Liquid Scintillation Technique Research Articles

Determination of 222Rn in air by alpha liquid scintillation using solvent extraction

A dynamic sampling method is proposed for the determination of 222Rn in air samples by extraction of the gas with a liquid scintillator and measurement of the alpha-radiation by a liquid scintillation technique. A detailed study of the procedure is carried out in order to define the optimal sampling conditions: times longer than 5 min and flows of the order of 450 cm 3/min are recommended using a xylene-based scintillator at room temperature to extract the radon from the air. Background reduction is also improved by separation of the alpha and beta pulses, such that the alpha-spectra used for the determination of 222Rn present sufficient sensitivity for environmental applications.

Application of pulse decay discrimination liquid scintillation counting for indoor radon measurement

The pulse decay discrimination (PDD) liquid scintillation technique has been applied to optimise radon counting by the Pico-Rad method. A dermination limit (with 10% relative error) of 4.8 Bqm−3 for indoor radon measurement has been achieved for optimal PDD setting with a radon elution cocktail containing 20% (v/v) of Ultima Gold AB in Instafluor. From a practical point of view this procedure allows a shortening of the counting time to 1 hour after 48 hours exposure to detectors. This method has been applied to indoor radon determinations in 626 places (municipal offices and private dwellings) in the Lodz region. These measureents resulted in an average concentration of 21.4 Bqm−3 and a median value of 15.1 Bqm−3. Analysis of the data indicates that most indoor radon comes from the underlying soil, which contains relatively little226Ra (10–20 Bqkg−1).

核種分析型β線排水モニタの構築

An radioactivity monitor for waste solution has been constructed using a liquid scintillation technique, which enables beta-emitter mixture to be analytically radioassayed. The method of least squ-ares has been applied to the radioassay for relatively low-level beta-emitter mixture in radioactive waste solution. This system can get rid of the difficulty of analysis for beta-emitter mixture in a mon-itoring sample, and provides fundamental information for subsequent waste-treatment. Detection limit of five nuclides was estimated to be about 0.02 Bq/cm3, which is sufficiently low compared with the values of authorized safety guideline.

Accidental Contamination with 90Sr: A Case Study

A case of accidental inhalation and extensive contamination by 90 Sr was observed in November 1995 in two workers who were handling a defective waste container with an old source of 90 Sr used for lightning rods. An internal monitoring programme was established to obtain experimental excretion data from each worker. Urine bioassays were carried out and activities of 90 Sr were determined from analyses of excreta by the liquid scintillation technique. The results were evaluated in accordance with ICRP recommendations using the dosimetric code GENMOD-PC. Since no information was available concerning aerosol size nor compound of the radionuclide, estimations of intakes were made following ICRP 30 recommendations, and an AMAD of 1 μm was assumed for the inhaled radioactive aerosol supposedly containing strontium titanate. The ICRP 30 theoretical excretion curve did not agree with the experimental data. Confirming that the source contained SrTiO 3 ; the assumed 1 μm particle size of the aerosol accidentally inhaled had to be changed to 10 μm, in order to adjust the urinary excretion function to the measured values. The initial estimation for one of the exposed workers, assuming a I μm particle size, resulted in a 90 Sr intake of 5 ALls. The final intake estimations were made with the following assumptions: acute inhalation 24 November 1995, AMAD=10 μm, Class Y solubility and ICRP 30 Respiratory Tract Model for Standard Man. The 90 Sr estimated intake was 2.6 x 10 5 Bq (37% ALI) for one of the workers and 6.6 x 10 4 Bq (10% ALI) for the other. The committed whole-body effective dose equivalents were 19 mSv and 5 mSv respectively, and the dose equivalents to lung were 147 mSv and 37 mSv, respectively.

Variation of 222Rn in public drinking water supplies.

The U.S. Environmental Protection Agency has proposed regulating 222Rn in public drinking water. When implemented, the regulation will require periodic sampling to demonstrate compliance. The work reported in this paper was conducted to evaluate how reliably grab samples can be used to characterize the average 222Rn concentration in a groundwater source. Periodic samples were collected from 14 wells over sampling periods ranging from 2 to 26 mo. Samples were collected using a "slow-flow" collection method, and samples were analyzed using liquid scintillation techniques. The results reveal variation in 222Rn concentration over the study period; however, for the 1,468 samples collected from the 14 wells, approximately 97% of the measurement results were within 30% of the mean value for the well.

Carbon exchange between Polysiphonia lanosa (Rhodophyceae) and its brown algal host

Polysiphonia lanosa and its preferred Ascophyllum nodosum host exchange 14C-labeled photoassimilates. Exchange was demonstrated by injecting 14C-bicarbonate into air bladders on 15-30 cm cultured sections of field-collected host blades. Each section bore rhizoidally attached Polysiphonia. In a separate set of experiments, Polysiphonia on similar host material was surface treated with 14C-bicarbonate in sealed vessels. Movement of radioactive label was detected by autoradiographic and liquid scintillation techniques. On average, 10.5% of total label moved from host to hemiparasite following the first treatment, and 9.7% moved from hemiparasite to host following the second. Reciprocal exchange of tagged photoassimilates may play an important role in the specificity of the relationship between these two algal species.

Determination of HTO content in polar ice/snow samples by low background liquid scintillation technique

Determination of HTO content in polar ice/snow samples by low background liquid scintillation technique

The interaction between methylene blue and the cholinergic system.

1. The inhibitory effects of methylene blue (MB) on different types of cholinesterases and [3H]-N-methylscopolamine ([3H]-NMS) binding to muscarinic receptors were studied. 2. Human plasma from young healthy male volunteers, purified human pseudocholinesterase and purified bovine true acetylcholinesterase were incubated with acetylcholine and increasing concentrations of MB (0.1-100 mumol l-1) in the presence of the pH-indicator m-nitrophenol for 30 min at 25 degrees C. The amount of acetic acid produced by the enzymatic hydrolysis of acetylcholine was determined photometrically. 3. Rat cardiac left ventricle homogenate was incubated with [3H]-NMS and with increasing concentrations of MB (0.1 mmol l-1 mumol l-1) at 37 degrees C for 20 min. THe binding of [3H]-NMS to the homogenate was quantified by a standard liquid scintillation technique. 4. MB inhibited the esterase activity of human plasma, human pseudocholinesterase and bovine acetylcholinesterase concentration-dependently with IC50 values of 1.05 +/- 0.05 mumol l-1, 5.32 +/- 0.36 mumol l-1 and 0.42 +/- 0.09 mumol l-1, respectively. MB induced complete inhibition of the esterase activity of human plasma and human pseudocholinesterase, whereas bovine acetylcholinesterase was maximally inhibited by 73 +/- 3.3%. 5. MB was able to inhibit specific [3H]-NMS binding to rat cardiac left ventricle homogenate completely with an IC50 value of 0.77 +/- 0.03 mumol l-1, which resulted in a Ki value for MB of 0.58 +/- 0.02 mumol l-1. 6. In conclusion, MB may be considered as a cholinesterase inhibitor with additional, relevant affinity for muscarinic binding sites at concentrations at which MB is used for investigations into the endothelial system. In our opinion these interactions between MB and the cholinergic system invalidate the use of MB as a tool for the investigation of the L-arginine-NO-pathway, in particular when muscarinic receptor stimulation is involved.

イメージングプレートによる粗表面汚染密度測定

Floating radioluminography using an imaging plate can be sufficiently applied to the monitoring of the surface contamination on rough surface materials at a radioisotope facility. This technique is superior to the smear method which has been used to estimate the contamination of low energy β-ray emitters, because the fixed contamination and the contamination on the coarse surface materials have been difficult to be wiped out on a smear paper. The radiation detection efficiency of the imaging plate is as high as the liquid scintillation technique, when the plate is exposed with the sample in a vacuum chamber. In this study, the technique has been tested to the surface monitoring of a liquid-waste concrete cistern, and the sort of contaminant radioisotope was estimated by inserting a plastic film or an aluminum plate between the imaging plate and the sample.

新しいスミア測定技術

A smear measurement system for a low-energy β emitter has been developed, which uses a paraffin scintillator for a radiation detector. In sample preparation, the radioactive contamination on a smear sample can be solidified immediately by adding small amount of a liquid-solid reversible paraffin scintillator. This technique overcomes many disadvantages of a conventional liquid scintillation technique ever employed, and allows the smear sample to be measured repeatedly and stored.

Radioanalytical methods for determination of alpha emitters in the environment

Modern radiometric methods for the determination of alpha emitting radionuclides in the environment are reviewed. These include alpha spectrometry, liquid scintillation techniques, and gamma spectrometry. Aspects such as a sample pretreatment, separation techniques and counting source preparation are considered.

Effect of the Prostaglandin E2, F2.ALPHA. and Indomethacin on the Incorporation of 3H-Methionine in Rat Blastocysts Development.

The effect of the prostaglandin E2, F2α and indomethacin on the incorporation of 3H-Methionine in rat blastocyst development was studied by the method of liquid scintillation technique. The eggs of intact pregnant rats when they were on the morula, early blastocyst, blastocyst, and late blastocyst stages were collected. Blastocysts of delayed implantation rats were also collected on the day 6 and 8. The rate of implantation of 3H-Methinine in delayed blastocysts was smaller than in normal blastocysts. Addition of prostaglandin E2 or F2α had accelerated the incorporation of 3H-Methionine in blastocysts at preimplantation and during delayed implantation (P<0.05). But addition of indomethacin inhibited the incorporation of 3H-Methionine in blastocyst and delayed implantation on the day 6 and 8 (P<0.05).

A very forward calorimeter for the LHC: Experimental results.

We report on measurements performed on a liquid scintillator calorimeter prototype designed for the very forward region in an experiment at the LHC. The liquid scintillator technique has the well known advantages of high speed, low noise and radiation hardness. The proposed solution is a SPACAL-like calorimeter with liquid scintillator circulating in quartz tubes positioned in a lead matrix. The beam tests were performed at the CERN SPS with electrons and pions in the range 20–120 GeV. Results on the energy response and resolution are presented.

In vitro effects of methionine-enkephalin, somatostatin and insulin on cultured gonadal cells of the snail Helix aspersa.

Isolated snail gonadal cells were cultured in the presence of synthetic neuropeptides in order to determine the subsequent effect of these substances on gonadal synthetic activities. Gonadal cells were incubated for 24 h in concentrations of methionine-enkephalin, somatostatin and insulin ranging from 10(-4) M to 10(-9) M, in medium 199 supplemented with 6% Ultroser G. Synthesis of DNA and protein by the cultured cells were simultaneously estimated by measuring incorporation of 3H thymidine and 35S methionine. The rate of labelled precursor incorporation was measured using the liquid scintillation technique. All substances tested exerted a dose-dependent effect. The synthetic activity of the cultured cells was highest when the concentration of the peptides added to the medium approximated the physiological levels. Methionine-enkephalin, somatostatin and insulin at 2 x 10(-8) M significantly increased 3H thymidine incorporation, by 62%, 69% and 69% respectively, and protein synthesis by 42%, 57% and 57%, respectively. In the case of juvenile gonadal cultured cells, a similar increase in 3H and 35S incorporation was registered for a 10(-7) M peptide concentration. Both lower and higher peptide concentrations inhibited 3H thymidine and 35S methionine incorporation. Pharmacological studies suggest the existence of methionine-enkephalin and somatostatin-like receptors on snail gonadal cells. These results indicate that our gonadal cell culture model provides a useful tool for the study of the neuroendocrinological control of the activity of snail gonadal cells.

Study on liquid scintillation technique for bioassay of plutonium

Simple, rapid and sensitive methods are very important for the bioassay of plutonium. In this work, modern liquid scintillation technique combined with selective extraction separation and α/β pulse decay discrimination were studied and evaluated for the bioassay of plutonium. After sample decomposition and partial evaporation, cyclohexanone and trialkylphosphine oxide (TRPO) were used for the separation of plutonium from matrix. Several different cocktails were tested for liquid scintillation analysis of urine samples. The minimum detectable activity (MDA) of this method was estimated to be 0.01 Bq/500ml urine with 100 minutes measuring time and 3σ confident level.

A rapid method for determining strontium-90 in contaminated samples of soil and plant

A rapid method for determining 90Sr has been applied to a large number of soil and plant samples contaminated for experimental purposes or following a nuclear accident. The method provides results in 48 h. A stable strontium carrier marked with 85Sr is introduced into a sample immediately before its treatment by HNO 3, HF and H 2O 2. The strontium is extracted from the acid solution by an organic phase composed of crown-6 dicyclohexyl-18, then re-extracted with distilled water and counted using a multi-marked liquid scintillation technique. For a 25 g sample, the strontium extraction yield is 70–85%, and the detection limit using a low background counter is 20 Bq kg −1. The method has been tested on reference materials.

Atmospheric Radon: Origin and Transfer

Abstract Atmospheric indoor and outdoor radon surveys have been performed in several locations of Mexico. In order to estimate the radon transfer from different origins to the atmosphere, soil and ground water, together with the exhalation rate from bare and coated building materials have also been studied. The radon detection was performed with SSNTD, an automatic silicon-based radon monitor and the liquid scintillation technique. The results from several years of monitoring indicate that the atmospheric radon behaviour is different for the countryside as compared with more complex inhabited regions; transfer from soil being inhibited by the specific structures of the cities. The effect of wall coatings reduced from 50% to 90% the radon exhalation from bare building materials. A low radon content was observed in the ground water samples studied.

Determination of Np, Pu and Am in high level radioactive waste with extraction-liquid scintillation counting

A new method for the determination of transuranium elements, Np, Pu and Am with extraction-liquid scintillation counting has been studied systematically. Procedures for the separation of Pu and Am by HDEHP-TRPO extraction and for the separation of Np by TTA-TiOA extraction have been developed, by which the recovery of Np, Pu and Am is 97%, 99% and 99%, respectively, and the decontamination factors for the major fission products (90Sr,137Cs etc.) are 104–106. Pulse shape discrimination (PSD) technique has been introduced to liquid scintillation counting, by which the counting efficiency of α-activity is >99% and the rejection of β-counts is >99.95%. This new method, combining extraction and pulse shape discrimination with liquid scintillation technique, has been successfully applied to the assay of Np, Pu and Am in high level radioactive waste.

Carbon transformations by attached bacterial populations in granitic groundwater from deep crystalline bed-rock of the Stripa research mine.

This paper presents and compares the assimilation rates of CO2 and lactate, and the lactate respiration rates, of attached bacterial populations growing in slowly flowing groundwater (1-3 mm s-1) from deep crystalline bed-rock of the Stripa research mine, Sweden. The bacteria studied grew in anoxic, high-pH (9-10) and low-redox artesian groundwater flowing up through tubing from two levels of a borehole designated V2, 812-820 m and 970-1240 m below ground. Bacteria were allowed to attach to and grow on sterile glass microscope slides in laminar-flow reactors connected to the flowing groundwater. Total numbers of bacteria were counted by acridine orange direct counts. The bacteria grew slowly, with doubling times of 34 d at 10 degrees C for the 812-820 m population, 23 d for the 970-1240 m population at 10 degrees C and 16 d for this population at 20 degrees C. Numbers of attached bacteria reached between 10(6) and 10(7) bacteria cm-2. The populations at the two levels of the borehole were different in physiology as well as in phylogeny and reflected the heterogeneity between the sampling levels. The earlier proposed presence of sulphate-reducing bacteria could not be confirmed. This is discussed in relation to results from 16S rRNA gene sequencing studies. The CO2 assimilation rates (as mol CO2 cm-2 h-1, using liquid scintillation techniques) increased with depth and temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Coxsackievirus B3 infection alters the uptake of 2,3,7,8-tetrachlorodibenzo- p-dioxin into various tissues of the mouse

The tissue uptake of 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) during infection was studies in a mouse model using the common human virus Coxsakievirvs B3 (CB3), adapted here to the mouse. Male A/J-mice were infected with the CB3 virus and subsequently, on days 4 and 7 of the infection, injected with 0.5 μCi [ 14C]TCDD (about 65 μg/kg). A uninfected group was injected with [ 14C]TCDD and served as the control group. Spleen, thymus,heart, pancreas, liver and brain were dissected 24 h after isotope injection, and the [ 14C]TCDD content of the tissues was determined by standard liquid scintillation techniques. On day 7, whole body autoradiography was also performed, 4 h after the isotope injection. Our results clearly show that there is an increased TCDD uptake in the selected tissues during the CB3 infection and that this increased uptake is most pronounced on day 4 post inoculation, which corresponds to the peak of viraemia. It was found that the total tissue concentrations of TCDD were significantly increase on day 4 in the brain, pancrease, heart, spleen and liver. In the spleen, heart and brain they were stil significantly increased on day 7. The considerable metabolic and immunological chanes that generally are caused by infections might explain the changes in accumulation of TCDD. It is possible that the increased uptake of TCDD affects the immune cells involved in repair of inflammatory tissue lesions, thereby affecting the progression of the disease.