REMOVAL OF RADIOACTIVE CONTAMINANTS FROM
AQUEOUS LABORATORY WASTES BY CHEMICAL TREATMENT
Joseph A. Drago, Sanitary Engineer
Brown and Caldwell Consulting Engineers
Walnut Creek, California 94596
J. R. Buchholz, Section Leader
Waste Management Group
Los Alamos Scientific Laboratory
Los Alamos, New Mexico 87545
INTRODUCTION
Low-level, aqueous, radioactive wastes generated at the Los Alamos Scientific Laboratory (LASL), Los Alamos, N.M., are collected in an industrial waste sewer system and
delivered to a specified technical area, TA-50, for treatment.   The major radionuclides
present in this waste are 238Pu and 239Pu with some 241 Am,  90Sr and 137Cs.   Typical values for the concentrations of these radionuclides in the raw waste, along with their
half-lives, major decay modes and Concentration Guides (CG's) for water in uncontrolled
areas [ 1 ], are summarized in Table I.   Additional aqueous radioactive wastes are also
generated and treated at the LASL plutonium and uranium processing area at TA-21, but
these wastes are not within the" purview of this paper.
Table I. Major Radionuclides in TA-50 Raw Waste
Concentration (pCi/1)
Major
Typical
Uncontrolled
Radionuclide
tvi (yr)
Decay Mode
TA-50 Waste
Area (CG)
238Pu
87
Alpha
140,000
5,000
239Pu
24,400
Alpha
5,800
5,000
241 Am
458
Alpha
6,000
4,000
90Sr
28
Beta
l,100a
300
I37Cs
30
Beta, Gamma
5,100
20,000
a89Sr-90Sr combined.
The LASL waste management philosophy is to concentrate and contain the radioactivity in liquid wastes so as to produce an effluent with the lowest practicable levels of
radioactivity.   The TA-50 liquid waste treatment plant shown schematically in Figure 1
has been described in detail elsewhere [2,3], and only the liquid treatment train is discussed here.   This train provides a high pH (above 11.0) chemical precipitation-flocculation
process similar to the one first described by Christenson et al. [4].   Cation exchange for
removal of beta-gamma emitters, including 90Sr and l37Cs, is an in-line process for additional treatment.
Raw wastes are received in holding tanks which are sized to handle overnight and weekend flows.   Raw feed is pumped from the waste holding tanks and routed to either or
both of the two chemical treatment trains, which can be operated in parallel (normal
mode) or series, at design rates of 950 1pm and 475 1pm, respectively.  These two treatment trains provide flash mixing of reactant chemicals (2 min), flocculation (40 min) and
sedimentation (2.5 hr) in combined flocculator-clarifier units. A small fraction of the sludge
produced is normally recycled to the flash mixers to aid in the floe formation.
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