As its supply of Helium-3 (He-3) dwindles, the Pentagon’s Defense Threat Reduction Agency (DTRA) is seeking a new means of detecting nuclear-fueled explosives.

DTRA has awarded a $2.8 million contract to technologies solution firm Alion to develop a replacement technology for Helium-3 nuclear detection.

Threats such as dirty bombs combine radioactive material with conventional explosives.

Historically, the Department of Defense and other agencies have used He-3 to detect neutrons emanating from the aforementioned Special Nuclear Material (SNM), according to a release from Alion. However, due to its rareness as a non-naturally occurring substance, the He-3 is rapidly drying up.

Alion is currently developing an advanced detection system that uses boron-coated “straws,” which the company says are “literally bundles of thin copper tubes with a coating of boron, an abundant element.”

Current He-3 detectors are omnidirectional, so they can only alert users to the presence of neutrons. Under the contract, Alion will develop methods to make the boron-coated straw detector directional, so that a search team can pinpoint the location of the source of neutrons and thus react to threats more effectively.

Alion engineers will also focus on creating smaller detector and faster electronics, while attempting to reduce the technology’s overall production costs.