1. Progress on Solid Breeder Test Program and Needs for TBWG A. Ying/M. Abdou Feb. 24, 2004 UCLA Outline Response to questions raised on thermal creep during last meeting Progress on Solid Breeder Test Program and Needs for TBWG Main contributors for this period of performance: M. Dagher, J. An

2. issues on thermal creep What is the thermal creep, why is it important, and what do we know now? (In fact, thermal creep is not the only phenomenon critical to pebble bed dimensional integrity) Background information The temperature window, and the associated design margin, for the solid breeder pebble bed is relatively narrow. Any deviation from its original position, particularly at the interface may increase the interfacial thermal resistance and cause the breeder operating temperature to go beyond its maximum allowable temperature. (Events such as sintering and melting can be the consequences)

3. Experimental data from the uni-axial compression tests on the ceramic breeder pebble bed show noticeable thermal creep at high temperatures (> 650 o C). J. Reimann, L. Boccaccini, M. Enoeda, A. Y. Ying, Fusion Engineering and Design 61-62 (2002) 319- 331

4. Constitutive equations have been derived for modeling purposes (HCPB in-pile assembly) 0.190.6569470.37JAERI-Li 2 TiO 3 0.180.6575760.67CEA-Li 2 TiO 3 0.20.651022012.12FZK-Li 4 SiO 4 npBA  cr (t) = A exp(-B/T(K))  (MPa) p t(s) n Granular material A B CD Osi 650 o C MTi 850 o C Mean compaction strain versus time wrt power increases  Continuous model  FEM code Constitutive equations for creep simulations Be PB CB PB A B A B J.H. Fokkens NRG, The Netherlands J. Reimann, FZK Shallow bed experimental conditions  time (s)  time (s) Pre-design analysis

5. Challenges remain FEM approach needs to simulate interactions between different deformation dominated regions and among different elements --- High creep (thermal and irradiation) deformation region --- as well as to simulate particle cracking, particle relocations, gap formation, and irradiation swelling. Elastic/Plastic deformation region Pictures from L. Boccaccini, FZK T < 600 o C

6. Test Case (FEM approach) 25 MW/m³ 3 MW/m³ Volumetric heating l 200 mm 11 mm A-A’ B-B’ midplane A’ B’ A B

7. Equivalent stress evolution

8. Need DEM approach for a better understanding of phenomena Account for:  mobility, friction, and sliding  non-standard packing structures Numerical results versus experimental data of normalized creep deformation as a function of time Effective micro-creep model DEM simulation For diffusional creep if  > 40 MPa For power law creep  < 40 MPa Lacking now is the creep database for pebble materials: Experimentally observed orthorhombic packing obtained numerically (26,010 particles) Applied uniform 1 MPa Pressure range at contact: 600 MPa down to 40 MPa

9. Non-Destructive Diagnostics Under Development (NRG, Petten) 1. X-ray Tomography  can provide full mapping of pebble locations in stack, including gross porosity  Can detect pebble relocation, while bed deformation can be traced 2. X-ray (and neutron) photography X-ray photography used to measure compaction

10. Current strategy calls for the IEA collaboration to resolve this research challenge Primary Variables Materials Packing Loadings Modes of operation Irradiation Effect (NRG) Primary & Secondary Reactants: Temperature magnitude/ gradient Differential thermal stress/contact pressure Plastic/creep deformation Particle breakage gap formation Goal: Performance/Integrity prediction & evaluation Partially integrated out-of-pile and fission reactor tests (NRG,ENEA) Finite Element Code (ABQUS, MARC) (NRG, FZK, UCLA) Discrete Element Model (UCLA) Design Guideline and Evaluation (out-of-pile & in-pile tests, ITER TBMs) Database Experimental Program (FZK, JAERI, CEA,UCLA) Thermo-physical and Mechanical Properties Consecutive equations Single/multiple effect experiments (NRG, UCLA)

11. Need for TBWG During the TBWG-11, emphasis was placed on exploring the possibility of collaboration between the parties, aiming to reduce the number of independent TBMs that should be contemporaneously tested in ITER in order to find a solution to the repartition of the space available in the ITER ports Working Sub-Groups were formed according to blanket concepts Recall from the last November meeting --

12. WSG-1: formed by blanket concepts based on ceramic breeder with Helium as coolant and ferritic martensitic steel as structural material  Including 6 parties  Coordinated by Lorenzo Boccaccini (FZK/EU)  First informal meeting held in Tokyo on the 14th of December, 2003. To examine whether or not reduced test space is possible through collaborative efforts and a more integrated testing approach “The main issue is to check the space necessary for performing meaningful testing and, hence, about the possibility to reduce this space by collaboration and a more integrated approach in the testing programme. This will help the subgroup to define the interfaces with ITER that are the first request from the JCT.”

13. The challenge Old parties (EU, JA, RF)New parties (US, CH, KO) 3 half ports assigned Each party occupies its own half of the port 2 half ports agreed during TBWG-11 Clearly, party would be forced to share port to some degree 1) reducing the dimension of the TBMs 2) sharing the position with other modules (in the time schedule), or 3) possibly collaborating within the individual program For the old parties, the question is if a significant program can be made by: 1) to decide as soon as possible the kind of engagement in this line of blanket, and 2) to present a tentative program to support this decision. For the new parties:

14. Input requested by the coordinator for the presentation to TBWG-12 To clarify as soon as possible the intention and the level of participation to this kind of blanket type and to present a tentative programme to support this decision (helium-cooled ceramic breeder blanket concepts) To prepare a preliminary proposal for testing in ITER and port allocation. To extend the level of coordination between the testing programme (that is an objective of the TBWG) including also the points that up to now have been neglected (e.g., PIE for the TBM).

15. 1. Concerning the US’ level of participation-- Recall the strategy-- The US Strategy calls to select He/SB/FS as an option but does not have an independent TBM. Rather, it plans on unit cell and submodule test articles that focus on particular technical issues of interest to all parties. Preparation of the response to the WSG-1 Coordinator Proposal to the US community In response to this strategy-- Two issue-specific submodule tests were proposed: Thermomechanic tests (may include different fabrication techniques) Neutronics and tritium transport tests 1 st iteration! (no information from other new parties yet)

16. Selection of structural material for component fabrication may influence the focus of TBM testing and collaboration Should the US work on both F82H and EUROFER-97? Or only one? If both: Collaboration with JA along the line of F82H: Blanket testing focuses on tritium production and extraction Collaboration with EU along the line of EUROFER: Blanket testing focuses on pebble bed performance integrity and thermomechanics

17. Thermomechanic Tests: why and how  Integrity of breeder and beryllium pebble beds under temperature and stress (and irradiation) loading is the key to the success of the solid breeder blanket performance  Testing conditions (spectrum, volume, nuclear heating) for this test can not be simulated outside of a fusion HOW? The idea is to insert 3 submodules (breeder units only) into EU TBM’s FW structural box. Collaborate with EU on EUROFER fabrication development for FW EU TBM FW structural box Preparation of the response to the WSG-1 Coordinator Proposal to the US community

18. The proposal calls to share the port space to test contemporaneously independent submodules (for example:3) Preparation of the response to the WSG-1 Coordinator Proposal to the US community Main feature: The submodules have independent temperature control.

19. To share the helium cooling system; yet with own independent temperature control US TBMS T P EU HCPB TBM (2001) Cooler Heater The required auxiliary systems (heater and heat exchanger) could be located inside the transporter if necessary Preparation of the response to the WSG-1 Coordinator Proposal to the US community

20. Insertion of independent submodules should minimize interference Preparation of the response to the WSG-1 Coordinator Proposal to the US community Coolant Manifold Purge lines Coolant lines Common coolant line

21. Auxiliary lines (such as coolant and purge) penetrate through EU coolant manifold assembly minimizing disturbances Coolant manifold for the proposed US submodules Purge gas manifold for the proposed US submodules EU Manifold Assembly US Coolant supply line US Coolant return line

22. Need a modified port plug design to accommodate the US’ proposal Issue: “TBM Port Plug should be fixed in short time and it may be practically unchangeable for the all duration of ITER operation” (Note that port plug is currently considered as JCT’s responsibility) Purge lines and helium pipes for the proposed 3 submoduels Pipes twisted to avoid neutron streaming Port plugs Helium pipes for the EU TBM (ITER-FEAT) ITER-FEAT EU port plug design

23. Neutronics and Tritium Transport Tests: why and how Preparation of the response to the WSG-1 Coordinator Proposal to the US community Critical elements in the tritium fuel self-sufficiency assessment for the D-T fuel cycle include production (TBR), extraction, inventory, and permeation How? The idea is to insert a quarter port module to share with JA in a helium-cooled ceramic breeder test port, while collaborating with JA on the F82H fabrication development for FW A relatively large module (detailed port size TBD) may be needed to reduce uncertainty in production and measurement due to heterogeneity

24. The idea is to modify the ITER-FEAT JA He- cooled TBM layout to house the US neutronics and tritium transport submodule Proposed US NT submodule NT submodule with independent temperature and purge gas flow controls Helium coolant and purge lines

25. Schematic view of auxiliary line arrangement in helium-cooled ceramic breeder concepts port EU-led WSG-1 port JA-led WSG-1 port 1288 760 Port 1 (helium cooled)

26. Space/Time Matrix of the Proposed US WSG-1 TBM Program 1: Assuming that EU and JA will be the main developers for the WSG-1 concepts 2. A port size equals 1280 (toroidal) x 1740 (poloidal) mm 2 3. Blanket internal may be different from that of the real module (I.e., no coolant nor breeder/beryllium materials needed-TBD) 4. Consistent with EU’s ITER FEAT TBM scheduled replacement 5. Replacement schedule is 1 year later than JA’s ITER FEAT TBM scheduled replacement Test PortITER Time Schedule H-H 1 2 3 D-D 4 Low Duty DT 5 6 7 High Duty DT 8 9 10 EU Led WSG-1 Port 1 Participation/Co- development/ Cost sharing Testing objectives Environmental tests 3 Thermomechanics tests (3submodules) 4 “A” “B” JA Led WSG-1 Port 1 Participation/Co- development/ Cost sharing Testing objectives Environmental tests 3 Neutronics and tritium transport tests 5 Integration tests (DEMO relevant CTF blanket module) Quarter-port 1/12 port 2 Half-port

27. 2. Concerning the R&D program- what is it? Preparation of the response to the WSG-1 Coordinator Proposal to the US community Need to establish an R&D program to support the proposal with a focus on fabrication and qualification of the proposed TBM before its ITER insertion R&D features for satisfying ITER testing: exclude long term irradiation performance; however, the cyclic effects that are introduced by the ITER pulsed operations should be studied Maximizing international collaboration

28. Initial R&D collaboration emphasizes cross evaluation Review design concepts proposed by the parties perform similar analysis to ensure adequacy (For example: structural analysis for EU Box is currently being performed) Consider modifications/improvements, if any Information exchange on proposed TBMs Other existing international collaborations (such as IEA)

29. Making use of the Leverage on Helium system technology High temperature helium system technology (>850 o C) is considered one of the R&D within the scope of the AGR for Nuclear Hydrogen Initiative Advanced Gas Reactor Fuel Development and Qualification Program

30. What is involved in terms of hardware? Ceramic breeder pebbles Coolant panel/manifold - material (EUROFER), fabrication (joining, welding), testing 200 mm 470 mm Beryllium pebbles

31. An Example R&D Plan

32. R&D Issues for solid breeder blanket TBM  Material fabrication, characterization, procurement (solid breeder, beryllium, ferritic steel structure)  Testing Facility (for out-of-pile and in-pile nuclear submodule tests. For key issues such as ceramic temperature window, material thermomechnaics, interaction, effects of cycling, etc.)  Fabrication Technology (FW, coolant structural panel, manifold)  Auxiliary Systems for TBM (helium cooling and tritium processing)  Instrumentation Development and Integration Preparation of the response to the WSG-1 Coordinator Proposal to the US community

33. Breeder and Pebble Bed Characterization and Development Multiplier and Pebble bed Characterization and Development Blanket Thermal Behavior Advanced In-Situ Tritium Recovery (Fission Tests) Nuclear Design and Analysis (Modeling Development) Fusion Test Modules Design Fabrication and Testing Material and Structural Response Tritium Permeation and Processing Blanket structure fabrication Instrumentation Test Sequence for Major Solid Breeder Blanket Tasks (Draft) E OP Unit Cell Thermomechanics T E OP Submodule Thermomechanics T Nuclear Submodule 1 E OP T 2018 2005 20102003 2008 2013 2015 2017 LEGEND Initiate Task Terminate Task E Evaluation Point OP Operate Major Experiment T Terminate Major Experiment Information Flow Thermo-physical properties/design database E E R&D Highlighted with Purple color to fit ITER Timeline ITER First Plasma Integrated module fabrication and testing E OP Permeation Rate Measurement Thermomechanics modeling EE Integrated modeling Testing Component Design Issues Prototype Mockup Testing E OP T ITER TBMs OP E Prototype Mockup Testing E OP T Nuclear Submodule 2 T OP E Tritium inventory in Be

34. Summary Need processes to derive a US ITER TBM plan Two issue-specific submodule tests are proposed for helium-cooled ceramic breeder blanket concepts Neutronics and tritium transport tests Thermomechanic tests Can this proposal be submitted to WSG-1 for initial discussions? Need inputs to WSG-1 for the preparation of TBWG-12 discussion the intention and the level of participation to helium-cooled ceramic breeder blanket concepts a tentative program to support this decision (helium-cooled ceramic breeder blanket concepts) Proposal can be revised with more inputs from other parties