Toshiba is in talks Terrapower, a company backed by Bill Gates, to jointly develop traveling wave nuclear reactors which are designed to use depleted uranium as fuel and could run for 60 years or more without refueling. (See http://www.greenbizcafe.com/?p=881 for a description of travelling wave reactors.)

Toshiba owns the Westinghouse Electric Company whose technology is the basis for about half of the world’s commercial nuclear reactors.

Toshiba is already developing its own mini nuclear reactors designed to operate continuously for 30 years and believes that 80 percent of the technologies used in the reactor under development can be applied to traveling-wave reactors.

Toshiba anticipates that commercialisation of traveling wave reactors could take about ten years.

A traveling-wave reactor is a kind of nuclear reactor that can convert fertile material into nuclear fuel as it runs. Travelling wave reactors differ from other kinds of  reactors in their ability to use little or no enriched uranium; instead they burn fuel made from depleted uranium, spent fuel removed from light-water reactors, natural uranium, thorium, or some combination of these materials.

They are called "travelling wave" because fission does not take place in the entire reactor core but in a localized zone that advances through the core over time.

Unlike other reactors, travelling wave reactors can be fueled at the time of construction with enough depleted uranium to produce full power for 60 years or more. Depleted uranium, which is produced as a waste byproduct of the enrichment process, is widely available as a feedstock. Stockpiles in the United States alone currently contain approximately 700,000 tonnes of depleted uranium. It has been estimated that these stockpiles represent an energy resource equivalent to $100 trillion worth of electricity.

No traveling wave reactor has yet been constructed but, in 2006, TerraPower LLC, a company whose principal owner is Bill Gates, was established  to model and commercialize a practical travelling wave reactor. TerraPower has developed designs for low- to medium-power (300 megawatt) and large power (1000 megawatt) reactors.

Scientists have been working on developing nuclear fusion power generation since the early 1950s. The main problem has always been that more energy has been required to produce the reaction than is produced.

Scientists at the National Ignition Facility in California believe that their latest experiments will overcome the problem.

Their technique uses lasers to concentrate isotopes of hydrogen. The pressures and densities achieved are close to what occurs in the sun. At these densities. mass becomes energy in the form of heat which can be used to drive a turbine.

A demonstration reactor is expected to begin testing later this year and to be in operation within two years. If successful, the scientsist believe that they could have a power plant delivering electricity to the grid within ten years. Electricity produced in this way would be economical, carbon free and effectively limitless.

However, other scientists are more sceptical.
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A Canadian company, General Fusion, claims that it can build a relatively low-tech prototype nuclear fusion power plant within the next decade for less than a billion dollars.

For decades, billions of dollars have been spent on research into ways of building a practical fusion reactor for electricity production. The major problem is creating a controllable fusion reaction that gives off more energy than is needed to trigger it and most scientists believe that achieving this will take several more decades and cost tens billions of dollars.

General Fusion’s approach involves building a metal sphere about three metres in diameter filled with a liquid lead-lithium mixture. This liquid is spun to open up a vertical cylindrical cavity in the center of the sphere. Two magnetized plasma rings composed of deuterium-tritium fuel are then injected into each end of the cavity and merge in the centre.

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The first generation of nuclear power plants were the experimental plants ot the 1950s and early 60s, which were also used to power nuclear submarines. The second generation were the commercial plants from the later 1960s to the 1990s.

After the Three-mile Island and Chernobyl accidents, a third generation of nuclear plants was developed. These emphasise improved fuel technology, superior thermal efficiency, passive safety systems and standardized design for reduced maintenance and capital costs and longer life (60 years compared to 40 years for Generation 11 reactors). However, the technology is basically the same as in older reactors.

Most of these are "light water reactors" meaning that they use ordinary water for cooling and to transfer the heat from the nuclear reation to the turbines that generate electricity. Most do this by making steam; most of the rest use pressured water.

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The Italian senate has voted 154-1 to overturn a 22-year-old prohibition on new nuclear power stations. Their decision is line with those taken recently in several other European countries as a means of reducing their carbon dioxide emissions.

Sweden has lifed its 29-year ban on new nuclear plants, Spain has begun to reverse its 25-year old policy of phasing out nuclear power. The Netherlands abandoned its policy of phasing out nuclear power in 2005. Germany’s coalition government is continuing the policy, introduced in 2001, of phasing out nuclear power by 2020 but Chancellor Angela Merkel has promised to abandon the policy if she wins elections in September. The UK government has reaffirmed that atomic power is central to the strategy for building a low-carbon Britain and is considering plans to build the first new reactors in over 20 years.

France, which gets 77% of its electricity from 59 nuclear power plants, is buillding an improved third generation "European Pressurised Reactor" in Normandy. The project is intended to be a prototype for up to forty power plants. Italy is already undertaking a feasibility study to construct four of the plants.

Europe currently has a total of 165 nuclear rectors with six under construction and several more planned.

John Wellinghoff, the Chairman of the U.S. Federal Energy Regulatory Commission has told a U.S. Energy Association forum.that no new nuclear or coal plants may ever be needed in the United States,

"We may not need any, ever," Mr Wellinghoff said. Renewables like wind, solar and biomass will provide enough energy to meet baseload capacity and future energy demands. Nuclear and coal plants are too expensive, he added.

"I think baseload capacity is going to become an anachronism," he said. "Baseload capacity really used to only mean in an economic dispatch, which you dispatch first, what would be the cheapest thing to do. Well, ultimately wind’s going to be the cheapest thing to do, so you’ll dispatch that first."

He added, "People talk about, ‘Oh, we need baseload.’ It’s like people saying we need more computing power, we need mainframes. We don’t need mainframes, we have distributed computing."

"What you have to do, is you have to be able to shape it," he added. "And if you can shape wind and you can effectively get capacity available for you for all your loads.

"So if you can shape your renewables, you don’t need fossil fuel or nuclear plants to run all the time. And, in fact, most plants running all the time in your system are an impediment because they’re very inflexible. You can’t ramp up and ramp down a nuclear plant. And if you have instead the ability to ramp up and ramp down loads in ways that can shape the entire system, then the old concept of baseload becomes an anachronism."

"I think it’s being settled by the digital grid moving forward," he said. "We are going to have to go to a smart grid to get to this point I’m talking about."

In 1989, Martin Fleischmann and Stanley Pons anounced that they had demonstrated the production of excess heat during electrolysis with palladium cathodes in heavy water. The phenomenon was dubbed "cold fusion" and their claims were quickly dismissed.

However, many laboratories have since repeated their expeiments. Although most have failed, a few have reported success. A 2007 review determined that more than 10 groups world wide reported measurements of excess heat in a third of their experiments. Most of the research groups reported occasionally seeing 50-200% excess heat for periods lasting hours or days.

If the production of excess heat is real, it could be a source of cheap, pollution-free energy.

The American "60 Minutes" has produced the following review of the current state the science:

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“Conventional” nuclear fusion reactors work by fusing deuterium and tritium to produce helium-4, a neutron and enormous heat and radiation. The heat is used to boil water and the resulting steam drives a turbine.

Several experimental nuclear fusion reactors based on this principle have been built but none has yet produced more power than it has consumed. The project leading the effort to produce commercial fusion power is the ITER project by an international consortium led by the European Union and based in Cadarache in southern France. The ITER project anticipates its first net power generation will be by 2038 with a commercial power plant by 2050.

The difficulty with these reactors is containing the heat and radiation which they produce. In effect, what they are trying to do is explode a hydrogen bomb, contain the radiation and capture the heat in order to boil water.

An alternative fusion process is based on helium-3 (He-3). When He-3 is fused, it produces a stream of protons and very little heat or radiation. An alternative process fuses helium-3 with deuterium. This produces helium-4 and a stream of protons. Click here to read the rest of this entry.

In a conventional nuclear reactor the input fuel is uranium-235 (U-235) which is part of a much larger mass of uranium – mostly U-238. This U-235 is progressively “burned” over about three years to yield a lot of heat. This fission of U-235 causes some of the U-238 to turn into plutonium-239, which behaves almost identically to U-235. So, some of the U-235 effectively renews itself by producing Pu-239 from the otherwise waste U-238.

In a “breeder reactor”, the reactor is configured to "breed" more Pu-239 than it consumes; so that the system can run indefinitely – in a sense, making the process “renewable”. However, there does need to be steady input of reprocessing activity to separate the fissile plutonium from the uranium and other materials. This is fairly expensive but basically straightforward and well-proven. 

As well as uranium and plutonium, thorium can be used as a nuclear fuel. The process is similar to, but more efficient than, a uranium breeder reactor.

The process is normally started with a radioactive material such as U-233, U-235 or PU-239. The thorium absorbs neutrons from the seed material and then decays, “breeding” U-233, which is an excellent reactor fuel.

Thorium has several advantages over uranium as a reactor fuel. Click here to read the rest of this entry.