Building a Body of Knowledge to Inform a Technology-Agnostic Iterative Safety Assessment Methodology for Fusion Facilities

Recent years have seen the achievement of important milestones in the harnessing of fusion energy for potential commercial applications. However, even ambitious timelines place the commissioning of a commercial pilot plant at least a decade away. The path to commercialization will involve the development of a commercially viable design, featuring a robust safety and reliability case that (1) comprehensively characterizes system safety, (2) facilitates regulator interactions via industry standard analytical methods, and (3) can build confidence with potential stakeholders. This path benefits from fusion not being burdened with some of the hazards associated with fission (e.g. criticality, decay heat), and therefore lends itself to a “clean slate” approach to design and safety assessment. The Electric Power Research Institute (EPRI) and Vanderbilt University (VU) have demonstrated a technology-neutral safety-in-design (SiD) methodology that incorporates risk and reliability considerations into each stage of the design, thereby incrementally building the safety and reliability case for a technology. The SiD methodology was originally developed for assessing early-stage advanced fission reactors, addressing challenges associated with limited operational experience, unfamiliar systems, and unique radiological, chemical, and other industrial hazards, thus supporting a technology-agnostic, flexible approach. The SiD methodology leverages established qualitative and semi-quantitative process hazard assessment methods, offering a practical means for developing the building blocks for quantitative risk assessment (if needed), and supports efficient early engagement with regulators. EPRI and VU, with fusion community members, utilities, and regulators, are evaluating the application of the SiD methodology to fusion technology. This paper presents an initial outline of a body of knowledge (BoK) that identifies and categorizes papers, reports, and technical standards reflective of academic and industry efforts in topical areas related to fusion safety and reliability. BoK development is a common approach to capture and describe the state of the art in a technical domain; for example, the BoK process has been used to perform the initial organization of the state of the art in areas such as systems engineering, environmental engineering, and project management. Here, BoK development is intended to provide the fusion community with access to a compendium of technical information to draw on during design, safety analysis, and early engagement with regulators and stakeholders. To date, more than 100 documents have been identified to form the BoK for the SiD application to commercial fusion plants. We have presently organized this documentation into seven topical areas: (1) a description of fusion technologies, (2) previous fusion safety analyses, (3) reliability studies, (4) safety analysis insights from nonfusion facilities, (5) fusion regulation and relevant technical guidance, (6) safety, environment, fuel cycle, and decommissioning studies, and (7) commissioning and operation studies. Preliminary engagement with the fusion community indicates that the SiD approach can inform and support fusion technology developers seeking to mature commercially relevant designs and build robust safety and reliability cases for technologies in an environment characterized by evolving regulatory regimes and limited operational experience.

Design and Engineering of LUPIN: A Test-Bed Radio-Frequency Ion Source for Enhanced Neutral Beam Injection on DIII-D

The Large, Uniform Plasma for Ionizing Neutrals (LUPIN) is a radio-frequency (RF) inductively coupled plasma (ICP) chamber for demonstrating plasma performance of an RF ICP positive ion source upgrade for the DIII-D neutral beam injection (NBI) system. LUPIN will be used to investigate ion source physics, including neutral gas dynamics, plasma density uniformity, interactions with Faraday shields, and power coupling to novel RF antenna designs. LUPIN has an RF generator capable of delivering 20 kW of power at 2 MHz, which is coupled into a cylindrical quartz vessel measuring 20 cm in length and 10 cm in radius. This configuration matches the power density requirements for a full-scale ion source. Target hydrogen and deuterium plasma densities exceeding 10 18 m -3 would relate to extracted ion current densities of 2100 A/m 2 for 10s. Vacuum conductance and gas flow calculations predict a maximum achievable neutral gas flow rate of 1675 Pa $ $ ⋅  L/s at 5 Pa of He, which mimics the gas flow of the DIII-D NBI system. Designs have been developed for an internal Faraday shield to mitigate heat flux and ion sputtering on the dielectric vessel. Thermomechanical finite element simulations demonstrated the Faraday shield design to be capable of withstanding anticipated heat loads from worst-case operation scenarios. Results of upcoming experimental investigations on LUPIN will guide the design of a full-scale prototype for DIII-D integration.

Design and Study of Inductively Coupled Plasma Chamber Components Using the SupRISE Test Device at DIII-D

The DIII-D National Fusion Facility aims to increase the auxiliary heating power for the tokamak by upgrading the neutral beam injection (NBI) system. In collaboration with North Carolina State University, the conventional arc-and-filament NBI ion sources will be converted to inductively coupled plasma (ICP) sources that utilize radiofrequency (RF) coupling to maximize reliability for high-power operation. In support of this initiative, a full-scale test device, Superior Radiofrequency Ion Source Experiment (SupRISE,) is currently under construction at the DIII-D facility. In preparation for the construction of a full-scale prototype that can be installed on the DIII-D NBI system, experiments on SupRISE have been conducted to determine the optimal RF frequency for high-power coupling, the Faraday shield slit configuration, and the ICP chamber length. SupRISE is comprised of an approximately 30 × 70 cm quartz dielectric vessel with an internal Faraday shield enclosed in a secondary vacuum chamber to ensure structural stability of the dielectric. Actively cooled front and back plates are designed to reduce the thermal stresses on the plasma-facing components and mate with the existing accelerator used by the NBI system at DIII-D. A total of 50 kW of RF power will be coupled to the plasma through the quartz over a variable frequency range of 4 to 8 MHz to sustain a plasma density of ~10 18  m$^{ - 3}$   − 3for a 10-s ON, 210-s OFF duty cycle. Various modeling efforts have been employed to simulate the thermal and stress profiles over the primary components of the SupRISE device, as well as the inductance behavior of the RF antenna. These simulation results and the final design for SupRISE are presented. An additional reduced-scale predecessor ICP source (called RISE) has been used to develop a predictive match model that will be applied to frequency optimization studies on SupRISE. The outcomes of this research and complementary efforts at North Carolina State University are essential for the incorporation of ICP NBI positive ion sources at the DIII-D facility.

Century: Zap Energy’s 100-kW-Scale Repetitive Sheared-Flow-Stabilized Z -Pinch System with Liquid Metal Cooling

Zap Energy is developing the sheared-flow-stabilized (SFS) Z-pinch concept for commercial applications. The SFS Z-pinch relies on plasma self-organization, in the sense that plasma dynamics play a critical role in confinement. Using plasma axial current for confinement and compression eliminates the need for external confinement or heating technologies. This compact magnetic confinement technology could, in turn, provide the basis for a cost-effective deuterium-tritium fusion power plant. In addition to a robust experimental program pushing plasma performance toward breakeven conditions, Zap Energy has parallel programs developing power handling systems suitable for future power plants. Technologies under development include high average power repetitive pulsed power, high duty cycle cathodes, and liquid metal wall systems. Century is the name of Zap Energy’s first effort to integrate these three components into an operational system capable of firing nonreacting hydrogen SFS Z-pinch plasmas into a liquid metal–lined container at sustained repetition rates on the order of 0.1 Hz. The pulsed power driver and liquid metal heat exchanger are both designed to sustain input powers of 100 kW. Construction and initial operations with an interim ~10-kW liquid metal heat exchanger are described.

High-Fidelity CFD Modeling of Cryogenic Hydrogen Isotope Extrusion for Fusion Reactor Pellet Fueling

This study investigates the extrusion processes of deuterium and protium using ANSYS-Polyflow. The geometries and computational fluid dynamics (CFD) settings closely replicate the experimental setups and data acquired from the extruder experiments at Oak Ridge National Laboratory (ORNL) for validation purposes. We explore the impacts of (1) slip versus non-slip boundary conditions and (2) the use of constant, temperature-, and shear rate–dependent viscosities, concluding that the implementation of non-slip wall boundary conditions combined with shear rate–dependent viscosity produced more accurate predictions. The simulations achieved excellent agreement with the experimental data, with relative differences of only 5% for deuterium, and 3% to 6% for protium. This is the first time that experimental extrusion data at ORNL have been accurately predicted through high-fidelity CFD modeling. The advancements offer valuable insights and a foundational modeling tool for optimizing pellet injectors for ITER and other future reactor-scale devices.

Sports dental trauma for children and adolescents: unique considerations

Sports play an important and positive role in the lives of millions of children and adolescents worldwide. The risk of injuryin this case, dental injuries, is an ever-present danger to the participants, particularly those we who choose contact sports. Children and adolescents are unique athletes as they are continually growing and developing, and the treatment of traumatic dental injuries must be specific for the age of the individual player. Preventive rules and equipment, especially athletic mouthguards must be tailored to the special needs of a particular athlete in a particular sport at a particular age.

Guide my feet: The Civil Rights Movement as a pedagogical practice of enskilment

This paper draws on Tim Ingold’s anthropological theory of enskilment to build an applied theoretical framework for pedagogical praxis. This frame is then applied in a learning analysis of the Civil Rights Movement and a critical exploration of contemporary teaching approaches in an under-resourced public school in the Midwest.

Searching for Psychoanalytic Ancestors and Other Excursions in Bibliophilia

Building capacity to address equity in sexual wellbeing among transgender and gender expansive communities in Philadelphia, United States

Transgender and/or gender expansive (TGE) individuals in the United States (US) face barriers to sexual wellbeing. TGE communities have largely been excluded from sex education programs, putting the onus of programming on community agencies and healthcare providers. Acceptable TGE-tailored educational programming for sexual wellbeing has been understudied. Sexual health experts have recently outlined a framework for supporting sexual wellness via comprehensive public health education, recommending attention to the intersecting pillars of sexual health, sexual pleasure, sexual wellbeing, and sexual justice. Guided by this framework, the objective of our study was to ascertain sexual wellbeing program needs among TGE communities. As part of a community-engaged research study, we conducted qualitative interviews ( n  = 29) with TGE individuals (age range: 21-55; 62.1% people of color) residing in Philadelphia to understand sexual wellbeing programmatic needs and preferences. Participants were presented with 11 topics based on the pillars of sexual wellness, and asked to expand upon the three they believed deserve prioritization. Our team performed a thematic analysis on all interviews. Participants’ most highly ranked topics were consent, boundaries, safety, security, and agency in interpersonal dynamics, trauma-informed and sex-positive sexual wellbeing approaches, and shame, self-esteem and acceptance of gender and sexual identity. Participants identified several intervention strategies for addressing these topics, including in-person, trans-led didactic sessions (e.g. workshops and classes for TGE people) to discuss effective sexual health communication with partners. Participants thought that sexual wellness interventions should be implemented in community-based settings as well as in centralized online resources. Our study provides insights for leveraging community priorities into community- and clinic-based programming to support equity in sexual wellbeing for TGE individuals. By incorporating education around safety and trauma-informed approaches, providers may facilitate sexual wellbeing among TGE individuals. Future studies should develop TGE-tailored sexual wellbeing interventions and evaluate their impact on sexual wellbeing indicators.

Local food systems and community economic development edited by R. David Lamie and Steven C. Deller, London, Routledge, 2021, 116 pp., £41.00 (paperback), ISBN 978-1-03-208184-7 (paperback)