Measurement of radionuclides using ion chromatography and flow-cell scintillation counting with pulse shape discrimination

A project has been initiated at Clemson Univ. to develop a HPLC/flow- cell system for analysis of non-gamma emitting radionuclides in environmental samples; an important component is development of a low background flow-cell detector that counts alpha and beta particles separately through pulse shape discrimination. Objective of the work presented here is to provide preliminary results of an evaluation of the following scintillators: CaF{sub 2}:Eu, scintillating glass, and BaF{sub 2}. Slightly acidic aqueous solutions of the alpha emitter {sup 233}U and the beta emitter {sup 45}Ca were used. Detection efficiencies and minimum detectable activities were determined

Measurement of radionuclides using ion chromatography and flow-cell scintillation counting with pulse shape discrimination

Principal conclusions are: CsI(Tl) provides sufficient pulse shape discrimination for use in the flow-cell detector. However, an improved method of coating is needed to extend the useful life of a detection cell. Of the activation/fission products investigated, only the co-elution of {sup 137}Cs and {sup 63}Ni produced a radiological interference. Tritium (and presumably other non-ionic radioisotopes) can be separated during the loading of the solution onto the pre- concentration column. Natural U (and/or decay products) produced a radiological interference with {sup 90}Sr. This is a potential problem. No potential radiological interferences were observed with {sup 223}Th. Chemical interferences were observed to some degree for all the chemicals tested except for the chloride solutions, NaCl and KCl, and the sulfate solution, Na{sub 2}SO{sub 4}. The specific interference effects were decreased detection efficiencies and changes in peak elution times. The NEL`s (non-observable effects loadings) are tentative targets for development of sample processing protocols, which is the next phase of the work

Development of a scintillation flow-cell detection system for environmental restoration and waste management applications

A flow-cell detection system was developed utilizing a coincidence circuit and tested with BaF{sub 2}, CaF{sub 2}:Eu and scintillating glass. The coincidence detection system reduced the background from {approximately}200 cps to {approximately}0.5 cps. The detection efficiencies for these cells ranged from 0.38 to 0.66 for {sup 45}Ca beta particles (E{sub max} = 0.257 MeV) and from 0.45 to 0.52 for {sup 233}U alpha particles (E{sub {alpha}} = 4.8 MeV). The minimum detectable activity was calculated for a 30 s count time and determined to be in the range of 1-2 Bq

Monte Carlo Optimization of Depth-of-Interaction Resolution in PET Crystals

The light distribution along one edge of a PET scintillation crystal was investigated with a Monte Carlo simulation. This position-dependent light can be used to measure the 511 keV photon interaction position in the crystal on an event by event basis, thus reducing radial elongation. The expected full width at half maximum (FWHM) of the light distribution on the 3 {times} 30 mm{sup 2} surface of a 3 {times} 10 {times} 30 mm{sup 3} bismuth germanate (BGO) crystal surrounded by a diffuse reflector was determined to be 3.0 mm. This light distribution does not change as the width (originally 3 mm) is varied from 1 to 6 mm, but decreases monotonically from 3.0 to 1.8 mm FWHM as the height (originally 10 mm) is reduced to 3 mm. Other geometrical modifications were simulated, including numerous corner reflectors on the opposing 3 {times} 30 mm{sup 2} surface, which reduced the FWHM to 2.4 mm. The response of a dual wedge photodiode combined with the predicted light distribution for the 3 {times} 10 {times} 30 mm{sup 3} BGO simulation crystal results in an expected depth of interaction resolution of 7.5 mm FWHM