Improving the quality of aerial gamma-ray surveys (original) (raw)
Related papers
Calibration of the High and Low Resolution Gamma-Ray Spectrometers
2012
Many laboratories accredited according to the requirements of the standard EN ISO/IEC 17025:2005 “General requirements for the competence of testing and calibration laboratories” are implied in the measurement of the radioactive content of various materials, by analyzing samples collected from the environment and food chain or industrial products. The most used method is based on the gamma-ray spectrometry measurement, using high resolution HPGe and low resolution NaI(Tl) or equivalent detectors, with the advantage of being non destructive. In order to improve its sensitivity, one applies many technical and methodological means, such as: careful choice of detector material, passive or active detector shielding, measurement of high volume samples with various matrix content, positioned in close to detector geometries. This last aspect has direct influence on the measurement, by introducing large errors in the results when the influence of geometry, sample volume and content, and true...
Gamma-ray calibration energies: a review of the 192Ir data
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1993
In order to perform evaluations by the least-squares method, the complete covariance matrix for the gamma-ray energy standards is needed . Some errors due to excluding the covariances from the statistical analysis are pointed out. The gamma-ray energies of 1921r and 198Au, measured with curved-crystal spectrometers, were reanalyzed and the covariances between results determined . The gamma-ray energies were updated by including the latest values of the fundamental constants. The covariance matrix between gamma-ray energy data and the fundamental constants is deduced, so that the energy values can be updated correctly if new measurements are performed or if the fundamental constants are reevaluated .
Assessment of calibration parameters for gamma-ray spectrometry systems
Journal of Radioanalytical and Nuclear Chemistry, 2011
The Gamma-ray spectrometers are complex instruments and the quality of the data they provide depends strongly on their proper calibration. This paper describes the energy and efficacy calibration of two gamma-ray spectrometers in order to validate the method for measuring the activity of gamma-ray emitting radionuclides. The punctiform standard sources 60 Co, 133 Ba, 137 Cs and 241 Am were used in this study. Minimum Detectable Activity, Peak to Compton Ratio and the peak shape parameters were determinate. An inter-comparison of the results obtained with both systems was done. The results demonstrated that the activity values are comparable with low errors respecting with those for conventionally true activities.
Journal of Signal Processing Systems, 2021
Scintillator detector's electronics is recalibrated against the datasheet given by the manufacturer. Optimal and mutual dependent values of (a) high voltage at PMT (Photomultiplier Tube), (b) amplifier gain, (c) average time to count the radiation particles (set by operator), and (d) number of instances/sample number are estimated. Total 5: two versions of Central Limit Theorem (CLT), (3) industry preferred Pulse Width Saturation, (4) calibration based on MPPC coupled Gamma-ray detector and (5) gross method are used. It is shown that CLT method is the most optimal method to calibrate detector and its respective electronics couple. An inverse modeling-based Computerized Tomography method is used for verification. It is shown that statistically averaging results are more accurate and precise data than mode and median, if the data is not skewed and random number of samples are used during the calibration process. It is also shown that the average time to count the radiation particle is the most important parameter affecting the optimal calibration setting for precision and accurate measurements of gamma radiation.
Comparative measurements in dose calibrators and a gamma-ray spectrometer
Applied Radiation and Isotopes, 2010
Specific activity results of 51 Cr, 67 Ga, 99m Tc and 201 Tl radioactive solutions, measured in different dose calibrators located at nuclear medicine services and in a calibrated HPGe gamma spectrometer, were compared. The HPGe spectrometer was calibrated in a well defined geometry by means of 60 Co, 133 Ba, 152 Eu, 166m Ho and 241 Am sources, previously standardized in a 4pb À g coincidence system. Despite the observed differences, the results may be accepted within the 10% uncertainty range, established by Brazilian regulatory standards.
As a first step after installation of new software and hardware in the Neutron Activation Analysis (NAA) laboratories of Nigeria Research Reactor-1 (NIRR-1) the calibration of the spectrometer was carried out before any spectral analysis could be done. Both electronic spreadsheet and dedicated spectral analysis software (k0-IAEA) were employed and the results obtained from both methods were compared in this study. The efficiency curves were established from measurement and interpretation of several spectra from nine standard gamma-ray calibration sources (Na-22, Mn-54, Co-57, Co-60, Y-88, Cs-137, Eu-152, Ra-226, Am-241) whose activities are known to better than ±3%. The sets of values obtained for the full-energy peak detection efficiency from the two approaches are close at higher geometries with less than 10% variation.
p081 A Numerical Method for the Calibration of In Situ Gamma Ray Spectroscopy Systems
Health Physics, 2010
High purity germanium in situ gamma ray spectroscopy systems are typically calibrated using pre-calculated tables and empirical formulas to estimate the response of a detector to an exponentially distributed source in a soil matrix. Although this method is effective, it has estimated uncertainties of 10 -15%, is limited to only a restricted set of measurement scenarios, and the approach only applies to an exponentially distributed source. In addition, the only soil parameters that can be varied are density and moisture content, while soil attenuation properties are fixed. This paper presents a more flexible method for performing such calibrations. For this new method, a three-or four-dimensional analytical expression is derived that is a combination of a theoretical equation and experimentally measured data. Numerical methods are used to integrate this expression, which approximates the response of a detector to a large variety of source distributions within any soil, concrete, or other matrix. The calculation method is flexible enough to allow for the variation of multiple parameters, including media attenuation properties and the measurement geometry. The method could easily be adapted to horizontally non-uniform sources as well. Detector responses are calculated analytically and Monte Carlo radiation transport simulations are used to verify the results. Results indicate that the method adds an uncertainty of only approximately 5% to the other uncertainties typically associated with the calibration of a detector system. Health Phys. 98(5):657-671; 2010
Radionuclide Calibrators Performance Evaluation
Radionuclide calibrators are used to estimate accurately activity prior to administration to a patient, so it is very important that this equipment meets its performance requirements. The purpose of this paper is to compare the commercially available "Calicheck" (Calcorp. Inc), used to assess linearity, versus the well-known source decay method, and also to show our results after performing several recommended quality control tests. The parameters that we wanted to evaluate were carried on using the Capintec CRC-15R and CRC-15 βeta radionuclide calibrators. The evaluated tests were: high voltage, display, zero adjust, background, reproducibility, source constancy, accuracy, precision and linearity. The first six tests were evaluated on the daily practice, here we analyzed the 2007 recorded data; and the last three were evaluated once a year. During the daily evaluation both calibrators performance were satisfactory comparing with the manufacture's requirements. The acc...