Saturday, September 20, 2008

The LFTR Emulates Natural Systems

The Rocky Mountain Institute advocates using the closed loop sort of materials and energy handling system found in nature:
Using nature as mentor, model, and measure often yields superior design solutions that profitably eliminate waste, loss, and harm.

Natural systems operate in closed loops. There's no waste—every output is either returned harmlessly to the ecosystem as a nutrient, like compost, or becomes an input for another process. In contrast, the standard industrial model of our age is a linear sequence of "take, make, and waste" — extract resources, use them, and throw them away — a process that erodes our stock of natural capital by depleting resources and replacing them with wastes.

Reducing the wasteful throughput of materials — indeed, eliminating the very idea of waste — can be accomplished by redesigning industrial systems on biological lines that change the nature of industrial processes and materials, enabling the constant reuse of materials in continuous closed cycles, and often the elimination of toxicity.

The LFTR had its origin in the desires of the great scientists, Eugene Wigner and Alvin Weinberg to eliminate the wastefulness of early reactors. They saw that in order to eliminate waste from nuclear systems, materials had to flow from one process to another. Most reactors use a structured core with solid fuel that is moved mechanically in and out of the reactor. Nuclear fuel is desiogned only to serve as fuel in a nuclear reactor. It is difficult to repricess. Eugene Wigner was trained as a chemical engineer, and thought in terms of efficient use of materials. And of the efficient transport of chemicals dissolved in, suspended in or bonded to liquids that flowed from process to process, within a chemical plant. Alvin Weinberg was trained in biology as well as in physics. He understood the role of fluid flow in live systems, and how fluids carried materials form one biological process to another. Weinberg also understood the transport of materials between organisms in environmental systems.

Wigner and Weinberg believed that reactors could, in effect, be turned int o closed loop systems in which little would really go to waste. It is impossible, according to the second law of thermodynamics, to design a system in which nothing hoes to waste. But it my be possible to design more efficient systems. Wigner and Weinberg determined that Thorium was a more efficient basis for nuclear fuel than uranium. The efficiency of the thorium fuel cycle rests on something called "neutron economy", that is the efficient use of neutrons produced in a nuclear process.

Neutron are the keys to both chain reactions, and the creation of nuclear fuel inside reactors. The nuclear fuel for thorium cycle reactors is Uranium-233, and U-233 has the best neuton efficiency of any fissionable material. The efficiency of the LFTR rests on its emulation of living organisms. Like living organisms it has a system to produce and distribute energy, a system to rid itself to of unwanted heat and materials, and systems to recapture energy, and the eliminated materials. Recapture of energy can be used for heat in industrial processes including hydrogen production, also for water desalinization, or for space heating, and of course to produce electricity, Recaptured materials can be used in industry, medicine, in food preservation, and in sanitation. Nothing need go to waste.

The LFTR also operates with thermal efficiency. It is capable of operating at a much higher heat than conventional reactors. High temperatures create potential for greater thermal efficiency. In addition, the use of closed cycle gas turbines create the potential for greater generating efficiency. The use of bottom cycle heat for space heating or desalinization, holds promise to further increase thermal efficiency,

The LFTR is efficient in terms of materials use. Some of the essential material used in the LFRT including Thorium are essentially wasted now in existing industrial processes. Other materials like graphite, can be manufactured, and thus are virtually renewable resources. Resources like nickel are rarer than craphite, but their use is LFTR is fully justified because no other energy use for Nickel would bring as high a rate of energy return.

A further efficiency of the LFTR is its capacity efficiency . The LFTR is capable of producing electricity 24 hours a day for extended periods of time. Unlike Light Water Reactors which must be shut down periodically for refueling, new fuel can be added to the LFTR while the reactor is operating. Thus the LFTR can operate continuously at 100% of capacity but need not do so.

The LFTR is demand efficient. Renewable energy systems, like Solar and wind generation produce electricity without any relationship to demand. Windmills generate electricity when moderate winds are blowing, but not in high winds, or on calm days. PV solar output varies with light conditions, while the electrical out put of Concentrated Solar generators is effected by clouds and dust storms. All Solar generation systems produce more electricity over a longer periods of time during the summer than during the winter. Generated output from renewables like solar and wind, cannot be regulated by consumer demand. When renewables produce more electricity than the market demands, excess electricity has to be dumped. This is a significant inefficiency. On other occasions renewable generated electricity is sold on the spot market for at loss. Owner of renewables demand financial subsidies to cover costs during the frequent periods when the selling price of renewable generated electricity is sold at a loss.

In contrast the LFTR can always generate the amount of electricity consumers demand. The temperature of reactor salts rises as load drops, and as salt temperature rises, reactor salt expands, and thus is expelled from the reactor core. The loss of salt and fuel from the core slows and eventually stops the fission process, but the reactor salts continue to draw heat from the radioactive decay of fission products. Thus the salt will remain hot until consumer demnd leads to electrical generation, and the electrical generation process, draws heat from reactor salts, lowering salt temperature, shrinking salt volume, drawing nuclear fuel back into the core, and starting the chain reaction again. This system allows for power to be immediately available from stopped reactors without neutron or fuel loss. Demand efficiency is the ability to respond quickly and automatically to ups and downs in grid electrical demand. Renewables just can't do that, and convintional reactors cost to much to operate at any rate other than 100% of capacity.

Finally the LFTR is time efficient. Unlike renewables the LFTR can produce power at any time. Unlike conventional Light Water Reactors the LFTR does not need to stop producing power during refueling. Because of then LFTRs high level of inherent and passive safety, it is far less likely to experience emergency shutdown than LWRs. This means that 100% of the LFTR capacity will be online virtually 100% of the time. Renewables and conventional nuclear do not match this temporal efficiency.


Soylent said...

"There's no waste—every output is either returned harmlessly to the ecosystem as a nutrient, like compost, or becomes an input for another process."

This is a patently absurd statement.

Less than 0.1% of incident sunlight is even turned into biomass.

Mineral nutrients are in chronic short supply in nature; mineral nutrients eventually end up in sediment on the sea floor or mineral deposits not available to organisms. It has to be continually replenished by erosion of rock to become available for organisms to use.

Coal, natural gas, oil shale and oil are all waste. An enormous amount of gas and oil, much more than currently available, has seeped to the surface and been oxidized by air without organisms being able to harness this energy.

Most limestone is composed of microscopic plankton shells, dead corals and other fragments from living organisms.

"In contrast, the standard industrial model of our age is a linear sequence of "take, make, and waste" — extract resources, use them, and throw them away — a process that erodes our stock of natural capital by depleting resources and replacing them with wastes."

Waste is being used in two different senses here.

When humans throw away food it is regarded as a waste. When nature throws away food it is regarded as recycling. In both cases bacteria, worms, crows, flies, rats, molds and other opportunists will step in and treat it as a resource.

When nature makes a mineral deposit is not regarded as waste; when we make a landfill, which is this rich deposits of mineral and all sorts of other things, it is regarded as waste.

Charles Barton said...

Ya I know, Lovins is supposed to be a physicist. I thought about pointing out the absurdity, but decided that we know the Emperor has no clothes, so why say it when that is not what I am after.


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