Papers by Shannon Bragg-Sitton
Combining Energy Systems with Security Resiliency and Efficiency Panel
Nucleation and Atmospheric Aerosols, 2005
Reliable reactor control is important to reactor safety, both in terrestrial and space systems. F... more Reliable reactor control is important to reactor safety, both in terrestrial and space systems. For a space system, where the time for communication to Earth is significant, autonomous control is imperative. Based on feedback from reactor diagnostics, a controller must be able to automatically adjust to changes in reactor temperature and power level to maintain nominal operation without user intervention. Model-based predictive control (MBPC) is investigated as a potential control methodology for reactor start-up and transient operation in the presence of either a constant or a time varying external source. Bragg-Sitton and Holloway [Bragg-Sitton, S.M., Holloway, J.P., 2004. Reactor start-up and control methodologies. In: El-Genk, M. (Ed.), Proceedings of the Space Technology and Applications International Forum (STAIF-2004), AIP Conference Proceedings 699, pp. 614-622.] assessed the applicability of MBPC to reactor startup from a cold, zero-power condition in the presence of a time-varying external radiation source, where large fluctuations in the external radiation source can significantly impact a reactor during start-up operations. Here the MBPC algorithm is applied using the point kinetics model to describe the reactor dynamics, with a single group of delayed neutrons and a fast neutron lifetime of 10 À7 s. Controller stability is assessed by carefully considering the dependencies of each component in the defined cost (objective) function and its subsequent effect on the selected ''optimal'' control maneuvers. Additional analysis demonstrates the effectiveness of the controller when a lower fidelity reactor kinetics model is adopted for the model system versus using a full six-group delayed neutron representation in the point kinetics equations to represent the ''real'' system operation.
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Apr 28, 2022
The Department of Energy (DOE) Fuel Cycle Research and Development (FCRD) Advanced Fuels Campaign... more The Department of Energy (DOE) Fuel Cycle Research and Development (FCRD) Advanced Fuels Campaign (AFC) is conducting research and development on enhanced Accident Tolerant Fuels (ATF) for light water reactors (LWRs). This mission emphasizes the development of novel fuel and cladding concepts to replace the current zirconium alloy-uranium dioxide (UO 2 ) fuel system. The overall mission of the ATF research is to develop advanced fuels/cladding with improved performance, reliability and safety characteristics during normal operations and accident conditions, while minimizing waste generation. The initial effort will focus on implementation in operating reactors or reactors with design certifications. To initiate the development of quantitative metrics for ATR, a LWR Enhanced Accident Tolerant Fuels Metrics Development Workshop was held in October 2012 in Germantown, MD. This paper summarizes the outcome of that workshop and the current status of metrics development for LWR ATF.
Trade names and trademarks are used in this report for identification only. This usage does not c... more Trade names and trademarks are used in this report for identification only. This usage does not constitute an official endorsement, either expressed or implied, by the National Aeronautics and Space Administration.
Nucleation and Atmospheric Aerosols, 2004
Experiments have been designed to characterize the coolant gas flow in two space reactor concepts... more Experiments have been designed to characterize the coolant gas flow in two space reactor concepts that are currently under investigation by NASA Marshall Space Flight Center and Los Alamos National Laboratory: the directdrive gas-cooled reactor (DDG) and the SAFE-100 heatpipe-cooled reactor (HPR). For the DDG concept, initial tests have been completed to measure pressure drop versus flow rate for a prototypic core flow channel, with gas exiting to atmospheric pressure conditions. The experimental results of the completed DDG tests presented in this paper validate the predicted results to within a reasonable margin of error. These tests have resulted in a re-design of the flow annulus to reduce the pressure drop. Subsequent tests will be conducted with the re-designed flow channel and with the outlet pressure held at 150 psi (1 MPa). Design of a similar test for a nominal flow channel in the HPR heat exchanger (HPR-HX) has been completed and hardware is currently being assembled for testing this channel at 150 psi. When completed, these test programs will provide the data necessary to validate calculated flow performance for these reactor concepts (pressure drop and film temperature rise).
Nucleation and Atmospheric Aerosols, 2003
This paper describes the concept and preliminary component testing of a gas-cooled, UN-fueled, pi... more This paper describes the concept and preliminary component testing of a gas-cooled, UN-fueled, pin-type reactor which uses Heme gas that goes directly into a recuperated Brayton system to produce electricity for nuclear electric propulsion. This Direct-Drive Gas-Cooled Reactor (DDG) is designed to be subcritical under water or wetsand immersion in case of a launch accident. Because the gas-cooled reactor can directly drive the Brayton turbomachinery, it is possible to configure the system such that there are no external surfaces or pressure boundaries that are refractory metal, even though the gas delivered to the turbine is 1 144 K. The Heme gas mixture is a good heat transport medium when flowing, and a good insulator when stagnant. Judicious use of stagnant cavities as insulating regions allows transport of the 1144-K gas while keeping all external surfaces below 900 K. At this temperature superalloys (Hastelloy or Inconel) can be used instead of refractory metals. Super-alloys reduce the technology risk because they are easier to fabricate than refractory metals, we have a much more extensive knowledge base on their characteristics, and, because they have a greater resistance to oxidation, system testing is eased. The system is also relatively simple in its design: no additional coolant pumps, heat exchanger, or freeze-thaw systems are required. Key to success of this concept is a good knowledge of the heat transfer between the fuel pins and the gas, as well as the pressure drop through the system. This paper describes preliminary testing to obtain this key information, as well as experience in demonstrating electrically heated testing of simulated reactor components.
Dual Plenary Session: Paths to a Sustainable Future
Proceedings of the Start-up Meeting of the OECD-NEA Expert Group on Accident Tolerant Fuels for LWRs, 28-29 April 2014, OECD-NEA HQ
Overview of the U.S. DOE Accident Tolerant Fuel Development Program
Nuclear Driven Water Desalination
Elsevier eBooks, 2021
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Feb 7, 2024
of total energy consumption, including electricity, heating, industry, and transportation. 80% fo... more of total energy consumption, including electricity, heating, industry, and transportation. 80% fossil fuels 20% non-fossil sources The U.S. Department of Energy is doubling down on the commitment to clean energy • Energy Earthshots TM will accelerate breakthroughs of more abundant, affordable, and reliable clean energy solutions within the decade. They will drive the major innovation breakthroughs that we know we must achieve to solve the climate crisis, reach our 2050 net-zero carbon goals, and create the jobs of the new clean energy economy.
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Oct 5, 2022
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Mar 30, 2022
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Oct 31, 2023
Unique INL site, infrastructure, and facilities enable energy and security RD&D at scale 49 Radio... more Unique INL site, infrastructure, and facilities enable energy and security RD&D at scale 49 Radiological facilities/activities 17.5 Miles railroad for shipping nuclear fuel 44 Miles primary roads (125 miles total) 9 Substations with interfaces to two power providers 3 Fire Stations 128 Miles high-voltage transmission & distribution lines 4 Operating reactors 22 Hazard Category II & III non-reactor facilities/ activities 7 Addressing the global challenge: Climate change U.S. electricity generation and emissions, World Economic Forum 10 The U.S. achieved a record of 41% electricity from low-carbon sources in 2022-with the remainder from natural gas and coal.
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Aug 31, 2023
The present study analyzes the economic viability of an Integrated Energy System (IES) that coupl... more The present study analyzes the economic viability of an Integrated Energy System (IES) that couples a Reverse Osmosis (RO) water desalination facility with a Nuclear Power Plant (NPP). The case study is conducted in collaboration with Arizona Public Service (APS), the operating owner of the Palo Verde Generating Station (PVGS) NPP. Cooling water for the reactor steam cycle is derived from treated effluent from municipal wastewater treatment plants. APS has established a long-term water resources program to effect a substantial reduction in plant cooling costs through advanced treatment and cooling technologies, and through the use of alternative water sources to replace the increasingly expensive effluent. One possible option is to replace some amount of the annual volume of effluent with brackish groundwater from a local regional aquifer. Although much less expensive than the municipal effluent, the quantity of brackish groundwater that could be used for plant cooling is limited as a result of the salinity and its impact on plant operation. Consequently, supplemental treatment could be required such that a greater amount of brackish groundwater could be used to reduce the demand on effluent. A study was conducted in 2018 by Idaho National Laboratory (INL) to investigate the economics of a PVGS onsite RO desalination plant that would reduce the salinity of a municipal effluent and brackish water blend to an acceptable level. One of the main findings of that study was that the overall economics of water desalination can be greatly improved if, in addition to cooling water for PVGS, potable water could also be produced and sold for profit. In fact, the study concluded that only producing cooling water for PVGS via RO desalination is not economically viable. The present report investigates the economic impact of a large, regional RO desalination plant that could provide potable water for the region, considering the conclusions from the 2018 scoping study. The study looks in particular at the water-market situation for the developing municipalities in the west valley of Phoenix. In addition to providing potable water for the municipalities, the existing infrastructure that conveys effluent to the Palo Verde plant and onsite water treatment facilities could be used to manage the RO concentrate. The processed concentrate could lead to a cost reduction in plant cooling by replacing some amount of effluent. The analysis reported here considers two cases (for various scenarios). First, the Base Case considers that neither the regional nor the onsite RO is built. The 2018 INL study showed that some brackish water can be blended with the municipal effluent water without having to build the onsite RO. That correspond to the maximum economically profitable option. The Base Case is where APS pumps the maximum volume of less-expensive brackish water (limited by water chemistry in the circulating water system), i.e. the case for which cooling water acquisition and treatment cost are lowest (without RO). Second, the proposed RO Case includes two RO plants, one onsite at PVGS and another larger, regional RO plant close to the brackish water wells. The regional RO produces potable water that is sold to the regional municipalities, while the PVGS onsite RO treats (part of) the regional ROs' concentrate and brackish water blend. The desalinated water from the PVGS RO is used in the circulating water system at PVGS. The analysis evaluates the difference in economics, using the Net Present Value (NPV) and Internal Rate of Return (IRR), between the cases. By comparing the two cases, in addition to evaluating the economics of the regional RO, we can also assess the impact of the regional RO on PVGS operational costs and, consequently, APS economics. The study shows that there exist combinations of regional RO and PVGS RO sizes for which the total blowdown and water chemistry limits at PVGS (including regional RO concentrate treatment at PVGS) are satisfied. However, such combinations only exist if no additional brackish water is directly mixed in the tertiary water system at PVGS. This leads to higher Levelized Costs of Potable Water (LCOPW) compared to cases where additional brackish water is injected (but violate the physical constraints). Additional studies are suggested to investigate the benefit of additional brackish water injection (lowers cooling water cost) versus the cost of lifting the physical constraints, e.g. building additional evaporation ponds. Staying in the case of no additional brackish water and satisfying the existing PVGS constraints, the lowest LCOPW (~0.5 $/m 3 ) can be achieved with a size of the regional RO of ~1.4e7 m 3 /yr (11000 AF/yr) capacity, which leads to ~8.63e6 m 3 /yr (7000 AF/yr) of potable water while no onsite RO at PVGS is built. Considering the viii residential water demand model developed for the Phoenix west valley, the NPV for this regional RO would be ~$100 million if all municipalities in the vicinity participate from the beginning of the project. ix CONTENTS ABSTRACT .
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Papers by Shannon Bragg-Sitton