The Nuclear Power Thread

[Astronuc]

A perspective on materials and advanced nuclear systems.

http://www.lanl.gov/conferences/marie/decadal/docs_open/Decadal-Plenary_Talk-Maloy1.pdf

 

[Astronuc]

Thorium

Safety and Regulatory Issues of the Thorium Fuel Cycle

http://pbadupws.nrc.gov/docs/ML1405/ML14050A083.pdf

Note the authors are from ORNL.

Thorium has been widely considered an alternative to uranium fuel because of its relatively large natural abundance and its ability to breed fissile fuel (²³³U) from natural thorium (²³²Th). Possible scenarios for using thorium in the nuclear fuel cycle include use in different nuclear reactor types (light water, high temperature gas cooled, fast spectrum sodium, molten salt, etc.), advanced accelerator-driven systems, or even fission-fusion hybrid systems. The most likely near-term application of thorium in the United States is in currently operating light water reactors (LWRs). This use is primarily based on concepts that mix thorium with uranium (UO₂ + ThO₂), add fertile thorium (ThO₂) fuel pins to LWR fuel assemblies, or use mixed plutonium and thorium (PuO₂ + ThO₂) fuel assemblies.

And FYI - Regulation of Radioactive Materials
http://www.nrc.gov/about-nrc/radiation/protects-you/reg-matls.html

 

[mheslep]

I'm curious how the breeding chain in a solid fuel Th based breeder works. That is, I understood that once the Th232 breeds into Pa233, the Pa then had to be continually removed from the core while it decayed in days to U233, else a high fraction was likely to undergo neutron capture. Continual removal of Pa233 is a resolvable chemical and plumbing problem in a molten reactor, but I don't follow how it is possible in a solid fueled LWR.

 

[Astronuc]

I'm curious how the breeding chain in a solid fuel Th based breeder works. That is, I understood that once the Th232 breeds into Pa233, the Pa then had to be continually removed from the core while it decayed in days to U233, else a high fraction was likely to undergo neutron capture. Continual removal of Pa233 is a resolvable chemical and plumbing problem in a molten reactor, but I don't follow how it is possible in a solid fueled LWR.

I'll try to find some information on Th-U233 programs.

Meanwhile - the Lightbridge patents on a Th-inspired novel fuel design for LWR and CANDU fuel.

http://www.google.com/patents/US20110255651
http://www.google.com/patents/US20130322591
http://www.google.com/patents/US20110311016

http://apps.shareholder.com/sec/vie...=AMDA-16UEEM&docid=9884078#FORM10K_HTM_PAGE_5 (see page 7)
KEY FUEL DEVELOPMENTS IN 2013

 

[Hologram0110]

I'm curious how the breeding chain in a solid fuel Th based breeder works. That is, I understood that once the Th232 breeds into Pa233, the Pa then had to be continually removed from the core while it decayed in days to U233, else a high fraction was likely to undergo neutron capture. Continual removal of Pa233 is a resolvable chemical and plumbing problem in a molten reactor, but I don't follow how it is possible in a solid fueled LWR.

In one of my graduate classes we wrote programs to simulate refueling of a thorium CANDU. The fissile material in this 'reactor' was U-233 at the discharge concentration (i.e. self sustaining in terms of fissile material, breeding ratio of 1). Note that this configuration gets terrible discharge burnup and you would likely want to include U-235 or Pu-239 rather than rely entirely on thorium in this configuration. We established a few strategies for improving U-233 yield and avoiding capture in Pa233. The first idea was to cycle fuel in and out of the reactor, such that the Pa233 is given time to decay to U-233. The optimal timing is just before a saturation concentration of Pa233 is reached. The second idea is low volumetric power (the decay-to-capture ratio is inversely proportional to the thermal neutron flux).

Obviously both these ideas have downsides. The first requires VERY frequent refueling which puts heavy demands on the refueling machines (currently a weak link in some Candu plants). It also requires large fuel inventories. The second idea hurts the capital cost of a plant (already a problem for CANDU units).

In our analysis, we decided to run at full power with no fancy refueling techniques. Our argument was that thorium is cheap and for this to work recycling/processing is clearly required and economic. If any of these things are not true, you should really be including more fissile material initially to increase burnup.

 

[wizwom]

I am currently working on Thorium breeding in solid fuel. Just as with solid fuel breeding in Uranium, it sits in situ and breeds up, then is reprocessed to recover the fissile material. There is no reason that Pa must be cycled out fast, U234 production is really not a problem unless you are looking for bumb-grade material.
The thermal cross section for Pa233 is 140 ± 20 according to Halperin et. al 1956.
In my solid fuel Thorium ADEP study with CINDER, U233 to U234 is turning out to 1500:1 and U233 to Pa233 8.3:1 (3.15567E+07 S, FLUENCE (N/CM**2) =1.07628E+21, initial HM 95% Th232 5% Pu)

 

[mheslep]

In one of my graduate classes we wrote programs to simulate refueling of a thorium CANDU. The fissile material in this 'reactor' was U-233 at the discharge concentration (i.e. self sustaining in terms of fissile material, breeding ratio of 1). ...

In our analysis, we decided to run at full power with no fancy refueling techniques. Our argument was that thorium is cheap and for this to work recycling/processing is clearly required and economic. If any of these things are not true, you should really be including more fissile material initially to increase burnup.

Thanks for this.

It seems to me the problem would not be the waste of thorium, but the loss of a neutron on Pa-233, and another on the subsequent U-234, both with good capture cross section. With all that you still calculated a sufficient breeding ratio? Or is the answer to keep adding other fissile material until it does? If so then the design adds back the long lived actinides to the waste stream, the lack of which was one advantage of the thorium reactor.

 

[Astronuc]

Thanks for this.

It seems to me the problem would not be the waste of thorium, but the loss of a neutron on Pa-233, and another on the subsequent U-234, both with good capture cross section. With all that you still calculated a sufficient breeding ratio? Or is the answer to keep adding other fissile material until it does? If so then the design adds back the long lived actinides to the waste stream, the lack of which was one advantage of the thorium reactor.

About 11% of neutrons captured by U233 produce U234 rather than fission, with a small amount of U234 coming from Pa234 decay. U234 is parasitic, but it's absorption by neutrons produces U-235, which is fissionable, although some forms U236, which leads to Np236, or n-capture to U237, which leads to Np237, but at much smaller levels than in LWR fuel containing U235 fissile material. Without U238, the transuranics are relatively low.

Breeder cores are designed with reflectors, since any core will 'leak' neutrons. So the reflector are used to reflect neutrons back to the active core, and use the neutrons that don't leak for converting fertile material to fissile material. The other benefit is to reduce neutron fluence to the containment/pressure vessel that holds the core.

Fuel Summary Report: Shippingport Light Water Breeder Reactor
http://www.inl.gov/technicalpublications/Documents/2664750.pdf

A summary of the Shippingport experience with thoria-based fuel. I communicated with the author for one project I did about 25 years ago.
http://large.stanford.edu/courses/2009/ph204/coleman1/docs/10191380.pdfArticle in American Scientist - needs subscription or purchase.
http://www.americanscientist.org/my_amsci/restricted.aspx?act=pdf&id=36745203226947
The image shows 'green' pellets, i.e, the thoria-urania powder combined with binder and die lubricant has been pressed, usually to about 50-60% of theoretical density (TD) of the stoichiometric ceramic, and awaiting sintering, in a furnace at about 1700-1800 C. It will probably achieve ~95 to 96% of TD.

Criticism - http://www.americanscientist.org/issues/pub/2010/6/not-so-fast-with-thorium

The criticism of the HTGR has nothing to do with thorium. It has to do with the fuel and reactor technology at the time, and the same would have happened with U-based fuel. Similarly, Shippingport was the first large LWR system to be devoted to commercial electricity. It was scheduled for shutdown, and researchers took advantage of it to load the core with thorium-based fuel as a demonstration. There were issues with the thorium fuel cycle at the time, mainly the breeding and reprocessing part, and some of those difficulties made it less attractive than the uranium-based fuel cycle. Of course, there were strong economic interests concerning the use of uranium.

We have learned a lot since then.

 

[Hologram0110]

Thanks for this.

It seems to me the problem would not be the waste of thorium, but the loss of a neutron on Pa-233, and another on the subsequent U-234, both with good capture cross section. With all that you still calculated a sufficient breeding ratio? Or is the answer to keep adding other fissile material until it does? If so then the design adds back the long lived actinides to the waste stream, the lack of which was one advantage of the thorium reactor.

The sustaining fuel was actually a pretty poor performer, this was just an academic exercise. The discharge burn-up was very low meaning it would generate large volumes of waste (because the initial U-233 concentration is so low).

Assuming a simple thermal flux it is possible to calculate how much Pa-233 captures a neutron instead of beta decay to U233. Pa-233 has a microscopic cross-capture cross-section of ~42.5 b and has a 27 day half-life (decay constant = 2.97e-07 /s). Therefore the ratio is 42.5e-28*Φ/2.97e-07 =
1.43E-20*Φ (where the flux is neutrons per meter squared per second). Thus the lower the neutron flux the greater the conversion ratio. Obviously if you want to account for energy dependence of the neutrons this gets more complicated, but this should give you an idea.

 

[mheslep]

...

Assuming a simple thermal flux it is possible to calculate how much Pa-233 captures a neutron instead of beta decay to U233. Pa-233 has a microscopic cross-capture cross-section of ~42.5 b and has a 27 day half-life (decay constant = 2.97e-07 /s). Therefore the ratio is 42.5e-28*Φ/2.97e-07 =
1.43E-20*Φ (where the flux is neutrons per meter squared per second). Thus the lower the neutron flux the greater the conversion ratio. Obviously if you want to account for energy dependence of the neutrons this gets more complicated, but this should give you an idea.

I think the main consideration is not per-se the cross-section of Pa-233, but rather its cross-section *versus* that of the fertile Th-232: Pa-233 cross-section is five times that of Th-232 (7.4 b, thermal). If the generated Pa-233 is never removed from the reactor, continued breeding of U-233 must become unsustainable.

 

[Hologram0110]

I think the main consideration is not per-se the cross-section of Pa-233, but rather its cross-section *versus* that of the fertile Th-232: Pa-233 cross-section is five times that of Th-232 (7.4 b, thermal). If the generated Pa-233 is never removed from the reactor, continued breeding of U-233 must become unsustainable.

I do not follow. Assuming the Th-232 makes up the bulk of the fuel, its concentration is effectively static. This means that the Pa-233 will eventually reach an equilibrium concentration which depends on the reactor flux (it both decays and transmutes) - therefore it doesn't increase indefinately. Are you concerned about the Pa-233 acting as a neutron poison lowering the reactivity of the fuel at the equilibrium concentration? If that is the case you simply need more fissile material to counteract the negative reactivity due to Pa-233. Yes at some point the fuel needs to be replaced just like any other fuel.

Perhaps I was unclear about what I meant by self sustaining fuel. This didn't mean self sustaining without reprocessing. It means the discharge concentration of your fissile material is roughly the initial concentration. Therefore reprocessing involves removing the fission products and topping up the fertile material (Th-232 in this case).

 

[Astronuc]

I think the main consideration is not per-se the cross-section of Pa-233, but rather its cross-section *versus* that of the fertile Th-232: Pa-233 cross-section is five times that of Th-232 (7.4 b, thermal). If the generated Pa-233 is never removed from the reactor, continued breeding of U-233 must become unsustainable.

One has to look at the macroscopic cross section, which is the product of atomic density, N, and microscopic cross section, $\sigma$. The initial concentration of Pa-233 would be nil, and it builds up over time, but as Hologram indicated, it's a small fraction of the total atoms and there is still much more Th-232.

Update: Role of Thorium to Supplement Fuel Cycles of Future Nuclear Energy Systems
http://www-pub.iaea.org/MTCD/Publications/PDF/Pub1540_web.pdf

 

[Astronuc]

MIT NSE Optimistic about the future of fusion power
http://newsoffice.mit.edu/sites/mit.edu.newsoffice/files/styles/article_cover_image_small/public/images/2014/lester-delfavero-hartwig-whyte.JPG?itok=wnYKYo0D
In inaugural Del Favero Doctoral Thesis Prize Lecture, Zach Hartwig PhD '14 explains why fusion research should be at the top of NSE's agenda.
http://newsoffice.mit.edu/2014/del-favero-lecture-zach-hartwig-future-fusion-power-1216

 

[dlgoff]

Yah!

NEW DELHI — The United States and India reached a deal Sunday to change on liability laws that its leaders say will allow American companies to invest in nuclear energy development in India.

http://www.newsobserver.com/2015/01/25/4503390/us-india-reach-compromise-on-troubled.html

 

[jim hardy]

hmmm article didn't say what is the agreement.
I pray it doesn't leave US taxpayers on the hook for mistakes over there.

Fukushima lies in the lap of whoever chose not to act on the information about 'recent' giant tidal waves there.
Product Liability laws bite from both ends -- Notice how fast the Toyota gas pedal issue disappeared after those GE plants blew up?

 

[Lee shannon]

There is at least one major unsolved problem with nuclear power. What do you do with the spent fuel? Right now it just accumulates at the various plant sites. Yucca mountain is still iffy as a long term solution.

well if anyone in power could get there heads out of there asses long enough to cough up the required funds we could just fire it off in the general direction of the sun and let it burn up the wast for us
using our current space going capacity and it would require almost no additional infrastructure at all just small high output propulsion system attached to a shielded (shielded against the nuclear radiation getting out and killing the astronauts who brought it into space with them) and a rudimentary guidance system
point it in the right direction and fire
And you have now solved all your nuclear wast problems.

 

[Jon Richfield]

well if anyone in power could get there heads out of there asses long enough to cough up the required funds we could just fire it off in the general direction of the sun and let it burn up the wast for us
using our current space going capacity and it would require almost no additional infrastructure at all just small high output propulsion system attached to a shielded (shielded against the nuclear radiation getting out and killing the astronauts who brought it into space with them) and a rudimentary guidance system
point it in the right direction and fire
And you have now solved all your nuclear wast problems.

 

[Jon Richfield]

well if anyone in power could get there heads out of there asses long enough to cough up the required funds we could just fire it off in the general direction of the sun and let it burn up the wast for us
using our current space going capacity and it would require almost no additional infrastructure at all just small high output propulsion system attached to a shielded (shielded against the nuclear radiation getting out and killing the astronauts who brought it into space with them) and a rudimentary guidance system
point it in the right direction and fire
And you have now solved all your nuclear wast problems.

Two problems, one small, one big.
Small: there is no point to disposing of low and intermediate level waste in such an expensive manner. The stuff is pretty harmless even if it does escape, and it simply could be stored above-ground in any of umpteen ways that resist transport for a few centuries.
High level waste is indeed dangerous; hoisting it off-planet not only would be would be expensive, but unsafe as well until some genius works out how to do it with a flat guarantee of nothing falling back to Earth in the wrong form or the wrong place. (Did I hear someone say "Challenger"?)
Big: insisting on permanently sequestering or otherwise disposing of high level material such as spent fuel, whether by permanent sequestration or safe disposal, is criminally short-sighted; the fact that it is no longer suitable for use in the form for which it was fabricated, does not mean that it is not valuable or that it is replaceable or difficult to store safely. The demand that ALL high-level material be so sequestered that no trace or emanation ever could escape and that no one ever could stumble over it in the millions of years that it would take its longest-lived isotopes or products to decay into less harmful forms than say natural potassium is not only unrealistic but irrelevant when the main risks are rather on the scale of decades and the volume of material is tiny, which generally is the case.

Almost the only really biologically dangerous isotope that offers any challenge to contain is tritium, and maybe some Na isotopes, and they are not much of a challenge, given their chemical nature and quantities. Instead of obsessively trying to bury them immediately and forever, the sane thing is to store the material where it can cool down till it is manageable to handle. That isn't terribly challenging; the history of theft of high-level waste is so encouraging that it inspires faith in the progressive improvement of human honesty.
Then why shouldn't we store it (above ground, I reckon, but conveniently in available chambers if someone insists) in a place that presents no marine or volcanic threats and that is reasonably weather-proof? Many desert nature reserves would be perfect. Most unapproachable nuclear hazards or processing or power plants are already de facto reserves. I live near a couple. They are great! And not unique either; ask naturalists that have inspected the evacuated regions round Chernobyl.
It would be important to catalog what is where, against the time that people begin to wonder where to get some of it out again for new use or re-use.
The storage medium should be in a form that could be extracted efficiently, but not rapidly, nor without special equipment, nor in particular inconspicuously. It should be indifferent to earthquake, fire or flood, and in particular to corrosion. Something like hundred-tonne cargo containers with special multiple walls and requiring special tools and much time to breach, and producing long-range distress signals if moved without approval, should do nicely. They even might be powered by waste heat from their own contents. Compared to alternatives such as vitrification (not to mention lifting into space) such storage would be dirt cheap and it all could be used up long before all the important half-lives had expired.
So who needs space launching or deep burial or indeed, long term storage at all? A few centuries should be plenty. Anything likely to survive after that, we could cheerfully burn down to inactivity in a high neutron flux unit.

 

[Jon Richfield]

@Astronuc in particular, but anyone is welcome. A question: I am keen on nukes, but am no nuclear engineer, and I had for long been under the impression that nuclear plants could be scrammed, typically by dumping them into enough water. Then came Fukushima. Wellll... there was a slight hiccup as Jim Hardy observed, concerning tsunamis, but not that the tsunamis never actually broke the plants badly. As I understand it the problem was
1: The tsunamis certainly did disrupt infrastructure in the region.
2: Water supply for scramming depended on the infrastructure.
All the other items I could have regarded with equanimity, but that combination struck me (a nuke freak, please note!) as simply crazy. To have ANY dependence on ANYTHING not fail-soft I would regard as totally nuts. So it would mean maintaining a reservoir of what... a million tonnes of water uselessly (pick a figure)? Under conditions that require no power to supply? And that would have cost how many millions of dollars extra? As compared to what the present rectification is costing and the direct harm that is accruing? (Never mind the political harm!)
SO: am I overlooking something?
And: let me guess: Fukushima is not the only place where fail-safe scramming is not available?

 

[Astronuc]

As we understand the information from TEPCO, the operating reactors at Fukushima (Units 1, 2 and 3) did scram on signals related to the earthquake. The nuclear reaction did shutdown. BWR control rods are hydraulically operated, and all rods, as far as we know, were inserted as designed.

However, after a reactor shuts down, there are still fission products undergoing beta decay (or alpha decay for some transuranics), and gamma decay. The 'decay heat' must be removed by the coolant. After the coolant pumps shutdown, there should be a residual heat removal system that continues to circulate water to cool the reactor core. That heat is transferred through heat exchangers to the environment - in the case the ocean (other plants discharge heat to rivers, lakes or reservoirs, or in cooling towers to the atmosphere).

There is are simple overview of decay heat as it relates to the Fukushima reactors here - http://mitnse.com/2011/03/16/what-is-decay-heat/

Note the heat rate as a function of time after the accident.

The problem at Fukushima is that they lost the cooling of the reactor. It appears that some of the piping may have broken, in which case, water simply drained out of the pressure vessel without getting to the core. A core sitting in stagnant steam can get pretty hot, and in steam, oxidation may take place, and that is where the hydrogen would be generated. The hydrogen leaked out and ignited causing the explosions that further damaged the containment.

Without heat removal from the core, the fuel temperature continues to rise. I suspect there where chemical reactions between the fuel and coolant, and it's possible the fuel cladding and core structure began to melt. From the release of fission products, we know the fuel in the core was breached. Xe, Kr gases, and I, which is a volatile, were released, while most of the other fission products would dissolved in the water.

 

[nikkkom]

@Astronuc in particular, but anyone is welcome. A question: I am keen on nukes, but am no nuclear engineer, and I had for long been under the impression that nuclear plants could be scrammed, typically by dumping them into enough water.

No. SCRAM is done by inserting all control and safety rods at once.

There are neither operational plans nor water allocated for flooding the containment. I found it surprising too.

All the other items I could have regarded with equanimity, but that combination struck me (a nuke freak, please note!) as simply crazy. To have ANY dependence on ANYTHING not fail-soft I would regard as totally nuts. So it would mean maintaining a reservoir of what... a million tonnes of water uselessly (pick a figure)? Under conditions that require no power to supply? And that would have cost how many millions of dollars extra? As compared to what the present rectification is costing and the direct harm that is accruing? (Never mind the political harm!)

I posted somewhat similar posts numerous times last few years.
Apparently our "nuclear people" managed to convince themselves that extended power outages won't happen. More amazingly, many STILL insist that planning for that is not necessary.

Fukushima is not the only place where fail-safe scramming is not available?

Well, scramming does seem to work. But yes, planning for reliable cooling of scrammed reactors in emergency such as extended power outage does not seem to be a priority even now. Neither filters on emergency vent lines.

I am no longer a supporter of nuclear power.

 

[Jon Richfield]

As we understand the information from TEPCO, the operating reactors at Fukushima (Units 1, 2 and 3) did scram on signals related to the earthquake. The nuclear reaction did shutdown. BWR control rods are hydraulically operated, and all rods, as far as we know, were inserted as designed.

However, ...

Thanks Astronuc, that was helpful.

 

[Astronuc]

I should add that the tsunami took out the fuel supply for the emergency diesel generators, so they quit. The tsunami also flooded the basements and shorted the electrical bus and flooded the emergency diesel generators, which are the major long term supply of electricity to the site when the transmission lines go down.

With electricity pumps and valves are inoperable, so even though the core is scrammed, the plant still needs the cooling system to function. Without power, the cooling system failed.

 

[Jon Richfield]

No. SCRAM is done by inserting all control and safety rods at once.

I am not sure whether you are referring (correctly) to Fukushima in particular, or (incorrectly) in general to nuclear reactors. The nature of a SCRAM varies with the reactor type. I had perhaps misused the term by extending it to cover flooding the reactor. However it seems that we agree on the need for a reactor design to include fail safe removal of waste heat, whether from isotopic decay, Wigner energy or any other post-SCRAM sources, whether by flooding or other realistic means.

I assume that we also agree that any design that could rationally be expected to permit failure of such safety features in a commercial or industrial installation would be unconditionally unacceptable. And I speak as (unlike you, it seems) a continuing nuclear power enthusiast.

Apparently our "nuclear people" managed to convince themselves that extended power outages won't happen. More amazingly, many STILL insist that planning for that is not necessary.

Here I share your amazement and no doubt your dismay. Accepting your remark at face value (I was not aware of such statements or views) I cannot accept that any engineer with such attitudes understands either engineering responsibilities or the statistics of disaster cost-benefits. And as you imply, to deny the responsibility to install filters on emergency vent lines strikes me as flatly irrational, even bearing in mind that they cannot filter out everything.

I am no longer a supporter of nuclear power.

There however, we diverge. The fact that nuclear power demands greater responsibility than many politicians and engineers display does not persuade me that the only or even the only rational alternative is to give up on such an important option for our most important resource, namely power.

 

[jim hardy]

Edit - oops i see other posts appeared whilst i was typing...

Without heat removal from the core, the fuel temperature continues to rise.

@ Jon --- That's the crux of it right there.

It has been long known that loss of all power for that generation of plants would lead to , well, just what happened.
For that reason they have redundant pumps, pipes, and heat exchangers, and redundant batteries, redundant diesel generators located in the basement where they're safe from earthquakes, redundant instruments and so on and so on.

Current designs do incorporate things like gravity fed heat removal and standardized connections for simple things like portable pumps and generators.How different might Fukushima turned out had some electrician found a few gasoline motor driven welding machines (ones that weren't full of seawater) and hooked them to the batteries?

Observe the two newer units there (5&6 ?), the ones with diesels higher up the hill, fared okay.
That those diesels were put way up there... hmmmm

Sorry for the ramble.

Glad to hear you aren't Anti-Nuke.
Thank you.

old jim

 

[Jon Richfield]

Edit - oops i see other posts appeared whilst i was typing...

@ Jon --- That's the crux of it right there.
...
Sorry for the ramble.

Glad to hear you aren't Anti-Nuke.
Thank you.

old jim

Hi Jim, no problem with the ramble. Interesting stuff. Here in South Africa we are helplessly watching developments and wondering whether our government is going to buy a job lot of VVER/PWRs. From Russia. I am left trying to imagine a worse prospect than combining Russian diplomatic free enterprise and control of their own installations, with our local politicians opportunism and Nuke nous. AFAIK most of them don't know kVA from kava and don't care as long as someone promises that their take-home pay will expand. Nukes I can follow with the help of some of the folks round here, but some things are beyond my conception, never mind comprehension.

 

[nikkkom]

Then why shouldn't we store it (above ground, I reckon, but conveniently in available chambers if someone insists) in a place that presents no marine or volcanic threats and that is reasonably weather-proof? Many desert nature reserves would be perfect. Most unapproachable nuclear hazards or processing or power plants are already de facto reserves. I live near a couple. They are great! And not unique either; ask naturalists that have inspected the evacuated regions round Chernobyl.
It would be important to catalog what is where, against the time that people begin to wonder where to get some of it out again for new use or re-use.
The storage medium should be in a form that could be extracted efficiently, but not rapidly, nor without special equipment, nor in particular inconspicuously. It should be indifferent to earthquake, fire or flood, and in particular to corrosion. Something like hundred-tonne cargo containers with special multiple walls and requiring special tools and much time to breach, and producing long-range distress signals if moved without approval, should do nicely. They even might be powered by waste heat from their own contents. Compared to alternatives such as vitrification (not to mention lifting into space) such storage would be dirt cheap and it all could be used up long before all the important half-lives had expired.
So who needs space launching or deep burial or indeed, long term storage at all? A few centuries should be plenty. Anything likely to survive after that, we could cheerfully burn down to inactivity in a high neutron flux unit.

This looks like inventing a bicycle to me. Why bother, when French have it nailed already?

Store spent fuel for 5-100 years (short periods let you recover more Pu; longer periods are more economic).
Then reprocess it. Save reprocessed uranium for use when prices of Uranium go up. Use recovered Pu to manufacture MOX fuel.
Vitrify fission products and transuranics.

This is being done today, every day, in La Hague facility in France. French will even build you a copy for something like $5bn if you ask them.

The only thing French don't do (yet), is geological burial of vitrified waste.

 

[Jon Richfield]

This looks like inventing a bicycle to me. Why bother, when French have it nailed already?

Store spent fuel for 5-100 years (short periods let you recover more Pu; longer periods are more economic).
Then reprocess it. Save reprocessed uranium for use when prices of Uranium go up. Use recovered Pu to manufacture MOX fuel.
Vitrify fission products and transuranics.

This is being done today, every day, in La Hague facility in France. French will even build you a copy for something like $5bn if you ask them.

The only thing French don't do (yet), is geological burial of vitrified waste.

I am glad that someone has had enough sense to steal my idea, even if it was a Frenchman ( :D ) The only thing that puzzles me is why they should want to vitrify anything such as transuranics.

My elaborations about containers etc are just to anticipate possible objections to deal with terrorism etc.
And incidentally, presumably like the French, I reckon that to reprocess fuel before you have a use for the products is crazy. It just lands you with a bigger storage bill for process waste plus an increased load of impurities in your Pu from decay products.

Hooray for French logic and practicality, say I!

 

[jim hardy]

I am glad that someone has had enough sense to steal my idea, even if it was a Frenchman ( :D ) The only thing that puzzles me is why they should want to vitrify anything such as transuranics.

Once upon a vacation i was chatting with a fellow at the motel pool while our kids were swimming.
He was on his way to the resort a block from where I lived in Key Largo.
Small world , he worked for a fuel reprocessing plant in England.
I mentioned i worked at the nuke plant near where he was going and would love to send him home with twenty years worth of spent fuel.
He said he'd love to have it.

US is delinquent in handling the stuff.

You have a Westinghouse-like PWR if I'm not mistaken. (Koeberg site?) I've communicated with a nice lady engineer responsible for its control rod drives through the user's group.

Small world indeed.

 

[nikkkom]

I am glad that someone has had enough sense to steal my idea, even if it was a Frenchman ( :D ) The only thing that puzzles me is why they should want to vitrify anything such as transuranics

Cost. Separating transuranics from fission products requires further processing steps.

Each additional step costs a lot when you work with very, very radioactive materials: it must be done in airtight building, all gaseous emissions and liquid effluents require elaborate filtering, all vessels and piping need to be very durable (since repairs are extremely costly, if practical at all), and all of this stuff requires heavy shielding.

 

[nikkkom]

My elaborations about containers etc are just to anticipate possible objections to deal with terrorism etc.

The final product at La Hague, a steel canister with vitrified waste, emits 1.5 million rem/h of gamma on contact. I dare any terrorists to try stealing THAT.

 

[Jon Richfield]

Pardon my cackling Jim; concerning your "US is delinquent in handling the stuff ", I was just reflecting on how miserably without perspective the views of outsiders are concerning almost any speciality. Imagine the reactions of anti-nuke activists who knew of such conversations...
The US is not alone in its delinquency of course; virtuously anti-nuke activists are instant experts with unbounded faith in their knowledge and understanding. Eg did you know that one of the differences between non-breeder and breeder reactors is that the latter permit a reaction time of at most two MICROseconds to prevent a nuclear explosion? No? Nor did I. We have a lot to learn. Unlike my passionate source.
Not that nuclear engineering is alone in this of course; get to trading war stories with other engineers, say process or chemical engineers trying to deal with safety inspectors who don't understand simple chemistry but quote standards that mention iron as a fire hazard, and accordingly want to see the precautions against fire in stacks of sheet steel. Or want to see the safety practices for dealing with cylinders of compressed N2, uncomprehendingly walking past cylinders of compressed H2 on the way there...
I also remember how miserably ignorant many specialists are about fields quite close to their own; I have met practising engineers who patently misunderstood the concept of nuclear shielding, being under the impression that it was like mechanical shielding: put up a metal plate and either the bullet gets through a thin sheet, or it fails to get through a thick sheet. That sort of thing. And of course I am not immune -- that is why I hang out in places like this where there are folks to help.
Besides, not being an engineer, I safely can claim to know everything. :D

You are correct about Koeberg. I live almost in sight of it (about 60 km away). It has been chugging away since 1984 with comparatively minor incidents, not counting a non-nuclear sabotage incident in the eighties if I remember correctly. However, lately there have been some worrying incidents that to me suggest incompetence and smugness; I am increasingly inclined to share some of nikkkom's concerns. :(

Regrettably I don't know any of their staff. I generally like female engineers in any field -- they tend to be girls with sense and competence.

But I am not sure whether the VVVR approach is any better. And if SA were to commit to Russian built and Russian plants in this country, our politicians would have sold us down the river to dependence on a power that could hold the country to ransom for price and obedience for the foreseeable future,and all for the cash in their own pockets. And IMO, that was the GOOD news.

 

[nikkkom]

Eg did you know that one of the differences between non-breeder and breeder reactors is that the latter permit a reaction time of at most two MICROseconds to prevent a nuclear explosion? No? Nor did I.

(1) You are confusing breeders with fast neutron reactors. Most breeders are fast reactors, but some are not.

(2) Fast reactors won't explode as a nuke even if they suffer power excursion. At worst, they can get their core melt. First, they are designed that way, and second, you can't get a sizable nuclear explosion by merely pushing uranium or plutonium chunks together, no matter how big are they - you need to make them collide or compress at significant velocities, hundreds of meter per second - otherwise, the energy release is "small" and the material "only" melts, doesn't reach millions of degrees.

 

[jim hardy]

We have a lot to learn.

Eric Hoffer said, succinctly:

"I am no longer young enough to know everything."

I took only one course in Reactor Physics
and it did no go at all into fast reactors.
I know just enough to appreciate the abysmal depth of my ignorance.

Anything worth doing should be done well. Particularly anything involving large amounts of energy.
A Windows crash deserves an ounce of prevention, a reactor excursion warrants tons.
The problems with nuclear are societal not scientific ones. Complacency, hubris, ambition, fear and the like.

And that's my opinion.

Do current design Russian reactors still have a large positive moderator void coefficient?
Chernobyl's was +$4(4X enough for prompt criticality). I am glad the one in Cuba never got finished for i don't think something like that should be built in the first place let alone turned over to civilians.

old jim

 

[Astronuc]

Do current design Russian reactors still have a large positive moderator void coefficient?

The VVER is the current commercial design being supplied by Russia, with the VVER-1000 and derivatives being the current models. The VVER-1000 is more like western PWRs, except is uses a triangular/hexagonal lattice. It uses control rods that drop in from the top, unlike the VVER-440 which used control assemblies.

The RBMK is a different animal and that design is more or less obsolete.