49 C.F.R. § 174.700
Special handling requirements for Class 7 (radioactive) materials
(a) Each rail shipment of low specific activity materials or surface contaminated objects as defined in § 173.403 of this subchapter must be loaded so as to avoid spillage and scattering of loose material. Loading restrictions are prescribed in § 173.427 of this subchapter.
(b) The number of packages of Class 7 (radioactive) materials that may be transported by rail car or stored at any single location is limited to a total transport index and a total criticality safety index (as defined in § 173.403 of this subchapter) of not more than 50 each. This provision does not apply to exclusive use shipments as described in §§ 173.403, 173.427, 173.441, and 173.457 of this subchapter.
(c) Each package of Class 7 (radioactive) material bearing RADIOACTIVE YELLOW-II or RADIOACTIVE YELLOW-III labels may not be placed closer than 0.9 m (3 feet) to an area (or dividing partition between areas) which may be continuously occupied by any passenger, rail employee, or shipment of one or more animals, nor closer than 4.5 m (15 feet) to any package containing undeveloped film (if so marked). If more than one package of Class 7 (radioactive) materials is present, the distance must be computed from the table below on the basis of the total transport index number (determined by adding together the transport index numbers on the labels of the individual packages) of packages in the rail car or storage area:
| Total transport index | Minimum separation distance to nearest undeveloped film | Minimum distance to area of persons or minimum distance from dividing partition of a combination car | ||
|---|---|---|---|---|
| Meters | Feet | Meters | Feet | |
| None | 0 | 0 | 0 | 0 |
| 0.1 to 10.0 | 4.5 | 15 | 0.9 | 3 |
| 10.1 to 20.0 | 6.7 | 22 | 1.2 | 4 |
| 20.1 to 30.0 | 7.7 | 29 | 1.5 | 5 |
| 30.1 to 40.0 | 10 | 33 | 1.8 | 6 |
| 40.1 to 50.0 | 10.9 | 36 | 2.1 | 7 |
| Note: The distance in this table must be measured from the nearest point on the nearest packages of Class 7 (radioactive) materials. | ||||
(d) Each shipment of fissile material packages must conform to requirements of §§ 173.457 and 173.459.
(e) [Reserved]
(f) A person shall not remain unnecessarily in, on or near a transport vehicle containing Class 7 (radioactive) materials.
(g) In the case of packages shipped under the exclusive use provisions of § 173.441(b) of this subchapter for packages with external radiation levels in excess of 2 mSv per hour (200 mrem per hour) at the package surface—
(1) The transport vehicle must meet the requirements for a closed transport vehicle (§ 173.403 of this subchapter);
(2) Each package must be secured so that its position within the transport vehicle remains fixed under conditions normally incident to transportation; and
(3) The radiation level may not exceed 0.02 mSv per hour (2 mrem per hour) in any normally occupied position in the transport vehicle or adjacent rail car.