Activity in DPM vs Particle Size in microns
234
U
235
U
238
U
237
Np
238
Pu
239
Pu
240
Pu
241
Pu
241
Am
1. Volume of the particle is
2. Use the density of the isotope listed in this reference.
3. Mass of the particle is
4. Activity of the particle is
Correct the activity of the particle for the oxide form if you need
that; the molecular weight of Pu
dioxide form must be reduced by the ratio of the molecular
weight of the dioxide form to the molecular weight of Pu .
Multiply the calculated activity by 238/270 to get the activity of
the dioxide form.
For particles larger than about 1ì the aerodynamic diameter is
approximately equal to the physical diameter times the square
root of the density. The 10ì diameter particle in our example
would have an equivalent aerodynamic diameter of 34ì (10ì x
the square root of 11.46). This must be taken into account in air
sampling/monitoring situations.
for oxide form of various isotopes
0.5ì
1ì
8.7E-3
0.07
3.0E-6
2.4E-5
4.7E-7
3.8E-6
1.0E-3
8.0E-3
25
201
0.09
0.73
0.33
2.7
151
1210
5.1
41.1
Calculating Activity vs Particle Size
5ì
9
3E-3
5E-4
1.0
2.5E4
91
333
1.5E5
5140
3
V = 1/6ðd .
M = V x density.
A = M x specific activity.
238
is 238, the activity of the
44
10ì
50ì
69.7
8700
0.02
3
3.8E-3
0.47
8
1000
2E5
2.5E7
730
9.1E4
2670
3.3E5
1.2E6
1.5E8
4.1E4
5.14E6
238