10 CFR Appendix E to Part 20: Appendix E to Part 20— Nationally Tracked Source Thresholds

The Terabecquerel (TBq) values are the regulatory standard. The curie (Ci) values specified are obtained by converting from the TBq value. The curie values are provided for practical usefulness only and are rounded after conversion.

Radioactive material Category 1 (TBq) Category 1 (Ci) Category 2 (TBq) Category 2 (Ci)

Actinium-227 20 540 0.2 5.4

Americium-241 60 1,600 0.6 16

Americium-241/Be 60 1,600 0.6 16

Californium-252 20 540 0.2 5.4

Cobalt-60 30 810 0.3 8.1

Curium-244 50 1,400 0.5 14

Cesium-137 100 2,700 1 27

Gadolinium-153 1,000 27,000 10 270

Iridium-192 80 2,200 0.8 22

Plutonium-238 60 1,600 0.6 16

Plutonium-239/Be 60 1,600 0.6 16

Polonium-210 60 1,600 0.6 16

Promethium-147 40,000 1,100,000 400 11,000

Radium-226 40 1,100 0.4 11

Selenium-75 200 5,400 2 54

Strontium-90 1,000 27,000 10 270

Thorium-228 20 540 0.2 5.4

Thorium-229 20 540 0.2 5.4

Thulium-170 20,000 540,000 200 5,400

Ytterbium-169 300 8,100 3 81