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DOE-HDBK-3010-94
Appendix B; Plutonium Recovery Facility
This initial drying cycle allows the use of lower temperatures in the actual calciner,
thereby producing an oxide that is easier to fluorinate.
Upon completion of the initial drying cycle, the cake is manually placed in the
calciner feed hopper where a screw auger drives it into the cylindrical calcining
vessel. Dry air is passed countercurrently through the calciner, which operates at
approximately 700 F. The internal sheath of the calciner rotates during operation to
ensure even heating. This rotation is driven by a hydraulic unit mounted in the floor
of the glovebox. The auger drives the product plutonium oxide out of the calciner
and through the glovebox wall into the hydrofluorination line.
Due to the flaky nature of the peroxide cake and design difficulties with the air
flowpath within the calciner, the offgas from the unit normally has recoverable
quantities of plutonium even after passing through a baffle separator. Therefore, a
scrubbing column is installed in the line as well. It is a 6-inch-diameter stainless steel
pipe containing 64% nitric acid. The acid is recirculated via an airlift pump and
cooled as necessary via a chilled water heat exchanger. The acid, containing the
dissolved plutonium oxide, is periodically bled from the tank manually. New acid
can be added manually as well.
The acid bled from the scrubber is collected in two stainless steel pencil tanks in the
glovebox. These tanks are equipped with level instrumentation and relief valves that
discharge to a sump in the vessel. A gear pump in the glovebox discharges the vessel
contents to one of the dissolver solution storage tanks through a cartridge filter after a
sample has been drawn from the interior glovebox sampling system to verify
plutonium concentration. The air exhausting from the scrubber goes through a
knockout pot and to the vessel vent system.
The glovebox sump is alarmed, but there is no interlock because liquid enters the
glovebox only by manual opening of valves. The drying unit and the calciner are
both electrically heated and are equipped with high temperature shutdown interlocks.
2.2.2.6.2
H yd roflu orin ation
As noted above, the hydrofluorination unit is physically joined to the calcining unit by
common piping. The auger that drives material through the calcining unit stops at a
dropoff point. At this point, the plutonium oxide is scooped up by a paddle wheel
machined to maintain a physical isolation barrier between the calciner and the
hydrofluorinator. This wheel drops the oxide into a 6-inch-diameter cylinder with a
slow moving stirrer to prevent clumping. The feed auger for the hydrofluorinator is
Page B-44


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