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Title: Interim Report on Development of a Model to Predict Dissolution Behavior of the Titanate Waste Form in a Repository

Abstract

Dissolution testing performed to date on a titanate waste form under development for plutonium immobilization reveals the following: (1) The wasteform is very durable. Many of the test results have shown the dissolution rate to be below detection or less than background levels of the constituent elements; (2) elemental release is non-stoichiometric with Pu, U, Ca, and Gd released faster than Ti and Hf at most pH conditions; (3) dissolution rates measured in flow-through tests sometimes show a continuous decrease with time in tests of up to two years duration; (4) attempts to model the dissolution as a transport-controlled process with diffusion through a leached layer as the rate limiting mechanism show reasonable agreement at low pH conditions but poor agreement at neutral to alkaline pHs. Based on present uncertainties in our understanding of rate control, we have provided conservative estimates of radionuclide release rates based on the fastest observed release rates measured in short-term tests. These dissolution rates under repository-relevant conditions are in the range of 10{sup -3} to 10{sup -6}g/m{sup 2}/day.

Authors:
Publication Date:
Research Org.:
Lawrence Livermore National Lab., CA (US)
Sponsoring Org.:
USDOE Office of Defense Programs (DP) (US)
OSTI Identifier:
792651
Report Number(s):
UCRL-ID-135363
TRN: US0301517
DOE Contract Number:  
W-7405-Eng-48
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 16 Aug 1999
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 54 ENVIRONMENTAL SCIENCES; DETECTION; DIFFUSION; DISSOLUTION; PLUTONIUM; RADIOISOTOPES; TESTING; TITANATES; WASTE FORMS

Citation Formats

Bourcier, W L. Interim Report on Development of a Model to Predict Dissolution Behavior of the Titanate Waste Form in a Repository. United States: N. p., 1999. Web. doi:10.2172/792651.
Bourcier, W L. Interim Report on Development of a Model to Predict Dissolution Behavior of the Titanate Waste Form in a Repository. United States. doi:10.2172/792651.
Bourcier, W L. Mon . "Interim Report on Development of a Model to Predict Dissolution Behavior of the Titanate Waste Form in a Repository". United States. doi:10.2172/792651. https://www.osti.gov/servlets/purl/792651.
@article{osti_792651,
title = {Interim Report on Development of a Model to Predict Dissolution Behavior of the Titanate Waste Form in a Repository},
author = {Bourcier, W L},
abstractNote = {Dissolution testing performed to date on a titanate waste form under development for plutonium immobilization reveals the following: (1) The wasteform is very durable. Many of the test results have shown the dissolution rate to be below detection or less than background levels of the constituent elements; (2) elemental release is non-stoichiometric with Pu, U, Ca, and Gd released faster than Ti and Hf at most pH conditions; (3) dissolution rates measured in flow-through tests sometimes show a continuous decrease with time in tests of up to two years duration; (4) attempts to model the dissolution as a transport-controlled process with diffusion through a leached layer as the rate limiting mechanism show reasonable agreement at low pH conditions but poor agreement at neutral to alkaline pHs. Based on present uncertainties in our understanding of rate control, we have provided conservative estimates of radionuclide release rates based on the fastest observed release rates measured in short-term tests. These dissolution rates under repository-relevant conditions are in the range of 10{sup -3} to 10{sup -6}g/m{sup 2}/day.},
doi = {10.2172/792651},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1999},
month = {8}
}

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