Shielding Isotopes

Hydrogen-3

Hydrogen-3 is a commonly used radionuclide with a half-life of 12.3 years, emitting only beta particles with a maximum energy of 0.019 Mev (Million Electron Volts) and an average energy of 0.0057 MeV. The beta particles from 3H travel a maximum of 6mm. in air.

CONCERNS
The major concern with using H-3 is that it cannot be easily monitored during it's use, therefore, special precautions are needed to keep the work environment clean. The regular use of wipe testing is the only way to insure that your work space is not contaminated. Contamination on the skin will not likely cause a significant dose to the dead layer of skin, however, it could lead to the internal absorption of H-3.

SHIELDING
Glass and plastic are the best shields for beta particles from H-3 Lucite.

DETECTION
A tiny drop of contamination containing H-3 can be easily detected with a wipe
test from a liquid scintillation counter. A Geiger counter will not detect the presence of H-3.

Carbon-14

Carbon-14 is a commonly used radionuclide with a half-life of 5,730 years, emitting only beta particles with a maximum energy of 0.156 MeV (Million Electron Volts) and an average energy of 0.049 MeV. The beta particles from C-14 travel a maximum of 22 cm.

CONCERNS
The major concern with using C-14 is that it cannot be easily monitored during it's use, therefore, special precautions are needed to keep the work environment clean. The regular use of wipe testing is the only way to insure that your work space is not contaminated. Contamination on the skin will not likely cause a significant dose to the dead layer of skin, however, it could lead to the internal absorption of C-14.

SHIELDING
Glass and plastic are the best shields for particles from C-14 Lucite.

DETECTION
A tiny drop of contamination from C-14 can be easily detected with a wipe test from a Liquid Scintillation Counter. Most Geiger Counters will not efficiently detect the presence of C-14.

Phosphorus-32

Phosphorus-32 is a commonly used radionuclide with a half-life of 14.3 days, emitting beta particles with maximum energy of 1.71 MeV. The beta particles can travel a maximum of 20 feet in air.
CONCERNS
The major concerns with using P-32 are:

Surface radiation exposure to the skin of the hands. A drop of contamination containing 1 microcurie of P-32 on 1 cm2 area of the skin produces an exposure of 2,000 millirems/hr.
Radiation exposure in air over an open vial continuing 1 millicurie of 32P can be as high as 26,000 millirems per hour.
Working with P-32 orthophosphate in high concentrations poses significant problems because of the large activity and high concentrations (i.e., 5 millicuries in 10 lambda). If you can avoid using them, please do so.

SHIELDING
Plexiglass (lucite) is the best shield for beta particles from P-32. When more than 1 millicurie of P-32 is handled, a sufficient number of x-rays (bremmstrahlung) may be formed to require Lead foil to be added to the exterior of the shield. The beta particles travel a maximum of 3.1 mm. in glass, 6.7 mm. in lucite, and 8mm in tissue. You may order from the following web address: Lucite

DETECTION
A tiny drop of contamination of P-32 can be easily detected with Geiger Counter.

Sulfur-35

Sulfur-35 is a commonly used radionuclide with a half-life of 87.4 days, emitting only beta particles with a maximum energy of 0.167 MeV (Million Electron Volts) and an average energy of 0.049 MeV. The beta particles from S-35 Travel a maximum of 24 cm. in air. The above properties are very similar to those of C-14.

CONCERNS
The major concern with using S-35 is that it's presence cannot be monitored during it's use, since most Geiger Conters will not be able to detect S-35. Special precautions are needed to keep the work environment clean. The regular use of wipe testing is the only way to insure that your work space is not contaminated. Contamination on the skin will not likely cause a significant dose to the dead layer of skin. The maximum permissible body burden for S-35 set by the NRC for the whole body is 400 microcuries.

SHIELDING
Glass and plastic are the best shields for beta articles from S-35. Plastic

DETECTION
A tiny drop of contamination from S-35 can be easily detected with a wipe test from a Liquid Scintillation Counter. If using a Geiger counter, make very slow sweeps across the possible contaminated area. Place the probe as close as possible to the contaminated area without coming into contact with the contamination.

Phosphorus-33

Phosphorus-33 is becoming more commonly used radionuclide with a half-life of 25.4 days, emitting only beta particles with a maximum energy of 0.249 MeV and an average energy of 0.083 MeV. The beta particles from P-33 travel a maximum of 46 cm in air.

CONCERNS
The major concern with using P-33 is that it cannot be easily monitored during it's use, therefore, special precautions are needed to keep the work environment clean. The regular use of wipe testing is the only way of insure that your work space is not contaminated. Contamination on the skin will not likely cause a significant dose to the dead layer of skin, however, it could lead to the internal absorption of P-33.

SHIELDING
Glass and plastic are the best shields for beta particles from P-33. Lucite

DETECTION
A tiny drop of contamination from P-33 can be easily detected with a wipe test from a Liquid Scintillation Counter. Most Geiger Counters will not efficiently detect the presence of P-33.

Chromium-51

Chromium-51 is a commonly used radionuclide with a half-life of 27.7 days, emitting gamma rays with a maximum energy of 0.320 MeV (Million Electron Volts) and X-rays with a maximum of 5 KeV (Thousand Electron Volts.)

CONCERNS
The major concern with using Cr-51 is radiation exposure in air over an unshielded vial. The dose rate at the opening of an unshielded vial containing 1 millicurie of Cr-51 can be 180 millirems per hour.

One millicurie=2.22 x 109 dpm (disintegrations per minute) This means that the quarterly NRC limit of 18,250 millirems for the hands would be reached in 101 hours.

SHIELDING
Lead foil or lead bricks are the best shields for gamma rays from Cr-51. The half value layer for Cr-51 gamma rays in Lead is 1.7mm., i.e. every 1.7 mm. of Lead reduces the Cr-51 gamma ray beam by 50%. You may order foil from the following web address: Lead Foil or Lead Bricks

DETECTION
A tiny drop of contamination containing Cr-51 can be easily detected with a Geiger Counter.

Iodine-125

Iodine-125 is a commonly used radionuclide with a half-life of 60 days, emitting gamma rays with a maximum energy of 0.035 MeV and X-rays with a maximum of 31 KeV (Thousand Electron Volts.)

CONCERNS
The major concern with using I-125 is Radiation exposure in air over an unshielded vial. The dose rate at the opening of an unshielded vial containing 1 millicurie of I-125 can be 1,400 millirems per hour. Unlabelled I-125 is very volatile in air and must be used in a fume hood. When performing iodinations using millicurie amounts, a thyroid check must be performed by the RSO within 72 hours. Call the Radiation Safety Department.

SHIELDING
Lead foil is the best shield for gamma rays from I-125. The half value layer for I-125 gamma rays in Lead is 0.02 mm., i.e. every 1.7 mm. of Lead reduces the I-125 gamma ray beam by 50%. Lead Foil

DETECTION
A small drop of contamination containing I125 can be easily detected with a Sodium Iodide Detector.