13 research outputs found
Wavelength Shifters for Water Cherenkov Detectors
The light yield of a water-based Cherenkov detector can be significantly
improved by adding a wavelength shifter. Wavelength shifter (WLS) molecules
absorb ultraviolet photons and re-emit them at longer wavelengths where typical
photomultiplier tubes are more sensitive. In this study, several wavelength
shifter compounds are tested for possible deployment in the Sudbury Neutrino
Observatory (SNO). Test results on optical properties and chemical
compatibility for a few WLS candidates are reported; together with timing and
gain measurements. A Monte Carlo simulation of the SNO detector response is
used to estimate the total light gain with WLS. Finally, a cosmic ray Cherenkov
detector was built to investigate the optical properties of WLS.Comment: 13 pages, 3 figure
Five-Column Chromatography Separation for Simultaneous Determination of Hard-to-Detect Radionuclides in Water and Swipe Samples
There
is a growing demand for the rapid determination of hard-to-detect
radionuclides in environmental and biological samples for environmental
monitoring, radiological protection, and nuclear forensic reasons.
A new method using five-column chromatography separation has been
developed for the simultaneous determination of Pu, Np, Th, U, Am,
Cm, Pm, Y, and Sr isotopes, as well as iron-55, by inductively coupled
mass spectrometry (ICPMS), Ī± spectrometry, CĢerenkov and
liquid scintillation (LS) counting. Spiked swipe and water samples
as well as proficient testing water standards were analyzed to validate
the separation procedure, and the results are in good agreement with
the expected values. The method provides quick sample turnaround time
and high analysis throughput with low analysis cost. The flexibility
of the method also allows for its easy adaptation to various emergency
and routine radioassays
Geochemistry of rare-earth elements and its significance in the study of climatic and environmental change in Barrow, Arctic Alaska
Geochemical characteristics of rare earth elements (REE) and sedimentary features were studied in the borehole 96-7-1 from Elson Lagoon to Barrow, Arctic Alaska. The results show that total contents of REE (Ī£REE) are lower, suggesting that physical weathering is dominate, therefore, concentrations of rare earth elements are lower in the paleosediment environment. The chondrite-normalized distribution patterns of REEs are characterized by light REE (LREE) enrichment and Eu depletion with the terrestrial sedimentary rock as the parent materials. In comparison with the borecore AB-67 in Elson Lagoon, the main conclusions for climatic and environmental changes are similar: before 1740 A. D., it was cold and dry with terrestrial properties, but the comparatively warming around 1400 A. D. and 1550 A. D.; after 1740 A. D., it became warming, or markedly after 1821 A. D.; but it was cold around 1890 A. D. From 1904 A. D., it got warm again, but it was relatively cold around 1971 A. D.
Determination of Atto- to Femtogram Levels of Americium and Curium Isotopes in Large-Volume Urine Samples by Compact Accelerator Mass Spectrometry
Ultralow level analysis of actinides
in urine samples may be required
for dose assessment in the event of internal exposures to these radionuclides
at nuclear facilities and nuclear power plants. A new bioassay method
for analysis of sub-femtogram levels of Am and Cm in large-volume
urine samples was developed. Americium and curium were co-precipitated
with hydrous titanium oxide from the urine matrix and purified by
column chromatography separation. After target preparation using mixed
titanium/iron oxides, the final sample was measured by compact accelerator
mass spectrometry. Urine samples spiked with known quantities of Am
and Cm isotopes in the range of attogram to femtogram levels were
measured for method evaluation. The results are in good agreement
with the expected values, demonstrating the feasibility of compact
accelerator mass spectrometry (AMS) for the determination of minor
actinides at the levels of attogram/liter in urine samples to meet
stringent sensitivity requirements for internal dosimetry assessment
Accurate Determination of Plutonium in Soil by Tandem Quadrupole ICP-MS with Different Sample Preparation Methods
In this work, three commonly used digestion techniques, such as acid leaching with 8 M HNO3, aqua regia and lithium metaborate fusion, were employed to extract Pu from different types of soil samples widely found across China, and to establish the influence of the major interference elements (U, Hg, Pb, Tl, and Bi) on the accurate measurement of Pu by tandem quadrupole ICP-MS. The three sample digestion techniques yielded good results for the analysis of Pu isotopes originating from global atmospheric fallout. The U and Pb contributions to m/z=239 (2.38 and 0.3 cps) in samples digested by the fusion method using AGMP-1M resin were higher than those digested by the acid leaching methods (0.55 cps for U and < 0.03 cps for Pb), which implies that additional purification with TEVA resin would be required for low-level Pu determination in soil samples. By taking advantage of tandem quadrupole ICP-MS in the NH3/He mode, the count rates of Hg, Tl and Bi at m/z=239 (<0.01 cps) in the samples purified by using AGMP-1M resin and/or TEVA resin were found to be negligible for the different sample digestion methods
Canada's efforts in developing capabilities in radiological population monitoring
Population monitoring is an important component of radiological and nuclear emergency preparedness and response. Since 2002, Canada has been investing in developing national capabilities in radiological population monitoring. This paper summarizes Canada's efforts in developing methods and techniques in biological dosimetry and in vivo and in vitro bioassay techniques. There are still many gaps to fill that require further efforts. Integration of different monitoring methods and techniques in order to have the best assessment of radiation dose to support medical management and integration of Canada's efforts with international efforts are recommended
Method of Polonium Source Preparation Using Tellurium Microprecipitation for Alpha Spectrometry
A thin-layer
source for the counting of polonium isotopes by alpha
spectrometry can be rapidly prepared using microprecipitation with
tellurium. Polonium was first coprecipitated with the reduction of
tellurium by stannous chloride, followed by microfiltration onto a
membrane filter for counting. This microprecipitation method is faster,
cheaper, and more convenient than the traditional spontaneous deposition
method, with an excellent Po recovery (>90%) under optimal conditions.
The influences of several experimental parameters, including TeĀ(IV)
quantity, reaction time, and HCl molarity, were examined to determine
the optimal conditions for Te microprecipitation. The decontamination
factors of potential interferences from various radionuclides (Ra,
Th, U, Pu, Am) for the counting of long-lived polonium isotopes (<sup>208</sup>Po, <sup>209</sup>Po, and <sup>210</sup>Po) were also evaluated,
and the results confirmed a good selectivity on polonium by this microprecipitation
method. Due to its strong resistance to high acidity up to 12 M HCl,
the method would be particularly suitable for rapid determination
of <sup>210</sup>Po in acid leaching solution of solid samples