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Page Title:
Example 4.6. The Number of Particles for Breathing Zone Air Sampling of a Lower Specific |
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|  DOE-STD-1121-98
Example 4.6. The Number of Particles for Breathing Zone Air Sampling of a Lower Specific
Activity Radionuclide
In the previous example, it was shown that breathing zone air sampling in a facility that
handled 238Pu might not be useful. For lower specific activity material, there is no similar problem.
For example, "6%" plutonium (Table 9.2 in Sula et al.1991), aged 14.4 years, has 50% ingrowth of
Am (Rittmann 1993), a specific activity of 3.44E9 Bq/g of "-emitters, and an "-NALI of 458 Bq
241
(bone surfaces). Using the same density for plutonium oxide and calulational approach as in
Example 4.5, gives the table below. It shows that the number of particles corresponding to 2% of a
NALI does not create is a problem until the AMAD > 10 :m. It is important, however, to minimize
accidental filter contamination by even one "large" particle. One 10-:m particle corresponds to an
HT=bone surfaces,50 of about 60 mrem and an HE,50 of about 5 mrem.
Aerodynamic Equivalent
Number of Number of
Volume Mass per Activity per
Diameter Physical Dia.
particles per particles per
(:m)
(:m)
(cm3) particle (g) particle (Bq)
NALI 0.02 NALI
0.1
0.012
8.1E-19
8.9E-18
3.1E-08
1.5E+10
3.0E+08
0.2
0.029
1.2E-17
1.3E-16
4.6E-07
9.9E+08
2.0E+07
0.3
0.050
6.7E-17
7.3E-16
2.5E-06
1.8E+08
3.6E+06
0.5
0.10
5.6E-16
6.2E-15
2.1E-05
2.1E+07
429,056
0.7
0.16
2.1E-15
2.4E-14
8.1E-05
5.6E+06
112,937
1
0.25
8.1E-15
8.9E-14
3.1E-04
1.5E+06
30,000
2
0.55
8.6E-14
9.5E-13
3.3E-03
140,494
2810
3
0.85
3.2E-13
3.5E-12
1.2E-02
37,912
758
5
1.4
1.6E-12
1.8E-11
6.0E-02
7,590
152
7
2.1
4.5E-12
5.0E-11
1.7E-01
2,676
54
10
3.0
1.4E-11
1.5E-10
5.1E-01
895
18
20
6.0
1.1E-10
1.2E-09
4.2E+00
109
2.2
30
9.0
3.8E-10
4.2E-09
1.4E+01
32
0.64
50
15
1.8E-09
2.0E-08
6.7E+01
6.8
0.14
70
21
4.9E-09
5.4E-08
1.8E+02
2.5
0.050
100
30
1.4E-08
1.6E-07
5.4E+02
0.85
0.017
200
60
1.1E-07
1.3E-06
4.3E+03
0.11
0.0021
300
90
3.9E-07
4.3E-06
1.5E+04
0.031
0.00063
Instruments used for air monitoring should be real-time monitors that continuously measure and
display results for periods of one hour or less. They should be placed to measure the highest
concentrations to which workers in the area are likely to be exposed.
43
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