49 CFR 174.715 - Cleanliness of transport vehicles after use.
(a) Each transport vehicle used for transporting Class 7 (radioactive) materials under exclusive use conditions (as defined in § 173.403 of this subchapter) in accordance with § 173.427(b)(4), § 173.427(c), or § 173.443(b), must be surveyed with appropriate radiation detection instruments after each use. A transport vehicle may not be returned to Class 7 (radioactive) materials exclusive use transport service, and then only for a subsequent exclusive use shipment utilizing the provisions of any of the paragraphs § 173.427(b)(4), § 173.427(c), or § 173.443(b), until the radiation dose rate at any accessible surface is 0.005 mSv per hour (0.5 mrem per hour) or less, and there is no significant non-fixed contamination, as specified in § 173.443(a) of this subchapter.
(b) This section does not apply to any transport vehicle used solely for transporting Class 7 (radioactive) materials if a survey of the interior surface shows that the radiation dose rate does not exceed 0.1 mSv per hour (10 mrem per hour) at the interior surface or 0.02 mSv per hour (2 mrem per hour) at 1 m (3.3 feet) from any interior surface. The transport vehicle must be stenciled with the words “FOR RADIOACTIVE MATERIALS USE ONLY” in lettering at least 7.6 cm (3 inches) high in a conspicuous place on both sides of the exterior of the transport vehicle, and it must be kept closed at all times other than during loading and unloading.