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Unique Features of Dynamic Isotope Power Systems for High-Requirements Spacecraft

Description: The Dynamic Isotope Power System, designed for spacecraft requiring prime power in the 500-to-2000 watt range, has been successfully built and ground tested. A number of studies, summarized herein, have demonstrated the advantages of using such a power system instead of the conventional solar system, for a variety of earth-orbit missions. These advantages stem from the unique nature of the dynamic isotope system, different in kind from solar power systems. As a result, in many cases, the spacecraft design can be significantly simplified and more closely harmonized with mission requirements. This overall advantage can be crucial in missions which have stringent pointing, stability, viewing and/or positioning requirements.
Date: August 1, 1980
Creator: Raab, Bernard
Partner: UNT Libraries Government Documents Department

Pu-238 fuel form activities, June 1-30, 1980

Description: This monthly report for Pu-238 Fuel Form Activities has two main sections: SRP-PuFF Pu-238 Fuel Form Production Processes and SRL Pu-238 Fuel Form Research and Development. The program status, budget information, and milestone information are discussed in each main section. The Work Breakdown Structures (WBS) for this program is outlined. Only one monthly report per year is processed for EDB.
Date: July 18, 1980
Partner: UNT Libraries Government Documents Department

SNAP 19 Viking Program. Bimonthly technical progress report, December 1979-January 1980

Description: Power system performance data for Pioneer 10 and Pioneer Saturn (initially designated Pioneer 11) were monitored through the reporting period. The estimated RTG system net power was 115 watts for Pioneer 10 and 116 watts for Pioneer Saturn. The telemetry signal quality from both spacecraft systems remains satisfactory.
Date: January 1, 1980
Partner: UNT Libraries Government Documents Department

SNAP 19 Viking Program. Bimonthly technical progress report, June-July 1980

Description: Monitoring and evaluation of Viking Lander 1 power system data continued. The RTG series power range as measured at the PCDA was 64 to 66 watts at finroot temperatures between 270/sup 0/F and 310/sup 0/F. Figures show the Mars Lander performance history of Viking 1. These data include both the minimum and maximum data for each of the SOL days plotted to show the range of performance experienced on the Martian surface. Power system performance data for Pioneer 10 and Pioneer Saturn (initially designated Pioneer 11) were monitored through the reporting period and are shown. After adjusting for the telemetry characteristics, the estimated RTG system net power was 114 watts for both, Pioneer 10 and Pioneer Saturn.
Date: January 1, 1980
Partner: UNT Libraries Government Documents Department

SNAP 19 Viking Program. Bimonthly technical progress report, February 1980-March 1980

Description: Viking 1 Lander power system data has not been available during this reporting period, but summary reports indicate no anomalies in performance. Monitoring and evaluation of Viking 2 Lander power system data continued. Temperature data were similar to those 23 months ago, but combined RTG output power was down by 7 watts from the 75 watts recorded in February of 1978. On February 7, 1980, during a scheduled relay transmission the Lander 2 battery voltage dropped below 26.5 volts. With the orbiter attitude control gas supply nearly depleted and the space network stations required for Voyager encounter with Saturn later this year, the final relay from Viking Lander 2 had been scheduled to take place on April 11. The attempt was made but no data were received. Power system performance data for Pioneer 10 and Pioneer Saturn (initially designated Pioneer 11) were monitored. The estimated RTG system net power was 115 watts for both, Pioneer 10 and Pioneer Saturn. The telemetry signal quality from Pioneer Saturn remains excellent. Pioneer 10, for the first time, shows a loss of signal strength.
Date: January 1, 1980
Partner: UNT Libraries Government Documents Department

SNAP 19 Viking Program. Bimonthly technical progress report, October-November 1980

Description: Monitoring of power system performance data for Pioneer 10 and Pioneer Saturn spacecrafts continued through the reporting period. The net power output for either system at the end of October 1980 was 113 watts. Pioneer 10 degradation has been nearly linear at a rate of 0.130 watts/1000 generator hours, while the Pioneer Saturn power degradation is slightly higher at 0.135 watts/1000 generator hours.
Date: December 18, 1980
Partner: UNT Libraries Government Documents Department

Nuclear proliferation and civilian nuclear power. Report of the Nonproliferation Alternative Systems Assessment Program. Volume IX. Reactor and fuel cycle description

Description: The Nonproliferation Alterntive Systems Assessment Program (NASAP) has characterized and assessed various reactor/fuel-cycle systems. Volume IX provides, in summary form, the technical descriptions of the reactor/fuel-cycle systems studied. This includes the status of the system technology, as well as a discussion of the safety, environmental, and licensing needs from a technical perspective. This information was then used in developing the research, development, and demonstration (RD and D) program, including its cost and time frame, to advance the existing technology to the level needed for commercial use. Wherever possible, the cost data are given as ranges to reflect the uncertainties in the estimates.
Date: June 1, 1980
Partner: UNT Libraries Government Documents Department

Analytical and experimental heat transfer and flow-field prediction on a rectangular reentry module

Description: A General Purpose Heat Source (GPHS) has been designed for the purpose of supplying power to a radioisotope thermal generator intended for interplanetary missions. The baseline configuration, nominally 2 in. x 4 in. x 4 in. with sharp edges and corners, is required to survive accidental earth reentry as well as terminal impact velocities. Several problems have been identified relative to survival criteria during reentry. This paper is concerned with the flow field and reentry heating for a broad face-on or side-on reentry orientation. Moreover, the analysis considers convective heat transfer in the absence of roughness or ablation effects during the supersonic/hypersonic regime of reentry. The anaytical results are compared with wind tunnel data. From these studies it was concluded that heat transfer distributions for non-circular shapes ca be obtained for reentry conditions using wind tunnel data for the surface distributions and a stagnation value based on a reference sphere condition. The distributions obtained at a fixed Mach number (M > 1) appear valid over an extended range of Mach numbers. The above required definition of a proper velocity gradient, and definition of an area aspect ratio. Flowfield predictions (inviscid) using the CM2DT program provide a proper definition of pressure and shock characteristics for non-similar (viscous) solutions. (LCL)
Date: February 5, 1980
Creator: Laganelli, A.L.
Partner: UNT Libraries Government Documents Department

Thermoelectric generator testing and RTG degradation mechanisms evaluation. Progress report No. 36

Description: The n-type selenide legs after 15,000 hours continue to show reasonable agreement with the 3M Co. published thermal conductivity data. In the ingradient testing after 16,500 hours the 3 surviving n-legs (out of 5) show serious degradation in power to load. Weight loss and thermoelectricity property measurements on the first samples of material produced by G.E. continue to correspond to the results previously obtained on R.C.A. material from the MHW program. The remaining MHW generator on test, Q1-A, has accumulated 23,679 hours and performance remains stable. The 18 couple modules S/N-1 and -3 previously tested at RCA show no significant change in operation during the current JPL testing. A comparison of LES 8/9 RTG's with an improved version of DEGRA is shown. No changes in the trends of degradation of LES 8 and 9 and the Voyager RTGs have been observed.
Date: July 1, 1980
Creator: Lockwood, A. & Shields, V.
Partner: UNT Libraries Government Documents Department

Fabrication of selenide segmented elements

Description: Processes are described for the fabrication of P- and N-type elements with high-efficiency selenide segments. Bonded hot and cold caps were attached to these elements with techniques based on processes developed in successful TRANSIT and Ring converter programs. An iron barrier was introduced in the segmented P-type element between the (Cu,Ag)/sub 2/Se and (Bi,Sb)/sub 2/Te/sub 3/ layers. This was made necessary by the known degradation in thermoelectric properties of (Bi,Sb)/sub 2/Te/sub 3/ contaminated with copper. Zero current thermal gradient tests of the segmented P-type element show the iron barrier successfully prevents copper contamination of the (Bi,Sb)/sub 2/Te/sub 3/.
Date: March 1, 1980
Creator: Elsner, N.B.; Chin, J. & Reynolds, G.H.
Partner: UNT Libraries Government Documents Department

Optimal thermionic energy conversion with established electrodes for high-temperature topping and process heating

Description: Advantages of thermionic energy conversion (TEC) have been counted and are recounted with emphasis on high-temperature service in coal-combustion products. Efficient, economical, nonpolluting utilization of coal here and now is a critically important national goal. And TEC can augment this capability not only by the often proposed topping of steam power plants but also by higher-temperature topping and process heating. For these applications, applied-research-and-technology (ART) work reveals that optimal TEC with approx. 1000-to approx. 1100 K collectors is possible using well-established tungsten electrodes. Such TEC with 1800 K emitters could approach 26.6% efficiency at 27.4 W/cm/sup 2/ with approx. 1000 K collectors and 21.7% at 22.6 W/cm/sup 2/ with approx. 1100 K collectors. These performances require 1.5- and 1.7-eV collector work functions (not the 1-eV ultimate) with nearly negligible interelectrode losses. Such collectors correspond to tungsten electrode systems in approx. 0.9-to approx. 6-torr cesium pressures with 1600-to-1900 K emitters. Because higher heat-rejection temperatures for TEC allow greater collector work functions, interelectrode-loss reduction becomes an increasingly important target for applications aimed at elevated temperatures. Studies of intragap modifications and new electrodes that will allow better electron emission and collection with lower cesium pressures are among the TEC-ART approaches to reduced interelectrode losses. These solutions will provide very effective TEC to serve directly in coal-combustion products for high-temperature topping and process heating. In turn this will help to use coal-and to use it well.
Date: July 1, 1980
Creator: Morris, J.F.
Partner: UNT Libraries Government Documents Department

High-power laser and arc welding of thorium-doped iridium alloys

Description: The arc and laser weldabilities of two Ir-0.3% W alloys containing 60 and 200 wt ppM Th have been investigated. The Ir-.03% W alloy containing 200 wt ppM Th is severely prone to hot cracking during gas tungsten-arc welding. Weld metal cracking results from the combined effects of heat-affected zone liquation cracking and solidification cracking. Scanning electron microscopic analysis of the fractured surface revealed patches of low-melting eutectic. The cracking is influenced to a great extent by the fusion zone microstructure and thorium content. The alloy has been welded with a continuous-wave high-power CO/sub 2/ laser system with beam power ranging from 5 to 10 kW and welding speeds of 8 to 25 mm/s. Successful laser welds without hot cracking have been obtained in this particular alloy. This is attributable to the highly concentrated heat source available in the laser beam and the refinement in fusion zone microstructure obtained during laser welding. Efforts to refine the fusion zone structure during gas tungsten-arc welding of Ir-0.3 % W alloy containing 60 wt ppM Th were partially successful. Here transverse arc oscillation during gas tungsten-arc welding refines the fusion zone structure to a certain extent. However, microstructural analysis of this alloy's laser welds indicates further refinement in the fusion zone microstructure than in that from the gas tungsten-arc process using arc oscillations. The fusion zone structure of the laser weld is a strong function of welding speed.
Date: May 1, 1980
Creator: David, S.A. & Liu, C.T.
Partner: UNT Libraries Government Documents Department

Application of microfabrication technology to thermionic energy conversion. Progress report No. 1, 1 May-31 October, 1979

Description: In a theoretical and experimental program to evaluate those areas where three-dimensional microfabrication techniques could be important for improving methods of thermionic energy conversion, effort in the first reporting period has been directed toward a theoretical study of microstructures of electrodes for thermionic energy converters. The properties of a cesiated tungsten thermionic energy converter were analyzed with electrode temperatures compatible with a flame-generated heat source (T/sub c/ = 1650/sup 0/K and T/sub a/ = 700/sup 0/K), in order to estimate the efficiency, power production, and appropriate electrode spacing for microfabricated devices. The analysis yielded a maximum efficiency of 16 percent and corresponding electrical power of 11 W/cm/sup 2/, requiring an emission current of 18 A/cm/sup 2/. The study revealed that to attain these parameters, electrode spacing must be approximately 1 ..mu..m, and that such a close-spaced diode with cesiated tungsten electrodes would operate approximately as a vacuum diode. That is, the principal function of the cesium would be to control the work function of the electrode surfaces. Operating at the point of peak efficiency, little space-charge limitation of the emission and little plasma resistance would be produced, because the atom/atom and electron/atom mean free paths would be larger than the interelectrode space.
Date: January 1, 1980
Creator: Brodie, I. & Gates, D.C.
Partner: UNT Libraries Government Documents Department

DOE/JPL Advanced Thermionic Technology Program. Progress report No. 45, October-November-December 1980

Description: The primary long-term goal of the DOE effort is to improve TEC performance to the level that thermionic topping of fossil fuel powerplants becomes technically possible and economically attractive. An intermediate goal is to demonstrate an in-boiler thermionic module in the early 1980's. A short-term goal is the demonstration of the reliability of thermionic operation in a combustion environment. The focus of the JPL program is to develop thermionic conversion technology appropriate for nuclear electric propulsion (NEP) missions. Accomplishments in the DOE program include: (1) continuing stable output from the combustion life test of the one-inch diameter hemispherical silicon carbide diode (Converter No. 239) at an emitter temperature of 1730/sup 0/K for a period of over 4200 hours; (2) construction of four diode module completed; (3) favorable results obtained from TAM combustor-gas turbine system analyses; and (4) obtained a FERP work function of 2.3 eV with the W(100)-O-Zr-C electrode. JPL program accomplishments include: the average minimum barrier index of the last six research diodes built with sublimed molybdenum oxide collectors was 2.0 eV. (WHK)
Date: January 1, 1980
Creator: Available, Not
Partner: UNT Libraries Government Documents Department

Program of thermoelectric generator testing and RTG degradation mechanisms evaluation. Progress report No. 38

Description: The n-type gadolinium selenide legs after 17,500 hours continue to show reasonable agreement with the 3M Co. published thermal conductivity data. Weight loss for both coated and uncoated Si-Ge material produced by G.E. are reported. No significant discrepancies with the results previously obtained on R.C.A. material from the MHW program have been found. Thermal conductivity measurements are also in agreement. The remaining MHW generator on test, Q1-A, has accumulated 26,800 hours and performance remains stable. The performance of the 18 couple modules S/N-1, S/N-2, and S/N-3 to date is summarized. Telemetry data indicate no changes in the trends of degradation of LES 8 and 9 and the Voyager RTGs.
Date: November 1, 1980
Creator: Lockwood, A. & Shields, V.
Partner: UNT Libraries Government Documents Department

Field task proposal/agreement separation and purification of radioisotopes for research

Description: The present purpose of this program is to produce high-purity uranium-234 (99%) and polonium-209 for the scientific community, both Governmental and non-Governmental. In addition, facilities for separation and purification of protactinium-231, thorium-230, and thorium-229 are maintained in stand-by condition for the resumption of these processes when conditions warrant. The uranium-234 isotope is separated from aged plutonium-238 material, purified, and converted to solid U{sub 3}O{sub 8}. This oxide is subsequently shipped to Oak Ridge National Laboratory for distribution through their Isotope Sales Group. The principal use of uranium-234, which is recovered from aged plutonium-238, is in fission detectors used to monitor reactors. Approximately one-third of the total uranium in a fission detector is uranium-234. The other two-thirds is uranium-235. A typical detector might contain 15 mg total uranium. As the neutron flux in the reactor causes fission of the uranium-235 in the detector, it also converts the uranium-234 to uranium-235.
Date: November 20, 1980
Creator: Wilkes, W.R. & Eppley, R.E.
Partner: UNT Libraries Government Documents Department

The feasibility of retrieving nuclear heat sources from orbit with the space shuttle

Description: Spacecraft launched for orbital missions have a finite orbital lifetime. Current estimates for the lifetime of the nine nuclear powered U.S. satellites now in orbit range from 150 years to 10{sup 6} years. Orbital lifetime is determined primarily by altitude, solar activity, and the satellite ballistic coefficient. There is also the potential of collision with other satellites or space debris, which would reduce the lifetime in orbit. These orbiting power sources contain primarily Pu-238 and Pu-239 as the fuel material. Pu-238 has an approximate 87-year half life and so considerable amounts of daughter products are present after a few tens of years. In addition, there are minor but possibly significant amounts of impurity isotopes present with their own decay chains. Radioisotopic heat sources have been designed to evolving criteria since the first launches. Early models were designed to burn up upon reentry. Later designs were designed to reenter intact. After tens or hundreds of years in orbit, the ability of any orbiting heat source to reenter intact and impact while maintaining containment integrity is in doubt. Such ability could only be verified by design to provide protection in the case of early mission failures such as launch aborts, failure to achieve orbit, or the attainment of only a short orbit. With the development of the Space Shuttle there exists the potential ability to recover heat sources in orbit after their missions are completed. Such retrieval could allow the risk of eventual reentry burnup or impact with atmospheric dispersion and subsequent radiation doses to the public to be avoided.
Date: January 1, 1980
Creator: Pyatt, D.W. & Englehart, R.W.
Partner: UNT Libraries Government Documents Department

DOE/JPL advanced thermionic technology program. Progress report No. 42

Description: Progress is reported on the following tasks: (I) surface and plasma investigations, (II) low-temperature converter development, (III) enhanced mode converter experiments, (IV) component hardware development, (V) thermionic power module system studies, (VI) thermionic array module development, (VII) high-temperature converter evaluation, (VIII) advanced converter studies, (IX) postoperational diagnostics, (X) cylindrical converter component development, and (XI) correlation of design interfaces. (WHK)
Date: January 1, 1980
Partner: UNT Libraries Government Documents Department

SNAP 19 Viking Program. Bimonthly technical progress report, April-May 1980

Description: Monitoring and evaluation of Viking Lander 1 power system data continued. The RTG series power range as measured at the PCDA was 65 to 67 watts at finroot temperatures between 280/sup 0/F and 310/sup 0/F. The Mars Lander performance history of Viking 1 include both the minimum and maximum data for each of the SOL days. Final available power system data for Viking Lander 2 are shown. Typical SOL day cycles for mission day 1193 are presented. The RTG series power ranged from 69 to 70 watts at finroot temperatures between 270/sup 0/F and 300/sup 0/F. The Mars Lander performance history for Viking 2 is shown. Power system performance data for Pioneer 10 and Pioneer Saturn (initially designated Pioneer 11) were monitored through the reporting period. After adjusting for the telemetry characteristics, the estimated RTG system net power was 114 watts for both Pioneer 10 and Pioneer Saturn.
Date: January 1, 1980
Partner: UNT Libraries Government Documents Department

Application of microfabrication technology to thermionic energy conversion. Progress report 4, 1 May 1980 to 31 July 1980

Description: Two applications of microfabrication technology to thermionic converters have been investigated theoretically. The first is a novel method of maintaining micron or submicron spacings over large areas (>1 cm/sup 2/), using metals of different expansion coefficients to eliminate the shear stresses on the insulating pillars separating the electrodes. The second uses low-voltage field-emission sources to create ions in a large (approx. 1 mm) interelectrode gap for space charge neutralization. The theoretical results for both these approaches are highly encouraging.
Date: September 5, 1980
Creator: Brodie, I.
Partner: UNT Libraries Government Documents Department

Air oxidation and seawater corrosion of Hastelloy S and Hastelloy C-4

Description: A program is currently under way at the Pacific Northwest Laboratory (PNL) to develop the data and technology needed to permit the licensing of /sup 90/SrF/sub 2/ as a radioisotope heat source fuel for terrestrial applications. The WESF /sup 90/SrF/sub 2/ storage capsule consists of a Hastelloy C-276 inner capsule (2 in. I.D. x 19 in. long) and a 316L stainless steel outer capsule (2-3/8 in. I.D. x 20 in. long). Preliminary experimental tests and theoretical calculations show that the WESF storage capsule is incapable of meeting current licensing requirements for heat sources that are to be used for terrestrial applications. Therefore, the DOE decision was to develop a new heat source design that would retain the existing WESF Hastelloy C-276 inner capsule and replace the current WESF outer capsule with a new outer capsule capable of meeting current licensing requirements. Based on a number of factors, Hastelloy S was selected as the outer capsule material. Hastelloy C-4 was selected as a backup material in case the Hastelloy S had to be rejected for any reason. This report summarizes the results of studies carried out to determine the effects of both air oxidation at heat source operating temperatures and seawater corrosion on the tensile properties of the outer capsule materials.
Date: March 1, 1980
Creator: Fullam, H. T.
Partner: UNT Libraries Government Documents Department

Formation of double sheaths and the J-V characteristics of the obstructed region

Description: The arc drop of the vapor thermionic converter is determined by the difference of sheath heights and the potential difference across the plasma. The J-V characteristics of cesium vapor diodes operating in the ignited mode show a knee corresponding to near optimum power. When the diode is operating in the region above the knee, the dominant contributor to the arc drop is the difference of the sheath heights (i.e., the potential difference across the plasma produces either a very small loss or may, in fact, reverse sign and reduce the arc drop). In this region the power decreases because the increase in output current is usually not able to compensate for the loss of output voltage. When the diode is operating in the region below the knee, the potential difference in the plasma becomes the dominant contributor to the arc drop. For these reasons, the shape of the J-V characteristics below the knee is different from that above the knee. The location of the knee is a good indicator of the maximum power and the maximum efficiency points. Under the fully optimized conditions, the knee also indicates the barrier index of the diode. Therefore, how and where the knee will appear is of great theoretical and practical interest. Some workers in the thermionic field have speculated that the appearance of the knee is due to the formation of the double sheath. However, this study indicates that the formation of the double sheath takes place significantly below the knee. In addition, this study evaluates J-V characteristics in the obstructed region.
Date: June 1, 1980
Creator: Wang, C.C.
Partner: UNT Libraries Government Documents Department