Year
1979
Abstract
Portal monitors (PM) provide one of the most effective detection mechanisms at access portals of nuclear facilities. They are especially useful against covert theft of special nuclear materials (SNM). This paper reports the results of a study of generic PMs that demonstrated that properly designed PMs can be very effective in detecting plutonium, particularly when radiation from fission product impurities in recycled plutonium are taken into account. There are many parameters that affect and determine the performance of PMs. These are SNM related, PM related, and finally parameters that relate to adversary tactics (e.g., concealable shielding material, tampering with maintenance and calibration, artificial variation in background, etc.). Many of these parameters were incorporated in a thorough analysis of PM effectiveness and vulnerability. The results are expressed in terms of the minimum detectable amount of SNM for different adversary tactics. The results demonstrate that a well designed PM is an extremely efftive and robust barrier against unauthorized removal of 239pu and 233u. The sensitivity to detection of 2^9pu is augmented, typically close to an order of magnitude, if the presence of fission product traces (with levels of ~2 pCi Ru/g Pu) is taken into account. Indeed, any \"labeling\" of the Pu by allowing certain amounts of fission products to contaminate the Pu product will assure the detectability of small amounts of Pu moving through the portal.