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Title: Mass optimization of a supercritical CO 2 Brayton cycle with a direct cooled nuclear reactor for space surface power

Abstract

A long life, reliable, and compact surface power system will be necessary to achieve future goals in space exploration. This application uniquely requires the system to be optimized with respect to mass because system mass directly drives the space launch cost associated with transporting the system to its desired location. In this study, a supercritical CO 2 Brayton cycle coupled to a direct-cooled nuclear reactor was designed and optimized for mass. Robust models were developed for each Brayton cycle component in order to model the cycle performance. The three most massive components of this cycle are the radiator-based heat rejection system (subsequently referred to as the “radiator”), recuperator, and reactor. Mass correlations for the recuperator and radiator were established through interactions with component experts from industry and national labs. A reactor model was developed to predict the minimum mass reactor that satisfies neutronic and thermal limitations for given cycle conditions. The system optimization explores tradeoffs between the reactor, recuperator, and radiator sizes in order to identify the least massive system that will satisfy the power (40 kWe) and life (10 yr) requirements. To explore the effects of turbine inlet temperature on system mass, three types of microtube and shell recuperatormore » technologies were considered: baseline stainless steel (which is consistent with the industry partner’s current designs), stainless steel with non-heritage tube sizes (which requires further development of manufacturing techniques), and Inconel (which is not a current/legacy design). Both stainless steel designs have a temperature limit of 823 K, which limits the turbine inlet temperature to 900 K. The baseline stainless steel design results in a combined mass of 738 kg. The stainless steel design allowing for non-heritage tube sizes reduces the combined mass to 674 kg (a 9% improvement). The Inconel design leads to an optimal turbine inlet temperature of 1120 K and reduces the combined mass to 391 kg (a 47% improvement). Furthermore, the interesting conclusion from this study include: (1) radiator mass dominates the total mass, and this drives the cycle to relatively high heat rejection temperatures resulting in a compressor inlet state point that is not close to the vapor dome; thus, the typical advantages of an sCO 2 system are not realized, and a working fluid with a higher critical temperature may be more suitable, and (2) neutronic limitations cause the reactor size to be relatively unaffected by the power level.« less

Authors:
 [1];  [1]
  1. Univ. of Wisconsin, Madison, WI (United States)
Publication Date:
Research Org.:
Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE), Nuclear Energy University Program (NEUP)
Contributing Org.:
Creare, Sandia National Laboratory
OSTI Identifier:
1646962
Grant/Contract Number:  
NE0008679
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Applied Thermal Engineering
Additional Journal Information:
Journal Volume: 163; Journal ID: ISSN 1359-4311
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
Supercritical carbon dioxide; Brayton cycle; Space power generation; Space dynamic power; Mass optimization; Space surface power

Citation Formats

Sondelski, Becky, and Nellis, Greg. Mass optimization of a supercritical CO2 Brayton cycle with a direct cooled nuclear reactor for space surface power. United States: N. p., 2019. Web. doi:10.1016/j.applthermaleng.2019.114299.
Sondelski, Becky, & Nellis, Greg. Mass optimization of a supercritical CO2 Brayton cycle with a direct cooled nuclear reactor for space surface power. United States. doi:10.1016/j.applthermaleng.2019.114299.
Sondelski, Becky, and Nellis, Greg. Fri . "Mass optimization of a supercritical CO2 Brayton cycle with a direct cooled nuclear reactor for space surface power". United States. doi:10.1016/j.applthermaleng.2019.114299. https://www.osti.gov/servlets/purl/1646962.
@article{osti_1646962,
title = {Mass optimization of a supercritical CO2 Brayton cycle with a direct cooled nuclear reactor for space surface power},
author = {Sondelski, Becky and Nellis, Greg},
abstractNote = {A long life, reliable, and compact surface power system will be necessary to achieve future goals in space exploration. This application uniquely requires the system to be optimized with respect to mass because system mass directly drives the space launch cost associated with transporting the system to its desired location. In this study, a supercritical CO2 Brayton cycle coupled to a direct-cooled nuclear reactor was designed and optimized for mass. Robust models were developed for each Brayton cycle component in order to model the cycle performance. The three most massive components of this cycle are the radiator-based heat rejection system (subsequently referred to as the “radiator”), recuperator, and reactor. Mass correlations for the recuperator and radiator were established through interactions with component experts from industry and national labs. A reactor model was developed to predict the minimum mass reactor that satisfies neutronic and thermal limitations for given cycle conditions. The system optimization explores tradeoffs between the reactor, recuperator, and radiator sizes in order to identify the least massive system that will satisfy the power (40 kWe) and life (10 yr) requirements. To explore the effects of turbine inlet temperature on system mass, three types of microtube and shell recuperator technologies were considered: baseline stainless steel (which is consistent with the industry partner’s current designs), stainless steel with non-heritage tube sizes (which requires further development of manufacturing techniques), and Inconel (which is not a current/legacy design). Both stainless steel designs have a temperature limit of 823 K, which limits the turbine inlet temperature to 900 K. The baseline stainless steel design results in a combined mass of 738 kg. The stainless steel design allowing for non-heritage tube sizes reduces the combined mass to 674 kg (a 9% improvement). The Inconel design leads to an optimal turbine inlet temperature of 1120 K and reduces the combined mass to 391 kg (a 47% improvement). Furthermore, the interesting conclusion from this study include: (1) radiator mass dominates the total mass, and this drives the cycle to relatively high heat rejection temperatures resulting in a compressor inlet state point that is not close to the vapor dome; thus, the typical advantages of an sCO2 system are not realized, and a working fluid with a higher critical temperature may be more suitable, and (2) neutronic limitations cause the reactor size to be relatively unaffected by the power level.},
doi = {10.1016/j.applthermaleng.2019.114299},
journal = {Applied Thermal Engineering},
issn = {1359-4311},
number = ,
volume = 163,
place = {United States},
year = {2019},
month = {8}
}

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