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

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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


1
Integration of Hydrogen Safety Into Design and
Safety Analyses at the High Flux Isotope Reactor
  • David H. Cook
  • UT-Battelle/Oak Ridge National Laboratory
  • 2010 EFCOG SAFETY ANALYSIS WORKSHOP
  • APRIL 2010

2
OUTLINE OF PRESENTATION
  • 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

3
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

4
The HFIR cold source installed into existing HFIR
beam position HB-4
5
Cold Source Hydrogen Footprint Affects Large Part
of HFIR Facility
6
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

7
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

8
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
    protection
  • Multiple containment boundaries to ensure no
    single failure brings hydrogen and air or water
    together
  • Highest quality standards used for hydrogen
    containment materials
  • High purity gases used--combined with testing and
    procedures

9
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
    building
  • In-reactor portion of CNS designed with two ASME
    code barriers to prevent reactor overpressure
    event affecting CNS

10
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

11
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

12
CNS Hydrogen Safety-Design Integration Timeline -
continued
  • 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
    integration
  • Refined safety, design, and operational goals
  • More detailed design information
  • Preliminary component and system testing
    performed
  • Hydrogen hazard and transient analysis to suggest
    moving active equipment outside changing
    operational point to minimize two phase flow
    issues
  • Preliminary equipment classification

13
CNS Hydrogen Safety-Design Integration Timeline -
continued
  • 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
    pressurizer
  • 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

14
CNS Hydrogen Safety-Design Integration Timeline -
continued
  • 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

15
Evolution of CNS Safety-Design Documentation
  • Cold Source safety documentation evolved along
    with the design and continues to evolve with
    operation
  • Pre-Conceptual Design Report and Conceptual
    Design Report contained preliminary DSA
    information
  • Hazard analysis report at beginning of final
    design
  • 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

16
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

17
Cold Source DSA Development
  • Final DSA was developed in two major steps
  • Phase 1 Final development and major system
    testing
  • Phase 2 Final commissioning and normal reactor
    operation
  • 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

18
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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