Processing of uranyl nitrate hexahydrate (UNH) at DOE`s Fernald Site: Success and pitfalls Page: 4 of 11
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The old UNH piping network was not used because it was so intricate that it was
difficult to determine where UNH would exit the system. To improve process
control, reduce the possibility of leaks, and removed the possibility of sending
UNH to an unintended destination, a new stainless steel transfer piping system
was installed to transfer UNH from individual storage tanks to the
dilution/neutralization tanks. Carbon steel piping was used to transfer the
neutralized liquids to the EIMCO, filter, which removed the precipitated uranium
from the neutralized liquids. All flange connections on piping, valves, and
pumps were located within either permanent or temporary secondary containment.
An extensive maintenance repair program was performed on all reused equipment and
the operational readiness of all equipment was verified by a SOT.
The UNH material was transferred from the storage tanks to an agitated processing
tank and diluted with water, if necessary, to adjust the acid normality to < 1
and the uranium content to < 100 g/l. Magnesium hydroxide was then pumped into
the process tank to neutralize the nitric acid and to precipitate out the uranium
and heavy metals. After precipitation was completed, a uranium concentration <
48 ppm and a pH > 6 was verified before the neutralized UNH, magnesium diurnate
(MDU), was pumped to the Plant 8 Wastewater Treatment System (WWTS) for
filtration. In Plant 8, the MDU was filtered through an EIMCOTM filter, a rotary
drum vacuum filter. The resulting filter cake was placed into 55-gallon drums
and sampled to verify that the material passed-TCLP and met the Waste Acceptance
Criteria (WAC) for disposal at'the Nevada Test Site (NTS). The filtrate
contained nitrates, which were removed by the FEMP biodenitrification system and
.discharged in accordance with the FEMP National Pollution Discharge Elimination
System (NPDES) permit.
A Readiness Assessment (RA), performed in accordance with DOE Order 5480.31,
verified that the UNH Neutralization Project was ready to begin in-situ
neutralization with Magnesium Oxide (MgO) on March 24, 1995. This date met the
DF&O startup requirement. Screening criteria were developed to select UNH tanks
that could be neutralized in place, without transferring UNH to a processing
tank. The UNH had to have a uranium concentration < 100 g/l, a Normality < 3,
and the selected tank had to have an operational agitator. The in-situ
neutralization process involved dumping a few bags of MgO each day and agitating
the tanks for several hours each day until neutralization and precipitation were
ENGINEERING PROBLEMS - CORRECTIVE ACTIONS
From January 1995 through March 1995, the UNH Neutralization Project focused on
the following activities:
- Ultrasonic Testing (UT) of the stainless steel pipe welds and
internal visual inspection of the welds for the carbon steel pipe,
to verify that the piping was acceptable to transfer UNH from
storage tanks to the processing tank and to transfer the neutralized
UNH from Plant 2/3 to the Plant 8 WWTS for filtration;
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Luken, D.W.; Brettschneider, D.J.; Heck, R.P. III & White, C.A. Processing of uranyl nitrate hexahydrate (UNH) at DOE`s Fernald Site: Success and pitfalls, article, February 1, 1996; United States. (https://digital.library.unt.edu/ark:/67531/metadc669651/m1/4/: accessed April 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.