NRC Medical-Use License Amendments

A radioactive material license is not a one-time approval—it is a living document that must be kept current as the program changes. Adding an authorized user, a new radionuclide, a new imaging room, or a higher possession limit can require an NRC (or Agreement State) license amendment before the change is made, while other changes require only a notification after the fact. Confusing the two is one of the most common—and most avoidable—compliance findings in medical-use programs.¹²

This article maps the amendment triggers of 10 CFR 35.13 against the notification provisions of 10 CFR 35.14, works a possession-limit example that shows why decay-in-storage matters to the request, and lays out a practical process for keeping a medical-use license defensible.

Introduction

Most radiation safety officers inherit a license, not a blank slate. Over time the program evolves: a new physician wants to become an authorized user, the practice adds a theranostics agent, a room is repurposed, patient volume grows, or the RSO retires. Each of these is a change to the assumptions on which the license was granted—and the regulations are explicit about which changes the licensee may make on its own authority and which require the regulator's prior approval.¹²

The stakes are practical. Permitting a physician to administer therapy before the authorized-user amendment is granted, or using a radionuclide the license does not list, is not a paperwork technicality—it is unauthorized use of licensed material. Conversely, submitting an amendment for something that only needed a notification wastes time and review resources. Knowing the boundary is core RSO competence.⁶

DRPS supports medical-use licensees with this work as part of radioactive material license support and radiation safety officer consulting across Florida, Maryland, Virginia, Washington DC, California, Nevada, and our other service areas. For the foundational picture, see our NRC materials license guide.

Topic Explanation

The license as a set of conditions

A medical-use license authorizes specific radionuclides, for specific types of use, at specific addresses, by specific authorized individuals, up to specific possession limits. Each of those five dimensions is a condition. An amendment is how a condition is changed with the regulator's approval; a notification is how the licensee informs the regulator of certain changes that do not require prior approval.¹²

The governing rules are compact:

• 10 CFR 35.13 — License amendments. Enumerates the changes for which a licensee "shall apply for and must receive a license amendment" before acting.¹
• 10 CFR 35.14 — Notifications. Enumerates changes the licensee must report, generally within 30 days, without a prior amendment.²
• 10 CFR 30.34 — Terms and conditions of licenses. Includes the requirement for NRC prior written consent before transferring control of a license (a corporate change of control is not a simple amendment).⁴
• 10 CFR 30.37 — Application for renewal. Establishes timely renewal, distinct from amendment.⁵

Amendment before the change

The defining feature of 10 CFR 35.13 is the phrase before. A licensee must apply for and receive the amendment before it makes the change. Filing the request is not enough; the change waits for the grant.¹

Key Technical Principles

10 CFR 35.13 versus 10 CFR 35.14 at a glance

The single most useful thing an RSO can internalize is which bucket a given change falls into. The table summarizes the high-confidence, common cases; the authoritative, fully enumerated lists live in the regulations themselves, and a few triggers have shifted between the two categories across Part 35 revisions, so confirm the current rule for any borderline case.¹²⁶

Why possession limits require a real calculation

When an amendment raises a possession limit or adds a radionuclide, the requested limit must realistically cover the maximum activity present at any one time—not just a single dose. That total includes freshly received doses, residual activity from earlier deliveries that has not yet decayed, and used vials and waste held in decay-in-storage. Decay-in-storage is itself governed by rule: under 10 CFR 35.92, a licensee may hold byproduct material with a physical half-life of less than 120 days for decay and then dispose of it as ordinary waste after holding it for at least 10 half-lives, provided it is surveyed and reads indistinguishable from background (and any radioactive labels are removed or defaced).³

The activity remaining after a storage interval $t$ follows simple exponential decay:

$$A(t)=A_0{e}^{-\lambda t},\lambda =\frac{\ln 2}{T_{1/2}}$$

Worked example. For I-131 ($T_{1/2}=8.02$ days), the ten-half-life decay-in-storage hold time is:

$$t=10\times T_{1/2}=10\times 8.02\text{days}\approx 80.2\text{days}$$

and the fraction of the original activity remaining after ten half-lives is:

$$\frac{A(t)}{A_0}={\left(\frac{1}{2}\right)}^{10}=\frac{1}{1024}\approx 0.098\%$$

The practical consequence for an amendment: if a therapy program receives up to, say, two 1.11 GBq (30 mCi) I-131 doses per week and must hold used vials and contaminated waste for roughly 80 days before disposal, the material physically present at any moment—new doses plus weeks of decaying waste in the storage area—can substantially exceed a single dose. A possession limit set to "one dose" would be exceeded almost immediately. The amendment request should therefore justify the possession limit against realistic inventory and decay-in-storage accumulation, not a best-case snapshot. This is exactly the kind of source-term reasoning a medical physicist brings to a license request.

Renewal is not amendment

Licensees sometimes conflate renewal with amendment. Renewal extends the license term; amendment changes its conditions. Under 10 CFR 30.37, filing a complete renewal application at least 30 days before expiration invokes timely renewal: the existing license remains in effect until the regulator acts, even past the printed expiration date.⁵ Both renewal and amendment are submitted on NRC Form 313, but they answer different questions and should not be bundled carelessly.⁵⁶

Common amendment scenarios in a medical program

A handful of requests account for most medical-use amendments, and recognizing them early shortens the timeline:

• Adding a diagnostic radiopharmaceutical or a new PET agent. If the radionuclide or type of use is not already authorized, an amendment is required before the first dose is received or prepared.
• Launching a therapy service (for example, a Lu-177 radioligand program). This typically combines several conditions at once—new radionuclide, a qualified authorized user, adequate possession limits, dedicated procedures, and often a designated treatment or waste-storage area—so it is best treated as a coordinated package rather than a series of piecemeal requests.
• Adding a new authorized user. The most common single amendment; the reviewer needs the physician's training-and-experience documentation or board certification.
• Opening or relocating a use area. A new imaging suite or a moved hot lab changes the address or area of use and requires an amendment before use.
• Changing the RSO. Handled through the notification-and-amendment pathway with provision for a temporary RSO so the program is never without radiation-safety oversight.

Grouping related changes into a single, well-documented submission—rather than filing them one at a time as they arise—reduces review cycles and keeps the license internally consistent.⁶

Clinical Impact

Keeping the license current is what lets the clinical program actually operate—and what keeps it out of enforcement trouble. The operational reality is that clinical initiatives frequently run ahead of the license. A hospital recruits an interventional cardiologist who wants to read cardiac studies, an oncology practice signs on to a new radioligand therapy, or a growing imaging center opens a second suite. Each of these must be reflected in the license before the activity begins, and the lead time for an amendment—assembling training-and-experience documentation, drafting procedures, and awaiting review—can be weeks.⁶

Programs that treat the license as static routinely discover the gap at the worst moment: during an inspection, when a new authorized user has already been administering therapy, or when a radionuclide on the shelf is not on the license. Building amendment lead time into clinical planning—so the paperwork is granted before the first patient—is the difference between a smooth service launch and a notice of violation. For broad-scope licensees, some of these changes are handled internally through the Radiation Safety Committee rather than by amendment, which is one of the advantages of a Part 33 broad-scope license.

Practical Optimization Tips

1. Maintain a "license map"

Keep a one-page current summary of what the license authorizes—radionuclides, uses, addresses, authorized individuals, possession limits, and expiration date—so any proposed program change can be checked against it instantly.

2. Screen every change through the 35.13/35.14 question

Before any new physician, radionuclide, room, or volume increase, ask explicitly: does this need an amendment before we act, a notification after, or nothing? Document the determination.

3. Assemble authorized-user packages early

Training-and-experience documentation and board certification are the most common amendment bottleneck. Start collecting them as soon as a physician expresses interest, not after they arrive.

4. Right-size possession limits

Request limits that cover realistic peak inventory including decay-in-storage, so routine growth does not force repeated amendments—while avoiding limits so high they raise security or emergency-planning obligations.

5. Calendar the renewal

Track the expiration date and file a complete renewal at least 30 days early to preserve timely-renewal protection under 10 CFR 30.37.⁵

Common pitfalls to avoid

• Acting before the amendment is granted. Filing is not receiving; 35.13 requires prior approval.¹
• Using a notification for an amendment-required change. The 30-day letter does not cover new users, new uses, new addresses, or higher limits.¹²
• Forgetting transfer-of-control consent. A corporate acquisition needs 10 CFR 30.34 prior written consent, not a routine amendment.⁴
• Setting possession limits by single-dose thinking. Decay-in-storage inventory accumulates.³
• Letting the license lapse. Missing the 30-day timely-renewal window can interrupt authorized operations.⁵

Regulatory Considerations

The amendment framework is federal in structure but administered by whichever authority issued the license. Medical use of byproduct material is governed by 10 CFR Part 35 for NRC licensees; Agreement States administer compatible programs.¹²⁶

• 10 CFR 35.13 and 35.14 define the amendment and notification triggers.¹²
• NRC Form 313 is the application vehicle for new licenses, amendments, and renewals; reference the existing license number and describe the requested change.⁷
• NUREG-1556, Volume 9 is the consolidated guidance the reviewer uses—it tells you what documentation each type of amendment request should contain.⁶
• 10 CFR 30.34 and 30.37 cover transfer-of-control consent and timely renewal, respectively.⁴⁵
• Jurisdiction. Of the states DRPS serves, Florida, Maryland, Virginia, California, Nevada, Pennsylvania, New York, and New Jersey are NRC Agreement States that license medical use under their own compatible rules, while Washington DC and Delaware are regulated directly by the NRC. X-ray machines, by contrast, are FDA and state-regulated, not licensed under Part 35. Always verify submission specifics with the authority that issued your license.

Documented determinations, complete Form 313 packages, and adequate lead time are what make amendment management defensible during inspection. DRPS aligns these with day-to-day operations through radioactive material license support, RSO consulting, and medical physicist consulting; requirements vary by authority, so confirm with the authority having jurisdiction.

Frequently Asked Questions (FAQs)

What is a license amendment?

A license amendment is a formal, NRC- (or Agreement State-) approved change to the conditions of an existing radioactive material license—such as adding an authorized user, a new radionuclide or type of use, a new area or address of use, or a higher possession limit. For many changes, 10 CFR 35.13 requires the licensee to apply for and receive the amendment before making the change; making the change first is a violation.

What is the difference between an amendment and a notification?

An amendment (10 CFR 35.13) must be requested and granted before certain changes take effect. A notification (10 CFR 35.14) is a letter the licensee sends the NRC, typically within 30 days after certain changes—such as a licensee name or mailing-address change, or an authorized user or RSO discontinuing duties. The distinction matters: doing an amendment-required change on a notification timeline is a compliance failure.

Which changes require an amendment before you act?

Generally: receiving, preparing, or using byproduct material for a type of use permitted under Part 35 but not authorized on the current license; adding or changing the address(es) or areas of use; permitting a new authorized user, authorized medical physicist, or authorized nuclear pharmacist to work (with limited exceptions); increasing the possession limit; and changing an Associate RSO's assigned duties. The full, enumerated list is in 10 CFR 35.13.

How do you submit an amendment?

Amendments are submitted using NRC Form 313 (or the Agreement State equivalent), referencing the existing license number, describing the requested change, and attaching supporting documentation—for example, an authorized user's training and experience, board certification, or an updated procedure. NUREG-1556 Volume 9 describes what the reviewer expects for each type of request.

What is timely renewal and how does it relate to amendments?

Under 10 CFR 30.37, if a licensee files a complete renewal application at least 30 days before the license expires, the existing license does not expire until the NRC acts on the renewal—this is "timely renewal." A renewal is not the same as an amendment: renewal extends the license term, while an amendment changes its conditions. Both use NRC Form 313.

Do Agreement States follow the same rules?

Agreement States administer their own compatible regulations, which generally mirror 10 CFR Part 35, including the amendment-versus-notification structure, but forms, fees, and submission portals differ. Of the states DRPS serves, most are NRC Agreement States, while Washington DC and Delaware are regulated directly by the NRC. Always verify with the authority that issued your license.

Key Takeaways

• A license is a set of conditions. Radionuclides, uses, addresses, authorized individuals, and possession limits each define what you may do.¹
• Amendment means "before." 10 CFR 35.13 requires prior NRC approval for new uses, new users, new addresses, and higher limits.¹
• Notification means "after." 10 CFR 35.14 covers name/address changes and departures, typically within 30 days.²
• Possession limits need a real calculation. Peak inventory includes decay-in-storage; I-131 waste is held about 80 days (ten half-lives) before disposal.³
• Renewal ≠ amendment. File a renewal at least 30 days early to keep timely-renewal protection under 10 CFR 30.37.⁵
• Verify your jurisdiction. Agreement States mirror Part 35 but differ in process; DC and Delaware are direct-NRC.⁶

Conclusion

The difference between a well-run medical-use program and a chronic source of violations often comes down to license hygiene: knowing which changes need an amendment before you act, which need a notification after, and which need something else entirely. 10 CFR 35.13 and 35.14 draw that line, NUREG-1556 Volume 9 tells you how to document each request, and NRC Form 313 carries it. Treat the license as a living document, build amendment lead time into clinical planning, size possession limits against realistic inventory, and keep the renewal calendared—and the license becomes an enabler of the clinical program rather than a liability waiting to surface at the next inspection.

How DRPS Can Help

Diagnostic Radiation Physics Services helps medical-use licensees keep their licenses current and defensible: screening proposed program changes against the amendment-versus-notification rules, assembling authorized-user training-and-experience packages, drafting amendment and renewal submissions on NRC Form 313, right-sizing possession limits with source-term and decay-in-storage reasoning, and preparing programs for the inspection that follows. This is delivered through radioactive material license support, radiation safety officer consulting, and medical physicist consulting.

DRPS supports facilities across our service locations, including Florida, Maryland, Virginia, Washington DC, California, Nevada, New York, Pennsylvania, New Jersey, and Delaware, with work performed by board-certified medical physicists.

Related Resources

• NRC materials license guide
• NRC broad-scope medical license (Part 33)
• NRC Part 35 recordkeeping requirements
• Decommissioning and license termination
• NRC enforcement process: violations and penalties
• Radioactive material license support
• Radiation Safety Officer consulting

References

1. U.S. Nuclear Regulatory Commission. 10 CFR 35.13: License amendments. nrc.gov
2. U.S. Nuclear Regulatory Commission. 10 CFR 35.14: Notifications. nrc.gov
3. U.S. Nuclear Regulatory Commission. 10 CFR 35.92: Decay-in-storage. nrc.gov
4. U.S. Nuclear Regulatory Commission. 10 CFR 30.34: Terms and conditions of licenses. nrc.gov
5. U.S. Nuclear Regulatory Commission. 10 CFR 30.37: Application for renewal of license. nrc.gov
6. U.S. Nuclear Regulatory Commission. NUREG-1556, Volume 9, Revision 3: Consolidated Guidance About Materials Licenses — Program-Specific Guidance About Medical Use Licenses. nrc.gov
7. U.S. Nuclear Regulatory Commission. NRC Form 313: Application for Materials License. nrc.gov
8. U.S. Nuclear Regulatory Commission. Frequently Asked Questions About Licensing Medical Uses of Byproduct Material Under Revised 10 CFR Part 35 (Medical Use Toolkit). nrc.gov
9. International Commission on Radiological Protection. ICRP Publication 107: Nuclear Decay Data for Dosimetric Calculations (I-131 half-life). Annals of the ICRP. 2008;38(3). icrp.org