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Title: Formation, characterization, and stability of plutonium (IV) colloid; A progress report

Abstract

Plutonium is expected to be a major component of the waste element package in any high-level nuclear waste repository. Plutonium(IV) is known to form colloids under chemical conditions similar to those found in typical groundwaters. In the event of a breach of a repository, these colloids represent a source of radionuclide transport to the far-field environment, in parallel with the transport of dissolved waste element species. In addition, the colloids may decompose or disaggregate into soluble ionic species. Thus, colloids represent an additional term in determining waste element solubility limits. A thorough characterization of the physical and chemical properties of these colloids under relevant conditions is essential to assess the concentration limits and transport mechanisms for the waste elements at the proposed Yucca Mountain Repository site. This report is concerned primarily with recent results obtained by the Yucca Mountain Project (YMP) Solubility Determination Task pertaining to the characterization of the structural and chemical properties of Pu(IV) colloid. Important results will be presented which provides further evidence that colloidal plutonium(IV) is structurally similar to plutonium dioxide and that colloidal plutonium(IV) is electrochemically reactive. 13 refs., 7 figs.

Authors:
; ; ;
Publication Date:
Research Org.:
Los Alamos National Lab., NM (United States); Los Alamos National Lab., NM (USA)
OSTI Identifier:
137514
Report Number(s):
LA-UR-89-2541; CONF-890928-1
ON: DE89015288; TRN: 89:024253
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Conference
Resource Relation:
Conference: Nuclear waste isolation in the unsaturated zone: FOCUS `89, Las Vegas, NV (United States), 18-21 Sep 1989; Other Information: PBD: 1989
Country of Publication:
United States
Language:
English
Subject:
05 NUCLEAR FUELS; HIGH-LEVEL RADIOACTIVE WASTES; UNDERGROUND DISPOSAL; COLLOIDS; PRODUCTION; RADIOACTIVE WASTE MANAGEMENT; YUCCA MOUNTAIN; GROUND WATER; SITE CHARACTERIZATION; PLUTONIUM; PH VALUE; Yucca Mountain Project

Citation Formats

Hobart, D.E., Morris, D.E., Palmer, P.D., and Newton, T.W. Formation, characterization, and stability of plutonium (IV) colloid; A progress report. United States: N. p., 1989. Web.
Hobart, D.E., Morris, D.E., Palmer, P.D., & Newton, T.W. Formation, characterization, and stability of plutonium (IV) colloid; A progress report. United States.
Hobart, D.E., Morris, D.E., Palmer, P.D., and Newton, T.W. Tue . "Formation, characterization, and stability of plutonium (IV) colloid; A progress report". United States. doi:. https://www.osti.gov/servlets/purl/137514.
@article{osti_137514,
title = {Formation, characterization, and stability of plutonium (IV) colloid; A progress report},
author = {Hobart, D.E. and Morris, D.E. and Palmer, P.D. and Newton, T.W.},
abstractNote = {Plutonium is expected to be a major component of the waste element package in any high-level nuclear waste repository. Plutonium(IV) is known to form colloids under chemical conditions similar to those found in typical groundwaters. In the event of a breach of a repository, these colloids represent a source of radionuclide transport to the far-field environment, in parallel with the transport of dissolved waste element species. In addition, the colloids may decompose or disaggregate into soluble ionic species. Thus, colloids represent an additional term in determining waste element solubility limits. A thorough characterization of the physical and chemical properties of these colloids under relevant conditions is essential to assess the concentration limits and transport mechanisms for the waste elements at the proposed Yucca Mountain Repository site. This report is concerned primarily with recent results obtained by the Yucca Mountain Project (YMP) Solubility Determination Task pertaining to the characterization of the structural and chemical properties of Pu(IV) colloid. Important results will be presented which provides further evidence that colloidal plutonium(IV) is structurally similar to plutonium dioxide and that colloidal plutonium(IV) is electrochemically reactive. 13 refs., 7 figs.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Aug 01 00:00:00 EDT 1989},
month = {Tue Aug 01 00:00:00 EDT 1989}
}

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  • We describe concentration changes caused by chemical and alpha-induced radiolytic reactions in various oxidation state pure solutions of Pu(VI), Pu(V), or Pu(IV) colloid or mixtures of these oxidation states at pH values > 1 for a period of nearly two years. The rates of approach to steady-states and the resulting experimental concentration quotient values were determined in order to find the conditions under which equilibrium in 2PuO{sub 2}{sup +} + PuO{sub 2}{sup 2+} + PuO/sub 2(coll)/ reaction might be attained and to learn about the underlying reactions. Computer calculations were used to compare the data with the results required frommore » proposed reaction schemes.« less
  • The effects of alpha-particle self-irradiation have been investigated in solutions of {sup 239}Pu in the pH range from 1.3 to > 2.2. The initial solutions contained Pu(VI), Pu(V), colloidal Pu(IV) or various mixtures of these. Composition versus time was determined for periods up to 618 days. Colloidal Pu(IV) formed slowly in mixtures with initial average oxidation states greater than about 4.5. Colloidal Pu(IV) reacts slowly to give mixtures of Pu(V) and Pu(VI). The two most important reactions in the system appear to be: the disproportionation of Pu(V) to give Pu(VI) and colloidal Pu(IV), and the alpha-particle induced reduction of Pu(VI)more » to give Pu(V). Steady-states were reached very slowly and required at least 400 days for most of the mixtures. No evidence was found for equilibrium in the disproportionation reaction. 20 refs., 4 figs., 3 tabs.« less
  • The objective of this research is to explore the feasibility of using small metal colloids, in microemulsions, as catalysts. The product of this work will be a new concept for tailoring highly dispersed materials to specific catalytic reactions. The knowledge gained from the proposed research will be broadly applicable to variety of reactions, including hydrogenation, synthesis gas conversion, and hydrogen conversion. To achieve this objective, a plan has been formulated to prepare and characterize catalyst particles in organic solvents and to explore the use of catalyst particles. In this paper, we will discuss the use of inverse micelles to solubilizemore » significant quantities of metal compounds in hydrocarbon solvents and their reduction, decomposition, and sulfidation to give colloidal catalytic materials. We will also discuss in detail the characterization of these materials, present preliminary results for the catalytic hydropyrolysis of coals, and discuss the results of our evaluation of selected metal colloids in catalytic hydrogenation of pyrene. 9 refs., 3 tabs.« less
  • In the presentation ''A Study of the Stability and Characterization of Plutonium Dioxide'', the authors discuss their recent work on actinide stabilities and characterization, in particular, plutonium dioxide PuO{sub 2}. Earlier studies have indicated that PuO{sub 2} has the fluorite structure of CaF{sub 2} and typical oxide semiconductor properties. However, detailed results on the bulk electronic structure of this important actinide oxide have not been available. The authors have used all-electron, full potential linear combinations Gaussian type orbitals fitting function (LCGTO-FF) method to study PuO{sub 2}. The LCGTO-FF technique characterized by its use of three independent GTO basis sets tomore » expand the orbitals, charge density, and exchange-correlation integral kernels. Results will be presented on zero pressure using both the Hedin-Lundquist local density approximation (LDA) model or the Perdew-Wang generalized gradient approximation (GGA) model. Possibilities of different characterizations of PuO{sub 2} will be explored. The paper ''Chemical Characterization Rocky Flats and Los Alamos Plutonium-Containing Incinerator Ash'' describes the results of a comprehensive study of the chemical characteristics of virgin, calcined and fluorinated incinerator ash produced at the Rocky Flats Plant and at the Los Alamos National Laboratory prior to 1988. The Rocky Flats and Los Alamos virgin, calcined, and fluorinated ashes were also dissolved using standard nitrate dissolution chemistry. Corresponding chemical evaluations were preformed on the resultant ash heel and the results compared with those of the virgin ash. Fluorination studies using FT spectroscopy as a diagnostic tool were also performed to evaluate the chemistry of phosphorus, sulfur, carbon, and silicon containing species in the ash. The distribution of plutonium and other chemical elements with the virgin ash, ash heel, fluorinated ash, and fluorinated ash heel particulates were studied in detail using microprobe analysis. Some of the more interesting results of these investigations are presented.« less