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Integration of Hydrogen Safety Into Design and Safety Analyses at the High Flux Isotope Reactor


Integration of Hydrogen Safety Into Design and Safety Analyses at the High Flux Isotope Reactor David H. Cook UT-Battelle/Oak Ridge National Laboratory – PowerPoint PPT presentation

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Title: Integration of Hydrogen Safety Into Design and Safety Analyses at the High Flux Isotope Reactor

Integration of Hydrogen Safety Into Design and
Safety Analyses at the High Flux Isotope Reactor
  • David H. Cook
  • UT-Battelle/Oak Ridge National Laboratory
  • APRIL 2010

  • HFIR Cold Neutron Source (CNS) Description
  • CNS hydrogen safety-design integration overview
  • Hydrogen safety design strategy
  • Integration timeline
  • Evolution of CNS safety and design documentation
  • Conclusions and lessons learned through the HFIR
    CNS hydrogen safety-design integration process

The HFIR CNS Description
  • Hydrogen cools neutrons enhancing the production
    of 4-12 ? neutrons
  • Highest heat load of any cold source placed into
    a reactor
  • 2.77KW
  • Employs supercritical hydrogen
  • 15 bar absolute (218 psia)
  • 18-20 K ( -425F)
  • 1 liter per second
  • Hydrogen system inventory
  • Cryogenic portion 6.1 kg
  • Entire system 9.65 kg
  • Significant new explosion and cryogenic gas
    hazards involved

The HFIR cold source installed into existing HFIR
beam position HB-4
Cold Source Hydrogen Footprint Affects Large Part
of HFIR Facility
CNS Involved New Hydrogen Hazards Requiring
Detailed Design-Safety Integration
  • Proximity of hydrogen to reactor safety equipment
  • Possible effects on all reactor safety functions
  • Reactor shutdown
  • Primary coolant pressure boundary
  • Decay heat removal
  • Confinement atmosphere and building integrity

Hydrogen Safety-Design Strategy
  • Integrated design and safety analysis effort used
    combination of facility modifications, new
    equipment location, multiple containment
    boundaries, and active systems to address nuclear
    and hydrogen safety requirements
  • Reactor facility modifications to prepare for
    cold source
  • Passive, multiple-boundary lines for hydrogen in
    reactor building
  • Active cooling and control equipment in hydrogen
    equipment area (HEA) just outside building
  • Pressurization equipment and relief points remote
    from HEA and reactor building
  • CNS reactor scram provided as defense in depth

Hydrogen Safety Requirements and Goals
  • Design should result in low probability 1E-6 /yr
    of damage to reactor or safety systems
  • NASA hydrogen safety guidelines and applicable
    hydrogen safety standards/guides used for worker
  • Multiple containment boundaries to ensure no
    single failure brings hydrogen and air or water
  • Highest quality standards used for hydrogen
    containment materials
  • High purity gases used--combined with testing and

Hydrogen Safety Requirements and Goals -continued
  • Engineered vent and relief systems to prevent
    explosive gas mixtures
  • Primary hydrogen barriers are ASME code stamped
    vessels, piping and transfer lines built to B31.3
    piping code or international equivalent
  • Seismic qualification of hydrogen boundaries
    inside reactor building and key portions of
    hydrogen boundaries and relief systems outside
  • In-reactor portion of CNS designed with two ASME
    code barriers to prevent reactor overpressure
    event affecting CNS

Hydrogen Safety Requirements and Goals -continued
  • In-reactor portion of CNS analyzed and shown to
    contain hydrogen oxygen detonation
  • In-reactor portion of CNS analyzed in conjunction
    with vent system to show worst cryogenic line
    break is contained and moderator vessel melting
    is contained
  • Helium refrigerator system designed for detection
    of hydrogen leak across main heat exchanger
  • Operational interfaces between reactor and cold
    source minimized

CNS Hydrogen Safety-Design Integration Timeline
  • Spring 1995-Early group formed to study adding
    CNS to HFIR after ANS reactor project cancelled
  • Preconceptual design study issued Dec.
    1995--included preliminary nuclear and hydrogen
    safety-design integration
  • Project design objectives and safety philosophy
    set considering reactor nuclear safety basis and
    hydrogen safety information from industry,
    regulations, and other CNSs
  • Safety and operational requirements for project
    reflected reactor safety requirements, hydrogen
    safety requirements, operational requirements,
    and project goals

CNS Hydrogen Safety-Design Integration Timeline -
  • Jan., 1996 Basic Energy Sciences review
    recommended installation of HFIR CNS
  • Conceptual design study issued May 1998--included
    more complete nuclear and hydrogen safety-design
  • Refined safety, design, and operational goals
  • More detailed design information
  • Preliminary component and system testing
  • Hydrogen hazard and transient analysis to suggest
    moving active equipment outside changing
    operational point to minimize two phase flow
  • Preliminary equipment classification

CNS Hydrogen Safety-Design Integration Timeline -
  • Preliminary design phase involved safety-design
    interactions to mature safety analysis and
    design, develop test plans, and develop
    operations plans
  • Major CNS components designed, e.g., variable
    speed circulator and supercritical hydrogen
  • CNS hazard analysis and safety analysis matured
  • Component and system testing continued
  • Project upgraded in Winter, 2004 to formal
    project management starting with Lehman review by
    DOE SC
  • Project baseline established April, 2004

CNS Hydrogen Safety-Design Integration Timeline -
  • Final design phase involved entire division
    focused on design-safety integration
  • Equipment final design, installation, and
    component testing
  • Distributed IC control and safety system design
    completed and tested
  • Two long reactor shutdowns for facility
    modifications and equipment installation
  • Final integrated system testing involving CNS
    without reactorthen CNS plus reactor
  • Final commissioning tests and transition to
    operations in spring 2007
  • Facility design and safety currently under
    configuration control

Evolution of CNS Safety-Design Documentation
  • Cold Source safety documentation evolved along
    with the design and continues to evolve with
  • Pre-Conceptual Design Report and Conceptual
    Design Report contained preliminary DSA
  • Hazard analysis report at beginning of final
  • DSA preparation during final design to support
    final DOE review and approval
  • Resolve USQ aspects of CNS addition to HFIR
  • Document how identify, characterize,
    prevent-mitigate hazards
  • Interface with reactor safety analysis, TSRs, and
    existing SMPs

Cold Source DSA Format and Content
  • DOE Std. 3009 safety analysis approach chosen for
    Cold Source DSA
  • Comprehensive
  • Precedents at HFIR for resolving other HFIR USQs
  • Cold source introduces hazards that are not
    adequately addressed by Reg. Guide 1.70 approach
    used for reactor
  • Plan for Cold Source DSA to coexist-with and
    complement reactor USAR and interface at TSRs,
    emergency procedures, and SMPs
  • Clear interfaces
  • Uses reactor-quality infrastructure that is
    currently in-use

Cold Source DSA Development
  • Final DSA was developed in two major steps
  • Phase 1 Final development and major system
  • Phase 2 Final commissioning and normal reactor
  • Phase 1 included stepwise increase in risk,
    understanding, and cold source design improvement
  • Helium-heater testing
  • Hydrogen-heater testing
  • Helium-reactor testing and operations (planned
    but not used)
  • Phase 2 involved final system hydrogen testing
    with reactor followed by long-term operation

Conclusions and Lessons Learned
  • Use best available knowledge from hydrogen safety
    and reactor safety areas
  • Assemble safety-design integration team early in
    project and maintain consistency through project
  • Augment safety-design team with expert advice,
    support, and review
  • Provide adequate resources and schedule to
    accomplish mission
  • Provide sufficient opportunities for testing to
    support design and safety activities
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