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At least 235 records · Page 13

MELCOR Model of the Molten Salt Tritium Transport Experiment (MSTTE)

This report summarizes the FY24 activities to model the Molten Salt Tritium Transport Experiment (MSTTE) using MELCOR. Summarized are the approaches used in construction of the MELCOR methods used for modeling, the construction of the MELCOR deck and the thermohydraulic calculations. The results show good comparison with previously reported calculation data, providing confidence in MELCOR to model experiments in the future.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

Considerations for the Development of a Regenerable LANA.75 Bed for Tritium Storage

LaNi4.25Al0.75 or LANA.75 has been used by the Savannah River Site Tritium Facilities for decades to safely store hydrogen isotopes • High molar density at moderate pressures (~1000x that of gas at STP) = less glovebox space • Can be used as a pump by varying temperature = fewer moving parts • Can deliver He-3 free gas = fewer unit operations • Beds are limited life components due to accumulation of He-3 • Formation of “heel” • Inventory hold-up • Reduced capacity • Eventual weeping of He-3

STAACK, Gregory [Savannah River National Laborator↗

Mechanical Properties of Tritium Precharged and Aged Additively Manufactured Austenitic Stainless Steel

What is “known” about tritium effects on austenitic steel • Decreased ductility and fracture resistance • Hardening/strengthening • Hydrogen is believed to interact with dislocations, grain boundaries, vacancies, and other microstructural features2 • But what about AM?? • Similar behavior/trends? • How do we account for differences between AM and forged? • Can we design based on material with similar microstructure that has already been tested?

Wieber, Natalie [Savannah River National Laborator↗

Tritium Containment Vessel Response to Thermal and Mechanical Abuse Environments for Fire Safety Assessments

This report evaluates leakage behavior from tritium containment vessels under thermal abuse and combined thermal-mechanical abuse conditions to better understand safety implications for releases occurring in a fire scenario. Surrogate gases were used for all tests in this report. Leakage through the valves from thermal pressurization was observed when heating rates >0.8°C/s were sustained to >300°C. Gas plumes were visualized from vessels that were heated above 260°C and then dropped.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

A Brief Review of Technologies for Separating Tritium from the Aqueous Effluent of Reprocessing Plants

The scope of this letter report encompasses a review of technologies applicable to separating tritiated water from light and heavy water with a focus on wastewater arising from the reprocessing of UNF. Reports considering flowsheet options for tritium management are also reviewed. The main objective of this letter report is to support consideration of programmatic opportunities for the Materials Recovery and Waste Form Development (MRWFD) Campaign within the Department of Energy’s Office of Nuclear Energy.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Evaluating Lithium-Lead Mixtures for Increased Tritium Breeding in Fusion Energy Blanket Systems: Exploring the Impact of Composition and Temperature

This project investigates hypo- and hyper-eutectic liquid lithium-lead (PbLi) mixtures as a coolant in fusion blanket systems, with a focus on testing the compatibility of compositions with better tritium breeding ratios (TBR). The 12-month study concentrates on static corrosion experiments, comparing silicon carbide (SiC) corrosion rates in Li-rich and eutectic Li-Pb mixtures, and examining interactions between Mo and PbLi. The research seeks to determine the maximum operating temperatures for this material combination, acknowledging the balance between Li-Pb melting temperature and achievable TBR to unlock new opportunities for blanket design. This work lays the groundwork for future collaboration between Kyoto Fusioneering and Oak Ridge National Laboratory (ORNL). Findings could enhance the TBR of fusion blanket designs, and impact fusion energy development by confirming material compatibility between different Li-Pb mixtures with SiC and Mo at higher temperatures, including at temperatures relevant for very high-temperature blankets (1,000 °C), which could enable higher electricity conversion efficiencies and commercial applications using process heat.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Fundamental Studies of Tritium Formation and Diffusivity in Pure and Defective Zircaloy-4 Getters

Zirconium (Zr) alloys have excellent mechanical properties at high temperature and are resistant to corrosion in different environmental conditions. These alloys are used as tritium (3H or T) getters in nuclear reactors due to their low absorption cross section to thermal neutrons and excellent thermo-mechanical properties. Zr alloys have better mechanical and thermal properties than many other refractory alloys including stainless steel. After the irradiation of TPBAR by neutron flux, 3H produced during irradiation diffuses though the pellets and is captured by the getter. 3H chemically reacts with Zr metal to form metal hydride (ZrTx). Hydrides thus formed are brittle and adversely affect the mechanical and thermal properties of alloys. The lattice mismatch at the interface of alloy and metal hydrides also creates a stress that significantly reduces the alloy’s performance and operation life. Therefore, understanding the behavior of 3H and its species becomes significant as fuel burnup is increased, which leads to increase in hydrogen pickup and oxide formation.

Duan, Yuhua↗

Advanced Tritium Process Analytics and Optimization via a Digital Twin, SRNL-TR-2023-00550

Improving the process knowledge and understanding of TCAP can be achieved by incorporating advanced tools. This project addresses “Advanced analytics for modeling, forecasting, & optimization of the tritium refinement process” and is being applied to the TCAP process. The value of digitization and advanced analytics for TCAP data are tracking of gas mixtures & inventories is presently a manual effort that is rather cumbersome. Incorporating some automation into the data capture will reduce errors and storing data in an accessible database that can be used for tracking as well as process improvements. In addition, the database approach will enable longer term history to be maintained rather than the current practice of deleting data after six months. The digitized and automated data will allow for models to be developed for the process and will enable the forecasting and optimization.

Korinko, Paul S.↗

Managing Tritium in Water.

Fermilab’s program to monitor and manage low levels of tritium in surface and sewer water on the laboratory site.

Fermilab, Fermilab↗

First-principles studies of the concentration-dependent tritium diffusion in the zirconium hydrides with and without Sn impurity

We performed first-principles calculations to study the 3 H diffusion in the zirconium hydrides with or without Sn impurity. Our results show that the formation of Zr 3 H x becomes preferable as the 3 H concentration increases. Based on the most stable configurations of Zr 3 H x (x = 0.5, 1.0, 1.5, 2.0), we studied the interstitial 3 H diffusion with or without Sn impurity. The results show that the interstitial 3 H diffusion becomes less probable in the hydrides with a higher 3 H concentration. When introducing a substitutional Sn impurity, the diffusion barriers increase. Therefore, the substitutional Sn in the diffusion pathway hampers the 3 H diffusion in Zr hydrides.

36 MATERIALS SCIENCE↗

Relative sensitivity of plastic scintillator: A comparative analysis with 60 Co gamma rays, deuterium–deuterium, and deuterium–tritium neutrons

A plastic scintillator has found extensive application in the realm of high-energy physics and national security science. Many applications in those fields often involve the simultaneous production of photons, neutrons, and charged particles, which makes the relative sensitivity information for these different radiation types important. In this study, we have adopted a multi-head detector comprised of a plastic scintillator and high gain phototubes, which provides a large dynamic range and linearity. A comparative study on the relative sensitivities of plastic scintillators was facilitated by adopting three distinct radiation calibration sources (i.e., 60 Co γ rays, DD neutrons, and DT neutrons). Neutrons from a DD source generate a comparable level of scintillation to gamma rays emitted by 60 Co (i.e., 60 Co-γ/DD-n = 0.92 ± 16%). DT neutrons induce ~3.5 times the scintillation observed with DD neutrons (i.e., DT-n/DD-n = 3.5 ± 28%). In addition, the Geant4 simulation granted us valuable insights into the relative sensitivity of the scintillator. This comparative study will provide a useful database for users in diverse applications.

47 OTHER INSTRUMENTATION↗

Relevance of Tritium Breeder Irradiation Testing in a Fusion Prototypic Neutron Source

A fusion prototypic neutron source (FPNS) will play a fundamental role in testing and developing fusion materials that can withstand the harsh fusion environment. We conducted a thorough assessment to determine whether blanket materials would benefit from FPNS testing. Because of the cross sections for the various blanket materials, lithium-containing materials can generally be tested adequately using existing fission irradiation capabilities instead of waiting for or relying solely on future FPNS experiments. However, non-lithium blanket materials, such as beryllium multipliers and flow channel inserts, should be tested under a fusion neutron spectrum.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Isotope physics of heat and particle transport with tritium in JET-ILW type-I ELMy H-mode plasmas

As part the DTE2 campaign in the JET tokamak, we conducted a parameter scan in T and D-T complementing existing pulses in H and D. For the different main ion masses, type-I ELMy H-modes at fixed plasma current and magnetic field can have the pedestal pressure varying by a factor of 4 and the total pressure changing from <?CDATA $\beta_{\mathrm{N}} = 1.0$?> β N = 1.0 to 3.0. We investigated the pedestal and core isotope mass dependencies using this extensive data set. The pedestal shows a strong mass dependence on the density, which influences the core due to the strong coupling between both plasma regions. To better understand the causes for the observed isotope mass dependence in the pedestal, we analysed the interplay between heat and particle transport and the edge localised mode (ELM) stability. For this purpose, we developed a dynamic ELM cycle model with basic transport assumptions and a realistic neutral penetration. The temporal evolution and resulting ELM frequency introduce an additional experimental constraint that conventional quasi-stationary transport analysis cannot provide. Our model shows that a mass dependence in the ELM stability or in the transport alone cannot explain the observations. One requires a mass dependence in the ELM stability as well as one in the particle sources. The core confinement time increases with pedestal pressure for all isotope masses due to profile stiffness and electromagnetic turbulence stabilisation. Interestingly, T and D-T plasmas show an improved core confinement time compared to H and D plasmas even for matched pedestal pressures. For T, this improvement is largely due to the unique pedestal composition of higher densities and lower temperatures than H and D. With a reduced gyroBohm factor at lower temperatures, more turbulent drive in the form of steeper gradients is required to transport the same amount of heat. This picture is supported by quasilinear flux-driven modelling using TGLF -SAT2 within Astra . With the experimental boundary condition TGLF -SAT2 predicts the core profiles well for gyroBohm heat fluxes <?CDATA ${\gt}15$?> > 15 , however, overestimates the heat and particle transport closer to the turbulent threshold.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗