7.0 Application Examples; Dissolving Operations Examples
spray through commercial nozzles, are 1E-4 and 1.0 (subsection 220.127.116.11.1). The
initial respirable source term is:
1200 g * 1.0 * 1E-4 * 1.0 = 0.1 g
This source term is generated within glovebox confinement.
B. Hydrogen Explosion. The original metal feed is 5 moles of Pu-239. The
stoichiometry of the dissolution reaction generates 1.5 moles of hydrogen for every
mole of plutonium dissolved, allowing a maximum of 7.5 moles. At ambient
glovebox conditions, this is ~ 190 l of gaseous hydrogen. The glovebox holding the
process is 4.5 m long, 1.2 m wide, and 1.8 m tall. Even allowing for 25% occupancy
by equipment, the total volume of the glovebox is over 7500 l. Uniformly dispersing
the maximum attainable hydrogen in the glovebox produces a volumetric
concentration of 2.5%. The lower flammability limit of hydrogen in air is 4.0%.
Given that the 170 l of hydrogen cannot be instantaneously generated and the
ventilation flowrate through the glovebox is over 10,000 lpm, a hydrogen explosion is
not a major concern in the glovebox air volume.
The hydrogen generation rate peaks at the beginning of the cycle, when both metal
surface area and acid concentrations are at their maximum. At that point, the rate of
hydrogen generation is ~ 0.08 ml/(cm2 sec) at the lower end of the operating
temperature range and ~ 0.3 ml/(cm2 sec) above the upper end based on experimental
data obtained by the site technical laboratory. To estimate hydrogen generation rates,
it is necessary to know the size of the metal piece being dissolved.
The minimum density for plutonium metal is ~ 16 g/cm3 in the delta phase, as
opposed to ~ 19.9 g/cm3 in the alpha phase. For example purposes, the minimum
density is assumed as this will yield the largest surface area. To avoid discussing
details of the metal, it is assumed to be in the shape of a square wafer with a
thickness of 2 cm. The 1200 g of plutonium metal would occupy a volume of 75 cm3
using the minimum density. For the given thickness of 2 cm, the length of a square
side is 6.1 cm. If the metal surface is assumed to be fully available for dissolution on
all surfaces, which it is not, the total surface area available is 123 cm2. The
corresponding minimum and maximum initial hydrogen generation rates are:
0.08 ml/(cm2 sec) * 123 cm2 = 10 ml/sec
0.3 ml/(cm2 sec) * 123 cm2 = 37 ml/sec.