MTR Project ACCENT

T.O. van Staveren, NRG

A.J. de Koning, NRG

M. Davies, Frazer Nash Consultancy

September 18, 2013

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MTR Project ACCENT

• Goal• Status of project• Design• Samples• Irradiation• PreIE and PIE program

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MTR Project ACCENT

• MTR: Materials Test Reactor• ACCENT: AGR Carbon Creep experimENT• Goal: Provide irradiation creep data on

(radiolytically oxidised) graphite– Input to models that predict graphite property changes

for EDF Energy Advanced Gas-cooled Reactors

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Plan

• Irradiate graphite samples at high temperature under stress in the High Flux Reactor in Petten

• Perform multiple irradiation and post-irradiation characterisation stages to determine graphite properties at different dpa values

• Load virgin and radiolytically oxidised samples to determine irradiation creep behaviour at low / high neutron dose and weight loss

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Project status

Conceptual design

Detailed design

Sample machining Pre-characterisation

Assembly and commissioning

Phase I Irradiation: 1 cycle with ~0.7 dpa

increment

Phase I Post-irradiation characterisation

Assembly and commissioning

Phase II Irradiation: 6 cycles with ~4 dpa

increment

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Project status

Program on schedule: Start of design phase: mid-2012 Machining of radiolytically oxidised

specimens: February 2013 PreIE: Spring 2013 Module assembly: June 2013 Phase I Irradiation: July 2013 PIE: August / September 2013• Assembly Phase II: October 2013• Phase II irradiation: November 2013

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Design

• Samples loaded in 6 modules• Instrumented holder for

modules with 24 thermocouples

• Sample target temperature: 420°C

• 10 MPa on stressed samples applied by gas filled bellows

• Samples under inert atmosphere

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• Instrumented holder with 24 thermocouples → online temperature monitoring

• Temperature controlled by He/Ne gas mixture in 2nd containment

• SiC temperature monitors → post mortem temperature analysis of samples and bellows

Temperature control

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Bellow system

• 4 samples per module• 2 samples under stress• Helium gas filled bellows• 10 MPa reached when

experiment is at temperature– Irradiation temperature at

bellows determines load on samples

• Filler and pressure parts for articulation and heat isolation

600mm

750mm

75mm

CL core 3

00mm

Bellow

Pressure part

Sample

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Samples

• 24 samples in 6 modules– Two paired samples per module– One sample in a pair is loaded to 10 MPa

• Target samples give ‘3 Experiments’– Virgin Gilso graphite → ‘Experiment 2’– Radiolytically oxidised graphite at intermediate neutron

dose and weight loss (ex-Blackstone) → ‘Experiment 3’– Radiolytically oxidised graphite at high neutron dose

and weight loss (ex-AGR, ex-Blackstone) → ‘Experiment 1’

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Samples at start of Phase I

dpa

Dim

ensi

onal

cha

nge

(%)

2

Experiment 2: virgin graphite

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Experiment 3: radiolytically oxidised graphite, ex-Blackstone

1Experiment 1: radiolytically oxidised graphite, ex-AGR and ex-Blackstone

Sample geometries

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Experiment 1• Sample machined from flexure tested beams,

ex-AGR, ex-Blackstone• 6 x 6 x 5.5 mm• Max. weight loss 37%

Experiment 2• Virgin samples• 12.5 x 6 x 5.5 mm• Laser engraving on one side

Experiment 3• Samples machined from cylinders irradiated in

Blackstone Phase I• 11.8 x 6 x 5.5 mm• Max. weight loss 8%

Sample machining (EXP 1)

• Samples radiolytically oxidised in AGR and High Flux Reactor Petten Blackstone irradiation

• Flexural tested beams, fracture surface ground back to give specimen pairs

• Marking of specimen needed to guarantee maintaining orientation relationship: grinding of corner

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Pre-characterisation

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Pre-stress testing

Photography Dimensions Mass CTE (3 directions) DYM (3 directions) Electrical resistivity ‘Standard’ XRD XRD texture Tomography

10 MPa

Loading samples to 10 MPa

DIC data recording

Photography Dimensions Mass CTE (3 directions) DYM (3 directions) Electrical resistivity ‘Standard’ XRD XRD texture Tomography

Before pre-stress testing

After pre-stress testing

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Assembly

• Module parts and radioactive samples assembled in glove box

• Bellows pressurised with helium• Orbital welding of modules• Leak tightness testing

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Phase I irradiation

• Irradiation from 13 July to 6 August 2013• dpa target reached: 0.7 dpa• Stable temperatures throughout irradiation• Analysis SiC temperature monitor ongoing

– Anneal SiC monitors at increasing temperatures– Measure electrical resistivity of SiC after each

annealing step

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Dismantling

• Modules punctured to check for leaking of modules and bellows during irradiation

• Modules opened with milling machine in hot cell• Samples successfully retrieved from modules in

hot cell

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PIE

• Started beginning of August• End: last week • Measurements:

– Photography– Dimensions– Mass– CTE– DYM– Electrical resistivity– ‘Standard’ XRD– XRD texture– Tomography

• Results…

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Next steps

• Continue assessment of Phase I irradiation– Analysis of SiC temperature monitor sets– Analysis of neutron dosimetry sets

• Report post-irradiation characterisation measurements

• Assemble ACCENT Phase II irradiation experiment

• Start Phase II irradiation

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Conclusions

• Successfull machining and pre-characterisation of radiolytically oxidised graphite samples

• Phase I irradiation completed:• dpa target reached• Stable temperatures throughout irradiation• Confirmation of irradiation temperature on-going

• Successfull completion of PIE measurements• Project on schedule for Phase II irradiation