Selection of 3013 Containers for Field Surveillance Page: 10 of 54
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1.1.3 Binning Assumptions
The following conditions are assumed and form the basis for all binning decisions:
" Metal containers without loosely adhering oxide are innocuous, based on historical and
scientific data. 14-15
" Chloride salts and high concentrations of fluoride salts are potentially corrosive to types
304 and 316 stainless steels. 16-17
" Chloride poses greater risk of corrosion than fluoride at the same concentration.18
" Pressurization of containers in the Pressure and Corrosion bin is primarily caused from
radiolysis of water to generate hydrogen gas (other gases may be generated but in minor
amounts relative to hydrogen). 19
" Pressurization of containers in the Pressure bin is due to a combination of factors,
including the radiolysis of water to generate hydrogen gas and the generation of other
gases such as 02, N2, NO2, SO2, CO2, CO, and CH4 (the mechanisms for generation of
these other gases are not well understood but may contribute a substantial percentage of
the total pressure).19
" The amount of water present directly affects the maximum potential pressure in a
container from the radiolysis of water.4
" Containers with less than 0.8 wt% fluoride are assumed not to be in the worst 5% of the
Pressure and Corrosion bin population based on the fluoride level alone.
" Containers with chloride at levels below the prompt gamma detection threshold are
assumed not to be in the worst 5% of the Pressure and Corrosion bin population.
" Containers with high-purity oxide containing less than 0.1 wt% water are assumed not to
be in the worst 5% of the population based on pressure generation.
1.1.4 Determination of Best Available Moisture Measurement
Moisture analysis methods vary in their accuracy to measure moisture exclusive of other effects.
Loss on ignition (LOI) and TGA are generally recognized to be conservative because of
measurement of weight loss of more than the water present. Coupling the TGA analysis with
either FTIR or mass spectroscopy (MS) is more specific to measurement of only the water in the
sample.
LOI and TGA methods measure any weight change to the sample when heated to 1,000 C.
Weight change can be due to loss of water or evaporation of salts or because of the oxidation of
other materials present (e.g., carbon or uranium). The main difference between LOI and TGA is
when the final weight of the sample is measured. For LOI analysis, the sample is weighed at
room temperature (or generally below 100 C), but it is measured at 1,000 C when using TGA
analysis. Readsorption of water during cooling of the LOI samples masks the actual weight loss
of the sample, which is the basis for using a lower 0.05 wt% binning cutoff for the LOI analysis
compared to 0.10 wt% for all other methods.
Because some containers were stored for significant amounts of time between sampling for
moisture analysis and welding into inner containers, weight change (gain) during storage was
interpreted as moisture adsorbed by the material. Where applicable, weight gain during storage is
added to the moisture measurement (from any of the methods) and is used as a better
representation of the moisture in a container than the moisture measurement alone.5
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Larry Peppers, Elizabeth Kelly, James McClard, Gary Friday, Theodore Venetz, and Jerry Stakebade. Selection of 3013 Containers for Field Surveillance, report, January 1, 2007; Los Alamos, New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc888824/m1/10/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.