ML26063A826

2025 Annual Operating Report for the Armed Forces Radiobiology Research Institute (Afrri), License No. R-84, Docket 50-170

ML26063A826
Person / Time
Site:	Armed Forces Radiobiology Research Institute (R-084)
Issue date:	03/04/2026
From:	Burke G Uniformed Services Univ. of the Health Sciences
To:	Cindy Montgomery Office of Nuclear Reactor Regulation, Document Control Desk
References
Download: ML26063A826 (0)

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UNIFORMED SERVICES UNIVERSITY OF THE HEALTH SCIENCES ARMED FORCES RADIOBIOLOGY RESEARCH INSTITUTE 4555 S PALMER RD.

BETHESDA, MD 20814 (301)-295-1210 https://afrri.usuhs.edu Learning to Care for Those in Harms Way March 04, 2026 Cindy K. Montgomery Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, MD 20852 Attention: Document Control Desk

Dear Ms. Montgomery,

Enclosed is the 2025 Annual Operating Report for the Armed Forces Radiobiology Research Institute (AFRRI), License No. R-84, Docket 50-170.

This report describes the technical specifications for operation of the TRIGA Mark-F reactor housed at AFRRI. Topics include definitions, safety limits and limiting safety system settings, limiting conditions for operations, surveillance requirements, design features, and administrative controls.

For further information please contact Mr. Andrew Smolinski, Chief, Radiation Sources, Radiation Sciences Department, AFRRI via andrew.smolinski@usuhs.edu or (301)-295-1288.

Gerald F. Burke CAPT, MSC, USN Institute Director, AFRRI

Enclosure:

As Stated BURKE.GERALD.F RANCIS.1027949 327 Digitally signed by BURKE.GERALD.FRANCIS.1027 949327 Date: 2026.03.04 13:18:28

-05'00'

Annual Operating Report - 2025 TRIGA Mark-F To satisfy the requirements of:

U.S. Nuclear Regulatory Commission License No. R-84, Docket No. 50-170 Technical Specification 6.6.a.

Prepared by:

Mr. Andrew Smolinski Reactor Facility Director, AFRRI Submitted by:

Gerald F. Burke CAPT, MSC, USN Institute Director, AFRRI

AFRRI 2025 Annual Report Page 2 of 17 Table of Contents

1. Introduction

2. General Information

a. Key reactor personnel and staffing changes

b. Reactor and Radiation Facilities Safety Subcommittee (RRFSS) composition

3. Facility Operations Summary (T.S.6.6.a.1)

a. Facility Design Changes (1) License Amendment Request (2) Facility Modifications

b. Performance Characteristics

c. Operational and Administrative Procedures

d. Results of Surveillance Tests and Inspections

4. Core Burnup - Characteristics (T.S.6.6.a.2)

a. Energy Generated by the Reactor Core

b. Number of Pulses $2.00 or Larger

5. Unscheduled Shutdowns (T.S.6.6.a.3)

a. Unscheduled Shutdowns

b. Related Corrective Actions to Ensure Safe Operations

6. Safety-Significant Maintenance (T.S.6.6.a.4)

a. Corrective Maintenance

b. Preventive Maintenance

7. Changes affecting the Safety Analysis Report (SAR) (T.S.6.6.a.5 and T.S.6.6.a.6)

(Made pursuant to 10 CFR 50.59 and summaries of 50.59 Safety Evaluations

a. Changes that affect the description in the SAR

b. Procedure changes that affect the description in the SAR

c. New experiments or tests not encompassed in the SAR

8. Radioactive Effluents (T.S.6.6.a.7)

a. Liquid Waste Summary

b. Gaseous Waste Summary

c. Solid Waste Summary

9. Environmental Radiological Surveys (T.S.6.6.a.8)

10. Exposures Greater Than 25% of 10 CFR 20 Limits (T.S.6.6.a.9)

11. Conclusion

AFRRI 2025 Annual Report Page 3 of 17

1. Introduction The TRIGA Mark-F reactor at AFRRI was available for normal operations for the duration of 2025. Two additional operating licenses were received, and one was removed: there are a total of six SRO-licensed staff members currently at AFRRI. All surveillance and maintenance activities were completed and within periodicity, and the pace of routine experiments exceeded 2024.

There were three reactor modifications approved under 50.59 during the year and no License Amendment Requests (LAR) submitted. There were four unscheduled shutdowns during 2025, all due to known causes. All safety systems performed as designed.

The 2025 annual audit required by the reactor technical specifications was conducted from 07 JAN 2026 to 08 JAN 2026, led by Ms. Michelle Dudley from the National Institute of Standards and Technology (NIST) Center for Neutron Research Reactor (NCNR). The audit report indicated no technical specification violations and no major discrepancies in reactor operations, maintenance, or documentation. The audit identified some minor documentation findings, highlighted known degradations in facility equipment that are being worked through by facility staff, and provided suggested changes and improvements. The biennial physical security plan (PSP) external audit was conducted by CPT David Manzenares from the 20th CBRNE Command (Chemical, Biological, Radiological, Nuclear, Explosives) from 30 APR 2025 to 02 MAY 2025. His review used the NRC inspection procedures as guidance to assess implementation of the PSP and special nuclear material control and accounting (MC&A). The audit identified some minor documentation findings that are being worked through by facility staff and provided suggested training and record improvements. Details of the audits are provided in Section 3.d.

An NRC inspection of reactor facility operations was conducted by Mr. Necota Staples from 29 JUL 2025 to 31 JUL 2025, which included observation of reactor operations. The inspection resulted in one Notice of Violation (NOV) - Severity Level IV related to the overpower event in May 2025, which was self-reported as Event Notification 57730. Details of EN 57730 are provided in Section 5.

There was one change to the Reactor and Radiation Facilities Safety Subcommittee (RRFSS), replacement of a recently retired external member.

The remainder of this report is written in the format designated in the Technical Specifications for the TRIGA Mark-F reactor at AFRRI. Items not specifically required are presented in the General Information section. The following sections correspond to the required items listed in Section 6.6.a. of the Technical Specifications.

AFRRI 2025 Annual Report Page 4 of 17

2. General Information

a. Key AFRRI personnel (as of 31 DEC 2025)

AFRRI Institute Director - CAPT Gerald Burke, USN AFRRI Deputy Director - Col Susan Whiteway, USAF AFRRI Chief of Staff - LTC Karen Thomas, USA Radiation Sciences Department (RSD) Head - Andrew Cook (SRO)

Radiation Safety Officer (RSO) - MAJ Jacob Vincent, USA Reactor Facility Director (RFD) - Andrew Smolinski (SRO)

Reactor operations personnel:

Reactor Operations Supervisor (ROS) - Benjamin Knibbe (SRO)

Training Coordinator - Benjamin Knibbe (SRO)

Other reactor operators:

Addison Guynn (SRO)

Kyrone Riley (SRO)

SFC John Wilson, USA (SRO)

Operator candidates:

SFC Brandon Thomas, USA Newly licensed operators:

None Additions to reactor and support staff in 2024:

None Departures in 2025:

Mathieu Brener (SRO)

Catherine Benton, Assistant Radiation Safety Officer (ARSO)

MAJ Andrew Ng, USA (AFRRI Executive Officer)

MSG Liberio Miguelpablo, USA (Operator Trainee and Health Physics)

b. Key Reactor and Radiation Facilities Safety Subcommittee (RRFSS) updates for 2025 Dr. Steven Dewey, Health Physics Chief, NIST-NCNR - appointed 06 JUN 2025

AFRRI 2025 Annual Report Page 5 of 17 Per the requirements in Section 6.2.1.1 of Technical Specifications for the TRIGA Mark-F reactor at AFRRI, the RRFSS consisted of the following members as of 31 DEC 2025:

RSC Chair and Director's Representative - Col Susan Whiteway Radiation Safety Officer - MAJ Jacob Vincent Radiation Sciences Department (RSD) Head - Andrew Cook Reactor Facility Director (RFD) - Andrew Smolinski Health Physics Specialist (External) - Dr. Steven Dewey (NIST)

Reactor Operations Specialist (External) - Jere Jenkins (TAMU)

Reactor Operations Specialist (External) - Thomas Regan (UMLRR)

Approved Alternates:

AFRRI Chief of Staff - LTC Karen Thomas AFRRI Executive Officer - MAJ Michael Stewart Health Physics Technician - Timothy Tylka Reactor Operations Supervisor (ROS) - Benjamin Knibbe Two meetings were held in 2025:

27 JUN 2025 25 NOV 2025

3. Facility Operations Summary A summary of changes to the facility design, performance characteristics, administrative procedures, and operational procedures related to reactor safety, as well as the results of surveillance testing, are provided in this section.

a. Facility Design Changes (1) License Amendment Requests (LAR)

There was one License Amendment (27) directed by the NRC because of publication of new regulations pertaining to Non-Power and Utilization Facilities (NPUFs). License Amendment 27 did not modify the reactor technical specifications. The NPUF Rules were approved and issued in January 2025. Directed changes and a compliance order was issued on February 6 for AFRRI:

• Non-expiring licenses.

o There will be no more 20-year license renewals. License Amendment 27, directed by the NRC, removed the license expiration date. (ML25030A322 dated February 10, 2025)

• Periodic SAR Submittals.

o License renewal is to be replaced with an initial safety analysis report (SAR) submittal for NRC review and updates every 5 years thereafter.

AFRRIs initial submission is due January 8, 2027.

AFRRI 2025 Annual Report Page 6 of 17 AFRRIs response to the order was sent to the NRC on February 12, 2025, consenting to the order and acknowledging the following:

• AFRRI License, R-84, Docket 50-170, is effective as of the date of its issuance and has no fixed term.

• AFRRI shall file an initial updated Final Safety Analysis Report (FSAR) no later than January 8, 2027.

• The FSAR, as required by 10 CFR 50.71(e)(4)(ii), must reflect all changes made to the FSAR up to a maximum of 6 months prior to the date of filing.

• AFRRI shall file subsequent FSAR updates no more than 5 years from the date of the previous submittal.

There were no License Amendment Requests originating from the reactor facility submitted during 2025. However, one is in the process of being authored. A Phase 0 public meeting was held with NRC personnel on 14 FEB 2023 for a proposed LAR (now No. 28) for the AFRRI TRIGA Mark-F Operating License R-84. This LAR is still in draft awaiting submission. The LAR Phase 0 meeting included changes to the Technical Specifications related to:

• Updating the organization structure.

• Updating qualification requirements for Reactor Facility Manager and ROS to align with standard American National Standard (ANS) 15.4.

• Allowing the low source interlock to be linked to wide range logarithmic or multi-range linear nuclear instruments.

• Changing the required location of Stack Gas Monitor readouts to be local and in control room, rather than control room and reactor bay.

Since the Phase 0 public meeting with the NRC, other inconsistencies in the Technical Specifications and facility limitations have been identified by operators that have delayed the submittal. The Reactor and Radiation Facilities Safety Subcommittee (RRFSS) requested that a review be conducted on alignment between ANS 15.1 and the current tech specs, and that any gaps be identified for resolution prior to the submittal.

Additional changes identified so far during this review include:

• Inconsistencies in safety system interlock surveillance periodicities between Section 3.2.1 Table 3 and Section 4.2.2.b.

• Inconsistency with fuel temperature scram test and check surveillances between Section 4.2.2.b, Table 2, and T.S. 4.2.3.c.

• Inconsistency in Reactor Secured definition between the ANS 15.1 standard and the current definition (1.32).

• No definition for Initial Startup and Approach to Power.

Endurance testing following replacement of the secondary cooling heat exchanger revealed the current technical specification limit on excess reactivity ($5.00) is insufficient to allow continuous 24/7 operation above 600kW due to xenon-preclusion. This resulted in modification,

AFRRI 2025 Annual Report Page 7 of 17 and ultimately cancellation, of a proposed long-duration in-pool experiment. Extending this limit to at least $7.50 will be evaluated for inclusion in LAR 28.

Troubleshooting of technical problems with the nuclear instrument channel used for pulsing (NPP-1000) has led to a desire to remove it being used as a high-flux channel for steady-state operations. The problems are strictly related to pulsing, but moving the high flux trip functionality to the multi-range linear channel (NMP-1000) would allow greater flexibility for configuring or replacing the NPP-1000 for pulsing, without affecting steady-state operations.

Moving the steady-state high flux trip to the other channel will be evaluated for inclusion in LAR

28.

Changes stemming from these activities will be added to the request after approval by the RRFSS.

(2) Facility Modifications (FMs)

One facility modification and two facility software modifications (FSM) were completed in 2025 requiring 50.59 evaluations:

FSM-004: Upgrade Reactor Control System Console Software. This facility software modification upgraded operating systems for 64-bit compatibility, added human factors improvements based on operator feedback, and installed new computers & monitors (FM-035). FSM-004 was approved by the RRFSS on 05 JUN 25. Final installation and testing were completed 16 JUL 2025.

FSM-009: High Level Assembly (HLA) Patch. This facility software modification provided software patches to address an intermittent Memory Access Error on the User Interface Terminal (UIT) (the windows computer) of the reactor control system. The errors were a source of at least two system crashes and subsequent reactor scrams (Scrams 0028 and 0029). FSM-009 was approved by the RRFSS on 21 OCT 2025. Final installation and testing were completed 22 OCT 2025.

FM-036 Partial-Body Irradiation System (SHRC & PES). This facility modification created a 3-part shielding system for partial-exposure of biological experiments in exposure room 2 (ER-2). It created the short horizontal radiation cannon (SHRC), an in-tank portable horizontal beamline between the reactor core and tank protrusion, to be used adjacent to ER-1 or ER-2. It created movable shielding windows inside ER-2 around the tank protrusion to further cut down and shape the beamline output. And it created additional Partial Exposure Shields (PES) as a setup around an experiment array to reduce/tailor radiation to the region of interest. FM-036 was approved by the RRFSS on 28 JUL 2025.

Final installation and testing were completed 04 DEC 2025.

b. Performance Characteristics There were no changes to the performance characteristics of the core during 2025. All fuel

AFRRI 2025 Annual Report Page 8 of 17 elements and control rods remained in place for operations throughout the year until 05 DEC 2025, when the annual maintenance shutdown began. Inspections for in-core fuel elements, fuel followed control rods (FFCRs), and the transient control rod were completed. All fuel elements passed elongation and bow measurements, however visual inspection of three standard elements led to their designation as suspect. These were removed from service, and placed in long term storage. Previously used elements from long-term storage were inspected and found suitable as replacements for the degraded elements. Two fresh instrumented elements were added to the F-ring to begin their initial burn-in period, keeping the overall number of elements and the core configuration the same. Core excess reactivity overall was reduced by $0.14 cents due to the changes. No new degradations were found in FFCRs or the transient control rod. Rod calibrations, thermal power calibration, and power coefficient of reactivity surveillances performed from December 18 through December 31, 2025, confirmed that core performance agreed with previous operational data.

c. Operational and Administrative Procedures There were no procedures requiring 50.59 evaluation. There were several updates to the Operational Procedures during 2025. There were no new Administrative Procedures implemented in 2025. The changes do not adversely affect reactor operations or safety. The revised procedures were approved by the RFD and reviewed by the RRFSS:

001 Reactor Startup Checklist 102 Monthly Checklist (twice) 004 Scrams, Alarms, and Abnormal Conditions 103 Quarterly checklist 009 Exposure Room Entry 104 Semi-Annual Checklist 010 Conduct of Experiments 105 Annual Checklist 011 Exposure Room Dosimetry and Experiments 200 Fuel Movement and Inspection 203 Power Coefficient Measurements 201 Control Rods 220 Primary Water System 210 Calibration of NP-1000 221 Primary Water RTD Test and Calibration 211 Calibration of NPP-1000 230 Secondary Water System 212 Calibration of NLW-1000 240 Makeup Water System 213 Calibration of NMP-1000 260 Facility Interlock System Test 214 Calibration of NFT-1000 406 Emergency Pool Fill 215 Thermal Power Calibration

d. Results of Surveillance Tests and Inspections All maintenance and surveillance tasks during 2025 were accomplished as normally scheduled during the year, including those tasks involving the reactor fuel, instrumentation, control rod drives, and other related components. The annual maintenance and surveillance outage occurred during the month of December 2025. FFCR, control rod, and control rod drive mechanism inspections were completed with no degradations in control rods identified, and three suspect elements removed from service as previously mentioned.

AFRRI 2025 Annual Report Page 9 of 17 In 2025, there were four reactor malfunctions and 36 corrective maintenance items identified.

In 2024, there were nine reactor malfunctions and 50 corrective maintenance items, so facility condition trends are improving. Refer to sections 5 & 6 below.

Annual Technical Specification Audit - The 2025 annual reactor audit required by the reactor technical specifications included:

• Conformance of facility operation to the Technical Specifications (TS) and the license.

• Results of all actions taken to correct deficiencies occurring in facility equipment, structures, systems, or methods of operation that affect safety.

• Facility Emergency Plan and implementing procedures (biennial).

• Reactor Facility ALARA Program.

The audit report indicated no technical specification violations and no deficiencies that affect reactor safety. The requirements of the operating license were met in all areas reviewed. No major discrepancies in reactor operations, maintenance, or documentation. The AFRRI Tech Specs do not stipulate use of a consensus standard in the development of its Emergency Plan (EP). After consultation with the Reactor Facility Director, it was decided that the EP would be reviewed against the guidance outlined in the current standard (ANSI/ANS 15.16 2015, Emergency Planning for Research Reactors) as part of the audit and a detailed comparison was included as part of the audit.

The audit identified some minor documentation findings, highlighted known degradations in facility equipment that are being worked through by facility staff, and provided suggested changes and improvements. A summary of positive, negatives, and suggested corrective actions from the audit are summarized in the section below.

Annual Audit Summary Positives

• AFRRI is actively working self-identified improvements throughout all the areas reviewed.

• The facility tour demonstrated efficient well-organized deployment of constrained resources to maximize its mission capacity.

• The ability of the staff to substantially increase delivery of experiments exceeding historical performance levels without negative impacts on safety and regulatory compliance is commendable.

• A continuing arc of improvement over past audits was noted for issuing new procedures and implementing improvements through revisions of existing documents. AFRRIs program is achieving a high level of maturity.

• The new revisions of the checklist used for the 2025 fuel inspections include several key improvements and the facility should be commended. These enhancements promote greater consistency across the inspection process.

AFRRI 2025 Annual Report Page 10 of 17 Negatives

• Most of the staff are fulfilling the responsibilities of multiple roles, with hiring of current staff openings essentially frozen, and some key roles filled by military personnel scheduled to rotate out in the next two years. Staffing constraints are the highest risk to continued compliant and safe operations at current mission levels.

• A needed correction to the 2024 annual report was identified, a typo in the units reported in the table in Section 8.a. was found. Units in the table headers should be microcuries (Ci) for total activity, and microcuries per liter (Ci/L) for concentration.

Suggestions

• Consider reproducing and maintaining the historical basis for previously approved experiments covered by routine reactor authorizations in a fashion similar to Routine Reactor Authorization (RRA) 6 for use of the graphite cube and Special Reactor Authorization (SRA) 7 for partial-body, and consider incorporating a periodic review of experiment envelopes as the facility is upgraded.

• It was noted that the EP extensively points back to the Emergency Response Guidebook in lieu of stating the expectations within the EP itself, which the reviewer found cumbersome.

It is recommended AFRRI consider the following edits to support ease of use:

o Consolidate all content aligned with the ANSI/ANS-15-16-2015 guidance into the EP.

o Eliminate duplicate content between the two documents.

o Streamline the Guidebook to consist of procedures uniformly formatted.

• Create a policy or procedure that fully defines the ALARA program at the AFRRI reactor.

An excellent starting point is the Appendix E of ANSI 15.11(g).

Biennial Security Audit The biennial Physical Security Plan (PSP) external audit was conducted by CPT David Manzenares from the 20th CBRNE Command (Chemical, Biological, Radiological, Nuclear, Explosives) from 30 APR 2025 to 02 MAY 2025. His review used the NRC inspection procedures as guidance to assess implementation of the PSP and nuclear material control and accounting (MC&A). The audit identified some minor documentation findings that are being worked through by facility staff and provided suggested training and record improvements.

Specific training of security officers and base police regarding recently revised regulations on suspicious activity and drone activity was highlighted as a recommendation.

NRC Inspections A routine NRC inspection of reactor facility operations was conducted by Mr. Necota Staples from 29 JUL 2025 to 31 JUL 2025. The inspection resulted in one Notice of Violation (NOV) - Severity Level IV related to the overpower event in May 2025, which was self-reported as Event Notification 57730. Details of EN 57730 are provided in Section 5. The results of the inspection and NOV are documented in Armed Forces Radiobiology Research Institute - U.S.

Nuclear Regulatory Commission Safety Inspection Report No. 05000170/2025201 and Notice of Violation, dated 04 SEP 2025. [ML25239A039]

AFRRI 2025 Annual Report Page 11 of 17

4. Core Burnup Characteristics

a. Energy Generated by the Reactor Core:

Month Kilowatt-Hours Energy Summary January 2,282.7 Total energy generated in 2025: 63,023.2 kWh (2.626 MWd)

February 1,408.2 Total energy on fuel elements: 1,282,650.8 kWh (53.44 MWd)

March 14,104.9 Total energy on FFCRs: 550,043.1 kWh (22.92 MWd)

April 3,903.1 May 599.3 June 33,509.4 July 1,125.8 August 1,228.7 September 646.3 October 620.1 November 178.3 December 3,416.4 TOTAL 63,023.2

b. Pulse Summary:

Total pulses this year > $2.00: 0 Total pulses on fuel elements > $2.00: 4,219 Total pulses on FFCRs > $2.00: 107 Total pulses this year: 0 Total pulses on fuel elements: 12,201 Total pulses on FFCRs: 2,436

5. Unscheduled Shutdowns

a. There were 4 unscheduled shutdowns in 2025 (all safety systems performed as designed):

Scram #

Date Description 0026 07 Apr 2025 UIT Computer Watchdog Scram (similar to Scram 009) - Computer stall 0027 22 May 2025 Overpower scram during startup (EN 57730) 0028 11 Aug 2025 UIT Memory Access Error - watchdog scram 0029 14 Aug 2025 UIT Memory Access Error - watchdog scram

b. Related Corrective Actions One of the unscheduled shutdowns was a reportable event (Scram 0027), with the steady state operating limit of 1.1MW momentarily exceeded and resulted in a Notice of Violation (NOV) - Severity Level IV during the annual NRC inspection. The event was self-identified and reported (EN 57730). The high-power scram occurred during startup in steady-state mode under

AFRRI 2025 Annual Report Page 12 of 17 two (2) control rod automatic control. During power escalation, the Logarithmic Nuclear Instrument Channel (NLW) malfunctioned, failing to provide a period signal (rate of change of power) to the automatic control system. The apparent cause of the event was high frequency noise induced in the log channel detector input, causing the channel to fail to a fixed high frequency of constant amplitude. The flat signal produced a negligible period signal for input to the automatic control algorithm. With no significant period input, the automatic control algorithm produced an output that withdrew the two control rods continuously for 5-7 seconds.

This resulted in the reactor power level increasing rapidly, several orders of magnitude, until high flux safety channels 1 and 2 caused an automatic scram, releasing control rods to safely shut down the reactor. Due to the rate of power increase, reactor power momentarily exceeded the steady-state license limit of 1.1MW for approximately 100 msec. Peak power levels recorded by the digital chart recorders were 1.2MW. All reactor protection systems functioned as designed.

Neither the fuel temperature Safety Limit (1000 °C), nor the Limiting Safety System Setting (600 °C), were exceeded during the event. Maximum fuel temperature recorded was 36 °C. All radiation monitoring systems were operable during the event. No release of radioactive material was detected. No damage to the fuel occurred.

The event was reported to NRC Headquarters Operations Office at 1504 on 22 May 2025 (EN 57730).

Subsequent troubleshooting revealed that the source of the noise was related to signal grounding, cable jacket condition, and proximity of the detector and preamplifier to other power sources. Commitments made to the NRC included changing out the fission chamber cable (completed during the 2025 annual outage), the transit rod motor drive modification (FM-031 and FSM-005), evaluation and modification of software inputs to drive speeds (FSM-003), and investigating the building AC ground network and shared neutrals. Relocation of the preamplifier to the core dolly and replacement of the degraded cable (FM-042) has substantially improved the condition of the channel.

The user interface terminal (UIT) computer watchdog scram (0026) was a memory buffer error. All safety systems operated as designed upon receipt of the UIT watchdog signal. The system was restarted per manual guidance. A scram with similar indications has not reoccurred since replacement of the control computers and operating system upgrade to 64-bit compatibility (Facility Modification FM-035 and Facility Software Modification FSM-004)

The two UIT Memory Access Error malfunctions (Scrams 0028 and 0029) were caused by spurious shutdown of the UIT application on the control system computer. All safety systems operated as designed upon receipt of the UIT watchdog scram signal. The issue was traced back to a change in the underlying operating system which occurred somewhere between Windows XP and Windows 10 that occasionally caused a synchronization issue with subroutines in the high-level assembly (HLA) code when the operator entered data into fields on the UIT (e.g.,

demand power, pulse timer, scram timer). A facility software modification (FSM-009), a software patch to the reactor control system software that addressed the synchronization issue between the main HLA thread and subroutines, was performed. The patch involved creating an

AFRRI 2025 Annual Report Page 13 of 17 event marker in the applicable subroutine files to ensure they finish before memory is reused in the main thread, which was causing the error and subsequent scram. The error has not reoccurred during operation since installation of the patch.

6. Safety-Significant Maintenance

a. Corrective Maintenance (CM) - 36 corrective maintenance items, 13 safety-related:

Maintenance effecting safety systems for 2025 is outlined in the table below, grouped by systems. The condition of the secondary cooling system and the problems with pulsing nuclear instrumentation are the most impactful maintenance items for the facility research needs, however, these items are not preventing overall safe operation of the facility.

Maintenance Affecting Safety Systems CM Tracking#

Date Description Secondary Cooling 25-004 11 Mar 2025 Replaced heat exchanger (like for like). Endurance test successful.

Nuclear Instrumentation 25-008 12 Mar 2025 NPP Pulse Channel Testing - Troubleshooting NPP with vendor (GA)25-015 23 May 2025 NLW troubleshooting for noise (EN 57730)25-017 02 Jun 2025 (Ongoing) Building electrical system troubleshooting (EN 57730)25-020 29 Jun 2025 NPP Pulse Channel Testing 25-023 25 Aug 2025 NPP Pulse Channel Testing (GA beta-version)25-024 16 Sep 2025 NPP Pulse Channel Testing (timestamps)25-027 10 Oct 2025 NLW Digital card replacement 25-032 02 Dec 2025 NLW Cable and Detector Investigation 25-036 31 Dec 2025 NLW Crossover Adjustments Control Rod Drives25-009 12 Mar 2025 Transient rod drop timer (Found during FSM-004 testing)

HVAC 25-030 03 Nov 2025 Metasys failure affected bay supply flow and bay ventilation DPs - Manual control of supply damper to ensure proper differential pressure. Metasys configuration restored to normal, manual control of dampers restored.

Fuel 24-025 09 Dec 2025 Fuel inspection and core arrangement. Four elements removed from service during biennial inspection, one instrumented element due to failed thermocouples, three based on visual inspection. All were placed in long-term storage, replaced with two previously used elements from long-term storage which passed inspection and two new instrumented elements. Core configuration (# of elements and positions) remained the same.

The condition of the secondary cooling system is improving. The primary/secondary plate-type heat exchanger was replaced allowing continuous high-power operation. The cooling tower leaks and the three-way valve that controls flow to the fins has had multiple failures due to wear and corrosion. The cooling tower system is nearing end of life and is in need of replacement.

Design aspects of this project are being planned for 2026. There is still no filter in the secondary system, and the open cooling tower allows debris (e.g., leaves and dust) to be carried throughout

AFRRI 2025 Annual Report Page 14 of 17 the system. Filtration is being included in the cooling tower replacement project scope.

Nuclear instrumentation safety significant maintenance in 2025 included the pulsing channel (NPP-1000) and wide range logarithmic (NLW) channel. Multiple activities were related to the NPP pulse capture modifications to restore pulsing capability. The testing revealed multiple software problems in the NPP module as the root of the data capture and transfer problems.

These affect the pulsing functions only. General Atomics (GA) resolution of the problem will require software changes to the NPP firmware and reactor control system software, FSM-007 and FSM-008, respectively.

Maintenance on the wide range logarithmic channel (NLW), which is responsible for the period signal and interlocks, included troubleshooting for noise and replacement of the digital card. Electrical noise on the NLW from movement of the AC/DC transient rod drive motor and external AC sources produced high period spikes, triggering the fast period interlock, and complicating transient rod withdrawals during startup. The noise also was the cause of the overpower event during a startup in automatic control as described in Section 5. Subsequent troubleshooting revealed that the source of the noise was related to signal grounding, cable jacket condition, and proximity of the detector to preamplifier to other power sources. Relocation of the preamplifier to the core dolly and replacement of the degraded cable (FM-042) has substantially improved the condition of the channel.

One control rod drive maintenance item was identified during unrelated software modification testing (FSM-004). The transient rod down limit switch, used in the drop timer, had inverted logic in the software code. Troubleshooting revealed the bug was isolated to the drop timer subroutine, did not affect any other functionality, and would produce conservative (longer) drop time values. The bug fix was included in the scope of FSM-004 and retested prior to returning the system to service.

One maintenance item was performed on the reactor HVAC system. The Metasys control system, which controls the AFRRI complex-wide ventilation systems (excluding buildings 43 and 47), failed during a routine update by facilities engineering. The failure affected reactor bay differential pressure (DP). Manual control of inlet dampers was taken to restore DP to normal until the system was investigated and restored.

Four reactor core fuel elements were removed from service during the biennial fuel inspection. Since all its thermocouples failed, a C-ring instrumented element was removed and replaced with a newer F-ring instrumented element that had been in the core for initial burn-in since 2009. This restored the NFT-2 fuel temperature indication, which had been out of service since December 2024. Three standard elements were removed from service based on visual inspection, one C-ring, one E-ring, and one F-ring, all dating from 1964. The suspect elements passed length and bow measurements but had visual defects (bulges) that warranted taking them out of service and restricting future use. Elements from the C-ring and E-ring were replaced with previously used elements from long-term storage that passed inspection. The F-ring positions were replaced by new (unirradiated) instrumented elements from storage to begin their initial burn-in period. The overall core configuration (number of elements and positions) remained the same.

AFRRI 2025 Annual Report Page 15 of 17 The inventory of available spare elements to be used in the core is currently limited. Long-term storage consists of:

• 4 suspect standard elements that are restricted from use.

• 4 previously used standard elements, acquired in 1964.

• 5 previously used instrumented elements all with failed thermocouples but otherwise intact, dating from 1964 (2), 1968 (2), or 1978 (1), which could be used in the core if necessary.

Planning for additional fuel procurement has been initiated.

b. Preventative Maintenance All maintenance and surveillance tasks during 2025 were accomplished as normally scheduled during the year, including those tasks involving the reactor fuel, instrumentation, control rod drives, and other related components. The annual maintenance and surveillance outage was during the month of December. Fuel, FFCR, and control rod and drive inspections were completed with no degraded control rods identified, and four fuel elements removed from service as described above.

7. Changes affecting the Safety Analysis Report (SAR)

(Made Pursuant to 10 CFR 50.59 and Summaries of 50.59 Safety Evaluations)

a. Facility Changes that Affect the Description in the SAR There was one facility modification performed that required 50.59 evaluation that affects the description in the SAR:

FM-036 Partial-Body Irradiation System (SHRC & PES). This facility modification created a 3-part shielding system for partial-exposure of biological experiments in exposure room 2 (ER-2). It created the short horizontal radiation cannon (SHRC), an in-tank portable horizontal beamline between the reactor core and tank protrusion, to be used adjacent to ER-1 or ER-2. It included rail attachments to trigger the existing limit switches of the facility interlock system to control core positioning and prevent interaction with in-pool components. It created movable shielding windows inside ER-2 around the tank protrusion to further cut down and shape the beamline output. And it created additional Partial Exposure Shields (PES) as a setup around an experiment array to reduce/tailor radiation to the region of interest. While the SAR already described the use of portable beam tubes for experiments, a description of this systems features will be added to the SAR. FM-036 was approved by the RRFSS on 28 JUL 2025. Final installation and testing were completed 04 DEC 2025.

b. Procedure Changes that Affect the Description in the SAR Several reactor administrative and operating procedures were in 2025. No procedures changed screened into 50.59 evaluation or required changes to the SAR description.

AFRRI 2025 Annual Report Page 16 of 17

c. New Experiments or Tests Not Encompassed in the SAR The experiment program in 2025 exceeded its output from 2024. The 47 experiment campaigns performed at the reactor in 2025 is the highest rate of output since before 1995.

Forty-six of the 47 experiment campaigns were routine experiments covered under existing routine reactor authorizations (RRA) or reactor parameter authorizations, T.S. 6.4.b. and T.S.

6.4.c respectively. One new experiment campaign was performed during the reporting period that required a special reactor authorization (SRA) that was not encompassed under existing routine experiment authorizations. This SRA covered initial use of the Partial-Body Irradiation System (SHRC & PES). The facility modification, tracked as FM-036 created a 3-part shielding system for partial-exposure of biological experiments in Exposure Room 2 (ER-2). It created the Short Horizontal Radiation Cannon (SHRC), an in-tank portable horizontal beamline between the reactor core and tank protrusion, to be used adjacent to ER-1 or ER-2. It created moveable L-shaped shielding windows inside ER-2 around the tank protrusion to further cut down and shape the beamline output. And it created additional Partial Exposure Shields (PES) as a setup around an experiment array to reduce/tailor radiation to the region of interest. Simulation models predicted a 10:1 body to leg ratio for the collimated mixed field irradiation of mice, and the initial experiments of passive dosimetry for characterization showed good agreement with the model. FM-036 and associated SRA-7 was evaluated under 10 CFR 50.59 and approved by the RRFSS. The first irradiation began with SRA-7 on 12/29/2025 and continued through January 2026. Since the first experiment has been completed successfully, SRA-7 is being converted to an RRA and sent to the RRFSS for review and approval.

8. Radioactive Effluents

a. Liquid Waste Two radioactive liquid discharges from the Hot and Warm waste tanks of 27,308.6 and 22,460.7 gallons were performed on August 28 and December 12, 2025, respectively. The Health Physics Department (HPD) conducted gamma spectrum analysis on one-liter samples of the tanks prior to discharge. No radionuclides were detected that exceeded the 25% of the concentration limits outlined in 10 CFR § 30.70. Schedule A - Exempt Concentrations. All isotope concentrations were below state and federal regulatory limits.

The 2025 external audit identified a needed correction to the 2024 annual report. A typo in the units reported in the table in Section 8.a. was found. Units in the table headers should be microcuries (Ci) for total activity, and microcuries per liter (Ci/L) for concentration. The statement that all isotope concentrations were below state and federal regulatory limits is correct.

b. Gaseous Waste There were no particulate discharges in 2025. The total activity of Argon-41 discharged in 2025 was 8.439 curies. The estimated effluent concentration from the release of Argon-41 represents 2.20% of the constraint limit for unrestricted areas (10 CFR 20.1101(d) and Table 2, Appendix B, 10 CFR 20).

AFRRI 2025 Annual Report Page 17 of 17 Quarter Argon-41 JAN - MAR 2025 2.514 Ci APR - JUN 2025 1.932 Ci JUL - SEP 2025 0.898 Ci OCT - DEC 2025 3.095 Ci 2025 Total 8.439 Ci

c. Solid Waste All solid radioactive waste material is transferred to the AFRRI byproduct license; none was disposed of under the R-84 reactor license.

9. Environmental Radiological Surveys All environmental sampling of soil and vegetation yielded radionuclide levels within the background range. The radionuclides that were detected were those expected from natural background and from long-term fallout from nuclear weapons testing.

10. Exposures Greater Than 25% of 10 CFR 20 Limits There were no doses to reactor staff personnel greater than 25% of 10 CFR 20 occupational limits. No visitors were exposed to doses greater than public radiation dose limits.

11. Conclusion 2025 was an incredibly productive year for the TRIGA Mark-F reactor at AFRRI, despite the challenges of staff shortages. This can be attributed to highly skilled staff, effective maintenance, better equipment reliability, and process improvements. For the second straight year, experiments and facility utilization are proceeding at a pace exceeding pre-1995 levels.

Agencies across the federal government and private sector companies have recognized the AFRRI reactor as a critical asset for their radiobiology research, education, and materials testing needs. AFRRI is looking forward to further research, leadership, training, and education in 2026.