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Title: Investigation of Effects of Neutron Irradiation on Tantalum Alloys for Radioisotope Power System Applications

Abstract

Tantalum alloys have been used by the U.S. Department of Energy as structural alloys for space nuclear power systems such as Radioisotopic Thermoelectric Generators (RTG) since the 1960s. Tantalum alloys are attractive for high temperature structural applications due to their high melting point, excellent formability, good thermal conductivity, good ductility (even at low temperatures), corrosion resistance, and weldability. A number of tantalum alloys have been developed over the years to increase high-temperature strength (Ta-10%W) and to reduce creep strain (T-111). These tantalum alloys have demonstrated sufficient high-temperature toughness to survive the increasing high pressures of the RTG's operating environment resulting from the alpha decay of the 238-plutonium dioxide fuel. However, 238-plutonium is also a powerful neutron source. Therefore, the RTG operating environment produces large amounts of 3-helium and neutron displacement damage over the 30 year life of the RTG. The literature to date shows that there has been very little work focused on the mechanical properties of irradiated tantalum and tantalum alloys and none at the fluence levels associated with a RTG operating environment. The minimum, reactor related, work that has been reported shows that these alloys tend to follow trends seen in the behavior of other BCC alloys undermore » irradiation. An understanding of these mechanisms is important for the confident extrapolation of mechanical-property trends to the higher doses and gas levels corresponding to actual service lifetimes. When comparing the radiation effects between samples of Ta-10%W and T-111 (Ta-8%W-2%Hf) subjected to identical neutron fluences and environmental conditions at temperatures <0.3Tm ({approx}700 deg. C), evidence suggests the possibility that T-111 will exhibit higher levels of internal damage accumulation and degradation of mechanical properties compared to Ta-10%W.« less

Authors:
;  [1];  [2]
  1. University of Dayton Research Institute, 300 College Park Dayton OH 45469-0102 (United States)
  2. Ohio State University Research Reactor, 1298 Kinnear Road, Columbus, OH 43212 (United States)
Publication Date:
OSTI Identifier:
21054539
Resource Type:
Journal Article
Journal Name:
AIP Conference Proceedings
Additional Journal Information:
Journal Volume: 880; Journal Issue: 1; Conference: International forum-STAIF 2007: 11. conference on thermophysics applications in microgravity; 24. symposium on space nuclear power and propulsion; 5. conference on human/robotic technology and the vision for space exploration; 5. symposium on space colonization; 4. symposium on new frontiers and future concepts, Albuquerque, NM (United States), 11-15 Feb 2007; Other Information: DOI: 10.1063/1.2437459; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-243X
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BCC LATTICES; CORROSION RESISTANCE; CREEP; DUCTILITY; EXTRAPOLATION; HELIUM 3; IRRADIATION; MELTING POINTS; NEUTRON SOURCES; NEUTRONS; PLUTONIUM 238; POWER GENERATION; RADIATION EFFECTS; STRAINS; TANTALUM ALLOYS; THERMAL CONDUCTIVITY; THERMOELECTRIC GENERATORS; WELDABILITY; NESDPS Office of Nuclear Energy Space and Defense Power Systems

Citation Formats

Barklay, Chadwick D, Kramer, Daniel P, and Talnagi, Joseph. Investigation of Effects of Neutron Irradiation on Tantalum Alloys for Radioisotope Power System Applications. United States: N. p., 2007. Web. doi:10.1063/1.2437459.
Barklay, Chadwick D, Kramer, Daniel P, & Talnagi, Joseph. Investigation of Effects of Neutron Irradiation on Tantalum Alloys for Radioisotope Power System Applications. United States. doi:10.1063/1.2437459.
Barklay, Chadwick D, Kramer, Daniel P, and Talnagi, Joseph. Tue . "Investigation of Effects of Neutron Irradiation on Tantalum Alloys for Radioisotope Power System Applications". United States. doi:10.1063/1.2437459.
@article{osti_21054539,
title = {Investigation of Effects of Neutron Irradiation on Tantalum Alloys for Radioisotope Power System Applications},
author = {Barklay, Chadwick D and Kramer, Daniel P and Talnagi, Joseph},
abstractNote = {Tantalum alloys have been used by the U.S. Department of Energy as structural alloys for space nuclear power systems such as Radioisotopic Thermoelectric Generators (RTG) since the 1960s. Tantalum alloys are attractive for high temperature structural applications due to their high melting point, excellent formability, good thermal conductivity, good ductility (even at low temperatures), corrosion resistance, and weldability. A number of tantalum alloys have been developed over the years to increase high-temperature strength (Ta-10%W) and to reduce creep strain (T-111). These tantalum alloys have demonstrated sufficient high-temperature toughness to survive the increasing high pressures of the RTG's operating environment resulting from the alpha decay of the 238-plutonium dioxide fuel. However, 238-plutonium is also a powerful neutron source. Therefore, the RTG operating environment produces large amounts of 3-helium and neutron displacement damage over the 30 year life of the RTG. The literature to date shows that there has been very little work focused on the mechanical properties of irradiated tantalum and tantalum alloys and none at the fluence levels associated with a RTG operating environment. The minimum, reactor related, work that has been reported shows that these alloys tend to follow trends seen in the behavior of other BCC alloys under irradiation. An understanding of these mechanisms is important for the confident extrapolation of mechanical-property trends to the higher doses and gas levels corresponding to actual service lifetimes. When comparing the radiation effects between samples of Ta-10%W and T-111 (Ta-8%W-2%Hf) subjected to identical neutron fluences and environmental conditions at temperatures <0.3Tm ({approx}700 deg. C), evidence suggests the possibility that T-111 will exhibit higher levels of internal damage accumulation and degradation of mechanical properties compared to Ta-10%W.},
doi = {10.1063/1.2437459},
journal = {AIP Conference Proceedings},
issn = {0094-243X},
number = 1,
volume = 880,
place = {United States},
year = {2007},
month = {1}
}