Achievements and Status of Research Activities in the Source Term area European Review Meeting on Se

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Achievements and Status of Research Activities in
the Source Term area European Review Meeting
on Severe Accident Research(ERMSAR-2007)Forschun
gszentrum Karlsruhe, Germany, 12-14 June 2007
T. Haste1, P. Giordano2, L. Herranz3
1PSI Villigen, Switzerland, 2IRSN Cadarache,
France, 3CIEMAT Madrid, Spain
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SOURCE TERM AIMS
OBJECTIVES

• WP14.1 OXIDEN effect of air ingress - under such
  conditions, the fuel and its fission products
  (FPs) may oxidise. Some (especially the very
  radio-toxic ruthenium) may form highly volatile
  oxide species which may be released to the
  environment
• WP14.2 HITEMP iodine volatility in the Reactor
  Coolant System (RCS) - the impact of high
  temperature on FP behaviour is investigated to
  improve the predictability of iodine species
  exiting the RCS the effect of silver-indium-cadmi
  um release on the speciation is also considered
• WP15 AEROB aerosol behaviour quantification of
  the source term following steam generator tube
  rupture, which leads to containment by-pass
  aerosol leakages through containment concrete
  wall cracks, revaporisation phenomena are also
  studied interaction of deposited aerosols with
  the RCS substrate may be considered later
  deposition/resuspension included specifically in
  JPA3
• WP16 CONTCHEM iodine behaviour in-containment -
  to improve the predictability of the various
  chemical and physical processes which control the
  iodine behaviour in both the gas and water
  phases FP heating/PARs, Ru behaviour in
  containment added in JPA3.

These aims are addressed in Technical Circles, 14
in all, composed of experts working in the areas
concerned
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WORK PROGRAMME

• 1- FP release under highly oxidizing conditions
  (WP14-1)

Experimental means
RUSET (AEKI), Ru speciation (VTT)MERARG (CEA),
analytical tests (UCL)FIPRED (INR), AECL
facilities (AECL)future VERDON (CEA)
Modelling work
Experim. review
Jointly-executed research IRSN AEKI CEA
EDF ENEA - FZK GRSINR VTT AECL
Interpretation
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WORK PROGRAMME

• 2- Transport High temperature gas phase
  chemistry in RCS (WP14-2)

Modelling work
Experim. review
Jointly-executed research IRSN AEKI - EDF
FZK GRS JRC/IE PSI UJV VTT - AECL
Interpretation
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WORK PROGRAMME

• 3- Aerosol behaviour impact on Source Term (WP15)
  

Experimental means
PHEBUS FP (IRSN), REVAP (JRC/ITU), RADSOL (UCL),
PECA/SGTR (CIEMAT)

ARTIST/FP5 (PSI), STORM (JRC Ispra),
PSAERO/HORIZON (FORTUM/VTT), HCE (AECL), IRSN
crack tests, possible COLIMA (CEA)
Modelling work
Experim. review
Jointly-executed research IRSN CEA CESI
CIEMAT Demokritos EDF Fortum GRS - JRC/ITU
JRC/IE PSI UJV VTT AECL - UNEW
Interpretation
Model proposals

Aerosol retention in cracks Aerosol retention in
SG Deposit remobilization
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WORK PROGRAMME

• 4- Containment chemistry (WP16)

Experimental means
Chalmers tests (Univ.), CAIMAN (CEA), PARIS
(AREVA), SISYPHE (IRSN)

PHEBUS FP (IRSN), EPICUR (IRSN)ThAI-Iod9
(GRS/Becker)RECI (IRSN)
Model proposals
Adsorption/desorption Liquid-gas mass
transfer Radiolytic oxidation of iodine Ruthenium
chemistry
Iodine data book
WMT, PSI, AECL
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RUTHENIUM BEHAVIOUR
RESULTS

• Reactor calculations have indicated that UO2 may
  be exposed to air thus enhancing Ru release
  potential and have specified prevailing
  conditions
• Ruthenium release occurs in oxide form after an
  incubation period during which full oxidation of
  fuel and cladding occurs (RUSET and AECL tests),
  further data from a MERARG test is pending
• Models have been developed for fuel oxidation and
  Ru release applicable to oxidising conditions
• Further data are required on Ru release in air to
  validate these models independently (future
  VERDON programme, ISTC/VERONIKA?)
• Oxide forms can stay volatile enough at lower
  temperatures to be transported to the reactor
  containment (RUSET and VTT tests)
• The potential Ru release into the containment and
  its demonstrated persistence there in volatile
  RuO4 form have stimulated investigations under
  containment conditions - experimental and
  modelling studies at IRSN and Chalmers University
  are addressing these issues

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IODINE BEHAVIOUR - CIRCUIT
RESULTS

• Knowledge of iodine transport through the RCS is
  essential to define the source term to the
  containment or to environment (bypass
  sequences)
• Analysis of Phebus FP and VERCORS-HT data, with
  equilibrium ASTEC/SOPHAEROS calculations have
  demonstrated the influence of Mo and structural
  materials on I vapour chemistry
• Consensus reached on the close connection amongst
  Cs, Mo, I and Cd and on the next steps to
  improve understanding
• The CHIP facility is now producing the first-ever
  data on chemical kinetics effects, that will
  enable advanced models accounting for
  non-equilibrium effects to be developed
• Other chemical elements released from degrading
  AIC control rods (Ag, In and Cd) would affect the
  physico-chemical environment of iodine transport
• The AIC release models developed from
  separate-effects data (EMAIC) will be tested in
  near-prototypical conditions in the upcoming
  QUENCH-13 integral test, aiming to assess better
  existing uncertainties (e.g. for Cd burst
  release)
• Active collaboration on Q-13 experimental and
  modelling support under way

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IODINE BEHAVIOUR - CONTAINMENT
RESULTS

• Current knowledge on iodine chemical behaviour in
  the containment is concisely encapsulated in the
  recent Iodine Data Book
• Nonetheless, further experimental data are
  required on iodine oxidation in gas and aqueous
  phases, liquid-mass iodine transfer, RI
  formation/destruction, etc. The EPICUR, CAIMAN,
  PARIS and SISYPHE tests are producing/have
  produced the data required to understand better
  and then to model all those aspects. These are
  further supported by new availability of AECL
  data
• Current code capabilities in an integral
  containment geometry are being assessed through
  the ThAI-Iod9 benchmark and the Phebus FPT2
  experiment interpretation, the latter resulting
  in a consensus on gaseous iodine evolution and
  inorganic/organic iodine distribution in the gas
  phase
• Potential conversion of particulate iodine into
  gaseous iodine species due to iodine interaction
  with in-containment safety systems (i.e., PARs)
  was shown by RECI small-scale tests, and
  theoretical assessments have shown that this
  could be quantitative. However, these results
  need to be confirmed at a larger scale to fully
  assess actual consequences

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AEROSOL BEHAVIOUR - SGTR
RESULTS

• Aerosol leakages to the environment either
  through containment cracks or directly from the
  primary circuit (bypass sequences), can
  contribute to the source term
• In the case of SGTR sequences some aerosol
  retention could occur in the secondary side, as
  experimentally demonstrated in the SGTR project
  of the 5th EU FWP of EURATOM
• Even if the secondary side of the steam generator
  is dry, data seem to indicate that some
  decontamination should be foreseen (this being
  much larger if water is present)
• Interpretation of available data, as well as
  development of models for dry and wet conditions
  has enhanced understanding and predictability,
  although there is some way to go
• Resuspension is a key phenomenon in the SGTR
  scenario and it is presently being revisited
  based on STORM, PSAERO data that from thick
  deposits in particular needs better understanding

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AEROSOL BEHAVIOUR CONTAINMENT CRACKS
RESULTS

• Loss of containment integrity by cracking of the
  concrete could also affect the source term if
  radioactive particles can leak through
• Aerosol transport models have been developed and
  compared satisfactorily to available data (SIMIBE
  tests) - they seem to indicate a high
  decontamination factor in the cracks,
  particularly in the presence of steam
• nonetheless, prototypical experiments are missing
  and scoping tests in the COLIMA facility under
  the EU PLINIUS transnational access programme
  have been proposed

REVAPORISATION

• Revaporisation of previously deposited
  radionuclides (as evidenced by PHEBUS) could lead
  to a late source term. Data from the REVAP
  facility together with those from AECL are being
  analyzed to improve modelling capability in
  integral situations.

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FORWARD PROGRAMME
HIGHLIGHTS OF FORWARD PROGRAMME

• WP14-1 joint interpretation of new Ru data from
  AECL tests (in joint selection), RUSET (AEKI)
  continued experiments on Ru release from alloys,
  VTT Ru tests
• WP14-2 CHIP data on iodine speciation in the
  circuit becoming available for both analytical
  and phenomenological lines, good cooperation on
  design and construction, possibilities for joint
  analysis QUENCH-13, strong cooperation on test
  conduct (especially SIC aerosol measurements) and
  pre-test calculational support new VTT facility
  on revaporisation and speciation (link with WP15)
• WP15 new revaporisation data from AECL, new
  effort on resuspension/deposition modelling
  including turbulent deposition (use of
  newly-acquired STORM data is being encouraged)
  possible COLIMA experiment (s) under PLINIUS
• WP16 availability of AECL RTF data with
  possibility of joint interpretation, EPICUR tests
  and interpretation, ThAI-Iod9 benchmark,
  continuing experiments on PARs/FP heating by IRSN
  (RECI successor) and on Ru behaviour
  in-containment at IRSN and Chalmers.

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COOPERATION
COOPERATION AND DISSEMINATION

• In SARNET, with the Corium, ASTEC, Research
  Priorities, Database and Spreading of Excellence
  areas (here through staff mobilities and
  contribution to the severe accident book and to
  training courses
• Outside SARNET, with PHEBUS FP and ISTP
  (especially chemistry areas, joint technical
  meetings) ISTC, though review of proposals (EVAN
  now a project, VERONIKA) watching brief kept
  on CSNI GAMA-related matters such as ThAI
  continuation and BIP FZK QUENCH through support
  to QUENCH-13

DISSEMINATION

• In SARNET, via ACT, where meetings are organised
  and documents stored (almost 60 technical papers
  so far)
• Outside SARNET, in journals (4 papers so far) and
  conference papers (19 so far, plus contributions
  to overall SARNET reports)

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CONCLUDING REMARKS
CONCLUSIONS

• The Source Term area has continued to make good
  overall progress in increasing understanding in
  its technical areas through a combination of
  experimental work, interpretation of data and
  modelling directed towards ASTEC
• Good cooperation has been established internally
  within other SARNET work areas such as Corium,
  IED, Spreading of Excellence and Research
  Priorities, and externally with Phebus FP, ISTP,
  ISTC and QUENCH, etc.
• The work of the SARNET area has been reported
  fully in the open literature and in journals
  more publications are expected as the project
  matures
• A process of reflection is starting on possible
  follow-on projects in the 7th FW (2007-2013),
  taking account of the recommendations of the
  Research Priorities Group

The authors thank the many technical contributors
within SARNET organisations, too numerous to
name, and the European Commission for funding
SARNET, in the 6th Framework Programme area
Nuclear Fission Safety of Existing Nuclear
Installations, under contract number
FI6O-CT-2004-509065.