have been observed with regard to both highly soluble and highly insoluble forms, leading
to the good practice of performing dissolution rate (i.e., solubility) tests on standard
materials in a facility.
As plutonium ages in a residual, loose contamination form, such as might be found in old
duct work, glove boxes, or other such components, it can be expected to undergo slow
oxidation to a more insoluble form. Thus, class Y forms of plutonium may be reasonable
assumptions of what to expect during many decommissioning operations.
Particle size is an important consideration for inhalation exposures. The normal practice for
an aerosol is to identify the activity median aerodynamic diameter and its associated
particle-size distribution. Particle sizes of 10 Ám or less are considered respirable. The
common practice is to assume a 1-Ám particle size for dosimetry purposes because actual
particle size information is usually lacking. Particle size data are most readily obtainable
for chronic exposure situations.
Unless representative air sampling is performed in the immediate proximity of a worker
during abnormal working conditions, the practical likelihood of obtaining good particle-
size information is slim.
SCOPE OF BIOASSAY PROGRAM
The relatively low annual limit on intake of plutonium renders its radiation hazard
substantially more restrictive than its industrial hygiene or chemical toxicity hazard. Thus,
internal radiation dose or intake monitoring is the appropriate focus of bioassay monitoring.