ML24143A143
| ML24143A143 | |
| Person / Time | |
|---|---|
| Site: | University of California-Davis |
| Issue date: | 05/22/2024 |
| From: | McClellan Nuclear Research Center |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML24143A141 | List: |
| References | |
| Download: ML24143A143 (1) | |
Text
1 University of California Davis McClellan Nuclear Research Center 2023 ANNUAL REPORT Docket Number 50-607 License Number R-130
2
- 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 facility operating license, R-130, provided by the United States Nuclear Regulatory Commission (NRC), which authorizes operation of the facilitys TRIGA' reactor at steady-state power levels not in excess of 1,000 kilowatts in accordance with the limitations of the facilitys Technical Specifications.
The Regents of the University of California hold the facility operating license for the UCD/MNRC.
The Regents delegate license holder duties to the UC Davis Chancellor, and the Chancellor delegates license holder duties to the Vice Chancellor of Research. The UCD/MNRC facility is under the direct control of the UCD/MNRC Director.
The UCD/MNRC provides four neutron beams to four bays for radiography and other research and commercial activities. 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, the reader is referred to the UCD/MNRC Safety Analysis Report.
- 2. Summary of Operating Experience Reactor operation was typically conducted at 800 kW steady-state until October 4, 2023, when reactor operation was restricted to 700 kW steady-state during the break-in period for a new 30/20 IFE that was introduced into the core as part of a new core configuration following the annual reactor shutdown for maintenance and fuel inspections. On October 30, 2023, reactor operating power was raised to 750 kW steady-state for the remainder of the year.
Two prolonged shutdowns occurred while the facility was awaiting license amendments. The first shutdown was in February, while awaiting the review and issuance of Amendment No. 9 to the Renewed Facility Operating License. The second shutdown was from the end of July to the end of September, while awaiting the review and issuance of Amendment No. 10 to the Renewed Facility Operating License.
The majority of experiments conducted at the UCD/MNRC utilized the neutron radiography facilities.
No new experiments were approved this year. Table 2.1 shows the number of experiments conducted in each experiment facility:
TABLE 2.1
SUMMARY
OF EXPERIMENTS Experiment Facility Number of Experiments Typical Experiment Facility Utilization Central Irradiation Facility 5
In-tank, in-core irradiations Pneumatic Transfer System 6
Neutron Irradiator 15 In-tank, out-of-core, fast neutron irradiations Silicon Fixture 10 In-tank, out-of-core irradiations Bay 1 755 Neutron radiography Bay 2 1309 Bay 3 746 Bay 4 50 The energy generated by the reactor and the hours the reactor was critical are shown below in Table 2.2:
3 TABLE 2.2 ENERGY GENERATED BY THE REACTOR AND HOURS THE REACTOR WAS CRITICAL TOTAL OPERATING HOURS THIS YEAR:
1105.03 TOTAL OPERATING HOURS:
60275.43 TOTAL MEGAWATT HOURS THIS YEAR:
792.23 TOTAL MEGAWATT HOURS:
74019.77
- 3. Unplanned Shutdowns There were five unplanned shutdowns this year. They are summarized below in Table 3.1:
TABLE 3.1
SUMMARY
OF UNPLANNED SHUTDOWNS Date Description 1/23/2023 Reactor shutdown due to helium leak in the Bay 2 insert, which was addressed with Facility Modification FM-III-23-1 3/27/2023 An automatic SCRAM was caused by a Bay 4 door limit switch making intermittent contact and triggering the External #1 interlock.
7/17/2023 An automatic SCRAM was caused by a Bay 2 door limit switch making intermittent contact and triggering the External #2 interlock.
7/18/2023 A manual SCRAM was caused by an accidental push of the Reactor Room SCRAM button by a member of a tour group.
9/29/2023 An automatic SCRAM was triggered by the NM-1000 when reactor power exceeded the high-power SCRAM setpoint (at 900 kW) during a thermal power calibration. A subsequent calibration was performed at a lower power level.
- 4. Major Preventative and Corrective Maintenance Operations Having Safety Significance 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 conducted in July and was extended through September and included the issuance of License Amendment No. 10. During the shutdown, inspection of fuel elements and control rods was performed in accordance with the UCD/MNRC Technical specifications. One fuel element was found to have gross pitting and was reported to the NRC in a special report in accordance with Technical Specification 6.7.2.
A new core configuration was established after the maintenance shutdown. The new configuration removed fuel elements from positions in the outer ring of the core (G-Ring) where the minimum shim plate clearance required by the Thermal-Hydraulic Analysis in the facilitys Safety Analysis Report was not present. One position was left empty (water-filled). The others were replaced with graphite elements.
4 Parametric values noted during testing were as follows:
Control Rod Worth:
Transient Rod:
$2.10 Regulating Rod:
$2.76 Shim 1:
$2.34 Shim 2:
$2.87 Shim 3:
$3.03 Shim 4:
$2.26 Control Rod Drop Times (in Seconds):
Transient Rod:
0.36 Regulating Rod:
0.39 Shim 1:
0.40 Shim 2:
0.37 Shim 3:
0.40 Shim 4:
0.39 Shutdown Margin: $7.10 Nuclear instrument calorimetric calibrations were performed during the annual reactor maintenance period. Adjustments were made to the NPP-1000 detector to match the measured calorimetric power.
Major non-routine maintenance items related to systems associated with reactor safety are described below in the Table 4.1:
TABLE 4.1
SUMMARY
OF MAJOR NON-ROUTINE MAINTENANCE WITH SAFETY SIGNIFICANCE Date Description 1/23/23 Isolated the Bay 2 insert helium supply line from the rest of the helium supply and installed a dedicated helium supply after the Bay 2 insert began to leak.
4/21/23 Cleaned and lubricated the Bay 3 External #2 limit switchs mechanical section.
5/31/23 The mechanical section of the External #1 limit switch on the closed side of the Bay 4 shutter was replaced.
7/17/23 Adjusted the Bay 2 east-side Door External #2 limit switch.
9/11/23 Measured the spacing between the shim plates and the fuel elements in the G-Ring of the core.
9/25/23 Reconfigured the core in accordance with License Amendment No. 10 and analyzed for maximum allowed power, maximum individual element power, and peak power location.
10/27/23 Replaced the control rods electromagnet power supply.
5
- 5. Changes to the Facility, Procedures, and Experiments Table 5.1 provides a brief summary of changes in the facility or in procedures and of tests and experiments carried out pursuant to 10 CFR 50.59.
TABLE 5.1
SUMMARY
OF CHANGES Date Description 1/23/2023 The Bay 2 Reflector Insert developed a helium leak and was isolated from the helium supply manifold and changed to an independent helium supply to preclude depressurization of other systems. A 50.59 evaluation was performed. This change was classified as Facility Modification FM-III 23-01.
2/8/2023 The beam mask located directly behind the Bay 4 Beam Tube Cover Plate was removed (similar to the Bay 3 modification performed in 2021, FM-III 21-01). A 50.59 evaluation was performed.
This change was classified as Facility Modification FM-III 23-02.
2/9/2023 Surveillance frequencies of certain procedures were revised to match those found in the new Technical Specifications that accompanied the Renewed Facility Operating License. Two new surveillance items were added (Measuring the maximum reactivity insertion rate of the control rods annually, and cycling the valves and checking flow of the Core Reflooding System quarterly). A 50.59 screening was performed.
3/1/2023 The frequency of an additional control rod surveillance that is not required by the Technical Specifications was changed from semiannual to annual because it is less safe to performed this procedure outside of the annual maintenance shutdown period. A 50.59 screening was performed.
3/1/2023 MNRC Document 29 Revision 22, Radiation Safety Procedures, was created and approved. It included updates associated with the Renewed Facility Operating License and License Amendment No. 9.
3/29/2023 The procedure for the calibration of the demineralizer system inlet and outlet conductivity cells was changed to mitigate the risk of draining water from the primary system piping. A 50.59 screening was performed.
8/4/2023 A new core configuration was analyzed and implemented to address issues found during the annual shutdown and fuel inspection. Low source-level nuclear instrument readings and shim plate observations made during the reconfiguration precluded operation with this new core configuration. A 50.59 screening was performed.
8/11/2023 A license amendment was requested and approved by the NRC to allow for water-filled positions in the G-ring of the core as a result of discoveries during the annual shutdown that precluded the use of position L-01. A 50.59 evaluation was performed. This change was classified as Facility Modification FM-I 23-03.
9/20/2023 A new core configuration was analyzed and implemented in order to remove fuel elements from positions in the G-Ring of the core with insufficient clearance near the shim plates. A 50.59 evaluation was performed. This change was classified as FM-III 23-04.
9/30/2023 MNRC Document 29 Revision 23, Radiation Safety Procedures, was created and approved to make adjust to environmental monitoring locations in excess of those required by the Technical Specifications. A 50.59 screening was performed.
11/8/2023 MNRC Document 11 Revision 7, Fuel, was created and approved to update the document after the issuance of License Amendment No. 10.
6
- 6. 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:
6.1 Liquid Effluents No liquid effluents were released during 2023.
6.2 Airborne Effluents Ar-41 radioactivity discharged during 2023 is tabulated in Table 6.1 below.
TABLE 6.1 2023
SUMMARY
OF AIRBORNE EFFLUENTS MONTH TOTAL MEASURED Ar-41 RELEASED (Ci)
JAN 2.44 FEB 0.12 MAR 2.27 APR 2.28 MAY 2.78 JUN 3.85 JUL 1.83 AUG 0.09 SEP 0.00 OCT 2.06 NOV 2.33 DEC 1.67 TOT 21.71 AVG 1.81 Per MNRC technical specification 3.7.2, the facility shall not effluence greater than 118 Ci of Ar-41 per year, which corresponds to 5 mrem dose to the public. MNRC released a total of 21.71 Ci of Ar-41 in 2023, corresponding to a dose to the public of 0.92 mrem. Based on MNRC SAR appendix A, MNRC cannot exceed any applicable effluence concentration limits during 1 MW reactor operations. No other radionuclides were discharged as air effluence by MNRC in 2023.
7 6.3 Solid Waste No solid radioactive waste was shipped this year.
- 7. Radiation Exposure Radiation exposure received by facility operations personnel, facility users, and visitors during 2023 is summarized in Table 7.1 below.
TABLE 7.1 2023
SUMMARY
OF PERSONNEL RADIATION EXPOSURES NUMBER OF INDIVIDUALS AVERAGE TEDE PER INDIVIDUAL (mrem)
GREATEST INDIVIDUAL TEDE (mrem)
AVERAGE EXTREMITY (mrem)
GREATEST EXTREMITY (mrem)
FACILITY PERSONNEL 12 58 197 177 875 FACILITY USERS 31
<1.0 1.0 VISITORS 1093
<1.0 3.0
- Extremity monitoring was not required.
8
- 8. Radiation Levels and Levels of Contamination Radiation levels and levels of contamination observed during routine surveys performed at the MNRC during 2023 are summarized in Table 8.1 below.
TABLE 8.1 2023
SUMMARY
OF RADIATION LEVELS AND CONTAMINATION LEVELS DURING ROUTINE SURVEYS AVERAGE(4)
HIGHEST(5)
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 (I/S Fence)
<0.1
<0.1
<5000(1)
<5000(1)
EQUIPMENT RM 0.5 80
<800(2)
<800(2)
DEMINERALIZER AREA 10.2 220
<800(2)
<800(2)
REACTOR RM 2.4 430
<800(2)
<800(2)
RADIOGRAPHY BAYS (3) 6.0 170
<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.
9
- 9. Environmental Surveys Environmental surveys performed outside of the MNRC during 2023 are summarized in Tables 9.1 &
9.2 below. The environmental survey program is described in the MNRC Facility Safety Analysis Report.
TABLE 9.1 2023
SUMMARY
OF ENVIRONMENTAL TLD RESULTS (WITH NATURAL BACKGROUND(1) SUBTRACTED)
AVERAGE (mrem)
HIGHEST (mrem)
ON SITE (SITES 50 - 61 & 65-71) 49 64 (1) Natural background assumed to be the off park (Sites 42) average of 8 mrem.
TABLE 9.2 2023
SUMMARY
OF RADIOACTIVITY IN WELL WATER ALPHA BETA TRITIUM Cs-137 (pCi/l)
(pCi/l)
(pCi/l)
(pCi/l)
AVERAGE
<MDA 2.12
<MDA
<MDA HIGHEST
<MDA 3.15
<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 2.41 5.08 Beta 0.900 1.29 Tritium 230 300 Cs-137 8.85 26.0