Agent Name

Potassium-40

CAS Number

13966-00-2

Formula

K

Major Category

Physical/Radiation

Category

Radionuclides

Description

A naturally occurring isotope that comprises about 0.012% of total potassium; K-39 (93% of potassium) and K-39 (7% of potassium) are not radioactive. Elemental potassium is a soft, silver-white metal. [Argonne]

Sources/Uses

Common element in the soil, the ocean, and in plants and animals; Present in the minerals carnallite, feldspar, saltpeter, greensand, and sylvite; [Argonne]

Comments

Source: Naturally occurring; Half-Life: 1.3 billion years; Specific Activity: 0.0000071 Ci/g Decay Mode: Beta, Electron Capture; GI Absorption: "Almost completely absorbed" Lung Clearance Half-Time: Days Internal Toxicity: High Annual Limit on Intake: 0.3 mCi Tenth-Value Layer: 38.7 mm Pb Gamma Ray Constant: 0.7 R/h @ 1 cm per mCi Radiation Energy (MeV): Beta 1.31 (89%); Gamma 1.46 (11%); [See Glossary for references.] See "Radiation, ionizing."

Exposure Assessment
Half Life

30 days; [Argonne]

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