Researchers at Lawrence Livermore National Laboratory (LLNL) have developed an inexpensive, nonhazardous plastic for detecting the neutron signatures of nuclear weapons–usable materials. Capable of efficiently distinguishing neutrons from gamma rays, the new polymer scintillator is expected to make practical for the first time handheld radiation detectors for international inspections of uranium enrichment plants and nuclear power reactors. The material could also replace or supplement existing neutron detectors in radiation portal monitors that use scarce helium-3. (See PHYSICS TODAY, May 2011, page 20.)
Although plastic scintillators have long been used to detect ionizing radiation, until now scientists did not believe it possible to formulate a plastic that could discriminate neutrons from the far more plentiful gamma rays. Unlike 3He detectors, which pick up thermal, or low-energy, neutrons, the polymer developed at LLNL scintillates with high-energy neutrons, the type emitted by the fissile isotopes uranium-235 and plutonium-239. David Beach, program...
