12 Va. Admin. Code § 5-481-3060
Article 4
Operating Controls and Procedures
When the isotopic abundance, mass, concentration, degree of irradiation, degree of moderation, or other pertinent property of fissile material in any package is not known, the licensee shall package the fissile material as if the unknown properties have credible values that will cause the maximum neutron multiplication.
§ 32.1-229 of the Code of Virginia.
Derived from Virginia Register Volume 22, Issue 25, eff. September 20, 2006.