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 |
[71 FR 65708, Nov. 8, 2006]