Residue Dissolution - h3010v20173

DOE-HDBK-3010-94

Appendix B; Plutonium Recovery Facility

addition lines, vessel vent connection, and instrumentation support lines. The vent

line is always open, and as a secondary precaution, a weighted plug on the oxide

charging port is designed to blow out below the rated pressure of the vessel.

Level and temperature indication are available for the dissolver vessel. The

temperature signal is used to control the steam inlet valve to the dissolver heating

block mounted on the bottom of the dissolver. It will completely close the valve if

dissolver temperature reaches 206 F. The sump level interlock will shut the air-

operated valves controlling nitric acid flow to the glovebox on high sump level.

Finally, the dissolver vessel itself is continuously checked for plutonium holdup by an

installed monitor.

The in-line filter elements used are 20-m cartridge filters that can be backflushed

with nitric acid or air/nitrogen if desired. The vacuum run tank is identical to the

dissolver vessels. The liquid-to-liquid eductor system, which transfers the product

solution to the accountability tank, mixes 35% nitric acid with the product solution to

dilute it and reduce temperature. Liquid samples are drawn from the accountability

tank by means of a sampling system previously described (section 2.1.5.7). This

system can also take samples from the dissolver vessel. The accountability tank is a

150-liter slab tank. Its instrumentation and piping is similar to that of the dissolver

vessels. After sample analysis in the H-3 lab annex, the solution is transferred by a

small gear pump from this tank to tank #1 or #2 in the tank farm located on the

maintenance side of the wet processing line. There, 35% nitric acid is added to

create a total volume of ≈ 200 liters to reduce plutonium concentration to the range

of 5 - 7 g/l.

2.2.2.2.2

R esid u e D issolu tion

The residue dissolution line is essentially identical to the oxide dissolution line with

one major and one minor exception. The major exception is that material is added to

the stirred dissolver slowly to avoid a process eructation. Residue chunks are poured

into a hopper that supplies material to a screw feed conveyer. The conveyer drops

residue into the solution at a controlled rate via a sealed entry port. The minor

difference between the residue line and the oxide line is that the dissolver and

vacuum run tanks are 20-liter vessels, and the accountability tank is a 125-liter

vessel. Product solution from this line is transferred to tank #3 or #4 in the tank

farm located on the maintenance side of the wet processing line. There, 35% nitric

acid is added, creating a total volume of ≈ 160 liters to reduce plutonium

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