C. Fréchou

Bio: C. Fréchou is an academic researcher from French Alternative Energies and Atomic Energy Commission. The author has contributed to research in topics: Isotope dilution & Liquid scintillation counting. The author has an hindex of 3, co-authored 3 publications receiving 64 citations.

Measurement of 36 Cl in nuclear wastes and effluents: Validation of a radiochemical protocol with an in-house reference sample

Abstract: 36Cl is a beta-emitter with a very low specific activity. It is produced during the irradiation of nuclear fuel, in the reactor core of power plants, from neutron capture by stable 35Cl that may be present at trace level in any part of the irradiated material. Due to its long half-life (T1/2 = 3.01 . 105 y), 36Cl may be significant in impact assessment studies of disposal sites of nuclear wastes. Considering these different elements, the National Radioactive Waste Management Agency (Andra-France) requests information on the 36Cl content of the waste packages destined to be stored at Andra sites. As for other halogens, the measurement of 36Cl is a difficult analytical task in view of its potential losses during the different chemical steps and also because of the lack of international certified reference material needed to validate the chemical and measurement procedures. This paper describes the methodology processed to constitute an in-house solid reference sample with a known content of stable and radioactive chlorine. The original radiochemistry developed to extract 36Cl from solid samples and purify it before a liquid scintillation counting is explained. The comparison of the results given by this radiochemical protocol and other methods allow its validation. The replication of the measurements on the constituted reference materials gives a repeatability around 8% at a confidence level of 95% that is very close to the calculated combined uncertainty value.

Use of single-collector and multi-collector ICP-mass spectrometry for isotopic analysis

Abstract: This article is intended as a tutorial review on the use of single-collector and multi-collector ICPMS for isotope ratio determination. The monitoring and quantification of both induced and natural differences in the isotopic composition of target elements is covered. The capabilities of various types of ICPMS instruments for isotope ratio measurements are addressed and issues, such as the occurrence of mass discrimination and detector dead time effects and appropriate ways of correcting for the biases they give rise to are discussed. Applications relying on induced changes include elemental assay via isotope dilution, tracer experiments with stable isotopes, aiming at a more profound insight into physical processes or (bio)chemical reactions, and nuclear applications. Attention is also paid to the origin of natural variations in the isotopic composition, with focus onto the mechanisms behind the isotopic variation for those elements for which isotopic analysis can be realized using ICP-mass spectrometry, i.e. the occurrence of radiogenic nuclides formed as a result of the decay of naturally occurring and long-lived radionuclides and mass fractionation as a result of thermodynamic and kinetic isotope fractionation effects. Geochronological dating via the Rb–Sr, U, Th–Pb, and Pb–Pb methods is briefly explained and also the use of Sr and Pb isotopic analysis for provenance determination studies is covered. Subsequently, applications based on isotopic analysis of elements showing a much narrower range of variation as a result of isotope fractionation are described. Next to provenance studies, such applications include the use of isotope ratios in geochemical, environmental and biomedical studies. Although it is not the intention to comprehensively review the literature, several examples of published applications are used to illustrate the capabilities of both single-collector and multi-collector ICPMS in this context. Thereby, attention is devoted both to widely accepted applications and to more ‘exotic’ applications, aiming at an extension of the application range.

Plasma source mass spectrometry for radioactive waste characterisation in support of nuclear decommissioning: a review

Abstract: The efficient characterization of nuclear waste materials represents a significant challenge during nuclear site decommissioning, with a range of radionuclides requiring measurement in varied and often complex sample matrices. Of the available measurement techniques, inductively coupled plasma mass spectrometry (ICP-MS) has traditionally been applied to long-lived radionuclides, particularly in the actinide series. With recent advances in the technique, both the sensitivities achievable and number of radionuclides potentially measurable has expanded, with the reduced procedural time offering significant economic benefits to nuclear site waste characterization compared with traditional radiometric (typically alpha and beta spectrometry) techniques. This review provides a broad assessment of recent developments, improvements in capability and describes the advantages and drawbacks of ICP-MS with regards to sample introduction and instrument design. The review will be of interest to international agencies concerned with nuclear decommissioning as well as nuclear site laboratories, project managers and sites involved in environmental monitoring and nuclear forensics.

Liquid Scintillation Analysis: Principles and Practice

Abstract: 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.