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Advanced boiling twophase flow modeling: A major challenge for nuclear industry

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NUCLEAR SAFETY : 2 basic principles. Successive barriers (fuel cladding is the first one) ... Overall optimization for the complete nuclear fuel cycle ... – PowerPoint PPT presentation

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Title: Advanced boiling twophase flow modeling: A major challenge for nuclear industry


1
Advanced boiling two-phase flow modeling A
major challenge for nuclear industry
  • A. Guelfi, O. Marchand (EDF RD)R. Assedo, L.
    Catalani (AREVA-NP)

2
Overview
  • Two major stakes safety and competitiveness
  • Design and safety studies
  • RD challenges for boiling flow modeling
  • A major challenge DNB prediction

3
1. Safety and Competitiveness
4
Safety of NPPs
  • THE HIGHEST PRIORITY
  • FOR EVERY POWER PLANT, AT ANY TIME
  • Safety criteria are fulfilled
  • Safe operation of the plant is guaranteed by
    design and monitoring procedures
  • NUCLEAR SAFETY 2 basic principles
  • Successive barriers (fuel cladding is the first
    one)
  • Defence in depth

5
Competitiveness of NPPs
  • Thermal Efficiency of main components (core,
    exchangers)
  • Optimized power density and distribution
  • Optimized heat transfer mechanisms (primary,
    secondary, cooling)
  • Mechanical resistance of main components
  • Irradiation, corrosion, vibrations, thermal
    fatigue, etc.
  • Two major challenges
  • PLANT AVAILABILITY (Kd)
  • plant LIFETIME EXTENSION (40 years and beyond)
  • Maintenance costs savings

6
Competitiveness of NPPs
  • A key issue fuel design and management
  • Overall optimization for the complete nuclear
    fuel cycle
  • Reduction of fuel design/construction/supply
    costs
  • A more and more flexible fuel management
    different fuel assembly types, different vendors
    within one reactor core
  • High efficiency fuel assemblies
  • High local power density plant power uprates
  • High burn-up cycle extension, reduction of fuel
    reload costs

7
2. Design and Safety studies
8
Design and Safety studies
  • Numerous new studies are required
  • Existing NPPs
  • Fuel management evolution (reloads)
  • Lifetime extension
  • Evolution of the tools and methodologies
  • New NPPs design and construction of new
    reactors
  • Worldwide Nuclear Renaissance (2008 30 reactors
    under construction 90 new projects ! 40
    non-nuclear countries have declared their
    interest to AEIA)
  • Among them
  • EPR Finland first-off reactor, France, US,
    China, South Africa, etc
  • BWRs

9
Design and Safety studies
  • Advanced simulation tools and methodologies
  • Handling normal operation and accidental
    conditions
  • Covering multi-disciplinary coupled physics,
    including 3D thermal-hydraulics
  • In-depth physical and numerical validation a
    prerequisite for Industrial qualification with
    uncertainty analysis
  • Improved physics more accurate and predictive
    models
  • Enhanced safety
  • Reduction of excessive conservatisms

10
Design and Safety studies
  • Modeling margins

11
3. RD challenges for two-phase flow modeling
12
Two-phase flow modeling challenges (see Guelfi et
al., Nuclear Science and Engineering, 2007)
  • Nuclear Thermal-Hydraulics
  • Industrial simulation tools
  • From macroscopic to local modeling scales
  • Different levels of maturity/qualification

13
Two-phase flow modeling challenges
  • Component and system scales
  • Improved models and closure terms, validation
    against new experiments
  • Extension of the qualification scope (e.g.
    CATHARE 3)
  • The advent of CMFD
  • Improved knowledge of local flow phenomena is a
    key issue for numerous design and safety issues
  • Fuel design (spacer grids) local wall-to-fluid
    heat transfer, flow mixing, etc.
  • Crud Deposition local flow interaction with
    chemical processes
  • SG Tube vibrations Fluid-Structure Interaction
    in high void fraction 2-phase flow
  • Etc.
  • Fuel management evolution (reloads)
  • Lifetime extension
  • Evolution of the tools and methodologies
  • New NPPs (Gen III, III) design and construction
    of new reactors
  • EPR Finland first-off reactor, France, US,
    China, South Africa, etc
  • BWRs

14
Two-phase flow modeling challenges
  • The need for validated CMFD tools
  • Wall-to-fluid and interfacial transfers must be
    correctly predicted
  • In industrial complex geometries
  • Under real thermal-hydraulic conditions
    (primary/secondary circuits)
  • High pressure and temperature
  • High turbulence level
  • From bubbly to churn turbulent flow
    ( all-flow-regime  tools)

15
Two-phase flow modeling challenges
  • The NEPTUNE initiative a first step !
  • Joint development of NEPTUNE_CFD code
  • Physical modeling and experiments
  • NURESIM-NURESP European Projects international
    collaboration
  • Collaborative research on CFD-scale two-phase
    flow modeling in connection with the industrial
    needs (including DNB and dry-out)
  • CMFD are still based on averaged models
  • Understanding of local flow phenomena is required
  • Closure terms must be developed/validated
  • Significant progress is now expected from very
    fine experimental investigation and Direct
    Numerical Simulation

16
4. A major challenge DNB prediction
17
A major challenge DNB prediction
  • DNB-type CHF prediction still a challenge !
  • Competition of numerous microscopic and
    mesoscopic scale phenomena
  • Basic physics not fully understood after decades
    of RD...
  • Current methodologies are very expensive
  • Numerous representative CHF experimental data
    banks are required
  • CHF predictors are based on empirical
    correlations
  • CHF studies rely on subchannel-type 3D TH codes
  • Statistical methodologies are needed to account
    for different sources of uncertainties

18
A major challenge DNB prediction
  • DNB CFD-based Local Predictive Approach (LPA)
  • LPA concept (introduced by EDF, late 90s)
  • Development of more general CHF predictors based
    on the local flow parameters
  • A 3-step strategy
  • Get a reliable and accurate two-phase flow CFD
    tool, with respect to PWR core geometrical and TH
    configurations. Improved physical models are
    still needed !
  • Select adequate CHF data banks and CFD-simulate
    the associated experiments to create numerical
    data bases
  • Develop a CHF local correlation on a reference
    data bank and further assess its validity against
    other data banks
  • STEP 1 is one of the current major challenges of
    the nuclear TH community

19
5. Conclusion
20
  • Computing Power is (almost) ready
  • Movie
  • EDF Code_Saturne calculation
  • real geometry real PWR TH conditions
  • 100 M nodes, 8000 processors
  • We need more predictive C(M)FD models !
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