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Thirty years of Research on Hydrogen Explosion Hazards in the Nuclear Industry Joseph E. Shepherd California Institute

Why am I here?. March 28, 1979 TMI-2. Events Driving Research Priorities. Some Major Research Programs. Recurrent Topics. Composition and distribution of explosive atmospheres Ignition sources and likelihood of ignition in passive systemsIs deliberate ignition or recombination effective in eliminating hazards?What is the most severe explosion hazard possible?Evaluation of structural loading and thermal response of equipment .

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Thirty years of Research on Hydrogen Explosion Hazards in the Nuclear Industry Joseph E. Shepherd California Institute

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    1. Thirty years of Research on Hydrogen Explosion Hazards in the Nuclear Industry Joseph E. Shepherd California Institute of Technology Pasadena, CA 91125 ANS Meeting panel on Managing Hydrogen Hazards in DOE Facilities: Research and Testing Needs for Safe Nuclear Operations American Nuclear Society 2010 Annual Meeting San Diego, CA June 15, 2010

    3. Events Driving Research Priorities

    4. Some Major Research Programs

    5. Recurrent Topics Composition and distribution of explosive atmospheres Ignition sources and likelihood of ignition in passive systems Is deliberate ignition or recombination effective in eliminating hazards? What is the most severe explosion hazard possible? Evaluation of structural loading and thermal response of equipment

    6. Towards a Standardized Approach Systematic evaluation of explosion hazards Flammability limits Detonation scaling (cell width) Deflagration consequences Detonation consequences Transition from Deflagration to Detonation (DDT) Structural response to explosions Elastic response Plastic deformation Failure of components due to rupture or thermal effects

    7. Gaseous explosions vs. high explosives Extensive results are available for high explosive structural response, fewer for gasess Structural loading Impulsive approximation of limited value for gases Traveling loads and low-frequency structural response for piping systems important for gases Dispersal of material High explosive correlations not appropriate Little or no data for gaseous explosion case ASME Code Case for high explosives

    8. Dispersal by Gaseous Explosions

    9. PWR/BWR Lessons Learned Scaling of explosion phenomena Deflagrations outcome relatively independent of scale: flammability limits depend on composition only Detonation and transition to detonation strongly dependent on scale: detonation limits depend strongly on geometry, size, and ignition source Deflagration-to-detonation transition (DDT) Large-scale experiments are needed to quantify DDT hazards in reactor containment geometries Detonations can be initiated and propagate at much lower concentrations in large scale than small scale: 10.5% H2-air detonation, DDT in 11% H2-air with 10% steam

    10. Detonation Cell Widths

    11. Detonation Cell Size Data available for many mixtures Fuel-Oxidizer-diluent Cataloged in Caltech database

    12. Turbulent Jet Initiation of Detonation

    13. Deflagration to detonation

    14. DDT Onset Minimum Size

    15. Explosion Regimes

    16. 3013 Containment System

    17. DDT in very small gaps for H2-O2

    18. Special Issues in Piping Systems Two types of loads : Short period hoop oscillation Long period beam bending modes Significant in piping systems Traveling load creates series of impulses at bends, tees and closed ends Dynamic pressure must be accounted for in computing magnitude of impulse Strains due to bending comparable or larger than hoop strains

    19. Piping System Response

    21. Hoop and axial strains with pressure

    22. Peak Strains in H2-N20 DDT testing

    23. H2-O2

    24. Lessons Learned –Piping Testing Structural modeling required developing forcing functions to simulate Pressure-time history due to detonation propagation Forces due to detonation propagation through bends Reflection of detonation wave and propagation in water filled sections Forces due to detonation propagation through tees Forces on cantilever supports Validated models developed to and applied Complete piping system with multiple bends, supports, a tee, and dead ends.

    26. Some Outstanding Issues Explosion limits for small volumes of explosive gases embedded in waste Response of piping systems partially filled with waste Including strain rate effects in structural response Estimating rupture and fragmentation thresholds Dispersion due to gaseous explosion Standardize analysis methods for safety studies Develop code cases and guidelines for ASME BPV code and B31 piping code

    27. Codes and Standards ASME BOILER AND PRESSURE VESSEL SECTION VIII, DIVISON 3 SPECIAL WORKING GROUP ON HIGH PRESSURE VESSELS (SWG HPV) TASK GROUP ON IMPULSIVELY LOADED PRESSURE VESSELS Created Code Case 2564 Covers design of high explosive containment vessels No treatment of gaseous explosion phenomena B31 Mechanical Design Technical Committee Considering how to provide design guidelines based on recent work in DOE complex

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