CEA-List Develops Advanced Nuclear Detection Techniques to Combat Illicit Trafficking
Researchers at CEA-List, a technological research division of the French Alternative Energies and Atomic Energy Commission, are pioneering novel nuclear detection methods to enhance border security and counter illicit trafficking of radioactive and nuclear materials. The core innovation involves harnessing two specific physical phenomena: photoneutron emission and photofission.
Traditional radiation portal monitors (RPMs) at borders primarily detect gamma rays and neutrons emitted spontaneously by materials like uranium or plutonium. However, these systems have significant limitations. They can struggle with heavily shielded materials, where lead or other metals block spontaneous emissions, and they provide limited capability to identify the specific isotopic composition of a detected substance.
The CEA-List approach, developed within its Nuclear Measurement Laboratory, actively probes suspect materials. It uses a pulsed, high-energy photon (gamma-ray) beam to irradiate a container or object. This beam induces two key reactions in nuclear materials:
1. Photoneutron Emission: The photon beam knocks neutrons directly out of atomic nuclei.
2. Photofission: In heavy nuclei like uranium-238, the photon beam can trigger fission, splitting the nucleus and releasing additional neutrons and gamma rays.
The system then precisely measures the unique time signature and energy spectrum of the neutrons and gamma rays emitted in response to the pulsed beam. This "active interrogation" method offers two major advantages over passive RPMs. First, it can detect materials even through substantial shielding, as the powerful external beam penetrates the shield and activates the hidden nuclear core. Second, the specific delayed signals from photofission products act as a fingerprint, allowing analysts to not only detect but also identify the type of nuclear material present—crucial for distinguishing between legitimate medical isotopes and illicit weapons-grade substances.
This research positions active detection using photoneutrons and photofission as a powerful scientific tool for non-proliferation and security. The technology aims to provide customs and border agencies with a more reliable, informative, and evasion-resistant method for screening cargo, ultimately strengthening global safeguards against nuclear smuggling.