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Office of Homeland Security & Emergency Coordination
Radiation Safety Division (RSD)
United States Department of Agriculture

Radionuclide Characteristics

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Tritium (H-3)

Tritium (H-3) has an atomic number of 1 and a half-life of 12.7 years. It is a low energy 0.019 Mev (max) beta emitter. The emitted beta radiation cannot penetrate the outer layer of dead skin. There is no external exposure hazard and no required shielding. Internal uptake is the primary concern. The critical organ is the whole body. The annual limit on intake ( ALI) is 80 milli-Curies for oral ingestion and for inhalation.

DOT limit for limited quantity varies depending on the compound and concentration.

DOT A2 limit in normal form per Type-A package: 1,000 Curies

Tritium is used in a chemistry laboratory setting as a radiolabel. It has the advantage that hydrogen appears in almost all organic chemicals making it easy to find a place to put tritium on the molecule under investigation.

 

Carbon (C-14)

Carbon (C-14) has an atomic number of 6 and a half-life of 5,730 years. It is a low energy 0.156 Mev (max) beta emitter. The low energy beta particles penetrate protective gloves and the outer layer of skin. Plastic shielding of any thickness is recommended to absorb all beta particles. There is no significant external exposure hazard. Internal uptake is the primary concern. The critical organ is the bone for carbonates and body fat for many other compounds. The annual limit on intake ( ALI) for compounds is 2 milli-Curies for oral ingestion and for inhalation.

DOT limit for limited quantity in liquid form per exempt package: 8 milli-Curies

DOT A2 limit in normal form per Type-A package: 80 Curies

 

Phosphorus (P-32)

Phosphorus (P-32) has an atomic number of 15 and a half-life of 14 days. It is a high energy 1.709 Mev (max) beta emitter. Phosphorus (P-32) poses an external radiation hazard. Do not use lead shielding, since the high energy beta radiation will produce even more hazardous bremsstrahlung x-rays. The recommended shielding is a plastic or plexi-glass shield, 1 centimeter thick. The bone is the critical organ for uptake. The annual limit on intake ( ALI) is 600 micro-Curies for oral ingestion and 900 micro-Curies for inhalation.

DOT limit for limited quantity in liquid form per exempt package: 1.4 milli-Curies

DOT A2 limit in normal form per Type-A package: 14 Curies

 

Phosphorus (P-33)

Phosphorus (P-33) has an atomic number of 15 and a half-life of 25 days. It is a low energy 0.249 Mev (max) beta emitter. Plastic shielding of any thickness is recommended to absorb all beta particles. There is no significant external exposure hazard. Internal uptake is the primary concern. The bone is the critical organ for uptake. The annual limit on intake ( ALI) is 6 milli-Curies for oral ingestion and 8 milli-Curies for inhalation.

DOT limit for limited quantity in liquid form per exempt package: 2.7 milli-Curies

DOT A2 limit in normal form per Type-A package: 27 Curies

 

Sulfur (S-35)

Sulfur (S-35) has an atomic number of 16 and a half-life of 87 days. It is a low energy 0.167 Mev (max) beta emitter. Plastic shielding of any thickness is recommended to absorb all beta particles. There is no significant external exposure hazard. Internal uptake is the primary concern. The critical organ is the whole body. The annual limit on intake ( ALI) for most compounds is 10 milli-Curies for oral ingestion and 20 milli-Curies for inhalation.

Sulfur (S-35) amino acids can decompose to volatile compounds during storage. Always open stock vials in an operating chemical fume hood. Incubation of S-35 methionine may release volatile compounds. The incubator may become contaminated.

DOT limit for limited quantity in liquid form per exempt package: 8.1 milli-Curies

DOT A2 limit in normal form per Type-A package: 80 Curies

 

Calcium (Ca-45)

Calcium (Ca-45) has an atomic number of 20 and a half-life of 163 days. It is a low energy 0.257 Mev (max) beta emitter. Plastic shielding of any thickness is recommended to absorb all beta particles. There is no significant external exposure hazard. Internal uptake is the primary concern. Internal uptake is the primary concern. The critical organ is the bone. The annual limit on intake ( ALI) is 2 milli-Curies for oral ingestion and 80 micro-Curies for inhalation.

DOT limit for limited quantity in liquid form per exempt package: 2.7 milli-Curies

DOT A2 limit in normal form per Type-A package: 27 Curies

 

Cobalt (Co-60)

The element, Cobalt, is a hard, lustrous, silver-gray metal. Cobalt (Co-60) has an atomic number of 27 and a half-life of 5.3 years. It is a synthetic radioactive isotope that emits gamma radiation. It is produced artificially by neutron activation of Cobalt (Co-59). Cobalt (Co-60) is an external radiation hazard. It emits a 318 keV beta particle, and it emits gamma rays of 1.17 and 1.33 MeV. The dose-rate of Cobalt (Co-60) is 13.2 rads per hour at 1 centi-meter from 1 milli-Curie of Cobalt (Co-60). One centi-meter of lead is recommended to reduce the radiation by one-half. The critical organs of concern for internal uptake are the liver, kidney, and bone. The annual limit on intake (ALI) is 200 micro-Curies for oral ingestion and 30 micro-Curies for inhalation.

DOT limit for limited quantity in solid form per exempt package: 11 milli-Curies

DOT A1 limit in special form and A2 limit in normal form per Type-A package: 11 Curies

 

Nickel (Ni-63)

Nickel (Ni-63) has an atomic number of 28 and a half-life of 100.1 years. It is a low energy 0.066 Mev (max) beta emitter. The emitted beta radiation cannot penetrate the outer layer of dead skin. There is no external exposure hazard and no required shielding. Internal uptake is the primary concern. Internal uptake is the primary concern. The annual limit on intake ( ALI) is 9 milli-Curies for oral ingestion and 0.8 milli-Curies for inhalation.

DOT limit for limited quantity in solid form per exempt package: 811 milli-Curies

 

Iodine (I-125)

Iodine (I-125) has an atomic number of 53 and a half-life of 60 days. It is an external radiation hazard. It emits gamma rays of 35 keV and x-rays of 27 to 32 keV.

The dose-rate of Iodine (I-125) is 1.4 rads per hour at 1 cm from 1 milli-Curie of Iodine (I-125) . One milli-meter of lead foil is recommended to reduce the radiation by 99%. The thyroid is the critical organ for uptake. The annual limit on intake ( ALI) for the thyroid is 40 micro-Curies for oral ingestion and 60 micro-Curies for inhalation.

Store NaI solutions at room temperature to minimize volatilization of compounds. Avoid acidic solutions.

DOT limit for limited quantity in liquid form per exempt package: 80 micro-Curies

DOT A2 limit in normal form per Type-A package: 800 Curies

 

Cesium (Cs-137)

Cesium (Cs-137) is a radioactive isotope of cesium, which is a product of nuclear fission. It has an atomic number of 55 and a half-life of 30.2 years. It emits a beta particle, and it also emits 662 kev gamma rays. Cesium (Cs-137) is an external radiation hazard. The dose-rate of Cesium (Cs-137) is 3.3 rads per hour at 1 centi-meter from 1 milli-Curie of Cesium (Cs-137). One-half centi-meter of lead is recommended to reduce the radiation by one-half.

The element, cesium, is quite chemically reactive, making it difficult to handle. Also, the salts of cesium are very soluble in water, and this complicates its safe handling.

Upon ingestion, cesium is uniformly distributed throughout the body, with higher concentration in muscle tissues, and lower concentrations in the bones. The annual limit on intake (ALI) is 100 micro-Curies for oral ingestion and 200 micro-Curies for inhalation.

DOT limit for limited quantity in liquid form per exempt package: 1.6 milli-Curies

DOT limit for limited quantity in solid form per exempt package: 16 milli-Curies

DOT A2 limit in normal form per Type-A package: 16 Curies

DOT A1 limit in special form per Type-A package: 54 Curies

 

Americium (Am-241)

Americium is a synthetic element that is produced by bombarding uranium or plutonium with alpha particles in a nuclear reactor. Americium (Am-241) has an atomic number of 95 and a half-life 432 years. It emits alpha particles of 5 different energies, mostly at 5.486 MeV (85.2%) and 5.443 MeV (12.8%); it also emits low energy gamma-rays (often considered x-rays) with discrete energies between 26.3 and 158.5 keV. When combined with beryllium, it is an efficient neutron source, where americium acts as the alpha source, and beryllium produces neutrons. For plain Americium (Am-241), internal uptake is the primary concern. The critical organs are the liver, bone, and the gonads. The annual limit on intake ( ALI) for compounds is 0.8 micro-Curies for oral ingestion and 0.006 micro-Curies for inhalation. For the americium-beryllium neutron source, the neutron radiation is an external radiation hazard.

DOT A1 limit of Americium (Am-241) / Be in special form per Type-A package: 270 Curies