Liquid Nitrogen Injection Underground Last Defense

[rnc2]

Only assuming that the worst will happen and that will include the complete breaches through the bottom of the sealed containment of all four reactors, wouldn't it be possible, first, and then prudent, second, to be ready to cool these molten masses with liquid nitrogen being injected underground while capturing the gases with a type of canopy or other containment system? I know that any possible solution at this point would be most difficult to procure. It would be easier to be ready for this possible outcome now.

 

[Astronuc]

I don't believe such breaches have occurred or will occur. Injecting liquid nitrogen is not feasible, since liquid nitrogen requires a cryogenic vessel. It would be liquid in the ground.

 

[rnc2]

Thank you. How difficult or feasible to build circum containment under/around vessels now? Its hard to really get accurate info at present especially with Jp gvmnt cracking down on 'illegal' info! I'm finding.

 

[NUCENG]

Thank you. How difficult or feasible to build circum containment under/around vessels now? Its hard to really get accurate info at present especially with Jp gvmnt cracking down on 'illegal' info! I'm finding.

The plant foundations are on bedrock. One complication would be boring or tunneling through rock.

 

[rnc2]

As I understand it, the plant is elevated unlike Chernobyl where filling the containment vessels were possible, this option isn't available on the slope of the fukushima plant. 7 on a scale of 1-7 brings the worst possible outcomes to mind, doesn't it?

 

[Astronuc]

As I understand it, the plant is elevated unlike Chernobyl where filling the containment vessels were possible, this option isn't available on the slope of the fukushima plant. 7 on a scale of 1-7 brings the worst possible outcomes to mind, doesn't it?

The INES 7 rating is based on the release of I and Cs isotopes from 3 reactors cores, and at least one spent fuel pool. As far as we know, the reactor pressure vessels (RPVs) are intact, and I expect containments are flooded to the extent possible. Hence I don't expect corium, but the fuel is heavily damaged. I don't believe the fuel melted, but more likely the cladding is heavily oxidized/corroded and cracked or broken, and there may be significant fuel washout or dissolution.

 

[rnc2]

I imagine that there is a lot that is being reported to only the highest global authority that is making it harder for even the most educated of second guessing impossible. I think the Japanese government owes the most complete description known to all the peoples of the world. I'm sorry this is coming off more as a blog than technical data or report on my part. But of course we are all interested in how long until the eventual depletion of volitles entering the Earth's biosphere. Thank you for your info. I saw a lot of number crunching and tears during the Exxon Valdez spill, that too was an environmental catastrophe, but without the radionuclides. Now I will have to call Muktuk Nuktuk..

 

[Pengwuino]

I imagine that there is a lot that is being reported to only the highest global authority that is making it harder for even the most educated of second guessing impossible. I think the Japanese government owes the most complete description known to all the peoples of the world. I'm sorry this is coming off more as a blog than technical data or report on my part. But of course we are all interested in how long until the eventual depletion of volitles entering the Earth's biosphere. Thank you for your info. I saw a lot of number crunching and tears during the Exxon Valdez spill, that too was an environmental catastrophe, but without the radionuclides. Now I will have to call Muktuk Nuktuk..

If by blog, you mean crackpottish nonsense...

 

[joema]

...complete breaches through the bottom of the sealed containment of all four reactors, wouldn't it be possible, first, and then prudent, second, to be ready to cool these molten masses with liquid nitrogen being injected underground...

It's tempting to think of molten reactor core material as a "lava like" substance you could cool by spraying something on it. However:

Reactors #2 and #3 have nominal thermal outputs of 2.4 billion watts. At this point the thermal output has probably diminished to "only" 0.3%, but that's still 7.2 megawatts per reactor.

Note this is not residual heat like molten lava from a volcano -- it is being continuously generated from nuclear decay.

Liquid nitrogen's latent heat of vaporization is 199.1 kilojoules per kilogram. That's the heat energy 1 kg of LN2 would carry away if vaporized.

7.2 megawatts is 25.9 million kilojoules per hour, continuously. A huge semi tanker truck can carry about 30,000 liters (about 24,000 kg) of LN2. This equates to 24000*199 = 4.77 million kilojoules per truck.

So even if injecting LN2 into the ground picked up no heat from the earth, and the LN2 perfectly vaporized and carried away 100% of the possible nuclear decay heat, it would take: 25.9 million kj/hr / 4.77 million kj/truck = 5.4 trucks per hour, continuously.

That's for a single reactor. To cool four reactors would take about four times that many, or 20 trucks per hour. That's probably far beyond the maximum world manufacturing capacity for liquid nitrogen.

 

[rnc2]

Thank you. Continuously meaning generations? 40Million years? (Just to put this in complete perspective!) And for the record, do you know what solution the brightest minds have come up with so far for the long term? Breaking down the cores, transporting to underground, safer locations? Or just restoring as much order as possible to damaged facilities?

 

[Dmytry]

Not feasible there. Soviet union could do that during Chernobyl - using up all liquid nitrogen of western part of soviet union, that is to say, most of liquid nitrogen it had - using it also to deep freeze the *ground* under the reactor, actually. That minimizes steam formation when hot fuel lava reaches that ground.
Japan can't possibly do something similar, they can't just take all their liquid nitrogen and throw at it. The calculations above are correct. It is a lot of liquid nitrogen. In the ballpark of all of liquid nitrogen in Japan.
When Chernobyl is discussed in the west, it is always downplayed just how many resources were thrown at it. It is always presented as a worst possible disaster, most ineptly handled - but it wasn't so. Move it to capitalist country, and it will be a lot worse, because it'd be handled by the utility owning the reactor, with a little help.

With the 'drywells' flooded, there's no way anything is melting anywhere. If there's any risk of steam explosion, it'd happen long before it hits the ground.

 

[joema]

Thank you. Continuously meaning generations? 40Million years?..

The decay heat gradually diminishes: http://en.wikipedia.org/wiki/Decay_heat

Spent fuel is usually stored in pools for several years. After that it can be stored in dry casks.

Note this is necessary because of a high wasteful "once through" fuel cycle, which not only squanders most of the energy but creates highly radioactive waste which requires long-term storage: http://en.wikipedia.org/wiki/Nuclear_fuel_cycle

There are other well-known solutions which reduce high level waste to a small amount: http://en.wikipedia.org/wiki/Integral_Fast_Reactor

So technical solutions exist which could largely eliminate the waste problem, but for a variety of reasons haven't been used. And regardless of that it wouldn't change the 440 nuclear plants currently in operation worldwide.

 

[Dmytry]

There are other well-known solutions which reduce high level waste to a small amount: http://en.wikipedia.org/wiki/Integral_Fast_Reactor

So technical solutions exist which could largely eliminate the waste problem, but for a variety of reasons haven't been used. And regardless of that it wouldn't change the 440 nuclear plants currently in operation worldwide.

how so? You get same amount of fission products for the energy you get out. Except the fission products aren't immobilized anymore in small containers (pellets, and then, rods).

 

[QuantumPion]

Thank you. Continuously meaning generations? 40Million years? (Just to put this in complete perspective!) And for the record, do you know what solution the brightest minds have come up with so far for the long term? Breaking down the cores, transporting to underground, safer locations? Or just restoring as much order as possible to damaged facilities?

The power is decaying exponentially. After 2 months the power will be down to around 1 MW. After one year, ~300 kW. After 10 years, ~30 kW. After 100 years, 5 kW. After 1000 years, 1 kW.

Most of the long-term decay heat is produced by only a few isotopes though (sr-90, cs-137, am-241 and pu-239) which can be chemically separated and allowed to decay by themselves in a small shielded container.

 

[Dmytry]

The power is decaying exponentially. After 2 months the power will be down to around 1 MW. After one year, ~300 kW. After 10 years, ~30 kW. After 100 years, 5 kW. After 1000 years, 1 kW.

Most of the long-term decay heat is produced by only a few isotopes though (sr-90, cs-137, am-241 and pu-239) which can be chemically separated and allowed to decay by themselves in a small shielded container.

small, VERY WELL COOLED shielded container. Think about it, it'll be making same power, if you concentrate it, you have higher power density, smaller surface area for cooling it...

 

[rnc2]

Mobile, Super-Cooled, Shielded Containers with a decaying payload launched into the sun would be something new, ridding the Earth of all the contamination, right? It seems that such an endeavor would serve mankind better than colonizing the moon, no? I'm sure this is elementary and there are reasons its not feasable, probably safety, cost?

 

[QuantumPion]

small, VERY WELL COOLED shielded container. Think about it, it'll be making same power, if you concentrate it, you have higher power density, smaller surface area for cooling it...

It's not hard to cool 10 kW, in a steel cask natural convection would be sufficient.

Mobile, Super-Cooled, Shielded Containers with a decaying payload launched into the sun would be something new, ridding the Earth of all the contamination, right? It seems that such an endeavor would serve mankind better than colonizing the moon, no? I'm sure this is elementary and there are reasons its not feasable, probably safety, cost?

No. The Earth is a big place. There's plenty of room to tuck away hazardous materials where they can't harm anyone for thousands of years. Launching waste is risky, expensive, and pointless. Also it would take quite a large rocket to send any significant amount of material into the sun. There is no such thing as a "decaying solar orbit". In order to crash into the sun, you have to use thrusters to actively decelerate. It takes more delta-v to decelerate from Earth into the Sun than it does to leave the solar system entirely.

 

[Danuta]

Mobile, Super-Cooled, Shielded Containers with a decaying payload launched into the sun would be something new, ridding the Earth of all the contamination, right? ...

Sweet Jeeeebers, NOOOOOO! Just imagine a company like TEPCO winning the contract for that project. Just imagine an "incident" happening anytime between the launch(or even much before) and the payload vessel's deceleration so it can free fall into the sun(sort of).

Don't think about this anymore. Ever.

 

[GJBRKS]

The power is decaying exponentially. After 2 months the power will be down to around 1 MW. After one year, ~300 kW. After 10 years, ~30 kW. After 100 years, 5 kW. After 1000 years, 1 kW.

Most of the long-term decay heat is produced by only a few isotopes though (sr-90, cs-137, am-241 and pu-239) which can be chemically separated and allowed to decay by themselves in a small shielded container.

Its not quite exponential because of decay chains ,

it will still be 5 MW after 1 year :

http://mitnse.com/2011/03/16/what-is-decay-heat/

 

[joema]

how so? You get same amount of fission products for the energy you get out. Except the fission products aren't immobilized anymore in small containers (pellets, and then, rods).

Newer reactor designs like IFR and I think some Gen IV designs burn fission waste as fuel, converting it to a much smaller amount of waste with shorter life.

http://www.pbs.org/wgbh/pages/frontline/shows/reaction/interviews/till.html

 

[Dmytry]

Newer reactor designs like IFR and I think some Gen IV designs burn fission waste as fuel, converting it to a much smaller amount of waste with shorter life.

http://www.pbs.org/wgbh/pages/frontline/shows/reaction/interviews/till.html

and what it does to Cs-137 and Sr-90 ?

 

[joema]

and what it does to Cs-137 and Sr-90 ?

Those have short half lives and are not a long term storage problem. By far the most difficult nuclear waste problem are transuranics which have very long half lives and require storage for many thousands of years. Those are greatly reduced (I think by a factor of 50 or 100).

Maybe someone with more technical knowledge could comment further.

 

[QuantumPion]

Its not quite exponential because of decay chains ,

it will still be 5 MW after 1 year :

http://mitnse.com/2011/03/16/what-is-decay-heat/

Although the rate changes as different isotopes are responsible for the majority of the head load at different times, it is still exponential.

I directly calculated the heat load using Origen for Fukushima Unit 1. The other units have nearly double the rated thermal power, so roughly double the decay heat load. Furthermore, that article's assumption is:

*Values for the decay heat were calculated based on assuming an infinite reactor operation time prior to shutdown. Infinite operation is a conservative assumption, and actual values may be significantly lower than those that are shown in the figure and table.

Which is massively over-conservative, especially since the units have a low capacity factor.

 

[Dmytry]

Those have short half lives and are not a long term storage problem. By far the most difficult nuclear waste problem are transuranics which have very long half lives and require storage for many thousands of years. Those are greatly reduced (I think by a factor of 50 or 100).

Maybe someone with more technical knowledge could comment further.

ahh, the features to please typical public who thinks if something got long half life it means its the worst.
Also, IFR lol. Another of those liquid sodium cooled reactors that never survive for any length of time without developing a big scary liquid sodium leak due to material problem. You think it is easy to make piping, valves, etc etc for liquid sodium ? The reason water is common coolant is that long term behaviours of materials in hot water are well studied. Unlike hot molten sodium. A good idea it may be, slain by ugly engineering issues.

 

[QuantumPion]

Those have short half lives and are not a long term storage problem. By far the most difficult nuclear waste problem are transuranics which have very long half lives and require storage for many thousands of years. Those are greatly reduced (I think by a factor of 50 or 100).

Maybe someone with more technical knowledge could comment further.

The long-lived products like Pu and Am have low activity (by definition) and are primarily alpha emitters (easy to shield). These are the easiest parts to deal with when considering reprocessing spent fuel.

The most troublesome isotopes are the medium-life ones which are active enough to pose a hazard but long enough to stick around for a while. These are Sr-90, Cs-137, Tc-99, Sn-126, etc.

 

[QuantumPion]

ahh, the features to please typical public who thinks if something got long half life it means its the worst.
Also, IFR lol. Another of those liquid sodium cooled reactors that never survive for any length of time without developing a big scary liquid sodium leak due to material problem. You think it is easy to make piping, valves, etc etc for liquid sodium ? The reason water is common coolant is that long term behaviours of materials in hot water are well studied. Unlike hot molten sodium. A good idea it may be, slain by ugly engineering issues.

No reason why you couldn't make a gas cooled fast reactor if you wanted to go that route.

 

[Dmytry]

No reason why you couldn't make a gas cooled fast reactor if you wanted to go that route.

Well he was repeating the IFR nuclear optimism. It's same pattern always. Nuclear optimists, with no real knowledge of issues involved, every single different reactor design is toured as new super duper thing that's going to solve all the problems. 'Inherently safe' is a very popular buzzword, used to capitalize on public ignorance of decay heat.
On topic of fuel re-processing. The point is, after you did some re-processing of fuel, the total thermal output is same. Whatever you do, spent fuel is hard to keep safe for first few years. Yes, if you separate out those fission products, you don't have to worry about re-criticality any more, which is probably the only advantage. Instead, you now got some liquid, and you need some complicated chemistry to turn it into some high melting point solid for safe storage. Not easy to do.
For the exponential: it is actually a sum of several exponents.

 

[joema]

The long-lived products like Pu and Am have low activity (by definition) and are primarily alpha emitters (easy to shield). These are the easiest parts to deal with when considering reprocessing spent fuel.

The most troublesome isotopes are the medium-life ones which are active enough to pose a hazard but long enough to stick around for a while. These are Sr-90, Cs-137, Tc-99, Sn-126, etc.

Sr-90 and Cs-137 have half lives of about 30 years. Isn't it the isotopes with longer half lives that create the need for expensive, controversial geologically stable storage like Yucca Mountain?

Why would you need to validate something is geologically stable for 10,000 years to store something with a 30 year half life?

 

[QuantumPion]

Why would you need to validate something is geologically stable for 10,000 years to store something with a 30 year half life?

To provide jobs for geologists, bureaucrats, and political contributions for politicians.

 

[rnc2]

Danuta Thanks for setting me straight. LOL

 

[Dmytry]

To provide jobs for geologists, bureaucrats, and political contributions for politicians.

and to advocate those liquid metal cooled fast neutron reactors which have certain fuel economy advantages, but are otherwise a nightmare. The idea may be neat, and the material issues might be solvable, in theory, but in practice - there is a lot more experience handling hot water than any other liquid.