A1 and A2 Values Explained: The Key to RAM Classification

Why A1 and A2 Values Matter

A1 and A2 values are the foundation of radioactive material classification. They determine whether you can ship in a simple excepted package, a Type A package, or whether you need a Type B package with NRC approval. Get this wrong, and you might ship material in packaging that can't contain it safely during an accident—or you might over-package and waste thousands of dollars on unnecessary Type B containers.

A1 and A2 values are used to calculate if a shipment qualifies for the Limited Quantity or “Excepted Package” designation, which gives the shipper the ability to ship in regular shipping boxes rather than a Type A or Type B spec package. The package could be as simple as a cardboard box. Labels and shipping papers are also not required for excepted packages in most situations—a significant reduction in paperwork and cost.

These values aren't arbitrary. They're calculated based on the radiological hazard of each nuclide—how much radiation it emits, what type, and how dangerous it would be if released. Understanding A1 and A2 values means understanding why certain materials require more robust packaging than others.

Who Needs to Know This

This applies to anyone who:

• Classifies radioactive material for shipment
• Selects packaging for radioactive shipments
• Prepares shipping papers for RAM
• Receives and inspects radioactive shipments
• Manages radioactive material shipping programs

If you're performing any of these functions, you must also have proper DOT hazmat training under 49 CFR 172 Subpart H.

Understanding A1 and A2 Values

A1 and A2 values are defined in 49 CFR 173.403 and the specific values for each radionuclide are listed in 49 CFR 173.435 (Table A-1). Let's break down what each means.

What is the A1 Value?

The A1 value is the maximum activity of special form radioactive material that can be transported in a Type A package. Special form means the material is either:

• An indispersible solid (won't break apart or release contamination)
• A sealed capsule containing radioactive material

Because special form material can't easily disperse, it poses less inhalation and ingestion risk. Therefore, A1 values are typically higher than A2 values—you can ship more activity in a Type A package.

It is crucial that a shipper obtain a special form certificate if shipping A1 special form. These certificates are dated and do have expiration dates. Without the special form certificate, you should only ship the material as A2 or “normal form.” This is important because the activity limits for special form sources are set much higher. If you have to ship as normal form material, it may put you into having to ship in a Type B container, which is very expensive and has additional requirements.

What is the A2 Value?

The A2 value is the maximum activity of normal form (also called “other than special form”) radioactive material that can be transported in a Type A package. Normal form includes:

• Liquids
• Powders
• Gases
• Unsealed sources
• Any material not certified as special form

Because normal form material could disperse if the package is breached, A2 values are typically lower than A1 values—reflecting the greater hazard if released.

Why Do Different Nuclides Have Different Values?

Each radionuclide poses a different level of hazard based on:

• Type of radiation: Alpha, beta, gamma, neutron
• Energy of radiation: Higher energy = more penetrating
• Half-life: Affects how long the hazard persists
• Biological uptake: How the body absorbs and retains it
• Dose conversion factors: Radiation dose per unit activity

For example, Tc-99m (used in medical imaging) has an A2 of 10 TBq, while Am-241 has an A2 of only 0.001 TBq. Americium is far more hazardous per becquerel due to its alpha emission and bone-seeking properties.

The biggest mistake shippers make when calculating a shipment using A1 and A2 values is basic math errors. Most A1 and A2 values are expressed in scientific notation, which for most people is not commonly used in everyday life. It's also common for isotope or radionuclide activity to be expressed in scientific notation. This is where a software application like RadShip.com's RAMcalc really shines—it can handle hundreds of radionuclides, compare them to the A1/A2 values, and perform the sum of fractions instantly.

Example A1 and A2 Values

Here are some common radionuclides and their A1/A2 values (always verify current values in 49 CFR 173.435):

Notice how Am-241 has the same A1 as Tc-99m (10 TBq), but its A2 is 10,000 times lower. This reflects the extreme hazard of inhaling or ingesting alpha-emitting americium.

How A1/A2 Values Determine Package Type

The relationship between your material's activity and the applicable A1 or A2 value determines what package type you need:

There really are no shortcuts for calculating a RAM package for compliance. Experienced shippers will typically be able to remember the most common radionuclides' A1 and A2 values—like Cs-137 and Co-60—and know when they are exempt, limited quantity, Type A, or Type B. But things start getting complicated when shipping multiple isotopes.

A1/A2 Values for Mixtures

When you have multiple radionuclides in a single package, you can't simply add up the activities. Instead, you must calculate a weighted A1 or A2 value using the “sum of fractions” method described in 49 CFR 173.433.

The formula is:

A_m = 1 / Σ(f_i / A_i)

Where:

• f_i = fraction of total activity for nuclide i
• A_i = A1 or A2 value for nuclide i
• A_m = effective A1 or A2 for the mixture

This calculation can get complex quickly. Consider this example: a facility is shipping a sealed source containing both Cs-137 and a small amount of Am-241 (common in some older calibration sources). The shipment contains 50 GBq of Cs-137 (A2 = 600 GBq) and 0.5 GBq of Am-241 (A2 = 1 GBq). The shipper might assume, “The Am-241 is only 1% of the total activity, so it shouldn't matter much.” But when you run the sum of fractions—Cs-137 contributes 50 ÷ 600 = 0.083, while Am-241 contributes 0.5 ÷ 1 = 0.500—the total is 0.583. Even though Am-241 represents only 1% of the total activity, it contributes 86% of the sum of fractions because its A2 value is 600 times more restrictive. A shipper who ignored the “trace” Am-241 could significantly under-classify the package.

Special Form: When A1 Applies

To use the A1 value (instead of A2), your material must be certified as special form. This certification isn't just a claim—it requires documented evidence that the source meets specific criteria under 49 CFR 173.469.

Special Form Requirements

• Material is either solid and non-dispersible, or enclosed in a sealed capsule
• Capsule/material can withstand impact, percussion, bending, and heat tests
• Manufacturer provides a certificate documenting compliance
• Certificate must be kept on file

Just because a source you are shipping is encapsulated and appears to be special form does not mean it has a current special form certificate. Always verify the documentation before claiming A1.

How RadShip.com Helps

RadShip.com simplifies A1/A2 calculations by:

• RAMcalc – Automatically looks up A1/A2 values for your radionuclides. No table hunting required.
• Special Form toggle – Select whether your material is special form, and RAMcalc uses the appropriate value (A1 or A2).
• Mixture Mode – Calculates effective A1/A2 for multi-nuclide materials using the sum-of-fractions formula.
• Package type determination – Tells you exactly what package type is required based on your activity and A1/A2 comparison.

When you're shipping radioactive material, there's no room for error—an incorrect classification can result in regulatory violations, rejected shipments, or worse, a safety incident. Manual calculations using the A1/A2 tables require looking up values, converting units, handling scientific notation, and performing sum-of-fractions math for mixtures. Each step is an opportunity for mistakes. An automated tool like RAMcalc eliminates these errors, provides consistent results every time, and maintains a current database of A1/A2 values so you're always working with the latest regulatory data. For facilities that ship frequently, automation also saves significant time—what might take 15-20 minutes to calculate manually is done in seconds.

Try it free for 7 days.

Common Questions

Why are A1 and A2 values expressed in TBq?

TBq (terabecquerels) is the SI unit for large activities. The values are also listed in Curies (Ci) in parentheses in 49 CFR 173.435. Both units are acceptable for shipping documentation.

What if my radionuclide isn't listed in the table?

Use the “unknown” values. Table A-1 includes conservative values for unlisted nuclides based on whether the emission type is known. These values are intentionally low to ensure safety.

Can I ever use A1 for liquids?

No. Liquids are always normal form. A1 only applies to special form materials, which by definition must be solid or in a sealed capsule that meets specific test criteria.

Do A1/A2 values change over time?

Rarely, but yes. The values are updated when new scientific data warrants changes. Always use the current version of 49 CFR 173.435. RadShip.com's database is kept current with regulatory updates.

What's the difference between A2 and the exempt activity (ALEC)?

Different thresholds for different purposes. ALEC (Activity Limit Exempt for Consignments) determines if material is regulated at all—see our guide on What is Radioactive Material per DOT? for details on exempt thresholds. A2 determines package type for regulated materials. ALEC values are typically much lower than A2 values.

My advice for new shippers: have an experienced shipper review your shipping paperwork and calculations before you certify the package and release it to the carrier. RAMcalc allows you to print off the values used in each calculation for easy review.

Summary: Your A1/A2 Checklist

Before selecting package type, ensure:

• ☐ Identify all radionuclides in your shipment
• ☐ Look up A1 and A2 values in 49 CFR 173.435
• ☐ Determine if material is special form (A1) or normal form (A2)
• ☐ For mixtures, calculate effective A1 or A2 using sum of fractions
• ☐ Compare your total activity to the applicable A1 or A2
• ☐ Select package type based on the ratio (excepted, Type A, or Type B)
• ☐ Document special form certification if claiming A1

Or skip the manual work and use RAMcalc to handle all of this automatically.

Regulatory References

DOT Requirements:

• 49 CFR 173.403 – Definitions (A1, A2, special form, normal form)
• 49 CFR 173.435 – Table of A1 and A2 values
• 49 CFR 173.433 – Requirements for determining A values for mixtures
• 49 CFR 173.469 – Tests for special form radioactive materials
• 49 CFR 173.412 – Additional requirements for Type A packages

NRC Requirements:

• 10 CFR 71 – Packaging and transportation of radioactive material (Type B approval)

IATA (Air Transport):

• IATA Dangerous Goods Regulations, Table 10.3.A – A1/A2 values (aligns with DOT)