Isotope Data and Safety Considerations
Calcium-45 (45Ca)
Max beta energy: 0.257 MeV (100%)
Max range in air: 52 cm (20.5 inches)
Max range in water: 0.62 mm
Shielding: 1 cm Lucite
Effective half-life: 162d
Radioactive half-life: 162.7d
Monitoring: G-M detector
Considerations
Millicurie quantities of 45Ca do not present a significant external exposure hazard because the low energy betas emitted barely penetrate gloves and the outer skin layer. The critical organ of uptake of 45Ca is the bone. The majority of 45Ca is deposited in the bone and is retained with a long biological half-life. A smaller fraction is rapidly eliminated. 45Ca is initially eliminated via the urine but eventually, half the radionuclide is eliminated via the feces.
Carbon-14 (14C)
Max beta energy: 0.156 MeV (100%)
Max range in air: 24 cm (9.5 inches)
Max range in water: 0.28 mm
Shielding: 1 cm Lucite (3 mm effective but has poor mechanical properties)
Effective half-life: 12d
Radioactive half-life: 5730y
Monitoring: liquid scintillation counter
Considerations
Millicurie quantities of 14C do not present a significant external exposure hazard because the low-energy betas emitted barely penetrate the outer skin layer. The critical organ for uptake of many 14C-labeled carbonates is the bone and, for many other 14C-labeled compounds, fat. Most 14C-labeled compounds are rapidly metabolized and the radionuclide is exhaled as 14CO2. Some compounds and their metabolites are eliminated via the urine. Biological half-lives vary from a few minutes to 25 days.
Some 14C-labeled compounds may penetrate gloves and skin; therefore, handle those compounds remotely, wear two pairs of gloves and change the outer layer frequently. Be especially cautious when handling 14C-labeled halogenated acids. Since these compounds may be incorporated in the skin, local dose commitments are in the order of 10-100 rad per μCi deposited.
Cesium-137 (137Cs)
Max beta energy: 1.174 MeV (5.4%)
Max intensity: 0.512 MeV (94.6%)
Gamma radiation: 0.662 MeV (85.1%)
Ba K x-rays: 35 keV (7%)
Shielding: 2.54 cm (0.1 inch) lead reduces exposure 90 percent
Effective half-life: 70d
Radioactive half-life: 30.2y
Monitoring: ϒ- or x-ray probe; G-M detector
Considerations
Unshielded exposure rate from 1 mCi point source at 1 meter is 0.32 mR/hr. Routine biological monitoring via the urine recommended. Maximum permissible concentration in air 6 x 10-8 μCi/ml.
Chromium-51 (51Cr)
Gamma radiation: 320 keV (9.8%)
X-rays: 5 keV (22.3%)
Auger Electrons: 4 keV (66.9%)
Shielding: 1.7 mm (HVL for lead)
Effective half-life: 27d
Radioactive half-life: 27.7d
Monitoring: scintillation detector
Considerations
Unshielded exposure rate from 1 mCi point source at 1 cm is 0.18 R/hr. The lower large intestine is the critical organ for intake of soluble 51Cr compounds and ingestion of insoluble compounds. The lung is the critical organ for inhalation of insoluble compounds. Uptake of 51Cr is slowly eliminated from the body via urine and feces.
Cobalt-57 (57Co)
Gamma radiation: 14 keV (9.5%), 122 keV (85.5%), 136 keV (10.8%), 570 keV (0.01%), 692 keV (0.16%), (others low intensity).
Fe K x-rays: 6.7 keV (55%)
Mode of decay: electron capture
Shielding: 3.2 mm (0.13 inches) lead reduces exposure 90 percent
Effective half-life: 9d
Radioactive half-life: 270.9d
Monitoring: y- or x-ray probe, G-M detector
Considerations
Unshielded exposure rate from 1 mCi point source at 1 m is 8.9 x 10-2 mR/hr. The critical organ is the lower large intestine. Routine monitoring via the urine. Maximum permissible concentration in air is 3 x 10-6 μCi/ml.
Hydrogen-3 (3H or Tritium)
Max beta energy: 0.019 MeV (100%)
Max range in air: 6 mm (0.24 inches)
Max range in water: 0.006 mm
Shielding: none
Physical half-life: 12.4y
Effective half-life: 12d
Monitoring: liquid scintillation counter
Considerations
Millicurie quantities of tritium do not present an external exposure hazard because the low energy betas emitted cannot penetrate the outer layer of skin. The critical organ for tritium uptake is the whole body. Three to four hours after intake, tritiated water is uniformly distributed in all body water. On average, tritiated water is eliminated within a 10-day biological half-life. Elimination rates may be increased by increasing water intake.
Special Precautions
Tritium cannot be monitored directly because of its low beta-energy. Therefore, good housekeeping is very important. Many tritium compounds readily penetrate gloves and skin due to the solvency of the carrier. Handle those compounds remotely, wear two pairs of gloves, and change the outer layer at least every twenty minutes. Tritiated DNA precursors are considered more toxic than tritiated water. However, they are generally less volatile and do not normally present a significantly greater risk.
Iodine-125 (125I)
Gamma radiation: 35 keV 7% emitted, 93% internally converted
Te K x-rays: 27-32 keV (140%)
Radioactive half-life: 59.6d
Effective half-life: 42d
Shielding: 0.02 mm (HVL for lead)
Monitoring: scintillation detector, G-M detector
Considerations
Unshielded exposure rate from 1 mCi point source at 1 cm is 1.4 R/hr. Volatilization of iodine is the most significant problem with this isotope. Formation of aerosols when opening vial of iodinated compounds is a hazard. The thyroid is the critical organ for 125I (30 percent accumulation). Although individual metabolisms vary, 125I can be assumed eliminated via the urine. A reasonably conservative biological half-life for 125I in the thyroid is 138 days.
Special Precautions
- Store mCi quantities at about 23ºC in containers surrounded by 1/8 inch thick lead.
- Use tools to prevent direct handling of unshielded mCi sources.
- Wear two pairs of gloves, monitor frequently and change the outer pair as necessary.
Phosphorus-32 (32P)
Max beta energy: 1.71 MeV (100%)
Max range in air: 790 cm (26 feet)
Max range in water: 0.86 mm
Shielding: 0.95 cm Lucite
Radioactive half-life: 14.3d
Effective half-life: 14d
Monitoring: liquid scintillation counter, G-M detector
Considerations
Unshielded exposure rate from 1.6 mCi in 1 ml at the surface is 21 rem/hr. The bone is the critical organ for intake of transportable compounds of 32P. Phosphorus metabolism is complex, with 30% being rapidly eliminated from the body, 40% possessing a 19-day biological half-life, and the remaining 30% being eliminated by radioactive decay. The lung and lower large intestine are the critical organs for inhalation and ingestion of nontransportable 32P compounds.
Special Precautions
- Use shielding to minimize exposure while handling and storing 32P.
- Wear extremity and whole body dosimeters while handling mCi quantities of 32P.
- Do not work over an open container. Use tools to handle indirectly unshielded sources and potentially contaminated vessels.
Phosphorus-33 (33P)
Max beta energy: 0.249 MeV (100%)
Max range in air: 49 cm (19 inches)
Max range in water: 0.6 mm
Radioactive half-life: 25.4d
Effective half-life: 25d
Shielding: 1 cm Lucite (3 mm effective but has poor mechanical properties)
Monitoring: liquid scintillation counter, G-M detector
Considerations
Millicurie quantities of 33P do not present a significant external exposure hazard because the low energy betas emitted barely penetrate gloves and the outer skin layer. The bone is the critical organ for intake of transportable compounds of 33P. Phosphorus metabolism is complex, with 30% being rapidly eliminated from the body, 40% possessing a 19-day biological half-life, and the remaining 30% being eliminated by radioactive decay. The lung and lower large intestine are the critical organs for inhalation and ingestion of nontransportable 33P compounds.
Sodium-22 (22Na)
Max beta(+) energy: 0.545 MeV
Gamma-radiation 0.511 MeV (180%), 1.275 MeV (100%)
Max range in air: 49 cm (19 inches)
Max range in water: 0.6 mm
Shielding: 0.95 cm Lucite for beta; 0.7 cm (Half-value layer for lead)
Radioactive half-life: 2.6y
Effective half-life: 11d
Monitoring: y- or b-probe, G-M detector
Considerations
Unshielded exposure rate from 1 mCi point source at 1 meter is 1.20 mR/hr. The critical organ is the whole body. Body burden of 10 μCi whole body. Routine monitoring via the urine. Maximum permissible concentrations in the air are 2.0 x 10-7 μCi/ml.
Special Precautions
- Shielding is required whenever small quantities are in use. Use shielding sufficient to stop beta+ radiation (e.g., 1 cm Plexiglas). For larger quantities, 2.54 cm of lead will reduce the gamma intensity by a factor of ten.
- The mode of decay is positron emission. When a positron undergoes annihilation, 2 gamma rays at 511 keV are produced. Otherwise, beta+ particles have a radiological hazard similar to beta- particles of the same energy.
Sulfur-35 (35S)
Max beta energy: 0.167 MeV (100%)
Max range in air: 26 cm (10 inches)
Max range in water: 0.32 mm
Radioactive half-life: 87.4d
Effective half-life: 76d
Shielding: 1 cm Lucite (3 mm effective but has poor mechanical properties)
Monitoring: liquid scintillation counter, G-M detector
Considerations
Millicurie quantities of 35S do not present a significant external exposure hazard since the low energy emissions barely penetrate the outer layer of skin. The critical organ for 35S is the whole body. The elimination rate of 35S depends on the chemical form; however, most 35S labeled compounds are eliminated via the urine, 90 days being an acceptably conservative biological half-life.
Special Precautions
35S may be difficult to distinguish from 14C because the beta emissions are of similar energy. If both radioisotopes are being used in the same area, establish controls which are conservative for both radioisotopes.
Uranium Isotopes
| Isotope | Half-Life | Natural Abundance (%) | Specific Activity (Ci/g) | Primary Decay Mode | Radiation Energy | ||
|---|---|---|---|---|---|---|---|
| Alpha (α) | Beta (β) | Gamma (γ) | |||||
| U-232 | 72 yr | 0 | 22 | α | 5.3 | 0.017 | 0.0022 |
| U-233 | 160,000 yr | 0 | 0.0098 | α | 4.8 | 0.0061 | 0.0013 |
| U-234 | 240,000 yr | 0.0055 | 0.0063 | α | 4.8 | 0.013 | 0.0017 |
| U-235 | 700 million yr | 0.72 | 0.0000022 | α | 4.4 | 0.049 | 0.16 |
| Th-231* | 26 hr | 540,000 | β | 0.17 | 0.026 | ||
| U-236 | 23 million yr | 0 | 0.000065 | α | 4.5 | 0.011 | 0.0016 |
| U-238 | 4.5 billion yr | >99 | 0.00000034 | α | 4.2 | 0.10 | 0.0014 |
| Th-234* | 24 days | 23,000 | β | 0.060 | 0.0093 | ||
| Pa-234m* | 1.2 min | 690,000,000 | β | 0.82 | 0.012 | ||
* Properties of thorium-231, thorium-234, and protactinium-234m are included here because these radionuclides accompany the Uranium decays. Source: Argonne National Laboratory, EVS-HHFS, August 2005
Research activities can involve the use of natural, enriched, or depleted uranium. Natural isotopes of uranium are U-238, U235, and U-234 (see table above for natural abundances). Depleted uranium contains less of the isotopes U-235 and U-234. The specific activity of depleted uranium (5.0E-7 Ci/g) is less than that of natural uranium (7.1E-7 Ci/g). Certain uranium compounds, such as mass spectroscopy standards, uranyl acetate, and uranyl nitrate, may be acquired in small quantities without RSC approval.
Uranium can pose a slight external hazard mainly from low-energy gamma and beta radiation when directly handling the material (potential skin effects). Uranium is primarily an alpha particle emitter, as well as a toxic heavy metal. Therefore, internal exposure through ingestion, inhalation, or injection through wounds is of primary concern. The bone surfaces and kidneys are the critical organs for internal exposure and toxicity to the kidney may be of greater concern than the radiation dose to bone surfaces for ingestion of soluble forms of uranium.
Intake Data (annual for natural uranium)
Ingestion
20.0 μCi equals 5 rem TEDE (WHOLE BODY)
10.0 μCi equals 50 rem CEDE (BONE SURF)
Inhalation
2.0 μCi equals 5 rem TEDE (WHOLE BODY)
1.0 μCi equals 50 rem CEDE (BONE SURF)
Survey Meters
A survey meter is required to work with uranium. A thin window Geiger-Mueller tube or thin window NaI detector is necessary to detect uranium.
Recommended Protective Clothing/Practices
When working with unsealed sources wear appropriate protective clothing such as laboratory coats, gloves, and safety glasses/goggles. A suitable fume hood should be used if the radioactive material is in the form of dust, powder, or if it is potentially volatile.
Technetium-99 (99Tc)
Max beta energy: 0.294 MeV (100%)
Max range in air: 63 mm (25 inches)
Shielding: none
Physical half-life: 2.13 x 105y
Monitoring: liquid scintillation counter, G-M detector
Considerations
Millicurie quantities of 99Tc do not present a significant external exposure hazard because the low energy betas emitted barely penetrate gloves and the outer dead layer of skin. It may be assumed that technetium is retained in the transfer compartment with a biological half-life of 0.02 days. 4% of technetium leaving the transfer compartment is transferred to the thyroid where it is retained with a biological half-life of 0.5 days. 10%, 3%, and 83% of technetium leaving the transfer compartment are translocated to the stomach wall, liver and all other organs and tissues of the body, respectively; and 75%, 20%, and 5% of technetium in all organs and tissues, except the thyroid, retained with biological half-lives of 1.6, 3.7 and 22 days, respectively.
Intake Data (annual)
Ingestion
4 mCi equals 5 rem TEDE (WHOLE BODY)
Inhalation
700 μCi equals 5 rem TEDE (WHOLE BODY)
Recommended Protective Clothing/Practices
When working with unsealed sources wear appropriate protective clothing such as laboratory coats (which must be monitored before leaving the laboratory) coveralls, gloves, safety glasses/goggles. A suitable fume hood should be used if the radioactive material is in the form of dust, powder, or if it is potentially volatile.
Thorium Isotopes
As thorium-232 undergoes radioactive decay, it emits an alpha particle, with accompanying gamma radiation, and forms radium-228. This process of releasing radiation and forming a new radionuclide continues until stable lead-208 is formed. The half-life of thorium-232 is about 14 billion years. Two other isotopes of thorium, which can be significant in the environment, are thorium-230 and thorium-228. Both decay by alpha emission, with accompanying gamma radiation, in 75,400 years and 1.9 years, respectively.
Intake Data (Thorium-232, annual)
Ingestion
2 μCi equals 5 rem TEDE (WHOLE BODY)
Inhalation
0.003 μCi equals 5 rem TEDE (WHOLE BODY)
Survey Meters
A thin window Geiger-Mueller tube or liquid scintillation detector is necessary to detect uranium. Note: Lantern mantels impregnated with thorium salts typically have an activity of 0.02 μCi and are often used as check sources for Geiger-Mueller counters.
Considerations
The primary hazard with thorium isotopes is toxic effects associated with ingestion or inhalation. When using unsealed sources of thorium use standard laboratory procedures (protective gloves, lab coat, goggles). A suitable fume hood should be used if the radioactive material is in the form of dust, powder, or if it is potentially volatile.
Radium-226 (226Ra)
Alpha energy: 4601 keV (5.5%), 4784 kev (94.5%)
Gamma energy: 11.7 kev (0.8%), 81.0 kev (0.81%), 83.8 kev (0.23%), 94.9 kev (0.14%), 186 kev (3.28%), 309 kev (0.007%)
Radioactive half-life: 1600 years
Effective half-life: 41.096 years
Shielding: HVL Lead: 0.04 cm
Monitoring: liquid scintillation counter, G-M detector
Intake Data (annual)
Ingestion
5 μCi equals 5 rem TEDE (WHOLE BODY)
2 μCi equals 50 rem CEDE (BONE SURF)
Inhalation
0.6 μCi equals 5 rem TEDE (WHOLE BODY)
Doses
Skin Dose: Reported for 1 μCi over 10 cm2 of skin equals 0.217 mrad/hr (gamma dose)
Protective Measures
Critical Organs
Bone tissue
Exposure Routes
Ingestion, inhalation, puncture, wound, skin contamination/absorption
Hazards
Long-term exposure (inhalation or ingestion) to radium increases the risk of developing diseases such as lymphoma, bone cancer, leukemia, and aplastic anemia.
Recommended Protective Clothing/Practices
When working with unsealed sources wear appropriate protective clothing such as laboratory coats (which must be monitored before leaving the laboratory) coveralls, gloves, safety glasses/goggles. A suitable fume hood should be used if the radioactive material is in the form of dust, powder, or if it is potentially volatile.