Solution of blank problems in 14-Mev. neutron activation analysis for trace oxygen

Abstract

ously described, the N G interference with TA was minimized by thermally decomposing the NG. The retention times of several of the most likely nitrated derivatives of resorcinol and 2-NDPA were measured. The relative retention times are shown in Table 11. As shown by these data, all of the components studied were separated from TA, DMS, resorcinol, and 2-NDPA or the compounds in question did not elute from the column.Precision Study. The precision study was conducted using extracts obtained from two different propellant formulations, 1 and 2. Because these propellants did not contain DMS, a known amount of this compound was added to the propellant 2 extracts. The recovery of the added DMS was then determined. A typical chromatogram for these propellant extracts is shown in Figure 1. The data obtained from the precision study are shown in Table 111. Two different propellant formulations were analyzed to emphasize any effects of different ratios of the components on the results. These data showed that the concentration of any one component did not influence the results of another component. The coefficient of variance for each of the two pro-pellants was essentially the same-Le., TA, 0.03%; DMS, 0.02%; resorcinol, 0.01 %; and 2-NDPA, 0.01 %. In addition, data in Table 111 show the close agreement obtained between the G C and present IR-TLC (4) methods, about *2% relative or less between all the components. Because the method would be applied to large numbers of samples, the precision calculations were based on peak height instead of the more accurate area measurements by triangulation to decrease the time required for calculation of the results.The results definitely indicated that NG was not a problem because low coefficient of variance for each component was obtained. These data were confirmed by analyzing samples with widely varying NG/TA and NG/stabilizer ratios as shown in Table IV. These results proved that the effect of NG on the stabilizers had been removed and, further, the interference of NG with TA had been eliminated.THE ACCURACY of trace oxygen determinations by 14-MeV neutron activation analysis can be seriously affected if the oxygen contribution from the container is significant. If the count from the blank is merely subtracted from the total sample-in-container count, errors as large as 100% may be introduced. Solutions by other workers (1-4) are specific to the individual systems being used and are not of general applicability.With a general purpose activation analysis facility, an attempt has been made to provide a generalized solution to the problem. In our previous approach (3, leak problems, associated with the encapsulation technique for loading steel samples in polyethylene containers under a nitrogen atmosphere, introduced imprecision in about 2 0 z of the experiments. The present technique gives consideration to the sample-in-container geometry and any attenuation effects which may arise during irradiation and counting. The application of this method does not presuppose the availability of...

Nucleonics

“…The use of fast neutrons for in vivo activation analysis has evolved from a bizarre curiosity to a widely accepted and practiced method during this period (44-, 45,143). The chronic uncertainties of 14-MeV neutron bombardment were exhaustively studied at the National Bureau of Standards; in particular, blank problems (140) and systematic errors (139) were investigated and a device proposed for high-precision analysis (127). Absolute determination of 14-MeV neutron yields, so important for intercomparison of facilities, was also evaluated (73).…”

Design parameter investigation of a cold-cathode Penning ion source for general laboratory applications

“…PIG ion sources have been used for a variety of applications, such as sputtering and evaporation of surfaces, electromagnetic separation of isotopes and fusion applications (Barnett et al 1953, Meyerand and Brown 1959, Roth 1995, Loeb 2005. Another possible application is in a sealed-tube neutron generator (Nargolwalla and Przybylowicz 1973). In fact, Penning applied his 1 Propulsion Research Engineer, now Assistant Professor of Aerospace Engineering, Missouri University of Science and Technology, Rolla, MO, USA.…”