Are any of the Fukushima power plants still fissioning fuel?

[bilby]

How so?

The steering rods aren't liquid. I suggest googling the concept "critical mass". The steering rods regulate how much plutonium each plutonium unit is exposed to. By design, if the steering rods, are fully deployed, mean that there's not enough plutonium to react for critical mass. So then nothing happens. It just sits there. Forever.

The units in question are GE/Hitachi BWR-4 Mark I reactors; Fukushima Daiichi number 3 was fuelled with Mixed Oxide fuel which contains 6% Plutonium, but the reactors that melted down were fuelled with conventional Low Enriched Uranium, and not Plutonium.

These units were built between 1967 and 1971, and use light water both as coolant and moderator; in the presence of this light water, the reactor is brought below criticality by the insertion of Boron control rods. After the earthquake and tsunami, the reactors were shut down by these control rods. However due to loss of power (including the loss of the backup generators), coolant water could no longer be pumped through the cores, and the water already present boiled off - allowing the fuel elements to melt and flow into the bottom of the containment.

The resulting 'corium' mixture of melted and re-solidified reactor core components no longer has a confirmed or designed pattern of boron insertions, so the control rods may not be working as designed; but at that point it doesn't matter, as Low Enriched Uranium won't reach criticality in the absence of a moderator.

In the unlikely event that sufficient water penetrated the 'corium' to moderate the neutron flux and bring a part of the material towards criticality, the heat this generates would boil off the water, and the material would drop below criticality again.

So criticality is inherently not possible for the materials that are present in the melted reactor cores.

TL;DR - criticality is difficult to achieve; it cannot happen by accident in material that used to be a reactor before it melted down. The fuel simply isn't rich enough to go critical without a moderator.

 

[barbos]

The steering rods aren't liquid. I suggest googling the concept "critical mass". The steering rods regulate how much plutonium each plutonium unit is exposed to. By design, if the steering rods, are fully deployed, mean that there's not enough plutonium to react for critical mass. So then nothing happens. It just sits there. Forever.

The units in question are GE/Hitachi BWR-4 Mark I reactors; Fukushima Daiichi number 3 was fuelled with Mixed Oxide fuel which contains 6% Plutonium, but the reactors that melted down were fuelled with conventional Low Enriched Uranium, and not Plutonium.

These units were built between 1967 and 1971, and use light water both as coolant and moderator; in the presence of this light water, the reactor is brought below criticality by the insertion of Boron control rods. After the earthquake and tsunami, the reactors were shut down by these control rods. However due to loss of power (including the loss of the backup generators), coolant water could no longer be pumped through the cores, and the water already present boiled off - allowing the fuel elements to melt and flow into the bottom of the containment.

The resulting 'corium' mixture of melted and re-solidified reactor core components no longer has a confirmed or designed pattern of boron insertions, so the control rods may not be working as designed; but at that point it doesn't matter, as Low Enriched Uranium won't reach criticality in the absence of a moderator.

In the unlikely event that sufficient water penetrated the 'corium' to moderate the neutron flux and bring a part of the material towards criticality, the heat this generates would boil off the water, and the material would drop below criticality again.

So criticality is inherently not possible for the materials that are present in the melted reactor cores.

TL;DR - criticality is difficult to achieve; it cannot happen by accident in material that used to be a reactor before it melted down. The fuel simply isn't rich enough to go critical without a moderator.

Yes, reactor is in pre-meltdown state and structural integrity of the containment vessel is questionable, I remember reports of cracks in it.
Nobody knows how it will behave if there is a big earthquake, it could simply crack open and leak radioactive materials out.

 

[bilby]

The units in question are GE/Hitachi BWR-4 Mark I reactors; Fukushima Daiichi number 3 was fuelled with Mixed Oxide fuel which contains 6% Plutonium, but the reactors that melted down were fuelled with conventional Low Enriched Uranium, and not Plutonium.

These units were built between 1967 and 1971, and use light water both as coolant and moderator; in the presence of this light water, the reactor is brought below criticality by the insertion of Boron control rods. After the earthquake and tsunami, the reactors were shut down by these control rods. However due to loss of power (including the loss of the backup generators), coolant water could no longer be pumped through the cores, and the water already present boiled off - allowing the fuel elements to melt and flow into the bottom of the containment.

The resulting 'corium' mixture of melted and re-solidified reactor core components no longer has a confirmed or designed pattern of boron insertions, so the control rods may not be working as designed; but at that point it doesn't matter, as Low Enriched Uranium won't reach criticality in the absence of a moderator.

In the unlikely event that sufficient water penetrated the 'corium' to moderate the neutron flux and bring a part of the material towards criticality, the heat this generates would boil off the water, and the material would drop below criticality again.

So criticality is inherently not possible for the materials that are present in the melted reactor cores.

TL;DR - criticality is difficult to achieve; it cannot happen by accident in material that used to be a reactor before it melted down. The fuel simply isn't rich enough to go critical without a moderator.

Yes, reactor is in pre-meltdown state and structural integrity of the containment vessel is questionable, I remember reports of cracks in it.
Nobody knows how it will behave if there is a big earthquake, it could simply crack open and leak radioactive materials out.

Well, it could crack open if a big enough earthquake struck (an unlikely event, as the recent 9.0 quake has relieved a lot of built-up stress in the fault; the next big quake in Japan will likely strike elsewhere). But even if the containment were breached, the material in question is solid and dense. It's not going anywhere in a hurry; so as long as the plant isn't thronged with gawking tourists at the time, it's not going to pose much of a threat to anyone.

Highly radioactive materials are dangerous to get close to, but they don't go out looking for people to devour - Godzilla is fictional.

 

[barbos]

Yes, reactor is in pre-meltdown state and structural integrity of the containment vessel is questionable, I remember reports of cracks in it.
Nobody knows how it will behave if there is a big earthquake, it could simply crack open and leak radioactive materials out.

Well, it could crack open if a big enough earthquake struck (an unlikely event, as the recent 9.0 quake has relieved a lot of built-up stress in the fault; the next big quake in Japan will likely strike elsewhere). But even if the containment were breached, the material in question is solid and dense. It's not going anywhere in a hurry; so as long as the plant isn't thronged with gawking tourists at the time, it's not going to pose much of a threat to anyone.

Highly radioactive materials are dangerous to get close to, but they don't go out looking for people to devour - Godzilla is fictional.

There are gaseous isotopes which can later decay into less volatile one. I would not bet on vessel cracking open being not a big deal. Radioactive waste containment is a big problem even under controlled environment and here we are far from controlled environment. We have a pile of radioactive waste in the center of the city essentially.

 

[T.G.G. Moogly]

Well, it could crack open if a big enough earthquake struck (an unlikely event, as the recent 9.0 quake has relieved a lot of built-up stress in the fault; the next big quake in Japan will likely strike elsewhere). But even if the containment were breached, the material in question is solid and dense. It's not going anywhere in a hurry; so as long as the plant isn't thronged with gawking tourists at the time, it's not going to pose much of a threat to anyone.

Highly radioactive materials are dangerous to get close to, but they don't go out looking for people to devour - Godzilla is fictional.

There are gaseous isotopes which can later decay into less volatile one. I would not bet on vessel cracking open being not a big deal. Radioactive waste containment is a big problem even under controlled environment and here we are far from controlled environment. We have a pile of radioactive waste in the center of the city essentially.

Part of the problem was also the loss of water in the spent fuel rod assembly tanks. I remember seeing water canons directed at these using sea water as I recall until they could restore the water to the tanks. These fuel assemblies are spent but still radioactive enough that they can overheat when cooling water is lost.

 

[Loren Pechtel]

Well, it could crack open if a big enough earthquake struck (an unlikely event, as the recent 9.0 quake has relieved a lot of built-up stress in the fault; the next big quake in Japan will likely strike elsewhere). But even if the containment were breached, the material in question is solid and dense. It's not going anywhere in a hurry; so as long as the plant isn't thronged with gawking tourists at the time, it's not going to pose much of a threat to anyone.

Highly radioactive materials are dangerous to get close to, but they don't go out looking for people to devour - Godzilla is fictional.

Yup. https://what-if.xkcd.com/29/

 

[Loren Pechtel]

There are gaseous isotopes which can later decay into less volatile one. I would not bet on vessel cracking open being not a big deal. Radioactive waste containment is a big problem even under controlled environment and here we are far from controlled environment. We have a pile of radioactive waste in the center of the city essentially.

The only gaseous isotope I would expect to find in a reactor would be Krypton-85, Xenon-133, Xenon-135 and Xenon-136.

1) Things were busted open in the quake. I would expect any Krypton and Xenon that was there already escaped. Production shut down within a few minutes of the scram.

2) All of these beta emitters. Beta emitters are only dangerous if they are inside the body. Both of these are noble gases, they forms no compounds under normal conditions. (It has been forced into a few compounds in extreme conditions and with incredibly reactive stuff.) Thus it's ability to stay in the body is very minimal. Xenon is slightly more willing to react but still only with extremely energetic stuff that you won't find in the body.

3) It's normally vented anyway when the wind is blowing away from people.

4) As for the decay products:
Krypton-85, stable
Xenon-133, stable
Xenon-135, cesium-135 with a 2my half-life. The threat is very low
Xenon-136, stable. It doesn't really matter, though, as Xenon-136 has such a long half-life that it's decay is irrelevant. The page I'm looking this up on apparently overflowed, despite listing a decay sequence it's also showing it as "stable".

You're no doubt thinking of radon, but radon is a product of radioactive decay, not of fission. Putting the uranium in a reactor doesn't increase the radon production rate. In fact, the radon production rate will go down. The thing is the material was refined when it was made into reactor fuel--other elements were removed.

Starting from U-238 there are two short steps then a 240ky half life at U-234. Since U-234 would not be separated out I will restart from there:

U-234 has a half life of almost a quarter million years. The production rate is low. The next big step is 75ky at Th-230 and then another 1600 years at Ra-226 before we reach Rn-222. The radon production rate is exceedingly low and should be ignored.

Starting from the U-235 it's easier to get to radon, only one 32ky roadblock at Pa-231. However, this sequence produces Rn-219 which has a half life of under 4 seconds--it's not going much of anywhere!

If they added any plutonium to the fuel:

Pu-239--decays to U-235, 700my roadblock.
Pu-240--10gy roadblock at Th-232
Pu-241--radon is not produced.

 

[barbos]

There are gaseous isotopes which can later decay into less volatile one. I would not bet on vessel cracking open being not a big deal. Radioactive waste containment is a big problem even under controlled environment and here we are far from controlled environment. We have a pile of radioactive waste in the center of the city essentially.

The only gaseous isotope I would expect to find in a reactor would be Krypton-85, Xenon-133, Xenon-135 and Xenon-136.

1) Things were busted open in the quake. I would expect any Krypton and Xenon that was there already escaped. Production shut down within a few minutes of the scram.

2) All of these beta emitters. Beta emitters are only dangerous if they are inside the body. Both of these are noble gases, they forms no compounds under normal conditions. (It has been forced into a few compounds in extreme conditions and with incredibly reactive stuff.) Thus it's ability to stay in the body is very minimal. Xenon is slightly more willing to react but still only with extremely energetic stuff that you won't find in the body.

3) It's normally vented anyway when the wind is blowing away from people.

4) As for the decay products:
Krypton-85, stable
Xenon-133, stable
Xenon-135, cesium-135 with a 2my half-life. The threat is very low
Xenon-136, stable. It doesn't really matter, though, as Xenon-136 has such a long half-life that it's decay is irrelevant. The page I'm looking this up on apparently overflowed, despite listing a decay sequence it's also showing it as "stable".

You're no doubt thinking of radon, but radon is a product of radioactive decay, not of fission. Putting the uranium in a reactor doesn't increase the radon production rate. In fact, the radon production rate will go down. The thing is the material was refined when it was made into reactor fuel--other elements were removed.

Starting from U-238 there are two short steps then a 240ky half life at U-234. Since U-234 would not be separated out I will restart from there:

U-234 has a half life of almost a quarter million years. The production rate is low. The next big step is 75ky at Th-230 and then another 1600 years at Ra-226 before we reach Rn-222. The radon production rate is exceedingly low and should be ignored.

Starting from the U-235 it's easier to get to radon, only one 32ky roadblock at Pa-231. However, this sequence produces Rn-219 which has a half life of under 4 seconds--it's not going much of anywhere!

If they added any plutonium to the fuel:

Pu-239--decays to U-235, 700my roadblock.
Pu-240--10gy roadblock at Th-232
Pu-241--radon is not produced.

So, what you are saying is that radioactive waste is just ordinary waste and does not need any kind of special treatment?
You need to call US department of Energy if they still exist of course.

 

[Loren Pechtel]

So, what you are saying is that radioactive waste is just ordinary waste and does not need any kind of special treatment?
You need to call US department of Energy if they still exist of course.

You were suggesting the release of gaseous radioactive materials. I was addressing the fact that basically zero gaseous material should be produced from radioactive decay. The only gaseous material was produced during fission.

The waste is hazardous but it doesn't need the crazy level of containment that is being planned with things like Yucca Mountain.

Realistically, it's no more dangerous than many other toxic waste products.

 

[T.G.G. Moogly]

So, what you are saying is that radioactive waste is just ordinary waste and does not need any kind of special treatment?
You need to call US department of Energy if they still exist of course.

You were suggesting the release of gaseous radioactive materials. I was addressing the fact that basically zero gaseous material should be produced from radioactive decay. The only gaseous material was produced during fission.

The waste is hazardous but it doesn't need the crazy level of containment that is being planned with things like Yucca Mountain.

Realistically, it's no more dangerous than many other toxic waste products.

For purposes of discussion you now have total control of nuclear waste disposal. No one can tell you what to do or what not to do. What you say becomes reality wrt nuclear materials.

Please tell me your plan for spent fuel rod assemblies and all the material at Hanford and all radioactive waste and radioactive locations anywhere in the U.S.

If that's too much to handle let's simplify: A reactor was just refueled and you have six fuel rod assemblies to dispose of. What will you do with them?

 

[Loren Pechtel]

You were suggesting the release of gaseous radioactive materials. I was addressing the fact that basically zero gaseous material should be produced from radioactive decay. The only gaseous material was produced during fission.

The waste is hazardous but it doesn't need the crazy level of containment that is being planned with things like Yucca Mountain.

Realistically, it's no more dangerous than many other toxic waste products.

For purposes of discussion you now have total control of nuclear waste disposal. No one can tell you what to do or what not to do. What you say becomes reality wrt nuclear materials.

Please tell me your plan for spent fuel rod assemblies and all the material at Hanford and all radioactive waste and radioactive locations anywhere in the U.S.

If that's too much to handle let's simplify: A reactor was just refueled and you have six fuel rod assemblies to dispose of. What will you do with them?

Back up and reframe the problem. You're looking at it wrong. A "spent" fuel rod still contains about 90% of it's original fuel, it has just built up enough fission products that poison the reaction that it doesn't work correctly anymore. Thus the first step is to reprocess the stuff.

After you're done you have fuel: Send to the fabrication plant to make new fuel rods.
You have commercial isotopes: Sell them.
You have isotopes nobody wants: Toss them in an old salt mine in a dry climate. Packing them up would be preferred in case somebody finds a use for them and wants to mine the dump but it isn't essential.

 

[T.G.G. Moogly]

For purposes of discussion you now have total control of nuclear waste disposal. No one can tell you what to do or what not to do. What you say becomes reality wrt nuclear materials.

Please tell me your plan for spent fuel rod assemblies and all the material at Hanford and all radioactive waste and radioactive locations anywhere in the U.S.

If that's too much to handle let's simplify: A reactor was just refueled and you have six fuel rod assemblies to dispose of. What will you do with them?

Back up and reframe the problem. You're looking at it wrong. A "spent" fuel rod still contains about 90% of it's original fuel, it has just built up enough fission products that poison the reaction that it doesn't work correctly anymore. Thus the first step is to reprocess the stuff.

After you're done you have fuel: Send to the fabrication plant to make new fuel rods.
You have commercial isotopes: Sell them.
You have isotopes nobody wants: Toss them in an old salt mine in a dry climate. Packing them up would be preferred in case somebody finds a use for them and wants to mine the dump but it isn't essential.

I'm looking at it as it exists in the real world so you need to get more specific as to who is going to reprocess what and then where they will dispose of whatever is left over and for how long and under what conditions, etc.

Is it just like you common landfill turned community park like Mount Trashmore in Virginia Beach? Is it like the small scale facility near Carlsbad NM? Is it just a common landfill? Is it a capped landfill like a typical superfund site over which communities then build ball fields and tennis courts? Can you be more specific?

We're talking today, right now, you have the power to do whatever you want. with the technology and politics presently with a waste product that you say is not as dangerous as commonly perceived. So okay, what will you do with it exactly? Where is your salt mine or salt mines? How will you control access if even needed, for how long, etc.?

 

[Loren Pechtel]

I'm looking at it as it exists in the real world so you need to get more specific as to who is going to reprocess what and then where they will dispose of whatever is left over and for how long and under what conditions, etc.

Is it just like you common landfill turned community park like Mount Trashmore in Virginia Beach? Is it like the small scale facility near Carlsbad NM? Is it just a common landfill? Is it a capped landfill like a typical superfund site over which communities then build ball fields and tennis courts? Can you be more specific?

We're talking today, right now, you have the power to do whatever you want. with the technology and politics presently with a waste product that you say is not as dangerous as commonly perceived. So okay, what will you do with it exactly? Where is your salt mine or salt mines? How will you control access if even needed, for how long, etc.?

I don't understand your question about who will reprocess it. What's the issue there?

As for what to do afterwards, I already spelled it out: Toss it in an old salt mine in a dry climate. That's plenty adequate containment for the long term. For the short term it probably should be confined by some means but that need not be built to last the ages.

 

[bilby]

Back up and reframe the problem. You're looking at it wrong. A "spent" fuel rod still contains about 90% of it's original fuel, it has just built up enough fission products that poison the reaction that it doesn't work correctly anymore. Thus the first step is to reprocess the stuff.

After you're done you have fuel: Send to the fabrication plant to make new fuel rods.
You have commercial isotopes: Sell them.
You have isotopes nobody wants: Toss them in an old salt mine in a dry climate. Packing them up would be preferred in case somebody finds a use for them and wants to mine the dump but it isn't essential.

I'm looking at it as it exists in the real world so you need to get more specific as to who is going to reprocess what and then where they will dispose of whatever is left over and for how long and under what conditions, etc.

Is it just like you common landfill turned community park like Mount Trashmore in Virginia Beach? Is it like the small scale facility near Carlsbad NM? Is it just a common landfill? Is it a capped landfill like a typical superfund site over which communities then build ball fields and tennis courts? Can you be more specific?

We're talking today, right now, you have the power to do whatever you want. with the technology and politics presently with a waste product that you say is not as dangerous as commonly perceived. So okay, what will you do with it exactly? Where is your salt mine or salt mines? How will you control access if even needed, for how long, etc.?

This reads like the sort of 'gotcha' questions YECs ask of 'eviloutionists', convinced that the questions are unanswerable; The response to an actual answer is to simply refuse to accept that the answer could possibly be known, or to reject it as laughable (but without giving a reason).

Nuclear waste isn't a problem (or rather, it's an engineering problem with a number of well understood, tried and tested solutions that have been shown to be safe and effective). Despite massive opposition from 'green' groups to any plans for long-term repositories, which has led to quite a bit of this stuff being stored in temporary facilities for far longer than their design lifetimes, not one person has ever been injured (much less killed) as a result of exposure to commercial nuclear waste. Not one. In 60 years. If this material were really so dangerous and difficult to successfully store long-term, then surely someone would have received a medically significant exposure from it by now.

The commercial reprocessing of 'spent' fuel has been going on (successfully) for so long that one of the world's largest reprocessing facilities, THORP, has reached the end of its life, and is being decommissioned. This is mature technology; It works, and it has been working, with an exemplary safety record, for decades.

The 'green' lobbyists have been so busy and so vocal about how impossible it all is that they haven't noticed that the industry has been busy, quietly actually doing the thing that's supposedly impossible.

Meanwhile, they have also been ignoring the thousands of deaths from coal power plant waste materials, that are a direct result of their lobbying to persuade the public that nuclear waste is some kind of evil super-material that can never be tamed. It can be; It has been.

And all of this before we even consider MSR designs that can add spent fuel from Gen I, II and III reactors directly to their fuel stream, and simply burn it up without any requirement for significant reprocessing.

The answer to your question is that we can carry on doing what we have been doing for years with spent fuel; Or we can do some stuff that is less wasteful, such as building MSRs that can burn it as fuel. (as to the stuff at Hanford, that's a red herring - it's military waste, mostly from processes that are no longer done, and all from processes that IMO shouldn't have been done to begin with. It has as much to do with commercial nuclear electricity generation as the Zeppelin flammability issue has to do with the Boeing 787 project. However MSRs are not very picky about what they use for fuel, so doubtless they could play some part in helping the military to dig themselves out of this particular hole).

But then, if I'm so clever, why are there still monkeys?

 

[repoman]

techno utopian Bilby,

look at this:

http://news.nationalgeographic.com/energy/2015/12/151215-as-sea-levels-rise-are-coastal-nuclear-plants-ready/

 

[bilby]

techno utopian Bilby,

look at this:

http://news.nationalgeographic.com/energy/2015/12/151215-as-sea-levels-rise-are-coastal-nuclear-plants-ready/

I am aware of it - it's a trivial problem, and a part of a much wider problem with sea level rise.

As sea levels rise, stuff on the coast will need to be moved.

The only problem here is that fearmongering idiots want to claim that nuclear plants are somehow more difficult to move than other infrastructure, or more dangerous if inundated. But that's not true - all kinds of industrial sites face the same issues, and pose similar risks. More people by FAR have been injured (and no doubt many have died) due to dioxin pollution from the Tohoku earthquake and tsunami, than due to radiation from Fukushima; but for some reason, apparently nobody except the victims and their families cares.

If dangerous stuff getting washed into the ocean is your concern, nuclear power plants should be a long way down your list of things to worry about.

And of course, more nuclear power is the best way to rapidly lessen the degree of severity of sea level rises. Using sea level rise as an argument against nuclear power is fucking crazy.

Refusing to share a common delusion or phobia is not Utopianism. Lots of people are terrified by all kinds of modern technology; it's not techno-utopianism to suggest that they are foolish and wrong.

 

[repoman]

If all governments tried to put new and move old nuclear power plants to an elevation that would account for worst case scenario sea level rise, how much push back would they get?

 

[bilby]

If all governments tried to put new and move old nuclear power plants to an elevation that would account for worst case scenario sea level rise, how much push back would they get?

Loads.

ANYTHING 'nuclear' gets loads of pushback.

The medical imaging profession had to rebrand NMR (Nuclear Magnetic Resonance) as MRI (Magnetic Resonance Imaging), because the 'N' word was scaring patients.

The existence of fear is not evidence of a threat. Nor is it a reason to not do the right thing. But it is a very powerful influence on politicians, who don't care about what is right - they only care about what is popular.

 

[repoman]

Sorry, I meant pushback for zoning nuclear plants far enough away from the coast to still be safe after say 5-10 meters of sea level rise.

 

[bilby]

Sorry, I meant pushback for zoning nuclear plants far enough away from the coast to still be safe after say 5-10 meters of sea level rise.

I refer the honourable gentleman to the reply that I gave some moments ago.

'ANYTHING nuclear' includes (but is not necessarily limited to) everything to do with nuclear power plants, including construction, zoning, and decommissioning/replacement of such plants; their fuel (spent, unused, and partially used); and the buildings, sites and staffing of such facilities and supporting infrastructure as might be needed.