palama - vttsafir2014.vtt.fi/finalseminar/day_1/tr3_4_3_palama_safir2014.pdfpalama project focused...
TRANSCRIPT
VTT TECHNICAL RESEARCH CENTRE OF FINLAND LTD
PALAMA
SAFIR2014 Final seminar
19th – 20th March 2015
Ville Tulkki
2 2 17/04/2015
Polttoaineen laaja-alainen mallinnus
PALAMA
Project focused on analysis on
nuclear fuel behaviour
4 years, 12.1 person-years, 14
researchers, 1.45 M€
Deliverables include 36
technical reports, 15
conference papers, 7 journal
papers, 2 Master’s theses and
1 Licentiate thesis
Asko Arkoma, Santtu
Huotilainen, Silja Häkkinen,
Anitta Hämäläinen, Timo
Ikonen, Seppo Kelppe,
Joonas Kättö, Henri
Loukusa, Anna Nieminen,
Jan-Olof Stengård, Elina
Syrjälahti, Ville Tulkki, Ville
Valtavirta, Tuomas Viitanen
3 17/04/2015 3
PALAMA Highlights
Completion of methodology for statistical assesment of the number of
failed rods during large break LOCA
Methodology development initiated in SAFIR2010 POKEVA
Development of FINIX fuel module
Improves fuel description in wide variety of host codes
New methodology to describe cladding response to stresses
To replace widely used strain hardening rule
Statistical evaluation of
failed rods during large
break LOCA
5 17/04/2015 5
Statistical methodology
Holistic approach that provides a fraction of failed rods
95% confidence that in 95% of LB LOCAs the actual number will be the
same or less
59 global APROS LB LOCA simulations, 1000 local fuel performance
simulations per global case
Also power histories from reactor physics codes required
First application: EPR analysis performed for STUK
STUK agreed to allow the publication of the results
A. Arkoma et al., Nuclear Engineering and Design Volume 285, 15 April
2015, Pages 1–14
6 17/04/2015 6
Calculation system
7 17/04/2015 7
Result
At 95/95 confidence and probability, at most 1.2% of all the rods in the
reactor fail
10% maximum allowed for this kind of scenario
FINIX fuel module
9 17/04/2015 9
FINIX – fuel behavior model and interface for
multiphysix applications
Reactor
physics
Thermal
hydraulics coolant conditions
clad temperature
Fuel
behavior
10 17/04/2015 10
FINIX – fuel behavior model and interface for
multiphysix applications
Reactor
physics
Thermal
hydraulics coolant conditions
clad temperature
FINIX
11 17/04/2015 11
FINIX models
Coupled thermomechanical
models
Solves the time-dependent radial
heat equation, in several
independent axial nodes
Rigid pellet (no elastic
deformations)
Cladding modeled as a thin-
walled tube
Thermal and mechanical solutions
coupled through gap conductance
and gap pressure
Burnup effects can be taken into
account in the initial state if given
by, e.g., FRAPCON
12 17/04/2015 12
FINIX coupling
Currently coupled to
Serpent 2
TRAB-1D/3D and Hextran
Provides realistic description of
fuel behaviour
Fast transient with Serpent 2
TMI-1 power peak with TRAB-1D
13 17/04/2015 13
FINIX
More information on FINIX in PALAMA special
article in the SAFIR2014 proceedings
Also: ”Module for thermomechanical modeling
of LWR fuel in multiphysics simulations”, T.
Ikonen et al. Annals of Nuclear Energy (2014),
accepted manuscript, in press.
FINIX currently licensed to Aalto, KIT
(Germany), Necsa (S. Africa) and CV Rez
(Czech Republic)
FINIX development continues in SAFIR2018
PANCHO project
Cladding viscoelastic
response
15 17/04/2015 15
Cladding creep response to changing
conditions
Cladding protects the fuel pellets
from the environment and contains
radioactive nuclides
Creep deformation at high
temperature and pressure
Commonly assumed that changes in
conditions can be accounted by
strain hardening rule
Accumulated strain invariant during
changes
Experiments show this is not true
16 17/04/2015 16
Viscoelastic model
Metal anelastic behaviour
Slow reversible deformation
Usually assumed insignificant
Irradiation and fuel behaviour
make it relevant in cladding
Can be illustrated with mechanical
analogs
Springs and dashpots parallel
and in series
Anelastic + permanent strain =
viscoelasticity
17 17/04/2015 17
Cladding creep
response
Viscoelastic model enables
reproduction of cladding response
to transient stresses
V. Tulkki, T. Ikonen Journal of Nuclear Materials,
457 (2015) , pp. 324-329
V. Tulkki, T. Ikonen, Journal of Nuclear Materials,
445 (2014) pp. 98-103.
18 17/04/2015 18
Stress relaxation behaviour
Viscoelastic model also
capable of simulating stress
relaxation behaviour
Figure displays model
performance in stress
relaxation with coefficients
fitted to creep experiment
Doctoral thesis ”Modelling fuel
behaviour and cladding
viscoelastic response” due this
summer V. Tulkki, T. Ikonen, “Modelling anelastic contribution to
nuclear fuel cladding creep and stress relaxation”,
submitted to Journal of Nuclear Materials (2015)
19 17/04/2015 19
Summary
PALAMA was 4 year project focused on fuel
performance issues
Wide variety of case studies, model
development, code development and analysis
Several highlights presented here
Completion of methodology for statistical
assesment of the number of failed rods during
large break LOCA
Development of FINIX fuel module
New methodology to describe cladding response
to stresses
More can be found from the SAFIR2014 Final
seminar proceedings
TECHNOLOGY FOR BUSINESS