Preparation of activation experiments for ITER material characterization

Preparation of activation experiments for ITER material characterization and data validation in the Deuterium–Tritium JET campaign T. Vasilopoulou & I. E. Stamatelatos, NCSRD, Greece L. W. Packer & S. Lilley, CCFE, UK P. Batistoni, ENEA, Italy

Roadmap towards fusion 2 -4 GW 38 MW Not in scale 500 MW JET ITER DEMO (in operation) (under construction) (under design) • Fusion power: a safe, clean, and limitless energy source for the future • A fusion reactor builds in the main on three devices: JET, ITER and DEMO • JET is considered as the test bed for ITER technologies HNPS 2016, NCSRD, Athens, 3 -4 June 2016

ITER material characterization ITER materials • structural materials used in the manufacturing of the main in-vessel components • functional materials used in diagnostics and heating systems Why? ITER materials need to satisfy a range of requirements: • their mechanical properties must be maintained in an environment of • o severe mechanical, electro-mechanical and thermal stresses o high radiation field, including neutrons with energies up to 14 Me. V o an intense flux of charged particles, photons and other radiation low activity levels, since neutron activation of the structure can lead to medium-term radiation complicating the handling of components in maintenance or decommissioning operations o long-term activation which requires special treatment, storage or disposal as waste at end of the plant life o HNPS 2016, NCSRD, Athens, 3 -4 June 2016

ACT Project Activation experiments project (ACT): • Nuclear analysis and characterization of real ITER materials • Experiments and simulations performed at JET Scope of the present work Preparation of ITER materials irradiation experiment to be performed during the JET Deuterium–Tritium campaign Updated JET schedule HNPS 2016, NCSRD, Athens, 3 -4 June 2016

Long Term Irradiation System (LTIS) Neutron spectra at LTIS • Installed before the 2015 D-D campaign, filled with activation foils in order to characterize the local neutron field • Will be used in the forthcoming T -T and D-T JET campaigns, carrying dosimetry foils and samples of ITER materials HNPS 2016, NCSRD, Athens, 3 -4 June 2016

ITER materials No. Component Material Supplier Type 1 Vacuum Vessel SS 316 L(N)-IG Outokumpu Plate • Both structural and functional components 1 Vacuum Vessel SS 316 L(N)-IG Industeel Plate 1 Vacuum Vessel SS 316 L(N)-IG Kind Forging 1 Vacuum Vessel SS 316 L(N)-IG Thyssen Forging • Material composition data provided by manufacturers and ITER basic model literature [1] 2 In-wall shield SS 304 (borated) - Borated steel 2 In-wall shield Alloy 660 - 3 First Wall 316 L(N) - - 3 First Wall Cu. Cr. Zr - - 6 Divertor W - Bar, plates 6 Divertor OF-Cu - Plates 7 Divertor XM-19 - Plate forgings 7 Divertor Al-bronze - Forgings 9 Toroidal Field Coils SS 316 L(N) Thyssen Radial plates 9 Toroidal Field Coils Nb 3 Sn BEAS Mixture 9 Toroidal Field Coils SS 316 L - Cover plates 9 Toroidal Field Coils SS 316 L(N) - Cover plates 9 Toroidal Field Coils Nb. Ti - - 9 a Toroidal Field Coils SS 316 L(N) Hyundai TF coil case 9 a Toroidal Field Coils SS 316 L(N) Kind TF coil case 9 a Toroidal Field Coils SS 316 L(N) Daido steel TF coil case • 23 ITER materials studied [1] V. Barabash (2013) ITER IDM: HTN 8 X 3 HNPS 2016, NCSRD, Athens, 3 -4 June 2016

Dosimetry Foils data from FENDL-3. 0 • To monitor neutron fluence • Discs D=18 mm, thickness=1 mm • Selection based on • Response on neutron energy • Half-lives • Material properties (i. e. melting point) • Threshold reactions Ti, Mn, Co, Ni, Fe, Y • Neutron capture reactions Co, Sc, Ta, Fe HNPS 2016, NCSRD, Athens, 3 -4 June 2016

Calculations • European Activation System (EASY-II) • EAF-2010 nuclear data library • D-T plasma source neutron spectrum at LTIS • Detailed MCNP model of JET (tokamak and hall) • Total neutron fluence of 1. 06× 1016 cm-2 (4 months) • Fluence rate of 1. 02× 109 cm-2·s-1 (continuous scheme) • Output • Specific activity (Bq/g) • Dose rate at 1 m (Sv/h) • Detector count rate (cps) • Cooling times ranging from 1 d to 600 d HNPS 2016, NCSRD, Athens, 3 -4 June 2016 Model of JET tokamak

Results: Specific activity (1) Vacuum Vessel Toroidal Field Coils In-wall shield HNPS 2016, NCSRD, Athens, 3 -4 June 2016

Results: Specific activity (2) First Wall TFC conductors Divertor materials HNPS 2016, NCSRD, Athens, 3 -4 June 2016

Results: Dose rate per gr at 1 m • 200 d post-irradiation dose rates per gr at 1 m distance are bellow 1 Sv/h for all materials • The dose rate calculated for material Nb 3 Sn is attributed to the different impurity content and in particular to the high level of Ta resulting in significant 182 Ta production • 200 d post-irradiation the dose rate at 5 cm distance from Nb 3 Sn material is ≈ 40 μSv/h HNPS 2016, NCSRD, Athens, 3 -4 June 2016

Concluding remarks • The preparation for D-T irradiation experiment has been completed • ITER samples will be installed in LTIS in 2018 for the T-T campaign and in 2019 for the D-T campaign • Manageable activities and dose rates are expected to be acquired after irradiation • For accurate prediction of activity levels and dose rates, exact knowledge of impurity levels is of outmost importance • Unique opportunity to study ITER materials under real fusion conditions HNPS 2016, NCSRD, Athens, 3 -4 June 2016

Thank you for your attention! JET tokamak dora@ipta. demokritos. gr