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Title: Ostwald Ripening and Its Effect on PuO2 Particle Size in Hanford Tank Waste

Abstract

Between 1944 and 1989, the Hanford Site produced 60 percent (54.5 metric tons) of the United States weapons plutonium and produced an additional 12.9 metric tons of fuels-grade plutonium. High activity wastes, including plutonium lost from the separations processes used to isolate the plutonium, were discharged to underground storage tanks during these operations. Plutonium in the Hanford tank farms is estimated to be {approx}700 kg but may be up to {approx}1000 kg. Despite these apparent large quantities, the average plutonium concentration in the {approx}200 million liter tank waste volume is only about 0.003 grams per liter ({approx}0.0002 wt%). The plutonium is largely associated with low solubility metal hydroxide/oxide sludges where its low concentration and intimate mixture with neutron-absorbing elements (e.g., iron) are credited in nuclear criticality safety. However, concerns have been expressed that plutonium, in the form of plutonium hydrous oxide, PuO{sub 2} {center_dot} xH{sub 2}O, could undergo sufficient crystal growth through Ostwald ripening in the alkaline tank waste to potentially be separable from neutron absorbing constituents by settling or sedimentation. It was found that plutonium that entered the alkaline tank waste by precipitation through neutralization from acid solution is initially present as 2- to 3-nm (0.002- to 0.003-{mu}m) scalemore » PuO{sub 2} {center_dot} xH{sub 2}O crystallite particles and grows from that point at exceedingly slow rates, posing no risk to physical segregation. These conclusions are reached by both general considerations of Ostwald ripening and specific observations of the behaviors of PuO{sub 2} and PuO{sub 2} {center_dot} xH{sub 2}O upon aging in alkaline solution.« less

Authors:
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1027695
Report Number(s):
PNNL-20747
TRN: US1105787
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; AGING; CRITICALITY; CRYSTAL GROWTH; IRON; METRICS; MIXTURES; NEUTRONS; PARTICLE SIZE; PLUTONIUM; SAFETY; SEDIMENTATION; SEGREGATION; SLUDGES; SOLUBILITY; STORAGE FACILITIES; TANKS; UNDERGROUND STORAGE; WASTES; WEAPONS; plutonium; tank waste; PuO2; Ostwald ripening; viscosity; plutonium hydrous oxide; alkaline

Citation Formats

Delegard, Calvin H. Ostwald Ripening and Its Effect on PuO2 Particle Size in Hanford Tank Waste. United States: N. p., 2011. Web. doi:10.2172/1027695.
Delegard, Calvin H. Ostwald Ripening and Its Effect on PuO2 Particle Size in Hanford Tank Waste. United States. doi:10.2172/1027695.
Delegard, Calvin H. Thu . "Ostwald Ripening and Its Effect on PuO2 Particle Size in Hanford Tank Waste". United States. doi:10.2172/1027695. https://www.osti.gov/servlets/purl/1027695.
@article{osti_1027695,
title = {Ostwald Ripening and Its Effect on PuO2 Particle Size in Hanford Tank Waste},
author = {Delegard, Calvin H.},
abstractNote = {Between 1944 and 1989, the Hanford Site produced 60 percent (54.5 metric tons) of the United States weapons plutonium and produced an additional 12.9 metric tons of fuels-grade plutonium. High activity wastes, including plutonium lost from the separations processes used to isolate the plutonium, were discharged to underground storage tanks during these operations. Plutonium in the Hanford tank farms is estimated to be {approx}700 kg but may be up to {approx}1000 kg. Despite these apparent large quantities, the average plutonium concentration in the {approx}200 million liter tank waste volume is only about 0.003 grams per liter ({approx}0.0002 wt%). The plutonium is largely associated with low solubility metal hydroxide/oxide sludges where its low concentration and intimate mixture with neutron-absorbing elements (e.g., iron) are credited in nuclear criticality safety. However, concerns have been expressed that plutonium, in the form of plutonium hydrous oxide, PuO{sub 2} {center_dot} xH{sub 2}O, could undergo sufficient crystal growth through Ostwald ripening in the alkaline tank waste to potentially be separable from neutron absorbing constituents by settling or sedimentation. It was found that plutonium that entered the alkaline tank waste by precipitation through neutralization from acid solution is initially present as 2- to 3-nm (0.002- to 0.003-{mu}m) scale PuO{sub 2} {center_dot} xH{sub 2}O crystallite particles and grows from that point at exceedingly slow rates, posing no risk to physical segregation. These conclusions are reached by both general considerations of Ostwald ripening and specific observations of the behaviors of PuO{sub 2} and PuO{sub 2} {center_dot} xH{sub 2}O upon aging in alkaline solution.},
doi = {10.2172/1027695},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2011},
month = {9}
}

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