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Title: Physical Property Changes in Plutonium from Accelerated Aging using Pu-238 Enrichment

Abstract

We present changes in volume, immersion density, and tensile properties observed from accelerated aged plutonium alloys. Accelerated alloys (or spiked alloys) are plutonium alloys enriched with approximately 7.5 weight percent of the faster-decaying {sup 238}Pu to accelerate the aging process by approximately 17 times the rate of unaged weapons-grade plutonium. After sixty equivalent years of aging on spiked alloys, the dilatometry shows the samples at 35 C have swelled in volume by 0.15 to 0.17 % and now exhibit a near linear volume increase due to helium in-growth. The immersion density of spiked alloys shows a decrease in density, similar normalized volumetric changes (expansion) for spiked alloys. Tensile tests show increasing yield and engineering ultimate strength as spiked alloys are aged.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
902342
Report Number(s):
UCRL-PROC-226996
TRN: US200717%%264
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: Presented at: Materials Research Society, Boston, United States, Nov 27 - Dec 01, 2006
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; AGING; ALLOYS; DILATOMETRY; HELIUM; PLUTONIUM; PLUTONIUM ALLOYS; TENSILE PROPERTIES; ULTIMATE STRENGTH; NESDPS Office of Nuclear Energy Space and Defense Power Systems

Citation Formats

Chung, B W, Choi, B W, Saw, C K, Thompson, S R, Woods, C H, Hopkins, D J, and Ebbinghaus, B B. Physical Property Changes in Plutonium from Accelerated Aging using Pu-238 Enrichment. United States: N. p., 2006. Web.
Chung, B W, Choi, B W, Saw, C K, Thompson, S R, Woods, C H, Hopkins, D J, & Ebbinghaus, B B. Physical Property Changes in Plutonium from Accelerated Aging using Pu-238 Enrichment. United States.
Chung, B W, Choi, B W, Saw, C K, Thompson, S R, Woods, C H, Hopkins, D J, and Ebbinghaus, B B. Wed . "Physical Property Changes in Plutonium from Accelerated Aging using Pu-238 Enrichment". United States. doi:. https://www.osti.gov/servlets/purl/902342.
@article{osti_902342,
title = {Physical Property Changes in Plutonium from Accelerated Aging using Pu-238 Enrichment},
author = {Chung, B W and Choi, B W and Saw, C K and Thompson, S R and Woods, C H and Hopkins, D J and Ebbinghaus, B B},
abstractNote = {We present changes in volume, immersion density, and tensile properties observed from accelerated aged plutonium alloys. Accelerated alloys (or spiked alloys) are plutonium alloys enriched with approximately 7.5 weight percent of the faster-decaying {sup 238}Pu to accelerate the aging process by approximately 17 times the rate of unaged weapons-grade plutonium. After sixty equivalent years of aging on spiked alloys, the dilatometry shows the samples at 35 C have swelled in volume by 0.15 to 0.17 % and now exhibit a near linear volume increase due to helium in-growth. The immersion density of spiked alloys shows a decrease in density, similar normalized volumetric changes (expansion) for spiked alloys. Tensile tests show increasing yield and engineering ultimate strength as spiked alloys are aged.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Dec 20 00:00:00 EST 2006},
month = {Wed Dec 20 00:00:00 EST 2006}
}

Conference:
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  • We present changes in volume, immersion density, and tensile property observed from accelerated aged plutonium alloys. Accelerated alloys (or spiked alloys) are plutonium alloys enriched with approximately 7.5 weight percent of the faster-decaying {sup 238}Pu to accelerate the aging process by approximately 17 times the rate of un-aged weapons-grade plutonium. After sixty equivalent years of aging on spiked alloys, the dilatometry shows the samples at 35 C have swelled in volume by 0.15 to 0.17 % and now exhibit a near linear volume increase due to helium in-growth. The immersion density of spiked alloys shows decrease in density, similar normalizedmore » volumetric changes (expansion) for spiked alloys. Tensile tests show increasing yield and engineering ultimate strength as spiked alloys are aged. (authors)« less
  • We present dimensional and density changes in an aging plutonium alloy enriched with 7.3 at.% of {sup 238}Pu and reference alloys of various ages. After 45 equivalent years of aging, the enriched alloys at 35 C have swelled in volume by 0.14 to 0.16% and now exhibit a near linear volume increase, without void swelling. Based on X-ray diffraction measurements, the lattice expansion by self-irradiation appears to be the primary cause for dimensional changes during the initial 2-3 years of aging. Following the initial transient, the density change is primarily cause by a constant helium in-growth rate as a resultmore » of {alpha}-particle decay.« less
  • Plutonium, because of its radioactive nature, ages from the ''inside out'' by means of self-irradiation damage and thus produces Frankel-type defects (vacancies and self-interstitial atoms) and defect clusters. The self-irradiation damage in Plutonium-239 occurs mainly by {alpha}-particle decay, where most of the damage comes from the U-235 recoil nucleus. The defects resulting from the residual lattice damage and helium in-growth could result in microstructural and physical property changes. Because these self-irradiation effects would normally require decades to measure, with a fraction (7.5 wt%) of Pu-238 is added to the reference plutonium alloy thus accelerating the aging process by approximately 18more » times the normal rate. By monitoring the properties of the Pu-238 spiked alloy over a period of about 3.5 years, the properties of plutonium in storage can be projected for periods up to about 60 years. This paper presents density and volume changes observed from the immersion density and dilatometry measurements equivalent to aging the reference plutonium alloys to nine years.« less
  • In support of Stockpile Stewardship activities, accelerated aging tests on a plutonium alloy enriched with 7.3 atomic percentage of {sup 238}Pu is underway using dilatometry at 35, 50, and 65 C and immersion density measurements of material stored at 50 C. Changes in density are expected from radiation damage in the lattice and helium in-growth. After twenty-five equivalent years of aging, the dilatometry data shows that the alloys at 35 C have expanded in volume by 0.11% to 0.12% and have started to exhibit a near linear expansion behavior primarily caused by the helium accumulation. The average He-to-vacancy ratio frommore » tested specimens was determined to be around 2.3. The model for the lattice damage and helium in-growth accurately represents the volume swelling at 35 C. The density converted from the dilatometry corresponds well to the decreasing density trend of reference plutonium alloys as a function of time.« less