• Applied Biological Chemistry
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• v.18 no.2
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• pp.56-60
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• 1975

A rapid method for the measurement of the absolute activity of carbon-14 in cotyledons and root of etiolated pea seedlings has been developed. Fresh tissue was frozen in liquid air, ground and suspended in gel phosphor and subjected to measurement for its radioactivity by liquid scintillation counter. Apparent activity of the suspended tissue sample calculated by counting efficiency value obtained by internal standardisation, was found to be related to absolute activity of the tissue, determined by flask combustion technique, by a constant factor. Once this factor is determined experimentally, analysis of C-14 lebelled tissue involves only fairly simple suspension counting by liquid scintillation counter. Present method appears to be applicable to other tissues tagged with C-14.

• Nuclear Engineering and Technology
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• v.35 no.2
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• pp.165-170
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• 2003

We developed an improved 3-PM liquid scintillation counting (3-PM LSC) method in which three detectors can be displaced to back and forth directions, and a data acquisition system being able to provide the values for all parameters required for the method. The detectors are entirely located in a 20-mm lead chamber of an inner diameter of 500 mm. A saw-toothed gear ties up all detectors so as to move them uniformly, up to 50 mm with unit of 1 mm. The data acquisition system was designed in an integrated circuit to perform the necessary works such as fast amplification, discrimination, coincidence and logic analysis. It generates values of nine parameters among twelve's generated in the 3-PH LSC method. The dead time of each counting channel is of extending type, valving from 10 to 100 $mutextrm{s}$. We measured the TDCR values with an unquenched liquid scintillation source 1"C by displacing the detectors with a step of 2.5 mm away from counting vial. Their values were derived on the range from 0.9 to 0.6. The extent is three times wider than those regions observed by applying the defocalization technique.ique.

• Analytical Science and Technology
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• v.15 no.1
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• pp.20-25
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• 2002

An accurate and simple analytical technique for $^{89}Sr$ and $^{90}Sr$, overcoming the demerits of the conventional method, has been developed with extraction chromatography and liquid scintillation counting. The Sr fraction was separated from hindrance elements with oxalate coprecipitation or cation exchange resin and purified with Sr-Spec column. With liquid scintillation counter, $^{89}Sr$ was measured by Cerenkov radiation method, and $^{90}Sr$ was measured by spectrum unfolding method. The developed radioactive strontium separation method was validated by application to the IAEA-reference material (IAEA-375, Soil) and radioactive waste samples.

• Journal of Radiation Protection and Research
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• v.21 no.2
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• pp.91-98
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• 1996

An optimized method for determining beta-emitting $^{241}Pu$ in the presence of alpha-emitting nuclides was developed using a liquid scintillation counting system. Pulse shape analysis (PSA) level was set using pulse-shape discrimination method and the $^{241}Pu$ counting channel was adjusted for maximum value of figure of merit using the 241pu standard source. The volume of scintillant was determined for the maximum value of counting efficiency. This optimized method has been applied to environmental samples to measure concentration of $^{241}Pu$ in soils and mosses. Also it has been identified the origin of Pu deposited in Korea from the activity ratio of $^{241}Pu/^{239,\;240}Pu$.

• Journal of Radiation Protection and Research
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• v.45 no.2
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• pp.76-80
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• 2020

Background: To improve the measurement accuracy of liquid-scintillation counting for activity standardization, it is necessary to significantly reduce the background caused by thermal noise or after-pulses. We have therefore improved a movable 3 photomultiplier (3PM)-γ coincidence-counting method using the logical sum of three double coincidences for β events. Materials and Methods: We designed a new data-acquisition system in which β events are obtained by counting the logical sum of three double coincidences. The change in β-detection efficiency can be derived by moving three photomultiplier tubes sequentially from the liquid-scintillation vial. The validity of the method was investigated by activity measurement of ¹³⁴Cs calibrated at the Korea Research Institute of Standards and Science (KRISS) with 4π(PC)β-γ(NaI(Tl)) coincidence counting using a proportional counter (PC) for the β detector. Results and Discussion: Measurements were taken over 14 counting intervals for each liquidscintillation sample by displacing three photomultiplier tubes up to 45 mm from the sample. The dead time in each β- and γ-counting channel was adjusted to be a non-extending type of 20 ㎲. The background ranged about 1.2-3.3 s^-1, such that the contributions of thermal noise or after-pulses were negligible. As the β-detection unit was moved away from the sample, the β-detection efficiencies varied between 0.54 and 0.81. The result obtained by the method at the reference date was 396.3 ± 1.7 kBq/g. This is consistent with the KRISS-certified value of 396.0 ± 2.0 kBq/g within the uncertainty range. Conclusion: The movable 3PM-γ method developed in the present work not only succeeded in reducing background counts to negligible levels but enabled β-detection efficiency to be varied by a geometrical method to apply the efficiency extrapolation method. Compared with our earlier work shown in the study of Hwang et al. [2], the measurement accuracy has much improved. Consequently, the method developed in this study is an improved method suitable for activity standardization of β-γ emitters.

• Journal of Korean Society for Atmospheric Environment
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• v.10 no.E
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• pp.299-302
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• 1994

At a nuclear power plant, environmental radioactivity monitoring is routine work for the radiation safety management For the environmental monitoring of tritium($^3$H) activity in water sampled liquid scintillation counting( LSC) method is applied to measure low- energy beta activity from tritium in the samples. The $^3$H activity is measured using the BECKMAN 5801 system at the KRISS( Korea Research Institute of Standards and Science) for evaluating the lower limits of detection( LLD) of $^3$H measurement and the measuring capability of low-level $^3$H activity at four nuclear Power Plant sites. The LSC systems used for low-level $^3$H activity measurements at the nuclear Power Plants are confirmed to satisfy throughout an intercomparison study under the experimental arrangements by the KRISS.

• Nuclear Engineering and Technology
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• v.36 no.2
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• pp.121-126
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• 2004

3-PM liquid scintillation counting using the geometry-efficiency variation technique has been applied to the activity measurement of $^{204}T1$, which decays to $^{204}Hg\;and\;^{204}Pb\;by\;{\beta}^-$ and E.C., respectively. The TDCR values K have been derived over a wide range, 0.78 < K < 0.97, by displacing the detectors up to 50 mm away from an unquenched liquid scintillation sample $^{204}Tl$. The derived plots of the logic sums of double coincidences $N_D(K)$ very K vary linearly in the observed regions. The fractions of losses due to electron capture decay have been taken into account by employing a PENELOPE Monte Carlo simulation. The calibrated activity is 102.3 kBq at a reference date of July 1st, 2002 (UT) with a combined uncertainty of $0.63\%$. This is consistent with the value determined by means of the CIEMAT/NIST method at KRISS.

• Journal of Pharmaceutical Investigation
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• v.25 no.3
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• pp.223-226
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• 1995

A new method to study water uptake into biodegradable polymer was developed. Polymer was gently mixed with the tritiated buffer and the radioactivity level of the polymer due to water uptake was measured by liquid scintillation counting. The rate of water uptake was estimated from the plot of the amount of water in the device as a function of time. The technique used in this study is particularly useful for estimating water uptake of biodegradable polymers which were difficult to study by other techniques such as weight gain used for hydrogel.

• Journal of Radiation Protection and Research
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• v.20 no.2
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• pp.103-115
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• 1995

For the determination of $^{222}Rn$ in water by a very simple and time saving liquid scintillation counting method that does not require any chemical separation, an optimum analytical condition has been investigated. The optimum pulse shape analysis(PSA) level for the measurement of $^{222}Rn$ using LKB 1220 Quantulus liquid scintillation counter was 110 for Optiphase HiSafe3 cocktail and 90 for toluene-based cocktail. The counting efficiencies of $^{222}Rn$ in the window covering u spectra using Optiphase HiSafe3 cocktail were 282.2% for glass vial and 271.6% for Teflon vial, whereas the counting efficiencies in toluene-based cocktail were 262.3% and 247.5% for glass and Teflon vials, respectively. The minimum detectable activity(MDA) in the u window for a 60-min measurement with a Teflon vial using Optiphase HiSafe3 cocktail was $0.30Bq/{\iota}$. The analytical method studied from this work was also applied to the determination of $^{222}Rn$ in some groundwater and hot spring water samples.

• Journal of Radiation Protection and Research
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• v.18 no.2
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• pp.17-25
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• 1993

Beta ray spectra of $^3H,\;^{14}C\;and\;^{36}Cl$ in liquid scintillation counting system have been calculated using the Monte Carlo method by which physical behaviors of particle transport in medium were simulated. The calculations have been carried out on the basis of beta rays being slowing down according to the continuous slowing down approximation(CSDA) model. Beta rays generated in simulation geometry were traced until they lost their energy below 0.3keV that in known to be the detection limit in the liquid scintillation counter. Scintillator solution in which pure beta emitting radionuclides were dissolved uniformly was assumed to be bottled in the shape of right circular cylinder with 12.5mm in radius and 35mm in height. The comparison of the calculated and measured results showed satisfactory agreement between those two, with slight discrepancy due to self quenching in the case of lower energy of emitted beta particles in the solution.