Performance Assessment of a New Digital Readout Electronics for Nuclear Waste Drum Characterization by Photofission

Characterization of nuclear waste is a critical issue for the global nuclear industry. The importance of such activities is reflected in the EURATOM Horizon 2020 MICADO project aiming at designing mobile and stationary platforms for in-situ characterization of nuclear waste packages by photofission, i.e., fission induced by high-energy photons. Such applications require a corresponding electronics capable of handling specific measurement protocols compatible with various detection systems. However, electronics adapted to the measurement of delayed neutrons from photofission did not encounter significant technological advances since the 1970’s. In this paper, we assess the performances of a new digital readout electronics developed recently in our laboratory for the detection of delayed neutrons from photofission using
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He proportional counters. Such measurements are applied to the characterization of nuclear waste mock-up drums. First, we describe the new digital readout electronics and compare it to the traditional 7820-7821 modules manufactured by Canberra. Second, we carry out measurements at the SAPHIR platform of CEA Paris-Saclay, France, operating at 9 MeV a Linatron M9 electron accelerator, manufactured by Varex Imaging. Validation measurements are conducted on bare samples of uranium or plutonium and the latter placed inside a 220-liter concrete-lined nuclear waste drum. Third, we highlight the advantages and performance enhancements achieved thanks to this new digital readout electronics. Further, this electronic system will allow the investigation of new photofission measurement methodologies such as simultaneous delayed neutron and high-energy delayed gamma counting with a single device in order to push back the current limits encountered in the field of the characterization of radioactive waste packages.