Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[AntonL]

I
I think that the Reactor pressure sensors are compromised, on likely dead.
the Down scale indicated a dé pressurization of the PCV.
taking into considération the recent leak , It seems possible that both PCV and and Reactor are both compromised since the 20th

It must be a relative slow leak, I would imagine a valve not holding the pressure
and now the contaminated steam is escaping, which condenses to the water
the basement acting as a containment area.

 

[havemercy]

Sorry to step back regarding the neutrons. I heard that the water has the effect to slow down the speed of the neutrons.

If this is correct, in the Spent Fuell pool, the neutrons with high speed will go through the fuell without making contact with the fuell and thus reduce the nuclear reaction.

If they add water, it will reduce the speed of the neutrons that will making more contact with the fuell and then increase the nuclear reaction.

The fact to put water in the pools will accordingly have the effect of making more nuclear reaction, isn't it correct ?

 

[|Fred]

It must be a relative slow leak, I would imagine a valve not holding the pressure and now the contaminated steam is escaping, which condenses to the water
the basement acting as a containment area.

I edited my post as I did not gave it enough sensible thoughts :)

 

[jlduh]

@Havemercy: my understanding is that water (not bored of course) increases the reaction and that steam reduces it, and that this is a way to control the reactivity and the reactor in a BWR. But answers from specialists would clarify that...

 

[Maclomer]

In all of the reactors (setting aside the spent fuel pools) the absolute imperative is to maintain cooling by whatever means is feasible and, however it is done, active cooling will probably be needed for many months.

Right now we know some of the cooling is done by directing water jets onto the exterior of the containment and the runoff will go into the ocean. If the containment is breached, that runoff will be radioactive so then there is bound to be a continual emission by this route. Unavoidable.

Now my question:
To what degree is cooling water, and so it seems, seawater, being injected directly into the cores (for example Number 3) and is this water is being heat-exchanged in a closed loop; or are they injecting the water and then allowing the steam to escape (people have commented here about salt build-up)?

I ask this because, at the same time, we hear about 'restarting the cooling pumps', especially for Number 3, using this newly laid power line, which implies to me that an intact cooling loop with proper heat exchange may still be possible, at least for some of the reactors.

 

[Gilles]

I think water in general increases the reaction rate by slowing neutrons. It's just that water vapor is much less dense than liquid, so the effect of steam is to decrease the rate relative to liquid water (negative void coefficient). In reactors using graphite as a moderator like RBMK , it was positive , because water acted essentially as neutron absorber and not as a moderator. That's the same for Pu-Na fast breeder ...

 

[|Fred]

Reactor 1 (not compromised) but under heavy stress
Reactor 2 stabilized (may be wishful thinking)
Reactor 3 (compromised, not necessarily the vessel it self may be only in the pipe of the cooling system and the containgment)

 

[artax]

There's a long but interesting doc. here on spent fuel storage (wet and dry):-

http://www-pub.iaea.org/MTCD/publications/PDF/te_0944_scr.pdf

 

[TCups]

Studied some nuclear chemistry at uni a long time ago hence my interest but I would have to research those isotopes.
However the news here did mention that the ALLOWED UK levels for infants in tap water used for drinking (making up milk) are 5 TIMES HIGHER than those allowed in Japan... so I wouldn't worry at all.
The main reason Iodine is important is because the body has some in it always (thyroid gland) and can't tell the difference between the active isotopes and the natural ones. So if you take the Iodide pills, the iodide atoms (ions) just displace the radio ones very quickly before they've been their long enough to have any effect.
I'm pretty sure the authorities are tellining the truth about the tap water, and washing with it will be no problem at all... and drinking!
If I was in Japan now, I would just avoid the exclusion zone and don't go swimming in the sea!

RE: IODINE PILLS & IODINE UPTAKE BY THE THYROID

Normal iodine will not, I believe, displace radioactive I-131 that has already been taken up by the thyroid gland. The purpose of the iodine pills is to effectively flood the normal biologic uptake of trace amounts of iodine with the normal, non-radioactive isotope, and suppress any further uptake of iodine, ie, radioactive iodine, by the thyroid. After a large dose of RAI (radioactive iodine), potassium iodide will do little good.

 

[Reno Deano]

Thanks Reno, so your explanation is that it's because there was no power available...

So the only vent they could open was inside the building, there was none actionnable toward the outside (what a pity...). Then that was a constraint, not a choice (like to avoid radioactive venting outside), right?

Are we talking about a valve that a man had to actionnate physically being close to it?

The reason why I'm asking these questions is that it seems that a modification has taken place in the US after the TMI accident under the NRC requirement, with the installation on all BWR reactors in the US of a so called "hardened vent" which is a direct realease to the atmophere to depressurize the containement. THis was to avoid precisely H2 release inside the building. Then the question is: did the japanese had this hardened vent? I have the impression that these vents are the big structures (like antennas) that we see close to every reactor (right or wrong?) but in this case it means that they still couldn't activate them because no power (seems not to "hardened" to me but...).

The Reactor Accident off gas system (shielded filtration - carbon and HEPAs) is within the reactor building. I am assuming it worked until the station black out. Then the valves failed shut. I do not know if they had hydrogen igniters on the system (but doubt). The system is located above the reactor vessel level of the plant. That could have been the location of the first expolsions and when damaged the gas vented naturally to the reactor building via numerous paths, eventually finding their way to the top of the reactor building (reactor work platform area). The other off-gas system is the normal one that allows filtration and decay of radioactive short lived gases and is generally under ground with a long decay loop before heading for the stacks. I have inplant experience with several of the BWR models, but am getting long in the tooth, and my memory gets sketchy at times. Also, I have little patience with conjecture based on hearsay and not facts.

The beta exposures while high are not approaching any significant Equivalent Whole Body Dose. Cobalt therapy cancer patients received significant burns of their skin when treated. Since the workers dosimetry did not likely measure beta radiation, the concern was based on isotopic knowledge of the radioisotopes in the water and the large penetration radiation component, and the fact that their boots were full of water. Beta exposure is measured in Grays anyway and depending on the amount of skin involved (largest organ of the body) is converted to Equivalent Whole Body dose at some later time, if significant.

 

[Astronuc]

Sorry to step back regarding the neutrons. I heard that the water has the effect to slow down the speed of the neutrons.

If this is correct, in the Spent Fuell pool, the neutrons with high speed will go through the fuell without making contact with the fuell and thus reduce the nuclear reaction.

If they add water, it will reduce the speed of the neutrons that will making more contact with the fuell and then increase the nuclear reaction.

The fact to put water in the pools will accordingly have the effect of making more nuclear reaction, isn't it correct ?

The spent fuel pool is there to store the discharge fuel for some period of time to allow the fuel to cool down thermally (allow decay heat to dissipate) and to allow the decay of short-lived radioisotopes (to reduce the radiation levels). The SFP also must provide for full core offload, which includes the reinsert fuel (fuel to be returned to the core), as well as the discharge fuel.

Water also provides shielding from gamma and beta radiation.

Water is also a moderator. A moderator slows fast neutrons to 'thermal energies' (mean neutron kinetic energy ~ 0.025 eV or speed of 2200 m/s). The fission cross-sections of U-235 and Pu-239 increase as the neutron energies approach the thermal energy of ~0.025 eV.

However, the SFP is designed to be subcritical. The walls of the spent fuel pool contain neutron absorbing material, usually a compound of boron with B-10, e.g., boraflex or boral. The water in the SFP can be borated, but in theory the SFP should be designed to remain subcritical if all the water is pure, i.e., without any boron, particularly for BWRs by design. As long as the boron in the walls of the spent fuel pool remain intact, the pool should not be able to achieve criticality.

For BWRs, the water in the SFP is the same as the water in the reactor cavity when the core is open for refueling. Movement of irradiated fuel is done with the fuel underwater - at least 7 m or so, as the reinsert and discharge fuel is moved between the core and SFP. Boric acid is not used in BWRs, so the SFP water would not contain boron.

 

[Astronuc]

Now my question:
To what degree is cooling water, and so it seems, seawater, being injected directly into the cores (for example Number 3) and is this water is being heat-exchanged in a closed loop; or are they injecting the water and then allowing the steam to escape (people have commented here about salt build-up)?

I ask this because, at the same time, we hear about 'restarting the cooling pumps', especially for Number 3, using this newly laid power line, which implies to me that an intact cooling loop with proper heat exchange may still be possible, at least for some of the reactors.

Ideally the cooling systems would remain closed, but that may not be the case where the units are venting steam. In addition, if there are open valves, then water may be leaking out. Leaking would certainly be the case if any of the piping, valves, or pumps, attached to the primary systems has ruptured.

Using seawater is problematic from the standpoint of corrosion, as well as the salt. Corrosion products can be transported in the primary circuit and attached systems. Salt may concentrate in areas where boiling/evaporation occurs. Salt and corrosion products may deposit in valves and seals, thus preventing the tight closing of valves or undermining the seals.

 

[Reno Deano]

Neutron Beams. During fission neutrons are scattered 360 degrees. As Astronuc can confirmed it takes a collimator to focus and make a "neutron beam". Also, the location of the various sources of neutrons (core and SFP) provides significant attenuation of neutron external to the sources. As much Boron as there is in both locations a neutron beam is highly improbable. Side Note: When we were starting up naval reactors for the first time, Rickover would bring out the first neutron to start the plant. :-)

 

[jlduh]

I would like to draw your attention to a last remark i just made (and it probably answers a question I've had for some time looking at the images of the ruins of the reactors). Looking from outside of the reactors, we assumed maybe that they are centered in the middle of the reactor building. I've seen variations on the differents schematics that have been posted around but if the drawing that the scientist from Tokyo University showed at the NHK is correct, which i believe it is, then it confirms that THE REACTOR IS NOT AT THE CENTER OF THE BUILDING VIEWED FROM THE TOP, but pushed towards the turbine building (because the east side of the torus below the ground is actually below the connecting building and not below the reactor building). So the reactor head is shifted towards the East (toward the sea).

Now we can try to speculate if the smoke plume from this building is coming from this place or not, but if think it is (satellite picture just after the explosion, 14th or march):

http://www.netimago.com/image_182152.html

http://www.netimago.com/image_182153.html

 

[jlduh]

@TCUPS: did you have a look at my post just above yours and at my other post with the big captures of the drawings on the NHK TV at page 72 of the thread?

Because i think they answer some of your questions concerning the basement, the location of the workers and water, the location of the basement relative to sea level,and confirms also your remark concerning the shift of the reactor towards the East side of the building, and the corresponding smoke position...)

 

[Reno Deano]

From NEI: http://nei.cachefly.net/newsandevents/information-on-the-japanese-earthquake-and-reactors-in-that-region/health-and-radiation-safety/"

Excerpt:

What the Experts Are Saying

"The fear is out of proportion to the actual risk right now. With regard to health effects, probably the largest effect will be psychological." (CNN)
-John Boice, Vanderbilt University epidemiologist

"Fear dominates our intention. The earthquake and tsunami are over, but with nuclear energy, who knows? We are used to thinking of industrial accidents, but with nuclear we are talking about what could happen. I cut my teeth on Three Mile Island, because there was a sense that we almost lost the Eastern part of the U.S. The biggest health problem from Three Mile Island was fear, the anxiety and mental stress that people had." (NPR)
-Dr. Robert DuPont, Georgetown University professor of psychology

"The fact that they can detect something doesn't mean it's harmful. It's important to understand that difference." (USA Today)
-Richard Morin, American College of Radiology safety committee chair

"This is indeed a really serious event, but it has to be put in the context of the earthquake and tsunami which led to it - and which has been the direct cause of massive suffering, which is still continuing. Obviously there are threats from the nuclear power station, but they are limited and they are quantifiable. It's not a Chernobyl. ... One of the biggest risks from radiation is the psychological damage it causes. After events like the 1979 partial meltdown at Three Mile Island, Pennsylvania, and the Chernobyl accident, there was substantial psychological trauma, even among people who were not affected, because there is such a fear of radiation and its long-term consequences." (New Scientist)
-David Spiegelhalter, Winton Professor of the Public Understanding of Risk at the University of Cambridge

 

[TCups]

@TCUPS: did you have a look at my post just above yours and at my other post with the big captures of the drawings on the NHK TV at page 72 of the thread?

Because i think they answer some of your questions concerning the basement, the location of the workers and water, the location of the basement relative to sea level,and confirms also your remark concerning the shift of the reactor towards the East side of the building, and the corresponding smoke position...)

Sorry, jlduh - my long post apparently pre-occupied me while you were posting. I have read your post now. It seems your image links will only come up as very small thumbnail images. These are not sufficient to make your point.

I will check page 72 . . .

 

[83729780]

Has there been any conformation of the exact location of "the basement in building 3" that was so contaminated? Does this mean the basement of the Reactor Bldg 3 in the region of the torus? Does this mean the basement of the Steam Turbine Bldg 3? Is there a basement in the region of the control room? I have not heard where the infamous basement is located.

It was in the basement of the turbine building (the one with the huge hole on the roof).

this from the NY Times:

But Michael Friedlander, a former nuclear power plant operator for 13 years in the United States, said that the presence of radioactive cobalt and molybdenum in water samples taken from the basement of the turbine building of reactor No. 3 raised the possibility of a very different leak.

Both materials typically occur not because of fission but because of routine corrosion in a reactor and its associated piping over the course of many years of use, he said.

These materials are continuously removed from the reactor’s water system as it circulates through a piece of equipment called a condensate polisher, which is located outside the reactor vessel. The discovery of both materials in the basement suggests damage to that equipment or its associated piping, as opposed to a breach of the reactor vessel itself, Mr. Friedlander said.

The condensate polisher is also located in the basement of the turbine building, where the tainted water was found. By contrast, the reactor vessel is actually located in a completely different, adjacent building, and would be far less likely to leak into the basement of the turbine building.

http://www.nytimes.com/2011/03/26/world/asia/26japan.html?pagewanted=2&hp

I'd like someone to comment on the possibility that the very heavy (and hot) debris that smashed through the turbine building also ruptured the pipes through which the coolant water is circulating.

 

[Joe Neubarth]

Good point -- yes, there was that source of water, also. ()

I had heard that the Turbine building was not flooded earlier. So the question is where did the water come from all over again. That reactor Three explosion was a hellofa release of energy. Cracked foundation with seepage is a possibility. Some of that seepage could have been highly radioactive.

 

[Joe Neubarth]

Sorry to step back regarding the neutrons. I heard that the water has the effect to slow down the speed of the neutrons.

If this is correct, in the Spent Fuell pool, the neutrons with high speed will go through the fuell without making contact with the fuell and thus reduce the nuclear reaction.

If they add water, it will reduce the speed of the neutrons that will making more contact with the fuell and then increase the nuclear reaction.

The fact to put water in the pools will accordingly have the effect of making more nuclear reaction, isn't it correct ?

Water does slow down the neutrons so that they cause more fissions with Uranium. An outsider like me can only assume that they have some neutron suppression like boron in the water normally.

 

[TCups]

Water does slow down the neutrons so that they cause more fissions with Uranium. An outsider like me can only assume that they have some neutron suppression like boron in the water normally.

I don't think there is any way that spraying water or even immersion in water (as in the SFP) would risk "criticality" and a spike in radiation from a nuclear chain reaction. On the other hand, the danger of not spraying water and cooling the rods would be damage to the rods and more release of radionuclides from the damage rods. The former is a non-problem, the later is very real and potentially very dangerous. The added potential danger from spraying water might be spreading radionuclide contamination from the run off.

 

[TCups]

I had heard that the Turbine building was not flooded earlier. So the question is where did the water come from all over again. That reactor Three explosion was a hellofa release of energy. Cracked foundation with seepage is a possibility. Some of that seepage could have been highly radioactive.

see 83729780's post #1167. The contaminated water contained radioactive Co and other trace radionuclides implicating a "polisher" unit and suggesting leakage from internal plumbing coming from the reactor, into the Turbine building caused the flooding in the basement of Turbine Bldg 3, I believe.

Still, this might only imply significant damage to "plumbing" coming from the reactor vessel rather than to the reactor vessel itself, though I am not sure that is much of a comfort.

The point, if I understand it, is that if the damage were to the "plumbing", and if this were the source of the contaminated waters in the basement, and that if it occurred within the Turbine Bldg 3 rather than the reactor, then the mechanism of damage might be very different from damage within or around the RV and primary containment of Bldg 3.

 

[artax]

I still find it hard to believe they've not sent a Radio Controlled helicopter/camera in!
They could get right in there, crikey it's been two weeks now!
I could get better images with a 200 dollar chopper/my casio EXILIM and a bit of gaffer tape!

 

[KateB]

I don't think there is any way that spraying water or even immersion in water (as in the SFP) would risk "criticality" and a spike in radiation from a nuclear chain reaction. On the other hand, the danger of not spraying water and cooling the rods would be damage to the rods and more release of radionuclides from the damage rods. The former is a non-problem, the later is very real and potentially very dangerous. The added potential danger from spraying water might be spreading radionuclide contamination from the run off.

From what I understand, after the Spent rods are exposed and begin heating again, the addition of water could, in theory, instigate a recriticality. But it is a catch-22, because if you don't introduce water, then you could have an uncontrolled criticality/heating, that unchecked could become another source of worry, i.e. corium. It worried me that the water that was dumped from the Chinook obviously was sans Boron, as with it, the water is less a modulator and more a coolant. Correct me if I am wrong. Thanks for the great information, everyone.

 

[TCups]

http://www.nytimes.com/2011/03/26/world/asia/26japan.html?_r=1&hp" suggests that radioactive water comes from the condensate polisher:

In the extended quote of M. Friedlander, (post above):

"He said the company had found the same problem with contaminated water in the basements of the No.1 and No. 2 turbine buildings as that which caused the men’s injuries in the No. 3 unit. Removing the radioactive water will delay the work of restarting cooling systems."

This, of course, would mean that the holes in the roof of Turbine Bldg. 3 are NOT related to any of this, and that salt water and the resulting build of of NaCl and perhaps CaCO₃ may be significant in explaining what has occurred, as I believe, others have posted.

This would seem to imply

1) that sea water was used as a coolant inside the RV's, which I believe is the case,
2) that at least to some extent, given the basement contamination in the Turbine Bldgs of 3 separate units, that loss of integrity of the contents of the reactor vessels has occurred in Units 1, 2, and 3

Am I following correctly?

Addendum:
Might it also imply that the most direct route to restoring circulating fresh water cooling, perhaps the only route to restoring fresh water cooling, is by access to the now highly contaminated basements in the turbine buildings?

 

[AntonL]

Today is day 14 since the accident.

Google "Nuclear experts specialist fly to Japan" and nothing of relevance is returned.
Why has a international nuclear expert community not arrived in Japan, helping TEPCO
to analyze the data and brainstorm best actions.

I personally feel that Tepco engineers are overextended, paralyzed and firefighting,
instead of having a set clear path of action with small deviations to solve the problem.
The question now arises if nuclear reactor accidents should be co-managed internationally,
an new task for the United Nations as they are the only body to enforce this.

This accident will pose many questions. Such as why was the sea water injection allowed to
continue so long? To keep the reactors at constant temperature by latent heat of
evaporating water, would have by now consumed 7100m3 this is on average two 10T tanker
trucks every hour over the period - that is manageable. Now about 210 tonnes of salt is
distributed in 3 reactors.

This picture tells everything: Overwhelmed Tokyo Electric Power Company Managing Director
Akio Komiri cries as he leaves after a press conference in Fukushima (18/3/2011),
(and Japanese usually do not show emotion publically)

 

[tortamuss]

The Leidenfrost effect keeps popping into my mind. Any thoughts?

 

[AntonL]

I still find it hard to believe they've not sent a Radio Controlled helicopter/camera in!
They could get right in there, crikey it's been two weeks now!
I could get better images with a 200 dollar chopper/my casio EXILIM and a bit of gaffer tape!

It is not in public interest to show high resolution pictures, I am sure these they have, that
what they are releasing is to show that they are working hard. The general public is not
educated and believes what is fed to them, if they told it is OK then it is OK. The PR machinery
is hard at work to keep a sense of calm.

 

[AntonL]

Addendum:
Might it also imply that the most direct route to restoring circulating fresh
water cooling, perhaps the only route to restoring fresh water cooling, is
by access to the now highly contaminated basements in the turbine buildings?

Cooling by latent heat of evaporating water is not a long term solution as
the steam has to go somewhere. If the reactors where running 80% capacity
at the time of the accident then the heat generated by the decay of the
fission products would be 3.9MW for unit 1 and 3.9MW for units 2 and 3 today
and reducing to 0.7 and 1.2MW in half a years time. External cooling by circulation
and heat exchanger is the only solution, and with all that salt circulation of
fresh water is not possible, the salt is there to stay.

http://www.nrc.gov/reading-rm/basic-ref/teachers/03.pdf" an explain how the salt should be removed

 

[TCups]

ADDITIONAL INFORMATION ABOUT CONTAMINATED BASEMENT FLOODING

Source: http://www.world-nuclear-news.org/RS_Fukushima_Daiichi_two_weeks_on_2503111.html

QUOTING, IN PART:

"Investigations are now underway into the unexpectedly high level of contamination in the water, particularly as the basement of the turbine building is not a recognised radiation area. One theory is that there is a leak from the reactor circuit, but pressures in the reactor vessel indicate this must be elsewhere in the loop."

Added emphasis is my own. Elsewhere in the loop, indeed.