Nuclear Open Thread

Fukushima Open Thread 2

The last Open Thread dedicated to the Fukushima Daiichi crisis is getting overloaded, so here is a new one. Same rules apply:

The Open Threads on are a general discussion forum, where you can talk about whatever you like — there is nothing really ‘off topic’ here — within reason. Please use this particularly comment thread to post anything on the Fukushima Nuclear Accident that is NOT directly related to the content/intent of the other threads (which are usually about status updates, engineering details, specific perspectives, etc.).

The sort of things that belong on this thread include general enquiries, soapbox philosophy, meandering trains of argument that move dynamically from one point of contention to another, and so on — as long as the comments adhere to the general topic of nuclear energy, climate change mitigation, energy security, and the Fukushima crisis.

Please follow the commenting rules, although the ‘stay on topic’ rule obviously does not apply as strictly here.

Finally, a suggestion. There are often multiple trains of discussion going on, and a comment stream is not really the best way to manage this (a PHP forum would be preferable for this purpose — but we make do with what we have — this blog/website is not primarily intended as an undirected/unmoderated usenet-style listing). In lieu of this, I recommend that you preface your comment with a bold category word, so people can quickly ascertain what you are talking about, e.g. <b>radiation health physics</b> or <b>nuclear insurance</b> or whatever.

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.

236 replies on “Fukushima Open Thread 2”

Double breaches at Fukushima Daiichi No. 2?

The latest IAEA presentation shows Unit 2 “Core and Fuel Integrity” has jumped to “Severe damage” today March 29. Yesterday was same as units 1,2 = “Damaged”.

The RPV pressure reports are unit 1 = “Slightly increasing” (due to restricting core cooling water); units 2,3 = “Stable”. Looking for confirmation of Will Davis’ thesis, I’ve examined the reactor status reports for evidence of RPV pressure drop on unit 2. I don’t see it – TEPCO continues to operate unit 2 below one atmosphere – about 0.074 MPa, or 3/4 atmosphere absolute. I read unit 3 as stable around 1.3 atmospheres = 0.135 MPa. But if unit 2 is being operated below one atmosphere, why can’t the most of flow leak out of the RPV + primary into the secondary circuit?

Is stable 3/4 atmosphere RPV pressure consistent with most of the core coolant injection volume leaking into the trench? As I reported earlier regarding unit 3 leak concerns, nuclear chemist Cheryl Rofer observes that the pressure history indicates…

(…) If there is a leak, it is not a big one.

It’s not a big one, because reactor #3 has been pressurized. If you try to blow up a balloon with a big leak, nothing happens. You can blow up a balloon with a pinhole leak, though. The steel reactor containment vessel is equipped with pressure gauges to measure the pressure. With a big enough leak, the pressure wouldn’t rise, but it has been rising as water is pumped in and turns to steam.

So where is the radioactive water coming from?


But unit 2 is a different case if RPV is at relative negative pressure, right?


Douglas Wise, on 29 March 2011 at 6:51 PM said:
“Finally, we have been led to believe that fourth generation designs, operating at pressures not much greater than atmospheric, will be safer and will require less expensive containment. Does this conclusion require re-evaluation?”

This question can’t be answered for fourth generation designs in general because some contain highly flammable materials while others do not.

Personally, I prefer designs that have no need for flammable materials (e.g. MSRs, LFTRs and Sub-critical Reactors).

Reactors that contain large quantities of sodium (e.g. Super Phenix etc) have the potential for major problems if the sodium comes into contact with air or water.


re post by: EL, on 30 March 2011 at 9:32 AM said:

@ David Kahana or others, re Cl-38 in samples

You can find a full discussion (and lots of math) regarding transient criticality and Cl-38 in the sample water of reactor #1 here:

Click to access Cause_of_the_high_Cl38_Radioactivity.pdf

Comes from Arms Control Wonk blog. And you’ll notice Red_Blue has already had his/her say in the comments.

El, the author launches into all sorts of calculations without first looking at the big picture. If there were Cl activation, there would also be significant Na activation. No activated sodium was found apparently. Other short lived fission products that would be expected to be found in significant quantities weren’t either. That puts a rather large hole into the scenarios proposed in that paper, or in the idea of Cl-38 arising from a re-criticality.

I’ll cross post this over on the technical open thread where it would make more sense for us to continue discussions on this issue if desired.


EL, on 30 March 2011 at 9:32 AM said:

@ David Kahana or others, re Cl-38 in samples

You can find a full discussion (and lots of math) regarding transient criticality and Cl-38 in the sample water of reactor #1 here:

Interesting, it’s the kind of rough calculation I was attempting to do, but that I didn’t finish yet.

I found that it’s not that easy to make an estimate of the maximum possible Cl-38 equilibrum level, without knowing the actual geometry of the fuel, and the time history of the Cl-37 concentration since seawater injection was started.

He’s used thermal neutron cross-sections, which is fine, that’s a conservative assumption, it should overestimate any Cl-38 production from spontaneous fission. If there’s actually B-10 in the water though, he should use a fission energy averaged cross-section which would be smaller than thermal, and would lead to a smaller equilibrium concentration.

In one scenario he’s assumed that all the fuel has escaped the RPV, presumably by melting right through it despite the injection of all of the seawater, and that it is now sitting on the base of the primary containment, irradiating seawater which sits uniformly above it!!

I certainly doubt that this is an accurate picture, for many reasons: the simplest being that I think we should see many more strange isotopes than Cl-38 in the water if the RPV has been completely breached and corium has melted uniformly onto the bottom of the containment!!!

In any case this is not a conservative assumption. It certainly underestimates the Cl-38 production, and probably by a very large factor.

If instead, the core is somewhat damaged or even pretty severely damaged, say 20-50%, but has much closer to normal geometry, and is still inside the RPV, then the neutron irradiation of the coolant water will be far more effective (due to a far larger surface (fuel) to volume (coolant) ratio.

After all that’s how the reactor was designed to operate: it uses water (in the lower part of the core) and steam (in the upper part of the core) to slow the fission neutrons to the point where the induced fission cross-section becomes large enough to make the reactor critical, so just as many neutrons are lost from the core as are produced inside it. The interaction of the moderatpr with neutrons is far larger if the core geometry hasn’t changed very much. So too, is the interaction of the spontaneous fission neutrons with any impurities in the coolant much larger, if the reactor has close to normal geometry.

He does include a second scenario, in which the core has partially melted, and there are a few crevices through which fuel leaks, but I must confess I can’t really follow his reasoning in that case. He gives some discussion of what the U02 density would be at 3120 K. So then it’s all melted, I suppose. But surely 3120 K is not consistent with the temperature readings we’ve seen from the feedwater …

In any case, this scenario is also far from conservative, as concerns Cl-38 production
from spontaneous fission. I presume that Cl-38 production will be maximal when the reactor is completely undamaged. So it seems to me that that is the most conservative assumption to make.

This geometry question is actually the hardest part of doing a real calculation if the core is damaged. What does the flow around the core look like? What if there is salt precipitated out and sitting right on top of some of the fuel pellets which have fallen to the bottom of the RPV? What if some of the core melted, then was cooled and resolidified but some is still relatively undamaged?

Finally, the Cl-37 concentration could by now easily be 5-10 times higher than the concentration he’s assumed (that in seawater), due to constant evaporation of water into steam to cool the core, without evaporation of the salt it contains. It’s a boiling water reactor after all, so it has presumably still been boiling the water.

I also think he’s underestimated the fuel load: he quotes 69 tons of fuel, but I’ve seen numbers closer to 150 tons for a complete core. So his total spontaneous fission neutron flux is maybe a factor of 2 low.

Together, those alone would lead to a factor of 10-20 low for the Cl-38.

@Rational Debate:

Frankly errors of this nature sound far more likely to me than any chance of re-criticality – not to mention as others already have that then we’d be seeing other isotopes also that weren’t in the sample results, and the relative abundances don’t seem plausible, etc.

Yes, I still think this is a valid point, and I agree with the person you quote: there can be spurious peaks depending on the method. I do wonder how seriously we should take the Cl-38, since other isotopes were observed and then the observations went away on re-analysis. I don’t know exactly how they are doing the isotope analysis. Personally, I’ld like to vaporize a very small sample of the water pass it slowly through a mass spectrograph, and get a gamma spectrum for each mass fraction, but that’s surely not practical. It would be pretty definitive, though. Other methods may well have problems.


Given that historical Japanese tsunamis within the last 115 years have been as high as 23 to 33 meters, yet the Fukushima reactors were designed to only withstand a 5.7 m one is all that is really necessary to know about the state of nuclear reactor designs and nuclear power industry: [deleted personal opinion presented as fact. Please re-submit with refs backing your claim and deleted personal appraisals of the motives of others] Anyone claiming otherwise is not looking at the facts and dangers involved.

And as for the plant withstanding an earthquake significantly larger than it was designed for, the epicenter was some distance away. Who knows what the same sized earthquake with an epicenter much closer to the plant might have done. Given that the plant already had structural defects [deleted unsubstantiated claim. Re-submit with references], I wouldn’t count on it holding up.
Please check the BNC Commenting Rules before posting again.


re post by: David Kahana, on 30 March 2011 at 6:35 PM

David, recall that the salt also supposedly plates out/cooks out (sorry for the loose description) onto the fuel rods, adhering to the cladding. Think of a water heater element in a hard water area… and he deposition wouldn’t be even either, it’d be different for the water covered area v. the transition zone v the steam cooled area… all making your geometry problem even more difficult! :0)


@David Kahana —

If instead, the core is somewhat damaged or even pretty severely damaged, say 20-50%, but has much closer to normal geometry, and is still inside the RPV, then the neutron irradiation of the coolant water will be far more effective (due to a far larger surface (fuel) to volume (coolant) ratio.

Actually, not in his model (which greatly overestimates both Cl-38 production rates). His physical argument can be reduced to this: if there is only 1 drop of seawater in the entire core, and it is in the position of highest neutron flux, what is its equilibrium Cl-38 concentration? Because this concentration is an upper bound on the concentration in any resulting water, period. (It’s a very loose bound: particularly in the slab geometry, where most of the water sees a neutron flux far lower than the maximum. Also he leaves out shielding.)


USA Sending in Marine Team !!!

The US military is sending Marines specialized in responding to nuclear emergencies to Japan to help deal with the trouble at the Fukushima Daiichi nuclear plant.

Japan’s Self-Defense Force Joint Chief of Staff Ryoichi Oriki announced the measure on Thursday.

Oriki said US Defense Secretary Robert Gates has approved the sending of the 140-member Chemical Biological Incident Response Force.

The unit is trained in search-and-rescue operations and clearing highly radioactive nuclear materials.

Oriki said the unit will not necessarily take immediate action, and that the Self-Defense Forces hope to share information with them and study how it can be put into use when needed.

The US military has provided a barge capable of carrying large volumes of fresh water to keep reactors at the plant cool. It has also sent nuclear experts to Japan as part of efforts to resolve the crisis.
Thursday, March 31, 2011 19:36 +0900 (JST)



His physical argument can be reduced to this: if there is only 1 drop of seawater in the entire core, and it is in the position of highest neutron flux, what is its equilibrium Cl-38 concentration?

Thanks for that: on re-reading his calculation, I see you’re right: that is his reasoning.

It’s actually not a bad way to proceed, if one just wants to get some kind of upper bound.

I just didn’t imagine that anyone would try to make a calculation without including effects of dilution, due to coolant flow and shielding of the neutron flux, both of which will certainly reduce the equilibrium Cl-38 concentration.

So if he’s correct about the neutron flux from spontaneous fission, we can dismiss outright the possibility that that was the source of the Cl-38.

By now, though, we’ve already heard from TEPCO that there were errors in their analysis programs for some of the radioisotopes, so I’m inclined to think the CL-38 measurement is also spurious.

“Groundwater at the crippled Fukushima Daiichi nuclear power plant is highly likely to be contaminated with radioactive materials, even though its operator Tokyo Electric Power Co. is reviewing its analysis released late Thursday due to erroneous calculations, the government’s nuclear safety agency said Friday.”

“The agency said the density readings of radioactive substances in groundwater samples taken on Tuesday and Wednesday from around the No. 1 reactor’s turbine building may be revised downward, as TEPCO’s evaluation programs for materials such as tellurium, molybdenum and zirconium were found to have errors.”


> Marines


—excerpt follows—-

“… military official characterized the deployment as “prudent planning,” a precautionary move to have the Marines on hand if needed, not an emergency.

The team is “an initial response force,” the official added, because it is only one part of the larger CBIRF unit based at the Indian Head Naval Surface Warfare Center in Maryland.

“They would provide radiological expertise to the on-scene commander and, if needed, to the JSDF (Japan Self-Defense Forces) in the areas of medical, logistical, chemical, biological, nuclear and hazardous materials,” the official said.

The unit is specially trained to counter the fallout from a chemical, biological, radiological, nuclear or high-yield explosive (CBRNE) incident, usually assisting local, state or federal agencies in their response.

On March 17, Admiral Robert Willard, who is overseeing American military assistance after Japan’s earthquake and tsunami, said 450 radiological and disaster specialists were awaiting orders to deploy as Japanese teams tried to cool fuel rods in reactors at the damaged Fukushima plant.

Rear Admiral Scott Swift, director of operations at US Pacific Command, said that around 15,000 US personnel were taking part in the round-the-clock relief operations since the disaster began as part of a mission dubbed Operation Tomodachi, or “friend.”


“Four more concrete pumping trucks are on their way to the Fukushima Daiichi nuclear power plant to help the effort to maintain fuel ponds.

Having overheated and suffered serious drops in water level, the used fuel ponds in the upper parts of damaged units 1, 3 and 4 were refilled by a number of ad-hoc means.

First came ineffective drops by helicopter, next was spraying from fire trucks. The situation was brought closer to control with the arrival of Hyper Rescue and Super Pump Truck from the Tokyo Fire Department, but it was an extra-large concrete pumping machine that has been most effective, particularly at unit 4 where steelwork obstructs spraying from the ground.”

These are Very common in the Midwest. They are used all the time to pour long bridge decks – so I am surprised they are not readily available in Japan – with all the construction they have had with their infrastructure in the past 10 years.


As many have posted previously, this site has been an oasis of reasoned discussion and relatively digestible information during the ongoing Fukushima crisis. I started out reading Huff Post (so saturated with doomsayers and [ad hom deleted]that my hair was standing on end!), so this site became my calm center in the midst of all the inflammatory hype and/or dismissive happy talk.

I have had a question for a while now and was wondering if any of the regulars could answer it. Are there high-exposure suits for nuclear workers to wear when they have to go into really “hot” contaminated areas? I keep thinking, we had suits for space travel and for men to walk on the moon–surely someone has invented a similarly protective suit for nuclear emergencies. Yet all I see are the workers in those flimsy Tyvec coveralls, with skin exposed on their faces. So are there “extreme” suits and if so, why aren’t they being utilized? (And if not, why hasn’t someone invented them??)

In a related vein, I read an article where a company in Florida that makes radiation-blocking suits (not, I gather, the extreme type I mentioned above) was sending them to Japan. They are black, like scuba suits . . . but I have yet to see any photos of workers wearing them. I hope they are not sitting on a dock somewhere . . .


Nancy, in brief – the suits do an excellent job at blocking particulates, which can be ingested and cause internal damage via alpha or beta emissions. But, they can’t stop the highly-penetrating gamma rays. The only thing really effective for this is lead or similar robust blocking material. That’s one of the reasons why nuclear-powered aircraft turned out to be such a hassle — the shielding is so heavy.


Barry, thanks so much for responding. I just checked out the website for the company that makes these black suits . . . and according to them, the fabric does offer some protection from gamma rays.

“The Demron fabric has been proved to provide multi-hazard protection against gamma rays, chemical and biological threats and X-rays by the Lawrence Livermore National Laboratory and Pacific Northwest National Laboratory (PNNL), GEOMET, and Kansas State University.”

It’s kind of ironic, but before March 11 I was strictly anti-nuclear and now, after doing a lot of research and discovering how very grounded many of those in the industry are, I am starting to be more open minded. Overall, I believe the industry needs to start “airing their dirty laundry” (well, maybe Japan did that for them) instead of always insisting that everything is hunky dory. As a long-time environmentalist (and co-author of “The Earth Friendly Home,”) I can see the merits of nuclear power right now. But as a realist, I can also see the huge obstacles that other renewables don’t present. My best hope is that nuclear becomes an energy bridge until other technologies, ones with far less toxic waste products, are feasible and practicable.


Apparently, Helen Caldicott’s “Nuclear Power is Not the Answer” is published by New Press in the US. I am sure it was originally published by Melbourne University Press, though. Is it common to have two different publishers?

Maybe MUP dumped her after they realised they were putting their good name on her anti-scientific crap?


> highly-penetrating gamma rays.
> The only thing really effective for this is lead

A nurse who taught new doctors how to handle patients treated with radioiodine did a demonstration — she’d hold a Geiger counter over the patient and show the residents the counts from the gammas.

Then she’d say ‘how many of you would prefer to wear the radiation shielding?’ — and they’d all say yes.

Then she’d hold the radiation shielding suit between the patient and the counter, and the counts would go way, way up — secondary particles coming out of the back side of the lead shielding.

Then she’d teach them how fast high energy gammas mostly just go right through you without interacting with tissue, which is why the dose to the thyroid to kill off thyroid cancer is so very high — and how when you interpose a lead shield, the massive lead atoms make much bigger targets and the gammas interact far more — throwing out lots of secondary radiation after the collisions.

Then she’d ask them again.


Fukushima update: Data, data, everywhere…

Academic researchers worldwide, including veterans of research on the Chernobyl accident, are poring over releases of data on population exposure rates to radioactive fallout from the Fukushima nuclear disaster. But they are finding that making any sense of the data is proving very difficult.

One problem is that data are strewn across many individual web pages on several websites, for example, those of Japan’s science ministry, here and here, the health ministry, the Nuclear and Industrial Safety Agency,and the International Atomic Energy Agency. Moreover, the data are often in different units, with few descriptive details of, for example, sampling techniques used.

The Japanese government does appear to be making efforts to be open about data, though. Summary maps (provided by the US Department of Energy) of aerial radiation monitoring have also been extremely useful, researchers say, though no geographical information system data of the maps is available from the website.

“The problem is that it is very difficult to get a real picture of the exposure of the population,” says Elisabeth Cardis, a radiation epidemiologist at the Centre for Research in Environmental Epidemiology in Barcelona, Spain, “I’ve been poring through many reports from many different bodies, and the information is very confusing.” Measures for the same zone sometimes differ greatly between reports, and it’s not made clear how measurements were made, she says. There’s a need for a critical review of all the available data, she says.



Tepco, like most power companies that operate nuclear reactors, is a public corporation with a sworn charter to protect investor capital. Can the company financially survive a nuclear accident? This will be a case study in corporate financial risk management for power companies around the world.

Tokyo Electric Power Company turns toxic

As engineers continue to fight to prevent catastrophe at the tsunami-hit Fukushima nuclear plant, executives at its controversial operating company are also struggling to prevent a financial meltdown.

Shares in the Tokyo Electric Power Company plunged again on the Nikkei stock index yesterday. They fell 18% to a 60-year low of ¥362 and the company said it was delaying publication of its annual earnings report due to the crisis.

In Tokyo, the air is thick with talk that Tepco might have to be nationalised as losses mount and investors brace themselves for compensation claims running into billions.

Government intervention could leave investors out of pocket, sparking outrage in a country where capital has been king since the end of the second world war.

The omens aren’t looking good as the human and environmental tragedy grows worse by the day and the Japanese lose faith in their nuclear industry.


Even as it struggled to contain the the world’s worst nuclear disaster in a quarter-century, Tokyo Electric Power Co. late last month quietly set out big plans for the future: It proposed building two new nuclear reactors at its radiation-spewing Fukushima Daiichi power plant.

Tokyo Electric, known as Tepco, informed Fukushima prefecture on March 26 of its desire to start building the reactors as early as next spring, local officials said. That was just two weeks after an explosion at the utility’s tsunami-crippled complex set off a cascade of catastrophes.

The proposal was then included in a formal report submitted to authorities in Tokyo on March 31 as part of an annual process designed to assess Japan’s future electricity supply.

“It was just unbelievable,” said Yoichi Nozaki, director general of Fukushima’s Planning and Coordination Department, which oversees energy matters here in the capital of the region most blighted by the the biggest nuclear debacle since Chernobyl.

With its reputation and its finances already shredded by the events at Fukushima Daiichi, Tepco now has another fiasco to contain. Its proposal for new reactors, first reported Sunday in a local Fukushima newspaper, has caused horrified dismay — and significant backpedaling by Tepco.

“It was a mistake,” Hiroshi Aizawa, a Tepco official in Fukushima, said Monday. He said the company had been too busy trying to get Fukushima Daiichi under control and avoiding power cuts to revise a plan that took shape before the March 11 earthquake.

The disarray — on full view just as BP seeks to re-start drilling in the Gulf of Mexico, the scene of a spectacular blowout last year on a rig leased by the oil giant — has sharpened a question dogging Tepco since a tsunami slammed into its Fukushima Daiichi plant: Has the scale of the disaster triggered a managerial meltdown or is the world’s largest private electricity utility simply sticking to the aloof, heedless habits of a corporate behemoth accustomed to getting its way?

“I don’t know what they’re doing,” Nozaki, the Fukushima planning chief, said of Tepco’s executives. “Ask them!”


If you’ve got a bloody great tank of thousands of tonnes of molten potassium nitrate at 500 degrees C and you hit it with an extremely strong magnitude 9.0 earthquake, what happens?

I’d really like to know if those who claim that solar thermal can and should replace all fossil fuels in the exclusion of all nuclear energy can give me any kind of answer to that.

In the absence of any better analysis, I would estimate the answer is that it will set everything for miles around on fire and burning extremely aggressively, releasing an enormous plume of very toxic nitrogen dioxide.


Came across a table of core shroud repairs that’s perhaps of interest, here:

(found that after noticing that Fukushima Unit 4 shutdown was preparation for replacing its core shroud, and that Unit 3 had the very first core shroud replacement ever done); those are cited over in the thread


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