Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Borek]

Oh, and a quick and silly question: p. 25 of your course an element which has a very high moderating ration is noted D, and later D2O. Couldn't find a D on my Mendeleiev Table...

H for Hydrogen, D for Deuterium, T for Tritium.

 

[jim hardy]

PLG

it'll soak in over next few says as your brain chews on it while sleeping.

You have it - Keff < 1 means the chain reaction is progressing toward smaller numbers.

a chain reaction is exactly analogous to a "chain multiplication" on a calculator.
Enter any number, multiply it repeatedly by some Keff that's near 1.

EG 10 X 1.000 = 10 forever, you can multiply that all day long. That's exactly critical with neutron population 10.
Similarly 1000 X 1.000 = 1000 forever, and 1E14 X 1.000 = 1E14 forever.

Now 10 X 1.0001 = 10.001, next time 10.0020001, that is slightly supercritical because Keff 1.0001 which > 1 and neutron population grows.

Indeed when fission tapers off you have only radioactive decay.
Indeed the "D" is deuterium, heavy hydrogen. It is preferred moderator because it has little appetite for neutrons.
Light hydrogen atom is prone to absorb an occasional neutron and become heavy hydrogen; that neutron is unavailable to fission process. Deuterium is less likely to grab a neutron and become tritium...but it can
Here's a handy periodic table
http://environmentalchemistry.com/yogi/periodic/H.html
select any element and click 'nuclides'

if you're not familiar with "chart of the nuclides", pls advise i can pm you an intro no need to clutter board with it.

Do you see how simple they made reactor physics? Those four factors they arranged to all be close to 1, when you multiply them result tells immediately whether you are K< 1 > .
Fuel pools here are by regulation designed for K<0.95, and a BWR core with all rods in is <0.9.

Yes you got it right. Ask your nuke friends about chart of the nuclides
i use this one but there's plenty around 'net...
http://www.nndc.bnl.gov/chart/reColor.jsp?newColor=dm

glad you're enjoying.

 

[nikkkom]

Many people probably won't agree with me, but I tend to say that I simply don't care for any (sea)water contamination. It's really of absolutely no concern if you compare it to the damage which airborne releases can do and obviously have done (100.000-150.000 displaced people).

Radioactive water leaking in the underground will either reach the open sea where it dilutes or it will contaminate the local groundwater - which makes no difference at all since there's already no resident left in the affected area.

Exactly. The guys at Fukushima have their plate quite full already. Contaminated groundwater can be drilled and pumped up later, after flooded basements are dealt with.

 

[Borek]

My understanding is that due to the local geology groundwater is expected to go to the sea, not inland.

 

[PLG]

Um, yes. Groundwater eventually goes to sea generally speaking, and all the more so when you are fifty yards away from the sea, so pumping the stuff back up is not really an option in the medium to long run. If there were corium leaks at some point, the material is going toward the ocean at a relatively slow rate of several centimeters a day (it"s slow because the ground is made up of impermeable argilite). There was a long, detailed post in another thread:

https://www.physicsforums.com/showpost.php?p=3356008&postcount=9753
also
https://www.physicsforums.com/showpost.php?p=3345426&postcount=9285

Pierre

 

[sp2]

Many people probably won't agree with me, but I tend to say that I simply don't care for any (sea)water contamination. It's really of absolutely no concern if you compare it to the damage which airborne releases can do and obviously have done (100.000-150.000 displaced people).

Radioactive water leaking in the underground will either reach the open sea where it dilutes or it will contaminate the local groundwater - which makes no difference at all since there's already no resident left in the affected area.

I have to respectfully call this nonsense.

You have no idea how much damage the sea-water or ground-water contamination may or may not do (or how far its effects may spread), and neither does anyone else.
That's really the whole point.

To imply that it's trivial, simply because it's probably less bad than atmospheric release is a little ridiculous.

(It's like saying 9/11 was no big deal, because it would've been a lot worse if it had happened an hour later.)

 

[sp2]

P.S. Anybody betting that the total release from Fukushima will end up at only 10% of Chernobyl would be laughed out of Town by any bookie in Vegas. (Though only after he took all your money, of course.)

 

[Duffer]

I have to respectfully call this nonsense...

Thank you
You have restored some of my confidence in this thread.

I was waiting to see if anybody challenged that (insert word.)

I will also point out that were we (the people living now) were to allow TEPCO to dump their problem into the Pacific, we would be setting a precedent that a thoughtful people would not want to set.

 

[elektrownik]

Is unit 4 sfp skimmer surge tank leaking ? or they change something ? It is only 700mm now, it always was much higher (4500-6500mm)...

 

[clancy688]

P.S. Anybody betting that the total release from Fukushima will end up at only 10% of Chernobyl would be laughed out of Town by any bookie in Vegas. (Though only after he took all your money, of course.)

Again, you can't compare ALL those numbers.

The Chernobyl number was calculated only for airborne releases. With the (in)famous IAEO iodine conversion method (the conversion factors they used can only be applied for airborne releases btw).
If nothing serious happens (another hydrogen explosion for example), the airborne release number WON'T go up. Well, the actual one.
There always is the possibility that TEPCO, NISA and NSC didn't tell the whole truth and the release was significantly bigger than reported.

But what I'm trying to say is: The official, often quoted number, will, even in the future, most likely only contain airborne released. Since the airborne release is finished, the real value of this number won't go up.

It's important to understand this issue if working and quoting official numbers. It doesn't have to be right (well, I think it's the correct approach, but that's only a personal opinion and not everybody thinks the same way, which I expected).

Water contamination is an entirely different thing. For example there's 140.000 TBq each of C134 and C137 loose in the basements. That's each twice the the size of the Chernobyl airborne release and half of a Chernobyl core's worth of C.

As I said, it doesn't have to be the right way. But water contamination DOESN'T count in official release numbers. Remember this.

 

[tsutsuji]

http://www.yomiuri.co.jp/science/news/20110629-OYT1T00674.htm and http://news24.jp/articles/2011/06/29/07185418.html# : The injection into reactors of decontaminated, desalinated water was stopped at around 11:00 AM and started again at 1:33 PM. At 8:10 AM, the hose had been found to be punctured in two places. Incidentally, the tank for liquid waste at the desalinating facility was also found leaking, without much consequence. The cause was a cap removed from a pipe.

http://www.yomiuri.co.jp/science/news/20110628-OYT1T01036.htm 15 tons of 7 μSv/h low contaminated water leaked into unit 6's turbine building basement. The cause is the failure of the attachment of a tube that is part of a level gauge at a low contaminated water tank.

 

[Cire]

You have no idea how much damage the sea-water or ground-water contamination may or may not do (or how far its effects may spread), and neither does anyone else.
That's really the whole point.

I think the ocean around the bikini Atoll would disagree with your premise. If you had no choice but to leak radioactive materials somewhere then the ocean would be your first choice.

Don't under estimate the ability of 187 quintillion gallons of water to dilute the problem.

 

[nikkkom]

Um, yes. Groundwater eventually goes to sea generally speaking, and all the more so when you are fifty yards away from the sea, so pumping the stuff back up is not really an option in the medium to long run.

It is. If boreholes would be drilled significantly deeper than sea level, and then all water which drains into them is pumped up and decontaminated, then almost all underground water will flow into these boreholes, not into sea.

 

[nikkkom]

I have to respectfully call this nonsense.

You have no idea how much damage the sea-water or ground-water contamination may or may not do (or how far its effects may spread), and neither does anyone else.

My point is, underground water moves slow enough so that there is no need to deal with it _right now_, when we have much more pressing issues (like continuing releases of radioactive steam, overflowing basements with 1 Sv/h water and such).

 

[NUCENG]

Yeah, but those were problems with the cesium absorption towers. You don't have to do any halftime math for C because C137 decays with a 30 year halftime. Or 2 years for C134. Anyway, the water they're processing now has a C:I activity ratio (for both C134 and C137) of ~ 1000:1, so whatever radiation problems they get, the iodine is only responsible for a tiny fraction of the resulting radiation.

As for what TEPCO did / calculated wrong, I have no idea. I'd like to know the answer for myself.

Hopefully they realized that most of the Cs released is stable, but it will clog up their filters.
I once found a calculation at a NPP that only considered radioiodine and radiocesium for their filter loading estimates. The author was wondering why the filters were so much larger than they needed to be. He had used the ORIGEN2 output for Ci/MWt but didn't look at the output for gm/MWt which listed yhe stable fission product isotopes.

 

[NUCENG]

PLG ""I am not sure a corium turns off by itself once it becomes active after a criticality,"

there are a couple turnoff mechanisms.
One is "Doppler Broadening", when the corium gets very hot it is more likely to absorb neutrons in a non-fission neutron capture. That's called "Doppler" and tends to limit a runaway. Google "Triga reactor" and watch the youtubes.

Another is 'boil out' , water's ability to moderate is a function of its temperature because the molecules are closer together when it's cold. When they spread apart into steam the neutrons don't get slowed down so well and are more likely to get absorbed in a non-fission capture in fuel or in reactor structural steel.. Anything increases nonfission capture fraction is a shutdown mechanism.

Another is 'displacement' , a euphemism... a steam explosion will disassemble things spreading the fissile material out, increasing "neutron leakage". 'Leakage' is the probability a neutron leaves the neighborhood without hitting a fissile nucleus. Anything that increases leakage is a shutdown mechanism.

Here is a dirt simple primer on reactor physics (that's been posted before, old hands kindly forgive repeat for interested newcomer.) Really it is a not complex subject.
http://www.if.uidaho.edu/~gunner/ME443-543/LectureNotes/ReactorPhysics.pdf
I took a course forty something years ago and this was a great re-introduction. Since you have access to nuke engineers i'd suggest you print it out - you can absorb it easily in one evening if your friends will help you out with vocabulary.

and here's a paper on corium reactivity that's got way too much math for me. it's some fellow's PHD thesis. I found it direct via Google so its not like i snooped the guys' emails. It is several places around 'net now. You'll find his calculations used in the Nureg 5653.

http://list.ans.org/pipermail/ncsd-fukushima/attachments/20110318/f20efbc8/thesis-0001.pdf
Your engineer friends may understand it, mostly i don't. It supports the self regulating nature of water moderated fission though.

Now i think it was zapperzero used a phrase some posts back re corium ::: ".. still stuck to the walls..."
uhhh, zz , was that just toying with words? do you know something i dont? Seen any analysis of what was on that 1Sv piece of concrete rubble?

SteveE has it ::: ""Frustrating as it is, I think I am just going to have to live with the fact that the answers we seek on a whole range of fronts are simply not available with the data we have, and apart from getting the chance to maybe find out the state of containment and cores one day, there is no indication that better quality data will ever become available to us. ""
one knows there were aircraft samples of plumes and better photos around the buildings.

TPTB know.
As a mere civilian i have to wait for the NOVA show.

old jim

The NOVA show will probably be a disappointment for most of those participating in this forum. We are probably well beyond their target audience already. But we'll all probably watch, if only to catch any mistakes. BTW no criticism meant, I love NOVA.

 

[tsutsuji]

http://www.yomiuri.co.jp/science/news/20110629-OYT1T00850.htm and http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110629_02-j.pdf : The water treatment facility was stopped at 2:53 PM after an alarm signalling a leak at the site bunker building (1) rang. It had been also stopped for flushing and adsorption tower replacement between 10:45 AM and 2:13 PM. The reason why the alarm rang is under investigation.

(1) the orange box on http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110627_01-e.pdf

 

[elektrownik]

Is unit 4 sfp skimmer surge tank leaking ? or they change something ? It is only 700mm now, it always was much higher (4500-6500mm)...

now 450mm any comments ?

 

[joewein]

Is unit 4 sfp skimmer surge tank leaking ? or they change something ? It is only 700mm now, it always was much higher (4500-6500mm)...

The one thing that has changed is that they are no longer using the "giraffe" concrete pump truck. On the 16th they installed a pipe from an electric pump to the top of the pool, replacing a pipe destroyed in the unit 4 SFP blast. Their goal is to also install a heat exchanger, effectively restoring the pool cooling and cleaning system.

Most likely the concrete truck was simply injecting fresh water from a pipe carrying water from the dam (via some storage tank), but was not drawing any water from the skimmer surge tank. Now, with TEPCO working towards restoring pool cooling, they probably are cycling water from the skimmer surge tank back into the pool, combining it with fresh water to make up for evaporation.

In any case, less water in the skimmer surge tank is not a problem. Less water in the SFP would be a problem, but with the water topped up the other side of the gate (in the reactor pit and tool bay) for radiation protection there is also more of a safety margin: if the water in the SFP drops below the reactor pit level, the gate starts leaking, topping up the pool again.

Also, as long as the truck is still there they would still have its camera to watch the water level. Perhaps they installed one anyway, I certainly would, with 1500+ fuel assemblies in the pool!

 

[biffvernon]

Don't under estimate the ability of 187 quintillion gallons of water to dilute the problem.

But don't underestimate the ability of biology to act in the opposite direction.

 

[zapperzero]

Now i think it was zapperzero used a phrase some posts back re corium ::: ".. still stuck to the walls..."
uhhh, zz , was that just toying with words? do you know something i dont? Seen any analysis of what was on that 1Sv piece of concrete rubble?
old jim

Nope. Haven't seen anything you haven't, but I do seriously think that there is some corium, based on the high temps still being recorded by the various RPV sensors, much higher than for the other two reactors.

 

[zapperzero]

Not necessarily. It is all a matter of amount of energy stored. If you have hot corium splitting water into hydrogen and oxygen in a closed tank situation doesn't get worse - amount of energy present inside is still the same. It can get worse if the gases get outside and explode there, but that's a slightly different thing.

Given that all three containments are at atmospheric pressure, I think the point is moot.

 

[Astronuc]

Nuclear Engineering International: Closed-loop circulation starts at Fukushima Daiichi
28 June 2011
http://www.neimagazine.com/story.asp?sectioncode=72&storyCode=2059992

TEPCO has begun injecting decontaminated water into units 1, 2 and 3 of the Fukushima Daiichi nuclear power plant.

Some diagrams and numbers provided.

 

[Jorge Stolfi]

Since the airborne release is finished, the real value of this number won't go up.

Is that correct? All four reactors are still releasing steam to the atmosphere. That steam is water that boiled off in contact with the molten cores and/or SFPs, hence it must not be quite Perrier. Are there any estimates of the amount of radioactivity that is being released that way?

 

[zapperzero]

Is that correct? All four reactors are still releasing steam to the atmosphere. That steam is water that boiled off in contact with the molten cores and/or SFPs, hence it must not be quite Perrier. Are there any estimates of the amount of radioactivity that is being released that way?

Of course it is not correct. TEPCO sampled a steam plume a few days ago, but I don't recall them having released the results.

 

[jim hardy]

zz wrote: ""...but I do seriously think that there is some corium, based on the high temps still being recorded by the various RPV sensors, much higher than for the other two reactors.""

i guess the giveaway would be how much water it's turning into steam.
But that's a difficult number to know if a lot of what they pump in goes into the basement as water instead of coming out the top as steam.

Were I manning the pumps i'd try to inject just enough water to carry away the expected heat then cut back to the point i had fifty degrees or so of superheat. That'd assure the steam coming out is dry , hence mostly distilled water molecules not water droplets. That'd minimize the amount of little radioactive friends that tag along with the steam.


I'll not attempt a calc here - i work with sliderule and BTU's but the rest of world uses EXCEL and metric system.
As George Gobel said - "Ever feel like the world is a tuxedo and you're a pair of brown shoes?"

 

[tsutsuji]

http://www.yomiuri.co.jp/science/news/20110629-OYT1T00850.htm and http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110629_02-j.pdf : The water treatment facility was stopped at 2:53 PM after an alarm signalling a leak at the site bunker building (1) rang. It had been also stopped for flushing and adsorption tower replacement between 10:45 AM and 2:13 PM. The reason why the alarm rang is under investigation.

(1) the orange box on http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110627_01-e.pdf

http://www.asahi.com/national/jiji/JJT201106290077.html : The facility was started again at 9:15 PM.

 

[clancy688]

Is that correct? All four reactors are still releasing steam to the atmosphere. That steam is water that boiled off in contact with the molten cores and/or SFPs, hence it must not be quite Perrier. Are there any estimates of the amount of radioactivity that is being released that way?

Back in April, the daily emissions were estimated at 154 TBq (after iodine conversion).

http://ex-skf.blogspot.com/2011/04/fukushima-i-nuke-plant-154.html

Since then I've heard of no new estimates for daily discharges. Still I'd take that number only as a "worst case" for June, since better cooling certainly had a positive effect on those discharges.

After 100 days, we're at an additional 15.000 TBq. Compared to the 770.000 TBq, that number is fairly small. It won't change the overall situation.

Saying that the number "won't go up" was a mistake on my behalf, sorry for that. I rather meant that the ongoing releases won't change much since they're very mall compared to the initial first week release.

 

[tonio]

My point is, underground water moves slow enough so that there is no need to deal with it _right now_, when we have much more pressing issues (like continuing releases of radioactive steam, overflowing basements with 1 Sv/h water and such).

Based on what information do you think that? I assume that the part of the plant nearest to the sea is built on a bed of rubble, bulldozed into the sea. Such material tends to be quite permeable. Furthermore, (artificial) preferential pathways into the sea may exist. What I mean to say is that it is well possible that (part of) the contaminated ground water may reach the sea much quicker than you think.

 

[~kujala~]

The information regarding the speed of groundwater flow has come from TEPCO itself:

Underground water flows at a speed of about 5 to 10 centimeters a day, so we have more than a year before it reaches the shore.

http://mdn.mainichi.jp/perspectives/column/archive/news/2011/06/20110620p2a00m0na005000c.html

But I don't know how extensive their investigations regarding the groundwater properties has been.

A couple of years ago they planned a big survey concerning the soil characteristics of Daiichi/Daiini:
http://www.tepco.co.jp/en/press/corp-com/release/betu07_e/images/071105e1.pdf

Groundwater level observation was part of the planned survey. They planned 13 shallow boring holes, depth 10 - 20 m. According to the map some of the shallow boring holes were quite near the sea.

Perhaps this survey also gave TEPCO some information concerning the speed of groundwater flow?

Now that there has been a big earthquake I think they have to re-examine the soil characteristics of Daiichi?

 

[tsutsuji]

http://www.chunichi.co.jp/s/article/2011062990203609.html : On 30 June, Tepco plans to begin transferring the accumulated water from unit 6 into the megafloat barge.

 

[tonio]

A couple of years ago they planned a big survey concerning the soil characteristics of Daiichi/Daiini:
http://www.tepco.co.jp/en/press/corp-com/release/betu07_e/images/071105e1.pdf

Groundwater level observation was part of the planned survey. They planned 13 shallow boring holes, depth 10 - 20 m. According to the map some of the shallow boring holes were quite near the sea.

Perhaps this survey also gave TEPCO some information concerning the speed of groundwater flow?

Now that there has been a big earthquake I think they have to re-examine the soil characteristics of Daiichi?

OK, that's interesting. They indicated that these boreholes are also meant for groundwater level observation, which means that they are probably provided with piezometers. Thus it is simple to assess the slope of the groundwater table. Assuming that they also assessed the borehole profiles (type of soil/rock) and possibly also did some well tests (assessment of permeability), they are also able to assess the ground water flow speed.

On the other hand, as far as I know one or more reactors are provided with ground water extraction systems, in order to keep their basements from flooding with ground water. If this is correct and if they monitored the amount of extraction on a regular basis:
- They have another means to assess the permeability of the soil/bedrock.
- Assessment of the present ground water table (and thus flow speed) is probably unreliable as it is disturbed by these extractions and in a phase of adjustment (i.e. increasing flow speed), probably even if the extractions were halted after the tsunami.
- More important: they are provided with a simple ground water remediation system: use the extractions to withdraw the contaminated groundwater and to lower the ground water table to somewhat below sea level, and you have a simple means to minimize inflow of contaminated groundwater into the sea. On the other hand, extra water purification capacity is then required.

 

[etudiant]

OK, that's interesting. They indicated that these boreholes are also meant for groundwater level observation, which means that they are probably provided with piezometers. Thus it is simple to assess the slope of the groundwater table. Assuming that they also assessed the borehole profiles (type of soil/rock) and possibly also did some well tests (assessment of permeability), they are also able to assess the ground water flow speed.


- More important: they are provided with a simple ground water remediation system: use the extractions to withdraw the contaminated groundwater and to lower the ground water table to somewhat below sea level, and you have a simple means to minimize inflow of contaminated groundwater into the sea. On the other hand, extra water purification capacity is then required.

Perhaps the groundwater is what TEPCO has in mind for the other 125,000 tons of water they plan to treat.
AREVA noted that the plan was to process 250,000 tons of water, even though there is a bit less than half as much in the plant currently.

 

[Luca Bevil]

They have to leep cooling the reactors. That should account for much of the remaining processing tons.

 

[joewein]

TEPCO reports finding Tellurium-129 (Te-129, half life 70 minutes) in early June, writes http://ex-skf.blogspot.com/2011/06/fukushima-i-nuke-plant-radioactive_29.html" :

Then, on page 99 for the test results for the samples taken on June 12:

Te-129 (half-life 70 minutes): 230 becquerels/liter, outside the silt fence in front of the Reactor 4 water intake canal.

Te-129 was also found in the deep seawater 8 kilometers off the coast of Minami-Soma City and Onahama on June 7 (pages 27, 28) and June 9 (page 39) separately.

A substance with more than 20 half lives per day, i.e. where less than 1/1,000,000 remains after one day, found some 80 days after shutdown, up to 40 km south of F1? Oh really?

What's even weirder is that it is identified in samples where *no* I-131 or Cs-134 or Cs-137 was found. Frankly, I have my doubts how reliable those tests are.