Scintillator reduction

Fig. 3. X-ray diffractogram of Class-F bituminous coal fly ash. Analytical conditions diffraction data were collected using a Philips X-ray powder diffractometer (45 kV/30-40 mA CuKa theta-compensating variable divergence slit diffracted-beam graphite monochromator scintillation detector) automated with an MDI/Radix Databox. The scan parameters were typically 0.02° step size for 1 s count times over a range of 5-60° 2-theta. All data were analysed and displayed using a data reduction and display code (JADE) from Materials Data Inc., livermore, CA.

The larger square p scintillators are viewed edgewise by 1-1/2-inch diameter 10-stage multiplier phototubes and used in 2-inch diameter wells of 8-inch X 8-inch Nal(Tl) crystals. The larger scintillators are used for sample sizes up to several hundred milligrams. Figure 2 illustrates the reduction in background achieved by the p coincidence requirement. 

Low-Level Waste Low-level waste (LLW) consists of contaminated dry trash, paper, plastics, protective clothing, organic liquids such as liquid scintillation samples, and the like. LLW is produced by any facility that handles radioactive materials such as nuclear power plants, medical facilities, colleges, and so forth. In the United States, commercial LLW is sent to one of three disposal sites (Barnwell, South Carolina, Richland, Washington, and Clive, Utah). Due to the limited size of these sites (and similar disposal sites through the world) and steeply escalating costs for waste disposal, the primary goal of LLW treatment prior to disposal is volume reduction, either by incineration or compaction, followed... 

Radiation scattered from the inspection point, after passing thru the detector collimator, impinges on scintillators which convert this incident radiation to visible light. The visible light, in turn, is sensed by an array of photomultiplier tubes that generate electrical outputs which are directed to computers for data reduction and analysis. These signals are proportional to the density of the HE in the shell... 

The conditions for Pu reduction and elution were examined in detail, and a variety of reducing agents were tested.82 A flow system with an on-line scintillation detector was used to show the elution behavior in detail under well-controlled flow conditions. It was found that reduction and elution with hydroquinone was slow, resulting in broad tailing peaks and incomplete reduction. Some Pu remained in the Pu(IV) state and could be eluted with a complexant on completion of the reductant/HCl elution step. However, by choosing other reductants, rapid reduction and clean elution as a sharp peak could be obtained. These results are shown in Figure 9.14. 

The same data collection and reduction techniques are commonly used by the same workers for many different polymers. Therefore, data for these other polymers may contain errors on a similar scale, but that the errors have usually, but not always, gone undetected (8). If more than 500 reflections are observed, from single crystals of simple molecules, recognizable electron-density distributions have been derived from visually estimated data classified only a "weak", "medium" or "strong". The calculation of the structure becomes more sensitive to the accuracy of the intensity data as the number of data points approaches the number of variables in the structure. One problem encountered in crystal structure analyses of fibrous polymers is that of a very limited number of reflections (low data to parameter ratio). In addition, fibrous polymers usually scatter x-rays too weakly to be accurately measured by ionization or scintillation counter techniques. Therefore, the need for a critical study of the photographic techniques of obtaining accurate diffraction intensities is paramount. 

Coincidence techniques have also been used for Compton interference reduction in the use of large volume Ge(Li) detectors together with plastic scintillator anticoincidence shields 70), In some cases it might be desirable to use the coincidence electronics to gate the multichannel analyzer to accept only non-coincident pulses. In 14 MeV neutron activation procedures the annihilation radiation resulting from the decay of 13N produced indirectly from the carbon in the plastic irradiation unit may be discriminated against by gating the analyzer to accept only non-coincident events. 

Reduction with tritiated NaBH4 (NaB3H4), followed by analysis of the radioactive sugar alcohols by paper chromatography and liquid scintillation counting. 

Figure 1.1 Schematic of a representative enzymatic assay. The reaction mixture is prepared (Mix Preparation) and the reaction can be started (Initiation) by the addition of the enzyme. During the reaction (Incubation), samples are removed at intervals labeled h, t2, and r3, and the reaction is stopped (Termination) by inactivating the enzyme. The incubation mixture is fractionated (the illustration shows a traditional chromatographic column), and the product is isolated from the substrate (Separation). In this assay, a radiochemical was used as the substrate and therefore the amount of product that formed is determined by its collection, the addition of scintillation fluid, and the measurement of radioactivity by scintillation counting (cpm Detection). The progress of the reaction is given by the amount of radioactive product recovered (Data Reduction).

Transient scintillating scotomata have been observed in the visual fields of both eyes in nine patients receiving paclitaxel infusions in doses of 175 and 225 mg/m (35). Involvement of the optic nerve was confirmed, and this is likely to have been related to optic nerve conduction abnormalities associated with the neurological effects of paclitaxel. The abnormalities were not progressive and there was some degree of recovery, although one patient sustained a permanent reduction in vision. 

The ability of high-temperature ionic solvents to dissolve various substances (e.g. metals or their oxides) is considered among their most important characteristics. In the case of scintillation, single crystals based on alkali-metal halides, some halides-dopants (Til, CeX3, etc.), are available as admixtures since they create levels in the forbidden zone which are responsible for the scintillation. In contrast, oxygen-containing admixtures are harmful since their existence in the crystals causes a considerable reduction in their light-yield, radiation resistance, etc. 

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