9.2 DOT HAZMAT Classification, Packaging & Testing

Interagency Coordination: DOT and NRC Regulatory Framework

The transportation of radioactive materials on public thoroughfares, railways, navigable waterways, and civil aircraft is governed by a coordinated regulatory framework between two federal agencies: the U.S. Department of Transportation (DOT) and the Nuclear Regulatory Commission (NRC). This relationship is codified in a formal Memorandum of Understanding (MOU):

• DOT Pipeline and Hazardous Materials Safety Administration (PHMSA): Promulgates and enforces regulations under Title 49 of the Code of Federal Regulations (49 CFR Parts 171 through 178). DOT regulates interstate and intrastate commercial carriage, vehicle safety, carrier responsibilities, driver qualifications, hazard communication (labeling, marking, placarding, shipping papers), and packaging standards for lower-activity shipments (Excepted and Type A packages).
• U.S. Nuclear Regulatory Commission (NRC): Promulgates and enforces regulations under 10 CFR Part 71 ("Packaging and Transportation of Radioactive Material"). The NRC serves as the technical authority that reviews, models, physically evaluates, and certifies package designs for higher-activity materials—specifically Type B packaging and fissile materials—issuing a federal Certificate of Compliance (CoC).
• DOT Certificate of Competent Authority (COCA): Because industrial radiography equipment moves across international boundaries, the DOT acts as the designated national "Competent Authority" under the International Atomic Energy Agency (IAEA) Safety Standards (Regulations for the Safe Transport of Radioactive Material, SSR-6). The DOT reviews the NRC Certificate of Compliance and issues a corresponding COCA certifying the package design for international import and export.

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Hazard Class 7 Classifications and UN Identification Numbers

Under DOT regulations (49 CFR 173.403), Hazard Class 7 is defined as any material containing radionuclides where both the activity concentration and the total activity in the consignment exceed specified regulatory exemption thresholds. In industrial radiography, commercial isotopes are assigned specific United Nations (UN) Identification Numbers that determine packaging, documentation, and emergency response protocols:

Hazard Class 7 UN Identifiers in Industrial Radiography:
  ├── UN 2916 ──> Radioactive material, Type B(U) package, non-fissile (Primary camera shipping designation)
  ├── UN 2915 ──> Radioactive material, Type A package, non-special form, non-fissile
  ├── UN 3332 ──> Radioactive material, Type A package, special form, non-fissile (Low-activity sources <= A1)
  ├── UN 2910 ──> Radioactive material, excepted package - limited quantity of material
  └── UN 2908 ──> Radioactive material, excepted package - empty packaging (Depleted uranium cameras without source)

Primary UN Designations in Field Operations

1. UN 2916 (Radioactive material, Type B(U) package, non-fissile or fissile-excepted): The standard proper shipping designation for commercial gamma exposure devices (such as the QSA Global Sentinel 880 Delta or SPEC 150) carrying operational industrial radiography sources (Ir-192, Co-60, or Se-75) whose activity exceeds the Type A threshold. The "(U)" signifies unilateral package design approval by the country of origin.
2. UN 3332 (Radioactive material, Type A package, special form, non-fissile): Applied when transporting Special Form radiography sources whose total activity does not exceed the radionuclide's specific $A_1$ value (such as small pipe-inspection sources, source-decayed calibrator sources, or low-activity crawler isotopes).
3. UN 2908 (Radioactive material, excepted package - empty packaging): Applied when returning or relocating an exposure device that does not contain a sealed source, but contains Depleted Uranium (DU) internal shielding. Under 49 CFR 173.428, an empty package containing DU is exempt from specification packaging, marking, and labeling, provided the external surface radiation level does not exceed 0.5 mrem/hr ($0.005\text{ mSv/hr}$), the internal surfaces are wiped clean ($< 2200\text{ dpm/100 cm}^2$ beta/gamma), and an internal notice is enclosed stating "Radioactive Material — Excepted Package — Empty Packaging".

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Special Form Encapsulation and $A_1 / A_2$ Activity Limits

Radiographic sources are classified under DOT regulations as either Special Form or Normal Form radioactive material (49 CFR 173.403). This physical classification determines the maximum activity that can legally be transported in a standard Type A container versus a heavy-duty Type B container.

Special Form Criteria and Rigorous Testing (49 CFR 173.469)

To qualify as Special Form Radioactive Material, the isotope must either be an indispersible solid metal cylinder or be encapsulated within a sealed capsule that can be opened only by destroying the capsule. Radiography sources (such as metallic Iridium-192 pellets) are double-encapsulated inside two hermetically laser-welded stainless steel or titanium capsules. To obtain a Special Form Certificate (Certificate of Competent Authority), the capsule design must survive the qualification tests of 49 CFR 173.469 without fragmenting, melting, or leaking:

1. Impact Test: The specimen is dropped onto the target from a height of 9 meters (30 feet), striking in the orientation expected to produce maximum damage. (The target is an essentially unyielding flat horizontal surface.)
2. Percussion Test: The specimen is placed on a sheet of lead supported by a smooth solid surface and struck by the flat face of a steel billet so as to produce an impact equivalent to a free drop of 1.4 kg (3.1 lb) through 1 meter.
3. Bending Test: Applied only to long, slender sources (length at least 10 cm and at least ten times the minimum width). The specimen is rigidly clamped horizontally so half its length projects, then struck by the flat face of a steel billet to produce an impact equivalent to a free drop of 1.4 kg through 1 meter onto the free end.
4. Heat Test: The specimen is heated in air to 800°C (1,475°F) and held at that temperature for 10 minutes.

Leaktightness Assessment: After the mechanical and thermal tests, the specimen must be assessed by a leaching test (for indispersible solids) or a volumetric leakage test, demonstrating that activity release does not exceed 2 kBq (0.05 microcurie).

Licensees must maintain valid copies of the source manufacturer's Special Form Certificate of Competent Authority on file for every sealed source model actively transported.

The Mathematical Threshold: $A_1$ and $A_2$ Values

The hazardous material regulations establish two activity limits for every radionuclide listed in 49 CFR 173.435:

• $A_1$ Value: The maximum activity of Special Form radioactive material permitted inside a non-accident-tested Type A package.
• $A_2$ Value: The maximum activity of Normal Form (dispersible powders, liquids, or unsealed solids) permitted inside a Type A package.

Why Industrial Radiography Cameras Mandate Type B Packaging

Notice the critical operational boundary: The $A_1$ limit for Special Form Iridium-192 is 27 Curies (1.0 TBq). However, a standard commercial radiography source is purchased at activities ranging from 50 to 120 Curies in order to penetrate thick industrial piping and pressure vessels. Because a 100-Curie Ir-192 source exceeds the 27-Curie $A_1$ threshold, federal law prohibits transporting it in a Type A package. It legally mandates packaging, testing, and transportation inside an NRC-certified Type B package (UN 2916).

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Package Engineering and Performance Testing: Type A vs. Type B

Packaging for radioactive material is engineered on a defense-in-depth philosophy: the integrity of the packaging must be proportional to the total potential hazard of the radiological payload.

Packaging Engineering Hierarchy:
  ┌────────────────────────────────────────────────────────────────────────┐
  │ Type A Packaging (Activity <= A1)                                      │
  │ Tested for Normal Conditions of Transport (NCT):                       │
  │ ├── Water spray (2 in/hr for 1 hr)                                     │
  │ ├── 4-foot free drop onto unyielding concrete                          │
  │ ├── 24-hour compression stack test (5x package weight)                 │
  │ └── Penetration test (13.2 lb bar dropped from 1 meter)                │
  └────────────────────────────────────────────────────────────────────────┘
                                     │
                                     ▼
  ┌────────────────────────────────────────────────────────────────────────┐
  │ Type B Packaging (Activity > A1)                                       │
  │ Tested for Hypothetical Accident Conditions (HAC) (Sequential):        │
  │ ├── 30-foot (9-meter) drop onto unyielding target in worst orientation │
  │ ├── 40-inch (1-meter) puncture drop onto 6-inch solid steel bar        │
  │ ├── 1475°F (800°C) thermal fire engulfment for 30 minutes              │
  │ └── Water immersion test (3 ft for 8 hrs; 50 ft for large quantity)    │
  └────────────────────────────────────────────────────────────────────────┘

Type A Package Qualification: Normal Conditions of Transport (NCT)

Under 49 CFR 173.465, prototype Type A containers must undergo rigorous simulation of rough handling and adverse weather encountered during normal commercial transport without breach of containment or loss of radiation shielding:

1. Water Spray Test: The package is subjected to a continuous water spray simulating heavy rainfall of approximately 2 inches (50 mm) per hour for at least 1 hour.
2. Free Drop Test: Within 1.5 to 2.5 hours following the water spray, the package must be dropped from a height of 4 feet (1.2 meters) onto a flat, unyielding horizontal concrete target in the orientation expected to produce maximum damage.
3. Compression / Stacking Test: The package must withstand for a duration of 24 hours a compressive compressive load equal to either 5 times the actual package weight or $13\text{ kPa}$ ($1.9\text{ psi}$) multiplied by the vertical projected area of the package.
4. Penetration Test: A 6 kg (13.2 lb) cylindrical steel bar with a hemispherical end (1.25 inches in diameter) is dropped vertically from a height of 1 meter (3.3 feet) onto the center of the weakest surface of the package.

Type B Package Qualification: Hypothetical Accident Conditions (HAC)

Type B packaging—represented by modern industrial radiography exposure devices and specialized transport overpacks—must be physically capable of surviving catastrophic transportation collisions, highway overturns, and multi-vehicle fuel fires. Under 10 CFR 71.73 and 49 CFR 173.467, prototype Type B packaging must withstand a cumulative, sequential battery of destructive tests on the identical specimen:

1. 30-Foot (9-Meter) Free Drop: The package is dropped from 30 feet onto a massive, flat, completely unyielding horizontal surface (such as a 10-ton steel armor plate mounted on solid bedrock) striking in an orientation engineered to produce maximum structural and locking failure.
2. Puncture Bar Drop: Immediately following the 30-foot drop, the damaged package is dropped from a height of 40 inches (1 meter) onto the top face of a solid, vertical cylindrical mild steel bar (6 inches in diameter and at least 8 inches tall) mounted to the unyielding target, striking the exposure device lock mechanism, outlet port, or depleted uranium shell.
3. Thermal Engulfment Fire Test: The structurally damaged package is engulfed completely in a hydrocarbon fuel-air fire providing a minimum heat flux equivalent to a furnace temperature of 800°C (1,475°F) for a continuous period of 30 minutes.
4. Water Immersion Test: The package is submerged under a head of water of at least 3 feet (0.9 meters) for not less than 8 hours. Furthermore, under 10 CFR 71.73(c)(6), an undamaged package must withstand deep-water immersion under 50 feet (15 meters) of water for 8 hours without structural collapse.

To pass Type B certification, the post-test package must demonstrate that radioactive containment remains absolute, and that external radiation levels do not exceed 1 rem/hr (10 mSv/hr) at 1 meter from the package surface.

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Overpacks, Secondary Shipping Enclosures & Tamper Seals

When transporting an exposure device inside a vehicle, licensees frequently place the camera inside a heavy-duty steel or plastic overpack, or bolt it inside a secondary transport enclosure (49 CFR 171.8). An overpack provides physical protection and mechanical stabilization.

Overpack Marking and Labeling Rules (49 CFR 173.25)

If the warning labels and proper shipping markings on the internal exposure device are obscured from view when placed inside an overpack or transport box, the exterior of the overpack must be labeled and marked identically to the internal package. Furthermore, the outside of the enclosure must be clearly stenciled with the word "OVERPACK" in lettering at least 0.5 inches (12 mm) high.

Tamper-Indicating Seals (49 CFR 173.412)

Every radioactive materials package transported on public highways must incorporate an unbroken, tamper-indicating seal (such as a serialized wire-and-lead crimp seal, or numbered security tape). The seal must be installed across the camera lock box, outer lid, or overpack latch. The seal serves as incontrovertible physical evidence that unauthorized personnel have not opened, tampered with, or accessed the exposure device during highway transit.