SiLiF Neutron Counters to Monitor Nuclear Materials in the MICADO Project

Abstract

In the framework of the MICADO (Measurement and Instrumentation for Cleaning And Decommissioning Operations) European Union (EU) project, aimed at the full digitization of low- and intermediate-level radioactive waste management, a set of 32 solid state thermal neutron detectors named SiLiF has been built and characterized. MICADO encompasses a complete active and passive characterization of the radwaste drums with neutrons and gamma rays, followed by a longer-term monitoring phase. The SiLiF detectors are suitable for the monitoring of nuclear materials and can be used around radioactive waste drums possibly containing small quantities of actinides, as well as around spent fuel casks in interim storage or during transportation. Suitable polyethylene moderators can be exploited to better shape the detector response to the expected neutron spectrum, according to Monte Carlo simulations that were performed. These detectors were extensively tested with an AmBe neutron source, and the results show a quite uniform and reproducible behavior.

Gamma—Ray Counters to Monitor Radioactive Waste Packages in the MICADO Project

“…The proposed monitoring system is based on detectors which can be easily installed and/or reassembled in different geometrical configurations, as they are mechanically very simple and are based on commercial electronics. The neutron monitoring detectors have already been described in [3]. In this paper we describe the SciFi monitoring detectors devoted to the gamma radiation, following a description of their operational principles and mechanical setup, some simulation results are described followed by the results of the characterization and a few tests of 36 SciFi detector units.…”

“…Following a complete active and passive characterization of the radwaste drums with neutrons and gamma-rays, the project contemplates a longer-term monitoring phase in the Work Package 7 by means of low-cost dedicated detectors for neutrons (named SiLiF [3]) and for gamma-rays (named SciFi). A continuous automatic monitoring of the radwaste drums after their characterization represents an added value in terms of safety and security, and the availability of continuous streams of counting-rate data around each drum would be a comfortable tool toward the transparency, which now more than ever is a relevant topic of the nuclear industry [1, [3][4][5][6][7]. As an evolution of the proof-of-principle systems discussed in [4][5][6][7], the detectors described here will be part of a prototype system which will be installed in a few real radwaste storage sites to prove its effectiveness.…”

The gamma and neutron monitor counters for the MICADO project

“…The operating principle of the SiLiF neutron detector, as a viable alternative to 3 He tubes [9], is straightforward: following a thermal neutron capture by 6 Li, the 7 Li compound nucleus decays into an alpha particle ( 4 He) and a triton ( 3 H), emitted back-to-back with high energy according to the reaction n + 6 Li à 3 H (2.73 MeV) + 4 He (2.05 MeV).…”

“…The MICADO (Measurement and Instrumentation for Cleaning and Decommissioning Operations) Euratom (EU) project is aimed at the full digitization of low-level and intermediate-level radioactive waste (radwaste) management [1,2]. Following a complete active and passive characterization of the radwaste drums with neutrons and gamma-rays, the project contemplates a longer-term monitoring phase in the Work Package 7 by means of low-cost dedicated detectors for neutrons, named SiLiF [3], and for gamma-rays, named SciFi [4]. The proposed system for the online real-time monitoring consists of an array of many radiation sensors to be deployed all around a number of radioactive waste drums, in order to collect counting-rate data in real time and to make them available to a software platform named DigiWaste.…”

“…The proposed system for the online real-time monitoring consists of an array of many radiation sensors to be deployed all around a number of radioactive waste drums, in order to collect counting-rate data in real time and to make them available to a software platform named DigiWaste. A continuous automatic monitoring of the radwaste drums after their characterization represents an added value in terms of safety and security, and the availability of continuous streams of counting-rate data around each drum would be a comfortable tool toward the transparency, which now more than ever is a relevant topic of the nuclear industry [1,[3][4][5][6][7][8]. As an evolution of the proof-ofprinciple systems discussed in [5][6][7][8], the detectors described here will be part of a prototype system which will be installed in a few real radwaste storage sites to prove its effectiveness.…”