Title: Calibration, characterisation and Monte Carlo modelling of a fast-UNCL
Authors: TAGZIRIA HamidBAGI JanosPEERANI PaoloBELIAN Anthony
Citation: NUCLEAR INSTRUMENTS \& METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT vol. 687 p. 82-91
Publisher: ELSEVIER SCIENCE BV
Publication Year: 2012
JRC N°: JRC72922
ISSN: 0168-9002
URI: http://publications.jrc.ec.europa.eu/repository/handle/JRC72922
DOI: http://dx.doi.org/10.1016/j.nima.2012.05.091
Type: Articles in Journals
Abstract: This paper describes the calibration, characterization and Monte Carlo modeling of a new IAEA Uranium Neutron Collar for LWR fuel (UNCL), which can be operated in both Passive and Active mode and employs up to 44 3He tubes at 10 atm pressure (in passive mode). Thus it can be operated in fast mode due its higher efficiency than the standard UNCL. Furthermore, it has an adjustable internal cavity which allows the measurement of varying sizes of fuel assemblies such as WWER-1000, WWER440, PWR, BWR. It is intended to be used (in active and fast modes) by the inspectorate for the determination of the 235U content in fresh fuel assemblies especially in cases where high concentrations of burnable poisons cause problems with accurate assays. A campaign of measurements has been carried out at the JRC-Ispra Performance Laboratories (PERLA) using various radionuclide neutron sources (252Cf, 241AmLi and PuGa) and our BWR and PWR reference assemblies, in order to calibrate and characterise the counter as well as assess its performance and determine its optimum operational parameters. Furthermore, the fast-UNCL has been extensively modelled at JRC using the Monte Carlo code, MCNP-PTA, which simulates both the neutron transport and the coincidence electronics. The model has been well validated using our measurements which agreed well with calculations. The WWER1000 fuel assembly for which there are no representative reference materials for an adequate calibration of the counter, has also been modelled and the response of the UNCL to these fuel assemblies has been simulated. Subsequently numerical calibrations curves have been obtained for the above fuel assemblies in various modes (fast and thermal), the sensitivity of the counter to fuel rods substitution as well as other important aspects and the parameters of the fast-UNCL performance have been investigated and assessed.
JRC Institute:Institute for Transuranium Elements

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