Graphite Research and Development A.G. Steer Graphite Core Project Team

Graphite Research and
Development
A.G. Steer
Graphite Core Project Team
Lifetime Management Branch
Graphite Research and Development
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Business Needs
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Strategic Funded Projects
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Direct Funded Work
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Magnox Projects
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BE/Magnox Collaboration
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Summary
Business Needs
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British Energy’s business imperatives
– Operational excellence
– Financial stability
– Life extension
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Leading to
– Safe and reliable operation
– Profitability
– Long-term contribution to the energy needs of the
UK
Business Needs
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Graphite Core Project Team’s contributions
– Maintain margins within the AGR core safety
cases
– Inspect and monitor the cores to provide relevant
information about the effects of graphite
degradation processes in a timely and cost
effective manner
– Improve understanding of core degradation
processes and their consequences
– Acquire material property data in advance of
reactor operations
Business Needs
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Graphite Core Safety Cases are based on five legs:
– Core and Component Condition Assessment
(CCCA)
– Damage tolerance
– Inspection
– Monitoring
– Consequences
Legs are constructed to be as independent of each
other as possible
Business Needs
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New information
– Material properties
– Material property models
– Fracture processes
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Validation
– Whole core experiments
Business Needs
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Technique and Equipment Development
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–
–
–
Core inspection
Monitoring
Material property measurements
Analytical methods for:
o
o
o
Static and seismic core models
Fuel and control rod movements
Stress analysis and structural integrity assessments
Strategic Funded Projects
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YAE 270 with a budget of:
– £420k in FY06/07
– ~£500k in subsequent FYs
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Build long-term relationships with academic centres
specialising in
–
–
–
–
Fundamental crystal behaviour
Materials properties
Fracture
Assessment of monitoring data
Strategic Funded Projects
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Nuclear Graphite Research Group in the Material
Performance Centre, The University of Manchester
–
–
–
–
–
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Prof Andrew Sherry
Prof Barry Marsden
Dr James Marrow
Dr Paul Mummery
Dr Alex Fok
University Post doctoral and Ph.D. Projects
Strategic Funded Projects
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Department of Chemistry, University of Sussex
– Prof Malcolm Heggie
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Department of Engineering, University of Hull
– Dr Gareth Neighbour
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Faculty of Engineering, University of Bristol
– Prof David Smith
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Faculty of Engineering, University of Strathclyde
– Dr Marcus Wheel
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University Post doctoral and Ph.D. Projects
Strategic Funded Projects
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Atomistic Modelling
– First principles study of dislocations in graphite,
GRA/GNSR/6008
– Equivalent irradiation temperature and damage in
graphite, GRA/GNSR/6010
– Development of a theoretical approach to graphite
properties, GRA/GNSR/6021
– Fundamental Approach to Irradiation Creep in
Graphite, GRA/GNSR/6038 – NEW
Strategic Funded Projects
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Atomistic Modelling
– Computer predictions from first principles of all
graphite crystal elasticity terms – No need to invoke
Van der Waal’s forces
– Revised understanding of crystal damage which
explains low temperature irradiation behaviour of
dimensional change and Wigner stored energy
– Identification of high temperature irradiation
dimensional change mechanism
Strategic Funded Projects
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Micro-structural and Fracture Investigations
– Modelling crack growth in complex heterogeneous
brittle materials, GRA/GNSR/6007
– Measurement of micro-structure strains in graphite,
GRA/GNSR/6022
– Micro-structural modelling of the elastic and strength
properties of nuclear graphite, GRA/GNSR/6023
– Experimental investigation into the crack initiation
process in nuclear graphite, GRA/GNSR/6029
– Microstructure/property relationships in unirradiated
and irradiated AGR nuclear graphite,
GRA/GNSR/6034 – NEW
Strategic Funded Projects
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Micro-structural and Fracture Investigations
Strategic Funded Projects
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Micro-structural and Fracture Investigations
Strategic Funded Projects
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Micro-structural and Fracture Investigations
Strategic Funded Projects
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New and Improved Measurement Techniques
– Feasibility study into the use of deep-hole drilling
techniques to measure radial distributions of internal
stress during in-core inspections of graphite fuel
bricks, GRA/GNSR/6030
– Feasibility study into the use of surface-hole drilling
techniques to map internal brick stresses at the
channel wall during in-core inspections of graphite
fuel bricks, GRA/GNSR/6031
– Scope for measurements on irradiated HTR graphite
bricks, GRA/GNSR/6037 – awaiting proposal
Strategic Funded Projects
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Dissemination of Information
– Projects are expected to produce:
o
o
o
o
o
o
Interim reports
Final reports
External, refereed scientific papers
Contributions to conferences, seminars, technical
specialist’s meetings, e.g. INGSM, etc.
Presentations at Graphite Research Meetings
Presentations to the GCDMC for endorsement where
appropriate
Direct Funded Work
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Review and assessment of irradiated sample
measurements
– Routine collection of trepanned samples from AGR
core fuel bricks
– Material property measurements
o
o
o
o
Density
Elastic modulus
Co-efficient of Thermal Expansion (CTE)
Strength
– Development of new and improved techniques
– Measurement of other material properties
Direct Funded Work
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Materials Test Reactor (MTR) programme
– Accelerated ageing obtainable using high-flux
reactor
– Project objective is to provide data to improve the
understanding of the future core component
condition and assess plant lifetime.
Direct Funded Work
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Materials Test Reactor (MTR) programme
– To do this the experiment must:
o
o
o
o
o
Extend the graphite material property database
Improve the understanding of graphite behaviour with
combined oxidisation and irradiation, and creep
Produce results that are translatable to the AGR
operational environment
Overlap with existing data
Produce data in time to provide maximum benefit
Direct Funded Work
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Materials Test Reactor (MTR) programme
– Pilot irradiation has been sanctioned
– Objectives of pilot irradiation are
o
o
o
Demonstrate experiment design & control of
irradiation conditions
Confirm ability to interpret MTR results to AGR
conditions
Cross-check with previous MTR experimental
programmes
Direct Funded Work
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Materials Test Reactor (MTR) programme
– Irradiation facility at NRG, Petten has been selected
– Experiment design and sample collection underway
– Start of irradiation planned for September 2007
Direct Funded Work
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Methods development
– Revised material property modelling
o
Driven by fundamental processes
o
o
o
o
Crystal dimensional change
Closure of porosity
Generation of micro-cracks
Creep model with recoverable strain
Direct Funded Work
Current material model
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Dimensional change
Correlation
CTE
1.0
Linear Dimensional Change (%
)
0.5
0.0
-0.5
-1.0
-1.5
-2.0
-2.5
Perpendicular
-3.0
Parallel
-3.5
0
50
100
150
200
250
300
Dose , EDN (x10^20)
Correlation
Correlation
Correlation
Correlation
3
50
2.5
40
Sigma/Sigmao
You ng's Mod ulus (GP a
45
35
30
" S tr u ct u re "
2
1.5
1
25
20
0.5
15
"P in n in g "
0
0
10
0
50
100
D os e ( 10
Modulus
15 0
20
n cm
-2
ED N )
20 0
50
100
150
200
250
300
D o s e (1 0 20 n c m -2 E D N )
25 0
Correlation
Strength
Direct Funded Work
Proposed material model
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Dimensional change
CTE
1.0
Linear Dimensional Change (%
)
0.5
0.0
-0.5
-1.0
-1.5
-2.0
-2.5
Perpendicular
-3.0
Parallel
-3.5
0
50
100
150
200
250
300
Dose , EDN (x10^20)
C o n n e c tiv ity
D e n s ific a tio n
Linear
P o re G e n e ra tio n
50
3
Sq Root
2 .5
40
35
Sigma/Sigmao
You ng's Mod ulus (GP a
45
30
" Str uct ure "
25
20
15
"Pin ning "
2
1 .5
1
0 .5
10
0
50
100
D os e ( 10
Modulus
15 0
20
n cm
-2
ED N )
20 0
25 0
0
0
50
100
150
D o s e (1 0 2 0 n c m -2 E D N )
200
250
300
Strength
Direct Funded Work
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Methods development
– Realistic and best-estimate stress analysis of graphite
components that include:
o
o
o
o
Fuel End Dose Depressions
Concentric and eccentric fuel in channel
Effects of methane holes and bore cracks
Development of a general probabilistic assessment
method
Direct Funded Work
1.0
z
-1.0
Channel Bore Diameter
Profiles
-2.0
-3.0
Predicted
Measured, 2001
Measured, 2004
-4.0
Layer 04
-5.0
1977
Layer 05
Layer 06
Layer 07
Layer 08
Layer 09
Layer 10
Layer 11
Layer 12
0.00
2907
3837
4767
5697
6628
Core axial position
7558
8488
9418
10348
Predicted
-0.10
Measured
▲Comparison with
measured diameters in 2001
and 2004
-0.20
Difference in Radial Displacement
Bore radial displacement
0.0
-0.30
-0.40
-0.50
-0.60
Comparison with difference
in measured diameters
between 2001 and 2004►
-0.70
-0.80
-0.90
Layer 04
-1.00
1977
Layer 05
2907
Layer 06
3837
Layer 07
4767
Layer 08
5697
Layer 09
6628
Height (mm)
Layer 10
7558
Layer 11
8488
Layer 12
9418
10348
Direct Funded Work
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Core inspections
– Achieved
o
o
o
o
Improved reliability
Reduced dose during trepanning
Ability to trepan high weight loss samples
Ability to TV in CO2 atmosphere
– Under consideration
o
o
Ability to measure channel diameter profiles in CO2
atmosphere
Volumetric survey using eddy currents
Direct Funded Work
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Channel Bore Measurement Unit (CBMU)
Direct Funded Work
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Developed Graphite Trepanning Tool and Hoist
Direct Funded Work
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New Graphite Trepanning Tool and Hoist
Direct Funded Work
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Core condition monitoring
– Class 1 parameters identified:
o
o
o
Fuel Grab Load Trace
Control rod movements
Change in channel power discrepancy
– Investigation levels have been defined
– Monitoring Assessment Panels established at
Hinkley Point B and Hunterston B
o
Quarterly meetings which review reactor monitoring
data with a view to inferring the condition of the
graphite core (cracked bricks, channel straightness)
Direct Funded Work
Fuel Grab Load Trace: Hunterston B R4 2688 crack
in layer 6
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HNB R4 2688 1998, 2004, 2005
-3000
-3100
load (arbitrary)
-3200
-3300
1998
2004
2005
-3400
-3500
-3600
-3700
-7700.00
-7200.00
-6700.00
-6200.00
height (arbitrary)
-5700.00
-5200.00
Direct Funded Work
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Fuel Grab Load Trace: Hunterston B R4 2688 crack
in layer 6
Direct Funded Work
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Whole core modelling and validation
– Whole core static and dynamic models of AGR cores
o
o
o
o
Double axial cracked fuel bricks
Full/half symmetry, 3-D core models
Realistic core driving loads during normal operation
Combined graphite core and support/restraint structure
in seismic models
– Methods to assess
o
o
Freedom for control rod insertion and fuel stringer
movements
Onset of inter-element gapping
Direct Funded Work
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Seismic model
– 3-D, half symmetry
– Total number of nodes
>280,000
– Number of beams,
springs and dampers
>250,000 each
– Execution times of 2436 hours
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Static models are
comparable in size and
scope
Direct Funded Work
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Whole core modelling and validation
– Quarter-scale tilting core rig
o
o
o
o
o
Aluminium bricks
Scale clearances and dimensions
Design and construction complete
Being commissioned with a single layer of bricks
Bricks for additional layers are being procured
– Supplements existing rigs
o
o
Small arrays with full-size components: “IMC Rig”
and “Box-kite Rig”
Large array, eighth-scale plastic rig
Direct Funded Work
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Quarter-scale Rig – Aluminium bricks
Direct Funded Work
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Eighth-scale Rig – Plastic bricks
Direct Funded Work
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Box-kite Rig – Perspex and aluminium
Direct Funded Work
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IMC Rig – Full-size
Graphite Bricks
Magnox Projects
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The Magnox Stations have relatively short
remaining operating lives
– Sizewell A and Dungeness A at the end of 2006
– Oldbury at the end of 2008
– Wylfa during 2010
Research activities are targeted closely to safety
case requirements where the main areas of study
are:
– The weight loss effects of radiolytic oxidation
– Brick cracking
Magnox Projects
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Development of new inspection techniques in
collaboration with British Energy
– Targeting keyway root locations using eddy
current techniques
Review of International Creep models
– Collaboration with Kurchatov Institute, Russia
Magnox Projects
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Feasibility studies into Poisson’s ratio measurement
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–
–
–
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Digital Image Correlation (DIC)
Electronic Speckle Pattern Interferometry (ESPI)
Capacitive Displacement Transducers
Ultrasonic Time of Flight Techniques
Micro-structural studies looking at changes in PGA
microstructure due to radiolytic oxidation.
BE/Magnox Collaboration
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British Nuclear Group (Magnox Electric) buys into
the results of a number of British Energy’s
university projects:
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–
–
–
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GRA/GNSR/6007
GRA/GNSR/6022
GRA/GNSR/6027
GRA/GNSR/6029
British Energy has bought into two of their projects
– Dynamic Young’s modulus methods
– Ultimate tensile strength methods
Summary for FY06/07
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Strategic programme - £420k
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Materials test reactor programme - £1M
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Direct funded monitoring and inspection projects ~£200k
Irradiated properties measurement development ~£60k
Whole core modelling and validation - ~£1.3M