Incorporating tritiated water into a 14C-sampling system for quantitative estimation of 14C activity in airborne effluent

The effects of incorporating tritiated water into a ¹⁴C-sampling system in sample preparation and ¹⁴C activity measurement by liquid scintillation counting were investigated. Experiments derived the limit of water content in the prepared sample, and also demonstrated that ¹⁴C activity can be determined without any interference from ³H contamination for a clear-sample solution. The results enabled us to estimate the permissible relative humidity of air required for accomplishing sample preparation and ¹⁴C activity measurement. These showed that for sampling of air with less than the permissible relative humidity, total ¹⁴C activity in airborne effluent can be evaluated accurately without dehumidification of air. This revised version was published online in July 2006 with corrections to the Cover Date.     

Incorporating tritiated water into a 14C-sampling system for quantitative estimation of 14C activity in airborne effluent

The effects of incorporating tritiated water into a ¹⁴C-sampling system in sample preparation and ¹⁴C activity measurement by liquid scintillation counting were investigated. Experiments derived the limit of water content in the prepared sample, and also demonstrated that ¹⁴C activity can be determined without any interference from ³H contamination for a clear-sample solution. The results enabled us to estimate the permissible relative humidity of air required for accomplishing sample preparation and ¹⁴C activity measurement. These showed that for sampling of air with less than the permissible relative humidity, total ¹⁴C activity in airborne effluent can be evaluated accurately without dehumidification of air.The authors would like to thank T. Kozawa, K. Isaka and Y. Adachi of Inspection Development Company Ltd., Y. Hiyama of Zuihou Sangyou Company Ltd., and T. Mizutani, H. Watanabe, M. Takeishi and K. Shinohara of Japan Nuclear Cycle Development Institute for their valuable assistance.     

Incorporating tritiated water into a 14C-sampling system for quantitative estimation of 14C activity in airborne effluent

The effects of incorporating tritiated water into a ¹⁴C-sampling system in sample preparation and ¹⁴C activity measurement by liquid scintillation counting were investigated. Experiments derived the limit of water content in the prepared sample, and also demonstrated that ¹⁴C activity can be determined without any interference from ³H contamination for a clear-sample solution. The results enabled us to estimate the permissible relative humidity of air required for accomplishing sample preparation and ¹⁴C activity measurement. These showed that for sampling of air with less than the permissible relative humidity, total ¹⁴C activity in airborne effluent can be evaluated accurately without dehumidification of air.The authors would like to thank T. Kozawa, K. Isaka and Y. Adachi of Inspection Development Company Ltd., Y. Hiyama of Zuihou Sangyou Company Ltd., and T. Mizutani, H. Watanabe, M. Takeishi and K. Shinohara of Japan Nuclear Cycle Development Institute for their valuable assistance.     

Comparison of two methods for 14C analysis from essential oils using LSC

Natural essential oil sample obtained from basil (Ocinum basilicum), and ethanol sample obtained from wine were measured to determine ¹⁴C specific activity, using two different sample preparation methods, and liquid scintillation counting method. The paper describes the use of two preparation methods, direct measurement method and CO₂ absorption method, and the results obtained for this comparative study. Depending on carbon content of the sample and bubbling time, different correction factors of carbon mass trapped in liquid scintillation cocktail were established for CO₂ absorption method.

     

Stability and reproducibility of gel-suspension samples for the liquid scintillation counting of14C using N-lauroyl-L-glutamic-α,γ-dibutylamide

Stability and reproducibility of gel-suspension samples were investigated in order to evaluate the characteristic feature of the gel-suspension method for¹⁴C activity measurement. Commercially available gelling agent, N-lauroyl-L-glutamic-α,γ-dibutylamide, was used for the gelformatio of the samples. No change of the counting rate for the gel-suspension sample was observed for more than 2 years after the sample preparation. Four samples used for checking the reproducibility of the sample preparation method. The same values were obtained for the counting rate of¹⁴C activity within the counting error. No change of the counting rate was observed for the “re-gelated” sample. These results show that the gel-suspension method is appropriate for the¹⁴C activity measurement by the liquid scintillation method and is useful for a long-term preservation of the sample for repeated measurement.     

Certain aspects of the liquid scintillation measurement of14C in ethanol

In this paper the quenching effect of ethanol in NE 267 liquid scintillation cocktail is investigated when¹⁴C is measured at environmental concentrations. The results obtained show that with a proper selection of amplifier gain and discriminators setting it is possible to achieve efficiency as high as 80% and up to 5 g of sample carbon in the cocktail. This is very important for the direct measurement of¹⁴C for environmental protection purposes in different chemical forms without applying the standard radiocarbon procedures. In all cases the quenching effect of the chemical form in which¹⁴C is being measured has to be determined.     

Nondestructive real-time radioisotope imaging system for visualizing 14C-labeled chemicals supplied as CO2 in plants using Arabidopsis thaliana

We have developed a real-time radioisotope imaging system (RRIS) that can nondestructively trace ¹⁴C-labeled chemicals in plants. In an experiment, after feeding ¹⁴CO₂ to a plant, the plant was fixed inside a box where lighting was regulated, and beta rays emitted from the ¹⁴C in the plant were intermittently imaged using the developed system. As a first step, using a series of standard sources of ¹⁴C, the data depth and detection limits of the ¹⁴C images captured by the RRIS were evaluated for various integral times. As a result, the linearity between the ¹⁴C activity and signal intensity was determined for the range 10³. Next, the linearity was validated using plant (Arabidopsis thaliana) organs, resulting that the linearity was shown in the case of young leaf, but was not maintained in the thick organs, such as a flower, mature leaf, siliques, and stem. Considering the good correlation between the intensity by RRIS and the PSL value by an imaging plate (IP) as well as the relative low energy of beta rays emitted from ¹⁴C, the thickness of the organs would easily affect the quantitativity of the RRIS as well as an IP. Our findings prove that sequential images of ¹⁴C in a living plant sample in a regulated light and air environment can be nondestructively analyzed using the developed system, whose quantitativity is similar to that of an IP.     

Rapid determination of tritium and carbon-14 in urine samples using a combustion technique

Traditionally in bioassay monitoring, ³H determinations in urine have been performed using either direct counting (with or without sample decolourisation) or distillation whilst ¹⁴C has been determined on separate sub-samples following chemical isolation of the carbon from samples. Although these techniques are relatively straightforward they do not permit simultaneous determination of ³H/¹⁴C. For ³H, direct counting can be significantly affected by variations in sample composition/colour resulting in varying degrees of sample quench, does not distinguish between aqueous/organically-bound ³H and is limited to small sample sizes. This study describes the use of purpose built multi-tube combustion furnace for the simultaneous extraction and determination of ³H and ¹⁴C. The technique is insensitive to sample composition and can be adapted to measure Tritiated water (HTO) and organically bound tritium separately. The development of a multi-tube system with integrated cool-down facility permits rapid throughput of high sample numbers and has been proven effective in decommissioning waste characterisation. In addition, the furnace-based technique is capable of processing larger sample sizes, increasing analytical sensitivity and accuracy of dose assessment.     

Estimation of 14CO2 amount in the atmosphere

Carbon from fossil CO₂ emissions, without a significant presence of ¹⁴C, causes dilution of ¹⁴C in the carbon isotopic mixture (Suess effect). Reported ¹⁴C activities are usually connected to radiocarbon amount in the carbon isotopic mixture. Our paper is aimed on estimation of ¹⁴C/¹⁴CO₂ amount in the atmosphere (and its trend), utilizing calculation of a ¹⁴C activity concentration. A parameter connected only with a ¹⁴C quantity in the volume or mass unit of air is not influenced by a fossil carbon amount. Such a “robust” parameter can be influenced only by processes connected with ¹⁴C emissions/depositions.     

Simple measurement of14C in the environment using a gel suspension method

A simple analytical method for environmental¹⁴C with a low background liquid scintillation counter was developed. We used a new gelling agent, N-lauroyl-L-glutamic-α,γ-dibutylamide, for the liquid scintillation counting of¹⁴C as CaCO₃ (gel suspension method). Our procedure for sample preparation was much simpler than that of conventional methods and required no special equipment. The samples prepared with the standard sample of CaCO₃ were measured to evaluate the self absorption of the sample, the optimum condition of counting and the detection limit. Our results indicated that the newly developed technique could be efficiently applied for the monitoring of environmental¹⁴C.     

A simple and reliable monitoring system for 3H and 14C in radioactive airborne effluent

Summary A simple and reliable sampling system for ³H and ¹⁴C in airborne release from nuclear facilities was designed. The sampling system can collect ³H and ¹⁴C simultaneously with a condensation technique using a commercially available cold trap equipment and a CO₂ absorption technique using an organic alkali monoethanolamine solution, respectively. In situ performance tests for the effluent from a reprocessing plant showed that the system has high and stable efficiencies for collecting ³H and ¹⁴C for a one-week batch sampling at a sampling flow rate of 0.4 l ^. min^-1. These collection techniques also provided a simple procedure of following sample preparation for activity measurements by liquid scintillation counting. The detectable concentrations of the proposed monitoring method were 3.0 Bq ^. m^-3 for ³H and 1.6 Bq ^. m^-3 for ¹⁴C, respectively. The sensitivity would be on an acceptable level for routine monitoring of airborne release at nuclear facilities.     

A one-year study of the total air-borne14C effluents from two Swedish light-water reactors,one boiling water- and one pressurized water reactor

The results of a one-year study of the total air-borne¹⁴C effluents from two Swedish light-water reactors, one boiling water reactor (BWR) at Forsmark and one pressurized water reactor (PWR) at Ringhals, are presented. Air emitted from the stacks has been collected continuously over two-week periods and the¹⁴C content in the samples has been analysed using accelerator mass spectrometry (AMS). The¹⁴C activity concentration in the air issuing from the stack of the PWR varied between 2 and 1132 Bq/m³ with a mean value of 200 Bq/m³, while from the BWR the activity concentration varied between 4 and 146 Bq/m³, with a mean value of 95 Bq/m³. The corresponding¹⁴C release rate was 0.27 TBq/GW_el·year for the PWR and 0.48 TBq/GW_el·year for the BWR. During the same period of time, for comparison, the¹⁴C activity in continuously collected air from the stack of the PWR was also measured by liquid scintillation counting. In most cases the results of these measurements were in fair agreement with the corresponding AMS results.     

Piezoresonance sensor for ammonia with polymaleic acid as the sensitive coating

Results of the study of a piezoresonance sensor with polymaleic acid as the sensitive coating for the determination of the concentration of ammonia in air are presented. The influence of the mass of the polymer coating, the flow rate of the carrier gas, and relative humidity on the performance characteristics of the sensor was studied. The mechanism of the interaction of ammonia with the sorbent in the presence of water vapors is proposed based on experimental data and quantum chemical calculation. It is found that the sensor exhibits high selectivity for ammonia in the presence of vapors of saturated and aromatic hydrocarbons. The detection limit for ammonia at the humidity 45–55% is 0.04 mg/m³, which makes it possible to determine ammonia at a level of the maximum permissible concentration for inhabited areas; the concentration characteristic of the sensor is linear in the concentration range 0.04-40 mg/m³.     

Rapid determination of low concentrations of long-lived alpha-emitters in the atmosphere by alpha-spectrometry

A sensitivity of 0.04 to 0.01 pCi/m³ for long-lived α-emitters in air is obtained by α-spectrometry of electrostatically precipitated aerosols in a large Frisch grid ionization chamber after decay of the natural activity for 2 or 4 hrs and 100 min counting. This corresponds to about 0.1 to 0.01 of the maximum permissible concentrations (168 hrs/week) for²³⁹Pu and other toxic long-lived α-emitters. The dependence of the sensitivity of the procedure on variable background contributions by Rn and Tn daughter products was investigated. After²¹²Bi (ThC) has significantly decayed, the sensitivity is 0.0002 to 0.001 pCi/m³ in the 5 MeV region with 1 000 min counting. Direct determination of the natural²¹⁰Po (RaF) content in the atmosphere or the detemination of other α-emitters at that activity level is thus possible without sample preparation or chemical treatment. An example for the low-level detection of transuranium nuclides in the air of a hot laboratory is presented.     

Application of Contactless Impedance Detection to Determination of Substances in Gaseous Phase

A simple cell, consisting of two insulated wire electrodes placed in a PTFE tube through which the test gaseous phase flows, has been applied to capacitively coupled contactless conductometric detection (C⁴D) and determination of water vapour in the air, to examine the possibilities of the use of C⁴D for analyses of gaseous samples. It has been found that the measurement is sufficiently sensitive and reliable for determinations of common concentrations of water in the air. The dynamic characteristics and the signal stability demonstrate that the cell will be suitable for long‐term continuous monitoring of the air humidity. Qualitative tests indicate that vapours of organic solvents can also be monitored. To the authors knowledge, this is the first attempt to use C⁴D in gas analyses.     

The simultaneous determination of Th,Pu, Ra isotopes, 210Pb, 55Fe, 32Si and 14C in marine suspended phases

An efficient and systematic chemical procedure for the simultaneous measurement of Th, Pu, Ra isotopes, ²¹⁰Pb, ⁵⁵Fe, ³²Si and ¹⁴C in the same sample has been developed. This method has been applied successfully to the measurement of these isotopes in oceanic particulate samples collected from several tons of sea water. This procedure should find application in the analysis of geochemical samples.     

Enzymatic syntheses of carbon-14 labeled isotopomers of L-phenylalanine

Convenient and efficient processes are described for the synthesis of L-enatiomers of phenylalanine specifically labeled with carbon-14 in 1-, 2-, and 3-positions of side chain. The method consists of the preparation of the proper isotopomers of cinnamic acid labeled with ¹⁴C and their conversion into L-phenylalanine using enzyme activity. The combined chemical and enzymatic approach allows to produce three different isotopomers of phenylalanine in pure L-optical form labeled with ¹⁴C.     

Distribution of 14C and 3H in low level radioactive wastes generated by wet waste streams from pressurized water reactors

Summary It is impossible to detect ¹⁴C and ³H by direct methods such as γ-spectroscopy because they are pure b-emitters and thus they are classified as hard to measure nuclides (HTM). In this paper the analysis results of ¹⁴C and ³H in the low level radioactive wastes (LLWs), including spent ion exchange resin, evaporated bottom and sludge are presented. The LLWs were generated by three nuclear power plants (NPPs), in Korea all with pressurized water type reactors (PWRs). A simultaneous separation procedure for ¹⁴C and ³H in LLWs was established by wet oxidation-acid stripping. A liquid scintillation analyzer was used for the measurement of ¹⁴C and ³H. It was found that the recovery of ¹⁴C and ³H was 82-99 and 78-103%, respectively, by wet oxidation-acid stripping with diluted standard solutions. At the lowest injection of ¹⁴C and ³H, i.e., at 1.44 Bq for ¹⁴C and 1.22 Bq for ³H, the minimum detectable activity (MDA) of ¹⁴C and ³H was calculated as 0.88 and 0.78 Bq/g, respectively, for the minimum allowable sample weight, using wet oxidation and 16 wt% H₂SO₄ acid. By the wet oxidation-16 wt% H₂SO₄ stripping method no interfering nuclides were detected in the trapping solution of ¹⁴CO₂ and the distillate of ³H. The activity concentration range of ¹⁴C in the analyzed samples, i.e., spent ion exchange resin, evaporated bottom and sludge, was 0.17-110,000, 8.4-1380 and 0.1-10,006 Bq/g, respectively, and that of ³H in the same was from no detectable to 769, 134-14,383 and 0.7-4820 Bq/g, respectively.     

Quantitative Analysis of Carbon-14 Labelled Polychlorinated Biphenyls and Hexachlorobenzene in Biological Samples Using an Oxidative Combustion Method

Abstract

Carbon-14 labelled glucose, polychlorinated biphenyls, and hexachlorobenzene at concentrations of 0.01-1200 nanograms were oxidized in a combustion chamber at 900C. The ¹⁴CO₂ emitted was trapped in an organic base. and its radioactivity measured. Recovery rates of 95-104% were obtained from samples oxidized with mannitol, while recoveries of samples oxidized with dried fish ranged from 93—101%. This method provides an alternate technique of sample preparation for materials that may yield a highly quenched solution following conventional sample preparation procedures for liquid scintillation measurements.     

Advantages of low-background liquid scintillation alpha-spectrometry and pulse shape analysis in measuring222Rn, uranium and226Ra in groundwater samples

Liquid scintillation counting (LSC) and pulse shape analysis (PSA) was used in measuring radon and gross alpha- and beta-activities in groundwater. We used conventional LSC counters for the measurement of radon in water, but low-background LSC spectrometers for the gross activity measurements. The lower limit of detection (LLD) for radon in water is 0.6 Bq/l for a 60 min count with a conventional counter, but 0.1 or 0.2 Bq/l, with the two types of low-background LSC spectrometers equipped with a pulse shape analyser (PSA). The gross alpha and beta activity measurements are made using a simple sample preparation method, PSA of a low background LSC and spectrum analysis. The LLD recorded for gross alpha and beta with the two spectrometers are 0.02 and 0.03 Bq/l and 0.2 and 0.4 Bq/l, respectively, for a 180 minutes count and a 38 ml sample volume. The method also enable the calculation of the U and²²⁶Ra contents in water and indicates the presence of some other long-lived radionuclides (²¹⁰Pb,²²⁸Ra or⁴⁰K). The LLD for U recorded with both spectrometers is 0.02 Bq^–1 and for²²⁶Ra 0.01 Bq·1^–1. The LLDs attained by this LSC method are two orders of magnitude lower than the maximum permissible concentrations set for U and²²⁶Ra.