[Paper Review] Very Big Accelerators as Energy Producers

Robert R. Wilson|arXiv (Cornell University)|Jul 29, 2010

Particle accelerators and beam dynamics3 citations

TL;DR

This paper proposes that very high-energy proton accelerators, such as the Fermilab Energy Doubler/Saver, could serve as net energy producers by using 1000 GeV protons to generate neutrons in uranium-238, which then produce plutonium-239 through neutron capture. The fission of this plutonium releases significantly more energy than the accelerator consumes, with calculations showing a break-even intensity of ~1.2×10¹³ protons/second at 1000 GeV, making such a system potentially energy-positive under optimized conditions.

ABSTRACT

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.

Motivation & Objective

• To investigate whether high-energy proton accelerators could function as net energy producers by leveraging neutron multiplication and plutonium fission.
• To evaluate the feasibility of using accelerator-driven systems for energy production, particularly with superconducting technology.
• To determine the minimum proton intensity required for net energy gain in such a system.
• To explore design optimizations—such as back-to-back magnet rings and improved beam dynamics—for enhancing efficiency and power output.
• To assess the role of electromagnetic shower components and fission energy recovery in improving overall energy yield.

Proposed method

• Modeling the energy deposition in a uranium-238 target using a proportionality constant 'a' (~60 neutrons per GeV) to estimate neutron yield per proton.
• Using the equation P = 0.2aNE − P₀ − bNE to calculate net power output, where 0.2 GeV is the energy per fission, P₀ is idle power, and b is RF inefficiency (≈2, potentially reducible to 1.5).
• Applying beam dynamics principles: beam emittance improves with energy, enabling smaller ring apertures and reduced refrigeration costs.
• Simulating nuclear shower development via computer modeling (by A. VanGinneken) to track energy partitioning among hadronic showers, electromagnetic components, and fission events.
• Proposing a dual-ring configuration with back-to-back superconducting magnets to allow continuous operation and double beam intensity.
• Evaluating target design options, including slurry-based targets with steam-driven piston cycles or conventional heat transfer, to manage thermal loads from high-intensity pulses.

Experimental results

Research questions

• RQ1 Can a high-energy proton accelerator produce more energy from plutonium fission than it consumes in operation?
• RQ2 What is the minimum proton intensity required for net energy gain in an accelerator-driven system?
• RQ3 How does increasing proton energy affect the efficiency of neutron production and subsequent energy yield?
• RQ4 To what extent can beam dynamics and magnet ring design reduce refrigeration and power costs?
• RQ5 Can back-to-back magnet rings and improved injection techniques significantly enhance usable beam intensity and system efficiency?

Key findings

• The break-even proton intensity N₀ for the Fermilab Energy Doubler at 1000 GeV is approximately 1.2×10¹³ protons per second, which is about 20 times the expected operational intensity but potentially achievable through pulsing or stacking.
• At 1000 GeV, each 10¹³ protons produce about 20 MW of fission energy, with a total of 62,000 Pu-239 nuclei generated per proton.
• The fraction of incident energy recovered as usable energy decreases with increasing proton energy due to a rising electromagnetic shower component, though this effect is partially offset by higher neutron yield.
• Including energy from both fission and electromagnetic showers, the total recoverable energy per 10¹³ protons reaches 20 MW at 1000 GeV, significantly exceeding the 0.2 MW beam power.
• Using undepleted uranium or slightly enriched fuel could reduce the required break-even intensity by a factor of ten, potentially making the system viable with current accelerator capabilities.
• The proposed dual-ring configuration could double beam intensity and improve utilization of the injection system, enhancing overall efficiency.