Unabated emission source term estimate for the 340-NX stack Page: 4 of 46
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HNF-SD-LEF-ER-002, Rev. 0
UNABATED EMISSION SOURCE TERM ESTIMATE FOR THE 340-NX STACK
EPA regulations (40CFR61, Subpart H) state that continuous air monitoring is
required for a source if the potential emissions can result in a dose to the maximally
exposed offsite individual exceeding 0.1 mrem/year. The objective of this work is to
estimate the air emissions from the 340-NX stack if the filter system was absent or failed.
The concentrations of airborne radionuclides before, during and after a liquid waste
transfer were measured upstream of the 340Building tank ventilation filters. Gross alpha,
gross beta, Co-60 and Cs-137 were present before the transfer and (except for the Co-60)
increased significantly during the transfer operations. Air sampling continued for five days
after the transfer and (except for gross beta) the concentrations generally declined, but not
to the pre-transfer condition. Offsite potential dose estimates were made assuming the
emissions were unabated and occurred at a steady annual rate. The contributions from
gross alpha and Am-241 were the most significant, with a combined potential dose of about
The 340-NX stack is the discharge point for the 340 Building vessel vault ventilation
system. The vessels are steel tanks used for temporary storage of liquid radioactive wastes
from the various facilities in the 300 Area. The liquids are periodically sampled and
transferred to railcars for transport to Tank Farms in the 200 Areas. Propeller type agitators
are used to mix the contents of the vessels when sampling and transferring are being
conducted. The vessel vault air cleaning components include in series a moisture separator
(which use is optional depending on damper alignments) and three filtration trains operated
in parallel. Each train consists of a prefilter, a HEPA filter, a second HEPA filter, and an
activated charcoal filter. It is expected that unabated emissions would be generated during
liquid sampling and transfers or other times when the agitators are used.
The general approach was to collect air samples upstream of the filter trains and with
the moisture separator bypassed. Samples were to be collected during the different
activities that might generate a source term.
The air samples were obtained from the 14-in. diameter duct just upstream from
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Stordeur, R.T. & Glissmeyer, J.A., Fluor Daniel Hanford. Unabated emission source term estimate for the 340-NX stack, report, March 19, 1997; Richland, Washington. (digital.library.unt.edu/ark:/67531/metadc677141/m1/4/: accessed August 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.