Advanced Portal Monitoring for Arms Control Treaty Verification

With the current global political landscape, the future of arms control treaties is highly uncertain, however it is imperative that the scientific community is prepared to meet the technological needs of future arms control treaty verification agreements. In this article, we discuss the potential role of portal monitoring within a warhead verification regime, and particularly the inclusion of additional sensor types (e.g. load cells) and more advanced analyses (e.g. correlated neutron analysis). By allowing for better discrimination between treaty accountable items and other non-treaty accountable sources, these more capable portal monitors may allow for continuity of knowledge (CoK) in more complex, realistic scenarios. However, more complex portal monitoring designs will also need to extend this complexity into considering information barriers, tamper prevention and indication, and other controls necessary to ensure authentication and certification demands of arms control technology can be met. Portal monitoring has long been identified as a useful tool to include within a treaty verification system, with attributes desirable to address CoK concerns, confirm movements (or absence of movement) of special nuclear material (SNM), or to confirm certain attributes about items moving past the portal[14]. Past research for arms control treaty verification utilizing portal monitor technology has focused on radiation detection only, utilizing gross-counting detectors that do not allow for high confidence isotope identification and quantification (but do offer an easier path to equipment certification). The Intermediate-range Nuclear Forces (INF) Treaty provides some historical precedence for the use of perimeter and portal monitoring in arms control, in which the “inspecting party [had] the right to establish continuous monitoring systems at the portal“, which would include “appropriate sensors at the exits” of sites producing treaty limited missiles[15].  In this article, we will consider both vehicle portal monitors, intended to be placed at boundaries to monitor the movement of treaty accountable items (TAIs) secured within transport vehicles, and in-facility ‘hallway’ portal monitors, intended to be placed within a facility to monitor the movement of TAIs. We will present several exemplar scenarios to show how advanced portal monitors could be used within an arms control treaty verification regime.