$In\ situ$ gas monitoring by fiber-coupled Raman spectrometry for H$_2$-risk management in nuclear containment during a severe nuclear aAccident
Résumé
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).
Mots clés
- Qualification
- Optical Fiber Sensor
- nuclear Instrumentation
- Instrumentation
- MISTRA facility
- optical fiber
- spectrometry
- laser
- Raman spectrometry
- autocatalytic recombiner
- Pressurized Water Reactor
- Nuclear Power Plant
- detonation
- deflagration
- hydrogen release
- core-coolant water reaction
- molten corium-concrete interaction
- corium
- ionizing radiation
- radioactivity
- nuclear accident
Domaines
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