Recent Publications

Fluid dynamics simulations of gas retention systems for shattered pellet injectors

Á. Gyenge, B. Farkas

Hydrogen isotope permeation in liquid Li17Pb83 supported by pure V and V alloy substrates

Yuya Ando, Yuto Murata, Takuya Nagasaka, Teppei Otsuka

Tritium Management in an All-Carbon First Wall Tokamak Reactor

James Davis, Sellathurai Suppiah, Ezekial Unterberg, Donald Ryland, Peter Stangeby

University of Toronto, Canadian Nuclear Laboratories, Oak Ridge National Laboratory

An Extended Study on the Release of Radiogenic Helium-3 from Uranium Tritide

J. Northall, E. H. Norris

AWE

Investigation of Impurity Gas Cracking Catalysts for Tokamak Exhaust Processing Systems

Yuki Edao, Katsumi Sato

Rokkasho Institute for Fusion Energy

Neutronics Analysis of a Water-Cooled Blanket with a Be 12 Ti Reflector to Enhance Tritium Breeding

Seonghee Hong, Sungjin Kwon

Korea Institute of Fusion Energy

Preliminary design of DTT vacuum pumping system

Mariagrazia Romano, Michele Fincato, Paolo Innocente, Christian Avanzato, Luca Balbinot, Andrea Belpane

University of Tuscia

Experimental evaluation of the performance and operational characteristics of a helium circulator for Test Blanket System applications

Chang Wook Shin, Suk-Kwon Kim, Dae-Sik Chang, Myungho Kim, Seok-Kwon Son, Hyung Gon Jin, Dong Won Lee, Youngmin Lee, Mu-Young Ahn

Korea Atomic Energy Research Institute, Korea institute of Fusion Energy

Determining neutral fueling response to RMPs in MAST using a multi-reservoir particle balance model and EMC3 EIRENE

Kurt Flesch, James Harrison, Andrew Kirk, Ian Waters, Heinke Frerichs, Oliver Schmitz, Livia Casali

The application of certain configurations of resonant magnetic perturbations (RMPs) has been shown to cause a plasma pump-out in both L- and H-mode discharges at MAST. In this paper we discuss the impact of neutral fueling on this density reduction. The neutral fueling and average particle confinement time $τ_p$ of the main ion species were calculated using a 0-D particle balance analysis. When the RMPs were applied, it was found that there was an increase in ionizations and a 15$\%$ reduction in $τ_p$ for L-mode discharges and a similar result for inter-ELM (edge localized modes) periods of H-mode discharges. A time-dependent global multi-reservoir particle balance (MRPB) was developed, which included atomic and molecular reservoirs, to further investigate the role neutrals had on the density change. We discuss how this model was able to accurately reproduce the experimentally measured density reduction and ionization increase due to either a reduction in $τ_p$ or a reduction in particle fueling efficiency. Results from EMC3-EIRENE modeling indicate this change could be attributed to neutral particle fueling occurring in locations with now-opened field lines due to the chaotic edge-region from RMP applications.

Neural network predictions of plasma confinement loss in Wendelstein 7-X pellet-fueled discharges

K. C. Hammond, J. -P. Bähner, J. Baldzuhn, S. Bozhenkov, K. J. Brunner, A. Dinklage, E. Edlund, G. Fuchert, M. Huck, A. I. Mohammed, et al.

The energy confinement time is a key parameter of a magnetized fusion plasma, helping to determine whether ignition can occur. Experiments in tokamaks and stellarators have shown that the confinement time can be improved via pellet injection. The state of enhanced confinement brought about by a given pellet typically deteriorates over time unless and until a subsequent pellet is injected. In this work, we develop a data-driven model that predicts, at any moment, the remaining time before a plasma in Wendelstein 7-X (W7-X) will lose its enhanced confinement state. This "remaining time" metric effectively sets a deadline for when the next pellet must be injected in order to steadily maintain a high confinement time. We describe the development and training of the model and compare its predictions to observations from previous experiments. At least 90% of the model predictions are accurate to within 51 ms, which is below the typical W7-X energy confinement time as well as the minimum time separation between subsequent pellet injections. The model can be evaluated rapidly and could be suitable for use in a control system that optimizes the pellet injection rate in real time.

Real-time feedback control of ELM frequency using divertor gas puffing and its effects on tungsten-induced radiation and plasma performance in KSTAR

Minseok Kim, Young-Ho Lee, SangKyeun Kim, Minwoo Kim, Sang-hee Hahn, Hiro J. Farre-Kaga, Ricardo Shousha, Juhyeok Jang, SooHyun Son, Yoon Seong Han, et al.

The edge-localized mode (ELM) frequency ($f_{\mathrm{ELM}}$) was successfully controlled in real time on KSTAR using a proportional-integral (PI) feedback controller, employing a $\mathrm{D}_2$ divertor gas puff as the actuator under tungsten lower-divertor conditions. The controller accurately tracked a two-step target---a 30 Hz increase in $f_{\mathrm{ELM}}$ for 4 s, followed by a 30 Hz decrease for 3 s---yielding mean and median absolute percentage errors of approximately 13% and 12%, respectively. Compared to a reference discharge, the actively controlled shot did not exhibit a significant drop in volume-integrated core radiation, confirming that excessive gas use merely degrades overall plasma performance. However, when contrasted with the exponential increase in core radiation observed in the absence of divertor gas puffing, these results underscore the critical need for real-time optimization. Specifically, divertor gas commands must be actively managed to maintain an $f_{\mathrm{ELM}}$ sufficient for flushing tungsten from the core while maximizing global plasma performance.

Mesh-based multiphysics coupling acceleration for fusion neutronics clustering for fusion blanket applications

Jin Whan Bae, Arpan Sircar, Katarzyna Borowiec, Vittorio Badalassi, Cami Collins

Oak Ridge National Laboratory

Accurate modeling of particle transport within fusion blankets is essential for predicting performance metrics such as heat deposition and the tritium breeding ratio (TBR). However, high-fidelity coupling of thermal fluids from computational fluid dynamics (CFD) to neutronics simulations often incurs significant computational costs due to the complexity of surface intersection calculations in Monte Carlo codes. This paper presents an accelerated multiphysics coupling method for neutronics that utilizes hierarchical agglomerative clustering to map complex material property distributions to a neutronics model. Implemented within the Fusion Reactor Design and Assessment (FREDA) framework, the method leverages existing Python packages to automate the creation of clustered geometries for OpenMC. The approach is demonstrated on a sector model of an ARC-class tokamak with an immersion molten salt blanket, and an simple geometry with varying isotopic concentrations. Results show that the clustering method significantly reduces computational burden without compromising fidelity, providing a foundation for agile iteration of neutronics simulations involving multiple coupled material properties.

Compatibility of Type 304H Stainless Steel in Static Molten FLiBe for Inertial Confinement Fusion Reactors: Role of Impurities and Redox Control

Rishi Pillai, Debashish Sur, Severine Cambier, Adam Willoughby, Tracie Lowe, Youyang Zhao, Amanda Bye, Susana Reyes

Oak Ridge National Laboratory, XCIMER Energy Corporation

Superpermeation and Compression Through Vanadium Foil

Joshua Ruby, Zachary Robinson, W. Udo. Schröder, Matthew Sharpe

University of Rochester

Overview of the European Breeding Blanket programme for Helias 5-B: Dual Coolant Lead-Lithium design, integration and tools

Iole Palermo, Javier Alguacil, Gaetano Bongiovi, Juan Pablo Catalan, Ilenia Catanzaro, Iván Fernández-Berceruelo, Salvatore Giambrone, Guillermo Gómez Fonfría, Jose Ángel Noguerón, Vicente Manuel Queral Mas, et al.

CIEMAT, Universita degli Studi di Palermo, UNED

As part of EUROfusion’s mission to bring stellarators to technological maturity, the Stellarator Power Plant Studies (SPPS) WPPRD began in 2021 to develop a HELIAS-class power plant. Building on DEMO tokamak experience, European teams are designing a Dual Coolant Lead-Lithium (DCLL) breeding blanket (BB) for HELIAS. This concept uses liquid PbLi as breeder/coolant and decoupled helium cooling for the first wall (FW). Two key adaptations address HELIAS’s complex geometry: a detached FW using Capillary Porous System (CPS) technology, and a quasi-toroidal segmentation (QTS) with PbLi flow aligned to magnetic field lines. QTS reduces magnetohydrodynamic (MHD) pressure drop by up to two orders of magnitude, potentially eliminating electrical insulation needs. Remote handling (RH) is rethought for 3D stellarators, where traditional vertical-port extraction is impractical. Alternatives include enlarged fixed coils, movable coils for temporary large ports, and detachable vessel periods. The detached FW strategy shifts maintenance from large BB segments to smaller, easily replaceable FW panels, extending BB lifetime. CPS designs with Li in tungsten matrices were analysed thermally, hydraulically, and neutronically, showing potential to lower displacement-per-atom (dpa) damage while maintaining tritium breeding. Be-based moderators behind the FW CPS matrix improved TBR while reducing back-structure damage. To accelerate design and analysis, HeliasGeom and SHANE tools were developed to rapidly generate realistic 3D parametric geometries for CAD, neutronic, and thermal-hydraulic coupling. Preliminary 3D studies addressed TBR optimisation, shielding, MHD in non-uniform fields (via GridapMHD), and multi-scale thermal–mechanical assessments. These innovations collectively advance stellarator blanket technology, integration, and maintainability toward viable power plant concepts.

Transient behavior analysis of the intermediate-circuit-balanced HCPB fusion power plant

Jan Loskot, Jan Štěpánek, Slavomír Entler, Pavel Zácha

CTU in Prague, Institute of Plasma Physics of the Czech Academy of Sciences

Multiscale assessment of tritium behavior in preliminary fusion pilot plant design using surrogate models in TMAP8

Lin Yang, Pierre-Clément Simon, Emre Yildirim, Jose Manuel Trueba Cutillas, Matthew Robinson, Masashi Shimada

Idaho National Laboratory, Tokamak Energy Ltd

The complexity and significance of multiscale phenomena in fusion energy systems make advanced modeling necessary for designing, optimizing, and safely deploying fusion plants. Tritium accountancy is one of those challenges for deuterium–tritium fusion systems. Its availability is constrained by its short half-life (12.33 years) and limited natural abundance, which require fusion plants to breed tritium onsite. Therefore, accurate tritium accountancy is essential for effective resource management, safety, and economics in fusion plants. Through the U.S. Department of Energy milestone program, Tokamak Energy Ltd. is developing a fusion pilot plant design and evaluating tritium retention and loss in key components and their effect on the fuel cycle. To rapidly explore design trade-offs and quantify design decisions on tritium management, this study presents a multiscale analysis to investigate tritium diffusion, trapping, and recovery in key plasma-facing components. To enhance computational efficiency, we integrate surrogate models at the component-level within a fuel cycle model at the system-level, enabling rapid evaluation of tritium recycling dynamics and inventory under various operational scenarios. The goal of this study is twofold: (1) demonstrate the feasibility of utilizing surrogate models to increase the accuracy of fuel cycle modeling, and (2) rapidly evaluate the performance of fusion technologies to accelerate design iterations. This multiscale model provides the tritium transport and retention behavior and supports the plasma-facing components design optimization in normal and bake-out operations. The work is implemented using the Tritium Migration Analysis Program, Version 8 (TMAP8), an open-source application for tritium transport analysis in fusion systems.

The Helios stellarator fusion power plant: Scoping studies, heating, and fueling

S.T.A. Kumar, C.P.S. Swanson, D.A. Gates

Thea Energy, Inc.

Shielding and tritium breeding performance assessment for magnetic mirror fusion devices: a parametric neutronics study with ParaTAN

Hitarth Shah, Tim Bohm, Ed Marriott, Craig Jacobson, Benjamin Lindley

Computational Fluid Dynamics Analysis of the MELODIE Bubble Column for PbLi Tritium Extraction

Anthony G. Bowers, Thomas F. Fuerst, Subash L. Sharma

Idaho National Laboratory, Missouri University of Science and Technology