Energy From Thorium Discussion Forum

How about a Faraday generator!

When an electrically conductive fluid flows through a tube, in the presence of a significant perpendicular magnetic field, a charge is induced in the field, which can be drawn off as electrical power by placing the electrodes on the sides of the reactor at 90 degree angles to the magnetic field.

There are limitations on the density and type of field used. Usually, the amount of power that can be extracted is proportional to the cross sectional area and the speed of the conductive flow.

But in our case, there should be a substantial current flowing through the liquid metal that is produced by the capacitive extraction of electrostatic charge to the carbon electrodes at the top of the reactor. This vertical current will generate a magnetohydrodynamic (MHD) current into the electrodes on the sides of the reactor vessel.

The lithium coolant is also cooled and slowed by this process and any horizontal vibrations relative to the flow by the fuel pellets will also be damped.

In addition, by pumping the reactor coolant into a MHD generator before a traditional heat exchanger addition efficiency can be realized.


By the way, in the Lftr design, one possible MHD conductive coolant is the molten salt reactor's molten salt, since molten salts are electrically conductive, by pumping the reactor coolant into a MHD generator before a traditional heat exchanger an estimated efficiency of 60 percent can be realized.

A reactor fuel whose ultimate performance is dependent on its ability to separated electric charge to maintain electric polarization requires a careful tradeoff analysis between nuclear performance and capacitive performance.

An optimized design of such a fuel is an exercise in material evaluation and selection from the perspective of both a nuclear and a electric insulation properties.

For example, the dielectric strength of a material is an intrinsic property of the material. It is dependent on the configuration of the material to which the electric field is applied. At breakdown, the electric field frees bound electrons. The more tightly the electrons are bound, the greater is its dielectric strength.

If the applied electric field is sufficiently high, free electrons may become accelerated to velocities that can liberate additional electrons during collisions with neutral atoms or molecules in a process called avalanche breakdown. Breakdown occurs quite abruptly (typically in nanoseconds)., resulting in the formation of an electrically conductive path and a disruptive discharge through the material. For solid materials, a breakdown event severely degrades, or even destroys, its insulating capability.

Factors affecting the dielectric strength of a nuclear capacitor are first, directly proportional to the increase in thickness of the material; and second, inversely proportional with the increase in temperature

Because dielectric materials usually contain minute defects, the practical dielectric strength will be a fraction of the intrinsic dielectric strength seen for ideal, defect free, material. Dielectric films tend to exhibit greater dielectric strength than thicker samples of the same material. For instance, dielectric strength of silicon dioxide films of a few hundred nm to a few micrometers thick is approximately 0.1 MV/m. However very thin layers become partially conductive because of electron tunneling.

To optimize the performance of an insulator, multiple layers of thin dielectric films are used where maximum practical dielectric strength is required, such as high voltage capacitors and pulse transformers.

A optimum isolative structure for high temperature capacitive nuclear fuel is a ultra thin layering of different metal oxides that are relatively insensitive to nuclear degradation.

Many thin layers of alternating materials will provide optimum electric polarization.

Four such materials are candidates as follows:

1. Thorium
2. Titanium
3. Strontium
4. Beryllium

For example, Strontium Titanate is an oxide of strontium and titanium with the chemical formula SrTiO3 and has a very large dielectric constant about10e4 at low temperatures compared to a pure vacuum at 20 and rubber at 3.

Furthermore, in a nuclear environment, impurities in the material will be the rule. Such impurities will erode capacitive capacity.

In addition, formation of a electrically conductive path in the insulator caused by impurities will produce a disruptive discharge through the material resulting in the generation of heat.

This deterioration will not happen all at once but gradually as the capacitive character of the fuel changes over time. Because of the inherent random nature of the materials environment, deterioration in polarization will be a gradual process averaged over an extreme range of particular nano-material environments and over a wide range in timeframes. This deterioration will be countered by the steady removal and subsequent replacement of new fuel pebbles on an ongoing basis.

Even though the hydride in the lithium moderator will provide a failsafe nuclear framework that underpins the mitigation of polarization failure, a potentially rapid heat build up from depolarization should be avoided to support good controllability of the reactor. High polarization potential can and provides a safety margin in control.

From the perspective of operational simplicity, it will be important to keep the electric potential in the reactor within an operational range so that transients from that range are minimized.

Simply put, the higher the average capacitive capacity that can be achieved, the more safety margin from transients that the reactor will manifest and the more performance latitude can be guarantied against the vagaries of randomness.

PS: here is a simulated displacement cascade within gold from a low energy ion impact.

http://www.youtube.com/watch?v=vLGxAC2DxSs

Axil,
These conferences have a lot of proposed methods, but I think this could be a fairly short term development-

http://www.icenes2007.org/icenes_procee ... EACTOR.pdf

Thoughts?

The big knock against nuclear power is it’s up front capital cost. If a game changing way to reduce that cost well below that of fossil fuel power plants (i.e. – “cheaper than coal”), wide spread deployment of nuclear power is inevitable and will doubtless exclude all other power generation technologies especially if the power density is very high and economies of scale can be applied.

The key is to eliminate the production of thermal heat as a method for electric generation. When you eliminate heat, you eliminate 90% of the cost of a nuclear reactor complex. This cost comes from the capital cost of piping, heat exchangers, pumps, turbines and the recurring costs of the associated O&M of those items. Substantial reduction in personnel to take care of these heat application apparatus is also possible.

Correspondingly, the size of a solid state reactor can be reduced very small and this small size factor is very attractive and saves on construction capital.

A reactor without any moving parts is a reactor that can achieve high availability, low operation and maintenance costs, and a long operational life.

Heat production in a traditional reactor limits the materials that can be use in its construction adding to it construction expense.

The research project that you reference: “Pulse Reactor system for Nuclear Pumped Laser using Low Enriched Uranium” is an application of cost reduction through direct nuclear energy conversion to electric power.

It is possible to produce a mid infrared energy source at a precise wavelength that can be directly converter to electric power. A proof of concept demo has shown a conversion efficiency in the narrow infrared laser originated bandwidth range to electric power at 92%.

By the way, it is the nuclear figments from fission that excites the laser gas and produces the laser output.

Here is another link on the subject:

http://www.nr.titech.ac.jp/coe21/eng/ev ... _Obara.pdf

Nuclear-pumped lasers and physical problems in constructing a reactor-laser



Using as fusion source for our neutrons gets around the requirement for criticality.

As far as I can tell, one variant that has not yet been considered is to use a fusion source as the nuclear fragment laser lamp.

I am thinking that a UF6 and/or a ThF4 vapor(1680°C) laser can be pumped using fusion neutrons from a pulsed source like the Helion fusion reactor. This nuclear pumped laser could produce optical power as well as breed U233.

If Deuterium is added, it would be similar to the deuterium fluoride laser: the Tactical High Energy Laser

The Tactical High-Energy Laser, or THEL, is a laser developed for military use, also known as the Nautilus laser system. The mobile version is the Mobile Tactical High-Energy Laser, or MTHEL.


Another possibility is to use a liquid (this is transparent) or solid (if it is transparent?) fluoride/thorium salt doped with lithium as the lasing medium, and a fusion source as the nuclear fragment lamp.

There is a lot to think about in this stuff. More on it later.

Nuclear pumped laser nuclear power conversion is not yet suitable for a direct power conversion reaction because its power conversion efficiency is low. The maximum energy transfer efficiency of the deposition of fission fragments into a planar channel does not exceed 20% when the neutron flux is constant.

This means that 80% of the nuclear energy will produce heat, the reaction characteristic that must be minimized. Heat production is the killer and the deal breaker.

In result, nuclear pumped laser nuclear power conversion is best put aside for now in preference for a more efficient power conversion approach. I still like electrostatic conversion best. Here is why:


Explanation of terms




When an atom fissions, it generally splits into two fragments, a heavy and a light product atom. The heavy fragment typically possesses a kinetic energy approximately 0.5 MeV/amu and the light fragment 1.0MeV/amu, which is a velocity ranging from 3% to 5% of the speed of light. With uranium fission, typically 81% of the energy released is the form of the kinetic energy of the fission fragments, with the remaining 19% released in the form of beta, gamma and neutrons, for a total of 207 MeV per fission. In a conventional nuclear reactor the high kinetic energy of the fission fragments is dissipated by collisions with other atoms to generate heat, which is extracted to produce energy through the Carnot cycle with efficiencies no more than 50%. In the fission fragment reactor, the high-speed fragments are used to produce electrical energy through direct conversion methods. In direct conversion, the kinetic energy of the charged fission fragments is extracted by deceleration in the electrostatic fields of the shell electron cloud around the atoms of a blanket material to directly produce electrical energy through ionization bypassing the Carnot thermodynamic cycle. Thus energy conversion efficiencies achievable with direct conversion methods approach 90%.

There is still a great deal of power that is unutilized in nuclear waste. I propose a way to utilize it.

Today, waste is kept underwater (water is an excellent shield) for a few years until the radiation decays to levels that can be shielded by concrete in large storage casks.

If that alpha radiation power in nuclear waste was converted directly into electricity at 90% efficiency rather that into intense waste heat, a great battery would result.

The Lithium Homogeneous Reactor (LHR) produces nuclear waste in all Z ranges up to neptunium 137. All this waste produces heavy alpha radiation. It might be simple to produce a direct nuclear conversion device using this waste product.

LHR waste is in the form of nano dust whose partial size ranges from 5 Nm maximum and from there descending into varied smaller sizes down into the atomic scale. This waste can be applied in a lamination process to form a Liviu Popa-Simil nuclear battery as follows:

Step 1 - Start out with a disposition of an amorphous layer of pure carbon or diamond 20Nm thick. This comprises a base level substrate and is initially done only once in the Liviu Popa-Simil CIci Direct Energy Conversion Nano scheme.

Layer begins

create a thorium-waste sandwich- steps 2 through 4

Step 2 – next deposit a layer of thorium 5Nm thick; this comprises the high Z conductor layer(C) in the Liviu Popa-Simil CIci Direct Energy Conversion Nano scheme. This anode also carries the positive charge.

Step 3 - deposit a uniform 5Nm thick disposition layer of nuclear waste on the thorium layer.

Step 4 – cover the nuclear waste disposition with another layer of thorium 5Nm thick to encapsulate the nuclear waste.

Step 5 – next, deposit an amorphous layer of pure carbon or diamond 20Nm thick. This completes the high Z isolation layer(I) in the Liviu Popa-Simil CIci Direct Energy Conversion Nano scheme.

Step 6 – cover the carbon layer with a layer of aluminum. This comprises the low Z conductor layer(c) in the Liviu Popa-Simil CIci Direct Energy Conversion Nano scheme. This cathode also carries the negative charge.

Step 7 - Finish with a layer of alumina 10 Nm thick, this comprises the low Z isolation layer (i)

Step 8 - Repeat - the entire process (steps 2 through 8 ) over again N times.



The lamination of N layers looks like this TCAX,TCAX…TCAX

Where “T” is the anode and “A” is the cathode.

Legend: T-thorium, C-carbon, A-aluminum, X-alumina

I wonder if the whole lamination structure could also be done using a nano diamond deposition structure utilizing different layer thicknesses to provide the various insulation layer requirements and with boron doping providing the low Z conductive layer(c).

My impression is that almost none of the heat given off in spent fuel is from alpha radiation. You get that almost exclusively from TRU decays not fission products.

So sorry, I should have said mostly beta radiation instead of alpha?

Is it true that the nuclear waste products from a thorium reactor have few transuranic wastes bygone NP137(Z<=237). If true, will these wastes be less energetic that wastes produced from uranium burning during the first century; after?

I though that the short lived wastes (a few tens of years) decayed mostly by alpha and beta emissions?


The energy transfer mechanism of direct nuclear radiation conversion is a kinetic energy transformation mechanism from alpha, beta, gamma, neutrons, and nuclear fragments energy capture through high Z material ionization and does not depend on the specific radiation type.

The nano layer spacing cover the weakest radiation levels. Stronger levels of radiation ionize multiple nano-layers.

http://en.wikipedia.org/wiki/Radioactive_waste

The majority of decay power is beta, followed by gamma. I doubt that alpha decay power is significant at all. For example, the most natural flow for a thorium/uranium cycle LFTR would be for all plutonium to be extracted into the fission product stream. If this was done rapidly the plutonium will be Pu238. This is likely the maximum alpha power configuration. At 20 kg/year this would mean 10kW/yr in the fission product stream. The whole fission product stream is around 150 MWatts. Even just the salt seekers after some decay time in the fuel salt will be a megaWatt or so. The alpha decay would be something like 1% of the total.

Thinking a bit more about it this 1% will build up year after year. When I get home I'll write some s/w to evaluate this. It might be more significant than I thought.

Here is some interesting info on radiation based thermal generators.

Beta radiation is high energy electrons and could be converted to a DC electric current. The energy converted to heat could also be utilized to maximum extent. I have been recommending the use of spent fuel stored at site for this purpose. But are the technologies available? If not they need to be developed.

Reminds me of this:
A beta emitted like Tc99 is suspended in an excimer mixture. A tuned photodiode extracts teh energy. If pressurized, in a lightweight composite pressurevessel, it supposed to have an impressive power to weight.

[url]http://en.wikipedia.org/wiki/Optoelectric_nuclear_battery[/url]

A powdered beta emitter in an excimer gas, driving photodiodes.

http://en.wikipedia.org/wiki/Optoelectric_nuclear_battery