Energy amplifier

Last updated February 17, 2024

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. The concept has more recently been referred to as an accelerator-driven system (ADS) or accelerator-driven sub-critical reactor.

History

The concept is credited to Italian scientist Carlo Rubbia,^[1] a Nobel Prize particle physicist and former director of Europe's CERN international nuclear physics lab. He published a proposal for a power reactor (nicknamed "Rubbiatron") based on a proton cyclotron accelerator with a beam energy of 800 MeV to 1 GeV, and a target with thorium as fuel and lead as a coolant. Rubbia's scheme also borrows from ideas developed by a group led by nuclear physicist Charles Bowman of the Los Alamos National Laboratory^[2]

Principle and feasibility

The energy amplifier first uses a particle accelerator (e.g. linac, synchrotron, cyclotron or FFAG) to produce a beam of high-energy (relativistic) protons. The beam is directed to smash into the nucleus of a heavy metal target, such as lead, thorium or uranium. Inelastic collisions between the proton beam and the target results in spallation, which produces twenty to thirty neutrons per event.^[3] It might be possible to increase the neutron flux through the use of a neutron amplifier, a thin film of fissile material surrounding the spallation source; the use of neutron amplification in CANDU reactors has been proposed. While CANDU is a critical design, many of the concepts can be applied to a sub-critical system.^[4]^[5] Thorium nuclei absorb neutrons, thus breeding fissile uranium-233, an isotope of uranium which is not found in nature. Moderated neutrons produce U-233 fission, releasing energy.

This design is entirely plausible with currently available technology, but requires more study before it can be declared both practical and economical.

OMEGA project (option making of extra gain from actinides and fission products ( オメガ計画 )) is being studied as one of methodology of accelerator-driven system (ADS) in Japan.^[6]

Richard Garwin and Georges Charpak describe the energy amplifier in detail in their book "Megawatts and Megatons: A Turning Point in the Nuclear Age?" (2001) on pages 153-163.

Earlier, the general concept of the energy amplifier, namely an accelerator-driven sub-critical reactor, was covered in "The Second Nuclear Era" (1985) pages 62–64, by Alvin M. Weinberg and others.

Advantages

The concept has several potential advantages over conventional nuclear fission reactors:

Subcritical design means that the reaction could not run away — if anything went wrong, the reaction would stop and the reactor would cool down. A meltdown could however occur if the ability to cool the core was lost.
Thorium is an abundant element — much more so than uranium — reducing strategic and political supply issues and eliminating costly and energy-intensive isotope separation. There is enough thorium to generate energy for at least several thousand years at current consumption rates.^[7]
The energy amplifier would produce very little plutonium, so the design is believed to be more proliferation-resistant than conventional nuclear power (although the question of uranium-233 as nuclear weapon material must be assessed carefully).
The possibility exists of using the reactor to consume plutonium, reducing the world stockpile of the very-long-lived element.
Less long-lived radioactive waste is produced — the waste material would decay after 500 years to the radioactive level of coal ash.
No new science is required; the technologies to build the energy amplifier have all been demonstrated. Building an energy amplifier requires only engineering effort, not fundamental research (unlike nuclear fusion proposals).
Power generation might be economical compared to current nuclear reactor designs if the total fuel cycle and decommissioning costs are considered.
The design could work on a relatively small scale, and has the potential to load-follow by modulating the proton beam, making it more suitable for countries without a well-developed power grid system.
Inherent safety and safe fuel transport could make the technology more suitable for developing countries as well as in densely populated areas.
Desired nuclear transmutation could be employed deliberately (rather than as an unavoidable consequence of nuclear fission and neutron irradiation) either to transmute high level waste (such as long-lived fission products or minor actinides) into less harmful substances, for producing radionuclides for use in nuclear medicine or to produce precious metals from low-priced feedstocks.
The lower fraction of delayed neutrons in the fission of ²³⁹
Pu compared to ²³⁵
U, which hampers the use of plutonium-containing fuels in critical reactors (which need to operate in the narrow band of neutron flux between prompt critical and delayed critical), is of no concern as no criticality of any kind is achieved or needed
While nuclear reprocessing runs into the problem that MOX-fuel can not be further recycled for use in current light-water reactors as the reactor-grade plutonium concentration of fissile isotopes is not achieved due to ²⁴⁰
Pu impurities exceeding acceptable levels, all fissile and fertile isotopes of actinoids can be "burned" in a subcritical reactor, thus closing the nuclear fuel cycle without the need for fast breeder reactors

Disadvantages

Each reactor needs its own facility (particle accelerator) to generate the high energy proton beam, which is very costly. Apart from linear particle accelerators, which are very expensive, no proton accelerator of sufficient power and energy (> ~12 MW at 1 GeV) has ever been built. Currently, the Spallation Neutron Source utilizes a 1.44 MW proton beam to produce its neutrons, with upgrades envisioned to 5 MW.^[8] Its 1.1 billion USD cost included research equipment not needed for a commercial reactor. Economies of scale might come into play if particle accelerators (which are currently only rarely built to the above mentioned strengths and then only for research purposes) become a more "mundane" technology. A similar effect can be observed when comparing the cost of the Manhattan Project up to the construction of Chicago Pile-1 to the costs of subsequent research or power reactors.
The fuel material needs to be chosen carefully to avoid unwanted nuclear reactions. This implies a full-scale nuclear reprocessing plant associated with the energy amplifier.^[9]
If, for whatever reason, neutron flux exceeds design specifications enough for the assembly to reach criticality, a criticality accident or power excursion can occur. Unlike a "normal" reactor, the scram mechanism only calls for the "switching off" of the neutron source, which wouldn't help if more neutrons are constantly produced than consumed (i.e. Criticality), as there is no provision to rapidly increase neutron consumption e.g. via the introduction of a neutron poison.
Using lead as a coolant has similar disadvantages to those described in the article on lead cooled fast reactors
Many of the current spallation-based neutron sources used for research are "pulsed" i.e. they deliver very high neutron fluxes for very short durations of time. For a power reactor a smaller but more constant neutron flux is desired. The European Spallation Source will be the strongest neutron source in the world (measured by peak neutron flux) but will only be capable of very short (on the order of milliseconds) pulses.

Related Research Articles

Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radioactive decay.

In nuclear physics, a nuclear chain reaction occurs when one single nuclear reaction causes an average of one or more subsequent nuclear reactions, thus leading to the possibility of a self-propagating series or "positive feedback loop" of these reactions. The specific nuclear reaction may be the fission of heavy isotopes. A nuclear chain reaction releases several million times more energy per reaction than any chemical reaction.

<span class="mw-page-title-main">Nuclear reactor</span> Device used to initiate and control a nuclear chain reaction

A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat from nuclear fission is passed to a working fluid, which in turn runs through steam turbines. These either drive a ship's propellers or turn electrical generators' shafts. Nuclear generated steam in principle can be used for industrial process heat or for district heating. Some reactors are used to produce isotopes for medical and industrial use, or for production of weapons-grade plutonium. As of 2022, the International Atomic Energy Agency reports there are 422 nuclear power reactors and 223 nuclear research reactors in operation around the world.

In nuclear engineering, fissile material is material that can undergo nuclear fission when struck by a neutron of low energy. A self-sustaining thermal chain reaction can only be achieved with fissile material. The predominant neutron energy in a system may be typified by either slow neutrons or fast neutrons. Fissile material can be used to fuel thermal-neutron reactors, fast-neutron reactors and nuclear explosives.

A neutron source is any device that emits neutrons, irrespective of the mechanism used to produce the neutrons. Neutron sources are used in physics, engineering, medicine, nuclear weapons, petroleum exploration, biology, chemistry, and nuclear power.

The nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel through a series of differing stages. It consists of steps in the front end, which are the preparation of the fuel, steps in the service period in which the fuel is used during reactor operation, and steps in the back end, which are necessary to safely manage, contain, and either reprocess or dispose of spent nuclear fuel. If spent fuel is not reprocessed, the fuel cycle is referred to as an open fuel cycle ; if the spent fuel is reprocessed, it is referred to as a closed fuel cycle.

Mixed oxide fuel, commonly referred to as MOX fuel, is nuclear fuel that contains more than one oxide of fissile material, usually consisting of plutonium blended with natural uranium, reprocessed uranium, or depleted uranium. MOX fuel is an alternative to the low-enriched uranium fuel used in the light-water reactors that predominate nuclear power generation.

<span class="mw-page-title-main">Uranium-238</span> Isotope of uranium

Uranium-238 is the most common isotope of uranium found in nature, with a relative abundance of 99%. Unlike uranium-235, it is non-fissile, which means it cannot sustain a chain reaction in a thermal-neutron reactor. However, it is fissionable by fast neutrons, and is fertile, meaning it can be transmuted to fissile plutonium-239. ²³⁸U cannot support a chain reaction because inelastic scattering reduces neutron energy below the range where fast fission of one or more next-generation nuclei is probable. Doppler broadening of ²³⁸U's neutron absorption resonances, increasing absorption as fuel temperature increases, is also an essential negative feedback mechanism for reactor control.

A subcritical reactor is a nuclear fission reactor concept that produces fission without achieving criticality. Instead of sustaining a chain reaction, a subcritical reactor uses additional neutrons from an outside source. There are two general classes of such devices. One uses neutrons provided by a nuclear fusion machine, a concept known as a fusion–fission hybrid. The other uses neutrons created through spallation of heavy nuclei by charged particles such as protons accelerated by a particle accelerator, a concept known as an accelerator-driven system (ADS) or accelerator-driven sub-critical reactor.

<span class="mw-page-title-main">Spallation</span> Physical process

Spallation is a process in which fragments of material (spall) are ejected from a body due to impact or stress. In the context of impact mechanics it describes ejection of material from a target during impact by a projectile. In planetary physics, spallation describes meteoritic impacts on a planetary surface and the effects of stellar winds and cosmic rays on planetary atmospheres and surfaces. In the context of mining or geology, spallation can refer to pieces of rock breaking off a rock face due to the internal stresses in the rock; it commonly occurs on mine shaft walls. In the context of anthropology, spallation is a process used to make stone tools such as arrowheads by knapping. In nuclear physics, spallation is the process in which a heavy nucleus emits numerous nucleons as a result of being hit by a high-energy particle, thus greatly reducing its atomic weight. In industrial processes and bioprocessing the loss of tubing material due to the repeated flexing of the tubing within a peristaltic pump is termed spallation.

Nuclear fuel is material used in nuclear power stations to produce heat to power turbines. Heat is created when nuclear fuel undergoes nuclear fission.

The Bhabha Atomic Research Centre (BARC) is India's premier nuclear research facility, headquartered in Trombay, Mumbai, Maharashtra, India. It was founded by Homi Jehangir Bhabha as the Atomic Energy Establishment, Trombay (AEET) in January 1954 as a multidisciplinary research program essential for India's nuclear program. It operates under the Department of Atomic Energy (DAE), which is directly overseen by the Prime Minister of India.

<span class="mw-page-title-main">Fertile material</span>

Fertile material is a material that, although not fissile itself, can be converted into a fissile material by neutron absorption.

Plutonium-239 is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 is also used for that purpose. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in thermal spectrum nuclear reactors, along with uranium-235 and uranium-233. Plutonium-239 has a half-life of 24,110 years.

The thorium fuel cycle is a nuclear fuel cycle that uses an isotope of thorium, ²³²
Th, as the fertile material. In the reactor, ²³²
Th is transmuted into the fissile artificial uranium isotope ²³³
U which is the nuclear fuel. Unlike natural uranium, natural thorium contains only trace amounts of fissile material, which are insufficient to initiate a nuclear chain reaction. Additional fissile material or another neutron source is necessary to initiate the fuel cycle. In a thorium-fuelled reactor, ²³²
Th absorbs neutrons to produce ²³³
U. This parallels the process in uranium breeder reactors whereby fertile ²³⁸
U absorbs neutrons to form fissile ²³⁹
Pu. Depending on the design of the reactor and fuel cycle, the generated ²³³
U either fissions in situ or is chemically separated from the used nuclear fuel and formed into new nuclear fuel.

<span class="mw-page-title-main">Liquid fluoride thorium reactor</span> Type of nuclear reactor that uses molten material as fuel

The liquid fluoride thorium reactor is a type of molten salt reactor. LFTRs use the thorium fuel cycle with a fluoride-based molten (liquid) salt for fuel. In a typical design, the liquid is pumped between a critical core and an external heat exchanger where the heat is transferred to a nonradioactive secondary salt. The secondary salt then transfers its heat to a steam turbine or closed-cycle gas turbine.

Hybrid nuclear fusion–fission is a proposed means of generating power by use of a combination of nuclear fusion and fission processes.

Nuclear transmutation is the conversion of one chemical element or an isotope into another chemical element. Nuclear transmutation occurs in any process where the number of protons or neutrons in the nucleus of an atom is changed.

An accelerator-driven subcritical reactor (ADSR) is a nuclear reactor design formed by coupling a substantially subcritical nuclear reactor core with a high-energy proton or electron accelerator. It could use thorium as a fuel, which is more abundant than uranium.

The MYRRHA is a design project of a nuclear reactor coupled to a proton accelerator. This makes it an accelerator-driven system (ADS). MYRRHA will be a lead-bismuth cooled fast reactor with two possible configurations: sub-critical or critical.

References

↑ Rubbiatron, il reattore da Nobel, Massimo Cappon, CERN docs server: Panorama , 11 giugno 1998. Also: File pdf.
↑ Aldhous, Peter (Nov 1993). "Rubbia Floats a Plan for Accelerator Power Plants". Science. 262 (5138): 1368. Bibcode:1993Sci...262.1368A. doi:10.1126/science.262.5138.1368. PMID 17736803 . Retrieved 6 March 2022.
↑ "Spallation Target | Paul Scherrer Institut (PSI)". Psi.ch. Retrieved 2016-08-16.
↑ http://www.tfd.chalmers.se/~valeri/Mars/Mo-o-f10.pdf ^{[ bare URL PDF ]}
↑ "Neutron amplification in CANDU reactors" (PDF). CANDU. Archived from the original (PDF) on 2007-09-29.
↑ 大電流電子線加速器の性能確認試験 [Performance of Ｈigh Power CW Electron Linear Accelerator](PDF) (in Japanese). Ōarai, Ibaraki: Japan Atomic Energy Agency. December 2000. Retrieved 2013-01-21.
↑ "Ch 24 Page 166: Sustainable Energy - without the hot air | David MacKay". www.inference.org.uk.
↑ http://accelconf.web.cern.ch/AccelConf/e04/PAPERS/TUPLT170.PDF ^{[ bare URL PDF ]}
↑ Conceptual design of a fast neutron operated high power energy amplifier, Carlo Rubbia et al., CERN/AT/95-44, pages 42 ff., section Practical considerations

A PRELIMINARY ESTIMATE OF THE ECONOMIC IMPACT OF THE ENERGY AMPLIFIER – An in-depth review of the Energy Amplifier co-authored by Rubbia (pdf download available from the CERN document server)
Christoph Pistner, Emerging Nuclear Technologies: The Example of Carlo Rubbia's Energy Amplifier, International Network of Engineers and Scientists Against Proliferation

External links

New Age Nuclear: article on energy amplifiers | Cosmos Magazine

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[1] Rubbiatron, il reattore da Nobel, Massimo Cappon, CERN docs server: Panorama , 11 giugno 1998. Also: File pdf.

[2] Aldhous, Peter (Nov 1993). "Rubbia Floats a Plan for Accelerator Power Plants". Science. 262 (5138): 1368. Bibcode:1993Sci...262.1368A. doi:10.1126/science.262.5138.1368. PMID 17736803 . Retrieved 6 March 2022.

[3] "Spallation Target | Paul Scherrer Institut (PSI)". Psi.ch. Retrieved 2016-08-16.

[4] ttp://www.tfd.chalmers.se/~valeri/Mars/Mo-o-f10.pdf ^{[ bare URL PDF ]}

[5] "Neutron amplification in CANDU reactors" (PDF). CANDU. Archived from the original (PDF) on 2007-09-29.

[6] 大電流電子線加速器の性能確認試験 [Performance of Ｈigh Power CW Electron Linear Accelerator](PDF) (in Japanese). Ōarai, Ibaraki: Japan Atomic Energy Agency. December 2000. Retrieved 2013-01-21.

[7] "Ch 24 Page 166: Sustainable Energy - without the hot air | David MacKay". www.inference.org.uk.

[8] ttp://accelconf.web.cern.ch/AccelConf/e04/PAPERS/TUPLT170.PDF ^{[ bare URL PDF ]}

[9] Conceptual design of a fast neutron operated high power energy amplifier, Carlo Rubbia et al., CERN/AT/95-44, pages 42 ff., section Practical considerations

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