Report a Safety Concern
Search

The U.S. Nuclear Regulatory Commission is in the process of rescinding or revising guidance and policies posted on this webpage in accordance with Executive Order 14151 Ending Radical and Wasteful Government DEI Programs and Preferencing, and Executive Order 14168 Defending Women From Gender Ideology Extremism and Restoring Biological Truth to the Federal Government. In the interim, any previously issued diversity, equity, inclusion, or gender-related guidance on this webpage should be considered rescinded that is inconsistent with these Executive Orders.

Home NRC Library Document Collections Regulations (NRC, 10 CFR) Part Index

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 65686, November 8, 2006]

Page Last Reviewed/Updated Wednesday, March 24, 2021