MTR Project ACCENT

1. MTR Project ACCENT T.O. van Staveren, NRG A.J. de Koning, NRG M. Davies, Frazer Nash Consultancy September 18, 2013

2. MTR Project ACCENT • Goal • Status of project • Design • Samples • Irradiation • PreIEand PIE program

3. MTR Project ACCENT • MTR: Materials Test Reactor • ACCENT: AGR Carbon Creep experimENT • Goal: Provideirradiation creep data on (radiolyticallyoxidised) graphite • Input tomodelsthatpredictgraphite property changes for EDF Energy Advanced Gas-cooled Reactors

4. Plan • Irradiategraphite samples at high temperatureunder stress in the High Flux Reactor in Petten • Perform multiple irradiationand post-irradiationcharacterisation stages todeterminegraphiteproperties at different dpavalues • Load virginandradiolyticallyoxidised samples todetermineirradiation creep behaviour at low / high neutron doseandweightloss

5. Project status Conceptual design Phase I Irradiation: 1 cycle with ~0.7 dpa increment Phase I Post-irradiation characterisation Assembly and commissioning Detailed design Assembly and commissioning Sample machining Pre-characterisation Phase II Irradiation: 6 cycles with ~4 dpa increment

6. Project status Program on schedule: • Start of design phase: mid-2012 • Machiningof radiolyticallyoxidisedspecimens: 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

7. Design • Samples loaded in 6 modules • Instrumentedholderfor modules with 24 thermocouples • Sample target temperature: 420°C • 10 MPa on stressed samples appliedby gas filledbellows • Samples under inert atmosphere

8. Temperature control • Instrumentedholderwith 24 thermocouples → online temperature monitoring • Temperaturecontrolledby He/Ne gas mixture in 2nd containment • SiCtemperature monitors → post mortemtemperature analysis of samples andbellows

9. Bellow system • 4 samples per module • 2 samples under stress • Helium gas filledbellows • 10 MPareachedwhen experiment is at temperature • Irradiationtemperature at bellowsdetermines load on samples • Filler andpressurepartsforarticulationand heat isolation Bellow Pressure part Sample

10. Samples • 24 samples in 6 modules • Twopaired samples per module • One sample in a pair is loadedto 10 MPa • Target samples give ‘3 Experiments’ • Virgin Gilsographite → ‘Experiment 2’ • Radiolyticallyoxidisedgraphite at intermediate neutron doseandweightloss (ex-Blackstone) → ‘Experiment 3’ • Radiolyticallyoxidisedgraphite at high neutron doseandweightloss (ex-AGR, ex-Blackstone) → ‘Experiment 1’

11. Samples at start of Phase I Experiment 2: virgin graphite Dimensional change (%) 2 dpa 3 1 Experiment 1: radiolyticallyoxidised graphite, ex-AGR and ex-Blackstone Experiment 3: radiolyticallyoxidised graphite, ex-Blackstone

12. Sample geometries • 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%

13. Sample machining (EXP 1) • Samples radiolyticallyoxidised 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

14. Pre-characterisation After pre-stress testing Before pre-stress testing Pre-stress testing • Photography • Dimensions • Mass • CTE (3 directions) • DYM (3 directions) • Electrical resistivity • ‘Standard’ XRD • XRD texture • Tomography • Loading samples to 10 MPa • DIC data recording • Photography • Dimensions • Mass • CTE (3 directions) • DYM (3 directions) • Electrical resistivity • ‘Standard’ XRD • XRD texture • Tomography 10 MPa

15. Assembly • Module partsandradioactive samples assembled in glove box • Bellowspressurisedwith helium • Orbital welding of modules • Leaktightnesstesting

16. Phase I irradiation • Irradiationfrom 13 Julyto 6 August 2013 • dpa target reached: 0.7 dpa • Stabletemperaturesthroughoutirradiation • Analysis SiCtemperature monitor ongoing • AnnealSiC monitors at increasingtemperatures • Measureelectricalresistivity of SiCaftereachannealing step

17. Dismantling • Modules puncturedto check forleaking of modules andbellowsduringirradiation • Modules openedwithmilling machine in hot cell • Samples successfullyretrievedfrom modules in hot cell

18. PIE • Startedbeginning of August • End: last week • Measurements: • Photography • Dimensions • Mass • CTE • DYM • Electrical resistivity • ‘Standard’ XRD • XRD texture • Tomography • Results…

19. Next steps • Continue assessment of Phase I irradiation • Analysis of SiCtemperature monitor sets • Analysis of neutron dosimetry sets • Report post-irradiationcharacterisationmeasurements • Assemble ACCENT Phase II irradiation experiment • Start Phase II irradiation

20. Conclusions • Successfullmachiningand pre-characterisation of radiolyticallyoxidisedgraphite samples • Phase I irradiationcompleted: • dpa target reached • Stabletemperaturesthroughoutirradiation • Confirmation of irradiationtemperature on-going • Successfullcompletion of PIE measurements • Project on scheduleforPhase II irradiation