Year
1989
Abstract
Due to the 1979 accident at Three Mile Island Unit 2 (TMI-2), fuel material was transported through the reactor coolant system (RCS). As the Cleanup Program nears completion, the location and quantity of residual special nuclear material (SNM) remaining in different reactor components becomes important. One of the measurement methods being used at TMI-2 to quantify the amount of SNM is the well-known foil activation technique. Foil activation is a passive nondestructive method of assaying SNM. Copper (Cu-64) foils are being activated by neutrons generated from the residual SNM at TMI-2. The activity of these foils is being measured by two sodium iodide (Nal) detectors and an electronic coincidence system. The coincidence system is used to enhance the 511 keV gamma rays produced by positron ( /3+) emission of activated copper foils by suppressing the background radiation. Since the neutron emission rate from the residual fuel at TMI-2 is fairly well known, the amount of SNM can be calculated from the copper foil activation, provided there is proper calibration of foils to a known amount of neutron flux and a coincidence system to a 511 keV gamma source of known activity. The Pacific Northwest Laboratory independently performed foil activation measurements at TMI-2 in 1988. Their method was similiar to the present means.