Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Spectrometry, Gamma”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1998

The significance of variations in the angular correction factor in in situ gamma spectrometry.

In situ gamma spectrometry is a powerful method of assessing radioactive contamination in soil. The most widely adopted calibration methodology relates the overall sensitivity of the detector system to the product of three calibration factors: (a) the flux at the detector per unit activity in the ground phi/S(A), (b) the detected count-rate per unit flux incident normally at the detector N0/phi and (c) a correction factor to take into account the angular non-uniformity in response of the detector (Nf/N0). The dependence of the latter factor on the activity distribution with soil depth is generally neglected despite the lack of published evidence to support this. By (i) modelling and (ii) use of published experimental profiles, this work examines the range of Nf/N0 values likely to be encountered in the field. It was found that the use of a fixed angular correction factor is justified given that the maximum errors in the derived activity concentration do not exceed 5% and are far outweighed by other uncertainties.

Calibration↗
PubMed1997

Data quality objectives for surface-soil cleanup operation using in situ gamma spectrometry for concentration measurements.

In situ gamma spectrometry is an efficient method for monitoring the progress of cleanup activities for radioactive contaminants in surface soil and for evaluating the attainment of cleanup standards. However, desired data precision and accuracy must be specified for such a detection system prior to the operation to ensure that the level of uncertainty associated with the concentration measurements is acceptable. A method for developing data quality objectives is described in this paper for in situ gamma spectrometry to achieve numerical goals for data precision and accuracy for cleanup operations. Concentration measurement for a radionuclide at its cleanup level must have a precision commensurate with the importance of cleanup decisions. The 95% lower limit of detection of the system is suggested to be about one tenth the expected system response at the cleanup level. The count time required to achieve the preferred 95% lower limit of detection, and hence the desired precision, can then be determined. The accuracy error arises from the overall calibration factor, which relates the detector responses (e.g., count rate) to physical quantities of interest (e.g., radionuclide soil concentration). The major source of error for the calibration factor using in situ gamma spectrometry is the misidentification of the type of the depth profile of radionuclide concentration in soil. If surrogate radionuclides are used, such as 241Am for plutonium, the variation in the concentration ratio would be another significant source of error. Soil sampling programs performed prior to a cleanup operation will greatly reduce the accuracy error for an in situ detection system, and the analysis of system errors may determine the degree of sampling required. The planning of such a program is discussed in the study. Uncertainty analysis using a Latin Hypercube sampling technique for the calibration factor is also demonstrated. The quantitative result of the uncertainty analysis is useful for determining a nuclide's maximum peak count rate using gamma spectrum that ensures the attainment of the cleanup standard for that nuclide with a pre-specified confidence level (e.g., 95%). The cleanup operation of 239,240Pu in surface soil in the safety shot areas at the Nevada Test Site serves as an example to illustrate the data quality objectives development.

Americium↗
PubMed2000

Low level gamma spectrometry by beta-gamma coincidence

A beta-gamma coincidence system consisting of a 2pi plastic beta detector and a Ge(Li) detector, is described. Such a system allows for a drastic reduction of background (approximately 70 times) as well as of Minimum Detectable Activity (approximately 7 times). An integral background (50-1500 keV) of less than 0.1 cps is obtained. The difficulty of the method, otherwise simple and inexpensive, is the precise determination of beta detector efficiency.

Journal Article↗
PubMed2000

Use of gamma-spectrometry for simultaneous determination of 210Pb, 73As, 109Cd, 203Hg and 59Fe distribution and excretion in rats at low doses.

gamma-Spectrometry permits the identification and quantification of different gamma-isotopes in the same aliquot. To estimate the sensitivity and discriminative power of a comparably small and inexpensive 8% germanium detector, we determined the detection limits for simultaneously applied 210Pb, 73As, 109Cd, 203Hg and 59Fe. The concentration of Fe and of each of the four potential environmental contaminants was determined in aliquots from all organs and tissues 10 days after simultaneous i.v. administration (2 micromol/kg body weight) to adult and growing iron-deficient and iron-adequate rats. Relating these values to the total size of each organ permitted to derive a whole body distribution pattern for all five isotopes in each individual animal. Cumulative renal and faecal excretion values were determined during the 10 day distribution period to calculate the half-lives for both excretory pathways for all five isotopes simultaneously. Distribution and excretion values corresponded well to literature data. Extrapolation of the results showed that the detector would be sensitive enough to discriminate and quantify the five metals at human dietary exposure levels. The results recommend to use gamma-spectrometry to investigate kinetic aspects of interactions between toxic and essential trace metals, because the method reduces the number of required animals drastically.

Animals↗
PubMed1989

Measurement of natural radioactivity levels in Indian foodstuffs by gamma spectrometry.

Measurements of natural radioisotopes present in some of the foodstuffs which form the main components of the composite Indian diet are presented. Assessment of daily intake of these natural radionuclides has been made on the basis of the average daily intake of these food-items by the population of Bombay and its environment. The content of 40K, 226Ra and 228Th radioactivity varies from 45.9 to 649.0 Bq/kg, 0.01 to 1.16 Bq/kg and 0.02 to 1.26 Bq/kg, respectively. The average daily intakes of 40K, 226Ra and 228Th have been estimated as 105.6, 0.17 and 0.18 Bq d(-1), respectively for the period 1970-1982.

Eating↗
PubMed2001

Self-absorption correction for gamma spectrometry of powdered milk samples using Marinelli beaker.

Self-absorption was measured for the activity calculation of the 1460.8 and 2614.47 keV lines of the 40K and the 208Tl, respectively, in powdered milk samples. Five Marinelli beakers were prepared with powdered milk in different degrees of compaction and the spectra were measured with an HPGe detector. The detection efficiency versus density was obtained and the self-absorption correction factors versus density were calculated for powdered milk. The results obtained show that this factor must be considered in the calculations of activities.

Animals↗
PubMed1996

An intercomparison of gamma-spectrometry on two samples of biological origin by eight laboratories in four countries.

This report gives details of the first inter-laboratory comparison of gamma-spectrometry to be run within SPERA, the South Pacific Environmental Radioactivity Association since its inauguration in 1991. Laboratories in Australia, Chile, French Polynesia and New Zealand participated in the exercise. Two 'unknown' samples of biological origin were analysed. The first was a sample of milk powder derived from IAEA reference material. This sample provided an assessment of overall accuracy of 134Cs, 137Cs and 40K determinations. The second sample consisted of dried fish flesh including natural 40K and spiked with a mixed nuclide solution containing 210Pb, 109Cd, 54Mn, 60Co and trace 133Ba. Together the samples gave information on analytical precision over a range of energies and activities. When the results were compared with the recommended values and confidence intervals of the IAEA reference material, the overall accuracy of the gamma-spectrometry analytical procedures was found to be good. The average mean values for combined laboratory data fell within the recommended value ranges for each isotope. Ninety percent of the individual laboratory isotope mean values were within two standard errors of the 95% confidence interval of the standard, 75% were within 1 s.e., and 33% of the analyses fell within the confidence interval. Technical precision was also adequate with the overall errors being of the same magnitude as that of the reference material values for each isotope with relative standard deviations of 5-10%. There was a tendency for standard deviations of the combined results to be larger than those reported or derived from individual laboratory results by a factor between 1.2-5.6. This result suggested an under-estimate of systematic errors within individual laboratories. The largest sources of error were derived from reporting and calculation of results which gave a 16% gross error rate.

Animals↗
PubMed2001

Extraction of full absorption peaks in airborne gamma-spectrometry by filtering techniques coupled with a study of the derivatives. Comparison with the window method.

In this paper, an adaptation of a spectral profile analysis method, currently used in high-resolution spectrometry, to airborne gamma measurements is presented. A new algorithm has been developed for extraction of full absorption peaks by studying the variations in the spectral profile of data recorded with large-volume NaI detectors (16 l) with a short sampling time (2 s). The use of digital filters, taking into consideration the characteristics of the absorption peaks, significantly reduced the counting fluctuations, making detection possible based on study of the first and second derivatives. The absorption peaks are then obtained by modelling, followed by subtraction of the Compton continuum in the detection window. Compared to the conventional stripping ratio method, spectral profile analysis offers similar performance for the natural radioelements. The 137Cs 1SD detection limit is approximately 1200 Bq/m2 in a natural background of 200 Bq/kg 40K, 33 Bq/kg 238U and 33 Bq/kg 232Th. At low energy the very high continuum leads to detection limits similar to those obtained by the windows method, but the results obtained are more reliable. In the presence of peak overlaps, however, analysis of the spectral profile alone is not sufficient to separate the peaks, and further processing is necessary. Within the framework of environmental monitoring studies, spectral profile analysis is of great interest because it does not require any assumptions about the nature of the nuclides. The calculation of the concentrations from the results obtained is simple and reliable, since only the full absorption contributions are taken into consideration. A quantitative estimate of radioactive anomalies can thus be obtained rapidly.

Air Pollution, Radioactive↗