Paging Birdman on nuclear reactor designs

[MillCreek]

In the October Surprise thread, I read with interest your experience in the nuclear industry.  So as an expert in this arena, what would you say is the optimum design of nuclear reactor for electric power generation with a minimal amount of waste products or diversion to a nuclear weapons program?  Either something currently built or on the drawing boards or design stage? 

I have read a few interesting things about the pebble bed reactors and what not, but I am but a simple former analytical chemist, and not well-versed in nuclear issues.  If there are any links or articles that you think are on point, I would enjoy reading them.

[Devonai]

I say we just stack a bunch of uranium and graphite blocks together in an old racquetball court and see what happens.

[zxcvbob]

I'll vote for liquid thorium (fluoride) reactors.  The fuel is cheaper too.

[kgbsquirrel]

Just stumbled across something. I was under the impression that Pu238 was really expensive to make due to it being a small fraction of the material produced in a breeder reactor, and thus would never be within my reach for building a small RTG. According to this, you can breed Pu238 in a Thorium fuel cycle reactor...

http://www.thoriumenergyalliance.com/downloads/plutonium-238.pdf

Hey Birdman, does this look correct to you?

[birdman]

I'll vote for liquid thorium (fluoride) reactors.  The fuel is cheaper too.

Molten salt reactors have a whole slew of problems...so let's say they are second best

[birdman]

Just stumbled across something. I was under the impression that Pu238 was really expensive to make due to it being a small fraction of the material produced in a breeder reactor, and thus would never be within my reach for building a small RTG. According to this, you can breed Pu238 in a Thorium fuel cycle reactor...

http://www.thoriumenergyalliance.com/downloads/plutonium-238.pdf

Hey Birdman, does this look correct to you?

Yes. 

[birdman]

My personal favorite is high temperature pebble-bed reactors, (if you know my real name, google it and you will see why).  They can be built as breeders or conventional, built youse any enrichment of fuel, run on normal thorium, or MOX fuel, and have the most important thing--a negative temperature coefficient of reactivity.

Basically, a properly designed HTGR cannot melt-down, as the reactivity decreases as the temperature increases--so it can be easily and reliably designed to shutdown due to the laws of physics at a temperature BELOW the temperature at which the fuel fails and releases material.  In effect, in operation, you have to keep it cool (by extracting heat and making power) to PREVENT it from shutting down when you don't want it to.

Google "PBMR" for the south African big one (I have worked VERY closely with all of those guys), MIT "modular pebble bed reactor" for work here, or find the jaanese or Chinese programs.

They also tend to be extremely efficient relative to other systems (Carnot and his damn laws help when the reactor is humming at 850degC) and can be built small (10-20MWelectric) or large (100-200MWe) and be built quickly and economically.

I've designed two major ones recently, where the only thing that presented funding was the 2008 financial crisis taking down our investors and political BS pushing the timelines out.

Sad to say, the first thing I have to tell people looking to invest or design reactors is "it's highly profitable, just not in this country"

[Stetson]

I learn the coolest things here.  Thank you for the explanation birdman.  I read it to my mom and even she understood it.

[Perd Hapley]

When I talk about this with my Dad, his concern is always that nuclear waste is horrible-awful-terrible and lasts basically forever. How is that stuff actually being stored, and how dangerous is it?

As a young lad, in the early '80s, my parents took me along to a "No Nukes" rally. It's not really a major issue for them, but they (or at least Dad) have been consistently opposed to it.

[RoadKingLarry]

Pay no attention to those digging sounds coming from under your house.

[birdman]

When I talk about this with my Dad, his concern is always that nuclear waste is horrible-awful-terrible and lasts basically forever. How is that stuff actually being stored, and how dangerous is it?

As a young lad, in the early '80s, my parents took me along to a "No Nukes" rally. It's not really a major issue for them, but they (or at least Dad) have been consistently opposed to it.

If you reprocess, the following things happen:
1. There is 30-100x LESS waste
2. You need 30-100x less uranium or thorium (in a normal reactor, for every 3kg of U-235 put in, there is 1-2kg of U-235 and 0.5-1kg of plutonium left at the end of the cycle..,which we store as WASTE!

We don't reprocess, thus we have a waste problem.

France has nearly the same number of reactors, and ALL their waste fits in a relatively small, and heavily shielded facility.

We (carter) made the decision to "set an example for the world and curb nuclear proliferation" by not reprocessing (since reprocessing is how you get plutonium...bear in mind, normal nuclear reactor power plant fuel cycles can't make bomb grade plutonium, only reactor grade mixed oxide fuel.

Since then, everyone reprocesses but us, no one else has a waste problem, and at least 4 more countries joined the nuclear club...smart guy, that mr. Peanut.

Also, you can use a concept like LIFE (laser initiated fission/fusion energy) or accelerator transmutation of waste (ATW) to take what waste you do have left and treat it.

Basically, the fission products come in three groups
Short and hot (10s-100s of year half life)
Annoying and hot (1000s-10000s year half life)
Long and cold (million year half lives)

Remember, the shorter the half life, the more radioactive a given amount of stuff is.

Category 1 (short and hot) is no big deal, you vitrify it, and store it in a building for 100-200yrs and it's gone.
Category 3 (long and cold) is no big deal, you dilute it sufficiently with dirt and bury it back in the ground...it's about as radioactive as uranium ore.

Category 2 is the annoying stuff, but it's a small quantity relative to the others.  That stuff you blast with a neutron source and turn it into category 1 or 2.  This takes power (about 10-20% of what the original reactor produced, or basically you need 11 where you used to need 10), but blammo, no waste problem.

With the above strategy, we have enough uranium ALREADY MINED to last hundreds of years, and no waste problem.

[zxcvbob]

We (carter) made the decision to "set an example for the world and curb nuclear proliferation" by not reprocessing (since reprocessing is how you get plutonium...bear in mind, normal nuclear reactor power plant fuel cycles can't make bomb grade plutonium, only reactor grade mixed oxide fuel.

Since then, everyone reprocesses but us, no one else has a waste problem, and at least 4 more countries joined the nuclear club...smart guy, that mr. Peanut.

Mr. Peanut was right on pretty much every point in his famous "Moral Equivalent of War" (M.E.O.W.) speech.  (Too bad Reagan dismantled the whole energy policy but didn't disband the Department of Energy.)  I wonder how Carter squared this particular wastefulness (of plutonium 239) with his philosophy of conservation and good stewardship of natural resources?

[birdman]

Mr. Peanut was right on pretty much every point in his famous "Moral Equivalent of War" (M.E.O.W.) speech.  (Too bad Reagan dismantled the whole energy policy but didn't disband the Department of Energy.)  I wonder how Carter squared this particular wastefulness (of plutonium 239) with his philosophy of conservation and good stewardship of natural resources?

No clue.  Not only that, he was a navy nuc.

Are you saying you agree with what he said?  Other than the potential socio-economic issues of not having a good energy policy, much of his premature push toward "renewables" was flawed.

[kgbsquirrel]

Mr. Peanut was right on pretty much every point in his famous "Moral Equivalent of War" (M.E.O.W.) speech.  (Too bad Reagan dismantled the whole energy policy but didn't disband the Department of Energy.)  I wonder how Carter squared this particular wastefulness (of plutonium 239) with his philosophy of conservation and good stewardship of natural resources?

"Its for the children"?

[RoadKingLarry]

No clue.  Not only that, he was a navy nuc.

Are you saying you agree with what he said?  Other than the potential socio-economic issues of not having a good energy policy, much of his premature push toward "renewables" was flawed.

He was a Rickover nuke. Other than being pretty sharp in a "do it my way or I'll make your life a living hell if I let you have one" kind of way, Rickover was nucking futz. His primary criteria for nuke officer selection seemed to be how well the candidates could kiss his ass. Some were able to fake it but a good many didn't have to.

[birdman]

"Its for the children"?

And children LLLLLOOOOOOVVVVVVEEEE plutonium.

[zxcvbob]

If we had continued on a path of energy conservation and a shift away from petroleum, we could have crippled the Middle East during the oil glut of the mid-1980's.  (probably crippled Houston and New Orleans too) and we might not be fighting the Islamic extremists now -- they would no longer be relevant.  We had them on the run, and instead we went back to big inefficient cars for the next 10 years.

There was a book out in the 1970's about alternative energy sources.  I can't remember the title well enough to find it on google; I'll have to search upstairs and see if I can find my old copy.  One example from it that stuck in my mind was to build a hydroelectric dam across the mouth of a long narrow bay [unfortunately it was in the Middle East] and wait about a year for evaporation to drop the water level enough to begin electricity generation.  The cool part was the water in the bay would get more and more concentrated until the salts would start precipitating out and could be dredged out to harvest the metals.  The gold that could be mined would be worth more than the electricity.  They had the technology to do all that 40 years ago.

We should have taken on a national challenge to see how far we could drive down the price of oil ($2 a barrel?) just to screw with the Arabs.

ETA: I remembered the author's first name (thought it was his last name), and that was enough to track it down:  Energy for Survival: The Alternative to Extinction by Wilson Clark.

[zxcvbob]

And children LLLLLOOOOOOVVVVVVEEEE plutonium.

If you burn uranium in a nuclear reactor, you get plutonium whether you want it or not.  (oversimplification, I know)  Why not recycle it? 

[kgbsquirrel]

I wish I could afford a small modular pebble bed reactor. Unlimited electricity to power my nefarious plans minor and benign hobbies and sell back a good bit to the local power grid. Hopefully it would be enough to cover the payments on the reactor.


Since everywhere seems to have a bunch of NIMBY morons, I wonder if it would be practicable to build a super giant NPP complex out in the middle of fracking no-where, say the old nuclear test range in Nevada, and then just pipe the power to the rest of the nation?

[French G.]

How could it be less practical than kissing a camel herder's butt for decades and then carting his oil halfway around the world one small load at a time? Of course even in the middle of nowhere idiots do the nimby, see yucca mountain, blocked for years. Virginia has a chance to become filthy rich mining uranium and every damn hippie is trying to stop it.

[AJ Dual]

I wish I could afford a small modular pebble bed reactor. Unlimited electricity to power my nefarious plans minor and benign hobbies and sell back a good bit to the local power grid. Hopefully it would be enough to cover the payments on the reactor.


Since everywhere seems to have a bunch of NIMBY morons, I wonder if it would be practicable to build a super giant NPP complex out in the middle of fracking no-where, say the old nuclear test range in Nevada, and then just pipe the power to the rest of the nation?

Probably not quite profitable due to line losses, unless someone comes up with a room temp superconductor that doesn't require high amounts of rare earths. And of course, even a room temp. superconductor that uses the most expensive elements possible hasn't been found either.

So there's generally an economic sweet spot between plant placement to users, and transmission distance.

[kgbsquirrel]

Another question for the Birdman: Can our huge pile of DU be used in a heavy water reactor, or is that sort of thing only viable with the natural isotope composition (.7% U235)?

I seem to recall seeing somewhere that the U.S. is sitting on some 480,000 tons of DU.

[zxcvbob]

Another question for the Birdman: Can our huge pile of DU be used in a heavy water reactor, or is that sort of thing only viable with the natural isotope composition (.7% U235)?

I seem to recall seeing somewhere that the U.S. is sitting on some 480,000 tons of DU.

U238 (DU) should work just fine as the fertile material in a breeder reactor.  I don't think it will sustain a reaction without a neutron source to convert it to plutonium 239.

[birdman]

U238 (DU) should work just fine as the fertile material in a breeder reactor.  I don't think it will sustain a reaction without a neutron source to convert it to plutonium 239.

Correct. U-238 is bred with neutron flux from a reactor to make Pu-239 (and 240,241 if you leave it in too long...the presence of those it what makes the difference between reactor and bomb grade Pu).

Let's put it this way, at 30-40,000 MW-days/ton metal burnup, our 450,000 tons of DU in breeder reactors would be enough to produce ALL of the US energy needs for 20-25 YEARS (and that's replacing ALL fossils fuels including oil/gas with synthetic hydrocarbons).  with ATW, there would be virtually no waste issues.

The big advantage of breeders is the saying we have in the industry:

You have a breeder reactor, a ton of DU or thorioum, and a ton of U-235 or Plotonium...what do you have after the end of the year?
A breeder reactor and TWO tons of U-233 or Plutonium (for a thorium or MOX cycle respectively)

[zxcvbob]

Correct. U-238 is bred with neutron flux from a reactor to make Pu-239 (and 240,241 if you leave it in too long...the presence of those it what makes the difference between reactor and bomb grade Pu).

Let's put it this way, at 30-40,000 MW-days/ton metal burnup, our 450,000 tons of DU in breeder reactors would be enough to produce ALL of the US energy needs for 20-25 YEARS (and that's replacing ALL fossils fuels including oil/gas with synthetic hydrocarbons).  with ATW, there would be virtually no waste issues.

The big advantage of breeders is the saying we have in the industry:

You have a breeder reactor, a ton of DU or thorioum, and a ton of U-235 or Plotonium...what do you have after the end of the year?
A breeder reactor and TWO tons of U-233 or Plutonium (for a thorium or MOX cycle respectively)

What's ATW?

On a mostly-unrelated topic, how does plutonium even have a critical mass?  All its isotopes are just alpha-emitters.  Spontaneous fission?  Or maybe one of the isotopes decays into something throws off a neutron or three when IT decays...