In nuclear physics, an energy amplifier is a novel type of nuclear power reactor, a subcritical reactor, in which an energetic particle beam is used to stimulate a reaction, which in turn releases enough energy to power the particle accelerator and leave an energy profit for power generation.

History

The concept is credited to Carlo Rubbia, a nuclear physicist and former director of Europe's CERN international nuclear physics lab. He published a proposal for a power reactor based on a proton cyclotron accelerator with a beam energy of 800 MeV to 1 GeV, and a fuel/moderator target with thorium as fuel and lead as a moderator.

Advantages

The concept has several advantages over conventional nuclear fission reactors:

• No overlap with the nuclear weapons fuel cycle — the energy amplifier cannot be used as a basis for creating weapons, so it can be used in politically-unstable countries.

• Subcritical design means that the reaction cannot run away — if anything goes wrong, the reaction stops and the reactor cools down. A meltdown or explosion cannot happen, making the amplifier an inherently safer design.

• Thorium is an abundant element — much more so than uranium — reducing strategic and political supply issues and eliminating costly isotope separation. There is enough thorium to generate energy for thousands of years at current consumption rates.

• No long-lived radioactive waste is produced — the waste decays after 500 years to the level of coal ash. The amplifier can actually be used to transform long-lived waste (plutonium) from conventional reactors into safer substances.

• No new science is required; the technologies to build the energy amplifier have all been demonstrated. Building an energy amplifier requires only some engineering effort, not fundamental research (unlike nuclear fusion proposals).

• Power generation would be economical compared to current nuclear reactor designs if the total fuel cycle and decommissioning costs are considered.

• Ease of operation, inherent safety, and safe fuel transport makes the technology more suitable for developing countries.

• Operation of the amplifier itself does not produce CO₂. When thorium production and power station construction are considered, the energy amplifier is a very low-carbon power technology.

How it works

The energy amplifier uses a cyclotron accelerator to produce a beam of protons. These hit a thorium target and produce neutrons by the process called spallation. Thorium nuclei absorb neutrons, forming fissile uranium-233. This isotope of uranium is not found in nature and is not the isotope used in nuclear weapons. Moderated neutrons stimulate U-233 fission, releasing energy.

If a beam energy of 7 megawatts (7 mA protons produced by a 1 GeV cyclotron) is used, the energy amplifier would produce 280 MW of thermal energy, corresponding to about 100 MW of electrical power after steam production and turbine generation. As the power needed to operate the accelerator is about 20 MW, there would thus be a net production of over 80 MW. Larger designs could achieve higher energy gains in the range of 30 to 60%.