Toward a Secure Inspection System for Nuclear Warhead Verification Without Information Barrier

We previously proposed an approach to nuclear warhead verification envisioning an inspection system that a priori avoids detection of sensitive information, using a so-called zero-knowledge protocol. Under such a protocol, the host can prove to an inspector that a warhead is authentic without revealing anything about its materials or design. The challenge remains, however, to demonstrate a practical implementation of such a system that can detect relevant violations and avoids even the possibility of snooping on electronic measurements as they are made. In this article, we examine the use of superheated drop (or “bubble”) detectors to detect neutrons from active interrogation of an unclassified test object with 14.1-MeV neutrons. Zero-knowledge is achieved by the host pre-loading individual detectors so that they are “topped up” by the measurement itself to a previously agreed-upon, unclassified reference value. The required preloads are determined by the host prior to the inspection, but remain unknown to the inspector. The viability of the method is examined with MCNP5 Monte Carlo neutron transport calculations modeling the experimental setup, an investigation of a diversion scenario, and a mathematical analysis of the detected data.