Peroxide Precipitation

DOE-HDBK-3010-94

Appendix B; Plutonium Recovery Facility

The evaporators are equipped with a level, temperature, and pressure indication.

Flow indication is available for all streams, as is temperature indication for exiting

streams. Level indication is used to automatically control the feed inlet valve.

Temperature indication controls the steam inlet valve, and is backed up by an

automatic shutoff of the valve for high pressure. The evaporator column is also

equipped with a pressure relief valve that lifts at 10 psig and leads to the glovebox

sump. It initiates an alarm upon lifting. The pencil tanks are also equipped with

relief valves leading to the glovebox sump. As in other liquid lines, the sump level

interlock stops major chemical and feed addition to the glovebox.

2.2.2.5.3

P eroxid e P recip itation

A simple schematic of the peroxide precipitation system is provided as Figure B.11.

After chemical adjustment as required, the precipitate feed is drawn from tank farm

vessels #13 and #14 by a gear pump and sent to the peroxide precipitation vessel.

Initially, the solution transfer to the precipitation vessel is as a single batch. A

commercial packaged refrigeration unit provides a source of chilled water that

circulates through coils located within the vessel. The precipitation vessels are

constructed of Pyrex and maintained at approximately 60 F to suppress peroxide

decomposition.

When the desired temperature has been obtained, a batch addition of 35% hydrogen

peroxide is made to the precipitation vessel. As the peroxide precipitate forms, a

slurry develops that cascades over into a digestion vessel that is also maintained at

approximately 60 F. Hydrogen peroxide is added to the digestion vessel almost to

the point at which liquid will overflow from the digester to the rotary drum filter.

When a distinct separation has occurred between liquid and precipitate in the digester,

indicating a stable condition, the liquid is vacuum-drawn through the drum filter, and

nitrate solution and peroxide addition begins at a continuous rate.

The reaction is completed in the digestion vessel, and the final slurry cascades over

into the vacuum drum filter. Liquid is drawn through the filter media to the drum

center by a vacuum, leaving the peroxide precipitate cake on the filter media. As the

drum revolves, the cake is washed by a dilute nitric acid spray and then cut off the

media by a fixed horizontal knife known as a doctor blade. The peroxide cake falls

off into a storage container mounted on a load cell. When full, the container is

replaced on the load cell, sealed, and sent by chainveyor to the calcination line.

Filtrate from the drum is collected in a slab tank and transferred to the evaporation

line. The slab tank and the precipitation vessels are steel mesh, reinforced Pyrex

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