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In-situ passive monitoring of alpha-emitting radionuclides

Description: Electrets and alpha-track detectors (ATDs) show considerable promise for inexpensive passive monitoring of alpha contamination on man-made surfaces or in soil. At the stringent Department of Energy (DOE) limit of 100 dpm/100 cm{sup 2}, the electret voltage drops 10 V in about 4 hours; 10 V is readily quantifiable since any reading of electret voltage is accurate to {plus_minus}l V. An analogous signal-to-noise ratio for the ATDs is obtained after an exposure time of about 3 hours. The alpha-track registration efficiency for CR-39 type plastic is about 70% with the background track density averaging 13 tracks/cm{sup 2}. Measurements for intercomparison were performed with electrets, ATDS, and conventional survey meters on a contaminated vinyl floor and a concrete loading dock. Agreement between different types of detector readings was satisfactory. Surface soil measurements, using an exposure time of 1 day, can detect contamination of just a few pCi/g. Preliminary horizontal mapping was conducted within and at the boundary of a plutonium contaminated area at the DOE Nevada Test Site (NTS). The means of making vertical profiles of subsurface contamination are being explored. Some problems that have to be overcome involve interference from natural radon, variable soil moisture, preventing moisture condensation, wide extremes of ambient temperature and wind-driven shifting of soil.
Date: June 1, 1993
Creator: Gammage, R. B.; DePriest, J. C.; Murray, M. E.; Wheeler, R. V.; Salasky, M. R.; Dempsey, J. C. et al.
Partner: UNT Libraries Government Documents Department

Multiple Input Microcantilever Sensor with Capacitive Readout

Description: A surface-micromachined MEMS process has been used to demonstrate multiple-input chemical sensing using selectively coated cantilever arrays. Combined hydrogen and mercury-vapor detection was achieved with a palm-sized, self-powered module with spread-spectrum telemetry reporting.
Date: March 11, 1999
Creator: Britton, C.L., Jr.; Brown, G.M.; Bryan, W.L.; Clonts, L.G.; DePriest, J.C.; Emergy, M.S. et al.
Partner: UNT Libraries Government Documents Department

Comparative study of combustion product emissions of Pakistani coal briquettes and traditional Pakistani domestic fuels

Description: A comparative emissions study was conducted on combustion products of various solid domestic cooking fuels; the objective was to compare relative levels of organic and inorganic toxic emissions from traditional Pakistani fuels (wood, wood charcoal, and dried animal dung) with manufactured low-rank coal briquettes (Lakhra and Sor- Range coals) under conditions simulating domestic cooking. A small combustion shed 12 m[sup 3] internal volume, air exchange rate 14 h[sup [minus]1] was used to simulate south Asian cooking rooms. 200-g charges of the various fuels were ignited in an Angethi stove located inside the shed, then combusted to completion; effluents from this combustion were monitored as a function of time. Measurements were made of respirable particulates, volatile and semi-volatile organics, CO, SO[sub 2], and NO[sub x]. Overall it appears that emissions from coal briquettes containing combustion amendments (slaked lime, clay, and potassium nitrate oxidizer) are no greater than emissions from traditional fuels, and in some cases are significantly lower; generally, emissions are highest for all fuels in the early stages of combustion.
Date: October 1, 1992
Creator: Wachter, E.A.; Gammage, R.B.; Haas, J.W. III; Wilson, D.L. (Oak Ridge National Lab., TN (United States)); DePriest, J.C.; Wade, J. (Midwest Technical, Inc., Oak Ridge, TN (United States)) et al.
Partner: UNT Libraries Government Documents Department