Abstract
An advanced neutron detection system for highly localized measurements in nuclear reactor cores was developed and tested in the Laboratory for Reactor Physics and System Behaviour (LRS) at the École polytechnique fédérale de Lausanne (EPFL), Switzerland, in close collaboration with the Detector group of the Laboratory for Particle Physics (LTP) at the Paul Scherrer Institute (PSI), Switzerland. The miniature-size detector is based on the coupling of a ZnS:6LiF scintillator/converter screen of 1 mm2and 0.2 mm thickness with a 10-m optical fiber, the latter being connected to a silicon photomultiplier (SiPM). In this development version, the output signal is processed via analog read-out electronics. The present work documents the characterization of a detection system prototype in the mixedradiation fields o f t he C ARROUSEL f acility a nd i ts t esting in the CROCUS zero-power reactor operated at LRS. The fibercoupled scintillator shows a linear response with the reactor power increase up to 6.5 W (i.e. around 108cm-2s-1total neutron flux), with a s ubsequent l oss o f l inearity d ue t o e lectronic dead time of the analog system. Nevertheless, the detector shows excellent neutron counting capabilities whether compared to other localized detection systems available at LRS, e.g. miniature fission chambers and an sCVD diamond detector.
Highlights
Neutron measurements with high spatial resolution are paramount for the investigation of complex in-core phenomena and for the validation of modern high-fidelity neutron transport codes
The scintillator was connected with an optical fiber to a photomultiplier tube (PMT) that limited the possibility of parallelization of the designed detector
The coupling of a ZnS:6LiF scintillator with a silicon photomultiplier (SiPM) has been already tested by the Detector group of the Laboratory for Particle Physics (LTP) at Paul Scherrer Institut (PSI), Switzerland, in the framework of the upgrade of a neutron diffractometer [11], [12]
Summary
Neutron measurements with high spatial resolution are paramount for the investigation of complex in-core phenomena and for the validation of modern high-fidelity neutron transport codes. The idea to perform extensive investigations of threedimensional static and dynamic in-core phenomena in research reactors [5], [6] triggered the development of advanced neutron detection techniques for highly localized measurements. The coupling of a ZnS:6LiF scintillator with a SiPM has been already tested by the Detector group of the Laboratory for Particle Physics (LTP) at PSI, Switzerland, in the framework of the upgrade of a neutron diffractometer [11], [12] This detection system was not developed for in-core reactor applications, an adapted version of the latter would represent an efficient solution to perform highlyresolved experiments in research reactors and to engineer advanced non-invasive reactor diagnostic techniques [13]. The performances of the fiber-coupled scintillator during in-core measurements are analyzed and compared with the ones of other localized neutron detection systems available at LRS, such as miniature fission chambers and an sCVD diamond detector
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