Airborne Activity General Dispersion Model
Assume a 1 uCi (37 kBq) release of respirable Pu
inside a
239
large room measuring 12 x 12 x 3 meters with a ventilation
turnover rate of 7 volumes per hour.
The General Dispersion Model uses this 2
ð
formula for
volume.
V = 2/3
ð
x R
3
Volume in cm
30 cm
1 M
10 M
3
@ distance R
5.65E4
2.09E6
2.09E9
Concentration @ distance R
in uCi / cc
1.77E-5
4.78E-7
4.78E-10
Time required for the airborne wave front to reach distance R
13 sec
43 sec
7.15 min
1 CFM sample for 1 week equals 10,080 CF (285.4 M )
3
2 CFM sample for 1 week equals 20,160 CF (571 M )
3
Calculating Airborne Radioactivity (long-lived)
S
N
C =
R / (V x
î
x SA x CE x CF)
S
C =
activity concentration at end of sample run time
N
R =
net counting rate
V =
sample volume
î
=
detector efficiency
SA =
self-absorption factor
CE =
collection efficiency
CF =
conversion from disintegrations per unit time to activity
Calculating Airborne Radioactivity (short-lived)
S
N
C =
R / [V x
î
x SA x CE x CF x (1-e
) x (e
)]
-
ë
Ts
-
ë
Td
Ts =
sample count time
Tb =
time elapsed between end of sample collection time
and start of sample count time
Airborne Activity General Dispersion Model
Assume a 1 uCi (37 kBq) release of respirable Pu
inside a
239
large room measuring 12 x 12 x 3 meters with a ventilation
turnover rate of 7 volumes per hour.
The General Dispersion Model uses this 2
ð
formula for
volume.
V = 2/3
ð
x R
3
Volume in cm
30 cm
1 M
10 M
3
@ distance R
5.65E4
2.09E6
2.09E9
Concentration @ distance R
in uCi / cc
1.77E-5
4.78E-7
4.78E-10
Time required for the airborne wave front to reach distance R
13 sec
43 sec
7.15 min
1 CFM sample for 1 week equals 10,080 CF (285.4 M )
3
2 CFM sample for 1 week equals 20,160 CF (571 M )
3
Calculating Airborne Radioactivity (long-lived)
S
N
C =
R / (V x
î
x SA x CE x CF)
S
C =
activity concentration at end of sample run time
N
R =
net counting rate
V =
sample volume
î
=
detector efficiency
SA =
self-absorption factor
CE =
collection efficiency
CF =
conversion from disintegrations per unit time to activity
Calculating Airborne Radioactivity (short-lived)
S
N
C =
R / [V x
î
x SA x CE x CF x (1-e
) x (e
)]
-
ë
Ts
-
ë
Td
Ts =
sample count time
Tb =
time elapsed between end of sample collection time
and start of sample count time
Airborne Activity General Dispersion Model
Assume a 1 uCi (37 kBq) release of respirable Pu
inside a
239
large room measuring 12 x 12 x 3 meters with a ventilation
turnover rate of 7 volumes per hour.
The General Dispersion Model uses this 2
ð
formula for
volume.
V = 2/3
ð
x R
3
Volume in cm
30 cm
1 M
10 M
3
@ distance R
5.65E4
2.09E6
2.09E9
Concentration @ distance R
in uCi / cc
1.77E-5
4.78E-7
4.78E-10
Time required for the airborne wave front to reach distance R
13 sec
43 sec
7.15 min
1 CFM sample for 1 week equals 10,080 CF (285.4 M )
3
2 CFM sample for 1 week equals 20,160 CF (571 M )
3
Calculating Airborne Radioactivity (long-lived)
S
N
C =
R / (V x
î
x SA x CE x CF)
S
C =
activity concentration at end of sample run time
N
R =
net counting rate
V =
sample volume
î
=
detector efficiency
SA =
self-absorption factor
CE =
collection efficiency
CF =
conversion from disintegrations per unit time to activity
Calculating Airborne Radioactivity (short-lived)
S
N
C =
R / [V x
î
x SA x CE x CF x (1-e
) x (e
)]
-
ë
Ts
-
ë
Td
Ts =
sample count time
Tb =
time elapsed between end of sample collection time
and start of sample count time
Airborne Activity General Dispersion Model
Assume a 1 uCi (37 kBq) release of respirable Pu
inside a
239
large room measuring 12 x 12 x 3 meters with a ventilation
turnover rate of 7 volumes per hour.
The General Dispersion Model uses this 2
ð
formula for
volume.
V = 2/3
ð
x R
3
Volume in cm
30 cm
1 M
10 M
3
@ distance R
5.65E4
2.09E6
2.09E9
Concentration @ distance R
in uCi / cc
1.77E-5
4.78E-7
4.78E-10
Time required for the airborne wave front to reach distance R
13 sec
43 sec
7.15 min
1 CFM sample for 1 week equals 10,080 CF (285.4 M )
3
2 CFM sample for 1 week equals 20,160 CF (571 M )
3
Calculating Airborne Radioactivity (long-lived)
S
N
C =
R / (V x
î
x SA x CE x CF)
S
C =
activity concentration at end of sample run time
N
R =
net counting rate
V =
sample volume
î
=
detector efficiency
SA =
self-absorption factor
CE =
collection efficiency
CF =
conversion from disintegrations per unit time to activity
Calculating Airborne Radioactivity (short-lived)
S
N
C =
R / [V x
î
x SA x CE x CF x (1-e
) x (e
)]
-
ë
Ts
-
ë
Td
Ts =
sample count time
Tb =
time elapsed between end of sample collection time
and start of sample count time