Release Estimation - h3010v10277

DOE-HDBK-3010-94

7.0 Application Examples; Dissolving Operations Examples

acid is added to the dissolving slab tank and circulated to insure any hydride generated has

been passivated. Additionally, 35% nitric acid is also supplied to the glovebox to adjust

product acid concentration.

Plutonium hydride sludge, which can become oxide in a spontaneous exothermic reaction

under certain conditions, can be generated if the dissolution temperature is not a minimum of

~ 50 oC. It is desired to keep the temperature below ~ 71 oC to prevent dissolving an

impurity associated with the metal. Hydrogen gas is also generated by the dissolution

reaction at a rate that increases with solution temperature, presenting a potential explosive

hazard. The development of an explosive concentration of hydrogen is prevented first by

controlling steam flow to the heat exchanger by temperature indication from the slab vessel.

High temperature in the dissolving spray chamber will activate an alarm at 64 oC and turn off

the centrifugal pump circulating acid at 68 oC. Securing acid flow results in a rapid reaction

rate decrease as the limited acid supply in the spray chamber depletes.

The second means to prevent developing an explosive concentration of hydrogen is a

continuous air purge of the spray chamber supplied by the process air system. The purge

exhaust goes to the vessel vent system and is monitored by a hydrogen detector that also

turns off the centrifugal pump if hydrogen concentration in the offgas exceeds 2.5% (4.0% is

lower flammable limit).

7.3.4.2

Release Estimation

The potential energetic phenomenon not previously covered in other examples are a pump or

piping failure causing liquid spray, a hydrogen explosion, and plutonium hydride oxidation.

A. Liquid Spray. The use of a centrifugal pump for liquid circulation generates

positive pressure. While the pressure is not high in this small process, it is sufficient

to produce liquid spray and thus a different release stress than the vacuum transfer

systems in other dissolution lines. A pump seal, flange failure, or even a piping leak

could cause spray generation. The maximum amount of material available in solution

is 1200 g of plutonium if all of the metal is dissolved. The DR will probably not be

1.0 even if no operator intervention occurs as the pump eventually shuts off from loss

of net positive suction head after sufficient liquid is lost. The distinction, however,

could be minor; therefore a DR of 1.0 is used for the sake of simplicity in this

example.

The phenomena is bounded by the depressurization of liquid via a failure under the

liquid surface level. The ARF and RF for this phenomena, which are based on liquid

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