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On-Orbit Measurements of Solar Exclusion Angle for Modular Agile Scalable Optical Terminal (MAScOT) on the ILLUMA-T Mission

The Integrated LCRD Low-Earth Orbit User Modem and Amplifier Terminal (ILLUMA-T) optical communications payload operated on the International Space Station (ISS) for 8 months, concluding in June 2024. ILLUMA-T made the ISS the first space-based user to communicate with NASA’s Laser Communications Relay Demonstration (LCRD). ILLUMA-T was also the first flight demonstration of the Modular, Agile, Scalable Optical Terminal (MAScOT) which will also be used in the Orion Artemis II Optical Communications (O2O) program, where it will provide an optical communications link for the crew aboard the Artemis II mission. Often optical and radio frequency communications systems have outages when they are pointing close to the Sun, where unwanted incident and scattered solar energy significantly reduces or prohibits operations. The MAScOT was designed to reduce the impact of any solar scatter through optical design, material choices, surface treatments and high cleanliness levels. Based on optical scattering models, a solar exclusion angle of 10 degrees was established for ILLUMA-T. This paper presents optical scattering modeling predictions, pre-launch laboratory testing results, and on-orbit measurements of solar scatter at angles ranging from 3 to 25 degrees.

optical communications↗
DOE OSTI2012

Multi-unit Operations in Non-Nuclear Systems: Lessons Learned for Small Modular Reactors

The nuclear-power community has reached the stage of proposing advanced reactor designs to support power generation for decades to come. Small modular reactors (SMRs) are one approach to meet these energy needs. While the power output of individual reactor modules is relatively small, they can be grouped to produce reactor sites with different outputs. Also, they can be designed to generate hydrogen, or to process heat. Many characteristics of SMRs are quite different from those of current plants and may be operated quite differently. One difference is that multiple units may be operated by a single crew (or a single operator) from one control room. The U.S. Nuclear Regulatory Commission (NRC) is examining the human factors engineering (HFE) aspects of SMRs to support licensing reviews. While we reviewed information on SMR designs to obtain information, the designs are not completed and all of the design and operational information is not yet available. Nor is there information on multi-unit operations as envisioned for SMRs available in operating experience. Thus, to gain a better understanding of multi-unit operations we sought the lesson learned from non-nuclear systems that have experience in multi-unit operations, specifically refineries, unmanned aerial vehicles and tele-intensive care units. In this paper we report the lessons learned from these systems and the implications for SMRs.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2012

U.S. Department of Energy Instrumentation and Controls Technology Research for Advanced Small Modular Reactors

Instrumentation, controls, and human-machine interfaces (ICHMI) are essential enabling technologies that strongly influence nuclear power plant performance and operational costs. The U.S. Department of Energy (DOE) has recognized that ICHMI research, development, and demonstration (RD&D) is needed to resolve the technical challenges that may compromise the effective and efficient utilization of modern ICHMI technology and consequently inhibit realization of the benefits offered by expanded utilization of nuclear power. Consequently, key DOE programs have substantial ICHMI RD&D elements to their respective research portfolio. This article describes current ICHMI research to support the development of advanced small modular reactors.

human-machine interface↗
DOE OSTI2018

ABSORPTION CHILLER AND STRATIFIED CHILLED-WATER STORAGE TANK CONFIGURATIONS FOR COUPLING TO A SMALL MODULAR REACTOR

Power maneuvers stemming from time-varying loads imposed on nuclear reactors from diurnal changes in demand and renewable intermittency can be detrimental to the life of the reactor. Temperature swings during power maneuvers result in thermal and mechanical stresses in fuel elements and other reactor components. Thermal Energy Storage (TES) reservoirs can be coupled to reactors to absorb these grid instabilities. Previous work has shown chilled-water storage can help shift cooling loads that contribute to the daily peak electric demand from on-peak to off-peak hours. The objective of this work is to evaluate a stratified chilled-water storage tank as a potential TES reservoir for a Small Modular Reactor (SMR) using absorption chillers for chilled-water production. Simulation results reveal absorption chiller performance is hindered when receiving steam from a tap on the low-pressure turbine. A better configuration involves integrating the absorption chillers into a flash vessel system that is thermally coupled to a sensible heat storage system. The sensible heat storage system maintains reactor thermal output at 100% and matches turbine output with demand while producing enough steam to power four large absorption chillers to charge a stratified chilled-water storage tank, which is used to offset cooling loads in an adjacent facility.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2017

Design of a Sensible Heat Peaking Unit for Small Modular Reactors

Thermal Energy Storage (TES) has been proposed as a load management strategy for Small Modular Reactors (SMRs) deployed on constrained grids and/or hybrid energy systems [1] The three main types of thermal energy storage are sensible heat storage, latent heat storage, and thermochemical storage. Sensible heat storage is the most commercially mature technology [2]. In sensible heat storage, there are two modes of operation: charging and discharging. For a two tank, sensible heat TES System, charging involves taking cold TES fluid from a cold tank, heating it and storing it in a hot tank for later use. Discharge involves taking the hot TES fluid from the hot tank, making use of the heat in some manner, and returning the TES fluid back to the cold tank. The theory, control strategies, and results for operating a two-tank sensible heat storage system in charging mode has been reported previously [3]. In this paper, we examine operation of the TES system in discharge mode as a peaking unit.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2018

Periodic Material-Based Seismic Base Isolators for Small Modular Reactors

Important structures such as nuclear power plants should experience very little vibrations in order to maintain the safety of the nuclear facilities during seismic events. Protection of these structures by seismic isolators requires the isolators to provide seismic isolation irrespective of the direction of excitations and to develop a stable response without rocking. Conventional seismic isolation systems, however, can only fulfill partial requirements for the seismic protection. This study adopts the principle of periodic materials for seismic isolation. These materials exhibit unique properties of frequency band gaps, where incoming waves with frequencies falling inside the frequency band gaps are forbidden. The new isolation systems, known as periodic foundations, function both as a structural foundation to support the gravitational weight of the superstructure and also as a seismic isolator. The isolation mechanism, hypothetically, can easily fulfill all the requirements for seismic protection of the critical facilities. This study focuses on the design of one-dimensional (1D) and three-dimensional (3D) periodic foundations for seismic isolation of small modular reactor (SMR) buildings. The theoretical study was first conducted to reveal the fundamental behavior of periodic foundations. Then global sensitivity analysis was utilized to study the effect of design parameters on the frequency band gaps. In addition, simple straight-forward design equations based on the sensitivity analysis are proposed for the design of periodic foundations. Utilizing the proposed equations, prototypes of 1D and 3D periodic foundations were designed to isolate an SMR building. Scaled models were fabricated and experimentally tested to validate the hypothesis and design. The periodic foundation structural systems were tested under various input waves, including seismic waves, in the horizontal and vertical directions and the torsional mode. The shake table test results show that the periodic foundations can reduce the acceleration response of the SMR building up to 90% in the horizontal direction and the torsional mode. As much as a 40% response reduction in the vertical direction is also observed. Moreover, the periodic foundation-isolated structure exhibited stable response with negligible rocking on the structure. This study proved the capability of periodic foundations to enhance the seismic safety of critical structures.

42 ENGINEERING↗
DOE OSTI2021

The Fast Modular Reactor (FMR) Pre-Application Regulatory Engagement Plan

The Fast Modular Reactor (FMR) is a 50 MWe Gascooled Fast Reactor (GFR) being developed by General Atomics Electromagnetic Systems (GA-EMS) under U.S. Department of Energy’s (DOE’s) Advanced Reactor Demonstration Program (ARDP), specifically Advanced Reactor Concepts 2020 (ARC-20). The 3-year conceptual design of the FMR is being conducted with verifications of key metrics in fuel, safety, and operational performance. GAEMS is pursuing design, licensing, and commercialization of the proposed reactor, with demonstration by 2030 and deployment by the mid-2030s. The U.S. Nuclear Regulatory Commission (NRC) recommends the pre-application regulatory engagement to provide for early identification of regulatory requirements for advanced reactors and to provide all interested parties with a timely, independent assessment of the safety and security characteristics of advanced reactor designs. As such, GAEMS is developing a pre-application regulatory engagement plan (REP) of the FMR.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2022

Multiscale Experiments and Multiphysics Simulation of Multiphase Flow for Transportable Small Modular Reactors

A new type of safe, small, transportable nuclear reactor would address the intense and ever-growing global demand for energy produced via a resilient, carbon-free energy source. In this regard, transportable small modular reactors (SMRs) are being designed and developed for electricity generation within small/micro-grid/off-grid isolated systems, as well as for heat generation in industrial/residential applications. These reactors feature the capability to be fully factory fabricated and then directly transported to utilities’ sites as “plug-and-play” systems. Research and development (R&D) programs are underway at Idaho National Laboratory (INL) to successfully design, develop, and demonstrate such safe-by-design mobile reactor technologies, in collaboration with partner organizations. Multiscale experimental facilities and multiphysics simulation tools are required for reactor design verification and validation (V&V), and licensing. These advanced reactors are intended to feature passive safety systems such as passive containment cooling systems (PCCS), which consist of multiphase flows and multispecies distributions. This seminar talk will focus on designing and analyzing transportable SMR PCCS by using multiscale experiments and multiphysics computational fluid dynamics (CFD) simulations to support reactor licensing and safety. The corresponding research challenges are addressed via supportive verification and validation results generated by the models and simulation tools in combination with selective parametric and uncertainty analysis. This solution approach could blaze the trail for commercial adoption of such technologies. The facilities, simulation capabilities, and research opportunities available at INL in regard to such reactors and the integrated energy systems with which they go hand in hand are also discussed briefly, and may spark interest in deeper research as well as new collaborative projects.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2022

A Simple Program to Estimate the Fast Modular Reactor Steady-State Closed Brayton Cycle Operating Parameters

The Fast Modular Reactor (FMR) is a gas-cooled fast reactor (GFR) that produces a net electricity output of 50 MW with helium-driven closed Brayton cycle. The power plant includes reactor system and power conversion unit (PCU). The reactor system produces fission energy that is transferred by helium flow. The PCU consists of a turbine, two compressors, and three heat exchanges. More specifically, the recuperator is a counter-flow energy recovery heat exchanger. The precooler and intercooler are the heat sinks. To analyze and understand the sensitivity of plant performance to the design parameters, a numerical program was written to calculate the plant operating parameters represented by the helium temperature, pressure, mass flow, and the heat sink temperatures. The program was developed for the steady-state operating condition. etc.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2022

MELCOR Model Development of the General Atomics Fast Modular Reactor

General Atomics Electromagnetic Systems (GA-EMS) is currently developing a fast modular reactor (FMR) capable of providing safe, carbon-free electricity by 2035. As part of the development process, researchers at the University of Wisconsin-Madison (UWM) use MELCOR 2.2 to develop a simulation model of the proposed design to perform accident analyses. This paper summarizes the efforts of researchers at UWM in the creation of the FMR model. This model was built based on initial FMR design parameters. The design parameters will change as the design evolves and is refined.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2018

POST-IRRADIATION EXAMINATION AND SAFETY TESTING OF AGR-2 PEBBLE BED MODULAR REACTOR FUEL AT OAK RIDGE NATIONAL LABORATORY

A cooperative research and development agreement (CRADA) has been established between Pebble Bed Modular Reactor (PBMR) State Owned Company (SOC) Ltd. of the Republic of South Africa and Battelle Energy Alliance, LLC (BEA), the managing and operating contractor of Idaho National Laboratory (INL). The objective of this agreement is to conduct safety tests and destructive examination on compacts containing tristructural isotropic (TRISO) coated particle fuel that was provided by Necsa (for PBMR and title transferred to the Department of Energy [DOE]) and irradiated in the Advanced Test Reactor (ATR) in Capsule 4 as part of the Advanced Gas Reactor (AGR)-2 experiment performed under a previous CRADA (08-CR-12). The proposed safety testing and post-test examination will assist with assessing fuel performance during high-temperature reactor accident conditions. Due to different capabilities, some work will be performed by DOE’s Oak Ridge National Laboratory (ORNL) under a separate agreement. This statement of work describes the work scope to be performed by ORNL in support of the CRADA. Based on consultation with PBMR and ORNL, INL may modify the scope of work to be performed at ORNL. In particular, data from initial tests and examinations may result in scope modification as necessary.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2012

Preliminary LOCA analysis of the westinghouse small modular reactor using the WCOBRA/TRAC-TF2 thermal-hydraulics code

The Westinghouse Small Modular Reactor (SMR) is an 800 MWt (> 225 MWe) integral pressurized water reactor (iPWR) with all primary components, including the steam generator and the pressurizer located inside the reactor vessel. The reactor core is based on a partial-height 17x17 fuel assembly design used in the AP1000{sup R} reactor core. The Westinghouse SMR utilizes passive safety systems and proven components from the AP1000 plant design with a compact containment that houses the integral reactor vessel and the passive safety systems. A preliminary loss of coolant accident (LOCA) analysis of the Westinghouse SMR has been performed using the WCOBRA/TRAC-TF2 code, simulating a transient caused by a double ended guillotine (DEG) break in the direct vessel injection (DVI) line. WCOBRA/TRAC-TF2 is a new generation Westinghouse LOCA thermal-hydraulics code evolving from the US NRC licensed WCOBRA/TRAC code. It is designed to simulate PWR LOCA events from the smallest break size to the largest break size (DEG cold leg). A significant number of fluid dynamics models and heat transfer models were developed or improved in WCOBRA/TRAC-TF2. A large number of separate effects and integral effects tests were performed for a rigorous code assessment and validation. WCOBRA/TRAC-TF2 was introduced into the Westinghouse SMR design phase to assist a quick and robust passive cooling system design and to identify thermal-hydraulic phenomena for the development of the SMR Phenomena Identification Ranking Table (PIRT). The LOCA analysis of the Westinghouse SMR demonstrates that the DEG DVI break LOCA is mitigated by the injection and venting from the Westinghouse SMR passive safety systems without core heat up, achieving long term core cooling. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2019

Small Modular Reactors in Canada: Planning for Waste from the Outset - 19254

Canada is exploring the potential for on- and off-grid applications for small modular reactors (SMRs). SMRs are at an early stage of development and a road-mapping process was launched in Canada in February 2018 to better understand the views on priorities and challenges related to the possible development and deployment of SMRs. In addition to engaging partners, stakeholders and Indigenous representatives through workshops, a number of working groups were formed to advise the Road-map Secretariat on topics such as understanding the value proposition of different SMR technologies, matters associated with regulatory readiness, and issues related to waste management and transportation. The Waste Working Group (Waste WG) brought together experts from current nuclear waste generators, the organization responsible for managing Canada's nuclear fuel waste, government, and the regulator to identify waste disposal and storage considerations for Canadian SMR applications, including an analysis of waste streams, waste transportation, short and long-term disposal and storage requirements, and decommissioning considerations. Radioactive waste has been safely managed within a regulatory framework in Canada for decades. Technologies for waste storage and transport exist and also have been in use for decades, and therefore provide a technical basis to explore any specific differences that would apply to waste streams resulting from the construction, operation and decommissioning of SMRs. The Waste WG concluded that a disposal path for SMR used fuel exists through the Nuclear Waste Management Organisation's (NWMO) Adaptive Phased Management (APM) approach, but that R and D work is needed to demonstrate that SMR waste can meet the acceptance criteria. The Waste WG noted that although projects are progressing to realize disposal facilities for the two largest producers of low and intermediate level waste, small producers including potential SMR operators currently have no defined path to disposal for low and intermediate level waste. The Waste WG also highlighted that there could be potential logistical challenges with the transportation of irradiated reactor cores, in particular for remote locations, which will need to be explored. The Waste WG recognized that some uncertainties remain, and early and open communication and coordination between the SMR developers and the NWMO, and potential waste receivers will be key to ensuring a robust framework for SMR waste management from the outset in Canada. This paper explores the results of the analysis and the key findings, high-level recommendations and actions of the Waste WG. It presents the results of the Waste WG's analysis of waste categories against Canadian SMR technologies that best align to end-user requirements; identification of key gaps in research and development for waste categories; and identification of potential work that could address the key gaps. The Waste WG undertook its work between February and August 2018. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Development of thermal transit flow measurement for small modular reactors - 140

Safe, reliable, and efficient operation of nuclear reactors requires timely and accurate measurement of primary coolant parameters such as temperature, flow, pressure, and level. These measurements may be challenging in small modular reactors (SMRs) with integral vessel design. For SMRs with the integral design, sensors may be located in confined spaces or embedded within pressure vessels. The absence of primary coolant loops is another fundamental design attribute that will affect the location of sensors, sensor interfaces, and types of sensors suited for process parameter measurements. Further, the number and location of pressure vessel penetrations may be constrained compared to traditional nuclear power plants (NPPs). As a result, conventional NPP temperature, flow, pressure, and level sensors may not be appropriate for use in SMRs. This paper addresses the development of new sensor technology for hybrid temperature, flow, and level measurement. The authors demonstrate the alternative use of resistance temperature detectors (RTDs) where cross-correlation of process temperature variations between RTDs is used to calculate process flow velocity. The new sensor and measurement technology will also incorporate RTD response time and self-heating characteristics to provide flow and level measurement in accident conditions. This capability would simplify reactor design and enable optimal placement of reactor pressure vessel penetrations leading to increased operational reliability and safety. The cross-correlation of temperature signals and adaptation for flow measurement in a laboratory setting is presented here. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2017

Simulation and control of a passively cooled small modular reactor Samet - 142

This work regulates a small modular reactor (SMR) with traditional control methodologies and analyzes its response to typical disturbances. An analytical model for the passively cooled NuScale SMR is developed to represent the essential dynamics. The MATLAB/Simulink based model consists of reactor core, steam generator, pressurizer, hot leg riser and downcomer, and turbine representations. The point kinetics equations with a single combined neutron precursor group and the lumped parameter representations with single-phase natural circulation account for the neutronics and thermohydraulics in the reactor core. A lumped parameter, moving-boundary approach forms the basis of the nonlinear model adopted for the once-through helical-coil heat exchangers in which boundaries between regions of different fluid states (i.e., subcooled, boiling, and superheated) vary over time. A proportional-integral-derivative controller employing a sliding-average temperature strategy commonly used for pressurized water reactors is implemented. The responses of the SMR to two different disturbances are analyzed and discussed in detail. For the first scenario, a 5% step increase in the load is applied to the system, which results in a change in the steam valve opening. For comparison, two different simulations under this same disturbance are run: one including and one excluding the control systems. The second scenario tests the effectiveness of the control system to increase (or decrease) the reactor thermal power to a certain level within a desired time period. The simulation results show that important system variables are kept at the desired values by the proposed control strategy. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2017

Control strategies for coupling thermal energy storage systems with small modular reactors - 188

The contribution of intermittent (renewable) energy sources such as wind and solar continues to increase as renewables improve in both efficiency and price-point. However, the variability of renewables generates additional challenges for the electric grid in the form of rapidly varying electric loads. Proposed options for accommodating this load have included operating nuclear reactors in a load follow mode, or operating the reactor at or near steady state and bypassing steam directly to the condenser. Both of these strategies result in lost energy potential. In addition to lost energy potential, load follow operation can result in increased stress on the fuel and other mechanical components. A more attractive approach is to operate the reactor at or near steady state and bypass excess steam to a thermal energy storage system. The thermal energy can then be recovered, either for electric generation during periods of peak electric demand, or for use in ancillary applications such as desalination and hydrogen production. Sensible Heat Thermal Energy Storage is a mature technology currently used in solar energy systems. This research focuses on the design and coupling of such a system to Small Modular Reactors (SMRs), typical of Integral Pressurized Water Reactor (IPWR) designs currently under development. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2017

Emerging and existing sensing technologies for small modular reactors and advanced reactors - 191

The development of small modular reactors (SMRs) and Generation-IV advanced reactor designs represents a promising future for nuclear energy. These next-generation reactors can support new applications for nuclear energy like hydrogen production, industrial heat generation, and water desalination in addition to electricity generation. Furthermore, SMRs and advanced reactors enable load-following operations, offer improved passive safety features, support lengthened refueling cycles, and provide spent fuel management capabilities. To date, there are no SMRs operating or under construction in the United States, but commercial operation of the first integral Pressurized Water Reactor (iPWR) SMR is expected by the mid-2020's with Generation-IV advanced reactors to follow a decade or two later. To facilitate the development and deployment of SMRs and advanced reactors, key instrumentation and control (I and C) system challenges must be addressed and existing nuclear grade I and C sensors will need to be adapted or new sensors developed. For example, traditional measurement techniques and maintenance strategies used in the current generation of light water reactors (LWRs) will be challenged by the inherent design characteristics of the iPWR. For Generation-IV reactors, conventional I and C sensors will not withstand prolonged exposure to the harsh environmental conditions of advanced reactors (e.g. elevated temperatures, corrosive coolants, increased radiation). This paper discusses the challenges associated with making primary system process measurements in next-generation reactors and includes a summary of work performed to evaluate existing and emerging sensor technologies for these systems. As importantly, the paper presents the initial test results of a prototype temperature sensor developed by Analysis and Measurement Services Corporation (AMS) for use in SMRs and advanced reactors. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗