# Activity-mass relationships for uranium and natural thorium.

- **operation:** document
- **citation:** 49 CFR 173.434
- **title:** Activity-mass relationships for uranium and natural thorium.
- **source type:** regulation
- **agency:** Pipeline and Hazardous Materials Safety Administration
- **status:** current
- **official:** true
- **published on:** Not available
- **effective on:** 2026-08-18
- **summary:** The table of activity-mass relationships for uranium and natural thorium are as follows:

Thorium and uranium enrichment 1 (Wt% 235 U present) Specific activity TBq/gram Grams/Tbq Ci/gram Grams/Ci 0.45 (depleted) 1.9 × 10−8 5.4 × 107 5.0 × 10−7 2.0 × 106 0.72 (natural) 2.6 × 10−8 3.8 × 107 7.1 × 10−
- **machine formats:** - **json:** https://regulus.evalyn.ai/document/49-cfr-173-434.json
- **markdown:** https://regulus.evalyn.ai/document/49-cfr-173-434.md
- **app url:** https://regulus.evalyn.ai/document/49-cfr-173-434
- **source url:** https://www.ecfr.gov/on/2026-08-18/title-49/section-173.434
**body:**

The table of activity-mass relationships for uranium and natural thorium are as follows:

Thorium and uranium enrichment 1 (Wt% 235 U present) Specific activity TBq/gram Grams/Tbq Ci/gram Grams/Ci 0.45 (depleted) 1.9 × 10−8 5.4 × 107 5.0 × 10−7 2.0 × 106 0.72 (natural) 2.6 × 10−8 3.8 × 107 7.1 × 10−7 1.4 × 106 1.0 2.8 × 10−8 3.6 × 107 7.6 × 10−7 1.3 × 106 1.5 3.7 × 10−8 2.7 × 107 1.0 × 10−6 1.0 × 106 5.0 1.0 × 10−7 1.0 × 107 2.7 × 10−6 3.7 × 105 10.0 1.8 × 10−7 5.6 × 106 4.8 × 10−6 2.1 × 105 20.0 3.7 × 10−7 2.7 × 106 1.0 × 10−5 1.0 × 105 35.0 7.4 × 10−7 1.4 × 106 2.0 × 10−5 5.0 × 104 50.0 9.3 × 10−7 1.1 × 106 2.5 × 10−5 4.0 × 104 90.0 2.1 × 10−6 4.7 × 105 5.8 × 10−5 1.7 × 104 93.0 2.6 × 10−6 3.9 × 105 7.0 × 10−5 1.4 × 104 95.0 3.4 × 10−6 3.0 × 105 9.1 × 10−5 1.1 × 104 Natural thorium 8.1 × 10−9 1.2 × 108 2.2 × 10−7 4.6 × 106 1 The figures for uranium include representative values for the activity of uranium-234 which is concentrated during the enrichment process. The activity for thorium includes the equilibrium concentration of thorium-228.

[Amdt. 173-244, 60 FR 50307, Sept. 28, 1995, as amended by 63 FR 52849, Oct. 1, 1998]
- **truncated:** false
- **body characters:** 1144