Authors:P. Vermaercke, L. Sneyers, M. Bruggeman, A. De Wispelaere, and F. De Corte
Several methods are in use for the determination of the thermal to epithermal neutron fluence rate ratio (f) and the deviation of the epithermal neutron spectrum from the 1/E shape parameter (α). In our former work, it was proven that the recently developed and characterized Synthetic Multi-ELement Standard (SMELS)
can be used for the fast verification of the stability of the irradiation parameters using the Au-Zr bare monitor method.
However, this latter method using SMELS had a too low precision for an accurate determination of f and α. Therefore, the Cd-ratio for multi-monitor method using SMELS was investigated for two irradiation channels. As shown the
material can also be used as a monitor for the calibration of an irradiation facility.
The intrinsic consistency and discrete character of high resolution gamma spectrometric measurements are used in order to
make self-calibration of these measurements. Both energy and overall relative efficiency (including all geometrical self-attenuation
and attenuation factors as well as the detector efficiency) can be performed using the same measured spectrum. The method
is particularly useful for non-destructive gamma spectrometric measurements of isotopic ratios on different nuclear material
samples. As an illustration, a complete isotopic analysis of U/Pu mixed oxide rods is given. The accuracy of the isotopic
measurements depends strongly on the accuracy of the available nuclear data and comparison with destructive analysis when
possible facilitates the process of obtaining more accurate nuclear data for the isotopes involved. The attainable accuracy
is estimated to be better than 0.5% for239Pu and241Pu measurements.
Fourteen organic compounds, 1-pentene, 2-methylbutane, 2-methyl-1,3-butadiene (isoprene),n-pentane, 2-chloropropane, ethyl alcohol, 2,2,4-trimethylpentane,n-hexane,n-hepatane, 1,3-difluorobenzene, 1,2-dichloroethane, hexafluorobenzene, cyclohexane and diphenyl ether, as new reference materials
for energy and temperature calibrations of differential thermal analysers (DTA) and differential scanning calorimeters (DSC)
in the temperature range 100–300 K, were investigated. The purities, triple point and transition temperatures, fusion and
transition enthalpies of these compounds were measured using a low-temperature DTA apparatus developed by the CTM of the CNRS
in Marseille. The results obtained were compared with those produced by adiabatic precision calorimetry. Our data are in good
agreement with literature values. Enthalpies of fusion and transition, triple point and transition temperatures are reproduced
within ±1% and ±0.1K, respectively.
To perform quantitative analysis of Ge(Li) spectra, not only energy calibration but also efficiency calibration procedures are done. Although the use of standard sample volume, mass, density and geometry is preferable, this optimum is not always possible. So to achieve an optimization is the main objective of the work reported here. Efficiencies have to be determined as a function of energy, density, thickness, mass of sample, intensity, and source-to-detector distance.
A melting point measurement facility for the UK has been developed and accredited to ISO/IEC 17025 Calibration status for
the determination of the liquefaction temperature of pure substances from 35 to 250°C.
The facility is based upon a commercial instrument, i.e. an oil bath fitted with an aluminium block (Isotech, model 798 EHT),
a precision multimeter (Isotech TTI-7), a thermocouple directly inserted in the sample under investigation and a platinum
resistance thermometer (PRT) tracking the block temperature. The homogeneity of temperature bath/block was investigated and
the PRT used for the traceability of the measurements was calibrated by NPL and traceable to ITS-90. The process was validated
using four current LGC Certified Reference Materials (CRMs):
Carbazole; material number: LGC2409, batch number: 007; liquefaction point: 245.58±0.07°C
Different approaches were used to identify reproducible features of the melting point (time-temperature) curves of these four
CRMs. Excellent correlation was observed between the certified values for the liquefaction point of the four CRMs and the
temperature at the end of their respective melting point curve plateau, determined using a temperature differential approach.
An uncertainty budget was derived and the expanded uncertainty at the 95% confidence interval (k=2) was found to be
Authors:F. De Corte, S. Hossain, S. Jovanovič, A. Dlabač, A. De Wispelaere, D. Vandenberghe, and P. Van den Haute
A study is made of the corrections that are needed in the evaluation of the annual radiation dose, for use in TL/OSL-dating, via NaI(Tl) field gamma-ray spectrometry (monitoring of K, Th and U), calibrated via voluminous blocks that are simulating the Auger hole measuring conditions. Two cases are considered: the Heidelberg granite calibration block, which was found to be quasi-infinite, and the Oxford concrete calibration blocks, for which effective concentrations of elements are reported so as to account for their non-infiniteness. The calculations, via the software package ANGLE, are based on the concept of effective solid angles for Marinelli geometries.
Two sets of calibration standards for134Cs and137Cs were prepared by small serial dilution of a natural matrix standard reference material, IAEA-154 whey powder. The first set was intended to screen imported milk powders which were suspected to be contaminated with134Cs and137Cs. Therefore the concentration range of the calibration standards were about 40–400 Bq/kg. The precision of the preparation of the standard with about 7 Bq/kg of134Cs and 39 Bq/kg of137Cs at measurement time was 7.4% and 3.2%, respectively. The preparation of a similar standard by spiking the matrix with radioisotope solutions resulted in a poorer precision, about double that of the former technique. The other set of calibration standards was prepared to measure the environmental levels of137Cs in commercial Venezuelan milk powders. Their concentration ranged from 3–10 Bq/kg of137Cs. The accuracy of these calibration curves was checked by using IAEA-152 and A-14 milk powders. Their measured values were in good agreement with their certified values. Finally, it is shown that these preparation techniques by serial dilution of a standard reference material were simple, rapid, precise, accurate and cost-effective.
To give satisfactory efficiency both for X- and gamma-ray photon, an improved counting system has been developed in CTBT Canadian
radioxenon laboratory. The counting system consists of a BEGe detector coupled with a thin carbon fiber window counting cell,
that can perform a reliable and efficient radioxenon measurement. A semi-empirical calibration procedure was adopted, which
is a combination of experimental measurement and mathematical simulation. Mathematical calibration tool is Monte Carlo simulation
software named VGSL. Advanced gamma-spectrum analysis software, named Aatami, was used for gamma-ray peak shape fitting and
X-ray multiplets deconvolution. The calculated full energy peak efficiency curve covers from 30 to 700 keV and agrees well
with experimental data points within 2%. The efficiency curve can provide radioxenon analysis both for X-rays and gamma-rays
with high quality. The efficiency distortion near xenon k-absorption edge of 35 keV, which is caused by high concentrated
xenon in the counting cell, is also discussed.
Authors:E. Lepel, W. Hensley, R. Brodzinski, and J. Smart
A pilot plant is being designed at the U. S. Department of Energy's Savannah River Site (SRS) to demonstrate the removal of 90Sr, 137Cs, and transuranics from a high-level liquid waste stream prior to encapsulation in a Saltstone Facility. In-line monitors are required to determine the concentration of all radionuclides on this processed waste stream. Calibration standards containing 60Co, 137Cs, and 90Sr were prepared and counted. Efficiency curves were generated. Strontium-90 is readily observable above the system background in the calibration standard count, and is observable at less than 3 nCi/ml in a mixed solution having the maximum allowable concentration of all other activities present in the proposed SRS effluent stream.
A new assembly dedicated for the low-level ψ-ray spectrometric measurements of environmental samples have been installed recently
at the International Atomic Energy Agency's Laboratories, Seibersdorf. Calibration of the detection efficiency was performed
by a set of 14 IAEA Certified Reference Materials, a standardized solution of134Cs, solutions of 2 pure potassium salts, and 2 mixed radionuclide gamma reference standard solutions. These materials, in
1.3 liter Marinelli beakers, were measured by a large HPGe detector. The high precision and accuracy of the calibration procedure
is shown by the high significance achieved in the linear fits of the efficiency results, which are traceable to certified
and standard reference materials. Small biases between some calibrands were detected. A new corrected result is the 1.37±0.05
Bq/kg activity concentration of137Cs in IAEA-A-14 Milk Powder.