Periodic Reporting for period 2 - AMHYCO (TOWARDS AN ENHANCED ACCIDENT MANAGEMENT OF THE HYDROGEN/CO COMBUSTION RISK)
Reporting period: 2022-04-01 to 2023-09-30
The main objective of the AMHYCO project is to propose innovative enhancements in the way combustible gases are managed in case of a severe accident in currently operating reactors. AMHYCO will contribute to this objective by improving the understanding of H2/CO combustion risk and incorporating this knowledge into Severe Accident Management Guidelines (SAMGs). This knowledge will be generated within the project by articulating in a concerted way the nuclear safety tools used worldwide with the most advanced simulation techniques and specific experimentation on scenarios where analytical methodologies are not reliable enough yet.
Why is it important? Combustible gases generated in the course of a severe accident are among the most serious threats to the containment integrity, i.e. the last barrier. An appropriate management of the associated risk is paramount to avoid or minimize the potential release of significant amounts of radioactive material to the environment. Since the Fukushima accident, more measurements to reduce the risk of containment failure have been taken from the European Union (EU) Nuclear Power Plants.
The key strategic objectives of the AMHYCO project are:
• To experimentally investigate phenomena that are difficult to predict theoretically such as H2/CO combustion and PARs (Passive Autocatalytic Recombiners) behaviour under realistic accidental conditions, taking into account their interaction with safety systems.
• To improve the predictability of analysis tools Including Lumped Parameter (LP), 3D and Computational Fluid Dynamic (CFD) codes – used for explosion hazard evaluation inside the reactor containment and providing support to Severe Accident Management Guidelines (SAMGs) design and development.
• To improve the SAMG for both in vessel and ex-vessel phases with respect to combustible gases risk management, using theoretical, simulation and experimental results.
Why is it important? Combustible gases generated in the course of a severe accident are among the most serious threats to the containment integrity, i.e. the last barrier. An appropriate management of the associated risk is paramount to avoid or minimize the potential release of significant amounts of radioactive material to the environment. Since the Fukushima accident, more measurements to reduce the risk of containment failure have been taken from the European Union (EU) Nuclear Power Plants.
The key strategic objectives of the AMHYCO project are:
• To experimentally investigate phenomena that are difficult to predict theoretically such as H2/CO combustion and PARs (Passive Autocatalytic Recombiners) behaviour under realistic accidental conditions, taking into account their interaction with safety systems.
• To improve the predictability of analysis tools Including Lumped Parameter (LP), 3D and Computational Fluid Dynamic (CFD) codes – used for explosion hazard evaluation inside the reactor containment and providing support to Severe Accident Management Guidelines (SAMGs) design and development.
• To improve the SAMG for both in vessel and ex-vessel phases with respect to combustible gases risk management, using theoretical, simulation and experimental results.
In WP1 ‘Critical review’, a critical review of the available literature regarding (1) PAR efficiency under ex-vessel conditions, (2) existing PWR SAMGs regarding containment risk management (3) H2/CO combustion and the available engineering correlations for combustion risk estimation, and (4) equipment and instrumentation surveillance under severe accident conditions has been performed. Many experts both from the AMHCYO partners and the Advisory Board were involved in the scientific review. This Work Package has been closed.
In WP2 ‘Selection of severe accident sequences’, the generic containments have been developed and severe accident sequences have been calculated. All the deliverables and milestones have been achieved/submitted, and the lessons learned have been discussed. An outstanding database on H2/CO scenarios of interest for three types of PWR containments (KWU, W and VVER) have been developed. The Work Package is completed now.
In WP3 ‘Experimental investigations’, the experimental programme on combustion was delayed due to the COVID and the difficulties with the supplies after the start of the Ukrainian conflict, but has now been completed. The experiments on flammability limits and turbulent flames were done for the data that had a clear knowledge gap in the literature or no data available at all. For the second task, the PAR experiments in the REKO facilities have been performed to validate numerical PAR models. The deliverable was issued. The WP is completed now, with the final deliverables being under review. The papers are under preparation.
The work in WP4 ‘Full containment analysis’ has started, but had an important influence some initial delay caused by WP2/WP3 delays. This WP has a new Work Plan and has been extended for 6 months (until June 2024). The fundamental preparations, concluding preparations, and applications are all underway. The unmitigated transients for LP models and 3D models are ongoing; while the mitigated transients and sensitivity cases will be done in the next few months. The approach of implementing the insights from WP2 into WP4 is unique, and the papers are already in the pipeline.
The WP5 ‘Enhancement of severe accident management guidelines’ has not yet officially started. However, the first discussions on what is relevant for the SAMGs have taken place. Some preliminary works have started, namely in: H2, P and T instrumentation location ; FCVS operational details ; and Spray actuation times & criteria.
In WP6 ‘Dissemination, communication, education and training’, many activities took place: workshops with PhD students, mobility programme, funding of the PhD thesis, defence of 1 PhD thesis, AMHYCO students being awarded for their work, participation at many events and conferences. In total, 22 conference papers and 2 journal papers were published.
In WP2 ‘Selection of severe accident sequences’, the generic containments have been developed and severe accident sequences have been calculated. All the deliverables and milestones have been achieved/submitted, and the lessons learned have been discussed. An outstanding database on H2/CO scenarios of interest for three types of PWR containments (KWU, W and VVER) have been developed. The Work Package is completed now.
In WP3 ‘Experimental investigations’, the experimental programme on combustion was delayed due to the COVID and the difficulties with the supplies after the start of the Ukrainian conflict, but has now been completed. The experiments on flammability limits and turbulent flames were done for the data that had a clear knowledge gap in the literature or no data available at all. For the second task, the PAR experiments in the REKO facilities have been performed to validate numerical PAR models. The deliverable was issued. The WP is completed now, with the final deliverables being under review. The papers are under preparation.
The work in WP4 ‘Full containment analysis’ has started, but had an important influence some initial delay caused by WP2/WP3 delays. This WP has a new Work Plan and has been extended for 6 months (until June 2024). The fundamental preparations, concluding preparations, and applications are all underway. The unmitigated transients for LP models and 3D models are ongoing; while the mitigated transients and sensitivity cases will be done in the next few months. The approach of implementing the insights from WP2 into WP4 is unique, and the papers are already in the pipeline.
The WP5 ‘Enhancement of severe accident management guidelines’ has not yet officially started. However, the first discussions on what is relevant for the SAMGs have taken place. Some preliminary works have started, namely in: H2, P and T instrumentation location ; FCVS operational details ; and Spray actuation times & criteria.
In WP6 ‘Dissemination, communication, education and training’, many activities took place: workshops with PhD students, mobility programme, funding of the PhD thesis, defence of 1 PhD thesis, AMHYCO students being awarded for their work, participation at many events and conferences. In total, 22 conference papers and 2 journal papers were published.
In the second reporting period, the project continued building competencies of the younger generation in the nuclear industry and disseminating the first results widely to the general public and the scientific community. The project has included several young researchers (PhD students, postdocs) in the teams, which will have a long-term impact on the promotion of nuclear research among young students and reinforcement of skills and competencies of the individuals engaged in the project. The PhD students have started to work on their thesis, one thesis was defended and others are scheduled for being defended in the last reporting period. The mobility scheme has started, and so far 4 mobility actions have been completed. In total, 22 conference papers and 2 journal articles published. In the remaining period, the consortium will put its efforts into publishing all of the results generated by the project.