LTH Severe accident research

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LTH Severe accident research

• Leading position in Aerosol Research
  (Experiments, TH modeling, fundamentals)
• Competence centre for Severe Accident analyses
  (MELCOR, SCDAP/RELAP, training)
• Industrial technology developments (e.g.
  Iodine retention)
• Contribution to teaching (PhDs, students
  projects, lectures)

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Severe Accident Phenomenology
? Lack of core cooling ?over heating of fuel ?
melting ? Release of fission products
and aerosol particles hydrogen ?In
Vessel, Primary Circuit and Containment
phenomenology - thermal hydraulics (water
and steam, molten debris) - aerosol physics
coupled with thermal-hydraulics - fission
product irradiation chemistry In total 983
Phenomena affecting reactor safety(1) 21
issues, grouped in 5, deserving further research
1) EU 5th Thematic Network Project EURSAFE
(2003)
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Needs of Industry and Safety Authorities
Scientific Interests

• Improved understanding of Phenomena
• Modelling
• Code Assessment
• Application
• Important synergy
• ?Finding hot issues deserving research
• Resolving issues by
• Experiments
• Analytical methods
• Technology development

• Improved and reliable prediction of plant
  behaviour
• Containment vulnerabilities
• H2 loads
• FP loads
• Reduce uncertainty in source term and off
  site consequences
• Containment by-pass
• Containment venting/failure
• Assess Accident Management Measures
• Operator training
• Periodical Safety Review

4
ENVIRONMENT
?National and International Co-operations
?bilateral and within Network ?
International Consensus for Importance and
Significance ? Universities ETH
Zürich,ETH Lausanne, University of Bern
University of Newcastle (UK), University of Udine
(I) Universities within the ARTIST
Project Framework
Universidad Politécnica de Madrid

University of Brussels
Royal Institute of Technology
.... ?
Partners CH UAK, ENSI, NPP, Industry
Foreign US, Japan, and EU
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Severe Accident Research Activities at LTH

• Experimental
• Own work
• Aerosol
• Iodine chemistry
• International
• Phebus-FP
• EU FWP
• etc.

• Analytical
• Model development
• Code assessment

• Plant application
• Analyses of certain accident scenarios
• Competence Centre Application of
  acquired knowledge and tools

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Multi-purpose Aerosol Generation Facility DRAGON

• Multi-component, multi-layer aerosol particles
  generated by
• Evaporation and condensation of single/multiple
  material powder/solution and powder
  fluidisation
• Internationally accepted simulant material
• Severe accident prototypical conditions
• aerosol particle size and concentration
• steam and non-condensable gas (N2/air) mixture
• at pressures of max 5 bar and temperature of
  lt300 - 350 oC

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Phenomenological Research Past and current

• Aerosol behaviour
• pool scrubbing of iodine and aerosols
  (1989-1996)
• aerosol deposition under condensing steam
• (1994-1998) (SBWR/ESBWR, SWR1000)
• aerosol deposition in complex geometries
• (EU 5th SGTR) (2000-2002)
• aerosol and droplet retention in secondary side
  of a PWR
• steam generator with broken tube/s (Phase I
  2003-2007)
  (Phase II 2009-2012)

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POSEIDON I Molecular iodine scrubbing in water
pools(1989-1992)

• Main outcome
• bubble hydrodynamics dependent iodine
  scrubbing
• bubble distribution, residence time,
  submergence
• moderate to very high decontamination factors
  at submergence exceeding 1 m in water of pH
  of 7

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POSEIDON II Aerosol scrubbing in hot water pools
(1993-1996)

• Unique outcome
• Particle size dependent decontamination factor
• Significant decontamination instead of no
  decontamination as assumed
• Reduced uncertainty in decontamination factor
  (improved models, BUSCA)

10
AIDA Aerosol thermal-hydraulic interaction and
effect on SBWR/ESBWR condenser performance
(1993-1997)
(LTH-ALPHA, EU4th FWP TEPSS)

• Main outcome
• formation of mud as a result of steam
  condensation
• plugging at the entrance
• flow redistribution
• reduced heat transfer

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EU4th FWP CONGA/CESANE Aerosol thermal-hydraulic
interaction and effect on SWR1000 condenser
performance
(1997-1999)

• Main outcome
• a thick deposit layer on the finned tubes
  avoiding efficient condensation
• tube layer underneath overloaded
• hence reduced efficiency of the passive
  containment cooling system
• Framatome ANP (Siemens) adopted a new design
  based on the outcome

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Applied Research and Development

• Qualification of CCI (Sulzer) Containment Venting
  Filter
• Participation from the first day in the
  development programme (1989-1992)
• Qualification and further improvements
• qualification of the system using aerosol
  particles very high (50000 to 250000)
  decontamination factor (1993-1995)
• qualification and optimisation of operational
  characteristics high decontamination factors
  for molecular iodine (gt 100) and organic
  iodide (gt 10) (2000-2003)
• both under prototypical severe accident boundary
  conditions

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Qualification of CCI (Sulzer) Containment Venting
Filter
Filter module
14
Qualification of CCI (Sulzer) Containment Venting
Filter System to measure inactive molecular
iodine and organic iodides
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Basic Research By PhDs

• Description of bubble hydrodynamics in large
  pools (1997-2001)
• Deagglomeration of aerosol agglomerates
  (2004-2008)
• Physics of Aerosol Particle Interaction with a
  Turbulent Flow inside a Differentially Heated
  Cavity through DNS
• Large Eddy Simulation of Particle Removal inside
  a Differentially Heated Cavity
• Deagglomeration by impact Application to nuclear
  aerosols
• High-resolution flow structure measurements in
  fuel rod / tube bundles

16
Phenomenological Research Past and current
Iodine chemistry ? development of IMPAIR3 Code
(gt1991-2004) ? radiolytic stability of AgI
(1997-2003) ? development of PSIODINE code
(gt2001-2006) ? basic and enhanced
decomposition of organic iodide (2000-
2003) ? mitigation of volatilization of iodine
in aqueous phase (2003-2007) ? effect of
nitrate and nitrite on iodine speciation and
volatility (2003-2009)
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Phebus FP Participation (1997- current)

• Objectives
• Code assessment (SCDAP/RELAP5, MELCOR, VICTORIA,
  SASPROG)
• Perform supportive pre-/post-test calculations
  (FPT0/FPT1/FPT2/FPT3)
• Perform supporting experimental investigations
  (FPT4/Filter Tests, Radiolytic stability of
  AgI, Radiolytic oxidation of N2 in air)
• Data interpretation for plant applications

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FPT4-Filter Test facility (1997-1999)
FPT4 back-up filter, before and after a test
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ARTIST - Facility

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ARTIST project how efficiently the PWR stream
generator secondary side components can mitigate
the activity release into the environment

21

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Tools Code Development/Validation and
Application
MELCOR
(gt 2000)
(1988-2003)
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Tools Code Development/Validation
and Application
IMPAIR3SCDAP/RELAP5VICTORIASASPROGARES
WECHSL (CORCON)VANESA CONTAIN
?
Plant Application
Goesgen (PWR)
Beznau (PWR)
Leibstadt (BWR)
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Strategy in establishing a Competence Centre
Establishing and use of PSI suite of codes
(1988-2003)
Acquiring MELCOR, assessment and further
development (1998 current)

• Establishing a competence centre (2003-2005)
• experimental and standard versions of MELCOR
• on-line simulation tool MELSIM
• qualified plant decks

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A new tool An Improved End-User Needs-Oriented
Mission Beyond Design and Severe Accidents Plant
Analysis and Technical Support Program (PATS)

• Competence Centre Providing Scientific and
  Technological Support to Swiss NPPs
• backed up with strong experience emerging from
  DEMONA/LOFT/LACE/ACE age to the current
  research
• resolution of key issues possessing scientific
  aspects by analytical and experimental
  investigations

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Accompanying Research (2003-current)

• ARTIST Aerosol and droplet retention in
  secondary side of Steam generator
• EU6th/EU7th NoE SARNET - Modelling of high
  temperature iodine chemistry in IMPAIR3 -
  Quenching
• EU7th ASAMPSA2 Preparation of best practice
  guidelines for L2 PSA2
• Modelling of Air oxidation QUENCH,
  ISTC/PARAMETER SF4
• Phebus FPT3/QUENCH
• - Effect of B4C
• Verification/Qualification of MELCOR plant
  input decks - Plant safety evaluation
  studies
• Novel technique to decompose and fix iodine
  species in water
• PhD studies on fundamentals of aerosol physics