Catawba Corps — Hazardous Materials Safety Interpretation

Page 1U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration June 25, 2026 John B. Woodbury Packaging Management Council Coordinator Catawba Corps 3533 15th Street E Lewiston, ID 83501 Reference No. 25-0163 Dear Mr. Woodbury: This letter is in response to your December 15, 2025 email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to fissile materials. Specifically, you ask whether a liquid payload can qualify for the fissile exceptions in § 173.453(b). Yes. In order to qualify for the fissile material exceptions in § 173.453(b), the packaging must contain “15 grams or less of fissile material provided the package has at least 200 grams of solid nonfissile material for every gram of fissile material.” While the nonfissile material in this calculation must be solid, § 173.453(b) does not require that the fissile material be solid. I hope this information is helpful. Please contact us if we can be of further assistance. Sincerely, 1200 New Jersey Avenue, SE Washington, DC 20590 Alexander Wolcott Acting Chief, Regulatory Review and Reinvention Branch Standards and Rulemaking Division#

Page 2Jacobson, N. 25-0163 From: INFOCNTR (PHMSA) To: Baker, Yul (PHMSA) Cc: Hazmat Interps Subject: FW: LOI 24-0124 Clarification Date: Tuesday, December 16, 2025 11:49:32 Good morning, Mr. Woodbury requested and received letter of interpretation #24-0124 early this year. He had a follow question to clarify the guidance in that letter. I reached out Mr. Noah Jacobson, received guidance, and relayed it to Mr. Woodbury. Mr. Woodbury wanted the response in writing, so I am submitting this new LOI request on his behalf. Please let me know if you need anything. Best, Aminah From: John Woodbury <John.Woodbury@catawbacorps.com> Sent: Monday, December 15, 2025 4:21 PM To: INFOCNTR (PHMSA) <INFOCNTR.INFOCNTR@dot.gov> Subject: LOI 24-0124 Clarification CAUTION: This email originated from outside of the Department of Transportation (DOT). Do not click on links or open attachments unless you recognize the sender and know the content is safe. Your response is greatly appreciated. However, the response to my letter does not fully address my question. The most important part concerns whether 49 CFR 173.453(b) includes liquid as the payload. 49 CFR 173.453(b) states: An individual or bulk packaging containing 15 grams or less of fissile material provided the package has at least 200 grams of solid nonfissile material for every gram of fissile material. Lead, beryllium, graphite, and hydrogenous material enriched in deuterium may be present in the package but must not be included in determining the required mass for solid nonfissile material. Your response indicates that the packaging mass can be used to fulfill the solid nonfissile material requirement. Please clarify if 49 CFR 173.453(b) can have a liquid payload.#

Page 3Thanks, John B. “Woody” Woodbury Packaging Management Council Coordinator (509) 438-6342 John.woodbury@catawbacorps.com#