Decommissioning a Radioactive Materials License

Introduction

Closing a radioactive-materials program and terminating an NRC or Agreement State license is a defined, dose-based process: the licensee decommissions the use area, demonstrates through a final status survey that residual radioactivity meets the radiological criteria for license termination, and documents compliance using derived concentration guideline levels and detection-capable instrumentation. ¹⁷¹⁰ It is not simply locking the door and mailing back a license; it is a regulated end-of-life process with specific dose criteria, survey methodology, and timeliness requirements.

For a medical or nuclear-medicine facility, decommissioning arises when a service line ends, a clinic closes or relocates, a hot lab is retired, or a sealed-source device reaches end of life. In each case the licensee must show that what remains behind is below a dose-based release limit, and must do so with a survey defensible enough to satisfy the regulator before the license — and the obligations that come with it — can end. ⁵⁷

This guide explains the radiological criteria for license termination, the MARSSIM final status survey framework, how derived concentration guideline levels translate a dose limit into a measurable concentration, the minimum-detectable-activity mathematics that determine whether an instrument is adequate, the decommissioning-timeliness rules, and the practical steps. DRPS supports licensees with this work as part of its radioactive material license support and radiation safety officer services across Florida, Maryland, Virginia, Washington DC, California, and Nevada.

Topic Explanation

What is decommissioning and license termination?

Decommissioning is the process of removing a facility or use area from service so that the license can be terminated, and license termination is the regulator's formal acceptance that residual radioactivity meets the release criteria. ⁷¹⁵ The two are linked: a license is not terminated until decommissioning is complete and the supporting survey is accepted.

The end-state most medical licensees seek is unrestricted release — the site can be released for any use with no further radiological controls. The alternative, restricted release, allows termination with legally enforceable institutional controls and is rarely the right path for a routine medical program. ¹²

For facilities planning an exit, decommissioning should be coordinated with the broader license and radiation-safety program, including radioactive material license support, radiation safety officer duties, and medical physics consulting. NRC NUREG-1757 provides the consolidated decommissioning guidance specifically for materials licensees, and MARSSIM provides the survey methodology. ⁷⁸¹⁰ A practical decommissioning plan answers a few recurring questions:

What licensed material, sealed sources, and contamination history exist in each area?
Which areas have potential for residual radioactivity, and which do not?
What are the radionuclides, and what are their derived concentration guideline levels?
Do the available instruments have enough detection capability to measure against those levels?
What survey design and statistical test will demonstrate compliance?
What timeliness and documentation obligations apply?

The radiological criteria for license termination

The release criteria live in 10 CFR Part 20, Subpart E. The key provisions are summarized below. ¹²³⁴

Release path	Dose criterion	Key conditions
Unrestricted use (10 CFR 20.1402)	TEDE ≤ 25 mrem/yr (0.25 mSv/yr) to the average member of the critical group	Residual radioactivity also reduced to ALARA ¹
Restricted use (10 CFR 20.1403)	TEDE ≤ 25 mrem/yr while controls are in effect; ≤ 100 mrem/yr if controls fail (up to 500 mrem/yr only under added conditions)	Legally enforceable institutional controls, financial assurance, periodic rechecks ²
Alternate criteria (10 CFR 20.1404)	Case-specific, with added Commission findings	Used rarely; requires demonstration and review ³

For nearly all medical decommissioning, the target is the unrestricted-use criterion: 25 mrem/yr TEDE plus ALARA. ¹ The dual requirement matters — meeting 25 mrem/yr is necessary but not sufficient; the licensee must also show residual radioactivity was reduced as low as reasonably achievable.

Key Technical Principles

From dose criterion to DCGL

The release criterion is a dose, but a survey measures a concentration. The bridge is the derived concentration guideline level (DCGL) — the radionuclide-specific residual concentration (per unit area for surface contamination, or per unit volume) that corresponds to the dose criterion under a defined exposure scenario. ⁸¹⁶

Two DCGL forms are used in MARSSIM: ¹⁰¹⁶

DCGL-W — the area-averaged guideline, compared against the survey data using a nonparametric statistical test (Sign test or Wilcoxon Rank Sum test).
DCGL-EMC — the elevated-measurement-comparison guideline for small areas of higher concentration, computed as the DCGL-W multiplied by an area factor:

DCGL_{EMC} = DCGL_{W} \times A_{m}

where $A_{m}$ is the area factor accounting for the smaller area over which an elevated reading is averaged. Survey results are judged against both: the average must satisfy the DCGL-W, and no hot spot may exceed its DCGL-EMC. ¹⁰

Classifying areas

MARSSIM organizes the survey by classifying each area by its potential for residual radioactivity, which sets how intensively it must be surveyed: ¹⁰

Class 1 — areas with the highest potential for contamination above the DCGL (for example, a hot lab bench or a sealed-source storage location); surveyed most intensively.
Class 2 — areas with potential for contamination but not expected to exceed the DCGL.
Class 3 — areas with low potential for any residual contamination.
Non-impacted — areas with no reasonable potential for residual radioactivity; not part of the final status survey.

Correct classification is foundational: under-classifying a contaminated area produces a survey too sparse to be defensible, while over-classifying everything wastes resources. ¹⁰

Minimum detectable activity

A survey is only credible if the instrument can actually detect activity at a fraction of the DCGL. The minimum detectable activity (MDA) is derived from Currie's detection-limit formulation. For paired counting with a well-known background, the detectable net count level is: ¹²¹³¹⁴

L_{D} = 2.71 + 4.65 B

where $B$ is the number of background counts accumulated in the counting interval. Converting the detectable counts to activity gives the MDA:

MDA = \frac{2.71 + 4.65 B}{ε \cdot t}

where $ε$ is the detection efficiency (counts per disintegration, including geometry and any yield/branching factors) and $t$ is the count time; additional divisors apply for sample mass or area, self-absorption, and chemical recovery as relevant. ¹²¹⁴

As a worked example, suppose a contamination measurement has a background of $B = 100$ counts over the count interval, a detection efficiency of $ε = 0.15$ counts per disintegration, and a count time of $t = 1$ minute:

L_{D} = 2.71 + 4.65 100 = 2.71 + 46.5 = 49.2 counts

MDA = \frac{49.2}{0.15 \times 1 min} \approx 328 dpm

To be a defensible final-status-survey instrument, this MDA must sit well below the DCGL — a common design target is for the MDA to be no more than about 10–50% of the DCGL so that residual activity at the release limit is reliably detected. ¹⁰ If the MDA is too high relative to the DCGL, the instrument, count time, or method must change before the survey is run.

The statistical demonstration

Final status survey data are not judged by eye. MARSSIM applies a nonparametric statistical test — the Sign test (when the radionuclide is absent from background) or the Wilcoxon Rank Sum test (when it is present in background) — to the measurements in each survey unit, demonstrating with defined confidence that the residual radioactivity is below the DCGL. ¹⁰ The number of measurements is set in advance from the expected variability and the desired decision-error rates, which is why survey design precedes data collection rather than the reverse.

Clinical Impact

Decommissioning is the moment a facility's entire compliance history is tested. Years of contamination control, survey records, sealed-source accounting, and waste management either support a clean release or surface as problems when the final survey is run. A program that surveyed and documented well throughout its life decommissions efficiently; one that did not may face remediation, repeat surveys, and delay. ⁷¹⁰

The practical stakes are real. Until the license is terminated, the licensee continues to carry the obligations and costs of licensure — fees, RSO duties, surveys, security, and recordkeeping. A decommissioning that drifts because of poor planning or inadequate survey capability extends those obligations and can complicate a lease exit, a property sale, or a facility renovation. Conversely, a well-run decommissioning ends the liability cleanly. ⁵⁶

Decommissioning also intersects with sealed sources and waste. Retired gauges, brachytherapy sources, and check sources must be transferred to an authorized recipient or disposed of properly, and any contaminated material enters the waste stream with its own requirements. For those adjacent topics, see our guides to sealed-source leak testing and radioactive waste management in nuclear medicine, and for the survey instruments involved, choosing the right radiation survey meter.

Practical Optimization Tips

A defensible decommissioning is built from disciplined planning and survey design.

Plan before you survey

Assemble the history first: licensed radionuclides, sealed sources, spill records, and the locations where material was used or stored. ⁷
Classify areas (Class 1/2/3 or non-impacted) from that history before designing the survey. ¹⁰
Derive the DCGLs for the radionuclides and exposure scenario, and confirm instrument MDAs are well below them before fieldwork. ⁸¹⁰
Transfer or dispose of all licensed material and sealed sources to authorized recipients, and document the chain.

Run a survey that will hold up

Design the survey — measurement locations, count times, and the statistical test — in advance, sized to the decision-error rates. ¹⁰
Use instruments with documented efficiency and MDA appropriate to each radionuclide and surface type. ¹²
Investigate and remediate elevated readings against the DCGL-EMC, not just the average. ¹⁰
Keep ALARA in view: meeting 25 mrem/yr is not enough if reasonable further reduction was achievable. ¹

Common pitfalls to avoid

Under-classifying impacted areas. A Class 1 area surveyed as Class 3 produces an indefensible result. ¹⁰
Inadequate detection capability. An MDA near or above the DCGL cannot demonstrate compliance. ¹²
Forgetting ALARA. The unrestricted-release criterion is 25 mrem/yr and ALARA, not either alone. ¹
Missing timeliness obligations. The 10 CFR 30.36 notification and completion timeframes are specific and enforceable. ⁵
Skipping the statistical design. Collecting data without a pre-specified test and sample size undermines the demonstration. ¹⁰
Poor lifetime recordkeeping. Decommissioning exposes gaps in years of survey and source records.

Regulatory Considerations

Decommissioning and license termination are governed by 10 CFR Part 20 Subpart E for the dose criteria and 10 CFR 30.36 for the timeliness obligations, with NUREG-1757 and MARSSIM providing the implementing guidance. ¹⁵⁷¹⁰ The analysis and survey should be documented so they are defensible during regulator review.

Key frameworks to reference:

10 CFR Part 20, Subpart E — radiological criteria for license termination, including the unrestricted-use criterion (20.1402), restricted-use criteria (20.1403), and alternate criteria (20.1404). ¹²³⁴
10 CFR 30.36 — decommissioning-timeliness rule for byproduct-material licensees: the notification and completion timeframes triggered by ceasing principal activities or 24 months of inactivity. ⁵
NRC NUREG-1757 — consolidated decommissioning guidance for materials licensees, including the decommissioning process (Volume 1), characterization and final-status-survey/DCGL guidance (Volume 2), and financial assurance and timeliness (Volume 3). ⁷⁸⁹
MARSSIM (NUREG-1575) — the multi-agency final status survey methodology: area classification, DCGLs, survey design, and statistical tests. ¹⁰
EPA MARLAP — guidance on detection and quantification capability (the MDA framework) underlying defensible survey instrumentation. ¹¹

Agreement States administer their own equivalent license-termination programs. Of the states DRPS serves, Florida, Maryland, Virginia, California, Nevada, Pennsylvania, New York, and New Jersey are NRC Agreement States that license and oversee decommissioning of medical materials use under their own radiation-control rules, while Washington, DC and Delaware are regulated directly by the NRC for radioactive material. A licensee must confirm which authority holds its license and apply that authority's decommissioning and release requirements. For the licensing context, see our NRC radioactive material license guide and preparing for an NRC inspection.

Frequently Asked Questions (FAQs)

What does it mean to decommission a radioactive materials license?

Decommissioning is the process of safely removing a facility or use area from service so that the radioactive materials license can be terminated. It includes removing or transferring licensed material, surveying for residual radioactivity, remediating where needed, demonstrating through a final status survey that residual radioactivity meets the radiological criteria for license termination, and submitting the documentation the regulator requires to terminate the license.

What is the dose criterion for unrestricted release?

Under 10 CFR 20.1402, a site is acceptable for unrestricted use when the residual radioactivity that is distinguishable from background would result in a total effective dose equivalent to an average member of the critical group not exceeding 25 millirem (0.25 millisievert) per year, and the residual radioactivity has also been reduced to levels that are as low as reasonably achievable (ALARA).

What is a final status survey?

A final status survey (FSS) is the radiation survey that demonstrates a site or area meets the release criteria. The Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) provides the standard methodology: classifying areas by contamination potential, deriving concentration guideline levels from the dose criterion, choosing sampling and measurement methods with adequate detection capability, and applying statistical tests to the data to demonstrate compliance.

What is a derived concentration guideline level (DCGL)?

A DCGL is the radionuclide-specific residual-radioactivity concentration that corresponds to the regulatory dose criterion. The area-averaged DCGL (DCGL-W) is compared against the survey data using a statistical test, while the elevated-measurement DCGL (DCGL-EMC) addresses small areas of higher concentration. The DCGL translates an abstract dose limit into a concentration a survey instrument can actually measure against.

How quickly must decommissioning begin after a program ends?

Under the decommissioning-timeliness provisions of 10 CFR 30.36, when a licensee decides to permanently cease principal activities, or when no principal activities have been conducted for 24 months, the licensee must generally notify the NRC in writing within 60 days and either begin decommissioning or submit a decommissioning plan, with decommissioning to be completed within 24 months unless an alternate schedule is approved.

Who should perform the final status survey?

The final status survey should be designed and performed or overseen by qualified radiation-safety and health-physics professionals using instruments with documented detection capability suited to the radionuclides and DCGLs involved. DRPS supports licensees with decommissioning planning, survey design, instrument selection, and license-termination documentation.

Key Takeaways

License termination is dose-based. Unrestricted release requires residual radioactivity below 25 mrem/yr TEDE to the average member of the critical group, and reduced to ALARA. ¹
MARSSIM is the survey framework. Area classification, DCGLs, survey design, and statistical tests turn the dose criterion into a defensible demonstration. ¹⁰
DCGLs bridge dose and measurement. The DCGL-W governs the average and the DCGL-EMC governs hot spots. ¹⁰¹⁶
Detection capability is decisive. The instrument MDA must sit well below the DCGL, a result that falls out of the Currie detection-limit mathematics. ¹²
Timeliness is enforceable. 10 CFR 30.36 sets specific notification and completion timeframes once a program ends. ⁵
Lifetime recordkeeping pays off at the end. Good survey and source records make decommissioning efficient; gaps create remediation and delay. ⁷

Conclusion

Decommissioning a radioactive-materials license is a structured, dose-based process: remove the material, classify the areas, derive the concentration guidelines from the 25 mrem/yr criterion, confirm the instruments can detect well below those guidelines, run a statistically designed final status survey, and document the demonstration. Each step is concrete, and each depends on the one before it.

A facility that treats decommissioning as a planned end-of-life project — built on good lifetime records, correct area classification, adequate detection capability, and a defensible statistical survey — terminates its license cleanly and ends the associated obligations. One that improvises faces remediation, repeat surveys, and continued liability. The difference is planning and survey rigor, not luck.

How DRPS Can Help

Diagnostic Radiation Physics Services helps materials licensees plan and execute decommissioning and license termination. This includes decommissioning planning, historical-site-assessment and area classification, DCGL derivation, survey design and instrument-MDA evaluation, final status survey support, and license-termination documentation, coordinated with the facility's radioactive material license support, radiation safety officer, and medical physics consulting programs.

DRPS supports facilities across our service locations, including Florida, Maryland, Virginia, Washington DC, California, Nevada, New York, Pennsylvania, New Jersey, and Delaware.

A strong decommissioning is not just about ending a license. It is about ending it cleanly, defensibly, and on schedule, so the facility can move on without a lingering radiological liability.

Related Resources

References

U.S. Nuclear Regulatory Commission. 10 CFR 20.1402: Radiological criteria for unrestricted use. ecfr.gov
U.S. Nuclear Regulatory Commission. 10 CFR 20.1403: Criteria for license termination under restricted conditions. ecfr.gov
U.S. Nuclear Regulatory Commission. 10 CFR 20.1404: Alternate criteria for license termination. ecfr.gov
U.S. Nuclear Regulatory Commission. 10 CFR Part 20, Subpart E: Radiological Criteria for License Termination. ecfr.gov
U.S. Nuclear Regulatory Commission. 10 CFR 30.36: Expiration and termination of licenses and decommissioning of sites and separate buildings or outdoor areas. ecfr.gov
U.S. Nuclear Regulatory Commission. Regulatory Issue Summary 2015-19, Revision 1: Decommissioning Timeliness. nrc.gov
U.S. Nuclear Regulatory Commission. NUREG-1757, Volume 1, Revision 2: Consolidated Decommissioning Guidance — Decommissioning Process for Materials Licensees. nrc.gov
U.S. Nuclear Regulatory Commission. NUREG-1757, Volume 2, Revision 2: Consolidated Decommissioning Guidance — Characterization, Survey, and Determination of Radiological Criteria. nrc.gov
U.S. Nuclear Regulatory Commission. NUREG-1757, Volume 3, Revision 1: Consolidated Decommissioning Guidance — Financial Assurance, Recordkeeping, and Timeliness. nrc.gov
U.S. Nuclear Regulatory Commission, EPA, DOE, DoD. Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM), NUREG-1575, Revision 1. 2000. nrc.gov
U.S. Environmental Protection Agency. Multi-Agency Radiological Laboratory Analytical Protocols Manual (MARLAP), Chapter 20: Detection and Quantification Capabilities. EPA 402-B-04-001C. epa.gov
U.S. Nuclear Regulatory Commission. NUREG/CR-4007: Lower Limit of Detection — Definition and Elaboration of a Proposed Position for Radiological Effluent and Environmental Measurements (Currie LA). nrc.gov
Currie LA. Limits for qualitative detection and quantitative determination: application to radiochemistry. Anal Chem. 1968;40(3):586-593. doi:10.1021/ac60259a007. nist.gov
U.S. Nuclear Regulatory Commission. Decommissioning of Nuclear Facilities — Process Overview. nrc.gov