Progress on Solid Breeder Test Program and Needs for TBWG

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

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

4. Mean compaction strain versus time wrt power increases Pre-design analysis • Continuous model • FEM code Osi 650oC A e (%) B J.H. Fokkens NRG, The Netherlands A B CB PB C D Be PB Granular material ecr(t) = A exp(-B/T(K)) s(MPa)p t(s)n time (s) A B p n Constitutive equations for creep simulations FZK-Li4SiO4 12.12 10220 0.65 0.2 MTi 850 oC CEA-Li2TiO3 0.67 7576 0.65 0.18 A J. Reimann, FZK JAERI-Li2TiO3 0.37 6947 0.65 0.19 B e (%) Shallow bed experimental conditions time (s) Constitutive equations have been derived for modeling purposes (HCPB in-pile assembly)

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

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

7. Equivalent stress evolution

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

9. 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 Non-Destructive Diagnostics Under Development(NRG, Petten)

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

11. 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 Need for TBWG 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. 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 For the old parties, the question is if a significant program can be made by: For the new parties: 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. 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 The challenge

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. Proposal to the US community Preparation of the response to the WSG-1 Coordinator 1st iteration! (no information from other new parties yet) • 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. 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.

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. Proposal to the US community Preparation of the response to the WSG-1 Coordinator 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 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

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

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

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

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

22. Purge lines and helium pipes for the proposed 3 submoduels ITER-FEAT EU port plug design Helium pipes for the EU TBM (ITER-FEAT) Port plugs Pipes twisted to avoid neutron streaming 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)

23. Proposal to the US community Preparation of the response to the WSG-1 Coordinator Neutronics and Tritium Transport Tests: why and how • 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. NT submodule with independent temperature and purge gas flow controls Proposed US NT submodule Helium coolant and purge lines The idea is to modify the ITER-FEAT JA He-cooled TBM layout to house the US neutronics and tritium transport submodule

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

26. Test Port ITER Time Schedule H-H D-D Low Duty DT High Duty DT 1 2 3 4 5 6 7 8 9 10 1/12 port2 EU Led WSG-1 Participation/Co- 1 Port development/ Cost sharing Testing Environmental Thermomechanics tests objectives tests3 (3 submodules)4 “A”“B” Half-port Quarter-port JA Led WSG-1 Participation/Co- 1 Port development/ Integration tests (DEMO relevant CTF blanket module) Testing Environmental Neutronics and tritium Cost sharing objectives tests3 transport tests5 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) mm2 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

27. Proposal to the US community Preparation of the response to the WSG-1 Coordinator 2. Concerning the R&D program- what is it? 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 collaborationemphasizes 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 onHelium system technology High temperature helium system technology (>850 oC) 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. Coolant panel/manifold - material (EUROFER), fabrication (joining, welding), testing 200 mm 200 mm 470 mm Beryllium pebbles What is involved in terms of hardware? Ceramic breeder pebbles

31. 2004 2009 2014 2019 2024 DD HH HICU* Out-of-Pile Testing HIDOBE Mockup Testing F&Q EXOTIC 9* ITER Operation Design Database for TBM In-pile partially Basic R&D integrated tests (characterization, Mockup modeling development) Design Analysis Testing F&Q Testing facility preparation Insertion of Insertion of EM TBM* IEA Participation Integrated TBM TBWG, WSG, ITER Interface, EM TBM Design and Analysis An Example R&D Plan

32. Proposal to the US community Preparation of the response to the WSG-1 Coordinator 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

33. 2003 2005 2008 2010 2013 2015 2017 2018 LEGEND 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 ITER First Plasma Thermo-physical properties/design database Initiate Task E Terminate Task E Evaluation Point Tritium inventory in Be Thermo-physical properties/design database E Operate Major Experiment Unit Cell Thermomechanics Terminate Major Experiment E Information Flow R&D Highlighted with Purple color to fit ITER Timeline Submodule Thermomechanics E Nuclear Submodule 1 E Nuclear Submodule 2 E E E Integrated modeling Thermomechanics modeling OP OP T T OP T T OP OP T OP OP T OP T E Prototype Mockup Testing Integrated module fabrication and testing E Prototype Mockup Testing E E ITER TBMs OP Testing Component Design Issues Permeation Rate Measurement Test Sequence for Major Solid Breeder Blanket Tasks (Draft)

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