Abstract
The present article provides an overview of the design of a three-dimensional (3D) full-core mapping system for the CROCUS reactor, operated at the École polytechnique fédérale de Lausanne (EPFL), Switzerland. The system is composed of 149 miniature neutron detectors distributed within the core double lattice at three main axial levels. The miniature detector technology is based on the optimization of the well-proven coupling of a miniature ZnS:6LiF(Ag) scintillator to a state-of-the-art silicon photomultiplier (SiPM) via jacketed optical fibers. The challenges in the mechanical design, the detector optimization, the core criticality, and the development of the acquisition electronics are strongly interconnected and their combination is addressed in this article. The 3D full-core mapping system is foreseen to be installed in CROCUS in autumn 2021 and it will pave the way for the investigation of 3D dynamic phenomena in nuclear reactor cores.
Highlights
THE interest in studying space-dependent neutronics phenomena in nuclear reactor cores has grown in recent years among the scientific community
The 3D core-mapping system designed for the CROCUS reactor, composed by 149 optimized miniature neutron detectors and the mechanical structure, will have an impact on the reactor operations in terms of criticality
The first prototype model of miniature neutron detector described in Section III.A was using a processing electronics developed at Paul Scherrer Institut (PSI) to transform silicon photomultiplier (SiPM) currents into a stream of photon events, and an analog read-out electronics assembled at LRS to count and discriminate thermal neutron events from the background
Summary
THE interest in studying space-dependent neutronics phenomena in nuclear reactor cores has grown in recent years among the scientific community. First of all, positioning a great number of in-core neutron detectors requires good reactor accessibility and inter-pin spaces fitting neutron detectors of a suitable size. Both the selected detectors and their acquisition chain must be produced in series at an acceptable cost. In this framework, the zero-power research reactor CROCUS, operated at the École polytechnique fédérale de Lausanne (EPFL) was selected as a perfect candidate for the installation of a 3D full-core mapping system. The digital acquisition electronics, developed in-house at LRS and tailored for the 3D core-mapping system, is presented
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