Transmutation Effects in Fusion Reactor Materials: Critical Challenges & Path Forward: Helium, Tritium and Hydrogen Effects I
Sponsored by: TMS Structural Materials Division, TMS: Nuclear Materials Committee
Program Organizers: Arunodaya Bhattacharya, Oak Ridge National Laboratory; Steven Zinkle, University of Tennessee; Philip Edmondson, The University Of Manchester; Aurelie Gentils, Université Paris-Saclay; David Sprouster, Stony Brook University; Takashi Nozawa, National Institutes for Quantum and Radiological Science and Technology (QST); Martin Freer, University of Birmingham
Tuesday 8:00 AM
March 21, 2023
Room: 27B
Location: SDCC
Session Chair: Steven Zinkle, University of Tennessee; Hiroyasu Tanigawa, QST Japan
8:00 AM Invited
He Irradiation of W First-wall Materials: Parameters at Stake for the Bubble Creation, Behaviour and Impact on Tritium Trapping: Elodie Bernard1; Ryuichi Sakamoto1; Céline Martin1; Floriane Montupet-Leblond1; Mickaël Payet1; Etienne Hodille1; Arkadi Kreter1; Loic Corso1; Frédéric Leroy1; Stefano Curiotto1; Christian Grisolia1; 1CEA
Plasma-facing materials are submitted to intense fluxes of He and H isotopes (H, D and radioactive T transmutating as He), which can jeopardize preservation of their key properties throughout operation. He impact on the material microstructure will be presented, with experimental data from fusion devices to nanosciences studies to characterize He bubble formation, characteristics and evolution. Then, we will address consequences for T inventory through T2 gas-loading experiments, a high sensitivity technique free from any additional defect creation in the material.
8:40 AM
Thermonuclear Fusion: Some Open Issues Concerning Tritium: Christian Grisolia1; Elodie Bernard1; Etienne Hodille1; Floriane Montupet-Leblond1; Mickael Payet1; Marco Utili1; Silvano Tosti1; Ion Cristescu1; samuel Peillon1; François Gensdarmes1; Arnaud Bultel1; 1CEA Cadarache
During the operation of a fusion machine, large amounts of tritium flow through the facility and interact with materials that can be damaged by neutrons. Particles are also produced. Even if tritium is weakly radiotoxic, its release into the environment must be avoided and tritium permeation controlled. The main problems related to the use of tritium in a fusion machine will be first reviewed.Secondly, tritium permeation studies in Eurofer (low activation steel) will be presented with their associated modelling. Active or passive permeation barriers will be described. he study of tritiated particles indicates that tritium is trapped on their surfaces that can be charged to saturation even at the low tritium pressure experienced in a fusion machine. They can thus contribute strongly to the tritium source term in case of a loss of vacuum accident (LOVA). We will show how to cope with these difficulty by isotopic exchange.
9:00 AM
Optimization of Tritium Breeding in Molten Salt Blankets: Materials and Geometries: Vittorio Badalassi1; 1Oak Ridge National Laboratory
The blanket is a key fusion reactor component that must fulfill several roles simultaneously: radiation shielding, tritium breeding, heat extraction, and structural robustness. Here we analyze a not much investigated but believed promising blanket concept based on molten salts breeding and cooling. The advantages of molten salt blankets are low MHD effects, flow at near atmospheric pressure, possible high temperatures, and good heat transfer properties. The drawbacks are structural material compatibility and chemistry control. Here we analyze molten salt blankets with respect to the Tritium Breeding Ratio (TBR) and material compatibility to test the capability of such MS breeders to reach high TBR and be feasible blankets. The nuclear quantities are evaluated with various molten salts via the MCNP code: TBR, nuclear heating, neutron flux, displacement damage, and helium production are reported and discussed. We present an optimization exercise and an optimized configuration of a molten salt blanket.
9:20 AM Cancelled
Tritium Retention in Beryllium and Titanium Beryllide under Neutron Irradiation to High Damage Doses: Vladimir Chakin1; Ramil Gaisin1; Rolf Rolli1; Michael Duerrschnabel1; Michael Klimenkov1; 1Karlsruhe Institute of Technology
Titanium beryllide TiBe12 is a promising neutron multiplier material for the DEMO blanket because it has comparative advantages over pure beryllium such as less swelling, higher hardness as well as corrosion resistance. Under neutron irradiation, both beryllium pebbles and titanium beryllide produce tritium and helium. High-dose neutron irradiation of beryllium and titanium beryllide at relevant temperatures, followed by thermal-programmed desorption tests, can provide necessary data for the operation design of the blanket. The HIDOBE experiment in the High Flux Reactor (HFR) included irradiation of beryllium and titanium beryllide at 640-1040 K to damage doses of 11-37 dpa.A strong tritium decrease of the retention occurs at highest irradiation temperatures to 20-50 % to the low temperatures for beryllium and to zero for titanium beryllide. A physical model of tritium and helium release and retention behavior for neutron-irradiated beryllium and titanium beryllide was adapted and developed based on obtained experimental results.
9:40 AM Break
10:00 AM Invited
Helium Effects on Mechanical Properties of (RA)FM Steels: Jean Henry1; Yong Dai2; Ermile Gaganidze3; 1Université Paris-Saclay, CEA; 2Paul Scherrer Institut; 3Karlsruhe Institute of Technology
The high quantities of gaseous transmutation products, in particular Helium, generated in the structural steels of in-vessel components of future fusion reactors have long been a subject of concern. The potentially deleterious effects of the accumulated Helium, acting synergistically with displacement damage, on bulk mechanical properties have been investigated using fission neutron irradiations of RAFM steels doped with 10B, 58Ni or 54Fe isotopes, irradiation in spallation conditions and high energy He implantation using cyclotrons. Based on data obtained using these techniques, this presentation aims to give an overview of He-induced effects on the mechanical behaviour of FM steels, with emphasis on tensile and impact properties. While the simulation experiments have generated useful data and have advanced our understanding of He-induced effects, each technique has specific drawbacks. Therefore, a high intensity 14 MeV neutron source, such as the planned IFMIF-DONES facility, is urgently needed!
10:40 AM
The Effect of Helium on Cavity Swelling in Dual-ion Irradiated Fe and Fe-10Cr Ferritic Alloys: Yan-Ru Lin1; Arunodaya Bhattacharya1; Steven Zinkle2; 1Oak Ridge National Laboratory; 2University of Tennessee
To gain fundamental insights into the He effects on cavity swelling, high purity Fe and Fe-10 wt.% Cr ferritic model alloys were irradiated with 8 MeV Ni ions and co-implanted He ions at 500°C up to 30 dpa with He implantation rates of 0.1, 10 and 50 appm He/dpa. By transmission electron microscopy, a bimodal cavity size distribution was observed in the 10 and 50 appm He/dpa samples, but not for 0.1 appm He/dpa. Cavity swelling was maximized at intermediate He implantation rates of ~10 appm He/dpa for both Fe and Fe-10Cr alloys. The cavity swelling behavior as a function of He implantation rate appears to be controlled by the He/dpa-dependent variation of cavity sink strengths. Treating small bubbles as biased sinks for interstitial absorption can significantly increase the ratio of biased to unbiased sink strengths (Q) and results in maximized cavity swelling for a Q ratio close to one.
11:00 AM
Effect of Helium on Low-temperature Hardening/Embrittlement (LTHE) in Neutron Irradiated Isotopically Tailored RAFM Steels: Arunodaya Bhattacharya1; Steven Zinkle2; Samara Levine2; Mark Gilbert3; Charles Kessel4; Hiroyasu Tanigawa5; 1Oak Ridge National Laboratory; 2University of Tennessee; 3UKAEA; 4Oak Ridge National Lab; 5QST
Reduced activation ferritic-martensitic (RAFM) steels are promising candidates for fusion first-wall/blanket structures. A major technical gap in understanding fusion-specific radiation damage is the high transmutation rates under the fusion neutron spectra as compared to fission neutrons. Here, different degradation scenarios associated with transmutation-induced helium generation in RAFM steels will be presented. Isotopic tailoring of F82H using 58/60Ni addition was used to stimulate helium generation during HFIR neutron irradiations up to ~86 dpa, >930 appm He. Based on HFIR data, the effect of He on low-temperature hardening and embrittlement (LTHE) will be elucidated. Irradiation hardening and ductility loss results are compared with historical He effect data from spallation neutron (SPN) irradiations, highlighting significant over-prediction of the effect of He on tensile properties after SPN irradiations as compared to test reactor irradiations on isotopically tailored steels. Microstructural understanding of the effect of He on LTHE of HFIR irradiated steels will be discussed.