10 CFR Appendix P to Part 110, Category 1 and 2 Radioactive Material
Table 1  Import and Export Threshold Limits
Radioactive material  Category 1  Category 2  

Terabequerels
(TBq) 
Curies
(Ci) ^{1} 
Terabequerels
(TBq) 
Curies
(Ci) ^{1} 

Americium241  60  1,600  0.6  16 
Americium241/Be  60  1,600  0.6  16 
Californium252  20  540  0.2  5.4 
Curium244  50  1,400  0.5  14 
Cobalt60  30  810  0.3  8.1 
Cesium137  100  2,700  1.0  27 
Gadolinium153  1,000  27,000  10.0  270 
Iridium192  80  2,200  0.8  22 
Plutonium238 ^{2}  60  1,600  0.6  16 
Plutonium239/Be ^{2}  60  1,600  0.6  16 
Promethium147  40,000  1,100,000  400  11,000 
Radium226 ^{a}  40  1,100  0.4  11 
Selenium75  200  5,400  2.0  54 
Strontium90 (Y90)  1,000  27,000  10.0  270 
Thulium170  20,000  540,000  200  5,400 
Ytterbium169  300  8,100  3.0  81 
1 The values to be used to determine whether a license is required are given in TBq. Curie (Ci) values are provided for practical usefulness only and are rounded after conversion.
2 The limits for Pu238 and Pu239/Be in this table apply for imports to the U.S. The limits for exports of Pu238 and Pu239/Be can be found in § 110.21.
a Discrete sources of radium226.
The “sum of fractions” methodology for evaluating combinations of radionuclides being transported, is to be used when import or export shipments contain multiple sources or multiple radionuclides. The threshold limit values used in a sum of the fractions calculation must be the metric values (i.e., TBq).
I. If multiple sources and/or multiple radionuclides are present in an import or export shipment, the sum of the fractions of the activity of each radionuclides must be determined to verify the shipment is less than the Category 1 or 2 limits of Table 1, as appropriate. If the calculated sum of the fractions ratio, using the following equation, is greater than or equal to 1.0, then the import or export shipment exceeds the threshold limits of Table 1 and the applicable security provisions of this part apply.
II. Use the equation below to calculate the sum of the fractions ratio by inserting the actual activity of the applicable radionuclides or of the individual sources (of the same radionuclides) in the numerator of the equation and the corresponding threshold activity limit from the Table 1 in the denominator of the equation. Ensure the numerator and denominator values are in the same units and all calculations must be performed using the TBq (i.e., metric) values of Table 1.