Gilson and Voss - Voss Associates

MISCELLANEOUS RULES OF THUMB
1. One watt of power in a reactor requires 3.1E10 fissions per
second. In a reactor operating for more than 4 days, the
total fission products are about 3 Ci / watt at 1.5 min after
shutdown. At 2 yr after shutdown, the fission products are
approximately 75 Ci / MW-day.
2. The quantity of a short-lived fission product in a reactor
which has been operated about four times as long as the
half-life is given by; Ci (FY)(PL) ,
where FY is the fission yield (%/100) and PL is the power
level in watts.
3. Correction factor for unsealed ion chambers to STP (0 0 C
and 760 mm of Hg) is f = (t + 273)/(273) x (760 / P)
where t is the ambient temperature in degrees C and P is
the ambient barometric pressure in mm of Hg.
4. The activity of an isotope (without radioactive daughter) is
reduced to less than 1% after seven half-lives.
5. NATURALLY OCCURRING RADIONUCLIDES
Primordial
Cosmogonic
40
K
Tritium
87 7
Rb
Be
Natural U and Th C 14
6. Unified Time, Distance, and Shielding formula for reduction
of external dose.
2 n
Rem = Initial Rem/hr x T in hours x (D
2) x 0.5
2
(D)
1
Where: Rem is the dose after applying reduction methods
T is the exposure time in hours
D
1
is the initial distance to the source
D
2
is the new distance to the source
n
0.5 is the Shielding for ‘n’ half-value layers
Page 139
MISCELLANEOUS RULES OF THUMB
1. One watt of power in a reactor requires 3.1E10 fissions per
second. In a reactor operating for more than 4 days, the
total fission products are about 3 Ci / watt at 1.5 min after
shutdown. At 2 yr after shutdown, the fission products are
approximately 75 Ci / MW-day.
2. The quantity of a short-lived fission product in a reactor
which has been operated about four times as long as the
half-life is given by; Ci (FY)(PL) ,
where FY is the fission yield (%/100) and PL is the power
level in watts.
3. Correction factor for unsealed ion chambers to STP (0 0 C
and 760 mm of Hg) is f = (t + 273)/(273) x (760 / P)
where t is the ambient temperature in degrees C and P is
the ambient barometric pressure in mm of Hg.
4. The activity of an isotope (without radioactive daughter) is
reduced to less than 1% after seven half-lives.
5. NATURALLY OCCURRING RADIONUCLIDES
Primordial
Cosmogonic
40
K
Tritium
87 7
Rb
Be
Natural U and Th C 14
6. Unified Time, Distance, and Shielding formula for reduction
of external dose.
2 n
Rem = Initial Rem/hr x T in hours x (D
2) x 0.5
2
(D)
1
Where: Rem is the dose after applying reduction methods
T is the exposure time in hours
D
1
is the initial distance to the source
D
2
is the new distance to the source
n
0.5 is the Shielding for ‘n’ half-value layers
Page 139
MISCELLANEOUS RULES OF THUMB
1. One watt of power in a reactor requires 3.1E10 fissions per
second. In a reactor operating for more than 4 days, the
total fission products are about 3 Ci / watt at 1.5 min after
shutdown. At 2 yr after shutdown, the fission products are
approximately 75 Ci / MW-day.
2. The quantity of a short-lived fission product in a reactor
which has been operated about four times as long as the
half-life is given by; Ci (FY)(PL) ,
where FY is the fission yield (%/100) and PL is the power
level in watts.
3. Correction factor for unsealed ion chambers to STP (0 0 C
and 760 mm of Hg) is f = (t + 273)/(273) x (760 / P)
where t is the ambient temperature in degrees C and P is
the ambient barometric pressure in mm of Hg.
4. The activity of an isotope (without radioactive daughter) is
reduced to less than 1% after seven half-lives.
5. NATURALLY OCCURRING RADIONUCLIDES
Primordial
Cosmogonic
40
K
Tritium
87 7
Rb
Be
Natural U and Th C 14
6. Unified Time, Distance, and Shielding formula for reduction
of external dose.
2 n
Rem = Initial Rem/hr x T in hours x (D
2) x 0.5
2
(D)
1
Where: Rem is the dose after applying reduction methods
T is the exposure time in hours
D
1
is the initial distance to the source
D
2
is the new distance to the source
n
0.5 is the Shielding for ‘n’ half-value layers
Page 139
MISCELLANEOUS RULES OF THUMB
1. One watt of power in a reactor requires 3.1E10 fissions per
second. In a reactor operating for more than 4 days, the
total fission products are about 3 Ci / watt at 1.5 min after
shutdown. At 2 yr after shutdown, the fission products are
approximately 75 Ci / MW-day.
2. The quantity of a short-lived fission product in a reactor
which has been operated about four times as long as the
half-life is given by; Ci (FY)(PL) ,
where FY is the fission yield (%/100) and PL is the power
level in watts.
3. Correction factor for unsealed ion chambers to STP (0 0 C
and 760 mm of Hg) is f = (t + 273)/(273) x (760 / P)
where t is the ambient temperature in degrees C and P is
the ambient barometric pressure in mm of Hg.
4. The activity of an isotope (without radioactive daughter) is
reduced to less than 1% after seven half-lives.
5. NATURALLY OCCURRING RADIONUCLIDES
Primordial
Cosmogonic
40
K
Tritium
87 7
Rb
Be
Natural U and Th C 14
6. Unified Time, Distance, and Shielding formula for reduction
of external dose.
2 n
Rem = Initial Rem/hr x T in hours x (D
2) x 0.5
2
(D)
1
Where: Rem is the dose after applying reduction methods
T is the exposure time in hours
D
1
is the initial distance to the source
D
2
is the new distance to the source
n
0.5 is the Shielding for ‘n’ half-value layers
Page 139