10 CFR Part 20, Appendix E
Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
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 |
[71 FR 65708, Nov. 8, 2006]