HF Scrubbing System

DOE-HDBK-3010-94

Appendix B; Plutonium Recovery Facility

2.2.2.6.3

H F S cru b b in g S ystem

As noted above, the last glovebox in the dry line scrubs the hydrofluorinator offgas.

In this system, 35% KOH is circulated by a small centrifugal pump into a venturi

scrubber, where it is intermixed with the hydrofluorinator offgas. The scrubbed

mixture than passes into a 6-inch-diameter tank, where the offgas bubbles up through

35% KOH and passes on to the vessel vent system.The centrifugal pump takes suction

on this small KOH tank and sends the solution through a chilled water heat exchanger

to remove the heat generated by the neutralization reaction. This liquid then goes

back to the venturi scrubber. Periodically, liquid from the system can be blown down

to scrubber waste tanks #20 and #21 via an air-operated valve.

A pH detector provides remote readout, a low pH alarm, and a low-low signal that

automatically opens the 35% KOH supply line. The level detector that controls the

liquid outlet line from the collection tank will also override the PH signal to the

supply line if tank level is too high. A temperature sensor in the collection tank also

provides control input to the chilled water inlet valve on the heat exchanger. This

glovebox is the only one in the dry line equipped with a sump and associated level

alarms and interlocks.

2.2.2.7 R ed u ction L in e

Plutonium fluoride powder is received in the reduction line via a chainveyor from the

hydrofluorination glovebox. There is a limited storage area with two storage spaces available

in a rack, but the normal practice is to begin the reduction procedure as soon as plutonium

fluoride is received for two main reasons. The first is, again, the desire to keep plutonium

fluorides in line for as limited a time as possible from an ALARA perspective. The second

is to keep the material dry so that moisture-induced pressure rises do not occur in the actual

metal formation step. The reduction line is inerted, but standard procedure is that plutonium

fluoride cannot be left cumulatively standing in the hydrofluorinator glovebox and the

reduction line more than 24 hours and then used in the process. It must be heated in an

argon atmosphere in a small muffle furnace in the reduction line and resampled before it can

be used in the process.

The reduction process is schematically represented in Figure B.14. The first step in the

reduction procedure is to use one of the two balances in the line to prepare a plutonium

fluoride charge. The load cell, like all of the load cells used in H-Plant, is a basic pressure-

sensitive transducer with digital readout of weight in grams. The plutonium fluoride charge

container is then placed in a slightly recessed well in the glovebox floor near the preparation

station.

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