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DOE OSTI2021

Operating a commercial building HVAC load as a virtual battery through airflow control

Virtual battery (VB) is an innovative method to model flexibility of building loads and effectively coordinate them with other resources at a system level. Unlike a real battery with a dedicated power conversion system for charging control, methods are required for operating building loads to deviate from the baseline to respond to grid signals. This paper presents a VB control for a commercial heating, ventilation, and air conditioning (HVAC) system to follow the desired power consumption in real-time by adjusting zonal airflow rates. The proposed method consists of two parts. At the system level, a mixed feedforward and feedback control is used to estimate the desired total airflow rate. At the zone level, two priority-based algorithms are then proposed to distribute the total airflow rate to individual zones. In particular, a zonal airflow limit estimation method is proposed using machine-learning techniques, in contrast to physics-based thermal models in existing studies, to more accurately capture zonal thermal dynamics and improve temperature control performance. An office building on the Pacific Northwest National Laboratory campus is implemented in EnergyPlus, and used to illustrate and validate the proposed control.

Wang, Jiyu↗

DOE OSTI2013

3-Port Single-Stage PV & Battery Converter Improves Efficiency and Cost in Combined PV/Battery Systems

Due to impressive cost reductions in recent years, photovoltaic (PV) generation is now able to produce electricity at highly competitive prices, but PV’s inherent intermittency reduces the potential value of this energy. The integration of battery storage with PV will be transformational by increasing the value of solar. Utility scale systems will benefit by firming intermittency including PV ramp smoothing, grid support and load shifting, allowing PV to compete directly with conventional generation. For distributed grid-tied PV adding storage will reduce peak demand utility charges, as well as providing backup power during power grid failures. The largest long term impact of combined PV and battery systems may be for delivering reliable off-grid power to the billions of individuals globally without access to conventional power grids, or for billions more that suffer from daily power outages. PV module costs no longer dominate installed PV system costs. Balance-of-System (BOS) costs including the PV inverter and installation now contribute the majority of installed system costs. Battery costs are also dropping faster than installation and battery power converter systems. In each of these separate systems power converters have become a bottleneck for efficiency, cost and reliability. These bottlenecks are compounded in hybrid power conversion systems that combine separate PV and battery converters. Hybrid power conversion systems have required multiple power converters hardware units and multiple power conversion steps adding to efficiency losses, product and installation costs, and reliability issues. Ideal Power Converters has developed and patented a completely new theory of operation for electronic power converters using its indirect EnergyPacket Switching™ topology. It has established successful power converter products for both PV and battery systems, and its 3-Port Hybrid Converter is the first product to exploit the topology’s capability for the industry’s first single-stage multi-port hybrid power converter. This unique low cost approach eliminates the hybrid power conversion bottlenecks when integrating batteries into PV systems. As result this product will significantly accelerate market adoption of these systems.

14 SOLAR ENERGY↗

DOE OSTI2018

Assessment of the National Solar Radiation Database (NSRDB 1998-2016)

Applying traceable and standardized uncertainty characterization for solar resource data provides confidence in the dataset for use by financiers, developers and site operators of solar energy conversion systems, and ultimately reduces deployment cost. Performance guarantees of solar energy conversion systems are based on the available solar resource from measurement stations or modeled dataset such as the National Solar Radiation Database (NSRDB). In this study we implemented a comprehensive uncertainty determination approach [1]. The study also analyzed how the NSRDB (19982016) - Version 3 compares with the previous NSRDB (19982015) - Version 2. The study also attempted to estimate the uncertainty differences derived by comparing theNSRDB data to the seven measurement stations from the National Oceanic and Atmospheric Administration's Surface Radiation Budget Network (SURFRAD) and University of Oregon Solar Radiation Monitoring Laboratory (SRML). The evaluation was conducted for hourly values, daily totals, monthly mean daily totals, and annual mean monthly mean daily totals and demonstrate the qualityof the new datasets currently available from the NSRDB.

14 SOLAR ENERGY↗

DOE OSTI2019

2018 Energy Storage Pricing Survey

Since grid energy storage is still a nascent industry, it is often difficult to obtain capital costs for various energy storage technologies. This type of information is required to perform an initial cost-benefit analysis related to a potential energy storage deployment, as well as to compare different energy storage technology options. The goal of this report is to summarize energy storage capital costs that were obtained from industry pricing surveys. The methodology breaks down the cost of an energy storage system into the following categories: the storage module; the balance of system; the power conversion system; the energy management system; and the engineering, procurement, and construction costs. Pricing data is presented for the following technologies: pumped hydro storage; compressed air energy storage; sodium battery storage; zinc battery storage; long duration flywheels; short duration flywheels; vanadium flow batteries; zinc bromide flow batteries; iron flow batteries; nickel batteries; lithium ion energy batteries; lithium ion power batteries; lead acid batteries; and advanced lead carbon batteries.

25 ENERGY STORAGE↗

DOE OSTI2021

2019 Energy Storage Pricing Survey

Since grid energy storage is still evolving rapidly, it is often difficult to obtain project specific capital costs for various energy storage technologies. This information is necessary to evaluate the profitability of the facility, as well as comparing different energy storage technology options. The goal of this report is to summarize energy storage capital costs that were obtained from industry pricing surveys. The methodology breaks down the cost of an energy storage system into the following component categories: the storage module; the balance of system; the power conversion system; the energy management system; and the engineering, procurement, and construction costs. By evaluating each of the different component costs separately, a synthetic system cost can be developed that provides internal pricing consistency between different project sizes using the same technology, as well as between different technologies that utilize similar components.

25 ENERGY STORAGE↗

DOE OSTI2021

2020 Energy Storage Pricing Survey

The annual Energy Storage Pricing Survey (ESPS) series is designed to provide a standardized reference system price for various energy storage technologies across a range of different power and energy ratings. This is an essential first step in comparing systems of the different technologies’ usage costs and total cost of ownership. The final system prices are developed based on data from an extensive set of interviews with representatives across the manufacturing and project development value chain, plus available published data. This information is incorporated into a consistent methodology structure that will allow pricing information to be incorporated at whatever level it was obtained, ranging from component to fully installed system. The ESPS system pricing methodology breaks down the cost of an energy storage system into the following component categories: the storage module; the balance of system; the power conversion system; the energy management system; and the engineering, procurement, and construction costs. By evaluating each of the different component costs separately, a more accurate system cost can be developed that provides internal pricing consistency between different project sizes using the same technology, as well as between different technologies that utilize similar components.

25 ENERGY STORAGE↗

DOE OSTI2018

Assessment of the National Solar Radiation Database (NSRDB 1998-2016): Preprint

Applying traceable and standardized uncertainty characterization for solar resource data provides confidence in the data set for use by financiers, developers, and site operators of solar energy conversion systems, and ultimately this reduces deployment cost. Performance guarantees of solar energy conversion systems are based on the available solar resource from measurement stations or modeled data sets, such as the National Solar Radiation Database (NSRDB). In this study, we implemented a comprehensive uncertainty determination approach (1). The study also analyzed how the NSRDB (1998-2016): Version 3 compares with the previous NSRDB (1998-2015): Version 2. The study also attempted to estimate the uncertainty differences derived by comparing the NSRDB data to the seven measurement stations from the National Oceanic and Atmospheric Administration's Surface Radiation Budget Network (SURFRAD) and University of Oregon Solar Radiation Monitoring Laboratory (SRML). The evaluation was conducted for hourly values, daily totals, monthly mean daily totals, and annual mean monthly mean daily totals, and it demonstrates the quality of the new data sets currently available from the NSRDB.

14 SOLAR ENERGY↗

DOE OSTI2014

Modular Undersea Compressed Air Energy Storage (UCAES) System

This project has been devoted to the design, optimization, and cost analysis of a unique power plant with integral energy storage. The proposed facility combines a novel underwater compressed air energy storage (UCAES) system with a customized gas turbine generator, providing exceptional power management and overall efficiency. Unlike conventional CAES, opportunities for underwater storage are plentiful and proximal to the power grid. The UCAES system provides coastal and island communities a practical means for managing the volatility of large-scale wind and solar power resources. The result is higher renewable energy absorption and improved electrical reliability with reduced fossil fuel consumption. The UCAES power plant is composed of three major subsystems: The underwater air containment system (ACS), the air transport pipe (ATP), and the land-based power conversion system (PCS). The underwater ACS is made up of modular concrete shell units, structurally optimized for minimal material usage while employing conventional production methods and equipment. Each shell is designed to receive and control loose fill or gravel, serving as the ballast. The static nature of the final structures make them an asset to marine habitats and includes features intended to permit safe and cost-effective deployment. The ATP Connects the ACS modules to each other and to the on-land power conversion system and utilizes high density polyethylene (HDPE) pipe for low cost and long life. The PCS Houses the turbine-generator ‘expander modules’, with peak capacity of 12.3 MWe each, engineered from existing gas turbine equipment and includes electrically driven commercial 3-stage intercooled centrifugal compressors, each nominally drawing 6.6 MWe when matching the turbine flow requirements. The subsystems listed above are designed with the intent to serve as building-blocks to achieve a peak power output rating in the 40 to 120 MWe range, with 0.25 to 4 hours of energy storage capacity. The modular facility with integral energy storage provides some remarkable transient maneuvers and load-following features unachievable by competing technologies. The system can operate as a dispatchable power plant with a fuel-to-electric efficiency over 41%; substantially better that the average existing Hawaiian peak power generation assets. Optimal efficiency can be maintained while load-following due to modular PCS design and is operable with a range of liquid or gaseous fuels while meeting the most stringent California (CARB) emission standards. The system can operate as a peaking energy plant in discharge mode. Power ramp-up equivalent to 215% of continuous load rating within 1 second accomplished by simply turning off the electric compressor(s). Contrarily, the system can offer energy absorption during periods of grid surplus generation. The electric compressors may be sequenced on to absorb power within seconds. More moderate transitions are easily achieved with standard compressor control functions. The system offers unique features as compared to energy storage systems. ‘Round-trip efficiency’, as calculated by industry standard methods, is in the 90% range. The PCS equipment has a mean-time between overhauls of 80,000 hours, with maintenance costs of less than $0.005/kW-hr of electricity delivered. The underwater ACS structures and piping employ materials and designs specified to achieve a 75 year life. With the underwater containment modules qualified as a marine habitat, there would be no decommissioning costs. In conjunction with the engineering work invested in the design of the UCAES power plant, Brayton Energy has employed a team of manufacturing specialists, marine construction engineers, and power industry experts to create a comprehensive economic model that captures the many site-related variables and configuration options. The cost results and methodology have been validated by suppliers, engineers, and deployment specialists through a detailed case study on Hawaii. While creation of the parametric cost model was based on inputs specific to Hawaii, the proposed construction and deployment steps were chosen to be general enough to allow extrapolation across locations world-wide. Analysis of the proposed system shows it to be a viable option and addresses the principal challenges described by the Department of Energy by offering competitive costs, validated safety and reliability, consideration of the regulatory environment, and utilization of industry accepted practices and equipment. The UCAES system is recommended for immediate consideration in Hawaii. Estimation of time to complete planning, design, and construction of the facility is anticipated to take 3 to 5 years. Other coastal and island communities world-wide should realize similar benefits; as the results presented in this report are considered generally transferable to other locations.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2017

Bio Diesel Cellulosic Ethanol Research Project

The objective of the project is to create the Hendry County Sustainable Biofuels Center and initiate its research, development, and education programs. The mission is to develop engineering and economic assessment methods to evaluate the natural resources impacts of biomass farming and fuel conversion systems; provide sustainability assessments of specific biofuels productions proposals; develop biomass farming and fuel conversion systems that are compatible with south Florida ecosystem restoration priorities; create ecosystem services opportunities and structures to diversify farm income; monitor the range of research and development activities necessary to the creation of sutstainable biofuels production systems in south Florida, identify gaps in the regional research, and assist in the development and coordination of additional projects to fill out the required knowledge base; prepare the workforce of southwest Florida for employment in biofuels related professions; and assist businesses & governmental design and realize sustainable biofuels projects.

09 BIOMASS FUELS↗

DOE OSTI2025

Application of Ocean Thermal Energy Conversion (OTEC) Systems for Powering Safety Monitoring Systems of Offshore Oil and Gas Operations. OESI 2.0 M-1 T-1-P1.1 – Objective 1 Interim Report: Summary of Offshore Oil and Gas Well Monitoring Systems and Process Power Requirements

This report is part of a comprehensive research initiative aimed at evaluating the technoeconomic feasibility of deploying greenhouse gas (GHG) emissions monitoring systems powered by small-scale renewable energy sources on the U.S. Outer Continental Shelf (OCS). The study has three primary objectives: summarizing available GHG monitoring systems for the OCS, modeling a renewable marine energy source (specifically ocean thermal energy conversion, or OTEC), and modeling the collocation of OTEC power sources with offshore oil and gas activities to offset power demand.

02 PETROLEUM↗

DOE OSTI2015

Development of a concentrating solar power system using fluidized-bed technology for thermal energy conversion and solid particles for thermal energy storage

Concentrating solar power (CSP) is an effective way to convert solar energy into electricity with an economic energy-storage capability for grid-scale, dispatchable renewable power generation. However, CSP plants need to reduce costs to be competitive with other power generation methods. Two ways to reduce CSP cost are to increase solar-to-electric efficiency by supporting a high-efficiency power conversion system, and to use low-cost materials in the system. The current nitrate-based molten-salt systems have limited potential for cost reduction and improved power-conversion efficiency with high operating temperatures. Even with significant improvements in operating performance, these systems face challenges in satisfying the cost and performance targets. This paper introduces a novel CSP system with high-temperature capability that can be integrated into a high-efficiency CSP plant and that meets the low-cost, high-performance CSP targets. Unlike a conventional salt-based CSP plant, this design uses gas/solid, two-phase flow as the heat-transfer fluid (HTF); separated solid particles as storage media; and stable, inexpensive materials for the high-temperature receiver and energy storage containment. We highlight the economic and performance benefits of this innovative CSP system design, which has thermal energy storage capability for base-load power generation.

14 SOLAR ENERGY↗

DOE OSTI2025

Controlling Interfacial Energetics and Charge Transfer Rates in 2D Semiconductors: Fundamental Studies en Route to Photoelectrochemical Energy Conversion Beyond the Shockley-Queisser Limit (Final Scientific/Technical Report)

Current photovoltaic and solar-to-fuel technologies do not fully utilize the energy of sunlight because excess photon energy above the semiconductor band gap is rapidly lost as heat through hot-carrier thermalization. Overcoming this loss mechanism is critical, as hot-carrier-based energy conversion systems are predicted to exceed the conventional efficiency limit of ~33%. This project advanced fundamental understanding of hot-carrier energy conversion in two-dimensional (2D) semiconductors, with a focus on monolayer MoS 2 . Using a combination of electrochemical microscopy and in situ ultrafast spectroscopic measurements, this research directly demonstrated hot-carrier extraction from monolayer MoS 2 photoelectrodes in proof-of-concept liquid junction solar cells. These measurements established that hot-carrier transfer can compete with ultrafast carrier cooling at solid–liquid interfaces, providing unambiguous experimental evidence that hot-carrier extraction is feasible in atomically thin semiconductors under operating photoelectrochemical conditions. Beyond demonstration, the project identified design rules for tuning hot-carrier extraction rates relative to cooling rates in 2D semiconductor photoelectrodes. The outcomes of this research provide foundational thermodynamic and kinetic insights for the rational design of next-generation hot-carrier-enabled solar energy conversion systems. These findings have broad implications for photoelectrochemical solar fuels production, electrocatalysis, and emerging energy conversion architectures that seek to harness nonequilibrium charge carriers for enhanced efficiency.

14 SOLAR ENERGY↗

DOE OSTI2012

Identifying and bounding uncertainties in nuclear reactor thermal power calculations

Determination of the thermal power generated in the reactor core of a nuclear power plant is a critical element in the safe and economic operation of the plant. Direct measurement of the reactor core thermal power is made using neutron flux instrumentation; however, this instrumentation requires frequent calibration due to changes in the measured flux caused by fuel burn-up, flux pattern changes, and instrumentation drift. To calibrate the nuclear instruments, steam plant calorimetry, a process of performing a heat balance around the nuclear steam supply system, is used. There are four basic elements involved in the calculation of thermal power based on steam plant calorimetry: The mass flow of the feedwater from the power conversion system, the specific enthalpy of that feedwater, the specific enthalpy of the steam delivered to the power conversion system, and other cycle gains and losses. Of these elements, the accuracy of the feedwater mass flow and the feedwater enthalpy, as determined from its temperature and pressure, are typically the largest contributors to the calorimetric calculation uncertainty. Historically, plants have been required to include a margin of 2% in the calculation of the reactor thermal power for the licensed maximum plant output to account for instrumentation uncertainty. The margin is intended to ensure a cushion between operating power and the power for which safety analyses are performed. Use of approved chordal ultrasonic transit-time technology to make the feedwater flow and temperature measurements (in place of traditional differential-pressure- based instruments and resistance temperature detectors [RTDs]) allows for nuclear plant thermal power calculations accurate to 0.3%-0.4% of plant rated power. This improvement in measurement accuracy has allowed many plant operators in the U.S. and around the world to increase plant power output through Measurement Uncertainty Recapture (MUR) up-rates of up to 1.7% of rated power, while also decreasing the probability of significant over-power events. This paper will examine the basic elements involved in calculation of thermal power using ultrasonic transit-time technology and will discuss the criteria for bounding uncertainties associated with each element in order to achieve reactor thermal power calculations to within 0.3% to 0.4%. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2016

Optimizing Short-Term Operation of a FIRES-like Industrial Heat Supply Thermal Energy Storage System

The Firebrick Resistance-heated Energy-storage System (FIRES) is under development at MIT for two applications: (1) integration with the Nuclear Air-Brayton Combined Cycle (NACC), a high-performance power conversion system (PCS) that may be used with high- temperature advanced reactors; and (2) industrial heat supply. This paper describes some key features of FIRES and equivalent systems configured for industrial heat supply and presents an assessment of the revenue achievable by a system operating under the conditions expected for early demonstration FIRES installations. The greatest technical challenge of the 21. century is likely to be the effort to minimize the damage caused by global climate change. This effort will require massive reductions in greenhouse gas (GHG) emissions throughout our economy and a transition to an electric power system driven entirely by very-low-carbon generators. Many investigators agree that this will require a substantial increase in electricity generation and in the use of nuclear power, and there is growing awareness that this will also require new technologies and systems for managing and storing energy and matching intermittent supply of renewable resources with electricity demand. Thermal energy storage systems (TESS) will, in some applications, be much more cost effective than the more popular and widely discussed battery electric storage systems and may provide unique capabilities. The Firebrick Resistance-heated Energy-storage System (FIRES) is under development at MIT for two applications: (1) integration with the Nuclear Air-Brayton Combined Cycle (NACC), a high-performance power conversion system (PCS) that may be used with high-temperature advanced reactors like the Fluoride-salt-cooled High-temperature Reactor (FHR), molten salt reactor (MSR) and sodium-cooled fast reactors (SFR); and (2) industrial heat supply. FIRES installations include a stack of refractory firebrick with imbedded electric heaters and airflow channels, a compressor or air blower, and a duct system to connect the firebrick with the heat demand (turbine or industrial customer). Analysis of the FIRES design space has shown that the concept is suitable for a wide range of peak operating temperatures (from about 200 deg.C up to at least 1800 deg. C) and pressures (from ambient to at least 20 atmospheres) and offers very high energy density (up to 1 MWh per cubic meter of firebrick for high temperature systems) at very low cost (as low as $5/kWh). These results favor early demonstration of FIRES. If the cost target of $5/kWh for FIRES systems were achieved, even the lowest expected operating income calculated here could cover the capital cost of a 10 MWh system in a single year. If the FIRES system were assumed to operate for at least 10 years, this level of operating income could readily recover a capital investment up to $50/kWh, which is simultaneously much cheaper than the costs expected for near-future battery systems (in excess of $200/kWh) and much more expensive than the small, low temperature firebrick systems already available for domestic heating. This provides a large margin for unexpected development costs and other uncertainties. FIRES would set a minimum price of electricity near that of natural gas-improving nuclear, wind, and solar economics while reducing greenhouse gas emissions from the industrial sector. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2023

Chapter 14: Surface plasmon resonance enhanced artificial photosynthesis of chemical fuels for energy storage

Nanostructured noble metals such as Au, Ag, and Cu have interesting optical properties because of the oscillation motions of their surface electrons upon strong coupling with light under resonance conditions. This resonant oscillation motion of conduction electrons refers to surface plasmon resonance (SPR) and localized SPR (LSPR) when localized near the surface of a nanoparticle. The extinction spectrum of a solution of plasmonic nanoparticles has tunable wavelength responses from UV to NIR due to strong light scattering and absorption which are highly sensitive to the permittivity of the nanoparticles, their sizes and shapes, and chemical environment. Strong light scattering due to the LSPR of plasmonic nanoparticles creates a strong localized and far-field intensity capable of enhancing light absorption characteristics of a chromophore near a plasmonic surface. Engineering the chromophores’ radiative decay dynamics can be done by 1) increasing its radiative decay rate to increase its photoluminescence intensity and 2) increasing its nonradiative decay rates associated to direct charge transfer to the metal surface. Such interesting photophysical properties of a chromophore can be extended to other light-absorbing materials such as semiconductor thin films and nanostructures. This plasmonic effect on the photophysics of a light-absorbing material can be theoretically and experimentally validated. The phenomenon has also been applied to advanced optoelectronic devices such as organic light-emitting diodes (OLED)1 and organic photovoltaics (OPV).2-4 The local field created by the SPR can provide an intense EM field to enhance photoluminescence emission of an organic chromophore5-8 and Raman scattering of an organic molecule, and single-molecule Raman9-10 can be detected on specially designed LSPR substrate. (Figure 1 on SPR for energy) Recent studies suggest that LSPR can be incorporated in light-harvesting and conversion systems to increase energy conversion in a solar cell and photoelectrochemical cell and chemical transformations of CO2 to chemical fuels.11-12 Plasmonic active metals naturally exhibit catalytic activities for electrochemical fuel conversion that can be enhanced by engineering their structures to form unique catalytic structures such as symmetry-broken Au-Cu Janus nanocrystals.13 These studies are critical to addressing the global challenges of energy14-15 and CO2 emission from nonrenewable sources such as coal, petroleum, and natural gas.16-17 Electrochemical systems comprised of unique photonic structures and functions that enable efficient and affordable energy harvesting/conversion/storage are highly desired for providing safe and environment-friendly energy sources. This chapter reviews our recent work of LSPR enabled photoelectrochemical water splitting and recent advances in LSPR-enabled CO2 reduction and photochemical reactions reported in the literature. Scientific and technical challenges of applying LSPR to enhance these energy conversion and storage systems are discussed at the conclusion of this chapter.

Pan, Shanlin↗

DOE OSTI2020

Effects of Heat Pipe Failures in Microreactors

Microreactors provide new opportunities for nuclear reactor applications given their long-lived fuel source, compact size, portability, reliability as it relates to safety and their self-regulating nature. To take advantage of these opportunities there are technological challenges that need to be overcome. One advancing technology often used in conjunction with microreactor designs are heat pipes, which are used for heat removal from the reactor core to the power conversion system. Heat pipes are a substitute for the traditional system in which the same fluid used as coolant in the reactor is then used as the working fluid in the power conversion system. This document describes how heat pipes operate, what happens when a heat pipe fails, and what codes can be used to simulate the results. Our analyses show that a single/double heat pipe failure results in a temperature increase of 15-50°C respectively in surrounding heat pipes. Heat pipe microreactors could be easily designed such that this increase is within the maximum parameters allowable for safety and does not result in cascading heat pipe failure. Thus, such failures do not lead to severe degradation of the reactor.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2016

VASIMR{sup R} Interfaced High Temperature Gas-Cooled Fast Reactor for Space Applications

This project was undertaken to assess the feasibility and advantages of utilizing a gas-cooled fast reactor to supply power to an electric propulsion system for deep space exploration to Europa, one of Jupiter's moons. Specifically, the primary objective of this project was to design a 9 MWe gas cooled fast reactor with an accompanying power conversion system to supply electricity to multiple electrically-powered thrusters for a four year mission duration. The thruster design chosen for this analysis is the Variable Specific Impulse Magnetoplasma Rocket (VASIMR). The VASIMR propulsion system, currently being developed by Ad Astra Rocket Company (AARC), is an electric propulsion rocket that uses electric power to accelerate neutral plasma propellant. Advanced electric space propulsion systems such as the VASIMR offer unique capabilities that allow for higher exhaust velocities that are up to ten times that of traditional chemical rockets. Furthermore, the thrust and specific impulse of the VASIMR system can be varied in order to achieve optimal travel times to given destinations for a desired payload. As a result, electric propulsion systems characteristically have lower ratios of system mass to power output than chemical rockets. This ratio is commonly known as the alpha parameter. Alpha parameters of approximately 10 kg/kWe or less make electric propulsion more attractive for deep space exploration missions in terms of resource efficiency and cost. However, the primary challenge with electric propulsion is to develop a high power density source of electricity in order to minimize the total system mass. The alpha parameter is the main benchmark used in this project to test whether or not the proposed coupled gas cooled reactor and power conversion system design is more competitive than other proposed systems. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2012

The pre-conceptual design of the nuclear island of ASTRID

The CEA is involved in a substantial effort on the ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration) pre-conceptual design in cooperation with EDF, as experienced Sodium-cooled Fast Reactor (SFR) operator, AREVA, as experienced SFR Nuclear Island engineering company and components designer, ALSTOM POWER as energy conversion system designer and COMEX NUCLEAIRE as mechanical systems designer. The CEA is looking for other partnerships, in France and abroad. The ASTRID preliminary design is based on a sodium-cooled pool reactor of 1500 MWth generating about 600 MWe, which is required to guarantee the representativeness of the reactor core and the main components with regard to future commercial reactors. ASTRID lifetime target is 60 years. Two Energy Conversion Systems are studied in parallel until the end of 2012: Rankine steam cycle or Brayton gas based energy conversion cycle. ASTRID design is guided by the following major objectives: improved safety, simplification of structures, improved In Service Inspection and Repair (ISIR), improved manufacturing conditions for cost reduction and increased quality, reduction of risks related to sodium fires and water/sodium reaction, and improved robustness against external hazards. The core is supported by a diagrid, which lay on a strong back to transfer the weight to the main vessel. AREVA is involved in a substantial effort in order to improve the core support structure in particular regarding the ISIR and the connection to primary pump. In the preliminary design, the primary system is formed by the main vessel and the upper closure comprising the reactor roof, two rotating plugs - used for fuel handling - and the components plugs located in the roof penetrations. The Above Core Structure deflects the sodium flow in the hot pool and provides support to core instrumentation and guidance of the control rod drive mechanisms. The number of the major components in the main vessel, primary pumps, Intermediate Heat Exchangers, and Decay Heat Exchangers are now under consideration. Under normal conditions, power release is achieved using the steam/water plant (in case of Rankine steam cycle) or the gas plant (in case of Brayton gas cycle). The diverse design and operating modes of Decay Heat Removal systems provide protection against common cause failures. A Decay Heat Removal system through the reactor vault is in particular studied with the objective to complement Direct Reactor Cooling systems. At this stage of the studies, the secondary system comprises four independent sodium loops (two and three sodium loops configurations are also investigated). Each loop includes one mechanical pump (or a large capacity Annular Linear Induction Electromagnetic Pump), and three modular Steam Generator Units characterized by once through straight tube units with a ferritic tube bundle; nevertheless, helical coil steam generator with tubes made of Alloy 800, and inverted type steam generator with a ferritic tube bundle are also investigated. The limited power of each modular Steam Generator Unit allows the whole secondary loop to withstand a large water/sodium reaction consecutive to the postulated simultaneous rupture of all the heat exchange tubes of one module. The arrangement of the components is based on the 'Regain' concept, in which the secondary pump is situated at a low level in the circuit; conventional arrangement, as SUPERPHENIX type, is a back-up option. Alternative arrangements based on gas cycles are also studied together with Na-gas heat exchanger design. This paper presents a status of the ASTRID pre-conceptual design. The most promising options are highlighted as well as less risky and back-up options. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗