UN3327 and UN3333: Shipping Fissile Radioactive Material in Type A Packages

Why Fissile Type A Matters

Most radioactive material shippers never encounter UN3327 or UN3333. These UN numbers are for a narrow but critical slice of the shipping universe: fissile material — isotopes that can sustain a nuclear chain reaction — that does not qualify for any of the fissile exemptions in 49 CFR 173.453.

The regulations treat fissile material differently because the hazard is fundamentally different. With most radioactive material, the concern is radiation exposure and contamination. With fissile material, there is an additional concern: criticality — the possibility that enough fissile material could accumulate in one place to start an uncontrolled nuclear chain reaction. That is why fissile packages get additional requirements that non-fissile packages do not: a Criticality Safety Index (CSI), accumulation limits, and nuclear criticality safety evaluations.

That said, most shippers of fissile material work with small enough quantities that they qualify for a fissile exemption — which means they use UN2915 or UN3332 like everyone else. UN3327 and UN3333 come into play when the fissile mass is too large for any exemption, which typically means fuel fabrication facilities, enrichment plants, and certain research reactors.

What Is Fissile Material?

Under 49 CFR 173.403, fissile material means:

• Plutonium-238 (Pu-238)
• Plutonium-239 (Pu-239)
• Plutonium-241 (Pu-241)
• Uranium-233 (U-233)
• Uranium-235 (U-235)
• Any combination of these

Of these five isotopes, U-235 is by far the most commonly shipped. It appears in enriched uranium fuel, research reactor fuel, high-assay low-enriched uranium (HALEU), and highly enriched uranium (HEU). Pu-239 is the second most common, found in mixed oxide (MOX) fuel and plutonium-bearing research materials. The others are less frequently encountered in commercial shipping.

When Do You Not Need the Fissile UN Numbers?

Before concluding that your shipment requires UN3327 or UN3333, check whether it qualifies for a fissile exemption under 49 CFR 173.453. If it does, you use the non-fissile UN numbers (UN2915 or UN3332) and skip all fissile-specific requirements.

The most commonly used fissile exemptions include:

The majority of fissile material shipments I have seen in my career qualified for one of these exemptions — most commonly (a) or (b). If you are shipping a few grams of enriched uranium for analysis, or calibration sources containing small amounts of Pu-239, you almost certainly qualify. It is only when you get into significant quantities — fuel assemblies, large research reactor targets, bulk enriched material — that you need UN3327 or UN3333.

What Qualifies for UN3327 or UN3333?

You use these UN numbers when all of the following are true:

1. Material contains fissile isotopes — Pu-238, Pu-239, Pu-241, U-233, or U-235
2. Material does NOT qualify for any fissile exemption under 49 CFR 173.453
3. Activity exceeds excepted package limits but does not exceed A1 (special form) or A2 (normal form)

Then choose the UN number based on material form:

• Normal form → UN3327 (activity limit ≤ A2)
• Special form → UN3333 (activity limit ≤ A1)

If the activity exceeds A1 or A2, you need fissile Type B packaging — UN3328 (Type B(U), fissile) or UN3329 (Type B(M), fissile). These are among the most heavily regulated shipments in hazmat transportation.

What's Different About Fissile Type A?

UN3327 and UN3333 carry all the same requirements as their non-fissile counterparts (UN2915 and UN3332) plus additional fissile-specific requirements:

Criticality Safety Index (CSI)

Every fissile package is assigned a Criticality Safety Index. The CSI limits how many fissile packages can be accumulated in one place during transport. A lower CSI means more packages can be grouped together; a higher CSI means fewer. The CSI must appear on the FISSILE label applied to the package.

Fissile Label

In addition to the standard radioactive category label (I-White, II-Yellow, or III-Yellow), fissile packages require a separate FISSILE label showing the CSI. This label is placed on two opposite sides of the package, alongside the radioactive labels.

Package Design Approval

Fissile Type A packages require either:

• A fissile package design approval from the NRC (or the competent authority of the country of origin), OR
• General license provisions under 10 CFR 71.22 for certain fissile materials in Type A quantities

This is a significant difference from non-fissile Type A packages, which are self-certified. For fissile packages, you typically need either an NRC-approved package design or must demonstrate compliance with the general license conditions — which include limits on fissile mass per package and in-transit accumulation.

Shipping Paper Entries

In addition to the standard shipping paper entries, fissile shipments must include:

• The UN number (UN3327 or UN3333) and its proper shipping name
• The CSI for each package
• The fissile mass per package
• Reference to the NRC certificate of compliance (if applicable)

UN3327 vs. UN3333: Which One?

The distinction mirrors the non-fissile pair:

In practice, UN3327 is more common because most fissile material shipped in these quantities — enriched uranium in solution, uranium compound powders, plutonium-bearing waste — is in normal form. UN3333 would apply to a certified sealed source containing fissile material at quantities above the exemption limits, which is uncommon but not unheard of in fuel fabrication and research reactor operations.

The Complete Type A Family

Here is how all four Type A UN numbers fit together:

Most shippers will only ever use the left column. If you are shipping fissile material at quantities above the exemption thresholds, you are almost certainly working within a nuclear facility with criticality safety staff, approved procedures, and NRC-licensed packages. These are not shipments where you figure it out from a guide — they are shipments where the criticality safety analysis drives the packaging and shipping decisions.

My advice: if you are not sure whether your fissile material qualifies for an exemption, start with 49 CFR 173.453 and work through the exemption criteria. Most small-quantity shippers — labs, universities, medical facilities — will find that their material falls under exemption (a) (2 grams or less per package) or exemption (b) (15 grams or less). In those cases, you are back to UN2915 or UN3332 and the fissile-specific requirements do not apply.

How RadShip.com Helps

RadShip.com evaluates fissile exemptions automatically as part of the classification workflow:

• RAMcalc — identifies fissile isotopes, checks all applicable exemptions under 49 CFR 173.453, and determines whether the material ships as fissile-excepted (UN2915/UN3332) or fissile (UN3327/UN3333)
• Enrichment input — for uranium shipments, enter the enrichment percentage and RAMcalc evaluates the enrichment-specific exemptions in 173.453(c) and (d)
• Fissile mass derivation — when you enter activity in grams, RAMcalc automatically computes the fissile mass using specific activity, so you don't need to calculate it separately

The fissile exemption evaluation is one of the most complex parts of Class 7 classification. Let the calculator work through the criteria systematically. Try it free for 7 days.

Common Questions

What is the difference between UN3327 and UN2915?

Fissile status. Both are Type A, non-special form, with an A2 activity limit. UN3327 contains fissile material that does not qualify for a fissile exemption. UN2915 is either non-fissile or the fissile content qualifies for an exemption. The practical difference is that UN3327 requires a CSI label, fissile package design approval (or general license), and additional shipping paper entries.

Can I ship enriched uranium under UN2915?

Yes, if the fissile content qualifies for an exemption. For example, if you have 1 gram of 3% enriched U-235 in a package, that is 0.03 grams of U-235 — well under the 2-gram exemption in 173.453(a). You would ship as UN2915 (assuming normal form) with no fissile-specific requirements. The exemption determination is about the fissile isotope mass, not the total uranium mass.

Are there fissile versions of LSA or SCO UN numbers?

No. There are no fissile versions of UN2912 (LSA) or UN2913 (SCO). Fissile material that does not qualify for a fissile exemption cannot be classified as LSA or SCO. It must use the fissile Type A (UN3327/UN3333) or fissile Type B (UN3328/UN3329) UN numbers.

What if my fissile material exceeds Type A limits?

You need fissile Type B packaging. That means UN3328 (Type B(U), fissile) or UN3329 (Type B(M), fissile). These require NRC-approved package designs that have been evaluated for both accident conditions and criticality safety. These are among the most regulated packages in transportation.

Summary: Your Fissile Type A Checklist

Before shipping under UN3327 or UN3333, verify:

• ☐ Material contains fissile isotopes (Pu-238, Pu-239, Pu-241, U-233, or U-235)
• ☐ Material does NOT qualify for any fissile exemption under 49 CFR 173.453
• ☐ Activity is within Type A limits (A2 for UN3327, A1 for UN3333)
• ☐ Package meets Type A design requirements (49 CFR 173.412)
• ☐ Package has NRC fissile design approval or qualifies under general license (10 CFR 71.22)
• ☐ Criticality Safety Index (CSI) has been determined
• ☐ FISSILE label applied with CSI on two opposite sides
• ☐ Radioactive category label applied (I-White, II-Yellow, or III-Yellow) on two opposite sides
• ☐ Package marked with UN number (UN3327 or UN3333), proper shipping name, shipper/consignee
• ☐ Shipping paper includes fissile mass, CSI, and NRC certificate reference
• ☐ 24-hour emergency response telephone number on shipping paper
• ☐ Transport Index calculated and recorded
• ☐ Nuclear criticality safety evaluation completed and documented
• ☐ If special form (UN3333): valid special form certificate on file

Regulatory References

Fissile-Specific:

• 49 CFR 173.403 — Definition of fissile material
• 49 CFR 173.453 — Fissile material exemptions
• 49 CFR 173.457 — Transportation of fissile material packages
• 10 CFR 71.22 — General license for fissile material (Type A quantities)

Classification and Limits:

• 49 CFR 173.435 — Table of A1 and A2 values
• 49 CFR 173.431 — Activity limits for Type A packages

Packaging and Design:

• 49 CFR 173.412 — Type A package design requirements
• 49 CFR 173.469 — Special form qualification criteria

Marking and Labeling:

• 49 CFR 172.101 — Hazardous materials table (UN numbers and PSNs)
• 49 CFR 172.403 — Radioactive material label requirements (includes FISSILE label)