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Precipitation and Co-precipitation - doe-std-1128-98_ch10229
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DOE Standard Guide of Good Practices for Occupational Radiological Protection In Plutonium Facilities
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Distillation - doe-std-1128-98_ch10231


DOE-STD-1128-98
water stream is being recycled, the cation resin will probably be in the
hydrogen form so that only hydrogen ions will enter the solution. If a
hydrogen form of cation resin is used by itself, the water solution will
likely become more acidic (lower pH). If an anion resin is used, anions in
solution will be replaced with anions from the resin. Although resin may be
in a chloride or other form, the hydroxyl form of the resin is often used so
that anions are replaced with hydroxyl anions (-OH). If only a hydroxyl
anion resin is used, the solution will drop in pH, becoming more basic. If
both a hydrogen form of cation resin and a hydroxyl form of anion resin
are used, the ions they add combine to form water, so both resins are used
on demineralized water systems that are recycled. One disadvantage of
most ion-exchange resins for waste treatment is the fact that they remove
all ionic contaminants, not just the radioactive ones, and so are exhausted
earlier than they might be. Selective resins are available for a few
materials, most notably cesium, but are not available for plutonium.
In some applications, radionuclides pass through both cation and anion
resin beds. This is assumed to happen because they are not present in an
ionic form. They are either colloidal or are present in a molecule or
complex that is neutral. In these cases, pretreatment or multiple treatment
steps may be required.
Unfortunately, plutonium may be present as a cation, anion, neutral
chemical complex, or colloid. Testing is almost always required to
optimize plutonium removal. One additional limitation in the use of most
ion exchange media for plutonium and other alpha-emitting radionuclides
is that the radiation degrades the resin over time. Organic ion exchange
media loaded with large quantities of plutonium may emit hydrogen and
may become unstable when exposed to oxidizing materials such as nitric
acid.
In some applications, ion exchange resins are "recharged" by the addition
of large quantities of a particular ion (e.g., hydrochloric acid may be used
to reconvert spent cation resin to the hydrogen form). In nuclear
applications, this is rarely feasible because of the need to dispose of the
recharge solution and because of the large quantity of rinse water used to
remove the excess recharge solution from the resin.
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