Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Joe Neubarth]

Just because they haven't released photos doesn't mean they haven't taken them. And I think they probably know more about cooling a reactor than you do. For instance, radiation levels were pretty high at one point in the air over the plant so maybe a helicopter could not stay there very long.

No, they do not know more than I do. Look at the photos. They are just spraying the hose into the air hoping to get some of the water in the building over the reactor and also in the general direction of the expended fuel rod pools. That was not a genius decision.

Also, a helicopter need not fly over the reactor site for more than a few seconds to hook a hose to a girder if the hook is already attached to the hose. long tending lines could have been attached to the end of the hose in one way or another. That would have been a lot more effective than trying to shoot water into the air in proximity to the reactor building.

 

[M. Bachmeier]

No, they do not know more than I do. Look at the photos. They are just spraying the hose into the air hoping to get some of the water in the building over the reactor and also in the general direction of the expended fuel rod pools. That was not a genius decision.

Also, a helicopter need not fly over the reactor site for more than a few seconds to hook a hose to a girder if the hook is already attached to the hose. long tending lines could have been attached to the end of the hose in one way or another. That would have been a lot more effective than trying to shoot water into the air in proximity to the reactor building.

Joe do you know how difficult it would be to coordinate what your suggesting.

 

[PietKuip]

Looks like it is common in BWR's, and that you are correct, NaCl impurities in water.

http://www.nap.edu/openbook.php?record_id=9263&page=116

But its production should essentially have stopped two weeks ago. That is 14 times 40 half-lifes ago. It should be gone.

To me this suggests that there is a huge neutron flux of the injected seawater.

Unless they made an error in the exponent.

 

[KateB]

Kate are we looking at unlikely chemistry. This case is unprecedented, with ocean water and uncounted types of impurities potentially interacting with isotopes?

I realize this. But NaCl, and dissociated compounds in solution, would likely become neutron activated regardless of source. As he asked about CL-38, I responded re: that isotope based on some reading I had already been looking at to brush up on my knowledge of radiochem. Is there any reason to think that Cl-38 could be a daughter product of something else, when it is already known as a very probable and possible interaction as a solute? If so, please elaborate.

**that should read regardless of source of the *impurities in water* Looking back it was cryptic.

 

[M. Bachmeier]

But its production should essentially have stopped two weeks ago. That is 14 times 40 half-lifes ago. It should be gone.

To me this suggests that there is a huge neutron flux of the injected seawater.

Unless they made an error in the exponent.

Do you think this is something entirely different from interaction with impurities and isotopes.

 

[KateB]

But its production should essentially have stopped two weeks ago. That is 14 times 40 half-lifes ago. It should be gone.

To me this suggests that there is a huge neutron flux of the injected seawater.

Unless they made an error in the exponent.

perhaps it was an error, but it has been mentioned in earlier posts (ones that were never quite addressed to my satisfaction :) that small amounts of high energy neutrons were measured up to 1.5 km from the plant (suggests fission?), if there is some type of breach, coupled with fission, could this be a reason for the flux? And by extension the presence of Cl-38? If so, this looks very bad.

 

[Joe Neubarth]

Joe do you know how difficult it would be to coordinate what your suggesting.

I know many Navy helicopter pilots who could drop a hook in place within fifteen seconds. It is not that hard for the pilot. Attaching an improvised hook to a hose might take fifteen minutes. But, the reality is that now it is all ex post facto. (the pun is intended here, too.)

 

[M. Bachmeier]

I realize this. But NaCl, and dissociated compounds in solution, would likely become neutron activated regardless of source. As he asked about CL-38, I responded re: that isotope based on some reading I had already been looking at to brush up on my knowledge of radiochem. Is there any reason to think that Cl-38 could be a daughter product of something else, when it is already known as a very probable and possible interaction as a solute? If so, please elaborate.

**that should read regardless of source of the *impurities in water* Looking back it was cryptic.

Sorry Kate the resulting radio-chemistry of adding sea water is unprecedented and I think I misunderstood the time scale of the sample. Were not talking about simply irradiation of mixed compounds but potential interaction with complex compound mixes, so there's a lot of room for questions and misunderstanding. My part.

 

[PietKuip]

perhaps it was an error, but it has been mentioned in earlier posts (ones that were never quite addressed to my satisfaction :) that small amounts of high energy neutrons were measured up to 1.5 km from the plant (suggests fission?), if there is some type of breach, coupled with fission, could this be a reason for the flux? And by extension the presence of Cl-38? If so, this looks very bad.

I discarded those neutron measurements at the gate (fluctuating around zero, even negative sometimes). And they have been telling us that the reactors were shut off.

The stable isotope chlorine-37 has a relatively large cross-section for neutron absorption. I am not a nuclear scientist, but I cannot find another way of producing Cl-38. Such high concentrations of this short-lived isotope suggest that there is still a chain reaction. But that is impossible.

 

[Joe Neubarth]

perhaps it was an error, but it has been mentioned in earlier posts (ones that were never quite addressed to my satisfaction :) that small amounts of high energy neutrons were measured up to 1.5 km from the plant (suggests fission?), if there is some type of breach, coupled with fission, could this be a reason for the flux? And by extension the presence of Cl-38? If so, this looks very bad.

Kate, your concern is very valid. We know that there has been a melt down of the reactor. We do not know how bad it was, but I feel it was quite bad. What is the documented neutron release rate from Oxidized Zirconium Uranium lava?

Chernobyl had a good flow, and I suspect that reactor 3 had a good flow, and some of it may have found it's way to diverse places where the neutrons could be thermalized in water pools just to the Oxidized Uranium's liking. Not likely, but we could have critical masses in some unusual places after that massive explosion. (Not supercritical, but sustaining never the less)

I hope I live long enough to read the summary report on what they think happened to Reactor Three. That will make for some very interesting reading.

 

[M. Bachmeier]

I discarded those neutron measurements at the gate (fluctuating around zero, even negative sometimes). And they have been telling us that the reactors were shut off.

The stable isotope chlorine-37 has a relatively large cross-section for neutron absorption. I am not a nuclear scientist, but I cannot find another way of producing Cl-38. Such high concentrations of this short-lived isotope suggest that there is still a chain reaction. But that is impossible.

There's been a lot of water poured over this site. Fresh water, sea water etc. If you have a small substantive reactor leak interacting physically with isotopes produced by impurities of water and decaying isotopes from stored fuel rods, is it possible to see neutron moderation?

P.S, In small quantities?

 

[AntonL]

I discarded those neutron measurements at the gate (fluctuating around zero, even negative sometimes). And they have been telling us that the reactors were shut off.

The stable isotope chlorine-37 has a relatively large cross-section for neutron absorption. I am not a nuclear scientist, but I cannot find another way of producing Cl-38. Such high concentrations of this short-lived isotope suggest that there is still a chain reaction. But that is impossible.

But a shut off reactor continues to produce heat, because of the decay of the fision products, do these emit the neutrons?
Further we also now that there has been a partial destruction of the cores according to tepco, and the NaCl would be in direct contact with fissionable material, Tepco should test for Uranium isotopes in the water that will then tell us more,

 

[PietKuip]

But a shut off reactor continues to produce heat, because of the decay of the fision products, do these emit the neutrons?
Further we also now that there has been a partial destruction of the cores according to tepco, and the NaCl would be in direct contact with fissionable material, Tepco should test for Uranium isotopes in the water that will then tell us more,

Direct contact would no be necessary. Neutrons penetrate zirconium and steel.

Yes, there are delayed neutrons from fission products. They account for less than one percent of the neutron flux in a working reactor. But neutron emitters have short half-lives (at most a minute), so they should be gone.

 

[Borek]

We know that there has been a melt down of the reactor.

Do we? At the moment this is just a speculation. Let's try to stick to facts.

 

[KateB]

Kate, your concern is very valid. We know that there has been a melt down of the reactor. We do not know how bad it was, but I feel it was quite bad. What is the documented neutron release rate from Oxidized Zirconium Uranium lava?

Chernobyl had a good flow, and I suspect that reactor 3 had a good flow, and some of it may have found it way to diverse places where the neutrons could be thermalized in water pools just to the Oxidized Uranium's liking. Not likely, but we could have critical masses in some unusual places after that massive explosion. (Not supercritical, but sustaining never the less)

I hope I live long enough to read the summary report on what they think happened to Reactor Three. That will make for some very interesting reading.

the Cl-38 was found in the Turbine-1 room. It seems (more) understandable if it was found in 3, considering (I believe, not sure!) an unintended consequence of MOX can be 'Breeder' type reactions (thorium daughter product? -Correct me if I'm wrong!) Unless the water is all from 3, and just being distributed throughout the turbine rooms through conjoined tunnels... Is it possible that criticality would be sustained in the U-only reactors even after control rods and boron was flushed in? Doesn't seem possible. Unless SFR escaped the SP's and somehow went critical again, though that seems unlikely too. Any takers?

 

[timeasterday]

We know that there has been a melt down of the reactor.

oops, Borek beat me. I was questioning this statement too. How do we know?

 

[M. Bachmeier]

But a shut off reactor continues to produce heat, because of the decay of the fision products, do these emit the neutrons?
Further we also now that there has been a partial destruction of the cores according to tepco, and the NaCl would be in direct contact with fissionable material, Tepco should test for Uranium isotopes in the water that will then tell us more,

Sorry Anton, but I must ask a dumb question. If there were a leak of a melted core near the bottom, does it have to be corium? I only ask because fuel rods are different. Some things melt at different temperatures.

 

[M. Bachmeier]

oops, Borek beat me. I was questioning this statement too. How do we know?

You've been reading and something smells.

 

[Gilles]

by looking at another video from NHK, we see the collapsed roof of R1 and I realized that the red beams are actually horizontal.

(http://www3.nhk.or.jp/daily/english/25_30.html , around the 3/5th)

So I repost the screenshot of the first video in a better orientation
[PLAIN]http://www-laog.obs.ujf-grenoble.fr/~henri/Fukushima2.gif
still difficult to decide what it is - but it may be a glowing light through a crack of the collapsed roof. If the reactor vessel is damaged, it has been probably during the explosion, or it may be a glow from the SFP.

 

[rhody]

Astronuc,

Are specialized teams in the US being organized officially, or unofficially through contact with the Japanese Govt and Tepco to provide virtual and on-site support hardware, etc... for containment of the reactors ?

Have you or anyone you know who shares your expertise been involved with any of the teams in Japan to address this crisis, and have any of them reviewed or joined in the discussions here in this thread or other related threads on PF ?

The reason for my query is that as each day passes, it appears to me, a layman looking from the outside in that things could get worse. The window(s) of opportunity appear to be filled with more roadblocks as each day passes.

Thanks...

Rhody...

 

[Joe Neubarth]

Sorry Anton, but I must ask a dumb question. If there were a leak of a melted core near the bottom, does it have to be corium? I only ask because fuel rods are different. Some things melt at different temperatures.

In past reactor meltdowns, the Zirconium ran together with the Uranium and collected at the bottom of the reactor vessel or flowed out through steam releases like at Chernobyl. For them to be together, they melted and flowed about the same time.

 

[PietKuip]

Let us assume that the numbers http://www.nisa.meti.go.jp/english/files/en20110325-6.pdf are correct and that there really is a megabecquerel of Cl-38 per cm^3 in that water.

Suppose this is the steady state concentration in a certain neutron flux. Then the number of neutrons absorbed is equal to the number of decays. Let is suppose this is sea water, 3 % NaCl by weight. That is 30 milligrams of NaCl per cubic centimeter. Less than 1 millimole.

The cross section for neutron absorption of Cl-37 is 33 barns = 33 x 10^-24 cm. Only about a quarter of the chlorine consists of this isotope. So the total cross section is 10^23 x 10^-3 x 33.10^-24 = 10^-3 cm^2.

So one needs a neutron flux of about 10^9 neutrons per cm^2 per second to get this kind of induced radioactivity. That is several orders of magnitudes below what one has in a working reactor. But the activity found may also be several orders of magnitude below steady state.

Please correct me if there is a major error in this estimate.

Edit: Cl-37 has a cross section of 0.423 barns; I underestimated the neutron flux by two orders of magnitude.

 

[Reno Deano]

None of the experts on BWRs (from NRC training center) has contributed to this and shouldn't. If by mistake their feelings or assumptions were to get out before being fed to the IAEA, TEPCO or the Japanese Gov't they (NRC) would be in deep kimche.

See NRC's updates on assistance: http://www.nrc.gov/japan/japan-info.html"

 

[Joe Neubarth]

Let us assume that the numbers http://www.nisa.meti.go.jp/english/files/en20110325-6.pdf are correct and that there really is a megabecquerel of Cl-38 per cm^3 in that water.

Suppose this is the steady state concentration in a certain neutron flux. Then the number of neutrons absorbed is equal to the number of decays. Let is suppose this is sea water, 3 % NaCl by weight. That is 30 milligrams of NaCl per cubic centimeter. Less than 1 millimole.

The cross section for neutron absorption of Cl-37 is 33 barns = 33 x 10^-24 cm. Only about a quarter of the chlorine consists of this isotope. So the total cross section is 10^23 x 10^-3 x 33.10^-24 = 10^-3 cm^2.

So one needs a neutron flux of about 10^9 neutrons per cm^2 per second to get this kind of induced radioactivity. That is several orders of magnitudes below what one has in a working reactor. But the activity found may also be several orders of magnitude below steady state.

Please correct me if there is a major error in this estimate.

If you are right and it looks like you are not wrong, we can be thankful the the producing element of all of those neutrons is spread over a wide area.

 

[KateB]

None of the experts on BWRs (from NRC training center) has contributed to this and shouldn't. If by mistake their feelings or assumptions were to get out before being fed to the IAEA, TEPCO or the Japanese Gov't they (NRC) would be in deep kimche.

See NRC's updates on assistance: http://www.nrc.gov/japan/japan-info.html"

This explains why no answers are easily forthcoming.

 

[Reno Deano]

I would recommend dumping charcoal over the areas where they believe the Iodine is emanating from. But, if wet it may loose it efficiency for trapping Iodine and other halogens. Using exhaust fans and Hepa filters and charcoal beds would be another method to control Iodine and fission product releases releases. Radioactive isotopes within the basement of turbine building could be from clogged drains and radwaste tank back ups. The turbine building also has drains to reactor building waste tanks. The turbines (and other associated systems) on BWRs do have buildup of radioactive corrosion products from the reactor via the steam used to power them. Doubtful, but if the MSIVs were to have been damaged there could be direct flow from the reactor to the Turbine building.

 

[|Fred]

In past reactor meltdowns, the Zirconium ran together with the Uranium or flowed out through steam releases like at Chernobyl. .

It was my understanding that meldown was basically the lost of part of the primary containment ie Ziralloy casing ; leading to a liquification of the fuel.
Once no longer in it's casing fission product (isotop) are free in the RCV, if they are noble gaz they are in the air, if they disolve in water they are in the water .. It is my undestanding that heavy metal isotops and stuff like Uranium can not be released through steam.. They need to be oxidized to break free in smoke.

I would recommend dumping charcoal

Yes.. Let's just do that and light a match.

 

[KateB]

Let us assume that the numbers http://www.nisa.meti.go.jp/english/files/en20110325-6.pdf are correct and that there really is a megabecquerel of Cl-38 per cm^3 in that water.

Suppose this is the steady state concentration in a certain neutron flux. Then the number of neutrons absorbed is equal to the number of decays. Let is suppose this is sea water, 3 % NaCl by weight. That is 30 milligrams of NaCl per cubic centimeter. Less than 1 millimole.

The cross section for neutron absorption of Cl-37 is 33 barns = 33 x 10^-24 cm. Only about a quarter of the chlorine consists of this isotope. So the total cross section is 10^23 x 10^-3 x 33.10^-24 = 10^-3 cm^2.

So one needs a neutron flux of about 10^9 neutrons per cm^2 per second to get this kind of induced radioactivity. That is several orders of magnitudes below what one has in a working reactor. But the activity found may also be several orders of magnitude below steady state.

Please correct me if there is a major error in this estimate.

Just to clarify (33 * 10^-24) * 10^-3 * 10^23? wouldn't that be 33 * 10^-4? (even lower values?)
I think that the prevalence of Cl-37 is less than 1/4 in sea water, though I don't believe it is low enough to cause a huge variation of your figures. BUT, and a BIG BUT. We have the issue of the steam leaving the salt behind creating a much larger percentage of NaCl to water, how does this change your estimation if at all?

 

[Joe Neubarth]

It was my understanding that meldown was basically the lost of part of the primary containment ie Ziralloy casing ; leading to a liquification of the fuel.
Once no longer in it's casing fission product (isotop) are free in the RCV, if they are noble gaz they are in the air, if they disolve in water they are in the water .. It is my undestanding that heavy metal isotops and stuff like Uranium can not be released through steam.. They need to be oxidized to break free in smoke.


Yes.. Let's just do that and light a match.

Well, technically, a melting of the Zirconium alloy would technically be a limited meltdown, it would be very difficult to keep the Uranium pellets in place. My understanding of past meltdowns was that at the bottom of the reactor (TMI) there was a good mixture between the fuel and the zirconium as well as trace amounts of Inconel and steel and chromium and so on and so forth.

 

[PietKuip]

Just to clarify (33 * 10^-24) * 10^-3 * 10^23? wouldn't that be 33 * 10^-4? (even lower values?)
I think that the prevalence of Cl-37 is less than 1/4 in sea water, though I don't believe it is low enough to cause a huge variation of your figures. BUT, and a BIG BUT. We have the issue of the steam leaving the salt behind creating a much larger percentage of NaCl to water, how does this change your estimation if at all?

It does not matter, this is just the grossest estimate of what a minimum neutron flux would be to achieve this level of activation of seawater. For that, the brine would have had to be in this neutron flux for about one half-life (30 minutes). And not have had time for decay. And not have been diluted. That is not realistic.

It seems that there was no water in that basement the day before. Suppose it had leaked in from the reactor 6 hours before they analyzed it. That is 12 half-times, and the activity would be 4000 times higher than when they measured the spectrum.

The uncertainties are gigantic, but something is very wrong. If the NISA numbers are correct, that reactor is still critical.