AMTEC recirculating test cell component testing and operation

Abstract

Alkali Metal Thermoelectric Converter operation in a recirculating test cell (RTC) requires a small electromagnetic pump (EM) and a high temperature 13" alumina solid electrolyte (BASE) to metal seal. This paper describes the design of an EM pump and an active metal braze seal as well as initial operation of a cell using these components. The EM pump delivered 0.25 cm3/min against a 28 psia head. A braze seal system was selected after shear strength tests of Ta or Nb brazed to BASE by a variety of fillers including TiCuNi, TiNi, and TiNiCr. The TiCuNi filler was chosen for environment cell testing and showed no failure or observed degradation after short term tests up to 1055K. The EM pump and the Nb/TiCuNi/BASE seal were used in a test that demonstrated all the operational functions of the RTC for the first time a t JPL. An increase in the radiation reduction factor (Z) a t constant input power was observed indicating that the condenser was being wet by sodium resulting in an increased reflectivity.

Kinetics and Transport at AMTEC Electrodes: II . Temperature Dependence of the Interfacial Impedance of Na(g)/Porous Mo/Na‐Beta′ Alumina

“…Typical data are shown in Fig. 2, and in previous papers (2,3,6,7). The quality of current impedance data for Mo and WRh electrodes has been demonstrated previously, along with some fits to data for thin Mo electrodes (2,3).…”

“…2, and in previous papers (2,3,6,7). The quality of current impedance data for Mo and WRh electrodes has been demonstrated previously, along with some fits to data for thin Mo electrodes (2,3). Following subtraction of Rs~R, and in some cases a series inductance as well, from the impedance data it was converted to admittance data in order to find RII (~, E) and CII (~o, E).…”

“…The experimental conditions, measurements, and some of the data analysis techniques have been described in detail in previous papers (2)(3)(4)(5)(6)(7) and in Part I (1). The thin, porous Mo electrodes which were used in these experiments were deposited by magnetron sputtering utilizing an S-gun (Sputtered Films, Incorporated) Mo target 17.8 cm below the masked, rotating BASE tube (15,17,20).…”

“…VT.T~ [3] The standard reaction rate, defined for unit activity sodium is k ~ The average value of Jo~ -~ is about 120 (AKmPa-lm -2) and that of k~ is about 1.1 • 10 -3 for a collection of data for many 0.5 ~m Mo electrodes and two 1.0 ~m Rh-W electrodes. All of these electrodes had been allowed to mature at high temperature and showed low, stable values of the interfacial capacitance vs. potential, indicating the electrodes were free of oxide phases such as Na2MoO4, Na2Mo~O6, and Na2WO4 which greatly increase the effective interfacial reaction area, and hence both the observed rate and capacitance.…”

“…(1)] discusses the basic model for the potential-dependent resistance, RACT, observed in AMTEC cell impedance data, as well as the approximations and weaknesses of the model. Results interpreted via a simple model have been published previously (2)(3)(4). This paper will present the dependence of the interfacial impedance parameters, RACT and Ci~rr, on the electrochemical potential, frequency, and temperature.…”