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Fukushima Nuclear Accident – a simple and accurate explanation

Twitter updates: @BraveNewClimate

New 15 MarchFukushima Nuclear Accident – 15 March summary of situation

New 14 MarchUpdates and additional Q&A information here and Technical details here

福島原発事故-簡潔で正確な解説 (version 3):(東京大学エンジニアリング在学生の翻訳) (thanks to Shota Yamanaka for translation)

Other translations: Italian, Spanish, German, 普通话


Along with reliable sources such as the IAEA and WNN updates, there is an incredible amount of misinformation and hyperbole flying around the internet and media right now about the Fukushima nuclear reactor situation. In the BNC post Discussion Thread – Japanese nuclear reactors and the 11 March 2011 earthquake (and in the many comments that attend the top post), a lot of technical detail  is provided, as well as regular updates. But what about a layman’s summary? How do most people get a grasp on what is happening, why, and what the consequences will be?

Below I reproduce a summary on the situation prepared by Dr Josef Oehmen, a research scientist at MIT, in Boston. He is a PhD Scientist, whose father has extensive experience in Germany’s nuclear industry. This was first posted by Jason Morgan earlier this evening, and he has kindly allowed me to reproduce it here. I think it is very important that this information be widely understood.

Please also take the time to read this: An informed public is key to acceptance of nuclear energy — it was never more relevant than now.


NOTE: Content Updated 15 March, see:

We will have to cover some fundamentals, before we get into what is going on.

Construction of the Fukushima nuclear power plants

The plants at Fukushima are Boiling Water Reactors (BWR for short). A BWR produces electricity by boiling water, and spinning a a turbine with that steam. The nuclear fuel heats water, the water boils and creates steam, the steam then drives turbines that create the electricity, and the steam is then cooled and condensed back to water, and the water returns to be heated by the nuclear fuel. The reactor operates at about 285 °C.

The nuclear fuel is uranium oxide. Uranium oxide is a ceramic with a very high melting point of about 2800 °C. The fuel is manufactured in pellets (cylinders that are about 1 cm tall and 1 com in diameter). These pellets are then put into a long tube made of Zircaloy (an alloy of zirconium) with a failure temperature of 1200 °C (caused by the auto-catalytic oxidation of water), and sealed tight. This tube is called a fuel rod. These fuel rods are then put together to form assemblies, of which several hundred make up the reactor core.

The solid fuel pellet (a ceramic oxide matrix) is the first barrier that retains many of the radioactive fission products produced by the fission process.  The Zircaloy casing is the second barrier to release that separates the radioactive fuel from the rest of the reactor.

The core is then placed in the pressure vessel. The pressure vessel is a thick steel vessel that operates at a pressure of about 7 MPa (~1000 psi), and is designed to withstand the high pressures that may occur during an accident. The pressure vessel is the third barrier to radioactive material release.

The entire primary loop of the nuclear reactor – the pressure vessel, pipes, and pumps that contain the coolant (water) – are housed in the containment structure.  This structure is the fourth barrier to radioactive material release. The containment structure is a hermetically (air tight) sealed, very thick structure made of steel and concrete. This structure is designed, built and tested for one single purpose: To contain, indefinitely, a complete core meltdown. To aid in this purpose, a large, thick concrete structure is poured around the containment structure and is referred to as the secondary containment.

Both the main containment structure and the secondary containment structure are housed in the reactor building. The reactor building is an outer shell that is supposed to keep the weather out, but nothing in. (this is the part that was damaged in the explosions, but more to that later).

Fundamentals of nuclear reactions

The uranium fuel generates heat by neutron-induced nuclear fission. Uranium atoms are split into lighter atoms (aka fission products). This process generates heat and more neutrons (one of the particles that forms an atom). When one of these neutrons hits another uranium atom, that atom can split, generating more neutrons and so on. That is called the nuclear chain reaction. During normal, full-power operation, the neutron population in a core is stable (remains the same) and the reactor is in a critical state.

It is worth mentioning at this point that the nuclear fuel in a reactor can never cause a nuclear explosion like a nuclear bomb. At Chernobyl, the explosion was caused by excessive pressure buildup, hydrogen explosion and rupture of all structures, propelling molten core material into the environment.  Note that Chernobyl did not have a containment structure as a barrier to the environment. Why that did not and will not happen in Japan, is discussed further below.

In order to control the nuclear chain reaction, the reactor operators use control rods. The control rods are made of boron which absorbs neutrons.  During normal operation in a BWR, the control rods are used to maintain the chain reaction at a critical state. The control rods are also used to shut the reactor down from 100% power to about 7% power (residual or decay heat).

The residual heat is caused from the radioactive decay of fission products.  Radioactive decay is the process by which the fission products  stabilize themselves by emitting energy in the form of small particles (alpha, beta, gamma, neutron, etc.).  There is a multitude of fission products that are produced in a reactor, including cesium and iodine.  This residual heat decreases over time after the reactor is shutdown, and must be removed by cooling systems to prevent the fuel rod from overheating and failing as a barrier to radioactive release. Maintaining enough cooling to remove the decay heat in the reactor is the main challenge in the affected reactors in Japan right now.

It is important to note that many of these fission products decay (produce heat) extremely quickly, and become harmless by the time you spell “R-A-D-I-O-N-U-C-L-I-D-E.”  Others decay more slowly, like some cesium, iodine, strontium, and argon.

What happened at Fukushima (as of March 12, 2011)

The following is a summary of the main facts. The earthquake that hit Japan was several times more powerful than the worst earthquake the nuclear power plant was built for (the Richter scale works logarithmically; for example the difference between an 8.2 and the 8.9 that happened is 5 times, not 0.7).

When the earthquake hit, the nuclear reactors all automatically shutdown. Within seconds after the earthquake started, the control rods had been inserted into the core and the nuclear chain reaction stopped. At this point, the cooling system has to carry away the residual heat, about 7% of the full power heat load under normal operating conditions.

The earthquake destroyed the external power supply of the nuclear reactor. This is a challenging accident for a nuclear power plant, and is referred to as a “loss of offsite power.” The reactor and its backup systems are designed to handle this type of accident by including backup power systems to keep the coolant pumps working. Furthermore, since the power plant had been shut down, it cannot produce any electricity by itself.

For the first hour, the first set of multiple emergency diesel power generators started and provided the electricity that was needed. However, when the tsunami arrived (a very rare and larger than anticipated tsunami) it flooded the diesel generators, causing them to fail.

One of the fundamental tenets of nuclear power plant design is “Defense in Depth.” This approach leads engineers to design a plant that can withstand severe catastrophes, even when several systems fail. A large tsunami that disables all the diesel generators at once is such a scenario, but the tsunami of March 11th was beyond all expectations. To mitigate such an event, engineers designed an extra line of defense by putting everything into the containment structure (see above), that is designed to contain everything inside the structure.

When the diesel generators failed after the tsunami, the reactor operators switched to emergency battery power. The batteries were designed as one of the backup systems to provide power for cooling the core for 8 hours. And they did.

After 8 hours, the batteries ran out, and the residual heat could not be carried away any more.  At this point the plant operators begin to follow emergency procedures that are in place for a “loss of cooling event.” These are procedural steps following the “Depth in Defense” approach. All of this, however shocking it seems to us, is part of the day-to-day training you go through as an operator.

At this time people started talking about the possibility of core meltdown, because if cooling cannot be restored, the core will eventually melt (after several days), and will likely be contained in the containment. Note that the term “meltdown” has a vague definition. “Fuel failure” is a better term to describe the failure of the fuel rod barrier (Zircaloy).  This will occur before the fuel melts, and results from mechanical, chemical, or thermal failures (too much pressure, too much oxidation, or too hot).

However, melting was a long ways from happening and at this time, the primary goal was to manage the core while it was heating up, while ensuring that the fuel cladding remain intact and operational for as long as possible.

Because cooling the core is a priority, the reactor has a number of independent and diverse cooling systems (the reactor water cleanup system, the decay heat removal, the reactor core isolating cooling, the standby liquid cooling system, and others that make up the emergency core cooling system). Which one(s) failed when or did not fail is not clear at this point in time.

Since the operators lost most of their cooling capabilities due to the loss of power, they had to use whatever cooling system capacity they had to get rid of as much heat as possible. But as long as the heat production exceeds the heat removal capacity, the pressure starts increasing as more water boils into steam. The priority now is to maintain the integrity of the fuel rods by keeping the temperature below 1200°C, as well as keeping the pressure at a manageable level. In order to maintain the pressure of the system at a manageable level, steam (and other gases present in the reactor) have to be released from time to time. This process is important during an accident so the pressure does not exceed what the components can handle, so the reactor pressure vessel and the containment structure are designed with several pressure relief valves. So to protect the integrity of the vessel and containment, the operators started venting steam from time to time to control the pressure.

As mentioned previously, steam and other gases are vented.  Some of these gases are radioactive fission products, but they exist in small quantities. Therefore, when the operators started venting the system, some radioactive gases were released to the environment in a controlled manner (ie in small quantities through filters and scrubbers). While some of these gases are radioactive, they did not pose a significant risk to public safety to even the workers on site. This procedure is justified as its consequences are very low, especially when compared to the potential consequences of not venting and risking the containment structures’ integrity.

During this time, mobile generators were transported to the site and some power was restored.  However, more water was boiling off and being vented than was being added to the reactor, thus decreasing the cooling ability of the remaining cooling systems. At some stage during this venting process, the water level may have dropped below the top of the fuel rods.  Regardless, the temperature of some of the fuel rod cladding exceeded 1200 °C, initiating a reaction between the Zircaloy and water. This oxidizing reaction produces hydrogen gas, which mixes with the gas-steam mixture being vented.  This is a known and anticipated process, but the amount of hydrogen gas produced was unknown because the operators didn’t know the exact temperature of the fuel rods or the water level. Since hydrogen gas is extremely combustible, when enough hydrogen gas is mixed with air, it reacts with oxygen. If there is enough hydrogen gas, it will react rapidly, producing an explosion. At some point during the venting process enough hydrogen gas built up inside the containment (there is no air in the containment), so when it was vented to the air an explosion occurred. The explosion took place outside of the containment, but inside and around the reactor building (which has no safety function).  Note that a subsequent and similar explosion occurred at the Unit 3 reactor. This explosion destroyed the top and some of the sides of the reactor building, but did not damage the containment structure or the pressure vessel. While this was not an anticipated event, it happened outside the containment and did not pose a risk to the plant’s safety structures.

Since some of the fuel rod cladding exceeded 1200 °C, some fuel damage occurred. The nuclear material itself was still intact, but the surrounding Zircaloy shell had started failing. At this time, some of the radioactive fission products (cesium, iodine, etc.) started to mix with the water and steam. It was reported that a small amount of cesium and iodine was measured in the steam that was released into the atmosphere.

Since the reactor’s cooling capability was limited, and the water inventory in the reactor was decreasing, engineers decided to inject sea water (mixed with boric acid – a neutron absorber) to ensure the rods remain covered with water.  Although the reactor had been shut down, boric acid is added as a conservative measure to ensure the reactor stays shut down.  Boric acid is also capable of trapping some of the remaining iodine in the water so that it cannot escape, however this trapping is not the primary function of the boric acid.

The water used in the cooling system is purified, demineralized water. The reason to use pure water is to limit the corrosion potential of the coolant water during normal operation. Injecting seawater will require more cleanup after the event, but provided cooling at the time.

This process decreased the temperature of the fuel rods to a non-damaging level. Because the reactor had been shut down a long time ago, the decay heat had decreased to a significantly lower level, so the pressure in the plant stabilized, and venting was no longer required.

***UPDATE – 3/14 8:15 pm EST***

Units 1 and 3 are currently in a stable condition according to TEPCO press releases, but the extent of the fuel damage is unknown.  That said, radiation levels at the Fukushima plant have fallen to 231 micro sieverts (23.1 millirem) as of 2:30 pm March 14th (local time).

***UPDATE – 3/14 10:55 pm EST***

The details about what happened at the Unit 2 reactor are still being determined.  The post on what is happening at the Unit 2 reactor contains more up-to-date information.  Radiation levels have increased, but to what level remains unknown.

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.

874 replies on “Fukushima Nuclear Accident – a simple and accurate explanation”

Interestingly the answer to the question why are we where we are, is probably because of government, commercial interests and economics. You can see this with some of the nuclear propaganda of the 60s. The failure of implementing nuclear technology safely is caused by the human desire to consume more and more and the fact that humans won’t consider the remote potential disasters (not in their short term interest.)

I am already looking at the density of nuclear power stations on the east coast of America where a tsunami is a remote potential hazard due to the collapse of a shelf below the water. You might think to be crackpot, but look at the Lisbon Tsunami (1755, I think). Now, tell me that the power-stations are all safe in that situation. My worry, as someone who is not up on nuclear tech, is that something like that might effect several stations at once and it is clear that the people in Japan are almost at a loss to what to do.

I think we must work on using less energy per head and use more renewable energy with a view to cut nuclear power to the minimum (only using the very safest nuclear tech however costly).


Kyodo news is reporting the following:

— Reactor No. 4 – Under maintenance when quake struck, no fuel rods in reactor core, temperature in spent-fuel storage pool reached 84 C on Monday, fire Tuesday possibly caused by hydrogen explosion at pool holding spent fuel rods, fire observed Wednesday at building housing reactor, pool water level feared receding, renewed nuclear chain reaction feared, only frame remains of reactor building roof.

Do they have a nuclear reaction going on in the number 4 spent fuel rod pool?


Why we are where we are, is!
It was a system that worked.
Let me ask all posters on this site!
If a 8+ earthquake and a tsunami hit your home
would it withstand the brunt force?
With what you know now are you going to do anything to change your situation!
your answer is no!
However the Nuclear Energy Field now knows more about Safer places to build and probably to contain it’s backup generators in a different manor.
Which was the problem from the start!
Until the Earthquake and Tsunami had you ever heard of this region of the world?
I rest my case!!


Umm, strange answer Mr Noland. I had heard of Japan, however I had not realised that they had so much nuclear power. I also had not realised that the nuclear world would be in so much disarray about what to do in such an event and I am not feeling reassured that this will not turn out to be a much worse event then is being reported at the moment. So therefore I am not reassured that consideration has been made to the various scenarios that might present themselves in future. Only in the last 1000 years we have had many events that would possibly cause a problem like this. OK people die anyway in these events (maybe 100,000 in the Lisbon Tsunami), however if it then leads to several million because of human misadventure, I would question this form of energy. I am not convinced that the people putting in this technology are clear about this in their heads.


Put it like this. The house is the world and the chimney has just blown off by one of those freak winds that we forgot can happen. After all if the Tsunami kills 100,000 people it is a fraction of the worlds population. However as a result the boiler blows and takes down the house.

I suppose what I am saying is that I like the Utopian thought of nuclear power as shown in the 50s films, however the reality I think is that we are playing with energy that we can only be mastered if designed by non humans and run by non humans, because humans make mistakes and humans are corrupt by nature (survival of the fittest, which is now measured by money).

You are clever guys. Why don’t you consider this new way of working at the other end of the power chain ie. reducing out individual reliance and lobbying governments to do so. Can’t we work on reducing that end.

In the UK and around the coast of Europe we have great tides that might be good for power generation, however the projects researching these are such small scale. I would imagine due to economic/profit reasons.


All I’m saying is this Their system was working fine!
And had a major catastrophe that no one but God could forsee!
And now you Chastise!
Yes we have to Glean from this mistake but it should not be Chicken Little!
Nuclear energy is a Valued asset!
And the Greens of the world!
Are you watching TV, using your computer,staying warm, driving to the store, taking your kids to school,going to the market,and on and on and on but chastise the world for using energy.
Give it up Kids your no better than than the next neighbor who has his needs.
But your telling us you gave it all up.
Let us see the candles in your windows!!!!


Come on guys, start thinking. We need passionate people to change the way we do things. We could have real fun and make money by designing ways to reduce our power consumption.

Having a little thought this afternoon. Why not design light switches that intelligently senses a human in the room ( With what my android phone is capable of I am sure a chip can be designed that is sophisticated enough). You go in the living room and switch on the light, Stay there and you are sensed and the light stays on. If when you leave the room after a few seconds (No human detected) light goes out. The amount of rooms with unnecessary lights in houses around here!! Just make sure it is compulsory in new builds. I am not in it for the money so take it away someone.

Another idea. How about set some electricity ration by making the electricity companies charging a huge amount more when the amount goes over. The base limit would be set to live reasonably comfortably and could be based on size of family, age of house etc. This would drive manufacturers of appliances to reduce power consumption. Over time as the technology becomes more efficient the base limit can be reduced to continue the trend.

I am sure I am making it all sound a little to simple (I am only a normal person) however I am sure you science guys can work it out.

Us humans are like radioactive fuel. If left without controls, we go into meltdown.


Mr Noland. What do you mean only god had foreseen? There is plenty of historical documentation showing similar events including 2004. We have had 6 years since. Failure there somewhere I think.

About candles. It is not about that it is about controlling the way we live. Thank goodness they have a 20 mile an hour speed limit outside my daughters school. There is an example of a control that hurts no one and has saved lives. Let us get control of our energy use.


I am a former licensed operator of a BWR. I will say this: the situation in Japan is bad, very bad, to say the least. There is much information that I do not know about the exact series of events that occurred.

I do not know the exact extent of damage to the containment structures, but they do seem to have withstood much more damage than they were designed to. That said, the containment systems are all passive in nature. They are designed solely to contain their contents, nothing more.

If the operators at Fukushima could have had one thing to mitigate the casualties, it would have been, without a doubt, electrical power. But the area was in a blackout. Why some sort of electrical power was not strung earlier will be the question to answer in the future.

The plants in the US have systems and procedures to combat a station blackout (complete loss of all AC). Operators are drilled on responding to catastrophic system failures concurrent with loss of emergency power sources and loss of pumps. But even then the assumption is that power is restored in (if memory serves) at most a day – not 7 like at Fukushima.

The more time the passed, the better the situation at the plants. But, after so long, batteries are drained. The reactor will cool down enough that no steam can be made for steam driven emergency pumps. But the plant will still heat up, from decay heat and residual heat in the hundreds of tons of steel that make up the reactor systems. If there is no power to run pumps, alternative sources of water must me used: fire pumps. In both plants where I have worked they were diesel powered, but I do not know where they are located or how they are powered at Fukushima.

This is not Chernobyl, nor is this Three Mile Island. Both of those were man made accidents – this is nature flexing her muscles.

Give credit to the operators on scene for doing everything that they can think of to keep the reactor cool. There are many tough choices being made daily that we don’t know about.


God Speed To all of Japan and I ask all to Keep them in our Prayers!
And if you can donate to the people of Japan, to help them help themselves as they have in the past!
My heart goes out to every Citizen of Japan!
You will recover!


The dispassionate analysis of the situation from various viewpoints is helpful. Compassion for the people who’s lives have been turned upside down by one of nature’s most awful events is useful as well. Petty bickering, egotistical arguing, and self promotion diminish the stature of the poster, and provide a sad commentary on why a crisis event cannot be solved readily, speedily, or rationally. The “people in charge” have the same petty egos, “positions of authority”, and lack of awareness being highlighted here. It also provides a ridiculous amount of pure crap for those of us who would like to understand what is currently going on, and it’s implications for the future – for all of us. There is no nationality, race, or religion or occupation that matters when it comes to being a living sentient human being. Perhaps it would be useful to remember that, and at least post relevant information only. Send prayers and tangible assistance to Japan within your ability to do so. PLEASE! Use whatever knowledge you have to better the lives of your fellow human beings. Nothing else matters.


As a follow up to my comments above – “the ridiculous amounts of pure crap” referenced above, is the stuff we should not have to weed through in order to read the posts form folks with perspective, rational comments, and intimate understanding of events or science.


Thank you for this systematic explanation.
I got enough of the gist of it to confirm that the media
have been flogging this whole tragedy with glee and


I am really surprised that many of the technical errors in the main piece that starts this thread have not been corrected. Lets be clear, this article was not written by a nuclear engineer. People who read this article should also read carefully the comments posted later that correct the mistakes.

I am a little surprised that this article continues to be repressed and linked too, without the necessary corrections.

Even now, more incorrect information is being reproduced disseminated from various sources. For example, above another article linked to here, which incidentally links back to this article, boldly pronounces on March 18th, Friday, that:

“The accident has been recorded at Level 4 on the International Nuclear Events Scale, meaning that there are local consequences only (the scale goes up to 7). For reference, Three Mile Island was a Level 5 and Chernobyl was a Level 7.”

From: “Is the Japanese nuclear fallout mostly hot air?”

In fact, the Fukushima nuclear accident was identified as being a level 6 accident by the French Nuclear Safety Authority, the Japanese nuclear safety agency have revised their assessment to Level 5, and the IAEA has not ranked the accident as yet.


The fact is that this event is unfolding as we speak, and so far has only deteriorated as the days go by.. Chernobyl was a very dramatic accident, but this accident is unfolding in slow motion. it may very well be assessed as being more severe than it is at this point, as the weeks and months go by.


Japan hikes n-plant alert level, IAEA calls it extremely serious

“Tokyo, March 18 (IANS) Fire trucks sprayed jets of water on the overheating Fukushima nuclear power plant Friday as Japan’s nuclear safety agency raised the crisis rating to level 5, defining it as an ‘accident with wider consequences’. IAEA chief called it an ‘extremely serious’ crisis.”


Your information is way out of date. Situation is improving, power is on site again. Japan has the incident now at level 5.
You only have to check today’s newspapers, TV channels etc to realise nothing is getting worse – it would be all over the media otherwise.
For up to date information checkout this link to LIVE news updates from JAPAN.


Stevie – I’m confused???????????
Your quote:

“No. You are confused. Japan just raised their rating to level 5.”

You check. That is what I said in my comment above. It was a 4 way back at the beginning – but still a 5 today according to the Japanese.


That is right. Exactly what I said. What precisely did I say that was inaccurate?

As of yesterday the Japanese raised the level to 5, giving it a rating the same as Three Mile Island.

That is absurd of course — 4 reactors in serious shape, coolant problems in spent fuel rod pools in all 6 reactors, one pool possibly dry, primary containment in one (possibly 2 reactors damaged), outer containment on 4 reactors damaged or completely destroyed, partial melt-down at 2 reactors, reported radiation levels at the plant up to at 1000 mSv.

By contrast on the point of how much radiation is being released, the measurement of radiation levels at the TMI plant was 12 mSv, and only partial meltdown of the core, with no breaches in the primary containment.

But there you go… perhaps the Japanese are a wee bit biased.


The Japanese say it’s level 5 on INES – which is consistent with Three Mile Island. Severe damage to the reactor, elevated dose rates in some places on site, no significant off-site health physics impact, nobody injured by radioactivity.

One chap in France says it should be INES level 6. But can an incident with no harm to people actually be rated at INES level 6?

Who officially decides on the INES category? Is it the IAEA? Or the country responsible for managing the incident?


Nobody has been harmed or injured by radioactivity or ionising radiation, as far as I’m aware, and certainly nobody is dying from exposure to ionising radiation.

If you actually have evidence to the contrary I would be extremely interested to see it.

To be honest, I’m really not concerned much with what the dose rates are in the plant itself.

The men and women who work there understand dose rates and health physics quite well. They routinely work in areas of elevated above-background dose, and they know how to work safely in those environments. They understand how to measure and quantify the radiation field in the working environment, and the accumulated doses that they’re personally receiving.

They understand how to manage shielding, exposure time, radiation measurement and dosimetry in order to get the work done safely and effectively.

Even with abnormally significantly elevated radiation fields in some areas as a result of these incidents, they still know how to work safely. If the radiation dose rate in some particular area is so highly elevated that it cannot be entered safely for any length of time at all, then they won’t be entering it.

It’s pointless to scare the public with elevated on-site dose rate measurements. They’re not working on the site. Leave that for the people with health physics training. I’m much more interested in off-site dose rate measurements, personally, as those are the measurements that are actually of relevance to the public.

Although of course tens of thousands are dead or suffering as a result of unrelated effects of this tragic earthquake.


[ unsubstantiated personal opinion deleted. Please re-post with authoritative references]There have been explosions, fires, power failures and numerous other events that disturb the normal work routine, and make it necessary for people to take additional risks, and for unexpected things to happen. So, while there are no reported deaths, as yet attributed to radiation, we do know that several people have been contaminated to a greater or lesser extent:

“According to IAEA’s report, 17 people – nine TEPCO employees and eight subcontractor employees – “suffered from deposition of radioactive material to their faces” due to low levels of exposure and were not taken to a hospital; two policemen were decontaminated after being exposed to high levels of radiation; one worker suffered from “significant exposure during ‘vent work,’” and was transported to an offsite location; and firemen who were exposed to radioactive material are being evaluated.”

[unsubstantiated personal opinion deleted]. So, yeah, “safely and effectively”, as you put it, until a valve explodes in your face.


People are missing, and people have been killed, no doubt [unsubstantiated personal opinion deleted].

But if biggest concern is not the “on-site dose rate measurements and the effect on the general public”, you will be happy to know that TEPCO moved their sensors from the main gate, soon after they started reading over 700 mSv/hr. and put them by the “west gate” where they read under 400 mSv/hr,[unsubstantiated personal opinion edited]Moving the sensor of site, is one way to solve that problem. Source:


I see, so that is what the IAEA is saying when they say that firemen are being “evaluated” after exposure to radiation. They mean “nobody is actually receiving any dose at harmful levels”.

Silly me, I thought they were being “evaluated” by medical personnel to see if they had received a dose at harmful levels”.

Or perhaps that idea is inconsistent with what you want to believe, since you have absolutely no evidence to contradict the on site medical personnel who seem to think evaluation is necessary.

I am sure they will be quite relieved when they read your blog postings and immediately send them home with a clean bill of health.


Steady there Stevie this is what is actually said about exposure to radiation in the article you linked to. Let’s not hype up the situation unnecessarily.This report was on the 17th March – I haven’t read any updates of death or permanent illness as a result of the evaluation. Have you? If so please post the citation.

“Also according to IAEA’s report, 17 people – nine TEPCO employees and eight subcontractor employees – “suffered from deposition of radioactive material to their faces” due to low levels of exposure and were not taken to a hospital; two policemen were decontaminated after being exposed to high levels of radiation; one worker suffered from “significant exposure during ‘vent work,’” and was transported to an offsite location; and firemen who were exposed to radioactive material are being evaluated.”

Read more at Suite101: IAEA Reports 25 injured, 19 Contaminated At Fukushima


“TOKYO, March 19 (Xinhua) — Chief Cabinet Secretary Yukio Edano said on Saturday that radiation levels have exceeded allowable limits in spinach and milk following radioactive leaks at the troubled Fukushima nuclear plant.”

Anyway, you guys go on believing what you desperately want (or need) to believe, for whatever reasons you want (or need) to believe.

And just think, when this article was first published, it calmly professed that there would be no radiation leakage at all… now we are down to trying to determine what a “safe” level of exposure is.


Please consider your sources, Stevie. China is no friend of Japan. Even before the fishing boat/Japan Coast Guard incident, there was a good deal of animosity between the two countries. Not only is China a communistic country, they are a direct competitor in almost every way to Japan. Do you really believe they are going to play fair?


Actually, I’m sure the quote from Mr. Edano is accurate but it is important to have the full story not just a snippet.


steviesmyths, from the article you cite, it would take five years of consumption of this spinach to receive the equivalent dosage as a CT scan. For the milk, you’d have to imbibe for a year for a similar result.

I think CT scans are safe. If you agree with me, you are compelled to conclude that the radiation measured in these foods are safe levels.


kay chaps! Lets avoid a barren and vain polemic.
What you are blaming Stevie for, is to me not understanbable. Stevie is trying to stick to facts, and is being cautious. No one here I suppose is trying to sound a prophet of doom, right?
I guess the purpose of the thread is to provide with SOME elements of information about what’s happening, but reality is happening there, not on this thread, whatever any one of us would tend to agree with.
I suggest we exchange valuable information on technical matters, whenever someone knows even a tiny bit. And also valuable links on the on going news, as you are already doing. Let us leave our opinions aside for a while, would we?
So, I’m no nuclear engineer, but I’ve passed my Phd in a research center for nuclear power in France, and I don’t reckon any one my acquaintances then explaining to me about the safety of plants, to have considered such a dramatic sequence of threatening accidents on so many reactors.
The situation is clearly critical, and catastrophic.
So please wait and see, before being alarmist or reassuring.


On the NHK news site this morning ir was reported that temps taken above the reactors was 100 degrees and stated if Nuclear melt down was happening the temps would be above 1000 degrees.


So the Crisis is over and all the ones who Chicken Little made run for their lives no have nothing to say!
Hopefully this is very positive for the People of Japan!
And Radiation can be curtailed!
Prayers and Positive energy going out to all the Japanese People! From the People of USA!!!!!


John, you are right about the comparison between the amount of radiation and the time period it would take for consumption of contaminated food, and overt and immediate health side effects. But it should be understood that radioactive dust fallout in this kind of event is not distributed evenly.

A lot depends on the weather. Studying the fallout from Chernobyl, we see that contamination was patchy. Some areas closer to the reactor were nearly untouched, others further away were massively contaminated requiring evacuation.

The contamination here seems to follow the same pattern, In this case milk 20 km from the reactor, in Fukushima prefecture was found to be contaminated, much further away spinach in Ibaraki (on the coast) was contaminated.

So, a sample from somewhere indicates a relatively low level of contamination. We don’t know how comprehensive the Japanese survey is but under the prevailing emergency conditions, we can guess that it is just a spot sample, from some food items.

Some food milk and spinach from these areas may be totally free of contamination, others, much more contaminated than the survey sample. Personal contamination through consumption may just depend on the luck of the draw.


“More workers were thrown into the effort — bringing the total at the complex to 500 — and the safety threshold for their radiation exposure was raised 2½ times so they could keep working.”

[personal opinion not supported by reference. Please do not edit quotes to suit your arguments or you will be banned as a troll]


Yes journalist have taken poetic license and not used facts!
Can we have one case of radiation poisoning!
Yes there was a death i remember in the crane of one of the reactors but that was not due to radiation!
Please use facts and figures when posting about radiation!
There was a report of Radiation hitting the west coast!
But was one Billion times likely to have any ill effect on any human!
Why report such outlandish claims!
Can we have the facts just the facts!
Why does the Media try to cause panic when none is due!
All you surfers in LA you will get more radiation this summer with out your shirts than you were exposed to the other day!
As for the gentleman that broke down on Japanese tv I saw it!
However until there are fatalities due to Radiation I will stay viligant That the Japanese will overcome this obstacle.


What do you not under stand!
The Reactors are being dealt with!
Whatever health issues are already etched in stone!
Yes we don’t want more exposed!
But all the rhetoric in the world will not change the events of a lifetime!
Get over it move forward and stop the Whining!
I saw more backbone and fortitude from Japanese
who lost their entire home and family than you sniveling whiners from the west because you may get a Japanese carrot that has the risk of nill!
And if you don’t want to listen to the ones on this sound board go away!!!!


Interesting. A few comments:

The diagram shows “primary containment” and “secondary containment”, and the article speaks of “first”, “second”, and “third containment”, though it doesn’t appear that “first” and “primary” (despite being synonyms) are the same here. A bit confusing, until I figured out the diagram was probably taken from elsewhere and should be ignored.

As others have pointed out, the Richter scale is not often used today, especially for larger quakes. (Was it 8.9 on the Richter scale as well?)

You say that what happened in Chernobyl “did not and will not happen in Japan”, yet admit that one of the causes of that disaster was that the reactor was “not managed properly by the operators”. How can you rule out potential operator error in Japan? It sounds as if your analysis is (with the exception of the hydrogen explosion which already occurred, which may have been unintentional, if benign?) assuming perfectly knowledgeable and competent operators. What’s the worst case scenario without this assumption?

And more generally:

Someone once made the (excellent) point that journalism typically only says what the journalist knows, yet what is important to us as the reader are three things: what we know, what we don’t know, and how we came to know these things. With only one or two exceptions, this article is still all of the first type.

I’m not referring to basics of how nuclear reactors work. I’m referring to the design and emergency procedures for the Fukushima reactors, and what has happened to them — especially since, as you note, the normal news outlets are notoriously inconsistent and unreliable with scientific matters. I’ve worked with scientific and engineering groups overseas, and I’ve never seen the level of detail that scientists seem to know about the reactors in Fukushima.


I’m not whinning I’m “just a mum” worried about her son, his wife and family living in Tokyo. I am trying to plow through this information but it is hard to understand it all if you have no idea about nuclear reactors, radiation, etc


No just a good lashing for you little people who would still wandering the Streets instead of getting busy rebuilding like this Great Nation has!
With no thanks from the naysayers and reporters who know crap news sell better than heroic ones!!!
Pull your heads out of the sand, The sun does shine!


Here from the Massachusetts Office of Health and Human Services:

“For perspective, the Environmental Protection Agency (EPA) has published emergency dose guidelines. These guidelines state that doses to all workers during emergencies should, to the extent practicable, be limited to 5 rems (0.05 Sv). The EPA further states that there are some emergency situations for which higher limits may be justified. The dose resulting from such emergency exposures should be limited to 10 rems (0.1 Sv) for protecting valuable property, and to 25 rems (0.25 Sv) for lifesaving activities and the protection of large populations. In the context of this guidance, the dose to workers that is incurred for the protection of large populations might be considered justified for situations in which the collective dose to others that is avoided as a result of the emergency operation is significantly larger than that incurred by the workers involved.

Table 5 presents the estimates of the fatal cancer risk for a group of 1,000 workers of various ages, assuming that each worker received an acute dose of 25 rems (0.25 Sv) in the course of assisting in an emergency. The estimates show that a 25-rem emergency dose might increase an individual’s chances of developing fatal cancer from about 20% to about 21%.”

It seems that the Japanese are using the same emergency protocol, and we can assume that any person among the emergency crews operating at the plant will be exposed to the maximum level of exposure. [personal opinion/projection un-supported by reference given]


I believe all who stayed and worked on this situation volunteered! Regardless of stats and numbers these few knew someone had to take up the Sword and slay this Dragon now instead of another generation!
Hero’s all!
I do not see them looking for the sympathy you shed!
This will be my last post on this site!
I wish to Thank the Heroic People of Japan for showing the world
what it is to have compassion for their fellow man
If ever I had to go through the strife of a catastrophe
I would want the peoples of this nation to come to my rescue!
Prayers and positive Thoughts to the Great People of Japan!!!!


[…] ウィキペディアでは「福島第一原子力発電所事故」という記事がつくられましたね。 そこでも紹介されている、マサチューセッツ工科大学の原子科学の専門家らが書いた文章がある。今回の事故を観察し、原子力発電について分かりやすく説明したものだ。それを紹介したブログに書かれていた導入文を紹介する。 私はこの文章を3/12(現地時間) に書いており、日本の事故に関して安心してもらおうと思っています。まず、状況は深刻ですが、管理下にあります。そしてこの文章は長いです。しかしこの文章を読んだ後、あなたは全てのメディア記者よりも原子力発電所について理解することとなるでしょう。 重大な放射能の放出は、今までもありませんし、これからも「ありません」。 「重大な」とは、長距離の飛行や、元々の放射線レベルが高い地域で作られたビールを飲むことで受ける放射線より被曝量が多いことをいいます。 私自身地震がおきてから全てのニュースを読んでいます。しかし、今まで一つとして正確で誤りのないレポートはありませんでした(この問題の一部は日本危機通信の弱点の一部でもありましょう)。「誤りのないものがない」とは偏った非核報道(最近は極普通ですが) をさしているのではありません。「誤りのないものがない」というのは物理や自然法則に関する目に余る間違いであり、原発の建てられ方と制御方法についての基本的な理解の欠如による事実の大きな誤解でもあります。私はCNN の3 ページにわたるレポートを読みましたが、どの段落をとっても、誤りが含まれていました。 (東京大学工学部 Shota Yamanaka訳、下線Dr Kats修正) Original found here […]


guillaume attuel:

The situation is clearly critical, and catastrophic. So please wait and see, before being alarmist

I think someone has forgotten to take their own advice.


I see that I have been edited for making a personal opinion/projection un-supported by reference given, which is not actually the case.

As shown in the reference, the percentage chance of someone getting a lethal cancer as a result exposure at the maximum “safe” dosage allowed at the plant as of Tuesday, increases by 1%. From 20% to 21% A one percent increase means that statistically speaking 1 person in 100 will contract a lethal cancer as a result of contamination, at the maximum safe levels that are now allowed in the plant.

Here is the pertinent relevant quote:

“The estimates show that a 25-rem emergency dose might increase an individual’s chances of developing fatal cancer from about 20% to about 21%.”

Therefore, if four hundred firefighters are exposed at the maximum emergency level allowed, four will contract cancer as a result of their exposure. To dispute this is like saying that there is no way that we can establish a statistical correlation between smoking cigarettes and cancer, and say that x number of people who smoke will contract various smoking related cancers.

Authorities, and the volunteers themselves have assumed this risk, because they think it is unavoidable and necessary to ensure the safety of the population at large.

In any case, to be censored like this in the context of an article that has numerous factual errors is a bit hard to explain.

First the article broadly states, incorrectly, that there was one hydrogen explosion at Chernobyl, when in fact their were two explosions. It is widely accepted that the first was a steam explosion. The second, MAY have been a hydrogen explosion. This point has been contested. In fact, the exact cause of the second explosion has never been confirmed, and the hydrogen explosion is just one theory among several.

“Two distinct explosions were heard, the first being the initial ‘steam explosion’ and the second most probably an explosion of hydrogen evolved in the course of zirconium-steam reactions.”

Source Nuclear Engineering International:

A point of contention perhaps, but to be accurate the article should outline clearly that the “hydrogen explosion” theory at Chernobyl is debatable, as the above referenced article does.

Secondly, the article goes on to assert that the “RBMK reactors they used both graphite and light water as moderator”. This is not true, at all. Light water in an RBMK reactor is a coolant and absorbent that limits reactivity. The graphite is the moderator that accelerates reactivity — water retards this process.

The reason that the GE plants of the kind at Fukushima, can use light water as a moderator is because they use enriched uranium, whereas other systems that use better moderators, such as graphite (RBMK) or heavy water (CANDU) can use unrefined uranium, which has the advantage of cutting down on processing costs.

If the people who maintain the board are going to censor on the basis that they believe certain things are not factual, or supported by the evidence, they should correct the opening article for clear factual errors.


I am tempted to borrow from an age-old journalism adage: If it bleeds, it leads. And I fault the media for not getting the details right.

Nuclear power is a complex industry, with a language all its own. Spokesmen try to translate nuke-speak into the common vernacular, sacrificing (important) detail for easily understood words. Journalists then take those words and simplify them more, giving their own flourishes to make it more newsworthy and dramatic, as drama and fear sell papers and make for good ratings, not concise facts.

As a side note, an earlier poster had a link to the state of Massachusetts saying that the EPA had set radiation dose limits for casualties. The EPA has nothing to do with setting dose limits for occupational exposure; in the US it is the Nuclear Regulatory Commission, as set forth in 10CFR20 (which every rad worker basically memorizes). Read here:


It is alleged sometimes, and told to have been considered a possibility by the soviet experts of that time, that a corium of a RBMK reactor that would have hit water, could have triggered a chain reaction of infinite reactivity, in other words a nuclear explosion. There is very little communication on that, especially from the AIEA, apparently to prevent from contesting the crisis management of the USSR. It seems that situation was much more critical due to full core power at the time of the melt down, and beacuse of graphite. The main concern if I got it right, was that heavy elements like plutonium and uranium would phase separate from the lighter ones, therefore enrich locally to high concentrations. It was not a only concern of an explosion due to water separation in hydrogen, or a redox reaction with graphite.
Although this is highly improbable (hopefully)
What do we know about a corium which would have formed in one BWR or PWR core, even after emergency rods have played their part well ?


I am not a scientist, but after reading about this nuclear plants and the way they produce energy, I have a question.
My understanding is that the steam produced by the boiling water heated by the heat produced by the nuclear rods is constant. Is there a water pumping system that will operate with the motion of the turbines moved by the steam. In other words a water pumping system that does not required electrical power just the transfer of mechanical energy from the turbines to the pumping mechanism. I have the conception os such a system. I am sure that it can be done! If all the nuclear power plants around the world have this flow, it just occured to me if the energy that produces the heat never stops


Ok Kids sorry! Had to come back!
I am a little disheartened in the fact that NHK reports the there is too much debris to be able to park a fire truck in close proximity to one reactor to adequately
Spray water!
Get a 5yard loader and a crane! Also get a Komatsu Excavator and dig a ditch to the ocean it’s close could have been done already! Make a holding Pool for water!
And a pipeline to all reactors!
Take that loader and clean the area of debris!
It’s not that difficult!
Go get a pipeline engineer and a construction engineer!
The progress you have made could have been done 6 days ago!!!!


Guillaume. I highly doubt there is going to be a single catastrophic event at these reactors. It is not outside the range of possibilities, but design features of this reactor system basically prohibit massive core meltdown, because loss of coolant, is also the loss of the “moderator” that triggers reactivity.

The long term problem here, to my mind, is the measures that are undertaken to control that process will require ongoing releases of radiation, over a long period of time, due to the loss of the outer containment, and other factors.

It might take months or even years to bring the situation under full control, and in that intervening time engineers may have to make multiple controlled releases of radioactive material into the atmosphere.


Yes thank you Stevie, I got you on that, and I follow you. On reports, Japanese are seen now to start complain about the lack of factual information they are getting via their own media. It is rather rare. I’ve heard too on the news, that no special measures to upgrade similar plants throughout japan will be taken! Only an evacuation perimeter extended from 10 to 20 km. They surely should protest against that. What all this reveals first is that the public is getting too much emollient words, instead of facts and clear explanations. There was and is indeed a real disinformation, if not misinformation in some cases. Too much publicity.


steviesmyths, on 21 March 2011 at 9:16 AM — The situation will be under full control shortly after external electric power is available at all units.


Is that right David? That seems a little premature, since Japanese authorities are not even sure that the existing pumping systems will even work on the damaged plants, according to my information.

Indeed, they have returned power only to the undamaged units, number 5 and 6.

What is the source for your assertion. Mine is the New York Times, here:

Where it says:

“After connecting a mile-long electrical transmission line on Saturday, workers made progress in starting to restore power to the plant, which may allow the operator to restart its cooling systems. The government said that power was returned to Reactor No. 2 at 3:46 p.m. Sunday, and that other reactors were also expected to gain power early in the week.

Even with electrical power extended to the reactors, there was no immediate indication from officials that the damaged pumping systems could be quickly restored. ”

Perhaps you can explain precisely what reasoning you use to assert that after an severe earthquake, flooding by tsunami, several explosions, partial damage to some of the core, damage to the Torus at the number 2 reactor that simply restoring power to the facility will magically mitigate the after effects of all that has happened, and everything will work properly thereafter.


Thank you for an informative and understandable article.

As a former nuclear power plant operator (single and multiple-reactor operations) in the world’s largest nuclear power complex, I can attest that–despite a few niggling particulars–the article is accurate, and gives a forthright explanation of the nuclear situation in Japan. Oh, and I have no economic interest in nuclear energy. My last position involved manufacturing thin-film rooftop solar cells.

While I am glad to see genuine questions and concerns expressed, it seems unfortunate that detractors’ comments comprise primarily invective and ad hominem attacks. Instead, all of us need to concentrate on learning more about nuclear energy; in this case, understanding mitigates fear. (As a parallel, some people are terrified of cliffs, and rightly so, in a sense; but a trained climber with the right equipment, understanding the danger, can make an exhilarating ascent.)

The lack of understanding on the part of reporters and commentators is extremely frustrating. As several have commented, the worker who received something like 20mrem of radiation exposure was rightly removed from the scene and taken to a hospital where he could be examined with more sophisticated equipment, and perhaps treated to minimize the longevity of any radioactive nuclides on or in his body. But to hear the reportage (as it made its way to the US Midwest, anyway), he was about to turn green and glow.

Responsible reporting needs to provide sufficient, accurate detail, as well as context and perspective; unfortunately, most of what you hear is designed to get headlines–and reporters have a financial interest in getting their story in print or on the air.

To gain an understanding of what’s happening in Japan, more people need to read articles like this, and use questions that arise for further inquiry.


A quick aside on nomenclature related to containment. The structure of the fuel rod and the fuel it contains do indeed form the first layers of containment of the fission products. In that sense, the reactor vessel and outer structures form third and subsequent containments.

However, operationally, the thick concrete and steel surrounding the reactor vessel are usually considered the primary shield, and shielding around steam plant components, which contain radioactive steam in BWR (Boiling Water Reactor) plants, would be called secondary shields. (This may vary between various configurations.)

My point is not to get too hung up about “discrepancies” between some of the terms used in technical discussions like this. Instead, try to clarify and understand first.

Incidentally, Nitrogen is a highly radioactive nuclide in nuclear plants. Again, as it says on page 34327 (and other places) of the Hitchhiker’s Guide, Don’t Panic! In the reactor core, while fission is occurring–that is, while rods are pulled and the reactor is critical–Oxygen-16 (which, remember, is one of the atoms that compose water) gets one of the protons in its nucleus changed into a neutron. This changes O-16 into N-16 (Nitrogen). The Nitrogen is not happy at being radioactive, and quickly changes that neutron back into a proton, releasing a powerful gamma ray. This all happens fast, with a 7-second half-life, so within a minute N-16 gammas are non-detectable. And remember, they are only in the system while the reactor is critical.


Appreciate your comments David Miller, about intolerance and invective. It’s not nice.

All the same, I don’t think that’s just one-sided. Both camps seem determined at times to knock each other out.

I imagine it must be extremely frustrating to argue the safety of nuclear power, just as it must be extremely frustrating for wind devotees to argue that intermittency is a resolvable problem.

Although they may be competing for investment money and / or political attention, it would be a good thing for people in either camp to ‘walk a mile in the other person’s shoes’ as the saying goes, just to see what it’s like.


In spite of this being an alledgedly ‘balanced’ view it is clearly part of the fightback from the nuclear power industry. There are so many points to correct that it becomes pointless to start dealing with the detail.

A simple point about using a pressure vessel to ‘contain’ a meltdown is that eventualy the pressure has to go somewhere – it is basic science. That is why they had to release the built up pressure (and associated highly toxic fission by-products) into the atmosphere very early on. The alternative is that the pressure inside the vessel builds up until eventually it MUST burst (a bit like like putting an aerosol can on a fire).

AND I think that the idea that “the more the public knows the more likely are to accept the technology” is completely flawed. All that happens is people’s minds turn-off because they cannot think about the horror that a full scale accident would cause. You should not confuse a refusal to think about something horrific as acceptance or ignorance.

Also please consider that it would not matter how many tsunami rolled over a solar PV plant or windmill, there would never be a need to evacuate every living soul to 20km away (at the least).

[deleted personal opinion presented as fact. Please re-submit with references/links.]

In summary: still water runs deep…

“All that happens is people’s minds turn-off because they cannot think about the horror that a full scale accident would cause. You should not confuse a refusal to think about something horrific as acceptance or ignorance.” interesting point there Bill.

Nuclear industry is not the only dangerous one, the chemical agribuisness can be just as bad, and leave traces for a very long time in the food chain. But it is more feared, and as a physicist myself, I must admit, rightly so. It is a challenging and demanding ‘fire’. Do we have tamed it yet?


[…] bravenewclimateのBarry Brooksは、マサチューセッツ工科大学の研究者、Josef Oehmenが書き、元々Jason Morganが投稿した長い記事を再掲載した。BrooksもMorganも原子力を支持しており、原発の「部分的メルトダウン」についてのマスメディアの報道が大げさで、それも間違いだらけだと考えている。Oehmenはメディアで読んだもののみをベースに自身の考えを述べているが、すぐに人々を安心させようと努めた。 重大な放射能漏れはこれまでも、そしてこれからも「ない」。 […]


“Japanese regulators acknowledged the severity of the crisis might be greater than they initially expected. The Asahi newspaper reported Friday morning that the incident’s international accident rating may be raised to level six—a serious accident—on the International Nuclear and Radiological Event Scale based on estimates of radiation emissions. The Fukushima Daiichi incident is currently rated a five, the same as the 1979 Three Mile Island incident in the U.S., meaning there was a release of radiation to the environment because of a fire at the reactor core. ”

Wall Street Journal, link:


@Bill Bradshaw …”And the last point, which is what will make the difference in the end, is NOT that nuclear reactors are so dangerous, but that there is a limited amount of fuel available. It will run out. ”

I challenge you to demonstrate this statement or to provide some justification for it.

As has been previously canvassed elsewhere in this site, even if uranium is use only as a once-through nuclear fuel only, there is an abundance of orebodies with U3O8 at sufficient concentration levels for mining for 50-70 years at current consumption rates,
– plus many more being found as a result of current exploration,
– plus a reservoir of 4.5 billion tonnes U in the oceans of the world,
– plus huge reserves of Thorium which are currently being mined from mineral sands and discarded even though they have potential use as a fuel for Th reactors. [deleted comment on supposition of a person’s motives]
Bill’s personal opinion presented as fact has now been moderated and he has been asked to provide references to support his opinion.
We missed that one – before volunteer moderator engaged I think.



I have been thinking about something in the last few days that I would love some facts on.

In the middle of the 19th Century I understand that a solar flair that took out telegraph equipment and that in future we can expect this to happen with the result of some damage to circuits.

The question I have with the above in mind is two fold:

1, When a reactor shuts down automatically does it require systems to work to do this (what I mean to say is if you completely unplugged the power and the safety circuits failed , would the reactors shut down safely under mechanical means?

2, Once the reactor is in a safe mode, does it need systems to keep them that way? What I am saying is are we been fed a bit of a lie when they say ‘shut down). Do they not mean placed under a sort of life support?

I am just thinking about this because we have been told that the reactors in question were designed for around 5 meter Tsumani waves and they were hit by more then 10. Tsunami records show that this sort of event is likely sometime somewhere and in terms of history quite often. There is some certainty about Solar activity. Is this being considered.

In the case of a solar flair it would cause huge problems, however if the outcome is several nuclear facilities in trouble, could we expect the end of humanity?

I do not know what the Fukushima power plant will do in the long run, however we know the outcome of the tragic Tsunami. It has killed possibly 25,000 to 30,000. Maybe more. However in context of the world it is a very very small proportion (although very very tragic). Like the 2004 Tsunami that killed more people, the local people and the world will pick up again. This does not feel the same with Fukushima and the future of Nuclear.

Is there a serious organisation looking at all possible outcomes?


Eric: Good questions.
1. Reactor shutdown systems are designed to be FAIL SAFE on loss of power. That is, shutoff rods insert automatically on loss of electric power.

2. You are NOT being fed a bit of a lie. The chain reaction is COMPLETELY TERMINATED by insertion of the shutoff rods. The fuel rods produce some residual heat — steadily decreasing with time, like a dying bonfire. This heat is removed to control temperature, usually by circulation of cooling water. But in Japan, that enormous Tsunami swamped the emergency generators as well. This is the reason the recovery workers have had trouble with those plants.

A solar flare sometimes leads to loss of grid power. The emergency generators at each plant are designed to remove the residual heat – there would be no tsunami in such a case.

It is impossible for nuclear plant accidents to bring about the end of humanity. Foolish fears might well do so, I think.


Thanks Dan for your explanation and that is good news.

Is it not possible that backup generators can fail as they also use control circuitry that can be damaged.

I have not made up my mind on nuclear power as I do accept that I am ignorant when it comes to nuclear safety. I just find the information coming out totally bewildering and I don’t yet feel reassured.

About foolish fears.
Fair point about foolish fears although I am sure someone would have said “foolish fears” if someone else had questioned the safety of a nuclear power station in the modern nation of Japan before last week.

Anyway, thanks for your expectational and I look forward to a good outcome at the Fukushima reactor for all involved and for our children.


@ Leigh Bettenay and moderator

Firstly that the fuel will run out is fact. WHEN it runs out is something we can debate.

And to make a reasoned argument about that I would indeed need to point to some evidence of how large the ore bodies are and what our rates of consumption are going to be. It is interesting to note that you have NOT provided any evidence to back up your claim of 50-70 years supplies and some other unsuppored statement about 4.5 billion tonnes in the oceans of the world.

My opinion (and it was clearly stated as that) is that safety issues will not control the use of nuclear reactors but shortages of fuel (and the economics of obtaining that fuel) will eventually make the technology useless. And that is what I said.

Also using current rates of consumption for your guess at how long the reserves will last is showing that you do not understand the exponential function and what growth in economies and power consumption actually means. This is not the place to explain those things either.

I think that the cooling systems in some modern reactors are now of a more passive design so that they don’t need pumps to circulate the cooling fluids. Another sign that designs have been improving since Fukushima was built. Of course I can’t find the reference that I need to support that now.
“Firstly that the fuel will run out is fact. WHEN it runs out is something we can debate.”
This is the type of personal opinion presented as fact that BNC deletes and asks for re-submission with supporting references. Edited on Bill’s previous comment but left here as an example and answered by next commenter.


Thank you Tom Keen for that ref in answer to Bill – I was just about to go looking for a link. This common belief that we will run out of uranium has also been de-bunked by Barry here on BNC. BTW Bill was asked for a link to prove his thesis on his previous post. I guess he couldn’t find one:)


I am not sure how I ended up having to post so many times on this channel.
@Tom Keen – Thanks that article, it was an interesting read. There are some assumptions about using fast breeder reactors to burn all the worlds uranium deposits in that article but it reads well. The paragraph that made me feel better about fast breeder reactors was this one:
” Waste management is much easier with fast reactors because almost all of the long-lived nuclear waste products associated with thermal reactors are split by the fast neutrons. The radioactive materials remaining are of concern for less than 500 years.”

@ Finrod thanks for the link to your blog as well. I was wondering how we would get all that oceanic uranium and you have answered that question nicely (and I quote from your blog here):
” This would require 220 million tonnes of the adsorbent cloth, with a cross-sectional collection area of 24,000 square kilometres submerged under the sea.”

I am now convinced that the fuel will never run out…


@ Bill Bradshaw

The paragraph that made me feel better about fast breeder reactors was this one:
” Waste management is much easier with fast reactors because almost all of the long-lived nuclear waste products associated with thermal reactors are split by the fast neutrons. The radioactive materials remaining are of concern for less than 500 years.”

It is this feature of some Generation IV reactors that first won my support for nuclear energy too. That, and they can burn current spent nuclear fuel, and even waste left over from weapons production.


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