Quench Correction Curves Research Articles

An estimation and radioactivity measurement for radiocarbon(14C) in the Korean nuclear power plants

Radiocarbon (14C), with a radioactive half-life of approximately 5730 years, poses a long-term environmental contamination risk when released into the atmosphere. The quantification analysis of its release estimates plant-specific generation rates based on factors such as plant power, core neutron flux distribution, and the volume of water exposed to this flux. Utilizing the improved estimation method, the 14C production rate for several Korean Pressurized Water Reactors (PWRs) was calculated. Also, improvements in measurement methods through sampling have also been made. These enhancements include the verification of the absorption method versus the mixing method.The results of this study indicate that plant-specific 14C production rates range from 0.213 to 0.317 TBq/yr, which are comparable to the global range observed in PWRs. Furthermore, the study evaluated a quenching correction curve for a liquid scintillation counter using two quenching correction methods: the external standard method and the internal standard method. The accuracy of these methods with 72 samples was validated with an average relative error within ±2.5%. The relative error of the mixing method, when compared to the direct absorption method, was found to be within ±20%. This finding underscores the validity of the improved measurement technique.

Study on Measurement Method of β Radioactivity in Environmental Water by Liquid Scintillation Spectrometers

Compared with other methods for measuring radioactivity in water, liquid scintillation measurement has the outstanding advantages of fast sample pretreatment, simple measurement method and high detection efficiency. Based on liquid scintillation spectrometer (SIM-MAX LSA3000B), 14C and 90Sr-90Y are selected as typical nuclides to study the change of TDCR quenching correction curve under different activity concentrations, and the basic method for measuring radioactive water samples with different activity concentrations is proposed, which is applied to the measurement of lake water, mountain spring water, tap water, mineral water and rainwater. The measurement results show that the total time of this method is less than 60 minutes, and the measurement error is less than 20%, which is obviously superior to the existing water sample radioactivity measurement method under nuclear emergency conditions.

Direct analysis of 210Pb in drinking water by liquid scintillation counting after sulfate precipitation

Lead-210 in drinking water can be rapidly determined by liquid scintillation counting (LSC) using a new sulfate precipitation method. In this method, 210Pb was first preconcentrated from water using iron hydroxide co-precipitation followed by sulfate precipitation to decontaminate most of non-alkaline earth elements. The Pb in the sulfate precipitate was then dissolved in strong alkaline solution, while alkaline earth elements (Sr, Ba, Ra) were separated as the sulfate/carbonate precipitate. To optimize the method, the influences of different acids and sulfate concentration on sulfate precipitation as well as the effects of pH, the added SO42−/CO32− concentrations and the Sr/Ba contents in the sulfate precipitate on the dissolution of PbSO4 were studied. In addition, X-ray fluorescence (XRF) analysis was applied for rapid determination of the chemical recovery and triple-to-double coincidence ratio (TDCR) quench correction curve for counting of 210Pb by LSC was established. The method was validated using 5 L of tap water samples and minimum detectable activity concentration (MDC) of ∼0.016 Bq·L−1 was achieved, which is sufficiently sensitive to meet the guidance level of 0.1 Bq·L−1 for 210Pb in drinking water as recommended by the World Health Organization (WHO).

Study on optimization of liquid scintillation counting during tritium measurements

This study was intended toward the evaluation of the correlation between the quenching coefficients and the counting efficiency for the physical quenching phenomenon and the effects of the properties of the standard sources for quenching on the tritium radioactivity concentration in the process of analyzing the tritium radioactivity concentration. Accordingly, a series of standard sources for quenching was prepared using three types of vials with different properties used for correction by the quenching phenomenon; the calculated values of the counting efficiency of a series of standard sources for quenching, relative errors in the counting values, uncertainty, and properties of the quenching correction curve were evaluated. On the basis of the results, nine samples (three glass-vial-type samples, three plastic-vial-type samples, and three Teflon-vial-type samples) were obtained and evaluated by applying Parameter Groups 1, 2, and 3, for which the efficiency was calibrated using the WinQ program in accordance with the properties of a series of standard sources for quenching. The results of this study are expected to serve as an aid in accurately understanding the standard sources for quenching, counting, and analyzing environmental samples that are subject to counting and analysis.

Determining the activity of 241Pu by liquid scintillation counting

Liquid scintillation counting (LSC) is one of the most widely used methods for determining the activity of 241Pu. One of the main challenges of this counting method is the efficiency calibration of the system for the low beta energies of 241Pu (E max = 20.8 keV). In this paper we compare the two most frequently used methods, the CIEMAT/NIST efficiency tracing (CNET) method and the experimental quench correction curve method. Both methods proved to be reliable, and agree within their uncertainties, for the expected quenching conditions of the sources.

Determination of 3H and 14C in the Dry Active Wastes (DAW) generated from the Light Water Reactors (LWR) by a wet oxidation method

3H and 14C Measurements of the dry active waste (DAW), such as the cotton, paper, and vinyl, generated from a nuclear power plant (NPP) were conducted with wet oxidation using open vessel equipment based on simulation results. The recovery efficiency with the simulated samples was around 93% with a relative standard deviation (RSD) of 1–3%. A liquid scintillation counter (LSC) was used for counting and adjusted to a quenching correction curve. The counting value was evaluated for the minimum detectable activity (MDA), which was found to be about 4 × 10−1 Bq/g for 3H and 2 × 10−2 for 14C when approximately 5 g of the samples were measured. The measured DAW samples for the cotton, paper, and vinyl generated from NPP achieved of RSD values of 25, 25, and 60%, respectively, for 3H and 0–50% for 14C.

Separation of phosphorous by liquid–liquid extraction for the measurement of 32P

Phosphorous containing radioisotope waste was separated and determined by liquid–liquid extraction method through liquid scintillation counter (LSC). In this process, ammonium phosphate was converted to phosphomolybdate (PMo) by the reaction of ammonium molybdate (Mo) in HCl solution (0.02 M) and maximum UV/VIS absorbance (λmax) 218 nm was observed. The PMo solution was extracted with TOA (Tri-n-Octylamine)/xylene mixture and λmax 290 nm was found for this organic layer. Absorbance of aqueous and organic layer was linear through concentration. The impurities such as Co, Cr, Gd, etc. remain in aqueous layer by treating with Mo which was determined by ICP-AES and AAS. The quenching correction curve for 32P was calculated using LSC results. No counting change was observed as the volume of quenchers increased. The recovery was 98% and 81% for the extraction and separation process from the test using H332PO4 as standard tracer.

Color quench correction for low level Cherenkov counting

The Cherenkov counting efficiency varies strongly with color quenching, thus correction curves must be used to obtain correct results. The external 152Eu source of a Quantulus 1220 TM liquid scintillation counting (LSC) system was used to obtain a quench indicative parameter based on spectra area ratio. A color quench correction curve for aqueous samples containing 90Sr/ 90Y was prepared. The main advantage of this method over the common spectra indicators is its usefulness also for low level Cherenkov counting.

Involvement of Highly Sulfated Chondroitin Sulfate in the Metastasis of the Lewis Lung Carcinoma Cells

The altered expression of cell surface chondroitin sulfate (CS) and dermatan sulfate (DS) in cancer cells has been demonstrated to play a key role in malignant transformation and tumor metastasis. However, the functional highly sulfated structures in CS/DS chains and their involvement in the process have not been well documented. In the present study, a structural analysis of CS/DS from two mouse Lewis lung carcinoma (3LL)-derived cell lines with different metastatic potentials revealed a higher proportion of Delta(4,5)HexUA-GalNAc(4,6-O-disulfate) generated from E-units (GlcUA-GalNAc(4, 6-O-disulfate)) in highly metastatic LM66-H11 cells than in low metastatic P29 cells, although much less CS/DS is expressed by LM66-H11 than P29 cells. This key finding prompted us to study the role of CS-E-like structures in experimental lung metastasis. The metastasis of LM66-H11 cells to lungs was effectively inhibited by enzymatic removal of tumor cell surface CS or by preadministration of CS-E rich in E-units in a dose-dependent manner. In addition, immunocytochemical analysis showed that LM66-H11 rather than P29 cells expressed more strongly the CS-E epitope, which was specifically recognized by the phage display antibody GD3G7. More importantly, this antibody and a CS-E decasaccharide fraction, the minimal structure recognized by GD3G7, strongly inhibited the metastasis of LM66-H11 cells probably by modifying the proliferative and invading behavior of the metastatic tumor cells. These results suggest that the E-unit-containing epitopes are involved in the metastatic process and a potential target for the diagnosis and treatment of malignant tumors.

Quench Correction by External Standard Source 152Eu Exchanged for Originally Equipped 226Ra

The external standard source of liquid scintillation counter, 226Ra, was exchanged to 152Eu. Quench correction curves by irradiating the radiation to quenched standard samples for a single labeled 3H or 14C, or dual labeled 3H and 14C, were plotted by the computer software that controls the liquid scintillation counting system. Using the correction curve, the radioactivity of quenched standard sample for making correction curves, was determined again quantitatively. The most of corrected values were within ±5% error of the nominal radioactivity of the standard sample.

In situ calibration of a low-level, in-line, flow liquid scintillation analyzer.

A new method to calibrate a flow liquid scintillation detector in an in-line waste water monitor was developed and its operation was verified. The liquid scintillation detector for detecting low energy beta emitters was one of three detectors of the monitor that aimed to analyze radionuclide concentrations in the waste water before draining it into sewer. To calibrate the liquid scintillation detector, a 20-cm3 calibration vial containing a reference solution was connected to the water sampling channel with a three-way valve. Ten measurements needed to define a quench correction curve required only 200 cm3 solution. The counting efficiencies of the liquid scintillation detector for 3H and for 14C under the average quenching level of the waste waters were estimated at 27% and 58%, respectively. The calibration using the vial took into account the sampling and mixing system, which would not be the case with sealed quenched standards. Although active solution was used, the method was simple, generated little active waste, had low possibility of contamination, and reduced costs and labor for the calibration.

Measurement of 90Sr in aqueous samples using liquid scintillation counting with full spectrum DPM method

90Sr activity was measured with the full spectrum DPM (FS-DPM) counting method after plotting the quench correction curves of 90Sr and 90Y, and the FS-DPM method was applied to determine the 90Sr in liquid waste samples. The optimum regions of 90Sr and 90Y were set for measuring 90Sr with the dual label DPM (DL-DPM) method. The direct measurement of purified 90Sr with spectrum unfolding techniques could overcome the disadvantages of the DL-DPM method. The activities of 90Sr in the 90Sr/ 90Y standardized solution measured with the FS-DPM protocols were close to the true activity. The concentrations of 90Sr in the liquid waste samples measured with the FS-DPM counting method were compared with those obtained with conventional methods.

A multiple window deconvolution technique for measuring low-energy beta activity in samples contaminated with high-energy beta impurities using liquid scintillation spectrometry

An optimised multiple window counting technique, using liquid scintillation counting combined with internal standardisation and spectrum unfolding has been developed for the assessment of low-level, low-energy beta activity in multilabeled samples containing high-energy beta impurities. Distinct spectral contributions are reconstructed for every individual radionuclide and impurity using software deconvolution techniques. The most important advantages of this method are that it does not require setting up quench correction curves and that the exact knowledge of reference activity is not required, thus eliminating two important sources of uncertainty in the final results. The technique has been successfully used on mixtures of 3H, 14C, 63Ni, 99Tc and 60Co over a wide range of quenching and activity ratios.

Determination of Tritiated Dexamethasone in Rat Liver and Muscle: Comparison of Two Sample Preparation Techniques, Combustion and Solubilization, Prior to Liquid Scintillation Counting

Rats were injected intramuscularly with 20 μCi/kg [3H]dexamethasone, which is a synthetic therapeutic glucocorticoid. After 2 h, the rats were sacrificed, and liver and muscle tissues were taken for assay. 3H radioactivity measurements were performed in a liquid scintillation counter. The objective of this study was to compare two sample preparation techniques, namely, alkaline solubilization versus dry combustion, to release the incorporated radioactivity quantitatively from rat liver and muscle; sample combustion has a recovery of 99 ± 1.0%. In addition, the effect of bleaching the samples with hydrogen peroxide was evaluated and quench correction curves were established. The current data demonstrated that the efficiencies of both methods were similar in the measurement of [3H]dexamethasone incorporated in rat liver and muscle tissues. For muscle, differences in disintegrations per minute (dpm) reached only 0.18%; for liver, the score was 0.78%. In conclusion, knowledge of the total radioactivity presen...

Accuracy of Cerenkov measurements using a liquid scintillation spectrometer

Cerenkov counting efficiency varies with colour quenching and sample turbidity. The activity in a plastic vial can be determined accurately with a colour quenching correction technique, regardless of the presence or absence of turbidity in a sample. On the other hand, the error of the measured activity in a glass vial becomes large with increasing sample turbidity due to the dissimilarity of the quench correction curves for non-turbid and turbid samples.

Activity determination of simultaneously chemical and color quenched samples using a liquid scintillation counter

Activities of simultaneously chemical and color quenched samples can be accurately determined by using a combination of two external standard techniques, these are, an external standard quenching correction curve and a double external standard relation curve. The latter curve is used for estimating the degree of contribution of chemical and color quenching for the samples. All that is required for this technique are chemical and color quenched standard sample sets for the nuclide to be radioassayed. The technique has been applied to the cases of 3H and 14C, and found to be very practicable with the aid of computerized data processing.

The design and testing of an emulsifying liquid scintillant based on cyclohexylbenzene

The design and testing of a new emulsifying liquid scintillant for the radioassay of aqueous samples is described. The scintillant is based on cyclohexylbenzene which has a high flash point and low toxicity. A suitable combination of surfactant and cyclohexylbenzene/PPO scintillator was developed by the construction and comparison of triangular contour diagrams, as described by FOX1 for each, of several commonly-encountered aqueous sample types. The chosen olend of surfactant, cyclohexylbenzene and PPO was further refined with a second surfactant. This was achieved by the construction of a diagram of temperature v.s. water content for each of several blends, each containing a different surfactant combination. Similar diagrams were constructed to illustrate the compatibility of several aqueous sample types with the chosen composition. SCR and AESCR quench correction curves were constructed for each sample type.

Reliability of the activity determined by the quenching correction method for two groups of emulsion scintillators

The reliability of the activity, determined using conventional quenching correction methods, has been studied for two groups of emulsion scintillators: (1) scintillators with three distinct water dilution criteria; and (2) scintillators forming a miscible solution with up to 50% water content. Whilst for the first group of scintillators the error of the activity measured very often becomes larger with increased water content, the measurements with the second group of scintillators fit the quenching correction curve.

Double ratio technique for determining the type of quenching in liquid scintillation measurement

A new double ratio technique which enables the detection of whether prepared samples for liquid scintillation measurement are predominantly colour- or chemical-quenched has been proposed. This technique makes it possible to determine the quenching correction curve to be employed in finding the activities of samples, resulting in reduction in the error which may arise from the difference between colour and chemical quenchings. This technique has been applied to the cases of 3H and 14C radioassays, and found to be practicable.

A simple program which processes liquid scintillation counting data from samples containing both 125I and 3H under conditions of varying quench

A simple program was written for a programmable calculator which enabled simultaneous measurement of 3H and 125I by liquid scintillation counting. The program uses quench correction curves to calculate the effects of quench in each sample and calculates the amount of each isotope present by solving a linear equation set simultaneously.