Reduction Line cont'd

DOE-HDBK-3010-94

7.0 Application Examples; Reduction Line Example

denser plutonium flows to the bottom of the crucible in a distinct phase. When the crucible

is cooled, the plutonium solidifies as a mass of pure metal.

The cooled crucible is broken, and the product plutonium metal button is cleaned and passed

through an airlock to the packaging station. There, the button is first dipped in a 2-l 35%

nitric acid bath and then in an identical water bath to remove any slag contamination. A

3/8" drill is used to obtain a small sample of the metal for analysis. The metal is then sealed

in a can and bagged out of the glovebox.

The small pyrotechnic charges used in the reduction operation contain magnesium metal.

These charges generally ignite at temperatures between 60 oC and 150 oC, with an intense,

white hot burn lasting less than a second. The purpose of these charges is to catalyze the

exothermic calcium-plutonium reactions, so that more of the heat of reaction can be used to

elevate the mixture temperature and less heat must be supplied by the furnace. This results

in lower ultimate temperatures and pressures in the reduction vessel itself.

The induction furnace heating coils are supplied by a 30-kw motor-generator mounted in the

floor of the glovebox. The hydraulic press that locks the reduction vessel in place in the

induction furnace operates at pressures in excess of 2.1 MPag (300 psig) and uses a hydraulic

fluid with a flammable rating of 0, which means that it is not practically combustible. Argon

and nitrogen are supplied to the glovebox from 0.1 MPag (15 psig) for the purposes of

inerting the reduction furnace and the overall glovebox respectively. Process water is also

supplied to jacket lines that cool the exterior of the reduction furnace.

The use of calcium can be a problem if excessive contaminant moisture is present in the

crucible or the plutonium fluoride. Hydrogen is a product of the reaction. The reaction of

calcium and water is also exothermic. Under the right conditions, it can generate sufficient

heat to ignite the pyrotechnic charge outside the induction furnace. As noted above, the

charge typically would produce a localized high temperature region in the mixture upon

ignition, potentially initiating the reduction reaction outside the furnace. Also, a defect in the

charge, such as partial decomposition due to excessive storage time, could result in an

explosive bang on the order of a small firecracker. It is noted that the charge can also be

ignited for other reasons, such as failure to properly cool a magnesium oxide crucible.

Historically, the unit has experienced failure of the reduction vessel pressure seal four times

during the reduction process. In the two worst instances before the glovebox was inerted,

small fireballs were observed. In addition, relatively minor thermal damage occurred to

several glovebox gloves, and contamination was released to the operating rooms. In all

cases, however, the bulk of the molten plutonium mass remained in the crucible. These

historical cases were largely due to gasket design difficulties and improper gasket installation

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