5    ACTINIDE REMOVAL FROM WASTEWATER APPLYING
WASTE MINIMIZATION TECHNIQUES
James R. Covey, Graduate Research Assistant
William S. Midkiff, Environmental Engineer
Los Alamos National Laboratory, Los Alamos New Mexico 87544
Fernando Cadena, Professor
New Mexico State University, Las Cruces, New Mexico 88003
INTRODUCTION
Approximately 60 tons of iron and lime sludge are being generated annually to remove a quantity of
actinides (atomic numbers from 89 through 103) about the size of a marble. Most of these actinides
consist of plutonium and americium. Through waste characterization, the potential reduction in waste
volume and techniques that may provide this waste reduction can be identified.
BACKGROUND INFORMATION
Los Alamos National Laboratory (LANL) is designing a new $150,000,000 facility to treat the
chemical and radioactive wastes generated throughout the complex. The existing treatment plant is
functional but aging. Increasingly stringent water discharge limits will force innovative process design
concepts to carry the new facility well into the twenty-first century.
The current annual flow into TA-50-1 (treatment plant) is 20 million liters.' The influent averages 70
nanocuries/liter (nCi/L) of gross alpha radiation.' The raw influent is below the minimum limit of 100 nCi/
g required for classification as TRU waste according to DOE Order 5820.2A and is classified as Low-Level
Waste. Current treatment reduces the gross alpha three orders of magnitude; resulting in an effluent activity
of about 50 picocuries/liter (pCi/L). The effluent is discharged into Mortandad Canyon.
REGULATIONS
Radioactive levels in the effluent are regulated by the Derived Concentration Guidelines of DOE Order
5400.5; which allows 30 pCi/L gross alpha for plutonium and americium combined. Chemical concentrations in the effluent discharge are regulated by United States Environmental Protection Agency (EPA)
permit under the National Pollutant Discharge Elimination System (NPDES) established by the Clean
Water Act. LANL waste associated with weapons production is regulated by the Atomic Energy Act and is
therefore exempt from EPA and state regulation. The changing political climate may result in changes in
regulatory authority. LANL discharges may then be regulated by the EPA under 40 CFR 141 & 142 and/or
the New Mexico Environment Department Drinking Water Program.
WASTE SLUDGE PRODUCTION
A major concern at LANL is the large volume of low-level radioactive sludge that is generated by
the current treatment technology. The plant annually produces 200 55-gallon drums of sludge
(approximately 60 tons) during the process of removing only a few grams of radioactive isotopes. If
the principal actinides in the influent could be separated and reduced to pure metallic form, the
annual volume of plutonium would be about the size of a marble and the americium would be about
the size of a BB.
Most of the sludge results from the coagulants, iron and lime, added at the plant at a concentration
of 10,000 parts-per-million (ppm). Waste minimization will be a key design criteria for the new
facility. Records of total suspended solids (TSS) in the influent average about 1000 kg per year
(approximately I ton).' Therefore, the theoretical sludge volume reduction available is near 98Vo.
Research is underway to develop and evaluate technologies that achieve the desired removal efficiency
with a minimum of produced waste volume.
47th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea. Michigan 48118.
Printed in U.S.A.
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