High Temperature Compatibility of 60-Watt IHS Materials

Technical Report · Tue Nov 21 00:00:00 EST 1995

DOI:https://doi.org/10.2172/1123675· OSTI ID:1123675

Worley, C. M. ^[1]; Merten, C. W. ^[1]

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1. Mound Engineering & Analysis Group, Inc.

The 60-Watt Isotopic Heat Source (IHS) utilizes a variety of materials which have been selected for their properties at elevated temperatures. These include iridium, molybdenum, and the T-111 alloy which consists of 90 wt% tantalum, 8 wt% tungsten, and 2 wt% hafnium. Properties of interest in radioisotopic heat source applications include high temperature strength, resistance to oxidation, weldability, and ability to act as a diffusion barrier. Iridium is utilized as a clad for fuel pellets because of its high temperature mechanical properties and good compatibility with carbon and plutonium oxide. Molybdenum retains good high temperature strength and has been used as a diffusion barrier in past applications. However, molybdenum also exhibits poor resistance to oxidation. Therefore, it is necessary to enclose molybdenum components so that they are not exposed to the atmosphere. T-111 exhibits moderate oxidation resistance, good high temperature mechanical properties, and good weldability. For these reasons, it is used as the outer containment boundary for the 60-Watt IHS. Because the temperature in GPHS fueled dads is on the order of 1000 degrees Celsius in the 60-W configuration, the potential for diffusion of dissimilar materials from one into another exists. Deleterious effects of diffusion can include degradation of mechanical strength through the formation of brittle intermetallics, degradation of mechanical properties through simple alloying, or formation of voids through the Kirkendall effect. Because of the possibility of these effects, design methodology calls for use of diffusion barriers between materials likely to exhibit interdiffusion at elevated temperatures. The necessity to assure the long term integrity of the 60-Watt IHS dictates that the diffusion behavior of its component materials be known. This report describes the high temperature compatibility studies which were conducted on the component materials of the 60-Watt IHS.

• Research Organization: EG&G Mound Applied Technologies
• Sponsoring Organization: USDOE
• DOE Contract Number: DE-AC04-88-DP43495
• OSTI ID: 1123675
• Resource Relation: Related Information: File Folder: Haupt H.8; STI input by OSTI for NE-75/SDPS
• Country of Publication: United States
• Language: English

Related Subjects

07 ISOTOPE AND RADIATION SOURCES
36 MATERIALS SCIENCE
TUNGSTEN ALLOYS
HAFNIUM ALLOYS
RADIOISOTOPE HEAT SOURCES
CLADDING
IRIDIUM
MOLYBDENUM
WELDABILITY
TEMPERATURE RANGE 0400-1000 K
DATA
MECHANICAL PROPERTIES
COMPATIBILITY
NESDPS Office of Nuclear Energy Space and Defense Power Systems
tantalum alloy (T11)
tungsten alloys
hafnium alloys
radioisotope heat sources
isotopic heat sources
cladding
iridium
molybdenum
oxidation resistance
weldability
high temperature
diffusivity
data
mechanical properties
compatibility