RULES OF THUMB FOR GAMMA RADIATION
1.
The range of gamma rays (any photon) for energies from eV
to 10 MeV in air is from a few mm to 100 meters. The range
of those photons in water is from a few mm to several cm.
2.
The dose rate 1 m above a flat, infinite plane contaminated
with a thin layer (1 Ci / m ) of gamma emitters is:
2
Dose Rate
Energy (MeV)
rem/h
mSv/h
0.4
7.2
72
0.6
10
100
0.8
13
130
1.0
16
160
1.2
19
190
3.
The dose rate in rem/h per hour in an infinite medium
uniformly contaminated by a gamma emitter is 2.12 EC /
r
,
where C is the number of microcuries per cubic centimeter,
E is the average gamma energy per disintegration in MeV,
and
r
is the density of the medium. At the surface of a large
body, the dose rate is about half of this. At ground level
(one-half of an infinite cloud), the dose rate from a uniformly
contaminated atmosphere is 1,600 EC rem/h per
m
Ci / cm .
3
4.
The radiation scattered from the air (skyshine) from a 100 Ci
Co source 30 cm behind a 1 m high shield is ~ 100 mR/h
60
(1 mSv/h) at 15 cm from the outside of the shield.
164
RULES OF THUMB FOR GAMMA RADIATION
1.
The range of gamma rays (any photon) for energies from eV
to 10 MeV in air is from a few mm to 100 meters. The range
of those photons in water is from a few mm to several cm.
2.
The dose rate 1 m above a flat, infinite plane contaminated
with a thin layer (1 Ci / m ) of gamma emitters is:
2
Dose Rate
Energy (MeV)
rem/h
mSv/h
0.4
7.2
72
0.6
10
100
0.8
13
130
1.0
16
160
1.2
19
190
3.
The dose rate in rem/h per hour in an infinite medium
uniformly contaminated by a gamma emitter is 2.12 EC /
r
,
where C is the number of microcuries per cubic centimeter,
E is the average gamma energy per disintegration in MeV,
and
r
is the density of the medium. At the surface of a large
body, the dose rate is about half of this. At ground level
(one-half of an infinite cloud), the dose rate from a uniformly
contaminated atmosphere is 1,600 EC rem/h per
m
Ci / cm .
3
4.
The radiation scattered from the air (skyshine) from a 100 Ci
Co source 30 cm behind a 1 m high shield is ~ 100 mR/h
60
(1 mSv/h) at 15 cm from the outside of the shield.
164
RULES OF THUMB FOR GAMMA RADIATION
1.
The range of gamma rays (any photon) for energies from eV
to 10 MeV in air is from a few mm to 100 meters. The range
of those photons in water is from a few mm to several cm.
2.
The dose rate 1 m above a flat, infinite plane contaminated
with a thin layer (1 Ci / m ) of gamma emitters is:
2
Dose Rate
Energy (MeV)
rem/h
mSv/h
0.4
7.2
72
0.6
10
100
0.8
13
130
1.0
16
160
1.2
19
190
3.
The dose rate in rem/h per hour in an infinite medium
uniformly contaminated by a gamma emitter is 2.12 EC /
r
,
where C is the number of microcuries per cubic centimeter,
E is the average gamma energy per disintegration in MeV,
and
r
is the density of the medium. At the surface of a large
body, the dose rate is about half of this. At ground level
(one-half of an infinite cloud), the dose rate from a uniformly
contaminated atmosphere is 1,600 EC rem/h per
m
Ci / cm .
3
4.
The radiation scattered from the air (skyshine) from a 100 Ci
Co source 30 cm behind a 1 m high shield is ~ 100 mR/h
60
(1 mSv/h) at 15 cm from the outside of the shield
164
RULES OF THUMB FOR GAMMA RADIATION
1.
The range of gamma rays (any photon) for energies from eV
to 10 MeV in air is from a few mm to 100 meters. The range
of those photons in water is from a few mm to several cm.
2.
The dose rate 1 m above a flat, infinite plane contaminated
with a thin layer (1 Ci / m ) of gamma emitters is:
2
Dose Rate
Energy (MeV)
rem/h
mSv/h
0.4
7.2
72
0.6
10
100
0.8
13
130
1.0
16
160
1.2
19
190
3.
The dose rate in rem/h per hour in an infinite medium
uniformly contaminated by a gamma emitter is 2.12 EC /
r
,
where C is the number of microcuries per cubic centimeter,
E is the average gamma energy per disintegration in MeV,
and
r
is the density of the medium. At the surface of a large
body, the dose rate is about half of this. At ground level
(one-half of an infinite cloud), the dose rate from a uniformly
contaminated atmosphere is 1,600 EC rem/h per
m
Ci / cm .
3
4.
The radiation scattered from the air (skyshine) from a 100 Ci
Co source 30 cm behind a 1 m high shield is ~ 100 mR/h
60
(1 mSv/h) at 15 cm from the outside of the shield.
164
