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Appendix B; Plutonium Recovery Facility
2.2.3.4 H yd rogen F lu orid e S torage an d S u p p ly
The HF storage and supply system for H-Plant consists of two major parts. The first is the
storage tank and associated vessels in the external chemical tank farm. The second is the HF
evaporator located on the second floor of the H-1 building.
2.2.3.4.1
H F S torage T an k
A drawing of the HF storage system is provided as Figure B.17. The HF storage tank
is a heavily insulated monel vessel equipped with a level detection system and
temperature and pressure indication. Liquid hydrogen fluoride is transferred out of the
tank by applying a nitrogen overpressure of 75 psig to the system. Double-walled
pipes deliver the liquid to the second floor of the H-1 building.
as necessary. The purge exhaust line ties off the tank relief valve line. It directs
purge flow to a knock-out tank and then into a scrubber filled with 35% KOH. The
plant air main is used to drive a jet pump that accelerates purge flow and provides
good intermixing between the air flow and the scrubbing solution. This simple
scrubber vents directly to the atmosphere.
The tank relief valve is set to lift at 150 psig, a pressure that is not considered
attainable absent a major fire. A pressure sensor in the relief outlet line sounds an
alarm in the H-1 control room when the relief lifts. The gas released when the relief
valve lifts is directed to the main exhaust stack.
2.2.3.4.2
H F E vap orator
The HF evaporator, represented in Figure B.18, is located in a dedicated room on the
south side of the chemical tank farm area. The location allows the unit to be directly
over the dry processing line, which allows gaseous HF to be piped directly to the
hydrofluorinator without having to pass through intervening rooms or corridors.
Liquid HF is piped through the exterior wall of the evaporator room. The evaporator
is a 15-inch diameter cylinder sitting in a water bath on a scale. The scale has been
calibrated both for the weight of the bath and the evaporator vessel so that the weight
of HF can be directly read at all times. The water bath is equipped with a standard
heating element that maintains the bath at approximately 70 F to boil HF. The bath
is recirculated by a small centrifugal pump that directs the water through a heat
exchanger and back to the bath. The chilled water inlet valve to the heat exchanger is
Page B-59
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