Helium-3 for Neutron Detection

Helium-3 proportional counters are a workhorse neutron detector for security and science; the isotope's huge capture cross-section makes it ideal.

The detector of choice for neutrons

Helium-3 is one of the best materials for detecting neutrons. It has a very large thermal-neutron capture cross-section through the reaction ³He(n,p)³H, which converts a neutron into a proton and a tritium nucleus. Those charged products ionize the gas and produce a clean, easily counted electrical pulse.

Packaged as a pressurized proportional counter, helium-3 detectors are efficient, gamma-insensitive, and stable, which is why they became the standard for radiation-portal monitors at borders and ports, for nuclear-material safeguards, and for neutron-scattering instruments in research.

The supply crisis this created

When large-scale deployment of neutron portal monitors was undertaken for security, demand for helium-3 spiked far above the tritium-decay supply, causing a well-documented shortage. The episode showed that a single application can exhaust the world's helium-3 and drove a search for alternatives and for new supply.

Hyperion as a supply source

• ³He counters remain preferred where performance matters most
• Safeguards and security demand steady, assured supply
• A breeder foundry adds new helium-3 at kg/yr scale
• Detection-grade purity requirements are addressed in processing

Supplying detection-grade helium-3 is a strategic-availability argument, described in physical and supply terms only, with no commercial claim on this page.

This page describes a design-and-simulation study, not a built machine. Construction begins Q2 2027; first-of-a-kind (FOAK) first tritium is targeted near 2030. No net-gain claim is made before FOAK.