A proven system for verifying that apparent nuclear weapons slated to be dismantled contained true warheads could provide a key step toward the further reduction of nuclear arms.The system would achieve this verification while safeguarding classified information that could lead to nuclear proliferation. Scientists at Princeton University and the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) are developing the prototype for such a system, called a “zero-knowledge protocol,” that would verify the presence of warheads without collecting any classified information at all. “The goal is to prove with as high confidence as required that an object is a true nuclear warhead while learning nothing about the materials and design of the warhead itself,” said physicist Robert Goldston, a fusion researcher and former director of PPPL, and a professor of astrophysical sciences at Princeton. While numerous efforts have been made over the years to develop systems for verifying the actual content of warheads covered by disarmament treaties, no such methods are currently in use for treaty verification.
The system would compare a warhead to be inspected with a known true warhead to see if the weapons matched. This would be done by beaming high-energy neutrons into each warhead and recording how many neutrons passed through to detectors positioned on the other side. Neutrons that passed through would be added to those already “preloaded” into the detectors by the warheads’ owner and if the total number of neutrons were the same for each warhead, the weapons would be found to match. But different totals would show that the warhead being inspected was really a spoof. Prior to the test, the inspector would decide which preloaded detector would go with which warhead.
A project to evaluate this approach is under construction at PPPL.The project calls for firing high-energy neutrons at a non-nuclear target called a British Test Object that will serve as a proxy for warheads. Researchers will compare results of the tests by noting how many neutrons pass through the target to bubble detectors that Yale University is designing for the project.
If proven successful, dedicated inspection systems based on radiation measurements could help to advance disarmament talks beyond the New Strategic Arms Reduction Treaty (New START) between the United States and Russia, which runs from 2011 to 2021.