In\ situ$ gas monitoring by fiber-coupled Raman spectrometry for H$_2$-risk management in nuclear containment during a severe nuclear aAccident

• Published in: IEEE transactions on nuclear science Vol. 67; no. 4; pp. 617 - 624
• Main Authors: Magne, Sylvain, Nehr, Simon, Buet, Xavier, Bentaïb, Ahmed, Porcheron, Emmanuel, Grosseuvres, Romain, Studer, Etienne, Scarpa, Roberta, Abdo, Daniele, Widloecher, Jean-Luc, Norvez, Olivier, Chaumeix, Nabiha, Dhote, Julien, Freyssinier, Mathilde, Ruffien-Ciszak, Audrey
• Format: Journal Article
• Language: English
• Published: Institute of Electrical and Electronics Engineers 01-04-2020
• Subjects: Engineering Sciences; MISTRA facility; hydrogen release; Optical Fiber Sensor; Pressurized Water Reactor; Instrumentation; nuclear accident; detonation; Qualification; core-coolant water reaction; laser; nuclear Instrumentation; optical fiber; spectrometry; corium; deflagration; Raman spectrometry; Nuclear Power Plant; molten corium-concrete interaction; ionizing radiation; autocatalytic recombiner; radioactivity
• ISSN: 0018-9499; 1558-1578
• DOI: 10.1109/TNS.2020.2965622

During a severe nuclear accident leading up to core melting, molten corium-concrete interaction (MCCI) and core-coolant water reaction both release large amounts of hydrogen (H$_2$ ) gas in the containment atmosphere. According to the Shapiro-Moffette ternary diagram and depending on local partial pressures of H$_2$ , air, and water vapor, deflagration/detonation may occur with potential deleterious impact over equipment and structures. CO and CO$_2$ are also of interest, as revealing gases for MCCI. Pressurized Water Reactors (PWRs) of French Nuclear Power Plants (NPPs) are equipped with passive autocatalytic recombiners (PARs), partly mitigating the H$_2$ risk. However, the H$_2$ -risk management strategy may be significantly improved by performing in situ monitoring of H$_2$ , O$_2$ , N$_2$ , H$_2$O, CO, and CO$_2$ partial pressures at several locations inside the containment, to account for potential local combustion risk. Raman spectrometry (RS) involves only one laser and spectrometer equipped with a 2-D charge-coupled device (CDD). Raman probes are chemically selective and may be radiation-hardened. Custom-made fiber-coupled Raman probes, linked with a readout unit, were qualified in a climatic chamber, a flame-propagation tube, a $^{60}$Co irradiation cell, a 3-D shaking table, a steam jet and the MISTRA facility (1/10 reduced-scale containment mock-up dedicated to thermo-hydraulic tests).