Two AMTEC units were operated for over 300 hours and then dissected and examined. The converter units were fabricated by Advanced Modular Power Systems, Inc. using a cold end condenser manufactured by Creare. Inc. and were constructed with a stainless steel housing and stainless steel sheathed molybdenum wick. Creare Unit 1 operated for 342 hours with condenser and BASE tube cell temperatures of 663 K and 1003 K respectively: the output power varied from an initial 68 mw to a final 25 mw. Operation of Creare Unit 1 was halted due to a low initial output current and power that remained unchanged. Creare Unit 2 ran for 575 hours with condenser and BASE tube cell temperatures of 543 K and 978 K respectively: the output power varied from an initial 2.6 watts to a final 1.8 watts. Operation of Creare Unit 2 was halted due to a low power output after the heater unit supplying heat failed and was replaced. The expected output power for both units was about 1 to 4 watts. Both units were subsequently disassembled and dissected to determine a failure mechanism and analyze the internal sodium distribution. Analysis showed that the internal sodium was primarily distributed near the condenser end of the converter units extending out to a distance of 3.2 cm. No significant amounts of sodium deposits were observed in the BASE tubes or plenum of either converter unit. The wick was sliced into 2 to 3 mm sections and analyzed using a SEM and X-ray florescence to determine its sodium distribution. The sodium distribution along the wick from the condenser to the base of the evaporator was observed to be continuous throughout. The analysis however could not determine how the sodium flow varied during operation. The low power output of Creare Unit 1 and the final low power output of Creare Unit 2 was tentatively determined to result from a fracture of the structural joint at the BASE tube braze seal on several of the tubes.


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    Title :

    Metallurgical examination of an AMTEC unit


    Contributors:

    Conference:

    Space Technology and Applications International Forum - 2001 ; 2001 ; Albuquerque, New Mexico


    Published in:

    AIP Conference Proceedings ; 552 , 1 ; 1094-1099


    Publication date :

    2001-02-02


    Size :

    6 pages





    Type of media :

    Conference paper


    Type of material :

    Electronic Resource


    Language :

    English



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