The chapter begins with a treatment of the basic theory of liquid scintillation and the interactions of alpha, beta, and gamma rays in liquid scintillator. A description of the basic design and concepts of operation of a liquid scintillation counter is provided. This is followed by a comprehensive treatment of quench effects and the methods of quench correction in liquid scintillation counting, including the internal standard method, sample spectrum, and external standard quench-indicating parameters. A detailed treatment of the preparation and use of quenched standards and quench-correction curves is provided. A discussion of direct DPM methods is also included. This is followed with a treatment on the analysis of X-ray, gamma ray, Auger electron, and positron emitters by liquid scintillation counting (LSC). A detailed discussion of the interferences encountered in liquid scintillation analysis (LSA) including background, quench, radionuclide mixtures, luminescence, and static and wall effects are described, and methods for their correction are discussed. The chapter continues with a treatment on the LSA of multiple radionuclides including dual- and triple-radionuclide analysis techniques and the analysis of more complex mixtures by spectral fitting, unfolding, and interpolation techniques. A detailed discussion of radionuclide standardization by the CIEMAT/NIST efficiency tracing and the triple-to-double coincidence ratio (TDCR) methods is provided. Neutron/gamma-ray measurement and discrimination by LSC are discussed. The use of LSC for the detection and measurement of double beta ( ββ ) decay is provided. A treatment of liquid scintillation schemes for the detection and measurement of neutrinos includes inverse beta decay and charged current interactions. Other liquid scintillation methods that are discussed include microplate scintillation and luminescence counting, PERALS and liquid scintillation alpha-spectrometry with large-area avalanche photodiodes (LAAPD), and simultaneous α / β analysis. Other methods described are the use of plastic scintillators in LSC, scintillation counting in noble liquids, radionuclide identification by LSC, and air luminescence counting. The chapter concludes with a treatment of the methods of assessment of liquid scintillation counter performance and optimization.

Liquid Scintillation Analysis: Principles and Practice

Chapter 7 – Liquid Scintillation Analysis: Principles and Practice

Chlorine (Cl) in the terrestrial environment is of interest from multiple perspectives, including the use of chloride as a tracer for water flow and contaminant transport, organochlorine pollutants, Cl cycling, radioactive waste (radioecology; 36Cl is of large concern) and plant science (Cl as essential element for living plants). During the past decades, there has been a rapid development towards improved understanding of the terrestrial Cl cycle. There is a ubiquitous and extensive natural chlorination of organic matter in terrestrial ecosystems where naturally formed chlorinated organic compounds (Clorg) in soil frequently exceed the abundance of chloride. Chloride dominates import and export from terrestrial ecosystems while soil Clorg and biomass Cl can dominate the standing stock Cl. This has important implications for Cl transport, as chloride will enter the Cl pools resulting in prolonged residence times. Clearly, these pools must be considered separately in future monitoring programs addressing Cl cycling. Moreover, there are indications that (1) large amounts of Cl can accumulate in biomass, in some cases representing the main Cl pool; (2) emissions of volatile organic chlorines could be a significant export pathway of Cl and (3) that there is a production of Clorg in tissues of, e.g. plants and animals and that Cl can accumulate as, e.g. chlorinated fatty acids in organisms. Yet, data focusing on ecosystem perspectives and combined spatiotemporal variability regarding various Cl pools are still scarce, and the processes and ecological roles of the extensive biological Cl cycling are still poorly understood.

/pdf/chlorine-cycling-and-the-fate-of-cl-in-terrestrial-1wile5wxdn.pdf

Chlorine cycling and the fate of Cl in terrestrial environments

The monitoring of long-lived radionuclides is of great importance in the context of the surveillance of nuclear facilities, during their operation as well as during their decommissioning. This is especially true for radionuclides of rather volatile elements, such as chlorine and iodine, the main interest being in 36Cl and 129I. Liquid Scintillation Counting (LSC) is a widely used measurement technique especially for the determination of 36Cl that requires a thorough and selective sample preparation in order to give accurate results. Sample preparation methods frequently employed such as volatilization and/or repeated precipitation steps can be rather elaborate and time consuming. Therefore, an attempt has been made to develop an ‘easy to use’ extraction chromatographic resin that allows extraction, and subsequent separation, of chloride and iodide from pretreated environmental and decommissioning samples for their determination via LSC. First results of the characterization of the resin including D
 w values of Cl−, I− and potential interferents, and of the method development are presented as well as the result of the analysis of a simulated real sample.

Characterization of an extraction chromatographic resin for the separation and determination of 36Cl and 129I

Chlorine-36 (36Cl), a radioisotope of chlorine (Cl) with a half-life of 301,000 years, is present in some types of nuclear waste and is disposed in repositories for radioactive waste. As the releas ...

/pdf/chlorine-cycling-and-fates-of-36cl-in-terrestrial-3tm7d2krfa.pdf

Chlorine cycling and fates of 36Cl in terrestrial environments

The radioactive chlorine isotope, 36Cl, decays with a half-life of 3×105 years by emitting a beta particle (98 %) and by electron capture The aim of this paper is to propose a radiochemical separation method of 36Cl from the other beta-gamma emitters present in low and medium radioactive wastes such as spent ion exchange resins and evaporator concentrates, that arise from Nuclear Power Plants and particularly in the wastes that come from decommissioning activities of graphite reactors, in order to provide data for 36Cl inventory calculations The separation method proposed is based on an oxidation technique where chlorine is trapped by NaOH 36Cl beta emissions are measured by liquid scintillation counting by the dual label technique in order to avoid the contamination produced by 14C which is also trapped by NaOH and which is the main contaminant present in graphite samples The sensitivity of this method is sufficient to achieve the needed thresholds for the radiological characterization of the radioactive materials to which this method can be applied

Radiochemical analysis of chlorine-36

Radiocarbon (14C) is a key radionuclide in the assessment of the safety of underground geological disposal facilities for radioactive wastes, and the understanding of the 14C behavior in stainless steel may lead to a re-evaluation of the near-surface repository for the disposal of wastes containing this radionuclide in high concentrations. To achieve this objective, leaching experiments were planned for two different scenarios. The first is where the leaching solution, NaOH solution of pH ca. 12 in aerobic conditions, simulates the expected conditions in a cement-based near-surface repository over long time periods. The other one uses an acid solution of 1M H3PO4, which has been proved as a high efficiency chemical removal agent of 14C in graphite. The development of both analytical methods and protocols to measure the release of 14C from the activated steel samples and the speciation in the aqueous and gaseous phase has been undertaken as part of the EC CAST (CArbon-14 Source Term) project. Analytical methods, suitable for identifying and quantifying low molecular weight organic molecules, comprise ion chromatography (IC) and gas chromatography coupled to mass spectrometry (GC-MS); they are described for aqueous and gaseous samples, respectively. In this paper the preparation of leaching experiments to measure the release of 14C and the results obtained are described.

14C release from steels under aerobic conditions

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Radiochemical analysis of chlorine-36

14C release from steels under aerobic conditions