Lars Frosig Østergaard

Bio: Lars Frosig Østergaard is an academic researcher from Technical University of Denmark. The author has contributed to research in topics: Liquid scintillation counting & Matrix (chemical analysis). The author has an hindex of 2, co-authored 2 publications receiving 101 citations.

Determination of 36Cl in nuclear waste from reactor decommissioning.

Abstract: An analytical method for the determination of 36Cl in nuclear waste such as graphite, heavy concrete, steel, aluminum, and lead was developed. Several methods were investigated for decomposing the samples. AgCl precipitation was used to separate 36Cl from the matrix elements, followed by ion-exchange chromatography to remove interfering radionuclides. The purified 36Cl was then measured by liquid scintillation counting. The chemical yield of chlorine, as measured by ICPMS, is above 70% and the decontamination factors for all interfering radionuclides are greater than 106. The detection limit of this analytical method for 36Cl is 14 mBq. The method has been used to determine 36Cl in heavy concrete, aluminum, and graphite from the Danish DR-2 research reactor.

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.

Radiochemical analysis of radionuclides difficult to measure for waste characterization in decommissioning of nuclear facilities

Abstract: Some radiochemical analytical methods for the determination of important beta-radionuclides for decommissioning are presented. An analytical method is briefly described, which is used for the determination of 3H and 14C in steel and aluminum by combustion using commercial oxidizer. A leaching method was developed for the determination of 3H in the contaminated silica gel. A simple distillation method is presented for the determination of 14C in heavy water and wastewater sample. A method developed for the simultaneous determination of 3H, 14C, 36Cl, 55Fe, 63Ni, 41Ca and 129I in concrete, graphite, aluminium, lead, and steel is presented. The developed methods have been successfully used to analyse various materials for characterization of the waste during the decommissioning of Danish nuclear reactors.

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.