46 C.F.R. § 148.300 – Radioactive materials.

(a) Radioactive materials that may be stowed or transported in bulk are limited to those radioactive materials defined in 49 CFR 173.403 as Low Specific Activity Material, LSA-1, or Surface Contaminated Object, SCO-1.
(b) Skin contact, inhalation or ingestion of dusts generated by Class 7 material listed in Table 148.10 of this part must be minimized.
(c) Each hold used for the transportation of Class 7 material (radioactive) listed in Table 148.10 of this part must be surveyed after the completion of off-loading by a qualified person using appropriate radiation detection instruments. Such holds must not be used for the transportation of any other material until the non-fixed contamination on any surface, when averaged over an area of 300 cm ², does not exceed the following levels:
1. (1) 4.0 Bq/cm ² (10−4 uCi/cm ²;) for beta and gamma emitters and low toxicity alpha emitters, natural uranium, natural thorium, uranium-235, uranium-238, thorium-232, thorium-228 and thorium-230 when contained in ores or physical or chemical concentrates, and radionuclides with a half-life of less than 10 days; and
2. (2) 0.4 Bq/cm ² (10−5 uCi/cm ²) for all other alpha emitters.