Year
2012
Abstract
In the late 1980s, the International Atomic Energy Agency (IAEA) began to deploy unattended and remote monitoring systems to allow for state of the art automated monitoring of nuclear facilities. This supplemented and strengthened onsite inspections to ensure nuclear materials were not diverted for weaponization or other purposes unknown. These systems are permanently installed in a nuclear facility and are expected to be robust and reliable continuously for periods of approximately 10–15 years or more. At the same time, considering that the State is a potential adversary, the IAEA must assure itself that the data collected are authentic. A layered approach has been used to both deter and detect intentional tampering. This employs the use of both hardware and software approaches including: secure sealed housings for system components and sensors, tamper-indicating conduits, digital encryption and authentication, and data analysis for tamper anomalies. While the information-gathering components are locked in secure cabinets, the radiation sensor components (i.e., neutron and gamma detectors) are in secure housings, but are located throughout the plant and use cabling to provide power and collect data over long distances. In some cases, there are kilometers of cabling in cable trays as well as cables running through wall penetrations. The detection of sensor tampering in high radiation areas is particularly challenging due to the high probability of single event upsets and component burnout on integrated circuits normally used to digitize and authenticate sensor signals. To improve on present capabilities we present a method and an apparatus developed at Idaho National Laboratory (INL) that demonstrates a novel approach for the detection of sensor tampering. This method is based on the detailed spectral analysis of the sensor noise floor after the sensor signal is received back at the secure cabinet. The apparatus consists of a 5.3 cm x 6.6 cm (2.1” x 2.6”) electronic circuit board containing all signal conditioning and processing components and a laptop computer running an application that acquires and stores the analysis results. The sensors do not require any modification and are remotely located in their normal high radiation zones. The apparatus interfaces with the sensor signal conductors using a simple pass-through connector at the normal sensor electronics interface package located in the already secure cabinet. The apparatus does not require hardening against the effects of radiation due to its location. We presented the apparatus design, the analysis method, and the test results as applied to tamper detection using three 3He neutron sensors and two solid state gamma sensors designed and built for safeguards monitoring. This work was supported by the Next Generation Safeguards Initiative (NGSI), Office of Nonproliferation and International Security (NIS), National Nuclear Security Administration (NNSA).