Hazard Summary cont'd

DOE-HDBK-3010-94

7.0 Application Examples; Liquid Storage and Ion Exchange Examples

holding tanks in the tank farm. The 4% nitric acid elution flow (purified plutonium solution)

is directed to eluate holding tanks in the tank farm that serve as feed to the evaporation line.

Each ion exchange column contains ~ 15,000 g of a strong base, polystyrene anion resin.

Process and instrument air are fed into the glovebox by pressurized sources ranging from 0.2

to 0.45 MPag (30 to 65 psig). An in-line heat exchanger heats solution by 0.2 MPag

(35 psig) process steam. Process chilled water is supplied as well.

The presence of a large number of active sites designed to exchange ions accompanied by

extensive polymer cross-linking in the overall resin matrix creates an inherent potential for

instability in the type of resin used. Under the right circumstances, this instability can be

expressed in a wide variety of exothermic reactions. Such reactions involving ion exchange

resins have resulted in vessel ruptures, fires, and explosions throughout general industry.

Significant potential for worker injury exists in such an incident, and explosions of large ion

exchange columns have resulted in worker fatalities.

The extreme range of the phenomena is exemplified by an actual explosion in a

Czechoslovakian sugar factory where the introduction of a hot sugar solution to an ion

exchange reservoir resulted in a complex reaction involving amino acids and the glucosidic

hydroxyl groups of the sugar. The experience of ion exchange column ruptures, fires, and

explosions in nuclear materials purification units in the United States, France, South Africa,

and Russia have typically involved the by now well-established oxidizing potential of nitric

acid with ion exchange resins. A variety of reactions is possible, but once the thermal

excursion reaches an autocatalytic state, an overpressurization incident of some type is

inevitable.

A large number of laboratory studies and incident investigations have codified a general set

of empirical precautionary measures designed to prevent exothermic reactions. A summary

of major preventive measures is provided below:

1. Nitric acid should be used only with strong-base resins due to the significantly

greater instability of weak-base resins;

2. When not in use, the resin column should be kept wet with very dilute nitric acid or

water because dry resin has a lower ignition temperature, and repeated wetting and

drying cycles can cause premature resin degradation;

3. The temperature of the resin column should be kept below 60 oC (140 oF) as

studies have indicated temperatures in excess of this value can ignite resin and sustain

a decomposition reaction;

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