Recent Publications

Neutron wall loading in stellarator optimization

Enrique Miralles-Dolz, R. Michael Churchill, Dario Giovanni Panici, Jacob Schwartz, Tim Bohm, Connor Moreno, Paul P H Wilson

Stellarator neutronics is inherently three-dimensional, since non-axisymmetric equilibria produce spatially varying neutron wall loading (NWL). Localized NWL peaks affect first-wall lifetime, shielding requirements, magnet protection, maintenance planning, and ultimately plant availability, but resolving these peaks with high-fidelity Monte Carlo transport remains too expensive for direct use in stellarator optimization. This work integrates a deterministic line-of-sight NWL model into the DESC stellarator optimization package so that NWL can be evaluated as a fast, differentiable engineering metric during stage-I equilibrium optimization. The model treats the deuterium-tritium plasma as a volumetric neutron source, evaluates the Bosch-Hale fusion reactivity from prescribed flux-surface profiles, and maps source contributions to first-wall points through a geometry-dependent kernel. The resulting local NWL map can be used directly in optimization objectives or constraints. The DESC implementation is validated against ParaStell/OpenMC Monte Carlo calculations for circular axisymmetric, ITER-like axisymmetric, and non-axisymmetric configurations; the surface-averaged NWL agrees within about 1.5% across these cases and the deterministic maps reproduce the dominant spatial loading structures while tending to conservatively overestimate the Monte Carlo wall loading. In proof-of-concept optimizations, current-profile variation at fixed plasma boundary reduced peak NWL and the peaking factor by 13.84% and 13.29%, respectively, while quasi-symmetry optimization through plasma boundary shaping reduced peak and mean NWL by 17.22% and 12.97%. These results demonstrate that differentiable NWL objectives and constraints can reveal useful engineering design directions unavailable to conventional plasma physics objectives.

Shutdown dose rate measurements with Ionization Chambers during and at the end of DT operations at JET

Nicola Fonnesu, Stefano Loreti, Rosaria Villari, Davide Flammini, Andrea Colangeli, Fabio Moro, Simone Noce, Alberto Previti, Axel Klix, Xavier L Litaudon

Within the framework of EUROfusion's technological exploitation of deuterium–tritium (DT) operation at JET — initiated under work package JET3 and continued under PrIO — the NEXP sub-project was conceived to exploit the substantial neutron yield expected during the DT campaigns (DTE2 and DTE3) to validate the numerical tools employed for neutron streaming and shutdown dose rate (SDDR) prediction in ITER. This validation, grounded in direct comparison between computational predictions and experimental measurements, constitutes a critical step in demonstrating the reliability of the SDDR methodology that underpins ITER's radiation safety case. As part of this activity, a dedicated dosimetry system based on spherical air-vented ionization chambers was installed in the JET Torus Hall in 2015 and has since undergone successive hardware and software upgrades to address operational challenges identified across DT experimental campaigns. This work traces the evolution of the SDDR dosimetry system and presents the analysis of the measurements acquired during the DT operation of JET, in particular the third DT campaign (DTE3) and, uniquely, throughout the ongoing final shutdown, a phase offering measurement conditions unlikely to be replicated elsewhere. SDDR predictions with the Advanced D1S tool by ENEA are described as well.

Numerical calculations of liquid-metal magnetohydrodynamic flow in inlet manifold: Effects of wall-divided parallel channels on liquid metal flow and pressure in electroconductive inlet manifold

Hiroshige Kumamaru

Compatibility study between CLF-1 steel and HCCB TBM Helium gas medium for engineering qualification

Leran Liu, Guoping Yang, Junshan Wan, Hongbin Liao, Xinghua Wu, Hongxiang Zhang, Zaixin Li, Fengchao Zhao, Qian Sheng, Shuqin Wu, et al.

Preliminary shielding design of the neutron cameras for D-T fusion product diagnostics on the HL-3 tokamak

Y.S. Zhang, Y.P. Zhang, J. Zhang, W.L. Zhong, M. Isobe, K. Ogawa, D. Mazon, Q.L. Yang, Z. Gao, J.M. Gao, et al.

Density, viscosity and conductivity of the B15C5-[EMIm][NTf2]-anisole system

Tianyu Zheng, Chunsen Ye, Zhengyue Wang, Guannan Chen, Yu Qiu, Pengrui Zhang, Wei Sun, Jinhe Sun

Interfacial electric potential profiles of molten fluoride salts in magnetic fields: Insights from molecular dynamics

Hiroki Shishido, Hidetoshi Hashizume

Neutronics Analysis of Shielding Performance for VNS Inboard Toroidal Field Coil with Various Material Options

Jin Hun Park, Pavel Pereslavtsev, Roman Afanasenko, Dieter Leichtle

Impact of ferritic steel blankets on the magnetic field configuration of the helical fusion reactor

Miguel Lindero-Hernández, Luis Alvaro Montoya-Santiyanes, Nagato Yanagi, Frederic Trillaud, Gabriel dos Santos, Diego A. Garfias-Dávalos, Yoshiro Narushima

Migration and release mechanism of hydrogen and helium in Li2O: A first-principles study

Li Yang, Brian D Wirth

Understanding the migration and release of hydrogen (H) and helium (He) in neutron irradiated lithium oxide (Li2O) is critical to develop a sustainable tritium fuel cycle for fusion reactors. In this article, we describe results about the formation, migration, and trapping of H and He with and without intrinsic defects in Li2O based on first principles density functional theory (DFT) calculations. The intrinsic defects include single vacancies, single intrinsic interstitials, and Schottky defects (SDs). We observe that the energetically favorable configurations and concentrations of H-related defects depend on their charge characteristics. Our analysis indicates that the migration and release mechanisms of H isotopes vary with temperatures. Below 1000 K, hydrogen diffusion and release depends on H+ and Li vacancies, while above 1000 K, oxygen defects and large defect clusters control H diffusional release. H trapping at intrinsic defects decreases the diffusivity and the resulting release of H. He atoms prefer octahedral interstitial sites, except near -2 charged oxygen mono-vacancies. He atoms do not alter H occupation preference but weaken the H binding to vacancies. The interaction of helium with oxygen vacancies mainly controls the helium release process.

Progress in reactor-core fusion technologies presented at the 30th IAEA Fusion Energy Conference 2025

Jiming Chen, Jianbao Wang, Qixiang Cao, Shen Qu, Zongyu Yang

This paper provides an overview of the recent progress in reactor-core fusion technologies within the vacuum vessel presented at the 30th International Atomic Energy Agency (IAEA) Fusion Energy Conference held in October 2025 in Chengdu, China, including plasma control, neutronics and nuclear data, tritium technologies, design and development of in-vessel components, related materials and intense neutron sources for material irradiation. Plasma control focusing on achievements for ITER and major fusion research devices are covered and the application of digital twin and Artificial Intelligence are highlighted. Research and Development (R&D) results from the International Thermonuclear Experimental Reactor (ITER) and current devices to future Demonstration Fusion Power Plant (DEMO) reactors are summarized, particularly new findings, data validation, design and analysis tool improvement, properties assessment and technical solutions for critical issues.

Neutron-induced air activation in the ITER HRNS diagnostic enclosure: Quantitative assessment and radiological implications

Anna Wójcik-Gargula, Grzegorz Tracz, Rojin Mehrara, Urszula Wiącek, Giovanni Mariano, Bruno Coriton, Ryszard Kantor, Dariusz Morawski, Marek Scholz

A feasibility study of neutron spectrum reconstruction using synthetic activation data for JT-60SA

Katarzyna Mikszuta-Michalik, Alvaro Cubi, Marco Fabbri, Matteo Di Giacomo

This study presents a methodology for assessing neutronics models of JT-60SA by comparing simulated neutron spectra with spectra reconstructed from neutron activation measurements. The analysis was performed using synthetic data generated with the Monte Carlo N-Particle (MCNP) radiation transport code for an existing model, as the final detailed tokamak model remains under development. Rather than limiting the assessment to a direct comparison with activation measurement, the proposed approach incorporate neutron spectrum reconstruction as a complementary method to evaluate agreement between simulated and actual spectra. The analysis demonstrates the feasibility and potential of the methodology rather than reproducing experimental conditions. Several spectrum unfolding techniques were applied: Tikhonov Regularisation, Minimum Fisher Information, Maximum Entropy, and Maximum Likelihood. Results were additionally combined into an average reconstructed spectrum to reduce method-dependent differences. The MCNP-calculated spectrum for the P10 port was used in FISPACT-II, advanced nuclear simulation software, to simulate foil activation. The reconstructed spectra and FISPACT-II activities were compared against reference MCNP data. Irradiation was assumed to last the entire experimental campaign. Longer irradiation time limits the activation foil set and increases reconstruction uncertainty. Results demonstrate that the high-intensity region of the neutron spectrum can be reconstructed with an uncertainty below 25%. Performing reconstructions separately across distinct energy ranges enables accurate determination of dominant high-intensity peaks despite numerical challenges from large intensity gradients. Shorter irradiation time allows the use of additional dosimetry foils, reducing the overall reconstruction uncertainty to approximately 23% for the full spectrum. Individual unfolding methods reproduce different spectral regions with varying accuracy, whereas averaging results reduces the discrepancy between the reconstructed and reference spectra. The study demonstrates the potential of combining established reconstruction methods for complementary assessment of neutronics simulations and identifies the treatment of large spectral intensity gradients as an important area for further methodological development

Thermodynamic and exergy analysis of a multi-source TES-coupled Rankine cycle for EU DEMO with DCLL blanket

Yuan Sun, Minyang Gui, Xiaodong Liu, ZhaoJun Li, Haibo Jia, Ruifeng Tian, Sen Duan, Sichao Tan

Comparison of the pressure drop and flow characteristics between two designs of a liquid metal blanket supply system

Yuchen Jiang, Yuqiao (Joy) Fan, Sergey Smolentsev

Evaluation of Flux- and Depletion-Based Methodologies for Tritium Breeding Ratio Prediction: Limitations of Current 7 Li Nuclear Data Processing

Cihang Lu, Arantxa Cuadra, David Brown, Gustavo Nobre

Spatially resolved evaluation of primary displacement damage and activation in the CFETR first-wall components

Yingming Sang, Zeenat Ullah, Kuanhao Liu, Shehu Adam Ibrahim, Da Chen

Transient thermal performance of a fusion blanket-Brayton cycle system with heat sink perturbation: A CFD and system code coupled approach

Zai-yong Chen, Guo-liang Xiao, Long Zhang, Sheng-hui Liu, Tian-yang Xing, Hong-yu Li, Xiao-liang Zhu

Uncertainty quantification propagation in FNG HCPB-tritium breeding module using OpenMC-SANDY workflow

Yogendra S. Panchal, G. Ivan Maldonado

BLUEMIRA: a modular, open-source framework for designing tokamak fusion reactors

Matti Coleman, James Cook, Fabrizio Franza, Ivan Maione, Simon Mcintosh, Hudson Baker, Alexander Ian Blair, Shail Desai, Oliver Funk, Georgina Graham, et al.

As efforts across the world to deliver fusion power enter their respective conceptual design stages, many begin to encounter the difficulties of generating complete designs, evaluating them, performing trade-off studies, and comparing different alternatives. Many organisations successfully use fusion reactor systems codes with low-fidelity formulations of the critical physics and engineering aspects to inform the initial design stage and steer them towards a region of the design space they consider attractive, but struggle to explore the design space in more depth. This work is an overview of the open-source tokamak reactor design framework, BLUEMIRA, built from the BLUEPRINT [1, 2] and MIRA [3, 4] codes, which goes beyond the “classical” systems code paradigm and enables the user to parameterise their reactor designs at higher fidelity. Reactor design workflows ranging from 0-D “radial build” design, equilibrium design, to 3-D CAD and automated neutronics analyses can be run within minutes. We present the functionality implemented in the BLUEMIRA code and demonstrate its application to the conceptual design of a conventional aspect ratio fusion reactor, performing an indicative design study over aspect ratio and number of toroidal field coils.