ABSTRACT
This work presents the results of an experimental study of the Makrofol® N and Makrofol® DE polycarbonate foils absorption properties of 85Kr and 131mXe. The diffusion lengths of 85Kr and 131mXe in both types of foils are determined. The partition coefficients of 85Kr from air and water and that of 131mXe from air in Makrofol® N are determined. The partition coefficients of 85Kr from water and 131mXe from air in Makrofol® DE are also determined. The parameters are determined for T = 22°C and allow for the full characterization of sorption and desorption of 85Kr and 131mXe in the foils at this temperature. The results from this study highlight the remarkable absorption ability of Makrofol® and especially of the Makrofol® N foil and show that it surpasses the Makrofol DE® foil not only as a Rn absorber, but also as Kr and Xe absorber.
ABSTRACT
A new experiment was designed to measure the photon emission intensities in the decay of 103mRh. The rhodium samples were activated in the ISIS experimental nuclear reactor at CEA Saclay. The procedure includes an absolute activity measurement by liquid scintillation counting using the Triple-to-Double Coincidence Ratio method, followed by X-ray spectrometry using a high-purity germanium detector to determine the photon emission intensities. The new result (IX = 0.0825 (17)) is derived with a significant reduction of the uncertainty.
ABSTRACT
This work demonstrates that a Liquid Scintillation Counting (LSC) technique using a Triple to Double Coincidence Ratio counter with extending dead-time is very appropriate for the accurate measurement of (222)Rn activity absorbed in thin polycarbonate foils. It is demonstrated that using a toluene-based LS cocktail, which dissolves polycarbonates, the (222)Rn activity absorbed in thin Makrofol N foil can be determined with a relative standard uncertainty of about 0.7%. A LSC-based application of the methodology for determination of the diffusion length of (222)Rn in thin polycarbonate foils is proposed and the diffusion length of (222)Rn in Makrofol N (38.9±1.3µm) and the partition coefficient of (222)Rn in Makrofol N from air (112±12, at 20°C) and from water (272±17, at 21°C) are determined. Calibration of commercial LS spectrometers for (222)Rn measurements by LSC of thin polycarbonate foils is performed and the minimum detectable activities by this technique are estimated.
ABSTRACT
The cross-efficiency method in LSC is one of the approaches proposed for the extension of the Système International de Référence (SIR) to radionuclides emitting no gamma radiation. This method is based on a so-called "universal cross-efficiency curve", establishing a relationship between the detection efficiency of the radionuclide to be measured and the detection efficiency of a suitable tracer. This paper reports a study at LNHB on the influence of the scintillator and of the LS counter on the cross-efficiency curves. This was done by measuring the cross-efficiency curves obtained for (63)Ni and (55)Fe vs. (3)H, using three different commercial LS counters (Guardian 1414, Tricarb 3170 and Quantulus 1220), three different liquid scintillator cocktails (Ultima Gold, Hionic Fluor and PicoFluor 15 from Perkin Elmer(®)), and for chemical and colour-quenched sources. This study shows that these cross-efficiency curves are dependent on the scintillator, on the counter used and on the nature of the quenching phenomenon, and thus cannot definitively be considered as "universal".
ABSTRACT
The (3)He ingrowth technique is based on the detection of the tritium radioactive daughter, (3)He, by mass spectrometry. Over the last three decades it has been used extensively in oceanography and groundwater studies for measurements of very low to ultra-low levels of tritium. To compare it with the best available methods of radioactive counting, we applied this method to measure the massic activity of a tritiated-water primary standard prepared by the French Laboratoire National Henri Becquerel (LNHB). One liter of a low-level tritium solution was prepared from a small aliquot of the LNHB standard by two-step gravimetric dilution with tritium-free groundwater. Sixteen samples of this solution were analyzed at the LSCE-Saclay noble gas facility, using the (3)He ingrowth method. The massic activity of the prepared solution was also measured by Liquid Scintillation Counting using the Quantulus LNHB counter and an internal calibration method with the LNHB tritiated water standard. All results agree within their standard uncertainty.
ABSTRACT
The principle of the Compton source efficiency tracing method (CET) in liquid scintillation counting (LSC) is to use, as a tracer, a Compton electron source temporarily created inside the source being measured. The tracer source and the source to measure have thus exactly the same chemical composition. A main advantage anticipated for this measurement method is its low sensitivity to the kB factor and insensitivity to the chemical composition and quenching of the source, which would obviate the necessity to develop a reference liquid scintillator cocktail in the framework of an international reference system for the measurement of pure-beta emitters by LSC. We took the opportunity of a tritiated water international activity measurement in comparison to prepare LS sources using various commercial liquid scintillator cocktails. Tritium is assumed to be a good candidate for testing the LSC activity measurement method, as the detection efficiency is rather low and the effect of the ionization quenching parameter, kB, on the detection efficiency calculation by the TDCR method is known to be important. The sources were measured using a TDCR counter equipped with a Compton spectrometer in order to apply the CET method. The measurements are analyzed using both the TDCR method and CET method in order to deduce the optimal calculation parameters. The detection efficiency range covered by these experiments is from 0.4 to 0.6, allowing a good test of the validity of the physical assumptions included in the calculation model. The paper will conclude on the advantages and drawbacks of using this CET method in the framework of an international reference system for low-energy pure-beta radionuclides.
ABSTRACT
This study describes a new determination of the decay scheme and half-life of (93)Zr. A pure (93)Zr solution was obtained after chemical separation from the dissolution of an irradiated zircaloy sample. The concentration of (93)Zr in the solution was measured by mass spectrometry, with an isotopic dilution technique. The activity of the solution was measured by liquid scintillation counting, using an efficiency tracing method. The measurement of the activity concentration of (93)Nb(m) by X-ray spectrometry, allowed the determination of the (93)Zr decay scheme and the calculation of the (93)Zr detection efficiency. This leads to the calculation of the decay probability of (93)Zr toward (93)Nb(m) of (0.73+/-0.06) and to a half-life of (93)Zr of (1.64+/-0.06)x10(6) years. These values are discussed in comparison with the evaluated values available in the literature.
ABSTRACT
Liquid scintillation counting (LSC) is widely used at LNHB for primary standardization of radionuclides (TDCR method), for secondary calibration and also for source stability studies or radioactive purity measurements. A total of five LSC counters are used for these purposes: two locally developed 3-photodetector counters for the implementation of the TDCR method, two Wallac 1414 counters and one Wallac 1220 Quantulus counter. The quality of the LSC measurements relies on the correct operation of these counters and their traceability to the frequency and time units.
