Resin Exotherm cont'd

DOE-HDBK-3010-94

7.0 Application Examples; Liquid Storage and Ion Exchange Examples

washing cycle, the resin remains fully loaded while the clean wash solution picks up

only trace quantities of plutonium. Over the course of the elution cycle, the loading

process is reversed as the plutonium in the resin beds is reduced to trace holdup once

again, and the clean elution solution reaches a plutonium concentration of 50 - 60 g/l

as it exits the last ion exchange unit.

The maximum amount of plutonium on the solid resin is 6500 g if an exotherm has

been postulated after completion of a loading cycle. The potential variability in this

number is solely a function of how much material is processed and where in the

loading or eluting cycle the process is. The amount of material that could be in

solution is fundamentally dependent on which operation is occurring. For the wash

cycle, there will be essentially no plutonium in solution. The amount of plutonium in

solution must be estimated for the loading and elution cycles.

Each ion exchange unit is a 5.5-foot tall column with a 6-inch diameter, having a total

volume of 30.6 liters and a resin bed volume of 23.9 l. A conservative estimate of

the void volume of the resin bed is 50%, in which case a total of 19 liters of liquid

may be present in one column. The liquid is distributed as 3.7 l in the top void space

of the column, 11.6 l in the resin bed, and 3.7 l in the bottom void space of the

column.

Loading cycle feed solution enters the top of ion exchange column 1 at a

concentration of 7 g/l, and exits through the bottom of the column. The reduced

concentration solution then enters the top of ion exchange column 2, and exits through

the bottom as a solution normally containing only waste concentrations of plutonium.

Ion exchange column 3 serves only to capture plutonium if something has gone wrong

with the absorption process in the first two columns, such as depletion of resin bed

capability. The process is reversed for elution. Clean 4% nitric acid flows into the

top of ion exchange column 3, and exits through the bottom of the column. It then

flows to the top of ion exchange column 2 and then to the top of ion exchange

column 1, before exiting from the glovebox as a concentrated plutonium solution.

The maximum mathematical estimate of plutonium in solution in the three columns for

either case is:

Loading: 19 l/column * 3 columns * 7 g/l = 399 g

Elution: 19 l/column * 3 columns * 60 g/l = 3420 g

These maximum mathematical estimates are, however, not physically attainable in the

system described. During the loading cycle, plutonium concentration is depleted from

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