RULES OF THUMB FOR BETA PARTICLES
1.
Beta particles of at least 70 keV energy are required to
penetrate the nominal protective layer of the skin.
2.
The average energy of a beta-ray spectrum is approximately
one-third the maximum energy.
3.
The range of beta particles in air is ~12 ft (3.6 m) / MeV.
4.
The range of beta particles (or electrons) in grams / cm
2
(thickness in cm multiplied by the density in g / cm ) is
3
approximately half the maximum energy in MeV. This rule
overestimates the range for low energies (0.5 MeV) and low
atomic numbers, and underestimates for high energies and
high atomic numbers.
5.
The exposure rate in rads per hour in an infinite medium
uniformly contaminated by a beta emitter is 2.12 EC /
r
where E is the average beta energy per disintegration in
MeV, C is the concentration in
ì
Ci / cm , and
r
is the
3
density of the medium in grams/cm . The dose rate at the
3
surface of the mass is one half the value given by this
relation. In such a large mass, the relative beta and gamma
dose rates are in the ratio of the average energies released
per disintegration.
6.
The surface dose rate through 7 mg / cm from a uniform
2
thin deposition of 1
m
Ci / cm is about 9 rads/h (90 mGy/h)
2
for energies above about 0.6 MeV. Note that in a thin layer,
the beta dose rate exceeds the gamma dose rate for equal
energies released by ~100.
162
RULES OF THUMB FOR BETA PARTICLES
1.
Beta particles of at least 70 keV energy are required to
penetrate the nominal protective layer of the skin.
2.
The average energy of a beta-ray spectrum is approximately
one-third the maximum energy.
3.
The range of beta particles in air is ~12 ft (3.6 m) / MeV.
4.
The range of beta particles (or electrons) in grams / cm
2
(thickness in cm multiplied by the density in g / cm ) is
3
approximately half the maximum energy in MeV. This rule
overestimates the range for low energies (0.5 MeV) and low
atomic numbers, and underestimates for high energies and
high atomic numbers.
5.
The exposure rate in rads per hour in an infinite medium
uniformly contaminated by a beta emitter is 2.12 EC /
r
where E is the average beta energy per disintegration in
MeV, C is the concentration in
ì
Ci / cm , and
r
is the density
3
of the medium in grams/cm . The dose rate at the surface
3
of the mass is one half the value given by this relation. In
such a large mass, the relative beta and gamma dose rates
are in the ratio of the average energies released per
disintegration.
6.
The surface dose rate through 7 mg / cm from a uniform
2
thin deposition of 1
m
Ci / cm is about 9 rads/h (90 mGy/h)
2
for energies above about 0.6 MeV. Note that in a thin layer,
the beta dose rate exceeds the gamma dose rate for equal
energies released by ~100.
162
RULES OF THUMB FOR BETA PARTICLES
1.
Beta particles of at least 70 keV energy are required to
penetrate the nominal protective layer of the skin.
2.
The average energy of a beta-ray spectrum is approximately
one-third the maximum energy.
3.
The range of beta particles in air is ~12 ft (3.6 m) / MeV.
4.
The range of beta particles (or electrons) in grams / cm
2
(thickness in cm multiplied by the density in g / cm ) is
3
approximately half the maximum energy in MeV. This rule
overestimates the range for low energies (0.5 MeV) and low
atomic numbers, and underestimates for high energies and
high atomic numbers.
5.
The exposure rate in rads per hour in an infinite medium
uniformly contaminated by a beta emitter is 2.12 EC /
r
where E is the average beta energy per disintegration in
MeV, C is the concentration in
ì
Ci / cm , and
r
is the
3
density of the medium in grams/cm . The dose rate at the
3
surface of the mass is one half the value given by this
relation. In such a large mass, the relative beta and gamma
dose rates are in the ratio of the average energies released
per disintegration.
6.
The surface dose rate through 7 mg / cm from a uniform
2
thin deposition of 1
m
Ci / cm is about 9 rads/h (90 mGy/h)
2
for energies above about 0.6 MeV. Note that in a thin layer,
the beta dose rate exceeds the gamma dose rate for equal
energies released by ~100.
162
RULES OF THUMB FOR BETA PARTICLES
1.
Beta particles of at least 70 keV energy are required to
penetrate the nominal protective layer of the skin.
2.
The average energy of a beta-ray spectrum is approximately
one-third the maximum energy.
3.
The range of beta particles in air is ~12 ft (3.6 m) / MeV.
4.
The range of beta particles (or electrons) in grams / cm
2
(thickness in cm multiplied by the density in g / cm ) is
3
approximately half the maximum energy in MeV. This rule
overestimates the range for low energies (0.5 MeV) and low
atomic numbers, and underestimates for high energies and
high atomic numbers.
5.
The exposure rate in rads per hour in an infinite medium
uniformly contaminated by a beta emitter is 2.12 EC /
r
where E is the average beta energy per disintegration in
MeV, C is the concentration in
ì
Ci / cm , and
r
is the density
3
of the medium in grams/cm . The dose rate at the surface
3
of the mass is one half the value given by this relation. In
such a large mass, the relative beta and gamma dose rates
are in the ratio of the average energies released per
disintegration.
6.
The surface dose rate through 7 mg / cm from a uniform
2
thin deposition of 1
m
Ci / cm is about 9 rads/h (90 mGy/h)
2
for energies above about 0.6 MeV. Note that in a thin layer,
the beta dose rate exceeds the gamma dose rate for equal
energies released by ~100.
162
