Vessel Vent

DOE-HDBK-3010-94

Appendix B; Plutonium Recovery Facility

2.2.2.8 V essel V en t

The vessel vent room is essentially the utility room for the plutonium processing line. It

houses the vessel vent system, the process steam condensate tanks, and the process chilled

A drawing of the vessel vent system is provided as Figure B.15. It consists of a typical

packed column scrubbing system with the flow-driving equipment contained in small

gloveboxes. The purpose of the system is to draw acidic vapors from the tanks to pass them

through a weak caustic solution for neutralization. The scrubbed vapors can then be sent to

the main exhaust plenums without creating potential concerns relating to chemical interaction

with filters.

The vessel vent header in each glovebox is sloped to drain any liquid entering the header into

small knock-out pots. The drain line entering each knock-out pot has its end submerged in a

liquid seal in order to maintain negative pressure in the vessel vent system. Vapors passing

into the header pass through a cyclone separator in the vessel vent room, which disengages

any residual liquid into a 2-foot-diameter knock-out tank filled with borated raschig rings.

The vapor then enters the bottom of a packed bed scrubber, bubbling up through a liquid

sump containing borated raschig rings, and then passes through the main bed of raschig

rings. 15% KOH is flowing downward through the packed bed as the neutralizing medium.

Vapors exit the scrubber through a series of demister pads and are then drawn into the small

blower glovebox where one of two centrifugal blowers sends them to join the main exhaust

ventilation upstream of HEPA filtration.

KOH solution at the bottom of the scrubber is drawn by one of two on-line pumps through a

heat exchanger to the top of the scrubber tower where it is sprayed onto the packed bed.

The small centrifugal pumps used in this system are, like the air blowers, housed in a small

glovebox. The heat exchanger uses process chilled water to prevent heat buildup due to the

exothermic nature of the neutralization reaction. The flow in this loop is periodically

directed to a raschig ring blowdown tank to remove depleted caustic and water generated by

neutralization. This tank and the knock-out tank can be recirculated for sampling or directed

to the liquid waste header leading to the H-8 treatment facility by a small centrifugal pump

located in the pumping glovebox.

Level indication is available for all of the tanks in this system. Temperature indication is

provided for the heat exchanger outlet and the scrubber tower sump. A pH measurement

device is also used to control the rate of blowdown and fresh caustic addition. Although the

drawing provided shows only one system, there are actually two of each tank to allow

maintenance on one tank while the other continues to support operation.

Page B-51