Half Lives

Radiation-related consulting and services from Integrated Environmental Management, Inc.

The half-life of a radioactive element is the time that it takes for one half of the atoms of that substance to disintegrate into another nuclear form. These can range from mere fractions of a second, to many billions of years. In addition, the half-life of a particular radionuclide is unique to that radionuclide, meaning that knowledge of the half-life leads to the identity of the radionuclide. The following is a listing of the half-lives of commonly-encountered radionuclides, with the units of each as shown.

Please note that some of the longer half-lives are written in scientific notation (i.e., 7.2E1 is equal to 7.2 x 10, or 72.)

Actinium

• Ac-225 - 10.0 days
• Ac-227 - 21.773 years
• Ac-228 - 6.13 hours

Americium

• Am-241 - 432.2 years
• Am-242 - 16.02 hours
• Am-242m - 152 years
• Am-243 - 7380 years

Antimony

• Sb-124 - 60.20 days
• Sb-125 - 2.77 years
• Sb-126 - 12.4 days
• Sb-126m - 19.0 minutes
• Sb-127 - 3.85 days

Argon

• Ar-41 - 1.827 hours

Astatine

• At-217 - 0.0323 seconds
• At-218 - 2 seconds

Barium

• Ba-137m - 2.552 minutes
• Ba-139 - 82.7 minutes
• Ba-140 - 12.74 days
• Ba-141 - 18.27 minutes
• Ba-142 - 10.6 minutes

Beryllium

• Be-10 - 1.6E6 years
• Be-7 - 53.44 days

Bismuth

• Bi-210 - 5.012 days
• Bi-211 - 2.14 minutes
• Bi-212 - 60.55 minutes
• Bi-213 - 45.65 minutes
• Bi-214 - 19.9 minutes

Bromine

• Br-82 - 35.30 hours
• Br-83 - 2.39 hours
• Br-84 - 31.80 minutes

Cadmium

• Cd-113m - 13.6 years
• Cd-115m - 44.6 days

Calcium

• Ca-41 - 1.3E5 years
• Ca-47 - 4.53 days

Californium

• Cf-252 - 2.638 years

Carbon

• C-11 - 20.38 minutes
• C-14 - 5730 years

Cerium

• Ce-141 - 32.50 days
• Ce-143 - 33.0 hours
• Ce-144 - 284.3 days

Cesium

• Cs-134 - 2.062 years
• Cs-134m - 2.90 hours
• Cs-135 - 2.3E6 years
• Cs-136 - 13.1 days
• Cs-137 - 30.0 years
• Cs-138 - 32.2 minutes

Chromium

• Cr-51 - 27.704 days

Cobalt

• Co-56 - 78.76 days
• Co-57 - 270.9 days
• Co-58 - 70.8 days
• Co-60 - 5.27 years

Copper

• Cu-61 - 3.408 hours
• Cu-64 - 12.701 hours

Curium

• Cm-242 - 162.8 days
• Cm-243 - 28.5 years
• Cm-244 - 18.11 years
• Cm-245 - 8500 years
• Cm-246 - 4730 years
• Cm-247 - 1.56E7 years
• Cm-248 - 3.39E5 years

Europium

• Eu-152 - 13.33 years
• Eu-154 - 8.8 years
• Eu-155 - 4.96 years
• Eu-156 - 15.19 days

Fluorine

• F-18 - 109.74 minutes

Francium

• Fr-221 - 4.8 minutes
• Fr-223 - 21.8 minutes

Gadolinium

• Gd-152 - 1.08E14 years

Gallium

• Ga-67 - 3.261 days

Gold

• Au-198 - 2.696 days

Holmium

• Ho-166m - 1.20E3 years

Hydrogen

• H-3 - 12.35 years

Indium

• In-111 - 2.83 days
• In-113 - 1.658 hours
• In-115 - 5.1E15 years

Iodine

• I-123 - 13.2 hours
• I-125 - 60.14 days
• I-129 - 1.57E7 years
• I-130 - 12.36 hours
• I-131 - 8.04 days
• I-132 - 2.30 hours
• I-133 - 20.8 hours
• I-134 - 52.6 minutes
• I-135 - 6.61 hours

Iridium

• Ir-192 - 74.02 days

Iron

• Fe-55 - 2.7 years
• Fe-59 - 44.53 days

Krypton

• Kr-83m - 1.83 hours
• Kr-85 - 10.72 years
• Kr-85m - 4.48 hours
• Kr-87 - 76.3 minutes
• Kr-88 - 2.84 minutes

Lanthanum

• La-140 - 40.272 hours
• La-141 - 3.93 hours
• La-142 - 92.5 minutes

Lead

• Pb-209 - 3.253 hours
• Pb-210 - 22.3 years
• Pb-211 - 36.1 minutes
• Pb-212 - 10.64 hours
• Pb-214 - 26.8 minutes
• Pb-214 - 26.8 minutes

Manganese

• Mn-52 - 5.591 days
• Mn-52m - 21.1 minutes
• Mn-54 - 312.5 days
• Mn-56 - 2.579 hours
• Mn-57 - 36.08 hours

Mercury

• Hg-197 - 64.1 hours
• Hg-203 - 46.60 days

Molybdenum

• Mo-93 - 3.5E3 years
• Mo-99 - 66.0 hours

Neodymium

• Nd-147 - 10.98 days

Neptunium

• Np-237 - 2.14E6 years
• Np-238 - 2.117 days
• Np-239 - 2.355 days
• Np-240 - 65 minutes
• Np-240m - 7.4 minutes

Nickel

• Ni-59 - 7.5E4 years
• Ni-63 - 96 years
• Ni-65 - 2.520 hours

Niobium

• Nb-93m - 13.6 years
• Nb-95 - 35.15 days
• Nb-95m - 86.6 hours
• Nb-97 - 72.1 minutes
• Nb-97m - 60 seconds

Nitrogen

• N-13 - 9.97 minutes
• N-16 - 7.13 seconds

Oxygen

• O-15 - 122.24 seconds

Palladium

• Pd-107 - 6.5E6 years
• Pd-109 0- 13.427 hours

Phosphorus

• P-32 - 14.29 days

Plutonium

• Pu-238 - 87.74 years
• Pu-239 - 24065 years
• Pu-240 - 6537 years
• Pu-241 - 14.4 years
• Pu-242 - 3.76E5 years
• Pu-243 - 4.956 hours
• Pu-244 - 8.26E7 years

Polonium

• Po-210 - 138.38 days
• Po-211 - 0.516 seconds
• Po-212 - 0.305 microseconds
• Po-213 - 4.2 microseconds
• Po-214 - 164.3 microseconds
• Po-215 - 0.00178 seconds
• Po-216 - 0.15 seconds
• Po-218 - 3.05 minutes

Potassium

• K-40 - 1.27E9 years
• K-42 - 12.36 hours
• K-43 - 22.6 hours

Praseodymium

• Pr-143 - 13.56 days
• Pr-144 - 17.28 minutes
• Pr-144m - 7.2 minutes

Promethium

• Pm-147 - 2.6234 years
• Pm-148 - 5.37 days
• Pm-148 - 41.3 days
• Pm-149 - 53.08 hours
• Pm-151 - 28.40 hours

Protactinium

• Pa-231 - 3.28E4 years
• Pa-233 - 27.0 days
• Pa-234 - 6.70 hours
• Pa-234m - 1.17 minutes

Radium

• Ra-223 - 11.434 days
• Ra-224 - 3.66 days
• Ra-225 - 14.8 days
• Ra-226 - 1600 years
• Ra-228 - 5.75 years

Radon

• Rn-219 - 3.96 seconds
• Rn-220 - 55.6 seconds
• Rn-222 - 3.824 days

Rhenium

• Re-187 - 5E10 years

Rhodium

• Rh-103m - 56.12 minutes
• Rh-105 - 35.36 hours
• Rh-106 - 29.9 seconds

Rubidium

• Rb-86 - 18.66 days
• Rb-87 - 4.7E10 years
• Rb-88 - 17.8 minutes
• Rb-89 - 15.2 minutes

Ruthenium

• Ru-103 - 39.28 days
• Ru-105 - 4.44 hours
• Ru-106 - 368.2 days
• Ru-97 - 2.9 days

Samarium

• Sm-147 - 1.06E11 years
• Sm-151 - 90 years
• Sm-153 - 46.7 hours

Scandium

• Sc-44 - 3.927 hours
• Sc-46 - 83.83 days
• Sc-47 - 3.351 days
• Sc-48 - 43.7 hours

Selenium

• Se-75 - 119.78 days
• Se-79 - 65000 years

Silver

• Ag-110 - 24.6 seconds
• Ag-110m - 249.9 days
• Ag-111 - 7.45 days

Sodium

• Na-22 - 2.602 years
• Na-24 - 15.00 hours

Strontium

• Sr-85 - 64.84 days
• Sr-87m - 2.81 hours
• Sr-89 - 50.5 days
• Sr-90 - 29.12 years
• Sr-91 - 9.5 hours
• Sr-92 - 2.71 hours

Sulfur

• S-35 - 87.44 days

Technetium

• Tc-101 - 14.2 minutes
• Tc-99 - 2.13E5 years
• Tc-99m - 6.02 hours

Tellurium

• Te-125m - 58 days
• Te-127 - 9.35 hours
• Te-127m - 109 days
• Te-129 - 69.6 minutes
• Te-129m - 33.6 days
• Te-131 - 25.0 minutes
• Te-131m - 30 hours
• Te-132 - 78.2 hours
• Te-133 - 12.45 minutes
• Te-133m - 55.4 minutes
• Te-134 - 41.8 minutes

Terbium

• Tb-160 - 72.3 days

Thallium

• Tl-201 - 73.06 hours
• Tl-207 - 4.77 minutes
• Tl-208 - 3.07 minutes
• Tl-209 - 2.20 minutes

Thorium

• Th-227 - 18.718 days
• Th-228 - 1.913 years
• Th-229 - 7340 years
• Th-230 - 7.7E4 years
• Th-231 - 25.52 hours
• Th-232 - 1.41E10 years
• Th-234 - 24.10 days

Tin

• Sn-119m - 293.1 days
• Sn-123 - 129.2 days
• Sn-125 - 9.64 days
• Sn-126 - 1.0E5 years

Tungsten

• W-181 - 121.2 days
• W-185 - 75.1 days
• W-187 - 23.9 hours

Uranium

• U-232 - 72 years
• U-233 - 1.59E5 years
• U-234 - 2.445E5 years
• U-235 - 7.03E8 years
• U-236 - 2.34E7 years
• U-237 - 6.75 days
• U-238 - 4.47E9 years
• U-240 - 14.1 hours

Vanadium

• V-48 - 16.238 days

Xenon

• Xe-131m - 11.9 days
• Xe-133 - 5.245 days
• Xe-133m - 2.188 days
• Xe-135 - 9.09 hours
• Xe-135m - 15.29 minutes
• Xe-138 - 14.17 minutes

Ytterbium

• Yb-169 - 32.01 days

Yttrium

• Y-90 - 64.0 hours
• Y-91 - 58.51 days
• Y-91m - 49.71 minutes
• Y-92 - 3.54 hours
• Y-93 - 10.1 hours

Zinc

• Zn-65 - 243.9 days
• Zn-69 - 57 minutes

Zirconium

• Zr-93 - 1.53E6 years
• Zr-95 - 63.98 days
• Zr-97 - 16.90 hours

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