Very Big Accelerators as Energy Producers

One consequence of the application of superconductivity to accelerator construction is that the power consumption of accelerators will become much smaller. This raises the old possibility of using high energy protons to make neutrons which are then absorbed by fertile uranium or thorium to make a fissionable material like plutonium that can be burned in a nuclear reactor. The Energy Doubler/Saver being constructed at Fermilab is to be a superconducting accelerator that will produce 1000 GeV protons. The expected intensity of about $10^{12}$ protons per second corresponds to a beam power of about 0.2 MW. The total power requirements of the Doubler will be about 20 MW of which the injector complex will use approximately 13 MW, and the refrigeration of the superconducting magnets will use about 7 MW. Thus the beam power as projected is only a few orders of magnitude less than the accelerator power. But each 1000 GeV proton will produce about 60,000 neutrons in each nuclear cascade shower that is releaseq in a block of uranium, and then most of these neutrons will be absorbed to produce 60,000 plutonium a toms. Each of these when burned will Subsequently release about 0.2 GeV of fission energy to make a total energy of 12,000 GeV (20 ergs) for each 1000 GeV proton. Inasmuch as megawatts are involved, it appears to be worthwhile to consider the cost of making the protons to see if there could be an overall energy production.

💡 Research Summary

The paper investigates whether a modern superconducting particle accelerator could serve not only as a research tool but also as a net energy‑producing device by breeding fissile material. Using the Fermilab Energy Doubler/Saver as a concrete example, the author outlines the accelerator’s specifications: a 1 TeV proton beam with a current of 10¹² protons s⁻¹, delivering a beam power of roughly 0.2 MW while the whole facility consumes about 20 MW (13 MW for the injector complex and 7 MW for cryogenic refrigeration of the superconducting magnets).

The core physics premise is that each 1 TeV proton, when dumped into a block of fertile material such as natural uranium or thorium, initiates a high‑energy spallation cascade that liberates on the order of 60 000 neutrons. These neutrons are overwhelmingly captured by ²³⁹U (or ²³²Th) nuclei, transmuting them into ²⁴⁰Pu (or ²³³U) – both of which are readily fissionable. The author assumes that each newly created fissile atom, when later burned in a conventional reactor, releases about 0.2 GeV (≈200 MeV) of energy. Multiplying 60 000 atoms by 0.2 GeV yields a total of 12 000 GeV (≈12 TeV) of fission energy per incident proton, i.e., a theoretical energy‑gain factor of twelve relative to the kinetic energy supplied to the proton.

A straightforward energy‑balance calculation follows. With a 0.2 MW beam, the accelerator would deliver roughly 6.3 × 10¹⁸ protons per year. At 60 000 neutrons (and thus 60 000 fissile atoms) per proton, the annual production of plutonium would be about 3.8 × 10²³ atoms, corresponding to roughly 0.06 kg of Pu. Burning this quantity releases ≈19 GJ, or about 5.3 MWh of electrical energy per year. Compared with the 20 MW (≈175 GWh yr⁻¹) power required to run the accelerator, the net gain is negative by more than an order of magnitude.

The paper then discusses the practical obstacles that erode the theoretical gain. First, the spallation target would be subjected to extreme thermal loads and intense radiation damage, demanding sophisticated cooling and frequent replacement. Second, the chemical separation of the newly bred plutonium from the target matrix is energy‑intensive and costly, and it introduces proliferation concerns. Third, the overall electrical efficiency of a superconducting accelerator is limited by RF power conversion (typically 5–10 % efficiency) and cryogenic losses, resulting in a total wall‑plug‑to‑beam efficiency well below 1 %. Fourth, scaling the beam current by orders of magnitude to approach parity with the plant’s electrical consumption would require breakthroughs in high‑current ion sources, beam transport, and loss mitigation.

Consequently, while the concept demonstrates an intriguing “energy‑amplifier” effect at the particle‑physics level, the author concludes that, with present‑day technology, a superconducting accelerator cannot serve as a viable net power producer. The modest net energy return is outweighed by the substantial capital and operational costs, as well as the engineering challenges of target survivability, fuel reprocessing, and overall system efficiency.

The paper suggests that future advances—such as ultra‑high‑current superconducting linacs, radiation‑hard target materials, and integrated on‑site fuel‑cycle facilities—could improve the economics, but until such technologies mature, accelerator‑driven fissile‑fuel breeding remains primarily a scientific curiosity rather than a practical energy solution.