Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Gilles]

sorry I may have missed some posts but has the "Cl-38" mystery been solved or any hint for that ? Astronuc said that they could have been a typo and a confusion with "Cs -138" - there are also some reports of "Co-58" , is it a possibility? if Cl-38 has been indeed produced (despite the absence of Na-24 or Cl-36, but are all nuclides really listed in these reports), is it possible to explain the needed neutron flux without some parts of the reactor being near-critical , at least during some time?

 

[AntonL]

>slide explaining the isotopes found in a reactor
If the reactor is working properly I thought that the isotopes were contained in the Zircaloy casing

The isotopes in the upper section (gas) are the ones normally found in working reactor as the gas can leak out, the others should be contained in the fuel rods.

 

[AtomicWombat]

Refering to https://www.physicsforums.com/showpost.php?p=3210895&postcount=1342" and below plan the building is about 125 meters long (google earth)
then the flooded area is about 1650 m21 40cm
2 100cm
3 150cm
4 80cm
confirms that the source of the water is from unit 3 and has leaked into the neighbouring
units through cable tunnels. The cable tunnels would be fire proofed between the buildings
restricting the flow hence the varied heights

at the time of measurement volume of water is about 6000m3

From the IAEA:
http://www.iaea.org/newscenter/news/2011/fukushimafull.html"
March 22
"Unit 3
Unit 3 experienced an explosion on 14 March that destroyed the outer shell of the building's upper floors. The blast may have damaged the primary containment vessel and the spent fuel pool. Concerned by possible loss of water in the pool, authorities began spraying water into the building in an effort to replenish water levels. First, helicopters dropped seawater on 17 March, and every day since then, including 21 March, emergency workers have sprayed water from fire trucks and other vehicles, so far spraying at least 3,742 tonnes."

March 24
"Japanese authorities today reported that three workers at the Fukushima Daiichi nuclear power plant were exposed to elevated levels of radiation. The three were working in the turbine building of reactor Unit 3 and have received a radiation dose in the range of 170-180 millisieverts.
Two of the workers have been hospitalized for treatment of severely contaminated feet, which may have suffered radiation burns. The workers had been working for about three hours in contact with contaminated water.
The IAEA is seeking additional information."

There were also reports that authorities were unable to maintain water levels in reactor 3, which I cannot source at the moment.

So we know where all the water went!

 

[|Fred]

just as a reminder side by side first analysis of Unit 3 and general one
[PLAIN]http://i.min.us/imbXPu.jpg

 

[Borek]

Perhaps someone knowledgeable could explain to me why they haven't started closing these plants up with concrete? How much longer do we need to wait?
Does anyone perhaps expect something could be salvaged in those plants?

I am perhaps not much more knowledgeable, but I don't think it will be a valid solution at this stage. I guess you think about something similar to Chernobyl sarcophagus. First, it takes months of preparations, it is not a thing that can be done fast. Second, before sarcophagus is built whatever is inside is still in potential contact with environment, so it won't stop radiation leaks for months. Third, and perhaps the most important part - building a sarcophagus around the buildings before the situation inside is known and stable, is just asking for more troubles, as you don't know how the situation can evolve.

 

[jensjakob]

"The water would be sent to condensers"
http://www.jaif.or.jp/english/aij/member/2011/earthquakereport32.pdf

Depending on the volume of water - I wonder:
1. Will it be fed into the reactorside of the condenser?
of
2. Will it be feed to the seawater side - sending it into the ocean?

 

[AntonL]

"The water would be sent to condensers"
http://www.jaif.or.jp/english/aij/member/2011/earthquakereport32.pdf

Depending on the volume of water - I wonder:
1. Will it be fed into the reactorside of the condenser?
of
2. Will it be feed to the seawater side - sending it into the ocean?

and feed it back to the reactors as cooling water no
sending it to the see yes
so feeding it to the condenser sounds better and they have fairly unrestricted access to the sea to cater for huge amounts of cooling water during normal operation

The condensers are the three blocks
[ Tu]rbi[ine] B[uild]ing
and blue flooded area by earlier press release.

 

[jensjakob]

A bit more about the basement-water:
http://mdn.mainichi.jp/mdnnews/news/20110327p2g00m0dm063000c.html

My questions:
1. What will they do with it?
2. What are the quantities?
3. Does it keep on coming?
4. Notice the part about needing "more pumps"

 

[jensjakob]

Hmmmm. Interesting math from another forum:
"
Also note the misleading numbers in the story--it's comparing apples to oranges: they say the detected level of 1,000 millisieverts per hour is four times the occupational limit of 250 millisieverts set by the government. But the 250 set by the government is the ANNUAL limit, while the 1,000 is the HOURLY amount.
"

Comments?

 

[Gilles]

it's not comparing apples to oranges, it's comparing elephants to mice ...

 

[AtomicWombat]

Four units and four different failure modes leads to one conclusion:
BWR are not as safe as they are said to be. It is time to switch them off.


Conclusions already made by industry experts (see attached pdf file)
1. All existing power plants' passive emergency cooling systems (BWR's
RCIC and PWR's turbine-driven auxiliary feedwater system) should be inspected
and reinforced to assure their reliability during adverse condition. Onsite
emergency generators should be further protected.
2. PWR is more resilient than BWR because of its steam generator secondary
water inventory and size of containment. This gives larger margin to core damage
and containment failure. Further review is still necessary to improve the safety
level.
3. Spent fuel pool safety has been grossly overlooked. A hardened and
independent top spray system is necessary for all nuclear power plants.

Please read attached pdf file - the most authoritative analysis yet found.

From the attched pdf, "An immediate question is whether a PWR is more resilient to an
earthquake/blackout than a BWR. By using our PCTRAN PWR models it is
quantitatively analyzed in great details. We may conclude an affirmative “yes” -
but not by much - just buy you a few more hours to resume onsite power supply.
After that the consequence is the same."
This qualifies conclusion 2 considerably.

I'm quite sure conclusion 3 will be the most obvious outcome of this event - spent fuel will no longer be stored for decades in pools in the secondary containment.

I think your conclusions are far stronger than warranted by the report.

 

[PietKuip]

sorry I may have missed some posts but has the "Cl-38" mystery been solved or any hint for that ? Astronuc said that they could have been a typo and a confusion with "Cs -138" - there are also some reports of "Co-58" , is it a possibility? if Cl-38 has been indeed produced (despite the absence of Na-24 or Cl-36, but are all nuclides really listed in these reports), is it possible to explain the needed neutron flux without some parts of the reactor being near-critical , at least during some time?

A new mystery is the 10^9 Bq/ml of I-134 in reactor building 2 with a half-life of 53 minutes.

Now, 340 half-lives after the earthquake that is supposed to have switched off the production of fission products.

 

[Fresno Phil]

Also, I think Reactor 2 is now confirmed RPV breach due to levels of Cs-134 measured outside of core.

We had a de-facto breach of the RPV when they lost the primary cooling loop and instead started using the fire-suppression loop for cooling.

With no loop to work with, what goes in has to come out. Before, I though they were just letting it drain back into the ocean, but who knows what sort of piping survives in these plants now.

Reactor 2 was the one with the "bad noise" heard after venting. A hydrogen explosion compromising the suppression chamber would not be unthinkable. The reported pressure for the suppression pool has been "downscale" for almost 2 weeks now.

According to NISA's latest, they are injecting 280 litres/min into #2's core via the fire suppression line, yet water level is 1.2m below the top of the rods, and was worse for a long time. Drywell is currently being reported as unpressurized (1ATM abs), yet has the highest radiation level (42 Sv/h).

Who knows what's going on with this unit.

 

[wasteinc]

as PietKuip indicates (about I-134), and KateB has suggested (regarding radioactive Cl), do we have indications that some criticality still happens inside some of the reactors?

Is this why http://english.kyodonews.jp/news/2011/03/81325.html" news emphasizes the I-134 ?

"According to the latest data released Sunday, radioactive iodine-134, a substance which sees its radiation release reduced to about half in some 53 minutes, existed in water at the No. 2 reactor's turbine building at an extremely high concentration of 2.9 billion becquerels per 1 cubic centimeter."

As AntonL in post #1451 has posted a picture suggesting that i-134 is produced only during fission, and not as a result of a damaged core

If some part of U is critical, that means that new heat is produced and the numbers about the residual heat you already calculated here are off.

 

[jensjakob]

Well, gents, the focus on short halflife leads to some journalists writing stuff like "so it will disperse fast and not be a danger".

I do think that the perspective shown in here "If it has such a short halflife, why is it still there 14 days after shutdown" is much more important than the spin sold to journalists.

(Though it IS positive that it disperses so fast...)

Source:
http://www.bbc.co.uk/news/world-asia-pacific-12872707

Quote:
"The radiation found in the sea will no longer be a risk after eight days because of iodine's half-life, officials say."

 

[Gilles]

sorry if I speculate too much but
* we know that hydrogen has been produced , so temperature has been over 1200°C and some zirconium coats have been oxidized and probably molten
* we know that fission products are abundantly detected in water, which confirms the destruction of many rods;
* we know that periodically smokes of various colors are emitted, which seems to indicate intermittent steam overpressures
* presence of short-lived isotopes is reported (no typos possible for I-134 i presume..), either fission products or neutron activated nuclides (more dubious?) which can be explained only if active fission is present.
Is a "oklo -like " scenario possible, that enough fuel could have melt and gather in the reactor, and near critical conditions could be met somewhere , with cycles of successive presence of liquid water (moderating) -vaporized steam (less moderating), giving some kind of feedback stabilizing the system to near critical conditions - for how long then?

 

[HansHooligan]

A bit more about the basement-water:
http://mdn.mainichi.jp/mdnnews/news/20110327p2g00m0dm063000c.html

My questions:
1. What will they do with it?
2. What are the quantities?
3. Does it keep on coming?
4. Notice the part about needing "more pumps"

5. what happens if water evaporates, will remaining matter become critical?
6. If it's a thick enough slurry, can fission happen in those water pools and if yes then what?

 

[John5656]

Daft question alert.

I see that they are detecting these isotopes with short half lives, and that indicates fission is still taking place. But isn't this is what is keeping the fuel rods hot?

Are they not always decaying, and thus fission is occurring?

Their arrangement, boron, control rods is preventing them from going critical, but surely we would expect to find these isotopes if containment has been lost? Either in the reactor or the SFP?

 

[Gilles]

Daft question alert.

I see that they are detecting these isotopes with short half lives, and that indicates fission is still taking place. But isn't this is what is keeping the fuel rods hot?

Are they not always decaying, and thus fission is occurring?

normally not, what heats the residual fuel is radioactive decay of fission products, but a chain reaction is not supposed to occur anymore if the control bars have been plunged into the reactor - it should be subcritical. Neutron induced fission is quite different from radioactive decay.

 

[jensjakob]

5. what happens if water evaporates, will remaining matter become critical?
6. If it's a thick enough slurry, can fission happen in those water pools and if yes then what?

Welcome to the Forum, Hans.

To my best knowledge, the answer to these 2 questions are a big no. Fortunately ;-)

 

[|Fred]

normally not, what heats the residual fuel is radioactive decay of fission products, but a chain reaction is not supposed to occur anymore if the control bars have been plunged into the reactor - it should be subcritical. Neutron induced fission is quite different from radioactive decay.

I think I can reformulate John5656's questions: is the radioactivity of those isotope incoherent with the amount of radioactivity suppose to be in the rod when the reactor scramble.

Nt x 2^(number of half-lives)= No

Where:
Nt = amount of isotope remaining (mesured)
No = original amount of isotope
number of half-lives = time / half-life

 

[jensjakob]

To those wondering how much the NRC might know, google gave me this from Hanford Hills (DOE)
http://msa.hanford.gov/hills/lesson.cfm?id=2458

Guess that NRC has quite some information - and I view it VERY positive.

TEPCO and Japan needs to understand that truth is out there - and they can't play the "silent game"

 

[John5656]

normally not, what heats the residual fuel is radioactive decay of fission products, but a chain reaction is not supposed to occur anymore if the control bars have been plunged into the reactor - it should be subcritical. Neutron induced fission is quite different from radioactive decay.

To quote, from wikipedia (I know what your thinking. I'm not a physicist, just trying to understand what is going on)

Uranium-235 undergoes a small rate of natural spontaneous fission, so there are always some neutrons being produced even in a fully shutdown reactor. When the control rods are withdrawn and criticality is approached the number increases because the absorption of neutrons is being progressively reduced, until at criticality the chain reaction becomes self-sustaining.

Even in a subcritical assembly such as a shut-down reactor core, any stray neutron that happens to be present in the core (for example from spontaneous fission of the fuel, from radioactive decay of fission products, or from a neutron source) will trigger an exponentially decaying chain reaction. Although the chain reaction is not self-sustaining, it acts as a multiplier that increases the equilibrium number of neutrons in the core.

http://en.wikipedia.org/wiki/Nuclear_reactor_physics

So even though we have a scram, surely some decay will be occurring, producing the short half lives found...? We don't have to have a chain reaction to find them, or do we?

 

[AtomicWombat]

A bit more about the basement-water:
http://mdn.mainichi.jp/mdnnews/news/20110327p2g00m0dm063000c.html

My questions:

My (best-guess) answers:

1. What will they do with it?

Ideally filter the radiaoactive particles before pumping the water out to sea. In reality probably just pump it out to sea.

2. What are the quantities?

Quantities of what? Radiaoactive contaminants OR water? An ealier estimate was about 6000 tonnes. I estimate about 2500-3000 tonnes - the approximate mass of water pumped into reactor 3.

3. Does it keep on coming?

As long as they keep pumping water into reactors that leak directly into the turbine buildings, yes it will keep coming.

4. Notice the part about needing "more pumps"

Yes and it strikes me they are making a bad situation worse by dispersing the radioactivity from the reactor cores (esp. no. 3) to the turbine buildings. But I guess that comes from not clearly understanding the situation before acting.

 

[PietKuip]

So even though we have a scram, surely some decay will be occurring, producing the short half lives found...? We don't have to have a chain reaction to find them, or do we?

Chlorine-38 is not a fission product. It can only occur at these levels when seawater is exposed to an ongoing (or very recent) neutron flux.

Neither can I-134 be present at such levels in a reactor that has been off for two weeks. Beta-rays or gammas do not produce iodine-134.

There are (intermittent? Oklo-type?) chain reactions going on at least two reactor buildings.

 

[daumphys]

From the attched pdf, "An immediate question is whether a PWR is more resilient to an
earthquake/blackout than a BWR. By using our PCTRAN PWR models it is
quantitatively analyzed in great details. We may conclude an affirmative “yes” -
but not by much - just buy you a few more hours to resume onsite power supply.
After that the consequence is the same."
This qualifies conclusion 2 considerably.

I'm quite sure conclusion 3 will be the most obvious outcome of this event - spent fuel will no longer be stored for decades in pools in the secondary containment.

I think your conclusions are far stronger than warranted by the report.

But at the point of nuclear reactor control, Is this conclusion always right?
Is the time lag of PWR model more short than BWR model? Is the response time of the BWR model short?

 

[AtomicWombat]

5. what happens if water evaporates, will remaining matter become critical?

No. These are not fissionable isotopes. Only the U238 and Pu239 (IIRC in these reactors) are fissionable. These are in their oxide form and are highly insoluble.

6. If it's a thick enough slurry, can fission happen in those water pools and if yes then what?

No again. See Q5 answer.

 

[AntonL]

Reactor 2 was the one with the "bad noise" heard after venting. A hydrogen explosion compromising the suppression chamber would not be unthinkable. The reported pressure for the suppression pool has been "downscale" for almost 2 weeks now.

According to NISA's latest, they are injecting 280 litres/min into #2's core via the fire suppression line, yet water level is 1.2m below the top of the rods, and was worse for a long time. Drywell is currently being reported as unpressurized (1ATM abs), yet has the highest radiation level (42 Sv/h).

Who knows what's going on with this unit.

We also know that all three reactors cores were severely damaged due to lack of cooling after the Tsunami struck. check the early reports.

Read my https://www.physicsforums.com/showpost.php?p=3209639&postcount=1218"
in reactor 2 residue heat should be 2.2MW which would boil away 6.3m3/h
any water above this quantity either fills the reactor or is boiled away or combination of both

280 l/m is 16.8m3/h and the temperature is fairly constant around 100 degrees C
should all this be boiled away to keep the temperature then there is maximum 3MW
too much heat or 0.1% of the reactor designed 2380MW thermal heat capacity.
With the huge amounts of water now in the basement the 3MW of too much heat
is a too high estimate, is is probably a fraction of that.

 

[|Fred]

Ideally filter the radiaoactive particles before pumping the water out to sea. In reality probably just pump it out to sea.

Tepco is planing to pump the water in the condenser (at the moment)

 

[AtomicWombat]

Daft question alert.

I see that they are detecting these isotopes with short half lives, and that indicates fission is still taking place. But isn't this is what is keeping the fuel rods hot?

Are they not always decaying, and thus fission is occurring?

Their arrangement, boron, control rods is preventing them from going critical, but surely we would expect to find these isotopes if containment has been lost? Either in the reactor or the SFP?

If a full meltdown has occurred it may be possible for critical mass arrangements of molten fuel, cladding and control rods to form by chance. In any case there would be a tendency for the components of the melt to separate based on different melting temperatures, chemical reactivity, solubility and density. So it would not be surprising for fuel to clump into a porous structure that allows water circulation.

However, this is speculation based on the evidence that fission continues. I suspect there have been no detailed studies of such a process.