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How LIFE Works - The concept of fusion-fission hybrids

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FreakinDJ Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Apr-26-09 03:56 PM
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How LIFE Works - The concept of fusion-fission hybrids
Fairly heady stuff, but what Dr Moses is saying is if we Fast Track the LIFE Reactor the same way Pres. Kennedy Fast Tracked Americas Race to the Moon we could see Commercially Viable Nuclear Fusion in 10 15 years.

Being able to Solve Americas Energy Independence problems could be a reality. A clean permanent method of disposing of decades of Nuclear Waste (Fuel Rods), Weapons Grade Plutonium, and Depleted Uranium would be a side benefit

The concept of fusion-fission hybrids using high-energy neutrons from fusion reactions to transmute, or burn, fissile material has been explored by Andrei Sakharov, Hans Bethe and other scientists since about 1951. Although the focus of many of these studies was the use of fusion neutrons to generate fuel for fast nuclear reactors, Nikolai Basov and others discussed the possibility of using laser-driven fusion targets to drive a fission blanket for generating power. Many proposals have also been made to use accelerators to generate neutrons that can then be used to burn nuclear waste and generate electricity.

Fusion-fission engines did not advance beyond the discussion stage at that time because powerful high-average-power lasers and other required technologies did not exist. Similarly, accelerator-based schemes never advanced past the conceptual study phase, in part because a complete nuclear fuel cycle including uranium enrichment and nuclear waste reprocessing was still required to generate economical electricity. The inefficiency and cost of those systems outweighed the benefit of transmuting nuclear waste.

Today, however, researchers are close to demonstrating the physics and key technologies required to make LIFE a reality. The capability of lasers to create the conditions required for ignition and thermonuclear burn in the laboratory with inertial confinement fusion (ICF) is expected to be demonstrated on the National Ignition Facility (NIF) within the next two to three years (see How to Make a Star). The National Ignition Campaign will begin during 2009, and ignition and fusion energy yields of 10 to 15 megajoules (MJ) are anticipated during fiscal years 2010 or 2011. Fusion yields of 20 to 35 MJ are expected soon thereafter. Ultimately fusion yields of 100 MJ are expected on NIF.

With the appropriate research, development and engineering program, LIFE engines could begin to provide electricity to U.S. consumers within 20 years, and could provide a very significant fraction of U.S. and international electricity demand by 2100.

Safe, Sustainable, Carbon-Free Energy
LIFE is well suited to meet the energy demands facing our nation and our planet. Although technical challenges must be overcome, the fusion-fission LIFE engine concept provides a path to a sustainable energy future based on safe, sustainable nuclear power with minimal nuclear waste per gigawatt of electricity generated. By the end of the century, LIFE could provide into the existing grid about half of U.S. baseload electricity demand. Spent nuclear fuel from light-water reactors (LWRs) could provide fuel for LIFE for the next 200 years, and depleted uranium from the LWR fuel-enrichment process could power LIFE engines for more than 1,000 years.

The LIFE Power Plant
The LIFE development team is exploring a variety of possible fuel, target and laser configurations and energies for a prototype LIFE engine. The LIFE system is designed to operate with fusion energy gains of about 25 to 30 and fusion yields of about 35 to 50 MJ to provide about 500 megawatts (MW) of fusion power about 80 percent of which comes in the form of 14.1 million electron-volt (MeV) neutrons with the rest of the energy in X-rays and ions.

This approach to fusion generates approximately 1019 14.1-MeV neutrons per shot (about 1020 neutrons every second). When used to drive a subcritical fission "blanket," the fusion neutrons generate an additional energy gain of four to ten depending upon the details of the fission blanket, providing overall LIFE system energy gains of 100 to 300.

The fission blanket contains either 40 metric tons (MT) of depleted uranium; un-reprocessed spent nuclear fuel (SNF); natural uranium or natural thorium; or a few MT of the plutonium-239, the minor actinides such as neptunium and americium, and the fission products separated from reprocessed SNF.

The point source of fusion neutrons acts as a catalyst to drive the fission blanket, so there is no need for a critical assembly to sustain the fission chain reaction. Starting from as little as 300 to 500 MW of fusion power, a single LIFE engine can generate 2,000 to 3,000 megawatts in steady state for periods of years to decades, depending on the nuclear fuel and engine configuration. Most "pure" inertial fusion energy plant designs require laser energies of about three MJ to achieve fusion yields of 200 MJ from NIF-like targets at about 15 shots a second to generate 3,000 MW of thermal power. In contrast, the laser energy requirements of the LIFE engine to generate the same amount of thermal energy are a factor of 2 to 2.5 lower.

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