Gilson and Voss - Voss Associates
Gilson and Voss - Voss Associates
Gilson and Voss - Voss Associates
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RULES OF THUMB FOR BETA PARTICLES<br />
1. Beta particles of at least 70 keV energy are required to<br />
penetrate the nominal protective layer of the skin.<br />
2. The average energy of a beta-ray spectrum is approximately<br />
one-third the maximum energy.<br />
3. The range of beta particles in air is ~12 ft (3.6 m) / MeV.<br />
4. The range of beta particles (or electrons) in grams / cm 2<br />
3<br />
(thickness in cm multiplied by the density in g / cm ) is<br />
approximately half the maximum energy in MeV. This rule<br />
overestimates the range for low energies (0.5 MeV) <strong>and</strong> low<br />
atomic numbers, <strong>and</strong> underestimates for high energies <strong>and</strong><br />
high atomic numbers.<br />
5. The exposure rate in rads per hour in an infinite medium<br />
uniformly contaminated by a beta emitter is 2.12 EC / <br />
where E is the average beta energy per disintegration in<br />
3<br />
MeV, C is the concentration in ìCi / cm , <strong>and</strong> is the<br />
3<br />
density of the medium in grams/cm . The dose rate at the<br />
surface of the mass is one half the value given by this<br />
relation. In such a large mass, the relative beta <strong>and</strong> gamma<br />
dose rates are in the ratio of the average energies released<br />
per disintegration.<br />
2<br />
6. The surface dose rate through 7 mg / cm from a uniform<br />
2<br />
thin deposition of 1 Ci / cm is about 9 rads/h (90 mGy/h)<br />
for energies above about 0.6 MeV. Note that in a thin layer,<br />
the beta dose rate exceeds the gamma dose rate for equal<br />
energies released by ~100.<br />
Page 126<br />
RULES OF THUMB FOR BETA PARTICLES<br />
1. Beta particles of at least 70 keV energy are required to<br />
penetrate the nominal protective layer of the skin.<br />
2. The average energy of a beta-ray spectrum is approximately<br />
one-third the maximum energy.<br />
3. The range of beta particles in air is ~12 ft (3.6 m) / MeV.<br />
4. The range of beta particles (or electrons) in grams / cm 2<br />
3<br />
(thickness in cm multiplied by the density in g / cm ) is<br />
approximately half the maximum energy in MeV. This rule<br />
overestimates the range for low energies (0.5 MeV) <strong>and</strong> low<br />
atomic numbers, <strong>and</strong> underestimates for high energies <strong>and</strong><br />
high atomic numbers.<br />
5. The exposure rate in rads per hour in an infinite medium<br />
uniformly contaminated by a beta emitter is 2.12 EC / <br />
where E is the average beta energy per disintegration in<br />
3<br />
MeV, C is the concentration in ìCi / cm , <strong>and</strong> is the density<br />
3<br />
of the medium in grams/cm . The dose rate at the surface<br />
of the mass is one half the value given by this relation. In<br />
such a large mass, the relative beta <strong>and</strong> gamma dose rates<br />
are in the ratio of the average energies released per<br />
disintegration.<br />
2<br />
6. The surface dose rate through 7 mg / cm from a uniform<br />
2<br />
thin deposition of 1 Ci / cm is about 9 rads/h (90 mGy/h)<br />
for energies above about 0.6 MeV. Note that in a thin layer,<br />
the beta dose rate exceeds the gamma dose rate for equal<br />
energies released by ~100.<br />
Page 126<br />
RULES OF THUMB FOR BETA PARTICLES<br />
1. Beta particles of at least 70 keV energy are required to<br />
penetrate the nominal protective layer of the skin.<br />
2. The average energy of a beta-ray spectrum is approximately<br />
one-third the maximum energy.<br />
3. The range of beta particles in air is ~12 ft (3.6 m) / MeV.<br />
4. The range of beta particles (or electrons) in grams / cm 2<br />
3<br />
(thickness in cm multiplied by the density in g / cm ) is<br />
approximately half the maximum energy in MeV. This rule<br />
overestimates the range for low energies (0.5 MeV) <strong>and</strong> low<br />
atomic numbers, <strong>and</strong> underestimates for high energies <strong>and</strong><br />
high atomic numbers.<br />
5. The exposure rate in rads per hour in an infinite medium<br />
uniformly contaminated by a beta emitter is 2.12 EC / <br />
where E is the average beta energy per disintegration in<br />
3<br />
MeV, C is the concentration in ìCi / cm , <strong>and</strong> is the<br />
3<br />
density of the medium in grams/cm . The dose rate at the<br />
surface of the mass is one half the value given by this<br />
relation. In such a large mass, the relative beta <strong>and</strong> gamma<br />
dose rates are in the ratio of the average energies released<br />
per disintegration.<br />
2<br />
6. The surface dose rate through 7 mg / cm from a uniform<br />
2<br />
thin deposition of 1 Ci / cm is about 9 rads/h (90 mGy/h)<br />
for energies above about 0.6 MeV. Note that in a thin layer,<br />
the beta dose rate exceeds the gamma dose rate for equal<br />
energies released by ~100.<br />
Page 126<br />
RULES OF THUMB FOR BETA PARTICLES<br />
1. Beta particles of at least 70 keV energy are required to<br />
penetrate the nominal protective layer of the skin.<br />
2. The average energy of a beta-ray spectrum is approximately<br />
one-third the maximum energy.<br />
3. The range of beta particles in air is ~12 ft (3.6 m) / MeV.<br />
4. The range of beta particles (or electrons) in grams / cm 2<br />
3<br />
(thickness in cm multiplied by the density in g / cm ) is<br />
approximately half the maximum energy in MeV. This rule<br />
overestimates the range for low energies (0.5 MeV) <strong>and</strong> low<br />
atomic numbers, <strong>and</strong> underestimates for high energies <strong>and</strong><br />
high atomic numbers.<br />
5. The exposure rate in rads per hour in an infinite medium<br />
uniformly contaminated by a beta emitter is 2.12 EC / <br />
where E is the average beta energy per disintegration in<br />
3<br />
MeV, C is the concentration in ìCi / cm , <strong>and</strong> is the density<br />
3<br />
of the medium in grams/cm . The dose rate at the surface<br />
of the mass is one half the value given by this relation. In<br />
such a large mass, the relative beta <strong>and</strong> gamma dose rates<br />
are in the ratio of the average energies released per<br />
disintegration.<br />
2<br />
6. The surface dose rate through 7 mg / cm from a uniform<br />
2<br />
thin deposition of 1 Ci / cm is about 9 rads/h (90 mGy/h)<br />
for energies above about 0.6 MeV. Note that in a thin layer,<br />
the beta dose rate exceeds the gamma dose rate for equal<br />
energies released by ~100.<br />
Page 126