ML22154A549

University of California - Davis, MNRC 2021 Annual Report

ML22154A549
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Site:	University of California-Davis
Issue date:	06/03/2022
From:	McClellan Nuclear Research Center
To:	Document Control Desk, Office of Nuclear Reactor Regulation
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2021 ANNUAL REPORT Docket Number 50-607 License Number R-130

UCD/MNRC ANNUAL REPORT FOR 2021

1. Introduction The University of California, Davis, McClellan Nuclear Research Center (UCD/MNRC) consists of a research reactor, associated radiography and positioning equipment, and a wide variety of equipment to support broad-based research activities. This Annual Report is published each year in support of the license provided by the United States Nuclear Regulatory Commission (NRC). The aforementioned license is for the operation of a steady-state TRIGA' reactor.

The intent of this document is to provide information relevant to the operation and safety of the UCD/MNRC. A brief description of the UCD/MNRC facility and administration is followed by an operational summary and health physics information for this facility during CY 2021.

2. UCD/MNRC Facility Description The UCD/MNRC is located on the McClellan Industrial Park site; the reactor is housed in Building 258. The McClellan Industrial Park site is approximately 2600 acres, located eight miles northeast of Sacramento, California.

The UCD/MNRC facility is a three-level ~18,000 sq. ft. rectangular-shaped enclosure that surrounds a 2 MW research reactor. The UCD/MNRC provides four neutron beams to four bays for radiography and other research and commercial activities. Space, shielding and environmental controls are provided by the enclosure for neutron radiography operations performed on a variety of samples.

In addition to the radiography bays, the UCD/MNRC reactor also has several in-core facilities ranging from a pneumatic tube system to a central irradiation facility.

For more detailed information on the UCD/MNRC project, the reader is referred to the UCD/MNRC Safety Analysis Report.

3. UCD/MNRC Administration The UCD/MNRC is licensed by the Nuclear Regulatory commission (NRC) to operate under the provisions of operating license R-130. The University of California Regents have designated the Chancellor at UC Davis to be the license holder. The UCD Chancellor has in-turn delegated the Vice Chancellor for Research to be the licensee of record.

The UCD/MNRC is under the direction of the UCD/MNRC Director.

UCD/MNRC ANNUAL REPORT FOR 2021

4. Operating Experiences 4.1 Experiments No new experiments were approved this year, and no changes were made to existing experiments. Table 4.1 shows the number of experiments conducted in each experiment facility:

TABLE 4.1 2021

SUMMARY

OF EXPERIMENTS Number of Typical Experiment Facility Experiment Facility Experiments Utilization Central Irradiation Facility 6 In-tank, in-core irradiations Pneumatic Transfer System 0 In-tank, out-of-core, fast neutron Neutron Irradiator 10 irradiations Silicon Fixture 11 In-tank, out-of-core irradiations Bay 1 964 Bay 2 1740 Neutron radiography Bay 3 94 Bay 4 58 4.2 Changes in Facility Design There were no changes in the design of the UCD/MNRC facility.

4.3 Changes to Performance Characteristics and Operating Procedures The latest thermal hydraulic analysis provided to the NRC concluded that a critical heat flux of 2.0 is reached with the current core configuration somewhere between 1.2 and 1.3 MW. As a result, the following changes have been made:

1. The annual reactor power calibration was performed at 800kW instead of 1600 kW.

2. The annual high-power scram tests were performed using the TRIGA prestart check routine and the console scram test functions for both power level safety channels instead of operating at the SCRAM setpoint (~2.14 MW).

3. As of November 5, 2021, the UCD/MNRC is administratively limited to steady state reactor operations at 1.0 MW or less. Reactor pulsing is not allowed and reactor power shall not exceed 1.2 MW for any reason.

These changes were analyzed through 50.59 Screening processes. It was determined that none of the changes qualified as facility modifications. 50.59 Screenings for the changes to the reactor power calibration and high-power SCRAM tests were approved on September 30, 2021, and the screening for the 1.0 MW administrative power limit was approved on November 5, 2021.

UCD/MNRC ANNUAL REPORT FOR 2021 4.4 Surveillance Tests and Inspection Results Surveillance tests and inspections were performed as required by the UCD/MNRC Technical Specifications with satisfactory results for all systems.

The annual reactor maintenance shutdown was completed during the month of August. During the shutdown, inspection of fuel elements and control rods was performed in accordance with the UCD/MNRC Technical specifications. All fuel element and control rod measurements were within the tolerances defined in the Technical Specifications, and there were no indications of deterioration or damage to any of the inspected elements or control rods systems.

Parametric values noted during testing were as follows:

Control Rod Worth:

Transient Rod: $1.83 Regulating Rod: $2.74 Shim 1: $2.54 Shim 2: $2.49 Shim 3: $2.50 Shim 4: $2.92 Control Rod Drop Times (in Seconds):

Transient Rod: 0.36 Regulating Rod: 0.41 Shim 1: 0.39 Shim 2: 0.37 Shim 3: 0.42 Shim 4: 0.40 Shutdown Margin: $6.78 Nuclear instrument calorimetric calibrations were performed during the annual reactor maintenance period. Minor adjustments were made to the NPP-1000 and NM-1000 detectors to match the measured calorimetric power.

5. Energy Generated by the Reactor TOTAL OPERATING HOURS THIS YEAR: 1527.48 TOTAL OPERATING HOURS: 57714.21 TOTAL MEGAWATT HOURS THIS YEAR: 1445.30 TOTAL MEGAWATT HOURS: 71929.29 TOTAL NUMBER OF PULSES PERFORMED THIS YEAR: 0 TOTAL NUMBER OF PULSES PERFORMED: 484

UCD/MNRC ANNUAL REPORT FOR 2021

6. Unscheduled Reactor Shutdowns There were three SCRAMs and one unscheduled shutdown in 2021. Each event is described in Table 6.1:

TABLE 6.1 2021

SUMMARY

OF UNSCHEDULED REACTOR SHUTDOWNS Date Event Description of Event 2/18/2021 Silent At 16:22, the reactor was operating at 1.0 MW steady-state SCRAM power in the automatic mode when it was observed that all of the control rods had separated from their electromagnets and were fully inserted into the reactor core. The electromagnets were still energized, but all other indications of reactor power, reactor period, and fuel element temperatures confirmed the reactor was subcritical with a negative period. There was no visual, audible, or recorded cause of the control rod separations, and there was no obvious external event that could explain the silent SCRAM, which is believed to have been caused by a momentary loss of electromagnet power. After de-energizing the electromagnets by initiating a manual SCRAM, control rod operability and SCRAM time checks were performed for each control rod. All checks were completed satisfactorily.

Normal operations were resumed. The problem did not reoccur.

3/11/2021 Unscheduled At 12:49, the reactor was shut down to look for a possible Shutdown item dropped in the reactor tank. A pen was found at the bottom of the tank.

4/15/2021 Database At 12:26, a reactor SCRAM was initiated by a Database Timeout Timeout. The error cleared on acknowledgement.

SCRAM 11/17/2021 Manual At 13:10, a reactor SCRAM was initiated by the inadvertent SCRAM operation of the Reactor Room Manual SCRAM Button.

7. Maintenance Operations Scheduled preventative maintenance items were conducted throughout the year with satisfactory results and no major issues. The annual reactor maintenance shutdown was completed in August. During the shutdown, preventative maintenance was performed on the control rod drives and radiography bay shielding doors. No significant issues were identified.

Control rod, nuclear instrument, and fuel temperature calibrations were also performed satisfactorily during the shutdown. Preventative maintenance on the cooling tower was performed satisfactorily in December.

Non-routine maintenance items related to systems that may be associated with reactor safety are described in the Table 7.1.

UCD/MNRC ANNUAL REPORT FOR 2021 TABLE 7.1 2021

SUMMARY

OF NON-ROUTINE MAINTENANCE Open date Close date Description 5/14/2021 5/17/2021 An air leak was repaired in the Bay 3 fast shutter actuation system. This shutter is used for radiography, not biological shielding. There was no impact on safety.

6/23/2021 6/23/2021 The Reactor Room Continuous Air Monitors motor power switch was replaced. It was hot to the touch. There was no impact on reactor safety.

7/20/2021 7/20/2021 The Reactor Room Continuous Air Monitors fuse holder was replaced. It was getting hot during operation. There was no impact on reactor safety.

9/30/2021 1/28/2022 A leak in the fire sprinkler system was repaired and a few sprinkler heads were replaced. The leak was not significant enough to render the system inoperable. There was no impact on reactor safety.

11/1/2021 11/5/2021 Dedicated ground conductor bars and tandem collectors were installed on Bay 2 & 3 Staging Area, Bay 4 Staging Area, and Equipment Room cranes to conform with current crane requirements. There was no impact on reactor safety.

11/4/2021 11/4/2021 A leak was repaired in the helium line leading to the Bay 4 beam tube. The leak was in the reactor room. It was identified and repaired before the helium supply was depleted.

There was no impact on reactor safety.

12/2/2021 12/2/2021 The depleted inlet deionizing resin bottles to the reactor makeup water tank were replaced. There was no impact on reactor safety.

12/1/2021 12/1/2021 The reactor rooms air conditioner (AC-1) was not providing heating service and was repaired. There was no impact on reactor safety.

12/16/2021 Repairs in The primary cooling systems ultrasonic flow sensor stopped Progress reporting flow measurements. It has been taken out of service. A replacement system has been identified and will be installed when it arrives. The loss of the flow sensor does not impact reactor safety. Primary coolant flow is still monitored and reported to the reactor operator by the primary flow proof switch, and the failed sensor is not required by the UCD/MNRC Technical Specifications.

8. Facility and Procedure Changes 8.1 Facility Modifications One class III facility modification, FMIII-21-001: Removal of Bay 3 SAIC Plug Beamline Insert, was performed in 2021. The goal of the modification was to remove a plug at the end of the Bay 3 beamline and increase the size of the neutron beam so that the bay could better support neutron radiography. An evaluation of the proposed modification was performed prior to starting work on the project. It was concluded

UCD/MNRC ANNUAL REPORT FOR 2021 that the change did not meet any of the 10 CFR 50.59 criteria, and therefore, no license amendment or change to the Technical Specifications was required. Special Operating Procedure, SOP 21-01, was created for the modification. Work was successfully completed on May 10, 2021. A radiological survey was performed after the modification was completed. Radiation levels remained in compliance with pre-modification radiation postings and all other applicable provisions of 10 CFR Part 20.

8.2 Procedure Changes Some preventative maintenance and surveillance frequencies were adjusted in 2021.

All surveillance items remain in compliance with the requirements of the UCD/MNRC Technical Specifications. These changes were evaluated in a 50.59 screening on December 3, 2021. Table 8.1 provides details on changes that are associated with systems related to reactor safety.

TABLE 8.1 2021

SUMMARY

OF CHANGES TO PROCEDURE FREQUENCIES Frequency Item Change* Reason for Change CALIBRATION - BAY CAM A Remove BAY CAM - Oil change and Bay CAM is no longer in service Q Remove greasing Secondary water conductivity and pH are continuously monitored by Sample Secondary Water M Remove the secondary cooling systems chemical addition system Cycle Demineralizer Valves M S Frequent valve operation may lead Cycle Primary Valves M S to leaks or premature failure Cycle Secondary Valves M S There are no penetrations in the reactor tank, no history of tank leaks, and tank water level is Check the Tell-Tale Drain M Remove monitored regularly as part of reactor startup and shutdown procedures Drain and Clean Cooling Sediment and contaminant levels Q A Tower do not warrant quarterly cleaning Calibrate ECCS Supply The 1 MW administrative restriction S Suspend Pressure gauge. placed on reactor operations as of Perform flow test of ECCS November 5, 2021 suspends the S Suspend supply. need perform surveillance items on Flow test in-tank ECCS flow the ECCS, AMUWS, and Generator S Suspend nozzle systems.

Change Generator A Suspend Crankcase Oil and Oil Filter Sample AMUWS for Activity S Suspend

UCD/MNRC ANNUAL REPORT FOR 2021 Exercise Generator set W Suspend Sample AMUWS System M Suspend The 1 MW administrative restriction Clean AMUWS Demin FM A Suspend placed on reactor operations as of batt. Terminals November 5, 2021 suspends the Calibrate AMUWS pressure need perform surveillance items on A Suspend gauges the ECCS, AMUWS, and Generator Clean and Inspect Power systems.

A Suspend Transfer Switch Clean Propane Generator Air B Suspend Cleaner Leaks in the helium system are Leak Check the Helium effectively identified by routine Pressurization System M Remove observation of helium tank Mechanical Joints pressure

• M = Monthly, Q = Quarterly, S = Semi-Annually, A = Annually Remove = Item completely removed from Preventative Maintenance Management System Suspend = Item temporarily suspended while not required

UCD/MNRC ANNUAL REPORT FOR 2021

9. Radioactive Effluents A summary of the nature and amount of radioactive effluents released or discharged to the environment beyond the effective control of the MNRC, as measured at or prior to the point of such release or discharge, include the following:

9.1 Liquid Effluents No liquid effluents were released during 2021.

9.2 Airborne Effluents Airborne radioactivity discharged during 2021 is tabulated in Table 9.1 below.

TABLE 9.1 2021

SUMMARY

OF AIRBORNE EFFLUENTS MONTH TOTAL CALCULATED AVG. CALCULATED FRACTION OF 10 RELEASED RELEASED MEASURED CONC. OF DOSE CFR 20 DOSE PARTICULATE PART. ACT.

Ar-41 Ar-41 IN FROM Ar-41 LIMIT FORM WITH RELEASED RELEASED UNRESTRICTED IN HALF-LIFE WITH HALF-AREA (1) UNRESTRICTED >8 DAYS LIFE > 8 DAYS AREA (Ci) (uCi/ml) (mrem) (%) (Ci) (uCi/ml)

JAN 2.81 2.82E-10 0.12 1.2 NONE NONE FEB 2.86 2.87E-10 0.12 1.2 NONE NONE MAR 3.29 3.30E-10 0.14 1.4 NONE NONE APR 3.08 3.09E-10 0.13 1.3 NONE NONE MAY 2.31 2.32E-10 0.10 1.0 NONE NONE JUN 2.32 2.33E-10 0.10 1.0 NONE NONE JUL 2.59 2.60E-10 0.11 1.1 NONE NONE AUG 1.62 1.63E-10 0.07 0.7 NONE NONE SEP 2.43 2.44E-10 0.10 1.0 NONE NONE OCT 2.60 2.61E-10 0.11 1.1 NONE NONE NOV 2.17 2.18E-10 0.09 0.9 NONE NONE DEC 1.93 1.94E-10 0.08 0.8 NONE NONE TOT 30.02 1.25 12.5 NONE NONE AVG 2.50 2.51E-10 (1) This location is 100 meters downwind which is the point of maximum expected concentration of Ar-41 based on an average wind speed of 2 m/s and atmospheric stability class B.

UCD/MNRC ANNUAL REPORT FOR 2021 9.3 Solid Waste No solid radioactive waste was shipped this year.

10. Radiation Exposure Radiation exposure received by facility operations personnel, facility users, and visitors during 2021 is summarized in Table 10.1 below.

TABLE 10.1 2021

SUMMARY

OF PERSONNEL RADIATION EXPOSURES NUMBER OF AVERAGE GREATEST AVERAGE GREATEST INDIVIDUALS TEDE INDIVIDUAL EXTREMITY EXTREMITY PER TEDE (1)

INDIVIDUAL (mrem) (mrem) (mrem)

(mrem)

FACILITY 10 38 110 170 420 PERSONNEL FACILITY 143 <1.0 2.0 *

• USERS VISITORS 462 <1.0 1.0 * *

(1) Only 3 individuals received extremity exposure

• Extremity monitoring was not required.

UCD/MNRC ANNUAL REPORT FOR 2021

11. Radiation Levels and Levels of Contamination Radiation levels and levels of contamination observed during routine surveys performed at the MNRC during 2021 are summarized in Table 11.1 below.

TABLE 11.1 2021

SUMMARY

OF RADIATION LEVELS AND CONTAMINATION LEVELS DURING ROUTINE SURVEYS AVERAGE HIGHEST AVERAGE HIGHEST (mrem/hr) (mrem/hr) (dpm/100cm2) (dpm/100cm2)

OFFICE SPACES <0.1 <0.1 <5000(1) <5000(1)

REACTOR CONTROL RM <0.1 <0.1 <5000(1) <5000(1)

RADIOGRAPHY CONTROL RM <0.1 <0.1 <5000(1) <5000(1)

COUNTING LAB <0.1 <0.1 <5000(1) <5000(1)

STAGING AREA <0.1 <0.1 <5000(1) <5000(1)

FACILITY (Fenceline) <0.1 <0.1 <5000(1) <5000(1)

EQUIPMENT RM 0.6 (4) 70 (5) <800(2) <800(2)

DEMINERALIZER AREA 13(4) 220(5) <800(2) <800(2)

REACTOR RM 4.0(4) 590(5) <800(2) <800(2)

RADIOGRAPHY BAYS 0.5(3) 215 <800(2) <800(2)

(1) <5000 dpm/100 cm2 = Less than the lower limit of detection for a scanning survey.

(2) <800 dpm/100 cm2 = Less than the lower limit of detection for a swipe survey.

(3) Due to Bay 1 Storage Areas; all other areas and bays are significantly lower (typically <0.1 mrem/hr).

(4) General area dose rate.

(5) Maximum contact dose rate.

UCD/MNRC ANNUAL REPORT FOR 2021

12. Environmental Surveys Environmental surveys performed outside of the MNRC during 2021 are summarized in Tables 12.1 & 12.2 below. The environmental survey program is described in the UCD/MNRC Safety Analysis Report.

TABLE 12.1 2021

SUMMARY

OF ENVIRONMENTAL TLD RESULTS (WITH NATURAL BACKGROUND(1) SUBTRACTED)

AVERAGE HIGHEST (mrem) (mrem)

ON SITE (SITES 50 - 61 & 65-71) 15 27 (1) Natural background assumed to be the off park (Sites 27-42) average of 57 mrem.

(2) This report no longer includes the on base sites as has not been relevant since 2000.

TABLE 12.2 2021

SUMMARY

OF RADIOACTIVITY IN WELL WATER ALPHA BETA TRITIUM Cs-137 (pCi/l) (pCi/l) (pCi/l) (pCi/l)

AVERAGE <MDA 1.07 <MDA <MDA HIGHEST <MDA 1.92 <MDA <MDA MDA is the minimum detectable activity at the 95% confidence level.

The MDA range for the analyzed radionuclides (pCi/L).

MIN MAX Alpha 2.50 4.09 Beta 1.70 1.92 Tritium 169 230 Cs-137 16.9 23.0