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Title: Alkali Metal Heat Pipe Life Issues

Abstract

One approach to fission power system design uses alkali metal heat pipes for the core primary heat-transfer system. Heat pipes may also be used as radiator elements or auxiliary thermal control elements. This synopsis characterizes long-life core heat pipes. References are included where information that is more detailed can be found. Specifics shown here are for demonstration purposes and do not necessarily reflect current Nasa Project Prometheus point designs. (author)

Authors:
 [1]
  1. Marshall Space Flight Center, National Aeronautics and Space Administration, Huntsville, Alabama, 35812 (United States)
Publication Date:
Research Org.:
American Nuclear Society, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
OSTI Identifier:
21160757
Resource Type:
Conference
Resource Relation:
Conference: ICAPP'04: 2004 international congress on advances in nuclear power plants, Pittsburgh, PA (United States), 13-17 Jun 2004; Other Information: Country of input: France; 61 refs; Related Information: In: Proceedings of the 2004 international congress on advances in nuclear power plants - ICAPP'04, 2338 pages.
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; ALKALI METALS; CONTROL ELEMENTS; DESIGN; FISSION; HEAT; HEAT PIPES; HEAT TRANSFER; NASA; POWER SYSTEMS

Citation Formats

Reid, Robert S. Alkali Metal Heat Pipe Life Issues. United States: N. p., 2004. Web.
Reid, Robert S. Alkali Metal Heat Pipe Life Issues. United States.
Reid, Robert S. 2004. "Alkali Metal Heat Pipe Life Issues". United States. doi:.
@article{osti_21160757,
title = {Alkali Metal Heat Pipe Life Issues},
author = {Reid, Robert S.},
abstractNote = {One approach to fission power system design uses alkali metal heat pipes for the core primary heat-transfer system. Heat pipes may also be used as radiator elements or auxiliary thermal control elements. This synopsis characterizes long-life core heat pipes. References are included where information that is more detailed can be found. Specifics shown here are for demonstration purposes and do not necessarily reflect current Nasa Project Prometheus point designs. (author)},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2004,
month = 7
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

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  • The use of high-power heat pipes in space power systems requires a means of life prediction. The design lifetimes required make experimental determination of life impractical. Thermochemical modeling of heat pipe corrosive failure modes has been investigated as a means of making such prediction. Results have been applied to tests of molybdenum-lithium heat pipes operating from 1400 to 1500/sup 0/K. A free energy minimization routine coupled to a hydrodynamic model of the operating heat pipe has been used to give local equilibrium values of reaction products as a function of operating time. The predicted reactions for critical regions of themore » heat pipe were compared with limited results of post-test examinations. Corrosive damage to the heat pipe wick structure was correlated with high oxygen and nitrogen activity in the evaporator region of the heat pipe.« less
  • Loss of sodium oxide into a gas phase comprised of low to high pressure sodium at typical AMTEC operating conditions does not seem indicated as a life limiting step under projected conditions. Sodium oxide loss is strongly thermally activated and strongly suppressed by external sodium gas pressure. However, loss of sodium oxide into liquid sodium may be, but is not clearly known to be, much more rapid than loss into the gas phase and could result both BASE degradation and enhanced corrosion of other AMTEC components. This favors conservative selection of vapor-fed cell designs and may significantly influence materials selectionmore » and use of getters.« less
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  • Experimental lifetime performance studies currently in progress use Niobium-1% Zirconium (Nb-1Zr) and Titanium (Ti) heat pipes with potassium (K) as the working fluid. A heat pipe life-test matrix has been developed for testing the heat pipes. Because the corrosion rates in alkali metal heat pipes are affected by temperature and working fluid evaporation flux, the variable parameters of the experimental matrix are established as steady operating temperature and input heat flux density. Total impurity inventory is a factor in corrosion rate so impurity levels are being evaluated in the heat pipe materials before and after testing. Eight Nb-1Zr/K heat pipesmore » were designed, fabricated, and tested. Two of the heat pipes have completed testing whereas the other six are currently in test. These are gravity-assist heat pipes operating in a reflux mode. The heat pipes are tested by sets, one set of two and two sets of three heat pipes. Three Ti/K heat pipes are also in life test. These heat pipes are tested as a set in a horizontal position in a capillary pumped annular flow mode. Each of the heat pipes is encapsulated in a quartz vacuum container with a water calorimeter over the vacuum container for power throughput measurements. Thermocouples are attached to the heat pipes for measuring temperature. Heat input to the heat pipes is via an rf coil. The heat pipes are operating at between 800 and 900 K, with heat input fluxes of 13.8 to 30 W/sq cm. Of the Nb-1Zr/K heat pipes, two of the heat pipes have been in operation for 14,000 hours, three over 10,000 hours, and three over 7,000 hours. The Ti/K heat pipes have been in operation for 1,266 hours. 5 refs., 4 figs., 1 tab.« less
  • The demonstration testing duration requirements to establish a quantitative measure of assurance of expected lifetime for heat pipes was determined. The heat pipes are candidate devices for transporting heat generated in a nuclear reactor core to thermoelectric converters for use as a space-based electric power plant. A Bayesian analysis technique is employed, utilizing a limited Delphi survey, and a geometric mean accelerated test criterion involving heat pipe power (P) and temperature (T). Resulting calculations indicate considerable test savings can be achieved by employing the method, but development testing to determine heat pipe failure mechanisms should not be circumvented.