Pollution Prevention Wipe Application Study Page: 4 of 21
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Sandia National Laboratories (SNL) and the Amarillo, "Pantex Plant" have teamed on a pollution prevention project
to identify suitable replacement solvent(s) for nuclear weapons maintenance operations. Field weapons maintenance
is currently performed using solvents (e.g. acetone, toluene, MEK, alcohols, etc.) that are classified as Resource
Conservation and Recovery Act (RCRA) materials. These solvents are used with hand wipes to clean weapon
surfaces prior to O-ring replacement, to remove decals for new labeling, to clean painted surfaces prior to
reconditioning, and for other general maintenance purposes. The EPA has assigned four characteristics as the
criteria for determining whether a material should be identified as hazardous under RCRA: Ignitability, Corrosivity,
Reactivity and Toxicity. In some cases, low level radioactive contamination from weapon surfaces necessitates that
the RCRA solvent-containing wipes used during the maintenance operations be classified as mixed waste. To avoid
using RCRA materials, cleaning candidates were sought with a flashpoint greater than 140 F, a pH between 2.5 and
12.5, and did not fail the reactivity and toxicity criteria.
The primary goal of the project is to reduce and/or eliminate mixed waste streams for the DOE weapons complex
and DoD in DOE-directed nuclear maintenance applications. A significant cost savings can be realized if this goal
is achieved. Disposal of mixed waste is significantly more expensive than the disposal of radioactive waste alone.
The DOE complex-wide potential estimated savings are 1370 cubic meters of mixed waste and 457,000 kg of
hazardous waste. This equivocates to estimated cost savings of $16M. Although DoD's waste is smaller, the waste
is relatively more expensive per unit volume because it is generated in smaller quantities at many different sites.
This waste cannot then be consolidated into a larger mixed waste depository due to state laws governing shipment of
RCRA-regulated hazardous waste. The Air Force estimates potential annual savings of over $300K and the Navy's
estimates are on the order of $150K. The total expected annual savings to the government are $16M for the DOE
and $450K for the DoD, for a total of 6.45M.'
The major tasks of this study included: 1) cleaning efficacy tests, so that the candidate cleaner(s) selected "cleaned
as well as or better than" the existing baseline cleaners, 2) corrosivity effects of the cleaners on the various metal
alloys of interest, 3) compatibility effects of organic materials, 4) accelerated aging studies and 5) ES&H issues
associated with the cleaners.
1. Cleaning Efficacy Study - For the purpose of this study and for ease of analysis, 38.1 mm OD, 16 RMS 6061
aluminum (Al) and 304 stainless steel (SS) discs were utilized. For statistical purposes, five samples per condition
were analyzed. In order to obtain an initial uniform surface, the discs were first precleaned using an n-propyl
bromide based cleaner, a.k.a. Nu Tri Clean followed by an isopropyl alcohol rinse (IPA). It was determined in an
earlier study that precleaning with Nu Tri Clean was comparable to cleaning with trichloroethylene (TCE). This in
effect eliminated residual chlorides as a variable in the process. After the discs were precleaned, a contaminant in
the amount of 0.2 cc was applied to the disc. The contaminant was allowed to dry for 1/2 hour before it was wiped
clean. Each disc was then wiped a total of three times using wipes furnished by the Amarillo, "Pantex Plant". Three
methods were used to determine cleanliness levels. Goniometer/Contact angle measurements and MESERAN
analyses were performed at SNL. X-ray photoelectron and Auger electron spectroscopy was performed at the
Amarillo, "Pantex Plant".
A Rame Hart Model 100 Contact Angle (CA) Goniometer was used to determine surface cleanliness. The test
measures the contact (tangent) angle that is formed between a drop of water and its supporting surface. The method
is a relative measurement of surface wettability. In general, the cleaner and less oxidized a surface, the lower the
CA measurement. The CA measurement is a qualitative test that is used as an initial screening tool.
A MESERAN Surface Analyzer was the second analytical method for determining quantitative measurement of
microorganic residues to nanogram/cm2 levels using a slope technique. The MESERAN is a non-destructive test
method available for in process organic contamination detection and measurement.2 Its measurement is based on
Evaporative Rate Analysis technology. The technique measures the rate of evaporation of a carbon-14 tagged
radioactive chemical with a Geiger counter. The optimal slope of the log count versus time evaporation curve,
expressed as a positive integer, is a valid inverse measure of the amount of residue, i.e., the higher the slope the less
the residue.3 Calibration curves have been established for common organic contaminants and can be used to convert
slope values to contamination levels in nanograms/cm.
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Lopez, E.P.; Modderman, W.E. & Montoya, M.G. Pollution Prevention Wipe Application Study, article, February 10, 1999; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc688931/m1/4/: accessed December 16, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.