U232 can be a bridge to aneutronic fusion power

Discuss the technical details of an "open source" community-driven design of a polywell reactor.

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Axil
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U232 can be a bridge to aneutronic fusion power

Post by Axil »

U232 can be a bridge to aneutronic fusion power.


I propose an aneutronic fusion reaction (Q>1) that uses D-T fusion to generate neutrons for the irradiation of Th230 so that U232 is produced.

230Th(n,y) -> 231Th(-B) -> 231Pa(n,y) -> 232Pa(-B) -> 232U

U232 is the most radio productive among all the uranium isotopes. When a U232 alpha emission commences, it is followed in short order by 5 other alpha emissions from its daughter products. When coupled with “High-Powered Radiovoltaics” and “direct heat to electric conversion” a high powered nuclear power source is possible.

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A fusion neutron source need not be highly available; U232 will save the power and dispense in uninterrupted fashion.


Such a power source would act like a battery and have a useful lifespan of over a hundred years, and when new such a battery would increase its power until 10.17 years of age and level out retaining power production for 100 or more years.


Since 80% of the energy in D-T fusion results in neutron production, U232 can be used as a converter to turn that neutron energy into alpha and gamma radiation.


This uranium isotope can then produce electric power directly using aneutronic nuclear reactions from its alpha and gamma radiation production at high efficiency without the need for turboelectric generators.


Large turbine and generator equipment is sufficiently expensive so that about 80% of the capital cost of a typical fossil-fuel or nuclear electric power generating station is in this thermal conversion equipment.


Using U232, a small fusion source of D-T neutrons can thus be transformed into a small, highly efficient, and compact generator of electric power with few if any moving parts.


Many proposed direct conversion techniques are based on mature technology derived from other fields, such as microwave technology, and some involve equipment that is more compact and potentially cheaper than that involved in conventional thermal production of electricity.

Direct conversion techniques can either be inductive, based on changes in magnetic fields, or electrostatic, based on making charged particles working against an electric field.

A sizable fraction of the energy released by U232 would not produce neutrons but would instead be radiated as alpha and as gamma (G-rays). This energy would be converted directly to electricity.

Because of the photoelectric effect, G-rays passing through an array of conducting foils would transfer some of their energy to electrons, which can then be captured electrostatically. Since G-rays can go through far greater thickness of material than electrons can, many hundreds or even thousands of layers would be needed to absorb most of the G-rays.


Alpha radiation can be directly converted to electric power by similar electrostatic and inductive techniques.

An efferent design would convert all the G-rays and alpha radiation to power and contain all the gamma radiation within the reactor itself.

Furthermore, such a design would be almost proliferation proof.

Lithium 6 would also be irradiated by neutrons to supply tritium for self sustaining D-T fusion reactor operation.

The heat output of the reactor would use direct heat to electric conversion.
Last edited by Axil on Wed Feb 24, 2010 7:25 am, edited 1 time in total.

KitemanSA
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Post by KitemanSA »

How do you convert tha gamma? How do you prevent it from fowling up the rest of your system?

Most folk talk about U232 in the Thorium cycle as a BARRIER to any other use besides fission power plants due to that gamma radiation.

Axil
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Post by Axil »

The advocates of hydrogen-boron (pB11) fusion on this site will be greatly disappointed in your skepticism about direct conversion of high energy radiation to electric power, also Eric Lerner.

You don’t believe that Eric Lerner’s patented direct conversion of x-ray radiation to electric power will work?

Eric Lerner invention must work. He must have tested it using x-rays. He is staking all his work on it.

This goes for all the other hydrogen-boron (pB11) fusion approaches.

Notwithstanding, direct high energy radiation conversion is inefficient but is possible through interaction of the gamma rays with an appropriate material that will suffer a loss of electrons through the gamma interactions with it. The electrons can be collected in an electric field and represent a current flow. In point of fact, gamma radiation detectors operate on this principle. Various materials have been used in this regard. Various semiconductors undergo electron ejection in response to ionizing radiation and have had many applications in radiation detection and measurement. Photovoltaic cells, commonly used in the visible and ultraviolet portion of the electromagnetic spectrum, can also convert gamma ray energy to electron current, but the process is very inefficient in terms of the fraction of gamma energy that ends up as collectible electrical charge.

At the end of the U232 decay chain, as thallium 208 with a half-life of 3.07 minutes transmutes into lead 208, thallium produces a 2.6 MeV G-ray as it emits a high energy electron.

This reaction carries a very small percentage of the U232 total decay energy. This 2.6 MeV G-ray gamma ray can be shielded using lead or tungsten or concrete. Upon absorption, it will produce heat in those shields.

On the plus side, this 2.6 MeV G-ray is a potent shield again proliferation. The reactor engineering must be carefully done to maximize proliferation protection and minimize operational exposure, but it can be done.

U232 emits most of its energy as alpha and beta radiation which is ideal for direct energy conversion.

KitemanSA
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Post by KitemanSA »

Axil wrote:The advocates of hydrogen-boron (pB11) fusion on this site will be greatly disappointed in your skepticism about direct conversion of high energy radiation to electric power, also Eric Lerner.
As far as I know, most folks on this site anticipate that the brem will be minimized, not converted. It is the alpha direct conversion that is the prime conversion path. And X-rays are not gamma rays so I don't know how well Lerner's process will work with them. Heck, I don't know how well it works with X-rays! Any data?

Axil
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Post by Axil »

The decay chain from Uranium-232 produces around 43 MeV/atom. This compares well against a standard RTG at 5 MeV/atom and even fission at 180 MeV/atom.

The total activity of a sample of U-232 peaks around 10 years after the sample is generated. The peak, however, is wide in that the activity has decreased by less than 10% at 20 years; i.e. the power level is relatively flat between 8 to 25 years. The peak activity is 5.8x10e12 disintegrations/s-g (157 curies/g) at the 10 year mark. This corresponds to 5 W/g of thermal energy. With a 40% conversion efficiency, the electrical power estimated for a U232 platform is 2 W/g U-232.

If the fear of heavy gamma radiation can be overcome, a safe, proliferation proof nuclear battery could be developed supported by a purpose built fusion/fission hybrid infrastructure.

MSimon
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Post by MSimon »

Lots of patented things don't work. Perpetual motion machines have been patented.

Getting a patent is nothing.
Engineering is the art of making what you want from what you can get at a profit.

MSimon
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Post by MSimon »

If the fear of heavy gamma radiation can be overcome, a safe, proliferation proof nuclear battery could be developed supported by a purpose built fusion/fission hybrid infrastructure.
The fear is easy enough to overcome with 10 or 20 ft thick concrete walls. Shipping will be a bitch.
Engineering is the art of making what you want from what you can get at a profit.

Axil
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Post by Axil »

MSimon wrote:
If the fear of heavy gamma radiation can be overcome, a safe, proliferation proof nuclear battery could be developed supported by a purpose built fusion/fission hybrid infrastructure.
The fear is easy enough to overcome with 10 or 20 ft thick concrete walls. Shipping will be a bitch.
It would be terror resistant!


Shipping ... no problem.

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MSimon
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Post by MSimon »

I think if you check you will find that the radioactives in that cask are not 100 curies per gram of high energy gammas.
Engineering is the art of making what you want from what you can get at a profit.

KitemanSA
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Post by KitemanSA »

Just looked more closely at the decay chain. Half life of 1.4E10 YEARS for alpha decay? Just how long should we be willing to wait for this power?

Am I missing something?

blaisepascal
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Post by blaisepascal »

KitemanSA wrote:Just looked more closely at the decay chain. Half life of 1.4E10 YEARS for alpha decay? Just how long should we be willing to wait for this power?

Am I missing something?
Perhaps. The title of this thread is "U232 can be a bridge to aneutronic fusion power". While it's true that nothing in this proposal appears to involve fusion, it does appear that U232 has an alpha-decay route that he is interested in.

Rereading his proposal, I see he wants to breed U232 from Th230 via 2 neutron captures and 2 beta decays -- and he wants to use D-T fusion as a neutron source for this.

OK, I'll bite...

Where's he going to get the Th230? Natural Thorium is at least 99.995% Th232. Th230 is a decay product of U234, which has a much longer half-life than Th230, so very little Th230 is naturally around.

Where's

Axil
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Post by Axil »

Read the chart from the U232 branch not the Th232 branch. We start out with pure u232 not Th232.

Power from alphas will be about 1/6 of the total power from U232 itself. The U232 decay chain provides 5/6 of the total when in equilibrium.

Power will build up over the first year from 1/6 power up to unity equilibrium.

It is important to note that the gamma’s radiation builds up in the same way. This will allow for installation when the gamma load is low. That is during the first year. I would think that the U232 power source can’t be accessed for about 200 years thereafter.
Last edited by Axil on Thu Mar 11, 2010 2:31 am, edited 1 time in total.

Axil
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Post by Axil »

blaisepascal wrote:
KitemanSA wrote:Just looked more closely at the decay chain. Half life of 1.4E10 YEARS for alpha decay? Just how long should we be willing to wait for this power?

Am I missing something?
Perhaps. The title of this thread is "U232 can be a bridge to aneutronic fusion power". While it's true that nothing in this proposal appears to involve fusion, it does appear that U232 has an alpha-decay route that he is interested in.

Rereading his proposal, I see he wants to breed U232 from Th230 via 2 neutron captures and 2 beta decays -- and he wants to use D-T fusion as a neutron source for this.

OK, I'll bite...

Where's he going to get the Th230? Natural Thorium is at least 99.995% Th232. Th230 is a decay product of U234, which has a much longer half-life than Th230, so very little Th230 is naturally around.

Where's

Reference:
6.465 MeV threshold Th232(n, 2n)Pa231
11.610 MeV threshold Th232(n, 3n)Th230

Above 11.610 MeV, the cross section for Th232(n,y)Pa233, Th232(n, 2n)Pa231, and Th232(n, 3n)Th230 are all equal at about 1 barns each.
All things being equal, the amount of Pa231 will be twice that of Pa233.

Ok, let's try some back of envelope numbers on the Pa233/Pa232 issue. Let's say your fusion hybrid is making Pa233/Pa232 with about 1part to 2 parts ratio respectively. That is, if we let a batch of extracted Protactinium sit for a long time we would roughly get uranium in the ratio of 333333:666666 of U233:U232. However, Pa233 has a halflife of 27 days & Pa232 halflife is 1.3 days. Thus, if we wait just 13 days we have waited 10 halflives of Pa233 so that only 1/2^10, or 9.8e-4 (0.098%) Pa-232 remain, while 0.72 (72%) of the Pa233 remain.

333333 parts Pa233 would decay into 333333 * (1 - 0.72) = .28 x 333333 = 93,333 parts U233

666666 parts Pa232 would decay into 666666 * (1 - 9.8E-4) = .999 x 666666 = 665999 parts U232

665999 /(93,333 + 665999) = 665999/765332 = A maximum of 87% pure U232 is possible from of fusion/fission hybrid.

MSimon
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Post by MSimon »

I think there will be a huge market for an electrical generator that can't be moved or repaired for 100 years once it is operational.

And licensing will be a piece of cake. You just build a few thousand of a particular design and operate them for 10 or 20 years to prove their reliability and then go into mass production.
Engineering is the art of making what you want from what you can get at a profit.

Axil
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Post by Axil »

This is a solid state device with high redundancy and no moving parts. You can get high reliability and availability out of that type of approach.
It is a nuclear battery. You don’t repair a battery, you buy a new one.

You don't need to be concerned with proliferation, that might be worth something.

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