Uranium Incidents (Smith, 1956)

ACCIDENT CASE STUDIES

DOE-HDBK-1081-94

Spontaneous Heating and Pyrophoricity

in segregated open-top bins. Several days after a heavy rain, a fire of unknown origin took

place in one of the bins with flames extending 100 feet into the air. Shortly afterwards,

contents of other (but not necessarily adjoining) bins suddenly and intermittently flared up.

Material in all bins soon became involved and 159,000 pounds of Zr were consumed. The

heat was sufficiently intense to crack windows and ignite wood located over 150 feet away.

Particles of burning Zr were carried over one-quarter mile through the air.

In 1951, some water-wet scrap Zr powder in wooden barrels was placed in outside storage

pending development of scrap-recovery processes. During the next several years, a few

minor spontaneous fires broke out in this material. In January 1956, the material in several

deteriorated wooden barrels was wet with water and repackaged in steel drums. In May

1956, employees working in the area noted that one of the steel drums lying on its side

contained a black material "similar to carbon dust." What happened is uncertain, but a

spontaneous explosion occurred accompanied by streaks of red fire with black smoke

extending 100 feet into the air. A pronounced concussion wave was noted and the sound of

the blast was heard several miles away. Two employees were killed, one having been blown

80 feet through the air, and a the third lost an arm. The drum contained Zr, probably in the

form of a fine powder. Using extensive precautions, the remaining drums of scrap Zr were

subsequently burned. During this operation, one of the drums exploded.

Two men died and two others were seriously injured in 1954 in a spontaneous explosion

initiated during removal of the friction-top lid from a polythene-bag-lined, 1-gallon metal

can containing Zr powder 16 percent wet with water. A ball of flame enveloped the entire

area, accompanied by a concussion wave.

A 2-pound sample of carbon-tetrachloride-moistened powdered Zr was placed in a glass

flask, vacuum applied, and the flask very gently heated with a Bunsen burner. The Zr

suddenly began to heat up and detonated with a blinding flash. The explosion was attributed

to a small amount of water.

Uranium Incidents (Smith, 1956)

In January 1955, an attempt was made to roll two 1,000-lb U slabs into 0.01-inch thick

strips. After initial heating to 1,150 F in a lithium-carbonate-potassium/carbonate bath,

several 30 percent reductions were made by rolling. It was observed that heavy work passes

had caused overheating. The strip, then 3/4 inch thick, was cooled to 1,200 F. The strip

again excessively heated during the next three reductions and became so ductile on entering

the fourth that it pulled into two parts. The strip at this stage was cherry red, but by the time

it had been removed to the mill floor it was observed to increase in temperature to a white

heat followed by melting and burning.

In February 1956, a technician was attempting to roll a plate consisting of Zr-clad U, which,

in turn, was clad in a low-carbon-steel jacket. During preheating, the furnace temperature

control (which had been set to 1,450 F) failed, allowing the temperature to rise to 1,800 F.

Pyrophoricity

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