A new nuclear power device

[Aero]

To the extent that we all have an interest in focused discussions, we're all thread herders. The community only does as well as it's individual members require us each to do.

Let me put it this way... I would still like to hear more on the sorts of reactors that folks were discussing above. Are these really potentially practical designs, or still very theoretical?

Mike

Me too.

[Mike Holmes]

Once we overcome the fear of the word "nuclear" (let alone some ability to pronounce it right!) the hybrid schemes will have a much better potential.

Is that because they need to be implemented on an economy of scale to be efficient? Or...

Mike

[KitemanSA]

"Potentially practical" is an interesting phrase.
The main problem is reprocessing.

Which is exactly why I an so interested in ADS (or Fusor) driven Thorium fueled molten salt reactors. (TMSR) Their benefits include but are not limited to:

1. They need only minimal chemical reprocessing which results in only fission products, not fissile material;
2. The only “waste" is said fission products, not actinides, so the time required for storage is MUCH less (~300 years vice 200 millennia);
3. The fuel is much more abundant, it uses 100% of the Thorium rather than 5% of the less common Uranium;
4. They run at much higher temperatures than PWRs, thus are much more efficient (~45% vice ~25%);
5. They are inherently safe. A “meltdown” simply removes a plug that is necessary to keep the material within the moderating graphite core. If the plug melts, the molten salt drains into a number of catch-bins and stops reacting.
6. The primary loop runs at atmospheric pressure, so there is no expensive high pressure core, allowing much less expensive designs;
7. The units seem to be effective in a wide range of sizes, but might be efficiently mass produced in the ~50MW range permitting high power installations to be brought on-line a bit at a time

Please note that without the ADS/Fusor boost, a TMSR would require other reprocessing which would include the first step of parging out the U233, which can be used poorly. That is why I am set first on BFR, then on TMSRs.

[Jboily]

Do a web search on "hybrid nuclear reactor". Here's an example:
The Fusion-Fission Hybrid Reactor for Energy Production: A Practical Path to Fusion Application

It's a great idea. I don't think it is economical, otherwise somebody would be doing it.

Yes I too have heard of this idea and wonder where its economic niche is The reactor itself is bound to be more expensive that a PWR. The and waste would just as expensive to store away safely.

The one potential advantage I thought a sub critical fusion fission hybrid might have over a run-of-the-mill fission reactor would be the ability to ramp up and down energy production much faster than a PWR, correct me if I'm wrong but I believe for some reason PWR aren't good at ramping power production up and down rapidly, making them only good for baseload.

The confinement time in a fusion-fission-hybrid grade plasma is about 1 or two seconds so it seems reasionable that power output could be made to fluctuate on that timescale, and ofcourse a fusion reaction is controled magnetically which is less cumbersome than lifting and lowering control rods.

I wonder whether a fusion fission hybrid might take the role of the nuclear version of a gas fired power station ramping up and down production with demand.

I do recall we were working on a breader fusion reactor concept like this in on of my last position (about 15 years ago). I do not have much detail however, since I was not directly involved in this particular design of this ITER version. I was just involved in the design of the material testing apparatus for this concept.

I think the main idea is to produce the Tritium required for a commercial reactor, since there are not enough Tritium around. Having nuclear fission component in a fusion reactor seemed to me at the time to negate the advantages that a fusion reactor would have, that is a reduced amount of nuclear waste.

[djolds1]

This is a rather new idea, and those who do not fully understand it please ask me your questions. My scientific itch gets the better of me sometimes.

The theory is that nuclear fission and fusion can be used to help each other, especially in the case of a standard fusor.

I looked how the fusion bomb worked and in reality it uses mostly fission, but how much of the uranium is “burned” in a fusion bomb is much higher than in a standard nuclear weapon.

The reason: the neutrons from the fusing tritium and deuterium causes the many more of the uranium atoms to fission in a nuclear bomb

The application: instead of just using deuterium in the fusor, add uranium ions, and there is plenty of ways to do this, the uranium ions will move towards the center with the deuterium.

Dr. Friedwardt Winterberg has published multiple papers on similar fission-fusion hybrid systems.

The scary thing is that they all look like subscale nuclear bombs, are powered in ways similar to those that gave the Nonproliferation people cold sweats, and could possibly be used as very small & easy to build primaries in Teller-Ulam style thermonuclear bombs.

Duane

[jmc]

To the extent that we all have an interest in focused discussions, we're all thread herders. The community only does as well as it's individual members require us each to do.

Let me put it this way... I would still like to hear more on the sorts of reactors that folks were discussing above. Are these really potentially practical designs, or still very theoretical?

Mike

Its very simple, you use a fusion reaction (or accelerator spallation) as your neutron source and then use the neutrons from that source to create energy in a subcritical fission reactor (a reactor where less that one neutron per fission event on average causes further fission). The full working system containing both neutron source and blanket is largely theoretical. But a neutron source of sufficient intensity to obtain net energy from a fusion fission hybrid already exists. JET has obtained Q of about 0.65 for about 10 seconds. A basic (where only fusion neutron cause fission and fission neutrons wscape) fissionable blanket amplyfies the energy output by about 30 0.65 * 30 = 19.5 that's enought to create net energy in a practical sense, ofcourse there's still the issue of extending pulses beyond 10 seconds but that mainly a matter of technological development.

[jmc]

MSimon,

I get your point about bloody minded people, actually a fusion fission hybrid could be used to breed plutonium at a much faster rate that a typical breeder reactor. Absorbtion cross-sections of U-238 for 14MeV neutrons are MUCH higher than even "fast" 2MeV neutrons which fast breeders use.

However if we really want to get into the more extreme strand of the non-proliferation mindset. Where we don't only consider a device's proliferation capacity but also the proliferation capacity of all concievable design modifications of said device, then we may aswell give up on all forms of nuclear power right now.

Even aneutronic fusion isn't safe, at the core of sustaining any nuclear fusion reaction is the lawson triple product, any reactor or plasma that could fuse p-B would also be capable of fusing DT, (albeit which some modification in the materials to deal with the neutrons) any device that can fuse DT can produce intense 14MeV neutrons, any device that can produce 14MeV neutrons at high intensities can be used to breed Plutonium.

Can we really say that a molten salt reactor with molten U238 inside of Thorium couldn't be used to make plutonum? As far as I was aware it can burns uranium and plutonium aswell.

If you don't like having devices that can be modified to produce nuclear bombs you may aswell just give up on all forms of nuclear power and put a couple of solar panels up on your house.


At the end of the day though, terrorist don't have the capital to buy a nuclear plant let alone buy one that doesn't produce plutonium and then modify it to do so.

I think the 'rogue state' argument isn't a good one either. Any state can build a nuclear bomb if it is focused on investing a sufficient quantity of resources into doing so. The knowledge is already there, and even if the technology cannot be purchased it can be developed from the ground up. The reason most states don't do this is fear of the political and conomic consequences.

You don't build a wall or fence around your property so that it is impossible for someone to break in, you build it so that it is detectable when they do. Provided the IAEA keeps tabs on the worlds reactors any attempts to modify them will stick out and alert the world.

We could give up on nuclear power but if we do we throw out the possibility of cheap interplanetary travel ( Nuclear fuel is just about the densest way to store energy ) and energy generation that doesn't require a significant fraction of the earth's surface to support us.

[MSimon]

I just think it is something you have to be mindful of.

Reprocessing is the hard trick. Lots of dangerous radioactives to deal with.

In any case the objections will come up. We had better be ready with answers.

All the points you have brought up were brought up in the previous discussion of the issue.

What a D-D BFR buys you is that you do not have as much capital invested as you would with a nuke and you can be some what sloppier in terms of getting the material you want to breed closer to the neutron source.

==

It is interesting that we have been here long enough that topics are starting to get recycled.

[David_Jay]

It is interesting that we have been here long enough that topics are starting to get recycled.

Welcome to the web! It truly IS systemic.

One anecdote: I have an interest old Case garden tractors. They are unusual in that they use motor oil as the fluid in their hydraulic system. There is a Yahoo group where we chat about them. Some newbie shows up on the forum and asks: "What kind of hydraulic fluid should I put in my tractor?". We say "DONT use hydraulic fluid, go read the FAQs". Within a week or two the process repeats itself.

[MSimon]

It is interesting that we have been here long enough that topics are starting to get recycled.

Welcome to the web! It truly IS systemic.

One anecdote: I have an interest old Case garden tractors. They are unusual in that they use motor oil as the fluid in their hydraulic system. There is a Yahoo group where we chat about them. Some newbie shows up on the forum and asks: "What kind of hydraulic fluid should I put in my tractor?". We say "DONT use hydraulic fluid, go read the FAQs". Within a week or two the process repeats itself.

I had a car ('47 Dodge I believe) that used motor oil in its automatic transmission.

[Axil]

MSimon,

I get your point about bloody minded people, actually a fusion fission hybrid could be used to breed plutonium at a much faster rate that a typical breeder reactor. Absorbtion cross-sections of U-238 for 14MeV neutrons are MUCH higher than even "fast" 2MeV neutrons which fast breeders use.

However if we really want to get into the more extreme strand of the non-proliferation mindset. Where we don't only consider a device's proliferation capacity but also the proliferation capacity of all concievable design modifications of said device, then we may aswell give up on all forms of nuclear power right now.

Even aneutronic fusion isn't safe, at the core of sustaining any nuclear fusion reaction is the lawson triple product, any reactor or plasma that could fuse p-B would also be capable of fusing DT, (albeit which some modification in the materials to deal with the neutrons) any device that can fuse DT can produce intense 14MeV neutrons, any device that can produce 14MeV neutrons at high intensities can be used to breed Plutonium.

Can we really say that a molten salt reactor with molten U238 inside of Thorium couldn't be used to make plutonum? As far as I was aware it can burns uranium and plutonium aswell.

If you don't like having devices that can be modified to produce nuclear bombs you may aswell just give up on all forms of nuclear power and put a couple of solar panels up on your house.


At the end of the day though, terrorist don't have the capital to buy a nuclear plant let alone buy one that doesn't produce plutonium and then modify it to do so.

I think the 'rogue state' argument isn't a good one either. Any state can build a nuclear bomb if it is focused on investing a sufficient quantity of resources into doing so. The knowledge is already there, and even if the technology cannot be purchased it can be developed from the ground up. The reason most states don't do this is fear of the political and conomic consequences.

You don't build a wall or fence around your property so that it is impossible for someone to break in, you build it so that it is detectable when they do. Provided the IAEA keeps tabs on the worlds reactors any attempts to modify them will stick out and alert the world.

We could give up on nuclear power but if we do we throw out the possibility of cheap interplanetary travel ( Nuclear fuel is just about the densest way to store energy ) and energy generation that doesn't require a significant fraction of the earth's surface to support us.

The key concept in non proliferation is isotopic denaturing. There is an intense gamma emitting isotope or a nuclear poison that is not easily separated from the bomb material. For U-233 it is U-232 and its decay chain, for PU-239 it is PU-238, for U-235 it is U-238, and so on.

The IAEA rules that support isotopic denaturing are that the enrichment of U235 cannot exceed 20%. For U233 it is 12%.

Whenever U233 is removed from a reactor, you also remove the denaturant U232 that makes weapons production hard.

The enabling technology that makes weapons production possible is isotopic enrichment