APPENDIX B: The Characteristics of Common Radioisotopes

This section provides useful information, including physical characteristics, shielding needs, handling precautions and waste disposal information for the six radioisotopes most commonly used at Princeton University:

• H-3

• C-14
  

• P-32

• Si-32

• P-33
  

• S-35

• Fe-55

• Co-57

• Fe-59

• Ni-63

• Zn-65

• Se-75

• Cd-109

• I-125

• Hg-203

For information about other radioisotopes, contact Environmental Health & Safety (EHS).

*Annual Limit on Intake

**Unless handling tens of millcuries

***LSC: Liquid Scintillation Counting

G-M: Geiger-Muller Counting

NaI: Sodium iodide scintillation survey metet

g: gamma counter

Hydrogen-3

Physical Characteristics:

• Half-life: 12.3 years
• Emissions: Beta particles with a maximum energy of 18.6 keV and an average energy of 5.7 keV.
• Maximum Range: 4.7 mm in air; 0.006 mm in tissue
• Fraction transmitted through the dead layer of the skin: none

Dose and Shielding:

• Dose rate to the skin at 10 cm: None
• Dose rate to epidermal basal cells from skin contamination of 1 mCi/cm2: None
• Shielding: None needed.
• Annual Limit on Intake (ALI): 80 millicuries via ingestion, assuming intake as tritiated water. The ingestion of one ALI will produce a dose of 5 rem.

Detection:

Liquid scintillation counting is the preferred method for detecting H-3. Most G-M detectors will not detect the presence of H-3.

Precautions:

H-3 contamination cannot be detected with a G-M meter, and special precautions are needed to keep the work environment clean. The regular use of wipe testing, using a liquid scintillation counter, is the only way to insure that your work space does not contain contamination.

Waste Disposal:

• Solid Wastes/Liquid Scintillation Wastes: through the Off-Site Radioactive Waste Disposal Program
• Liquid Wastes: through the Sewer Disposal Program. The monthly secondary disposal limit is 3 mCi.

Carbon-14

Physical Characteristics

• Half-life: 5,730 years
• Emissions: Beta particles with a maximum energy of 156 keV and an average energy of 49 keV.
• Maximum Range: 22 cm in air; 0.027 cm in tissue
• Fraction transmitted through the dead layer of the skin: 0.11

Dose and Shielding:

• Dose rate to the skin at 10 cm: 600 mrad/hour/mCi
  (for an unshielded point source)
• Dose rate to epidermal basal cells
  from skin contamination of 1 mCi/cm2: 1400 mrad/hour
• Shielding: None needed, when used in millicurie quantities under normal laboratory conditions.
• Annual Limit on Intake (ALI): 2 millicuries via ingestion. The ingestion of one ALI will produce a dose of 5 rem.

Detection:

Liquid scintillation counting is the preferred method for detecting C-14. Most G-M detectors are not likely to detect the presence of C-14 in amounts less than about 100,000 dpm (0.05 µCi).

Precautions:

Low-level C-14 contamination cannot be easily detected with a G-M meter, and special precautions are needed to keep the work environment clean. The regular use of wipe testing, using a liquid scintillation counter, is the only way to insure that your work space does not contain low-level removable contamination.

Waste Disposal:

• Solid Wastes/Liquid Scintillation Wastes: through the Off-Site Radioactive Waste Disposal Program
• Liquid Wastes: through the Sewer Disposal Program. The monthly secondary disposal limit is 3 mCi.

Phosphorus-32

Physical Characteristics:

• Half-life: 14.3 days
• Emissions: Beta particles with a maximum energy of 1.71 MeV and an average energy of 0.7 MeV.
• Maximum Range: 620 cm in air; 0.8 cm in tissue; 0.6 cm in plexiglas
• Fraction transmitted through the dead layer of the skin: 0.95

Dose and Shielding:

• Dose rate to the skin at 10 cm: 4070 mrad/hour/mCi
  (for an unshielded point source)
• Dose rate to epidermal basal cells from skin contamination of 1 mCi/cm2: 9200 mrad/hour
• Shielding: 3/8” plexiglas/lucite will shield all P-32 betas. For high activity sources exceeding a few millicuries, it may be desirable to add lead shielding outside the plexiglas shielding to shield against bremsstrahlung x-rays. Plexiglas should be placed closest to the P-32 source as primary shielding, and lead should be used outside the plexiglas as secondary shielding.
• Annual Limit on Intake (ALI): 600 microcuries via ingestion. The intake of one ALI will produce a dose of 5 rem.

Detection:

A G-M detector will readily detect low-level P-32 contamination, although liquid scintillation counting is also an acceptable method for detecting removable P-32 contamination.

Precautions:

High localized doses are possible while handling millicurie amounts of P-32 and as a result of skin contamination. Reduce doses by wearing safety glasses (for shielding the eyes), using remote handling tools such as tongs, using shielding extensively to shield storage and experimental containers and work areas, and performing thorough and frequent surveys of the work area, clothing and the body.

Waste Disposal:

• Solid Wastes: through the Decay-in-Storage Program.
• Liquid Wastes: through the Sewer Disposal Program. The monthly secondary disposal limit is 300 µCi.

Silicon-32

Physical Characteristics

• Half-life: 104 years
• Emissions: Beta particles with a maximum energy of 0.224 MeV and an average energy of 0.067 MeV. Since Si-32 decays to P-32, emissions from a Si-32 source also include the 1.71 MeV beta from P-32
• Maximum Range: 37 cm in air; <.05 cm in tissue.
• See the P-32 fact sheet for information about the properties of the beta from the P-32 progeny.

Dose and Shielding

Dose rate to the skin at 10 cm: See the P-32 fact sheet for information about the dose from the P-32 progeny.
Dose rate to epidermal basal cells from skin contamination of 1 µCi/cm2: See the P-32 fact sheet for information about the dose from the P-32 progeny.
Shielding: Depending on the age of the material, plexiglas shielding may be required for the P-32 progeny.
Annual Limit on Intake (ALI): 2000 microcuries via ingestion and 200 microcuries via inhalation. The intake of one ALI will produce a dose of 5 rem.

Detection

Liquid scintillation counting is the preferred method for detecting Si-32. Most G-M detectors are not likely to detect the presence of Si-32 in amounts less than about 100,000 dpm (0.05 µCi). However, if the sample is older than a week, it may be appropriate to use a G-M detector to detect the P-32 progeny.

Precautions

Appropriate precautions will depend on the age of the sample of Si-32. A sample of Si-32 will reach equilibrium with the P-32 progeny in approximately 120 days, i.e., a 1 mCi sample of Si-32 will also contain 1 mCi P-32 in 120 days. Within the first week, it is appropriate to take precautions based on the properties of Si-32. However, after that point, the sample will contain enough P-32, that precautions based on the properties of P-32 should be taken.

Low-level Si-32 contamination cannot be easily detected with a G-M meter, and special precautions are needed to keep the work environment clean. The regular use of wipe testing, using a liquid scintillation counter, is the only way to insure that the work space does not contain low-level removable contamination.

High localized doses are possible while handling millicurie amounts of P-32 and as a result of skin contamination. Reduce doses by wearing safety glasses (for shielding the eyes), using remote handling tools such as tongs, using shielding extensively to shield storage and experimental containers and work areas, and performing thorough and frequent surveys of the work area, clothing and the body.

Radiation Monitoring Requirements: Radiation monitoring badges may be required for Si-32 users, depending on the amount of Si-32 used.

Waste Disposal

Solid Wastes: through the Off-Site Radioactive Waste Disposal Program.

Liquid Wastes: through the Sewer Disposal Program. The monthly secondary disposal limit is 300 µCi.

Phosphorus-33

Physical Characteristics:

• Half-life: 25.3 days
• Emissions: Beta particles with a maximum energy of 249 keV and an average energy of 76 keV.
• Maximum Range: 45 cm in air; 0.06 cm in tissue
• Fraction transmitted through the dead layer of the skin: 0.35

Dose and Shielding:

• Dose rate to the skin at 10 cm: 2000 mrad/hour/mCi
  (for an unshielded point source)
• Dose rate to epidermal basal cells from skin contamination of 1 mCi/cm2: 4500 mrad/hour
• Shielding: None needed, when used in millicurie quantities or less, under normal laboratory conditions
• Annual Limit on Intake (ALI): 6 millicuries via ingestion. The intake of one ALI will produce a dose of 5 rem.

Detection:

Liquid scintillation counting is the preferred method for detecting P-33. Most G-M detectors are not likely to detect the presence of P-33 in amounts less than about 100,000 dpm (0.05 µCi).

Precautions:

Low-level P-33 contamination cannot be easily detected with a G-M meter, and special precautions are needed to keep the work environment clean. The regular use of wipe testing, using a liquid scintillation counter, is the only way to insure that the work space does not contain low-level removable contamination.

Waste Disposal:

• Solid Wastes: through the Decay-in-Storage Program.
• Liquid Wastes: through the Sewer Disposal Program. The monthly secondary disposal limit is 3 mCi.

Sulfur-35

Physical Characteristics:

• Half-life: 87.6 days
• Emissions: Beta particles with a maximum energy of 167 keV and an average energy of 49 keV.
• Maximum Range: 24 cm in air; 0.030 cm in tissue.
• Fraction transmitted through the dead layer of the skin: 0.12

Dose and Shielding:

• Dose rate to the skin at 10 cm: 625 mrad/hour/mCi
  (for an unshielded point source)
• Dose rate to basal cells from
  skin contamination of 1 mCi/cm2: 1460 mrad/hr
• Shielding: None needed, when used in millicurie quantities under normal laboratory conditions
• Annual Limit on Intake (ALI): 10 millicuries via ingestion for most compounds of sulfur. The intake of one ALI will produce a dose of 5 rem.

Detection:

Liquid scintillation counting is the preferred method for detecting S-35. Most G-M detectors are not likely to detect the presence of S-35 in amounts less than about 100,000 dpm (0.05 µCi).

Precautions:

• 35S-labeled methionine/cysteine compounds can volatilize. Stock solutions and thawed materials should be opened within a fume hood. Activated charcoal can be used to trap contamination within equipment such as incubators. Contact EHS for further information.
• Low-level S-35 contamination cannot be easily detected with a G-M meter, and special precautions are needed to keep the work environment clean. The regular use of wipe testing, using a liquid scintillation counter, is the only way to insure that the work space does not contain low-level removable contamination.

Waste Disposal:

• Solid Wastes: through the Decay-in Storage Program
• Liquid Wastes: through the Sewer Disposal Program. The monthly secondary disposal limit is 3 mCi.

Iron-55

Physical Characteristics

Half-life: 2.70 years
Emissions: Principal emissions are a 6 keV x-ray and 5.2 keV [average] Auger electrons.
Electron Maximum Range: 0.15 cm in air; 0.0 cm in tissue

Dose and Shielding

Dose rate at 10 cm: negligible
Dose rate to basal cells from skin contamination of 1 µCi/cm2: 59 mrem/hr
Shielding: None needed, when used in millicurie quantities, under normal laboratory operations.
Annual Limit on Intake (ALI): 2,000 microcuries via inhalation, and 9,000 microcuries via ingestion. The intake of one ALI will produce a dose of 5 rem.

Detection

Liquid scintillation counting is the preferred method for detecting Fe-55 contamination, although a low energy sodium iodide crystal scintillation detector will also detect Fe-55 with a lower efficiency. The regular use of wipe testing, using a liquid scintillation counter, is the only way to insure that the work space does not contain low-level removable contamination.

Precautions

External radiation from Fe-55 is low energy and does not normally present an external exposure hazard. Low-level Fe-55 contamination is not readily detected with a survey meter, and special precautions are needed to keep the work environment clean. The regular use of wipe testing, using a liquid scintillation counter, is the only way to insure that your work space does not contain low-level removable contamination.

Radiation Monitoring Requirements: Radiation monitoring badges are not required for Fe-55 users.

Waste Disposal

Solid Wastes: through the Off-Site Radioactive Waste Disposal Program.

Liquid Wastes: through the Sewer Disposal Program. The monthly secondary disposal limit is 3 mCi.

Cobalt-57

Physical Characteristics

Half-life: 271.8 days
Emissions: Principal emissions are 122 keV gammas (86%) and 137 keV gammas (11%), accompanied by electrons with energies ranging up to 7 keV
Half-Value Layer: < 1 mm lead
The half-value layer is the amount of material required to reduce the radiation intensity by 50%.

Dose and Shielding

Gamma dose rate (deep tissue dose) at 30 cm: 0.93mrem/hour per millicurie at 30 cm (for an unshielded point source)
Dose rate to epidermal basal cells from skin contamination of 1 µCi/cm2: 444 mrem/hr
Shielding: Lead foil or sheets, when used in hundreds of microcuries or in millicurie quantities.
Annual Limit on Intake (ALI): 4000 microcuries via ingestion and 700 microcuries via inhalation. The ingestion of one ALI will produce a dose of 5 rem.

Detection

A sodium iodide crystal scintillation detector is the preferred method for detecting Co-57. Additionally a G-M detector will detect Co-57 contamination with a significantly lower efficiency of detection. Liquid scintillation counting is also an acceptable method for detecting removable contamination.

Precautions

High localized doses are possible while handling Co-57 and as a result of skin contamination. Reduce doses by using remote handling tools such as tongs, using shielding extensively to shield storage and experimental containers and work areas, and performing thorough and frequent surveys of the work area, clothing and the body.

Radiation Monitoring Requirements: Radiation monitoring badges must be worn by any person who uses open sources of Co-57 in amounts of 0.5 mCi or more for extended operations (applies to most operations other than simple aliquoting from a stock vial).

Waste Disposal

Solid Wastes/Liquid Scintillation Wastes: through the Off-Site Radioactive Waste Disposal Program

Liquid Wastes: through the Sewer Disposal Program. The monthly secondary disposal limit is 3 mCi.

Iron-59

Physical Characteristics

Half-life: 44.6 days
Emissions:

Beta particles: 0.273 MeV (46%) and 0.466 MeV (53%) maximum energies with average energies of 0.081 MeV and 0.149 MeV respectively.
Gamma rays: 1.099 MeV (56%) and 1.292 MeV (44%).
Beta Maximum Range: ~ 100 cm in air; 0.14 cm in tissue; 0.12 cm in plexiglas

Fraction transmitted through the dead layer of the skin: 0.95
Half-Value Layer: 15 mm lead
The half-value layer is the amount of material required to reduce the radiation intensity by 50%.

Dose and Shielding

Gamma dose rate (deep tissue dose) at 30 cm: 7.0 mrem/hour/mCi (for an unshielded point source)
Beta dose rate to the skin at 30 cm: 130 mrem/hour/mCi (for an unshielded point source)
Dose rate to epidermal basal cells from skin contamination of 1 µCi/cm2: 3593 mrem/hour
Shielding: Generally, lead is the preferred shielding material for Fe-59 for lower activity operations. However, it may be desirable to use a combination of plexiglas and lead/steel as shielding when working with multi-millicurie amounts to minimize the amount of bremsstrahlung produced by the betas. In such a case, plexiglas should be placed closest to the source as primary shielding, and lead should be used outside the plexiglas as secondary shielding.
Annual Limit on Intake (ALI): 800 microcuries via ingestion and 300 via inhalation. The intake of one ALI will produce a dose of 5 rem.

Detection

A sodium iodide crystal scintillation detector is the preferred method for detecting Fe-59. Additionally a G-M detector will readily detect Fe-59 contamination, although liquid scintillation counting is also an acceptable method for detecting removable contamination.

Precautions

High localized doses are possible while handling Fe-59 and as a result of skin contamination. Reduce doses by wearing safety glasses (for shielding the eyes), using remote handling tools such as tongs, using shielding extensively to shield storage and experimental containers and work areas, and performing thorough and frequent surveys of the work area, clothing and the body.

Radiation Monitoring Requirements: Radiation monitoring badges must be worn by any person who uses open sources of Fe-59 in amounts of 0.5 mCi or more for extended operations (applies to most operations other than simple aliquoting from a stock vial).

Waste Disposal

Solid Wastes: through the Decay-in-Storage Program
Liquid Wastes: through the Sewer Disposal Program. The monthly secondary disposal limit is 300 µCi.

Nickel-63

Physical Characteristics

Half-life: 100.1 years
Emissions: Beta particles with a maximum energy of 66 keV and an average energy of 17 keV
Maximum Range: 5 cm in air; < 0.01 cm in tissue

Dose and Shielding

Dose rate to the skin at 10 cm: negligible (for an unshielded point source)

Dose rate to epidermal basal cells from skin contamination of 1 µCi/cm2: negligible

Shielding: None needed.

Annual Limit on Intake (ALI): 9000 microcuries via ingestion and 2000 microcuries via inhalation. The ingestion of one ALI will produce a dose of 5 rem.

Detection

Liquid scintillation counting is the preferred method for detecting Ni-63. G-M detectors will not detect Ni-63 contamination.

Precautions

Ni-63 contamination cannot be detected with a G-M meter, and special precautions are needed to keep the work environment clean. The regular use of wipe testing, using a liquid scintillation counter, is the only way to insure that your work space does not contain low-level removable contamination.

Radiation Monitoring Requirements: Radiation monitoring badges are not required for Ni-63 users, since the monitoring badges will not detect Ni-63.

Waste Disposal

Solid Wastes/Liquid Scintillation Wastes: through the Off-Site Radioactive Waste Disposal Program
Liquid Wastes: through the Sewer Disposal Program. The monthly secondary disposal limit is 3 mCi.

Zinc-65

Physical Characteristics

Half-life: 243.9 days

Emissions: Beta (positron) particles with a maximum energy of 0.33 MeV (2%) and an average energy of 0.099 MeV. Gamma rays: 1.116 MeV (51%) and 0.511 MeV (2%).
Beta Maximum Range: 76.2 cm in air; 0.10 cm in tissue; 0.08 cm in plexiglas
Fraction transmitted through the dead layer of the skin: 0.95
Half-Value Layer: 14 mm lead; 2 cm in tissue
The half-value layer is the amount of material required to reduce the radiation intensity by 50%.

Dose and Shielding

Beta Dose rate to the skin at 30 cm: 1.93 mrem/hour/mCi (for an unshielded point source)
Gamma Dose rate (deep tissue dose) at 30 cm: 3.44 mrem/hour/mCi (for an unshielded point source)
Dose rate to epidermal basal cells from skin contamination of 1 µCi/cm2: 281 mrem/hour
Shielding: Shield stock vials with lead. Generally, lead is the preferred shielding material for Zn-65 for lower activity operations. However, since significant bremsstrahlung may be produced with higher activities, it may be desirable to use a combination of plexiglas and lead/steel as shielding when working with multi-millicurie amounts. In such a case, plexiglas should be placed closest to the source as primary shielding, and lead should be used outside the plexiglas as secondary shielding.
Annual Limit on Intake (ALI): 400 microcuries via ingestion and 300 microcuries via inhalation. The intake of one ALI will produce a dose of 5 rem.

Detection

A G-M detector will readily detect low-level Zn-65 contamination, although liquid scintillation counting is also an acceptable method for detecting removable contamination.

Precautions

High localized doses are possible while handling millicurie amounts of Zn-65 and as a result of skin contamination. Reduce doses by wearing safety glasses (for shielding the eyes), using remote handling tools such as tongs, using shielding extensively to shield storage and experimental containers and work areas, and performing thorough and frequent surveys of the work area, clothing and the body.

Radiation Monitoring Requirements: Radiation monitoring badges must be worn by any person who uses open sources of Zn-65 in amounts of 0.5 mCi or more for extended operations (applies to most operations other than simple aliquoting from a stock vial).

Waste Disposal

Solid Wastes: through the Off-Site Radioactive Waste Disposal Program
Liquid Wastes: through the Sewer Disposal Program. The monthly secondary disposal limit is 300 µCi.

Selenium-75

Physical Characteristics

Half-life: 119.8 days
Emissions: Principal emissions are 136 keV and 265 keV x-rays.
Half-Value Layer: 0.02 mm lead; 2 cm in tissue
The half-value layer is the amount of material required to reduce the radiation intensity by 50%.

Dose and Shielding

Gamma Dose rate (deep tissue dose) at 30 cm: 2.74 mrem/hour/mCi (for an unshielded point source)
Dose rate to epidermal basal cells from skin contamination of 1 µCi/cm2: 519 mrem/hour
Shielding: Lead foil or sheets, when used in hundreds of microcuries or in millicurie quantities. None needed when used in low microcurie amounts.
Annual Limit on Intake (ALI): 700 microcuries via inhalation, and 500 microcuries via ingestion. The intake of one ALI will produce a dose of 5 rem.

Detection

A sodium iodide crystal scintillation detector is the preferred method for detecting Se 75. Additionally a G-M detector will readily detect Se-75 contamination, although liquid scintillation counting is also an acceptable method for detecting removable contamination.

Precautions

High localized doses are possible while handling millicurie amounts of Se-75 and as a result of skin contamination. Reduce doses by using remote handling tools such as tongs, using shielding extensively to shield storage and experimental containers and work areas, and performing thorough and frequent surveys of the work area, clothing and the body.

Radiation Monitoring Requirements: Radiation monitoring badges must be worn by any person who uses open sources of Se-75 in amounts of 0.5 mCi or more for extended operations (applies to most operations other than simple aliquoting from a stock vial).

Waste Disposal

Solid Wastes: through the Decay-in-Storage Program.

Liquid Wastes: through the Sewer Disposal Program. The monthly secondary disposal limit is 3 mCi.

Cadmium-109

Physical Characteristics

Half-life: 462.6 days
Emissions: Principal emissions are 22.1 keV x-rays (83%), accompanied by electrons with energies ranging up to 87 keV.
Half-Value Layer: 0.01 mm lead; 2 cm in tissue
The half-value layer is the amount of material required to reduce the radiation intensity by 50%.

Dose and Shielding

Beta dose rate to the skin at 30 cm: 0 mrem/hour/mCi (for an unshielded point source)
Gamma Dose rate (deep tissue dose) at 30 cm: 0.778 mrem/hour/mCi (for an unshielded point source)
Dose rate to epidermal basal cells from skin contamination of 1 µCi/cm2: 2000 mrem/hour
Shielding: Lead foil or sheets are used to shield the x-rays (the electrons are too low in energy to require shielding) when Cd-109 is used in hundreds of microcuries or in millicurie quantities. Shielding is not needed when Cd-109 is used in low microcurie amounts.
Annual Limit on Intake (ALI): 40 microcuries via inhalation, and 300 microcuries via ingestion. The intake of one ALI will produce a dose of 5 rem. The critical organ for protection are the kidneys.

Detection

A sodium iodide crystal scintillation detector is the preferred method for detecting Cd-109. G-M detectors are not likely to detect the presence of Cd-109 in amounts less than about 100,000 dpm (0.05 µCi).

Precautions

Skin contamination and ingestion are the chief concerns when working with Cd-109, and appropriate precautions must be taken to limit contamination. Contamination of work areas and individuals is a more significant hazard than the external dose, unless working with millicurie quantities.

Radiation Monitoring Requirements: Radiation monitoring badges must be worn by any person who uses open sources of Cd-109 in amounts of 1 mCi or more for extended operations (applies to most operations other than simple aliquoting from a stock vial).

Waste Disposal

Solid Wastes: through the Off-Site Radioactive Waste Disposal Program.

Liquid Wastes: through the Sewer Disposal Program. The monthly secondary disposal limit is 300 µCi.

Iodine-125

Physical Characteristics:

• Half-life: 60.1 days
• Emissions: Principal emissions are a 35 keV gamma ray and 27 - 32 keV x-rays.
• Half-Value Layer: 0.02 mm lead; 2 cm in tissue. (The half-value layer is the amount of material required to reduce the radiation intensity by 50%.)

Dose and Shielding:

• Dose rate at 10 cm: 15 mrem/hour/mCi
  (for an unshielded point source)
• Shielding: Lead foil or sheets, when used in hundreds of microcuries or in millicurie quantities. None needed when used in low microcurie amounts such as for RIA kits.
• Annual Limit on Intake (ALI): 60 microcuries via inhalation, and 40 microcuries via ingestion. The intake of one ALI will produce a dose of 5 rem. The critical organ for protection is the thyroid gland.
  

Detection:

A sodium iodide crystal scintillation detector is the preferred method for detecting I-125. G-M detectors are not likely to detect the presence of I-125 in amounts less than about 100,000 dpm (0.05 µCi).

Precautions:

Volatile iodine can be released from Na125I or from iodinated compounds containing hundreds of microcuries or more of I-125. Containers of I-125, including sample vials of iodinated compounds, should always be opened in a fume hood. Personnel using I-125 in hundreds of microcuries or more must wear double gloves and should change gloves as soon as the gloves become contaminated. Iodinations must be performed under EHS surveillance and thyroid count bioassays must be performed following an iodination.

Waste Disposal:

• Solid Wastes: through the Decay-in-Storage Program.
• Liquid Wastes: through the Sewer Disposal Program. The monthly secondary disposal limit is 30 µCi.

Mercury-203

Physical Characteristics

Half-life: 47 days
Emissions: Beta particles: 0.210 MeV maximum energy (100 %) and 0.070 MeV average energy.

Gamma rays: 0.279 MeV (100%).
Beta Maximum Range: 34 cm in air; 0.04 cm in tissue; 0.04 cm in plexiglas

Dose and Shielding

Dose rate to the skin at 30 cm: 15.2 mrem/hour/mCi (for an unshielded point source)
Gamma Dose rate (deep tissue dose) at 30 cm: 1.63 mrem/hour/mCi (for an unshielded point source)
Dose rate to epidermal basal cells from skin contamination of 1 µCi/cm2: 3296 mrem/hour
Shielding: Shield stock vials with lead.
Half-Value Layer: 0.2 cm lead
The half-value layer is the amount of material required to reduce the radiation intensity by 50%.
Annual Limit on Intake (ALI): 500 microcuries via ingestion and 800 microcuries via inhalation. The intake of one ALI will produce a dose of 5 rem.

Detection

A G-M detector will readily detect low-level Hg-203 contamination, although liquid scintillation counting is also an acceptable method for detecting removable contamination.

Precautions

High localized doses are possible while handling millicurie amounts of Hg-203 and as a result of skin contamination. Reduce doses by wearing safety glasses (for shielding the eyes), using remote handling tools such as tongs, using shielding extensively to shield storage and experimental containers and work areas, and performing thorough and frequent surveys of the work area, clothing and the body.

Radiation Monitoring Requirements: Radiation monitoring badges must be worn by any person who uses open sources of Hg-203 in amounts of 0.5 mCi or more for extended operations (applies to most operations other than simple aliquoting from a stock vial).

Waste Disposal

Solid Wastes: through the Decay-in-Storage Program
Liquid Wastes: through the Sewer Disposal Program. The monthly secondary disposal limit is 3 mCi.