Ignition of Plutonium Metal Fines

DOE-HDBK-3010-94

7.0 Application Examples; Feed Preparation Example

The equation as used in this case has already been multiplied by the factor of two

necessary to obtain a bounding value. It is noted that the absolute density of

plutonium oxide (11.5 g/cm3) was not used. The equation requires the use of bulk

powder density, which must take void volume into account. The value of 2.5 g/cm3

used is representative of heavy metal oxides such as plutonium oxide.

The value of ARF obtained from this equation is not directly related to the bounding

RF of 0.3 assigned. While it may be adequate to assume the 0.3 value for spill

distances greater than 3 m, it is not for distances significantly less than 3 m as the

small fall distance minimizes the time for particulate interaction and agglomeration.

The equation provided in subsection 4.4.3.1.2 for estimating particle size is:

AMMD = 12.1 - 3.29(

) + 7540(ARF)

(7-3, 4-6)

where:

AMMD

= aerodynamic equivalent mass median diameter

= 5 m,

= bulk powder density = 2.5 g/cm3, and

ARF

= airborne release fraction = 1.5E-4.

An AMMD of 5 m would indicate an RF significantly higher than 0.3, producing a

combined ARF x RF of ~ 1E-4. This is a factor of 6 less than the combined

ARF x RF (6E-4) assessed for fall distances less than 3 m, and approximately the

same as the median ARF x RF (1.5E-4) estimate provided in the handbook for

perspective on conservatism. For the types of estimates being made, there is not a

major difference between the two values. Either estimate could be defended, but for

the sake of conservatism and consistency, the bounding value is used.

B. Ignition of Plutonium Metal Fines. If plutonium metal fines are present in an

oxide container opened in an oxygen environment, it is not uncommon to see brief

sparking after opening. This is generally not a major concern due to the limited

amount of fines. Even if a given small piece of metal sustains smoldering oxidation,

the overall fire hazard is minimal. The metal is not in close proximity to a significant

amount of combustible material with which to interact; it will generally cease

combustion due to heat transfer losses through metal surfaces, and the combustion can

easily be extinguished by the operator simply by closing the container.

The hazard identification states that 100 g of metal fines is the maximum amount of

metal contamination anticipated in impure oxide received for processing. The

absolute limit is 2000 g if an entire feed can contains nothing but metal fines, but the

maximum anticipated DR is 0.05. The DR for metal fines present is never

Page 7-7