Abstract
The DISCOMS project (Distributed Sensing for Corium Monitoring and Safety) aimed at providing innovative solutions not requiring local electrical power supplies, for remote monitoring of a severe nuclear accident. The solutions are based on both long length SPNDs (Self Powered Neutron Detectors) and on distributed OFSs (Optical Fibre Sensors) capable to detect the onset of a severe accident, the corium pouring on the containment building concrete basemat, and its interaction with the concrete floor under the reactor vessel, until it spreads in the core catcher (EPR case). This paper mainly focuses on these last three detection targets achievable with distributed OFSs. It is based on the results of a Molten Core & Concrete Interaction (MCCI) experiment, namely VULCANO, held in June 2018 with a concrete crucible equipped with overall ~ 180 m long optical fibre sensing cables. This small scale experiment (50 kg of prototypical corium) has demonstrated the ability of distributed OFSs to remotely provide useful data during the MCCI run: i) temperature profiles images up to about 580°C (single wavelength Raman DTS reflectometer) until cooling down to room temperature, ii) high spatial-resolution frequency shifts profiles, due to combined (non-selective) strain and temperature influences (Rayleigh OFDR and Brillouin reflectometers), and iii) cables lengths ablated by the corium on sections weakened by the temperature (Raman DTS, Rayleigh OFDR, telecom and photon counting reflectometers).
Highlights
IN March 2011, an 9.1 magnitude earthquake struck off the north-east coast of Japan, and caused a powerful tsunami, with waves greater than 30 m height in some places
This work further led to a new and dedicated research program, the RSNR [3], to stimulate and fund new R&D topics in nuclear safety, with four main objectives: i) analyse the conditions that previously led to nuclear accidents, including the Fukushima-Daiichi event, taking into account the first conclusions of the Complementary Safety Assessments that followed [4], ii) analyse the severe accident management procedures to be considered by licensees and public authorities, for all major nuclear accidents to date, iii) analyse their impact, with regard to radioactive material releases, on human health and on the environment, and iv) enhance nuclear facilities robustness to extreme situations
Considering the optical fibre length as an image of the MCCI, ablated depths were compliant with thermocouples indications (Fig. 13)
Summary
IN March 2011, an 9.1 magnitude earthquake struck off the north-east coast of Japan, and caused a powerful tsunami, with waves greater than 30 m height in some places. These innovative means rely on passive sensors, namely long lengths (up to 6 m long) ex-core SPNDs (Self Powered Neutron Detectors) [6] and distributed OFSs (Optical Fibre Sensors): SPNDs would be installed in the reactor pit whereas OFSs would be located at several depths in the concrete floor, and below the core catcher (EPR). The global cost for the society of a severe nuclear accident which could occur in France has been estimated to 120 G€, with 11 G€ related to contaminated territories, depending on the scenario [7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
