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A miniature TDCR system dedicated to in-situ activity assay

Johansson, L C; Bakhshandeiar, E; Pearce, A; Collins, S M; Orlandini, P*; Sephton, J P (2014) A miniature TDCR system dedicated to in-situ activity assay. Appl. Radiat. Isot., 87. pp. 287-291.

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Abstract

In the framework of the European Metrology Research Programme (EMRP), the Joint Research Project Metro Fission has a dedicated work package for the development of a portable Triple-to-Double-Coincidence-Ratio (TDCR) system dedicated to in-situ activity measurements of low-energy beta emitters arising from the operation of the next generation of nuclear power plants. In the design phase of the NPL version of the mini-TDCR, a wide range of metrological aspects and detector types was considered. This paper summarizes these aspects of design, in the light of previous experience with the primary TDCR system at NPL. For example, in this miniature version of the TDCR, the optical chamber was simplified and cylindrical geometry was deemed sufficient. There flectivity of the surface was increased by painted layers of Spectraflects, aspecially formulated barium sulphate coating with high reflectivity across a wide range of wavelengths including UV. This option was chosen rather than the high performing and more expensive Spectralons material was used for the primary NPL TDCR. The miniature TDCR system is intended for on-site monitoring and will not require as high a performance as the primary system. Other factors that were considered included sample changing, lighttightness, type of photodetector, method for varying the detection efficiency, shielding and the possible addition of an internal gamma-ray source for determination of the quench parameter of the source. In this version, the sample changing is performed using a piston and an automatic shutter. Significant design effort has been applied to ensure minimal ingress of light from the piston. Efficiency variation is accomplished by increasing the vertical displacement of the vial. Provision has been made to automate this at a later stage. Maximum light transmission to the photo-multiplier tubes is obtained at the 'zero' reference height. Validation
measurements were successfully performed using four different radionuclides: 3H, 241Pu, 63Ni, and 99Tc.

Item Type: Article
Subjects: Ionising Radiation
Ionising Radiation > Radioactivity
Identification number/DOI: 10.1016/j.apradiso.2013.11.035
Last Modified: 02 Feb 2018 13:13
URI: http://eprintspublications.npl.co.uk/id/eprint/6183

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