ML24094A048

Mit Nuclear Reactor Lab., Annual Report for 2023, Per Technical Specification 7.7.1

ML24094A048
Person / Time
Site:	MIT Nuclear Research Reactor
Issue date:	03/29/2024
From:	Foster J, Lau E, Warmsley F Massachusetts Institute of Technology (MIT)
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
Download: ML24094A048 (1)

Text

MIT NUCLEAR REACTOR LABORATORY AN MIT INTERDEPARTMENTAL CENTER Edward S. Lau Assistant Director Reactor Operations Mail Stop: NW12-122 138 Albany Street Cambridge, MA 02139 U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Attn.:

Document Control Desk Phone: 617 253-4211 Fax: 617 324-0042 Email: eslau@mit.edu March 29, 2024

Subject:

Annual Report, Docket No. 50-20, License R-37, Technical Specification 7.7.1 Forwarded herewith is the Annual Report for the MIT Research Reactor for the period from January 1, 2023, to December 31, 2023, in compliance with paragraph 7.7.1 of the Technical Specifications issued November 1, 2010, for Facility Operating License R-37.

EL/st Sincerely,

-3ffd#-

Frank Warmsley Interim Reactor Superintendent MIT Research Reactor Edward S. Lau, NE Assistant Director of Reactor Operations MIT Research Reactor John P. Foster Director of Reactor Operations MIT Research Reactor

Enclosure:

As stated cc:

USNRC - Senior Project Manager Research and Test Reactors Licensing Branch Division of Licensing Projects Office of Nuclear Reactor Regulation USNRC - Senior Reactor Inspector Research and Test Reactors Oversight Branch Division of Licensing Projects Office of Nuclear Reactor Regulation Ao2D N flfz

MIT RESEARCH REACTOR NUCLEAR REACTOR LABORATORY MASSACHUSETTS INSTITUTE OF TECHNOLOGY ANNUAL REPORT to United States Nuclear Regulatory Commission for the Period January 1, 2023 - December 31, 2023 by REACTOR STAFF

Table of Contents Section Introduction................................................................................................................... 1 A.

Summary of Operating Experience................................................................... 3

1.

General................................................................................................. 3

2.

Experiments and Utilization................................................................ 4

3.

Changes to Facility Design................................................................... 6

4.

Changes in Performance Characteristics............................................... 6

5.

Changes in Operating Procedures.......................................................... 7

6.

Surveillance Tests and Inspections....................................................... 8

7.

Status of Spent Fuel Shipment.............................................................. 8 B.

Reactor Operation............................................................................................ 9 C.

Shutdowns and Scrams................................................................................... 10 D.

Major Maintenance........................................................................................... 12 E.

Section 50.59 Changes, Tests, and Experiments.............................................. 17 F.

Environmental Surveys..................................................................................... 22 G.

Radiation Exposures and Surveys within the Facility....................................... 23 H.

Radioactive Effluents........................................................................................ 24 Table H-1 Table H-2 Table H-3 Argon-41 Stack Releases.......................................................... 25 Radioactive Solid Waste Shipments......................................... 26 Liquid Effluent Discharges........................................................ 27 I.

Summary of Use of Medical Facility for Human Therapy............................... 28

MIT RESEARCH REACTOR ANNUAL REPORT TO U.S. NUCLEAR REGULATORY COMMISSION FOR THE PERIOD JANUARY 1, 2023 - DECEMBER 31, 2023 INTRODUCTION This report has been prepared by the staff of the Massachusetts Institute of Technology Research Reactor for submission to the United States Nuclear Regulatory Commission, in compliance with the requirements of the Technical Specifications to Facility Operating License No. R-37 (Docket No. 50-20), Paragraph 7.7.1, which requires an annual report that summarizes licensed activities from the 1st of January to the 31st of December of each year.

The MIT Research Reactor (MITR), as originally constructed and designated as MITR-I, consisted of a core of MTR-type fuel, enriched in uranium-235, cooled and moderated by heavy water in a four-foot diameter core tank that was surrounded by a graphite reflector. After initial criticality on July 21, 1958, the first year was devoted to startup experiments, calibration, and a gradual rise to one megawatt, the initially licensed maximum power. Routine three-shift operation (Monday-Friday) commenced in July 1959. The authorized power level for MITR-I was increased to two megawatts in 1962 and to five megawatts (the design power level) in 1965.

Studies of an improved design were first undertaken in 1967. The concept which was finally adopted consisted of a more compact core, cooled by light water, and surrounded laterally and at the bottom by a heavy water reflector. It is under-moderated for the purpose of maximizing the peak of thermal neutrons in the heavy water at the ends of the beam port re-entrant thimbles and for enhancement of the neutron flux, particularly the fast component, at in-core irradiation facilities. The core is hexagonal in shape, 15 inches across, and utilizes fuel elements which are rhomboidal in cross section and which contain UAlx intermetallic fuel in the form of plates clad in aluminum and enriched to 93% in uranium-235. The improved design was designated MITR-II. However, it retained much of the original facility, e.g.,

graphite reflector, thermal shield, biological shield, secondary cooling systems, containment, etc.

After Construction Permit No. CPRR-118 was issued by the former U.S.

Atomic Energy Commission in April 1973, major components for the modified reactor were procured and the MITR-I completed its mission on May 24, 1974, having logged 250,445 megawatt-hours during nearly 16 years of operation.

2 The old core tank, associated piping, top shielding, control rods and drives, and some experimental facilities were disassembled, removed, and subsequently replaced with new equipment. After pre-operational tests were conducted on all systems, the U.S. Nuclear Regulatory Commission issued Amendment No. lOto Facility Operating License No. R-37 on July 23, 1975. After initial criticality for MITR-II on August 14, 1975, and several months of startup testing, power was raised to 2.5 MW in December 1975.

Routine 5-MW operation was achieved in December 1976.

Three shift operation, Monday through Friday, was continued through 1995 when a gradual transition to continuous operation (24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> per day, 7 days per week with a shutdown for maintenance every 4-5 weeks) was initiated.

In December 2000, a fission converter medical facility was commissioned.

This facility generated the highest quality epithermal beam in the world for use in the treatment of certain types of cancer, and could again be made available.

-From mid-April through *mid-'September 2010, all major piping *in the--primary and secondary coolant systems was replaced and upgraded. This included a titanium heat exchanger (replacing the three previous primary heat exchangers) and the major instrumentation sensors that monitor system flows, temperatures, and pressures.

On November 1, 2010, NRC approved the relicensing of the reactor for 6-MW operation* through November 1, 2030~

Reactor power was increased in small increments from 5 MW for observations and data collection, and reached 5.8 MW on April 23, 2011. Routine 5.8 MW operation began on May 25, 2011.

On December 4, 2019, NRC approved the licensing of a new digital nuclear safety system.

After an NRC-approved postponement due to the nationwide COVID-19 public health emergency, implementation was completed in September 2020. The reactor was returned to full power on September 16, 2020, with the new system in service.

The current operating mode is normally continuous operation just under 6 MW when needed, with a maintenance shutdown scheduled every calendar quarter.

This is the forty-ninth annual report required by the Technical:' Specifications, and it covers the period from January 1, 2023, through December 31, 2023.

Previous reports, along with the "MITR-II Startup Report" (Report No. MITNE-198, February 14, 1977) have covered the startup testing period and the transition to routine reactor operation.

This report covers the forty-seventh full year of safe reactor operation and maintenance activities.

A summary of operating experience and other activities and related statistical data are provided in Sections A through I of this report.

A.

1.

3

SUMMARY

OF OPERATING EXPERIENCE General The MIT Research Reactor, MITR-11, is operated at the MIT Nuclear Reactor Laboratory (NRL) to facilitate* experiments and research including in-core irradiations and experiments, neutron activation analyses, and materials science and engineering studies such as neutron imaging. It is also used for student laboratory exercises and student operator training, and education and outreach programs. Additionally, the reactor has been used for industrial production applications and other irradiation services. When operating, the reactor is normally maintained at slightly below 6 MW.

For CY2023, the reactor was in an extended maintenance outage to identify and repair a primary system leak discovered in mid-December of 2022 (UOR 2022-2). The reactor was not made critical for CY2023.

Throughout CY2023, the reactor did not operate, compared to 77 operating hours per week for CY2022, 102 hours0.00118 days <br />0.0283 hours <br />1.686508e-4 weeks <br />3.8811e-5 months <br /> per week for CY2021, 60 hours6.944444e-4 days <br />0.0167 hours <br />9.920635e-5 weeks <br />2.283e-5 months <br /> per week for CY2020, 110 hours0.00127 days <br />0.0306 hours <br />1.818783e-4 weeks <br />4.1855e-5 months <br /> per week for CY2019, and 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per week for CY2018. The lower average for CY2020 was the result of extended shutdowns for the nationwide COVID-19 public health emergency, and for installation of the new digital nuclear safety system in the control room.

As part of maintenance activities to repair the primary system leak and minimize staff dose exposure, the reactor core tank was completely defueled over the course of IO fuel-movement evolutions between January 11 and January 31, 2023.

The fuel was then returned to the core tank in 6 fuel-movement evolutions between September 20 and September 28, 2023. While the core was empty of fuel, a screen was placed over the core flow guide to prevent any foreign objects from falling into the lower grid plate. No refuelings were performed in CY2023 for the purpose of compensating for burnup reactivity. No new fuel was introduced into the reactor core during CY2023.

One fuel element was discharged after it was inadvertently disengaged from the fuel handling tool during a defueling evolution (UOR 2023-1 ). A replacement fuel element that had been discharged during the previous operating cycle was returned to the same core position.

The MITR-11 fuel management program remains quite successful. During the period of CY2023, two shipments totaling 16 spent elements were returned to an off-site DOE facility.

As in previous years, the reactor did not operate with any fixed hafnium absorbers.

4

2.

Experiments and Utilization Due to the year-long maintenance outage, no irradiations were conducted using the MITR-11 throughout CY2023. However, the facility was still used for experiment preparation, post-irradiation examination, and in support of training and education programs. Experiment work conducted in CY2023 includes:

a) Post irradiation examination of the SFX inert-gas irradiation was completed.

This is a project sponsored by NSUF and led by PI Joshua Daw at INL that completed two cycles of irradiation in MITR in CY2022. This project is investigating the use of sapphire optical fibers for distributed temperature measurements. The irradiation included fibers previously irradiated at KSU with Li-6 coatings as well as commercial silica fibers for control.

The irradiation vehicle was placed into the NRL's main hot cells and the fibers were extracted for later analysis.

b) The extraction and testing of fibers and samples irradiated in the NSUF-sponsored HPR project were conducted. This project, led by PI Zilong Hua at INL, is studying the deployment of optical-fiber assisted photo-thermometry sensors in reactor environments. The HPR experiment consists of seven gold-coated silica optical fibers -

three interrogation/sensing pairs and one continuous loop for control/transmission-loss monitoring. The vehicle was disassembled in the main NRL hot cells, and then the fiber pairs were removed from their guide tubes. Optical transmission testing was performed on the fibers, and the photo-thermometry targets were also extracted for thermal diffusivity and thermo-gravimetric testing.

c) The neutron diffractometer / neutron imaging beamline is operational. An ongoing project funded by the DOE in 2021 utilizes this beamline to demonstrate a novel polychromatic diffractometer. This project involved MIT UROP students. In parallel, we prepared and submitted a proposal for a simultaneous neutron/X-ray imaging facility to be built at this beamline.

d) The MIT graphite exponential pile (MGEP) was re-started several years ago by Professor Kord Smith with the support of NRL staff and other MIT Nuclear Science

& Engineering (NSE) faculty members.

It has since been used for teaching and research.

A DOE-NE funded research project used the graphite pile to conduct experiments in support of demonstrating autonomous control of a subcritical system.

The facility is an ideal testbed due to its inherent safety characteristics and modular construction.

These allow in-pile instrumentation and pulley mechanisms to be installed without significant modifications to the facility.

e) The student spectrometer (4DH1) has been used throughout the year to support remote teaching and demonstration of neutron properties. NSE students are using the spectrometer with previously collected data while the reactor has been shut down during the 22.09/22.90 course "Principles of Nuclear Radiation Measurement and Protection". In addition, it is used for demonstrations for Course 16 (Aero/ Astro ).

5 f) Students in the MIT NSE class 22.01 "Introduction to Nuclear Engineering and Ionizing Radiation" were given a demonstration of gamma spectroscopy and on-site lectures about neutron activation analysis.

g) The NRL is continuing to work with researchers from CF Technologies, Inc.

(Hyde Park, MA) to support the application of a new technique for the purification of the medical isotope 177Lu. A proposal is being prepared for testing the technique in the purification of other medical isotopes as well.

h) The recently commissioned reactor simulator was used for training MIT student reactor operators with the reactor shut down. It was also used to demonstrate reactor power changes for MIT nuclear engineering classes (course 22.01 "Introduction to Nuclear Engineering and Ionizing Radiation",

and course 22.011 "Seminar in Nuclear Science and Engineering") as well as other visiting groups.

An ongoing initiative is the partnership with the Department of Energy's Nuclear Science User Facilities (NSUF) for advanced materials, high temperature sensors, and fuel irradiation. The MITR became the first university research reactor to be a partner facility with the NSUF starting in 2008. MIT-NRL staff worked with INL staff to jointly develop advanced reactor instrumentation, promote the use of U.S.

irradiation facilities for materials testing and instrumentation development, and review NSUF's user proposals for various funding opportunity announcements throughout the year.

6

3.

Changes to Facility Design Except as reported in Section E, no changes in the facility design were made during this calendar year. The nominal uranium loading of MITR-11 fuel is 34 grams of U-235 per plate and 510 grams per element (manufactured by BWXT).

Performance of these fuel elements has been excellent.

The loading results in 41.2 w/o U in the fuel meat, based on 7% voids, and corresponds to the maximum loading in Advanced Test Reactor (ATR) fuel.

Two hundred sixty-six elements fabricated by BWXT have been received, forty of which remain in use. One has been removed because of suspected excess out-gassing, two because they were dropped, and two were returned to BWXT without being placed in-core due to not meeting on-site quality assurance inspection criteria.

Two hundred twenty-one have been discharged because they have attained the fission density limit.

The MITR is actively involved in studies for future use of low enrichment uranium (LEU) in the MITR, partially supported by the Reduced Enrichment for Research and Test Reactors (RERTR) Program at DOE. These studies principally focus on the use of monolithic U-Mo fuels with uranium densities in excess of 15 g/cm3 ( compared with 1.5 g/cm3 for UAlx fuel), currently under development by the RERTR Program. Although initial studies show that the use of these fuels is feasible, conversion of the MITR-11 to lower enrichment must await the final successful qualification of these high-density fuels. In October 2018, NRC accepted a report entitled "Low Enriched Uranium (LEU) Conversion Preliminary Safety Analysis Report for the MIT Research Reactor (MITR)" supporting a future application for licensing to convert from High Enriched Uranium (HEU) to LEU fuel.

This PSAR provides analysis determining that a power increase from 6 MW with the current HEU core to 7 MW when using the LEU core is required in order to maintain core neutronic flux performance.

4.

Changes in Performance Characteristics Performance characteristics of the MITR-11 were reported in the "MITR-11 Startup Report."

Minor changes have been described in previous reports.

Performance characteristics of the Fission Converter Facility were reported in the "Fission Converter Facility Startup Report", and in the FY2006 report which described a 20% improvement in the intensity of the unfiltered epithermal neutron beam. In CY2012, fuel was removed from the fission converter tank. The tank will remain unfueled pending resumption of epithermal beam research. In CY2013, the D2O coolant was removed from the fission converter system and replaced with demineralized light water. The D2O was put into on-site storage for future use.

7

5.

Changes in Operating Procedures With respect to operating procedures subject only to MITR internal review and approval, and not covered in Section E of this report, a summary is given below of changes implemented during CY2023.

a) PM 3.1.4 "Non-Routine Reactor Startup" was modified to accommodate changes, which resulted from installing the digital nuclear safety system equipment, to the process for verifying the safety system flux channel calibrations. The modification was judged not to have safety implications, because neither the method of performing the startup nor the temporary scram set points of 2.0 MW and 5.0 MW were affected. (SR #2020-22) b) "MIT Nuclear Reactor Logbook Changes" covered the update to version 2.00 of the software for the digital console logbook. The new version added features that were desired after four years of experience with the original software. The new features included safety improvements, such as checks for personnel licenses and medical exams being current. Other updates modernized cybersecurity functions and included capture of items from the hardcopy Job Workbook. The system backup processes remain unchanged. All of the new software is to run on an independent platform to test it prior to installation.

Additionally, the Job Workbook will be maintained in hardcopy and digitally in parallel for several months before the hardcopy is retired. (SR #2020-31) c) AOP 5.6.3 "Trouble Radiation Monitor" was updated to reflect secondary system upgrades involving the water monitors. A small pump has been added to provide continuous flow > 1 gpm through each monitor, independent of the alignments of the cooling towers and the main secondary pumps. The procedure now includes a step directing, should a low flow condition exist, verification that the pump is operating. This improves safety by providing a response fully consistent with the system's current layout. (SR #2022-12) d) PM 6.6.2.4 "Inventory of Emergency Supplies and Equipment" was revised to align with current procedure formatting guidelines and best practices, and to update the eyewash station inventory.

The revisions were evaluated as maintaining safety unchanged. (SR #2022-9)

8

6.

Surveillance Tests and Inspections There are many written procedures in use for surveillance tests and inspections required by the Technical Specifications. These procedures provide a detailed method for conducting each test or inspection and specify an acceptance criterion which must be met in order for the equipment or system to comply with the requirements of the Technical Specifications. Thirty such tests and inspections are scheduled throughout the year with a frequency at least equal to that required by the Technical Specifications. Together with those not required by Technical Specifications, over 100 tests and calibrations are conducted by Reactor Operations on an annual, semi-annual, or quarterly basis.

Other surveillance tests are done each time before startup of the reactor if shutdown exceeds 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, before startup if a channel has been repaired or de-energized, and at least quarterly; a few are on different schedules. Procedures for such surveillance are incorporated into daily or quarterly startup, shutdown, or other checklists.

During this reporting period, surveillance frequencies have been at least equal to those required by the Technical Specifications, and the results of tests and inspections were satisfactory throughout the year for Facility Operating License No. R-37.

7.

Status of Spent Fuel Shipment In CY2023, there were two shipments made to reduce the inventory of spent fuel at MIT. These shipments are made using the BEA Research Reactor (BRR) package. The U.S. Department of Energy has indicated that further shipments will be feasible in CY2024 for future fuel discharges.

9 B.

REACTOR OPERATION Information on energy generated and on reactor operating hours is tabulated as follows:

Calendar Quarter 1

2 1

3 4

Total

11. Energy Generated (MWD):

a) MITR-II 0

0 0

0 0

(MIT CY2023)

(normally at 5.7 MW) b) MITR-II 43,715.7 (MIT FY1976-CY2022) c) MITR-I 10,435.2 (MIT FY1959-FY1974) d) Cumulative, 54,150.9 MITR-I & MITR-II

2. MITR-II Operation (hours):

(MIT CY2023) a) At Power (2'.: 0.5-MW) for 0

0 0

0 0

Research b) Low Power

(< 0.5-MW) for 0

0 0

0 0

TrainingO) and Test c) Total Critical 0

0 0

0 0

(1)

These hours do not include reactor operator and other training conducted while the reactor is at or above 0.5 MW. Such hours are included in the previous line (row 2a of the table).

C.

SHUTDOWNS AND SCRAMS During this reporting period, there were no inadvertent automatic scrams and no other unscheduled shutdowns.

The term "inadvertent automatic scram" in this section refers to shutting down of the reactor through protective system (nuclear safety or process system) automatic engineered action when the reactor is at power or at least critical; the reactor operator is not involved in the scram action.

The term "other unscheduled shutdown" typically refers to an unscheduled power reduction to subcritical initiated manually by the reactor operator in response to an abnormal condition indication. For such shutdowns, the reactor operator may manually use a "minor scram" (fast control blade insertion by gravity) or a "major scram" (fast control blade insertion plus reflector dump and containment building isolation), among other possible actions.

An example of another type of "other unscheduled shutdown" is a reactor shutdown due to loss of off-site electrical power, because the reactor protective system action was not the cause of the shutdown. An incidental control blade drop is likewise considered an "other unscheduled shutdown",

because such drops lower the reactor power rapidly, and require the console operator to manually bring the reactor to full shutdown condition.

The following summary of inadvertent automatic scrams and other unscheduled shutdowns is provided in approximately the same format as for previous years in order to facilitate a comparison.

I.

Nuclear Safety System Scrams a)

None.

2.

Process System Scrams a)

None.

Total 0

Subtotal 0

0 Subtotal 0

11

3.

Other Unscheduled Shutdowns a)

None.

0 Subtotal 0

Total 0

4.

Experience during recent years has been as follows:

Calendar Year 2023 2022 2021 2020 2019 2018 2017 2016 2015 2014 2013 2012 Nuclear Safety and Process System Scrams O*

2 2

2 3

1 1

4 8

13 4

6

• Reactor remained shut down for maintenance throughout CY2023.

12 D.

MAJOR MAINTENANCE Major reactor maintenance projects performed during CY2023 are described in this Section. These were planned and performed to improve safety, reliability and efficiency of operation of the MIT Research Reactor, and hence improve the reliability of the reactor operating schedule and the availability of the reactor for experiments, research, and training purposes. Additionally, Reactor Operations staff performed safety reviews for all reactor experiments and their operating procedures. The staff also provided support for installations and removals of reactor experiments, and monitored key performance data from the experiments during reactor operations.

For continuous support of neutron transmutation doping of silicon, reactor staff performed routine irradiation and shipping activities. There is an annual external audit to review the program for maintaining the ISO 9001 Certification.

Preventive maintenance on silicon conveyor machinery, such as alignment of conveyor carriages, was performed during major outages.

Major maintenance items performed in CY2023 are summarized as follows:

Date Maintenance Descri:gtion 1/03/2023 Efforts continued to find where the suspected primary system leak was originating. Drive motors for shim blades 1 and 6 were removed to checkfor leaks, and core tank level was lowered to various heights to see if that affected the leak rate. The leak rate was monitored once per shift to check for increase.

1/04/2023

• Work commenced on the Fission Converter. The current fission converter is being revamped to a new experiment called the M3 experiment. This will involve removing many existing structures and parts of the existing fission converter and replacing the components with those for the new experiment. The fission converter tank is stored in the reactor floor corral and will then be reinstalled when the work is completed. Note this is expected to take longer than one year to complete.

1/05/2023 -

Replaced main airlock gasket and tested per leak test procedure.

1/10/2023 During the replacement of this gasket, the door developed a problem in which it needed to be held in the closed position while the gasket was inflating. Troubleshooting on this problem continued until Maintenance found a small foreign object inside the gasket that was delaying the air fill. When the object was removed, the door returned to normal operation.

1/09/2023 Completed removal of the HTWL-FC-1 experiment from core position B-3.

13 1/10/2023 Commenced reorganization of fuel stored in the SFP, to make room for the planned removal of all the fuel from the core tank.

1/11/2023 -

Commenced defueling the reactor. All fuel elements from the fuel 1/18/2023 storage ring in the core tank were transferred to the SFP.

1/19/2023 Repacked Spent Fuel Pool Ion Column and replaced inlet filter.

1/24/2023 -

All fuel in the core was removed and placed in the fuel storage 1/25/2023 ring.

1/25/2023 Installed temporary temperature sensor in SFP.

1/25/2023-Commenced removing fuel in the core tank's storage ring to the 1/31/2023 SFP.

2/01/2023 Experiment junction box, junction box support bracket, and in-core experiment gas lines removed from the core tank.

2/01/2023-Removed shim blade drive mechanisms for blades 2, 3, 4, 5.

2/02/2023 Removed regulating rod and drive mechanism.

2/03/2023 Core tank temporary recirculation system installed.

2/06/2023 -

Began removal of items that penetrate the upper shield access ring 2/08/2023 for eventual removal of the ring to continue leak investigation.

Items removed include the proximity switch tubes and temperature sensors MTS-1 and-lA. Shield system pump PM-1 was secured as shield piping on the reactor top will be removed. The grid latch was opened, and numerous electrical outlets and items attached to the side of the upper shield access ring were removed as well. The fission chambers in the vertical ports for various channels were removed.

The upper shield access ring was then removed to the reactor floor for storage.

2/09/2023 Drained fission converter tank.

2/10/2023 Removed upper shield ring (i.e., second shield ring from top) and stored it on the reactor floor.

Suspected leak found. The leak was at the interface of the MP-6 and MP-6A pressure sensor piping into the core tank. Water was found spraying from the MP-6A fitting.

2/14/2023 Removed the fission converter cadmium shutter to Hot Cell #2.

14 2/15/2023 -

De-energized Circuits Ll/L2 for startup channels, control panel 2/21/2023 power, and power to shim blade servos. Breakers locked open for reactor top work.

2/22/2023 Removed 3GV6 cooling water jacket and placed it in storage.

3/01/2023 Removed upper annular ring (i.e., third shield ring from top) and stored it on the reactor floor.

3/09/2023 -

Replaced blown fuse in MCC-2 for auxiliary fans. Replaced the 3/13/2023 control room fan wiring. Control room fan was then disabled as it was found to be the cause of the auxiliary fans fuse failing.

3/29/2023 Raised core tank level and started primary pumps to test effectiveness of repair/replacement of fittings for the MP-6/MP-6A penetrations. Confirmed repair was successful.

4/07/2023 Moved the fission converter's cadmium shutter from Hot Cell #2 and stored it in the reactor floor corral.

4/19/2023 Reinstalled the upper annular ring and the upper shield ring after refurbishment that included cleaning and anti-rust coating.

5/02/2023 Reinstalled the upper shield access ring.

5/03/2023 Commenced dismantling the 4DHI/2PHI pneumatic tube area to investigate and repair the high argon levels seen in 2022 when the 2PHI tube was,in use. Repairs completed on 8/15/2023.

5/24/2023 RRPO replaced plenum monitor blowers #1 and #2.

5/24/2023 Reconfiguration work on fission converter shielding in progress.

6/17/2023 -

Performed maintenance on the cooling towers in coordination with 6/26/2023 Tower Tech engineers on site.

6/28/2023 Completed installation of security camera system upgrade, after several months of on-site preparatory work. New system was tested satisfactorily.

7/07/2023 Resealed graphite cover gas by refilling mineral oil for its loop seal. Condensate from the graphite area had displaced the oil.

7/07/2023 Secured shield pump PM-I due to leak. Leak repaired and pump restarted on 7/12/2023.

7/08/2023 Main exhaust damper tripped due to oil leak. Repaired on 7/11/2023.

15 7/12/2023 Instrumentation personnel secured the leak tape system to refurbish most of its leak tapes. Returned system to service on 7/26/2023.

7/13/2023 Hot Cell blower secured for maintenance. Returned to operation same day.

7/24/2023 Commenced further cooling tower maintenance work.

Maintenance completed on 7/27/2023.

7/28/2023 Replaced gasket for main airlock outer door after a leak was identified. Tested satisfactory on 8/02/2023.

8/07/2023 Installed new hydraulic pump and pressure switch for the main exhaust damper in response to failure of its hydraulic system.

8/15/2023 Completed annual day-long charcoal filter efficiency testing.

8/18/2023 Repaired core tank level sensor ML-3 and tested it satisfactorily.

8/29/2023 Commenced further maintenance on Cooling Tower #2 (a.k.a.

Cooling Tower B). Maintenance completed on 11/1/2023.

9/07/2023 Repacked and replaced primary ion column.

9/20/2023 Began refueling reactor core from SFP. Completed on 9/28/2023.

Core returned to a loading that matched the December 2022 core.

9/28/2023 Began numerous Tests and Calibrations. This included moving shim blades to verify operability of indicators; it was found that a few of the blades had wiring issues with the indicators. Some of these issues on shim blade #2 continue into CY2024.

9/29/2023 Began returning the detectors for numerous nuclear instruments that were moved during the leak repair, to achieve optimal positions and testing. This continued into CY2024.

10/16/2023 Broken pressure gage found in one of the on-site bulk CO2 storage tanks; replacement ordered by CO2 supply vendor. This was not resolved until CY2024.

10/17/2023 MIT Facilities assisted in closing two 480-volt breakers in the Utility Room after they failed to close properly following the emergency power transfer test. Facilities personnel will follow up procuring replacement breakers for future installation. This continues into CY2024.

10/26/2023 Installed a Pu-Be neutron source into the core in preparation for reactor restart. Source removed on 12/20/2023.

16 11/03/2023 -

Replaced shim blade #4 after it exhibited age-related issues during 11/09/2023 drop time tests.

12/14/2023 Completed repairs on main exhaust damper after it closed without cause on 11/28/2023.

Many other routine maintenance and preventive maintenance items were also scheduled and completed throughout the calendar year.

There was a multi-month project to upgrade the fire protection alarm system in the containment building that lasted into CY2024.

17 E.

SECTION 50.59 CHANGES, TESTS, AND EXPERIMENTS This section contains a description of each change to the reactor facility and associated procedures, and of the conduct of tests and experiments carried out under the conditions of Section 50.59 of 10 CFR 50, together with a summary of the safety evaluation in each case.

Changes that affect only the operating procedures and that are subject only to MITR internal review and approval, including those that were carried out under the provisions of 10 CFR 50.59, are similarly discussed in Section A.5 of this report.

The review and approval of changes in the facility and in the procedures as described in the SAR are documented in the MITR records by means of "Safety Review Forms". These have been paraphrased for this report and are identified on the following pages for ready reference if further information should be required with regard to any item. Pertinent pages in the SAR have been or are being revised to reflect these changes.

The conduct of tests and experiments on the reactor are normally documented in the experiments and irradiation files.

For experiments carried out under the provisions of 10 CFR 50.59, the review and approval is documented by means of the Safety Review Form. This includes all in-core experiments, which are additionally reviewed and approved by the MIT Reactor Safeguards Committee (MITRSC) prior to installation in the reactor core. All experiments not carried out under the provisions of 10 CFR Part 50.59 have been done in accordance with the descriptions provided in Section 10 of the SAR, "Experimental Facilities".

18 Advanced Cladding Irradiation Facility (ACI) \ High Temperature Water Loop SR #0-06-4 (04/03/2006), SR #0-06-6 (05/18/2006), SR #2015-8 (05/22/2015),

SR #2015-9 (05/22/2015), SR #2017-20 (4/01/2019)

An in-core experiment loop was installed on May 22, 2006, to investigate the effects at various stages of irradiation on specimens of silicon carbide intended for use in advanced fuel cladding designs. Its envelope of operating conditions is very similar to that of previous in-core experiments such as the Zircaloy Corrosion Loop and the Electro-Chemical Potential Loop.

No new safety issues were raised.

Operation continued until October 2007. A second advanced cladding loop, designated ACI-2, operated in core from March 2009 through mid-December 2009, March to April 2010, December 2010 through June 2011, from October 2011 to July 2012, and from August through October 2013. A later version of this loop, designated the Westinghouse Accident-Tolerant Fuel (WATF) experiment, was installed in 2014 and operated until May 2015, and again from December 2015 until July 2016. The latter run featured a stepped thimble to minimize neutron streaming to the reactor top. Additionally, from May 2015 to August 2015, the facility was used to test an In-Core Crack Growth Measurement (ICCGM) system. In 2017, from January to June, the ACI facility was used for the COATI irradiation ("CTP and ORNL Accident Tolerant Irradiation") of a variety of silicon carbide composite materials. From August 2017 through the first quarter of 2021, it was used for W ATF Phase 2 and Exelon experiments. In later 2021 and 2022, it saw dry samples - SiC fiber composite coupons from Free Form Fibers and zirconium crystals from Idaho National Laboratory-along with one cycle of fast-response, self-powered neutron detectors from INL in 2022.

Heated In-Core Sample Assembly Experiment (ICSA)

SR #0-04-19 (12/01/2004), SR #M-04-2 (12/30/2004), SR #0-05-11 (07/22/2005),

SR #M-09-1 (07/30/2009), SR #M-09-2 (12/11/2009), SR #0-10-2 (03/28/2010),

SR #0-12-17 (06/04/2012), SR #0-12-19 (07/09/2012), SR #2017-6 (7/02/2019),

SR #2017-6A (05/03/2017)

High-temperature sample capsules were used with the redesigned titanium 2" ICSA tube to provide a heated irradiation environment for the specimens within.

These capsules include gamma-heating susceptors similar in principle to the High Temperature Irradiation Facility. No new safety issues were raised. An alternate 16" plug was designed and installed in the reactor top shield lid to allow simultaneous use of the ICSA and the ACI-2 in-core experiments. The ICSA operated in core from December 2009 through April 2010, from August 2010 to January 2012, from April to July 2012, and from mid-September through October 2013 for various sample irradiations using heated and unheated capsules.

The MIT Reactor Safeguards Committee (MITRSC) approved two ICSA Safety Evaluation Report amendments in early 2013 to allow the 2013 irradiation of molten fluoride salt in-core using a nickel capsule inside the ICSA. The ICSA facility remained in regular use in CY2021 for in-core experiments and irradiations. - See section A.2 (Experiments and Utilization),

items (c), (d), and (e).

19 Physical Security Plan Revisions SR #0-13-16 (05/12/2014), SR #0-13-30 (12/24/2013), SR #2014-19 (11/07/2014),

SR #2014-23 (02/18/2015), SR #2015-5 (01/23/2015), SR #2017-5 (2/14/2017),

SR #2019-7 (06/11/2019), SR #2019-9 (09/27/2019), SR #2021-2 (01/25/2021)

SR #2021-2A (04/12/2021), SR #2021-2C (04/28/2021), QA #2022-25 (in progress)

MITRSC approval for the revised Plan was granted per the Security Subcommittee meeting of 6/6/2013. It was then submitted to NRC as a License Amendment Request, and approved by NRC in 2014. In 2015, a security alarm coincidence monitoring system was installed to provide local and remote notification should the weekend alarm or an intrusion alarm become deactivated during periods of unattended shutdown. Procedures were revised to incorporate use of this monitoring system. In 2017, the Plan was revised in response to an NRC Request for Additional Information (RAI) regarding incorporation of material from NRL's responses to NRC Compensatory Action Letters. The revision and response to NRC were approved by the MITRSC Special Subcommittee for Security. In 2018, further modifications to the Plan were proposed as a followup to the RAI, and were reviewed and approved by the MITRSC in October 2018. These proposed modifications were discussed with NRC during a routine inspection in December 2018.

In May 2019, all proposed modifications to the Plan and associated security procedures were presented to the MITRSC Security Subcommittee, including proposed changes to AOP 5.8.22 "Loss or Degradation of a Security System", in accordance with new regulatory guidelines that were incorporated into the Security Plan. The Subcommittee approved the modifications, and the Plan was submitted to NRC on 6/11/2019. On 7/29/2019, NRC was satisfied with the update as being in compliance with 10 CFR 73 and incorporating all of the site-specific compensatory measures to which MIT had committed. NRC then closed Confirmatory Action Letter (CAL) No. NRR-02-005 which had been issued in 2002 in response to the 9/11 national emergency.

In CY2021, conversion from the C*CURE security management system to the Genetec system being adopted throughout the MIT campus was implemented for the reactor facility. It included, for compatibility with the new system, replacement of the iris readers with other biometric readers, with a corresponding Physical Security Plan revision sent to NRC in April 2021, shortly after the completion of the upgrade. Other security devices were either replaced or retrofitted with external interfaces to make them compatible with the new system.

A comprehensive system-wide test was performed immediately afterwards, and again in CY2022, proving the conversion successful.

In CY2022, the NRL worked with DOE-PNNL for grant funding to upgrade the security camera system for the reactor. A contract was awarded and accepted by MIT in September 2022. Due to supply-chain issues, installation was postponed until mid-CY2023. The system was commissioned on June 28, 2023, and was accepted as satisfactory in an Assurance Site Visit by PNNL project managers on August 16, 2023.

Reactor Operations submitted the first quarterly report on the system to PNNL on November 16, 2023.

20 Stack Effluent & Water Monitor Project SR #2015-30 (pending), SR #2015-30A (12/02/2015), SR #2015-30B (07/08/2016),

SR #2015-30C (03/31/2016), SR #2015-30E (04/21/2017)

As part of a project to install new stack effluent monitors and secondary water monitors using detectors located outside the containment building, a new 1-1/4" diameter piping penetration was installed on the south side of the containment building, about four feet below ground. It was tested as satisfactory per existing procedures for pressure-testing new penetrations. Until such time as it is connected to the main system piping, the new piping will remain blank-flanged, or isolated and tagged out, in order to ensure containment integrity is maintained. A new climate-controlled shed, the "stack monitor shed", was constructed in the reactor's back yard in CY2016, with the two new stack monitor stations fully mounted within. In CY2019 through CY2023, this newly-installed system continued to operate in parallel with the existing stack effluent and water monitoring systems.

D2O Helium System Modifications SR #2022-10 (05/20/2022), SR #2022-18 (03/09/2023), SR #2022-19 (12/10/2022),

SR #2023-10 (11/30/2023)

The D2O reflector helium cover gas system was upgraded to eliminate the gasholder as the method to control routine supply and relief of the helium cover gas.

The gasholder was replaced with a high-flow, low-pressure regulator with an integral overpressure relief port. The cover gas system's overpressure and underpressure safety components were not affected by this change. The regulator's output setting of two inches of water pressure matches the previous gasholder blanket pressure. Various startup, shutdown, operating, testing, and calibration procedures were modified and fine-tuned for use with the new system.

Identification and Repair of Primary System Leak SR #2023-1 (01/27/2023), SR #2023-2 (09/08/2023), SR #2023-9 (08/07/2023)

The MIT Reactor was shut down on December 12, 2022, in response to indications of a water leak from the primary coolant system. Subsequently the leak rate was confirmed to be steady at ~7.5 gallons/day. Lowering the core tank water level to the height of the anti-siphon valves halted the leak. After defueling the core tank and removal of several annular shield rings surrounding the reactor vessel, in February 2023, the leak was confirmed to be coming from a pipe fitting that penetrates the main core tank flange for pressure sensor MP-6A. The pipe fitting was replaced.

Other penetrations around the core were inspected, and one other similar fitting was replaced as a preventive measure. These pipe penetrations were found covered in iron rust from the annular shield rings. The pipes and all surrounding areas were cleaned.

All surfaces of the shield rings were reconditioned by grinding and sanding, and then covered with an anti-rust coating. The leak was confirmed repaired successfully.

21 Afterward, all the shield rings were returned to their locations surrounding the reactor vessel, along with reinstallation of all the shim blade drives, the regulating rod drive, and sensors for core tank level, flow, temperature, and pressure.

After completion of all corresponding instrumentation tests and calibrations, and creation of a special procedure for the moves, the core tank was re-fueled in September 2023.

Preparations for reactor restart continued for the rest of 2023, including temporary installation of a Pu-Be neutron source, and some adjustment of fission chamber positions in order to compensate for the photo-neutron source from the reactor's D20 reflector system diminishing over time while shut down.

22 F.

ENVIRONMENTAL SURVEYS Environmental monitoring is performed using continuous radiation monitors and passive dosimetry devices (TLD). The radiation monitoring system consists of detectors and associated electronics at each remote site with data transmitted continuously to the Reactor Radiation Protection office and recorded electronically in a database. The environmental monitoring remote sites are located within a quarter mile radius of the facility. The calendar year totals per sector, due primarily to Ar-41, are presented below. There was no production or release of Ar-41 in the calendar year. The passive TLDs were in place at all times throughout the year and are exchanged quarterly.

Site North East South West Exposure (01/01/2023 -12/31/2023) 0.00mrem 0.00mrem 0.00mrem 0.00mrem Calendar Year Average 2023 0.0 mrem 2022 0.7 mrem 2021 0.2mrem 2020 0.2 mrem 2019 0.2mrem 2018 0.2 mrem 2017 0.4 mrem 2016 0.6 mrem 2015 0.4 mrem 2014 0.8 mrem 2013 0.2 mrem 2012 0.3 mrem

23' G.

RADIATION EXPOSURES AND SURVEYS WITHIN THE FACILITY A summary of radiation exposures received by facility personnel and experimenters is given below:

January 1, 2023 - December 31, 2023 Whole Body Exposure Range (rems)

Number of Personnel No measurable.......................................................................................... 107 Measurable - < 0.1...................................................................................

36 0.1 0.25 5

0.25 -

0.50 0.50 0.75 0.75 1.00 1.00 1.25 1.25 1.50 1.50 -

1.75 1.75 2.00 Total Person Rem= 1.76 Total Number of Personnel= 149 1

0 0

0 0

0 0

From January 1, 2023, through December 31, 2023, the Reactor Radiation Protection program provided radiation protection services for the facility which included power and non-power operational surveillance (performed on daily, weekly, monthly, quarterly, and other frequencies as required), maintenance activities, and experimental project support. Specific examples of these activities included, but are not limited to, the following:

1.

Collection and analysis of air samples taken within the containment building and in the exhaust/ventilation systems.

2.

Collection and analysis of water samples taken from the secondary, D2O, primary, shield coolant, liquid waste, and experimental systems, and fuel storage pool.

3.

Performance of radiation and contamination surveys, radioactive waste collection and shipping, calibration of area radiation monitors, calibration of effluent and process radiation monitors, calibration of radiation protection/survey instrumentation, and establishing/posting radiological control areas.

4.

Provision of radiation protection services during fuel movements, in-core experiments, sample irradiations, beam port use, ion column removal, diffractometer beam testing, etc.

The results of all surveys and surveillances conducted have been within the guidelines established for the facility.

24 H.

RADIOACTIVE EFFLUENTS This section summarizes the nature and amount of liquid, gaseous, and solid radioactive wastes released or discharged from the facility.

1.

Liquid Waste Liquid radioactive wastes generated at the facility are discharged only to the sanitary sewer serving the facility. The possible sources of such wastes during the year include cooling tower blowdown, the two on-site liquid waste storage tanks, and one controlled sink in the Restricted Area (Engineering Lab).

All of the liquid volumes are measured, by far the largest being the 266,377 liters discharged during CY2023 from the cooling towers. (Other large quantities of non-radioactive waste water are discharged to the sanitary sewer system by other parts of MIT, but no credit for such dilution is taken because the volume is not routinely measured.)

Total activity less tritium in the liquid effluents (cooling tower blowdown, waste storage tank discharges, and engineering lab sink discharges) amounted to 2.55E-4 Ci for CY2023.

The total tritium was 7.47E-2 Ci.

The total effluent water volume was 281,561 liters, giving an average tritium concentration of 2.37E-4 µCi/ml.

The above liquid waste discharges are provided on a monthly basis in the following Table H-3.

All releases were in accordance with Technical Specification 3.7.2.1, including Part 20, Title 10, Code of Federal Regulations. All activities were substantially below the limits specified in 10 CFR 20.2003 "Disposal by Release into Sanitary Sewerage".

Nevertheless, the monthly tritium releases are reported in Table H-3.

2.

Gaseous Waste Gaseous radioactivity is discharged to the atmosphere from the containment building exhaust stack. All gaseous releases likewise were in accordance with the Technical Specifications and 10 CFR 20.1302, and all nuclides were substantially below the limits, using the authorized dilution factor of 50,000. Because the reactor did not operate in CY2023, the only nuclide was H-3. The 46 Ci of H-3 was released at an average concentration of 7.3E-12 µCi/ml. This represents 0.01 % of EC (Effluent Concentration (lE-08 µCi/ml)).

3.

Solid Waste Two shipments of solid waste were made during the calendar year.

The information pertaining to these shipments is provided in Table H-2.

25 TABLE H-1 ARGON-41 STACK RELEASES CALENDAR YEAR 2023 Ar-41 Average Discharged Concentration(!)

(Curies)

(uCi/ml)

January 2023 0

0.0 February 0

0.0 March 0

0.0 April 0

0.0 May 0

0.0 June 0

0.0 July 0

0.0 August 0

0.0 September 0

0.0 October 0

0.0 November 0

0.0 December 0

0.0 Totals ( 12 Months )C2) 0 0

EC (Table II, Column I) 1 X 10-8

%EC 0%

(1) Average concentrations do not vary linearly with curies discharged because of differing monthly dilution volumes.

(2) Last decimal place may vary because of rounding.

26 TABLE H-2

SUMMARY

OF MITR-II RADIOACTIVE SOLID WASTE SHIPMENTS CALENDAR YEAR 2023 Descriptions Volume 51.35 ft3 Weight 464 lbs.

Activity 6.8 mCi Date of shipment April 19, 2023 Waste processor NIA Direct for Burial Waste broker Energy Solutions, Clive, UT Disposition to licensees for burial Energy Solutions, Clive, UT Volume 60 ft3 Weight 1489 lbs.

Activity 9.8 mCi Date of shipment December 7, 2023 Waste processor Toxco Material Management Center, Oak Ridge, TN Waste broker Ecology Services Inc., Columbia, MD Disposition to licensees for burial Energy Solutions, Clive, UT

Jan.2023 Feb.

Mar.

Apr.

May June July Aug.

Sept.

Oct.

Nov.

Dec.

12 months 27

. TABLE H-3 LIQUID EFFLUENT DISCHARGES CALENDAR YEAR 2023 Total Total Volume Activity Tritium of Effluent Less Tritium Activity WaterC1)

(xl0-6 Ci)

(mCi)

(liters) 151 39.2 30825 NDAC2) 0.03 7377 NDAC2) 0.01 24931 NDA(2) 0.006 12868 NDAC2) 0.007 20177 NDAC2) 0.002 33992 NDAC2) 0.004 21703 9.78 20.4 32558 NDAC2) 0.002 27678 90.3 1.29 26968 NDA(2) 0.002 27055 4.75 13.7 15430 255 74.7 281561 Average Tritium Concentration (xl o-6 µCi/ml) 1272 3.9 0.402 0.485 0.365 0.065 0.195 626 0.066 47.9 0.064 889 236.8 (1) Volume of effluent from cooling towers, waste tanks, and NW12-139 Engineering Lab sink. Does not include other diluent from MIT estimated at l.0x107 liters/day.

(Z) No Detectable Activity (NDA): less than l.26xl0-6 µCi/ml beta for each sample.

28 I.

SUMMARY

OF USE OF MEDICAL FACILITY FOR HUMAN THERAPY The use of the medical therapy facility for human therapy is summarized here pursuantto Technical Specification No. 7.7.1.9.

1.

Investigative Studies Investigative studies remain as summarized in the annual report for FY2005.

2.

Human Therapy None.

3.

Status of Clinical Trials The Phase I glioblastoma and melanoma trials with BIDMC have been closed.

A beam that is superior to the original epithermal beam in the basement Medical Therapy Room in both flux and quality could again be made available from the Fission Converter Facility. No use of that beam is anticipated in the near term because of a nationwide funding hiatus for work of this type.