thorough literature search.

  16. Seb Tallents (History)


    About that 42% failure rate, where in the Sandia report is this mentioned?

    (I assume you mean:

  17. Seb Tallents (History)

    Ah, PDF 97, not document page 97. Doh.