Ensuring compliance with the moratorium on nuclear testing, observed by all nations but North Korea, is the responsibility of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). But its global international monitoring system (IMS) is sometimes confounded by the production of the medical isotope precursor molybdenum-99, which has a nearly identical radioactive signature to nuclear explosions. The problem is worsening as demand for technetium-99m, the most widely used medical radioisotope and the offspring of 99Mo, continues to grow.
The surest radioactive indicator that a nuclear test has recently taken place is the presence of radioisotopes of xenon in the atmosphere, says Ted Bowyer, a nonproliferation program manager at Pacific Northwest National Laboratory (PNNL). As a noble gas, xenon doesn’t interact with the environment and is more difficult to contain underground than other particulate fission products.
Home to the largest nuclear nonproliferation program in the Department of Energy’s national lab complex, PNNL...