Hydrofluorination cont'd

DOE-HDBK-3010-94

Appendix B; Plutonium Recovery Facility

located at the bottom of this cylinder. The cylinder is sized sufficiently to allow for

holdup during a product run to account for the shorter residence time of the calciner.

Normally, however, a significant portion of the lag space is not used as the calciner is

simply fed at less than its full capacity rate.

A drawing of the hydrofluorination system is provided as Figure B.13. The rotary

tube hydrofluorinator provides high temperature contact between the plutonium oxide

generated in the calciner and a counter-current stream of hydrogen fluoride gas in dry

air to generate plutonium fluoride. The reaction occurs in two zones within the unit,

the first of which is heated to approximately 750 F and the second to approximately

1100 F. Fluorinated product passes through a breech seal and is deposited via high

temperature isolation valves into a 6-inch-diameter metal product chamber. The

chamber is isolated from the hydrofluorinator, and an outlet valve to the metal

chamber is opened. Product flows out with the assistance of a dry air purge and is

deposited in a container on a load cell. The container is manually placed in a

chainveyor for transfer to the button reduction line.

The offgas from the hydrofluorinator contains sufficient HF gas that, if left untreated,

it could cause a severe corrosion problem in ducting. As a result, the offgas from the

unit passes into the final glovebox in the dry line where a caustic scrubbing system

neutralizes the offgas before passing it on to the vessel vent system.

The hydrofluorination line is heavily shielded due to the high-neutron density

associated with the interaction between alpha particles from the plutonium and

fluorine. The dry line operating and maintenance rooms are segregated into two

halves by shielding walls, which separate the calciner from the hydrofluorinator. The

hydrofluorination glovebox itself is covered by a Benelex wall with sliding cabinet

doors over the windows and gloveports. A second Benelex wall several feet from the

cabinet further compartmentalizes the operating room. Operators normally enter the

inner compartment and access the glovebox windows only to load product containers

and place them into the chainveyor.

The hydrofluorinator system is designed to run with minimal operator supervision.

The valves for loading product are remote-controlled air-operated valves, and a

remote readout for the load cell is provided as well. The rotary unit in the

hydrofluorinator is motor driven instead of hydraulically driven to reduce maintenance

requirements. Fluorine detectors in the exhaust ventilation and in the operating rooms

are designed to shut the air-operated HF inlet line and turn off the hydrofluorinator if

2 ppm of HF is detected.

Page B-45