Hydrogen Fluoride Storage and Supply

DOE-HDBK-3010-94

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.

Nitrogen lines penetrate the vessel in three other locations to provide for tank purging

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

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