IR 05000313/2021002
| ML21217A332 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 08/09/2021 |
| From: | John Dixon NRC/RGN-IV/DRP |
| To: | Dinelli J Entergy Operations |
| References | |
| IR 2021002 | |
| Download: ML21217A332 (27) | |
Text
SUBJECT:
ARKANSAS NUCLEAR ONE - INTEGRATED INSPECTION REPORT 05000313/2021002 AND 05000368/2021002
Dear Mr. Dinelli:
On June 30, 2021, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at Arkansas Nuclear One. On July 1, 2021, the NRC inspectors discussed the results of this inspection with Mr. J. Sullivan, General Manager Plant Operations, and other members of your staff. The results of this inspection are documented in the enclosed report.
One finding of very low safety significance (Green) is documented in this report. This finding involved a violation of NRC requirements. We are treating this violation as a non-cited violation (NCV) consistent with Section 2.3.2 of the Enforcement Policy.
If you contest the violation or the significance of the violation documented in this inspection report, you should provide a response within 30 days of the date of this inspection report, with the basis for your denial, to the U.S. Nuclear Regulatory Commission, ATTN: Document Control Desk, Washington, DC 20555-0001; with copies to the Regional Administrator, Region IV; the Director, Office of Enforcement; and the NRC Resident Inspector at Arkansas Nuclear One.
If you disagree with a cross-cutting aspect assignment in this report, you should provide a response within 30 days of the date of this inspection report, with the basis for your disagreement, to the U.S. Nuclear Regulatory Commission, ATTN: Document Control Desk, Washington, DC 20555-0001; with copies to the Regional Administrator, Region IV; and the NRC Resident Inspector at Arkansas Nuclear One.
This letter, its enclosure, and your response (if any) will be made available for public inspection and copying at http://www.nrc.gov/reading-rm/adams.html and at the NRC Public Document August 9, 2021 Room in accordance with Title 10 of the Code of Federal Regulations 2.390, Public Inspections, Exemptions, Requests for Withholding.
Sincerely, John L. Dixon, Jr., Chief Reactor Projects Branch D Division of Reactor Projects Docket Nos. 05000313 and 05000368 License Nos. DPR-51 and NPF-6
Enclosure:
As stated w/Attachment: Momentary Loss of Power to 4160 Vac bus A2 Event
Inspection Report
Docket Numbers:
05000313 and 05000368
License Numbers:
Report Numbers:
05000313/2021002 and 05000368/2021002
Enterprise Identifier:
I-2021-002-0109
Licensee:
Entergy Operations, Inc.
Facility:
Arkansas Nuclear One
Location:
Russellville, AR
Inspection Dates:
April 1, 2021, to June 30, 2021
Inspectors:
B. Baca, Health Physicist
N. Brown, Resident Inspector
R. Bywater, Senior Resident Inspector
T. DeBey, Resident Inspector
J. Drake, Senior Reactor Inspector
J. O'Donnell, Senior Health Physicist
A. Patz, Senior Resident Inspector
Approved By:
John L. Dixon, Jr., Chief
Reactor Projects Branch D
Division of Reactor Projects
SUMMARY
The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees performance by conducting an integrated inspection at Arkansas Nuclear One, in accordance with the Reactor Oversight Process. The Reactor Oversight Process is the NRCs program for overseeing the safe operation of commercial nuclear power reactors. Refer to https://www.nrc.gov/reactors/operating/oversight.html for more information.
List of Findings and Violations
Failure to Provide Appropriate Procedures for 4160 Vac Switchgear Inspections Cornerstone Significance Cross-Cutting Aspect Report Section Initiating Events Green NCV 05000313/2021002-01 Open/Closed
[H.9] - Training 71111.12 The inspectors identified a Green finding and associated non-cited violation of Arkansas Nuclear One, Unit 1, Technical Specifications 5.4.1.a, for the licensees failure to have an adequate maintenance procedure as required by Regulatory Guide 1.33, Quality Assurance Program Requirements, Revision 2, February 1978. Regulatory Guide 1.33, Appendix A,
Section 9, Procedures for Performing Maintenance, requires, in part, that maintenance should be properly preplanned and performed in accordance with written procedures, documented instructions, or drawings appropriate to the circumstances. Specifically,
Procedure OP-1416.002, U1 A2 Bus Switchgear Inspection, Revision 21, did not adequately provide the level of detail required, including qualitative or quantitative acceptance criteria, to ensure correct alignment of potential transformer contacts. A manual trip of Arkansas Nuclear One, Unit 1, from full power was caused by a bent potential transformer contact in the 4160 Vac A2 bus that was not identified during previous inspections.
Additional Tracking Items
Type Issue Number Title Report Section Status LER 05000313/2021-001-00 Reactor Manual Trip due to Temporary Loss of Non-Vital 4160 Volt Bus 71153 Closed
PLANT STATUS
Unit 1 entered the inspection period at 90 percent power and then shut down for a planned refueling outage between April 9 and May 11, 2021. Unit 1 operated at or near full power for the remainder of the inspection period.
Unit 2 operated at or near full power for the duration of the inspection period.
INSPECTION SCOPES
Inspections were conducted using the appropriate portions of the inspection procedures (IPs) in effect at the beginning of the inspection unless otherwise noted. Currently approved IPs with their attached revision histories are located on the public website at http://www.nrc.gov/reading-rm/doc-collections/insp-manual/inspection-procedure/index.html. Samples were declared complete when the IP requirements most appropriate to the inspection activity were met consistent with Inspection Manual Chapter (IMC) 2515, Light-Water Reactor Inspection Program - Operations Phase. The inspectors reviewed selected procedures and records, observed activities, and interviewed personnel to assess licensee performance and compliance with Commission rules and regulations, license conditions, site procedures, and standards.
Starting on March 20, 2020, in response to the National Emergency declared by the President of the United States on the public health risks of the coronavirus (COVID-19), resident and regional inspectors were directed to begin telework and to remotely access licensee information using available technology. During this time, the resident inspectors performed periodic site visits each week, increasing the amount of time on site as local COVID-19 conditions permitted.
As part of their onsite activities, resident inspectors conducted plant status activities as described in IMC 2515, Appendix D; observed risk significant activities; and completed on site portions of IPs. In addition, resident and regional baseline inspections were evaluated to determine if all or a portion of the objectives and requirements stated in the IP could be performed remotely. If the inspections could be performed remotely, they were conducted per the applicable IP. In some cases, portions of an IP were completed remotely and on site. The inspections documented below met the objectives and requirements for completion of the IP.
REACTOR SAFETY
71111.01 - Adverse Weather Protection
Impending Severe Weather Sample (IP Section 03.02) (1 Sample)
- (1) The inspectors evaluated the adequacy of the overall preparations to protect risk-significant systems from a severe thunderstorm warning on June 21, 2021.
71111.04 - Equipment Alignment
Partial Walkdown Sample (IP Section 03.01) (3 Samples)
The inspectors evaluated system configurations during partial walkdowns of the following systems/trains:
- (1) Unit 1 emergency diesel generator 1 during Unit 1 emergency diesel generator 2 outage on May 20, 2021
- (2) Unit 1 service water loop 1 during Unit 1 emergency diesel generator 2 outage on June 9, 2021
- (3) Unit 2 emergency diesel generator 2 during Unit 2 emergency diesel generator 1 outage on June 30, 2021
71111.05 - Fire Protection
Fire Area Walkdown and Inspection Sample (IP Section 03.01) (4 Samples)
The inspectors evaluated the implementation of the fire protection program by conducting a walkdown and performing a review to verify program compliance, equipment functionality, material condition, and operational readiness of the following fire areas:
- (1) Unit 2 post-accident sampling building, Fire Zone PASS building, on April 1, 2021
- (2) Unit 2 turbine-driven emergency feedwater pump A room, Fire Zone 2024, on May 21, 2021
- (3) Unit 1 intake structure, Fire Area N, on June 21, 2021
- (4) Unit 2 intake structure, Fire Area OO, on June 30, 2021
71111.08P - Inservice Inspection Activities (PWR) PWR Inservice Inspection Activities Sample (IP Section 03.01)
- (1) The inspectors verified that the Unit 1 reactor coolant system boundary, steam generator tubes, reactor vessel internals, risk-significant piping system boundaries, and containment boundary are appropriately monitored for degradation and that repairs and replacements were appropriately fabricated, examined and accepted by reviewing the following activities from March 22 to May 4, 2021:
03.01.a - Nondestructive Examination and Welding Activities
Ultrasonic Examination a. Containment Sump, P-66 IWE CS Sleeve to Flued Head b. Containment Sump, P-67 IWE CS Sleeve to Flued Head c. Containment Sump, P-68 IWE CS Sleeve to Flued Head d. Oily Waste Separator, OW-117-201, 6-inch Buried Pipe e. Service Water, MIC-I (HBD-2-18"), straight pipe
Visual Examination a. Containment, P-66, Reactor Building Sump Recirc Penetration Type VII b. Containment, P-67, Reactor Building Sump Recirc Penetration Type VII c. Containment, P-68, Reactor Building Sump Recirc Penetration Type VII
The inspector reviewed the weld package for repairs on the main feedwater system for valve FW-2837, welds FW-1, FW-2, FW-3, FW-4, FW-5.
03.01.b - Pressurized-Water Reactor Vessel Upper Head Penetration Examination Activities
The inspector reviewed the NDE report for the Reactor Vessel Upper Head Penetration examination activities which consisted of an ultrasonic examination of all CRDM nozzles and a demonstrated volumetric leak path assessment of all J-groove welds and supplemental eddy current examination of 35 CRDM nozzle inside surfaces.
03.01.c - Pressurized-Water Reactor Boric Acid Corrosion Control Activities
The following boric acid evaluations and condition reports were reviewed:
a. CR-ANO-1-2018-01078, CR-ANO-1-2019-02272, CR-ANO-1-2020-01226, CR-ANO-1-2020-01229, CR-ANO-1-2020-01377 03.01.d - Pressurized-Water Reactor Steam Generator Tube Examination Activities
100 percent full length inspection of all tubes with bobbin coil probe
X-Probe and bobbin probe inspection of the tubes surrounding each tie rod to evaluate tie rod bowing Problem Identification and Resolution review of Inservice items The inspector evaluated a sample of 34 condition reports associated with inservice inspection activities. No findings or violations of more than minor significance were identified.
71111.11Q - Licensed Operator Requalification Program and Licensed Operator Performance
Licensed Operator Performance in the Actual Plant/Main Control Room (IP Section 03.01) (1 Sample)
- (1) The inspectors observed and evaluated licensed operator performance in the Unit 1 control room during plant cooldown, depressurization, and transfer to shutdown cooling in preparation for Refueling Outage 29 on April 12, 2021.
Licensed Operator Requalification Training/Examinations (IP Section 03.02) (1 Sample)
- (1) The inspectors observed and evaluated the Unit 2 licensed operator simulator evaluation scenario on June 15, 2021.
71111.12 - Maintenance Effectiveness
Maintenance Effectiveness (IP Section 03.01) (1 Sample)
The inspectors evaluated the effectiveness of maintenance to ensure the following structures, systems, and components (SSCs) remain capable of performing their intended function:
- (1) Alignment checks of potential transformer contacts in 4160 Vac switchgear on June 7, 2021
Quality Control (IP Section 03.02) (1 Sample)
The inspectors evaluated the effectiveness of maintenance and quality control activities to ensure the following SSC remains capable of performing its intended function:
- (1) Quality control for stored fuel oil/preventive maintenance strategy of diverse and flexible mitigation capability response equipment on June 29, 2021
71111.13 - Maintenance Risk Assessments and Emergent Work Control
Risk Assessment and Management Sample (IP Section 03.01) (3 Samples)
The inspectors evaluated the accuracy and completeness of risk assessments for the following planned and emergent work activities to ensure configuration changes and appropriate work controls were addressed:
- (1) Unit 1 Refueling Outage 29 plan on April 6, 2021
- (2) Unit 1 planned entry into lowered reactor coolant system inventory on April 29, 2021
- (3) Unit 1 and Unit 2 work controls for spurious opening of 161 kV switchyard breaker B1218 during alternate AC diesel generator maintenance outage on June 24, 2021
71111.15 - Operability Determinations and Functionality Assessments
Operability Determination or Functionality Assessment (IP Section 03.01) (5 Samples)
The inspectors evaluated the licensee's justifications and actions associated with the following operability determinations and functionality assessments:
- (1) Unit 1 emergency feedwater initiation and control channel B steam generator B pressure transmitter containment isolation valve MS-6843 seat leakage operability determination on April 1, 2021
- (2) Unit 2 Loop 2 service water pinhole leak operability determination on May 7, 2021
- (3) Unit 1 high pressure injection system, all flow transmitters improper calibration/recalibration operability determination, on May 25, 2021
- (4) Common unit meteorological tower functionality assessment and availability of alternate meteorological data on June 1, 2021
- (5) Unit 1 borated water storage tank internal inspection operability determination on June 3, 2021
71111.18 - Plant Modifications
Temporary Modifications and/or Permanent Modifications (IP Section 03.01 and/or 03.02) (1 Sample)
The inspectors evaluated the following temporary or permanent modifications:
- (1) Unit 1 emergency diesel room exhaust fan replacements on May 24, 2021
71111.19 - Post-Maintenance Testing
Post-Maintenance Test Sample (IP Section 03.01) (2 Samples)
The inspectors evaluated the following post-maintenance test activities to verify system operability and functionality:
- (1) Unit 1 service water pump P-4C post-maintenance testing after pump shaft replacement on June 29, 2021
- (2) Common unit diesel-driven fire pump P-6B post-maintenance testing after semi-annual inspection and preventive maintenance on June 30, 2021
71111.20 - Refueling and Other Outage Activities
Refueling/Other Outage Sample (IP Section 03.01) (1 Sample)
- (1) The inspectors evaluated Unit 1 Refueling Outage 29 activities from April 9 to May 11, 2021.
71111.22 - Surveillance Testing
The inspectors evaluated the following surveillance tests:
Surveillance Tests (other) (IP Section 03.01)
- (1) Unit 1 surveillance testing of five main steam safety valves on April 15, 2021
- (2) Unit 2 surveillance testing of moderator temperature coefficient on April 22, 2021
- (3) Unit 1 surveillance testing of emergency diesel generator 1 on May 3, 2021
- (4) Unit 1 core power distribution surveillance testing after refueling outage on May 12, 2021
- (5) Unit 1 service water system surveillance testing on May 17, 2021
- (6) Unit 1 surveillance testing of boron concentration in primary coolant water on May 19, 2021
Containment Isolation Valve Testing (IP Section 03.01) (1 Sample)
- (1) Unit 1 local leak rate testing of reactor building sump isolation valve CV-4400 on April 29, 2021
FLEX Testing (IP Section 03.02) (1 Sample)
- (1) Annual surveillance testing of FLEX portable pumps and generators on May 11,
RADIATION SAFETY
71124.01 - Radiological Hazard Assessment and Exposure Controls
Radiological Hazard Assessment (IP Section 03.01) (1 Sample)
- (1) The inspectors evaluated how the licensee identifies the magnitude and extent of radiation levels and the concentrations and quantities of radioactive materials and how the licensee assesses radiological hazards.
Instructions to Workers (IP Section 03.02) (1 Sample)
The inspectors evaluated instructions to workers including radiation work permits (RWP)used to access high radiation areas.
- (1) The inspectors reviewed the following radiation work permit (RWP) packages, electronic alarming dosimeter condition reports, and labeling of containers:
RWP 2021-1471, "1R29 Reactor Pressure Vessel Closure Head - Volumetric and Surface Exams," Revision 0
RWP 2021-1442, "1R29 Steam Generator Primary Side Eddy Current Inspection and Repair Activities," Revision 0
RWP 2021-1406, "1R29 Radwaste Processing and Shipping," Revision 0
CR-ANO-1-2020-01134 - Worker received an unanticipated dose rate alarm and took appropriate actions
CR-ANO-C-2020-01365 - Worker received a dose alarm during Unit 2 under vessel walk down; the alarm was determined to be instrument malfunction
Yellow radioactive material trash bags [various areas in the Radiologically Controlled Area]
Two Intermodal containers of Dry Active Waste [ESUU300322 and ESUU300545]
Storage box (EQ-216) containing tensioner cables on the Reactor Building -
404-foot elevation
Contamination and Radioactive Material Control (IP Section 03.03) (2 Samples)
The inspectors evaluated licensee processes for monitoring and controlling contamination and radioactive material:
- (1) Observed licensee surveys of potentially contaminated material leaving the radiologically controlled area
- (2) Observed workers exiting the Unit 1 containment building during a refueling outage
Radiological Hazards Control and Work Coverage (IP Section 03.04) (3 Samples)
The inspectors evaluated in-plant radiological conditions during facility walkdowns and observation of radiological work activities. The inspectors reviewed the following radiological work packages for activities within the Unit 1 containment building:
- (1) RWP 2021-1442, "1R29 Steam Generator Primary Side Eddy Current Inspection and Repair Activities," Revision 0, specifically for installation of nozzle dams and eddy current equipment
- (2) RWP 2021-1471, "1R29 Reactor Pressure Vessel Closure Head - Volumetric and Surface Exams," Revision 0, specifically for under head inspection activities
- (3) The inspectors also reviewed the following radiological work package for activities associated with processing and handling of radioactive waste: RWP 2021-1406, "1R29 Radwaste Processing and Shipping," Revision 0, specifically for Shipment RSR-21-038 High Radiation Area and Very High Radiation Area Controls (IP Section 03.05) (5 Samples)
The inspectors evaluated licensee controls of the following High Radiation Areas and Very High Radiation Areas:
- (1) In-Core Tunnel was controlled as a Very High Radiation Area on the Unit 1 Containment Building - 335-foot elevation
- (2) Access to the In-Core Tunnel was controlled as a Technical Specification (TS) High Radiation Area (HRA) on the Unit 1 Containment Building - 335-foot elevation
- (3) Reactor Vessel Closure Head stand was controlled as a TS HRA using the flashing lights control option on the Unit 1 Containment Building - 404-foot elevation
- (4) The T-11 Tank Room was controlled as a TS HRA in the Unit 1 Auxiliary Building - 317-foot elevation
- (5) The F3A/B Filter Room was controlled as a TS HRA in the Unit 1 Auxiliary Building - 335-foot elevation Radiation Worker Performance and Radiation Protection Technician Proficiency (IP
Section 03.06) (1 Sample)
- (1) The inspectors evaluated radiation worker and radiation protection technician performance as it pertains to radiation protection requirements.
71124.03 - In-Plant Airborne Radioactivity Control and Mitigation
Permanent Ventilation Systems (IP Section 03.01) (2 Samples)
The inspectors evaluated the configuration of the following permanently installed ventilation systems:
- (1) Unit 1 control room emergency ventilation system
- (2) Emergency operation facility ventilation system
Temporary Ventilation Systems (IP Section 03.02) (2 Samples)
The inspectors evaluated the configuration of the following temporary ventilation systems:
- (1) Unit 1 Reactor Containment Building, 426-foot elevation - Reactor head ventilation and Alpha Level 2 decontamination tent ventilation
- (2) Unit 1 Reactor Containment Building, 335-foot elevation - Steam Generator D-ring eddy current testing
Use of Respiratory Protection Devices (IP Section 03.03) (1 Sample)
- (1) The inspectors evaluated the licensees use of respiratory protection devices during Unit 1 refueling outage work activities.
Self-Contained Breathing Apparatus for Emergency Use (IP Section 03.04) (1 Sample)
- (1) The inspectors evaluated the licensees use and maintenance of self-contained breathing apparatuses.
OTHER ACTIVITIES - BASELINE
===71151 - Performance Indicator Verification The inspectors verified licensee performance indicators submittals listed below:
MS05: Safety System Functional Failures (SSFFs) Sample (IP Section 02.04)===
- (1) Unit 1 (April 1, 2020 through March 31, 2021)
- (2) Unit 2 (April 1, 2020 through March 31, 2021)
BI01: Reactor Coolant System (RCS) Specific Activity Sample (IP Section 02.10) (2 Samples)
- (1) Unit 1 (April 1, 2020 through March 31, 2021)
- (2) Unit 2 (April 1, 2020 through March 31, 2021)
BI02: RCS Leak Rate Sample (IP Section 02.11) (2 Samples)
- (1) Unit 1 (April 1, 2020 through March 31, 2021)
- (2) Unit 2 (April 1, 2020 through March 31, 2021)
OR01: Occupational Exposure Control Effectiveness Sample (IP Section 02.15) (1 Sample)
- (1) Unit 1 and Unit 2 (January 1, 2020 through December 31, 2020)
PR01: Radiological Effluent Technical Specifications/Offsite Dose Calculation Manual Radiological Effluent Occurrences (RETS/ODCM) Radiological Effluent Occurrences Sample (IP Section 02.16) (1 Sample)
- (1) Unit 1 and Unit 2 (January 1, 2020 through December 31, 2020)
71153 - Follow Up of Events and Notices of Enforcement Discretion Event Report (IP Section 03.02)
The inspectors evaluated the following licensee event reports (LERs):
- (1) LER 05000313/2021-001-00, Reactor Manual Trip due to Temporary Loss of Non-Vital 4160 Volt Bus (ADAMS Accession No. ML21133A020). The inspection conclusions associated with this LER are documented in this report as Non-Cited Violation 05000313/2021002-01.
INSPECTION RESULTS
Failure to Provide Appropriate Procedures for 4160 Vac Switchgear Inspections Cornerstone Significance Cross-Cutting Aspect Report Section Initiating Events Green NCV 05000313/2021002-01 Open/Closed
[H.9] - Training 71111.12 The inspectors identified a Green finding and associated non-cited violation of Arkansas Nuclear One, Unit 1, Technical Specifications 5.4.1.a, for the licensees failure to have an adequate maintenance procedure as required by Regulatory Guide 1.33, Quality Assurance Program Requirements, Revision 2, February 1978. Regulatory Guide 1.33, Appendix A, Section 9, Procedures for Performing Maintenance, requires, in part, that maintenance should be properly preplanned and performed in accordance with written procedures, documented instructions, or drawings appropriate to the circumstances. Specifically, Procedure OP-1416.002, U1 A2 Bus Switchgear Inspection, Revision 21, did not adequately provide the level of detail required, including qualitative or quantitative acceptance criteria, to ensure correct alignment of potential transformer contacts. A manual trip of Arkansas Nuclear One, Unit 1, from full power was caused by a bent potential transformer contact in the 4160 Vac A2 bus that was not identified during previous inspections.
Description:
On March 14, 2021, while operating at full power, the Arkansas Nuclear One (ANO) Unit 1 reactor experienced a loss of power to the non-safety-related 4160 Vac bus A2, which feeds safety-related 4160 Vac bus A4. Reactor operators manually tripped the reactor as required by their procedures. Emergency diesel generator B automatically started and provided power to the A4 bus. The licensees adverse condition analysis determined that a bent contact in the A2 bus potential transformer drawer resulted in contact misalignment, loss of electrical continuity, and loss of power to the A2 bus. The licensee concluded the contact most likely became bent during refurbishment of the A2 bus in 2013. The inspectors reviewed the A2 bus maintenance records and found that the licensee performed A2 bus potential transformer drawer contact alignment inspections using Procedure OP-1416.002 in 2013, 2016, and 2019. Each of these inspections documented satisfactory alignment. The technique used in the procedure to check contact alignment was a contact wipe check using Mobil 28 grease. The inspectors determined that Procedure OP-1416.002 was inadequate because it did not provide instructions for how to perform the wipe check and did not contain quantitative or qualitative acceptance criteria for wipe check results. The procedure had a table with entries stating, Contact wiped using Mobil 28 grease, and, Ensure proper contact wipe using Mobil 28 grease. Acceptance criteria specified were: Sat and Unsat. The procedure was inadequate to identify the bent contact in the A2 bus potential transformer drawer.
The inspectors also examined the licensees procedures for inspecting potential transformer contact alignment in all the other seven Unit 1 and Unit 2 4160 Vac buses and found similar inadequate inspection acceptance criteria. Additionally, the inspectors identified several examples where the procedures were not written consistently using language required by Procedure CPG-001, ANO Procedure Writers Guide, Revision 2. For example, the procedures inconsistently used action words such as verify, check, and, ensure, which have different specific meanings. Also, although the potential transformer drawers for the eight ANO Unit 1 and Unit 2 4160 Vac buses are identical General Electric devices, the licensees inspection procedures varied considerably in format and content among them.
Corrective Actions: The licensee cleaned and realigned the potential transformer contacts and restored the A2 bus to normal operation. A condition report was written with corrective actions to perform an adverse condition analysis of the event, review and revise inspection procedures, and complete extent of condition inspections of potential transformer contacts in the other buses. The Unit 1 inspections were completed in the spring 2021 refueling outage and the Unit 2 inspections were scheduled to be performed in the fall 2021 refueling outage.
Corrective Action References: Condition Reports CR-ANO-1-2021-00457, CR-ANO-1-2021-00490, CR-ANO-1-2021-00491, and CR-ANO-2-2021-00709
Performance Assessment:
Performance Deficiency: The inspectors determined that the failure to have an adequate maintenance procedure to correctly perform inspection of potential transformer contact alignment in 4160 Vac bus A2 in accordance with Technical Specification 5.4.1.a and Regulatory Guide 1.33 was a performance deficiency.
Screening: The inspectors determined the performance deficiency was more than minor because it was associated with the procedure quality attribute of the Initiating Events cornerstone and adversely affected the cornerstone objective to limit the likelihood of events that upset plant stability and challenge critical safety functions during shutdown as well as power operations. Specifically, Procedure OP-1416.002, U1 A2 Bus Switchgear Inspection, Revision 21, did not adequately provide the level of detail required, including qualitative or quantitative acceptance criteria, to ensure correct alignment of potential transformer contacts.
A manual trip of ANO Unit 1 from full power was caused by a bent potential transformer contact in the 4160 Vac A2 bus that was not identified during previous inspections.
Significance: The inspectors assessed the significance of the finding using Appendix A, The Significance Determination Process (SDP) for Findings At-Power. A detailed risk evaluation was required for this finding because it was a condition that caused a reactor trip and the loss of mitigation equipment (auxiliary feedwater pump P-75, powered from the A2 bus). A senior reactor analyst performed the detailed risk assessment and determined that the estimated increase in core damage frequency from internal events for this performance deficiency was 3.5E-7/year. The analyst determined the risk contribution due to external events was insignificant. There was no significant contribution to large early release frequency.
Therefore, the finding was of very low safety significance (Green). The full Detailed Risk Assessment is provided as an attachment to this report.
Cross-Cutting Aspect: H.9 - Training: The organization provides training and ensures knowledge transfer to maintain a knowledgeable, technically competent workforce and instill nuclear safety values. Specifically, knowledge transfer and knowledge retention strategies were not applied to ensure technicians were technically competent in the performance of wipe checks of potential transformer contacts while using inadequate inspection procedures.
Enforcement:
Violation: Technical Specification 5.4.1.a for Unit 1 requires, in part, that written procedures be established, implemented, and maintained covering the applicable procedures recommended in Appendix A to Regulatory Guide 1.33, Quality Assurance Program Requirements, Revision 2, February 1978. Regulatory Guide 1.33, Appendix A, Section 9, Procedures for Performing Maintenance, requires, in part, that maintenance should be properly preplanned and performed in accordance with written procedures, documented instructions, or drawings appropriate to the circumstances.
Contrary to the above, prior to March 14, 2021, the licensee failed to create written procedures, documented instructions, or drawings appropriate to the circumstances to perform inspection of potential transformer contact alignment in 4160 Vac buses.
Specifically, the licensee did not provide an adequate level of detail, including qualitative or quantitative acceptance criteria, in Procedure OP-1416.002, Unit 1 A2 Bus Inspection, Revision 21, to ensure correct alignment of potential transformer contacts. A manual reactor trip of ANO Unit 1 from full power was caused by a bent potential transformer contact in the 4160 Vac A2 bus that was not identified during previous inspections.
Enforcement Action: This violation is being treated as a non-cited violation, consistent with Section 2.3.2 of the Enforcement Policy.
EXIT MEETINGS AND DEBRIEFS
The inspectors verified no proprietary information was retained or documented in this report.
On April 22, 2021, the inspectors presented the occupational radiation safety inspection results to Mr. J. Dinelli, Site Vice President, and other members of the licensee staff.
On May 5, 2021, the inspectors presented the ANO Unit 1 inservice inspection results to Mr. J. Dinelli, Site Vice President, and other members of the licensee staff.
On July 1, 2021, the inspectors presented the integrated inspection results to Mr. J. Sullivan, General Manager Plant Operations, and other members of the licensee staff.
DOCUMENTS REVIEWED
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Procedures
203.025
Natural Emergencies
Corrective Action
Documents
CR-ANO-
2-2021-00783, 2-2021-00785, 2-2021-00812, C-2021-01519
Drawings
M-217, Sheet 1
Emergency Diesel Generators Fuel Oil Storage
Drawings
M-217, Sheet 4
Emergency Diesel Generators K-4A/K-4B Starting Air
System
Procedures
OP-1104.029
Service Water and Auxiliary Cooling System
2
Procedures
OP-1104.036
Emergency Diesel Generator Operation Attachment A
Procedures
OP-2104.036
Emergency Diesel Generator Operations
Work Orders
WO 2933844, 52935896
Corrective Action
Documents
CR-ANO-
2-2021-1114, C-2021-0944, C-2021-0945, C-2021-0946
Drawings
FP-110, Sheet 1
Fire Zone Intake Structure
Drawings
Fire Zone Ground Floor Plan EL 354
Drawings
FP-2105, Sheet 1
Fire Zone Plan Below Grade EL 335-0
Drawings
Fire Zone Post Accident Sampling Facilities
Miscellaneous
Unit 2 Prefire Plans
Miscellaneous
Fire Hazards Analysis Arkansas Nuclear One - Unit 1 and
Unit 2
Miscellaneous
Unit 1 Prefire Plans
Procedures
Control of Combustibles
Calculations
CALC-20-E-0001-
EVALUATION OF 14-INCH SERVICE WATER PIPE WALL
THINNING, LINE HBD-14-14, MIC LOCATION 9
Calculations
CALC-88-E-0100-
Calculation for Unit 1 Intermediate Cooling Water
Calculations
CALC-ANO1-EP-
ANO-1 Steam Generator Secondary Side Integrity Plan
Corrective Action
Documents
CR-ANO-
1-2004-01230, 1-2008-02183, 1-2016-03851, 1-2018-01775,
1-2019-03062, 1-2021-00871, 1-2021-01090, 1-2021-01135,
1-2021-01456, 1-2021-01767, 1-2021-01768, 1-2021-01769,
1-2021-01770
Corrective Action
CR-ANO-
1-2021-00704, 1-2021-00705, 1-2021-00708, 1-2021-00883,
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Documents
Resulting from
Inspection
1-2021-01031, 1-2021-01201, 1-2021-01263, 1-2021-01370,
1-2021-01468, 2-2021-00754
Miscellaneous
R29 Reactor Vessel Head lnspection-BARK1
Miscellaneous
BARK1
Reactor Vessel Head lnspection Plan
Miscellaneous
WDI-PJF-344403-
EPP-001
Examination Program Plan for the Arkansas Nuclear One
Unit 1
Miscellaneous
WDI-PJF-344403-
EPP-001
Examination Program Plan for the Arkansas Nuclear One
Unit 1
Procedures
CEP-BAC-001
Boric Acid Corrosion Control (BACC) Program Plan
Procedures
CEP-CII-
003_308-1
Visual Examinations of Class MC Components
308
Procedures
CEP-NDE-0121
Reactor Vessel Upper Head (RVUH) Nozzle Penetration
Non-Visual Examination Guidelines
Procedures
CEP-NDE-0400
Ultrasonic Examination
Procedures
CEP-NDE-0407
Straight Beam Ultrasonic Examination of Bolts and Studs
(ASME XI)
Procedures
CEP-NDE-0423
Manual Ultrasonic Examination of Austenitic Piping Welds
(ASME XI)
Procedures
CEP-NDE-0901
VT-1 Examination
Procedures
CEP-NDE-0902
VT-2 Examination
Procedures
CEP-NDE-0903
VT-3 Examination
Procedures
CEP-NDE-0955
Visual Examination (VE) of Bare-Metal Surfaces
308
Procedures
CEP-WP-GWS-1
General Welding Standard ASME/ANSI
Procedures
Boric Acid Corrosion Control (BACC) Program
Procedures
SEP-ISI-ANO1-
101
Program Section For ASME Section XI, Division 1 ANO 1
Inservice Inspection Program
Work Orders
WO-ANO-
301122, 528933, 51511812, 52668905, 52914122
Corrective Action
Documents
CR-ANO-
C-2021-01182
Miscellaneous
Outage Risk Assessment Team Report
03/29/2021
Miscellaneous
SES-2-034
Unit 2 Dynamic Exam Scenario
Miscellaneous
SES-2-063
Unit 2 Dynamic Exam Scenario
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Procedures
OP-1102.010
Plant Shutdown and Cooldown
Procedures
OP-1104.004
Decay Heat Removal Operating Procedure
133
Corrective Action
Documents
CR-ANO-
1-2021-00490, 1-2021-00491, C-2019-00471, HQN-2015-
01089
Miscellaneous
CPG-001
Procedure Writers Guide
Miscellaneous
EPRI 1003089
Maintenance of General Electric Magne-Blast M26 and M36
Switchgear
10/2001
Miscellaneous
IPH1250/175DJ-
TCL
Installation and Operation Manual: High Performance
Industrial Pumping Module
11/2014
Miscellaneous
OMRG36864
Operators Manual 9.0L OEM Diesel Engines
03/07/2013
Miscellaneous
TDG971 0010
FLEX Portable Diesel Generator
Procedures
OP-1416.001
Unit 1 A1 Bus Switchgear Inspection
Procedures
OP-1416.002
Unit 1 A2 Bus Switchgear Inspection
Procedures
OP-1416.004
Unit 1 A4 Bus Switchgear Inspection
Procedures
OP-1416.008
Unit 1 A3 Bus Switchgear Inspection
Work Orders
Corrective Action
Documents
CR-ANO-
1-2021-00537, C-2021-01252
Miscellaneous
ANO Unit1 Operator Logs
04/29/2021
Miscellaneous
Outage Risk Assessment Team Review Comments
03/16/2021
Miscellaneous
ANO Unit 1 Outage Schedule
Procedures
1015.048
Shutdown Operations Protection Plan
Procedures
Shutdown Safety Management Program (SSMP)
Calculations
CALC-21-E-0003-
T-3 BWST Tank 1R29 NDE Review and Boric Acid
Corrosion rate
05/02/2021
Calculations
CALC-85-EQ-
0003-021
Corrective Action
Documents
CR-ANO-
1-2019-03062, 1-2021-00621, 1-2021-00641, 1-2021-01039,
1-2021-01090, 1-2021-01105, 1-2021-01106, 1-2021-01141,
1-2021-01150, 1-2021-01370, 2-2021-00739, C-2021-
01467, C-2021-01499, C-2021-01673
Drawings
M-206, Sheet 1
Steam Generator Secondary System
133
Miscellaneous
Arkansas Nuclear One Emergency Plan
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Miscellaneous
Unit 1 Narrative Log
06/01/2021
Miscellaneous
Unit 1 Shift Relief Sheet
04/01/2021
Miscellaneous
Engineering Review of NDE Prepared On T-3
05/02/2021
Miscellaneous
Unit 1 Online Rosemount EQ Transmitter Replacement
06/2020
Procedures
1903.011
Emergency Response/Notifications
Procedures
1904.002
Offsite Dose Projections
Procedures
Post-Maintenance Testing
Procedures
Operability Determination Process
Procedures
OP-1304.185
Unit 1 Green Channel High Pressure Injection Flow Inst Cal
Procedures
OP-1304.188
Unit 1 Red Channel High Pressure Injection Flow Inst Cal
Work Orders
WO 560988, 561566, 50235828, 52886069, 52914122
Corrective Action
Documents
CR-ANO-
1-2021-00679, 1-2021-00798, 1-2021-00892, 1-2021-01076,
1-2021-01118, 1-2021-01156, 1-2021-01283, 1-2021-01284,
1-2021-01340, 1-2021-01378, 1-2021-01386, 1-2021-01634,
1-2021-01647, 1-2021-01800, 1-2021-01818
71111.18
Miscellaneous
2476506
Failure Mode Analysis for CR-ANO-1-2021-01818
Miscellaneous
Replace Unit 1 EDG Room Ventilation Fans (VEF-
24A/B/C/D) With New Fans
Miscellaneous
Replace Unit 1 EDG Room Ventilation Fan VEF-24A
Miscellaneous
FCR-89796
Field Change Request to Update TDC747 0030 Which
Incorrectly Identifies the Direction of Rotation as CCW
Installation, Operation, Maintenance and Handling
Miscellaneous
50.59 Screening for ANO EDG Replacement Fans
Miscellaneous
TDC747 0030
Instructions for Curtiss Wright EDG Exhaust Fans
Procedures
OP-6030.210
Electrical Scheme Testing
Procedures
OP-6030.211
Motor Run Test
Work Orders
WO 27996, 527997, 527998, 527999, 562254, 552799
Corrective Action
Documents
CR-ANO-
1-2021-01523, 1-2021-01678
Procedures
1104.032
Fire Protection Systems
Procedures
OP-1104.029
Service Water and Aux Cooling System Attachment C
2
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Procedures
OP-1306.027
Unit 1 K-5 Diesel Fire Pump Engine Surveillance Inspection
Work Orders
WO 488847, 527996, 527997, 527998, 527999
Corrective Action
Documents
CR-ANO-
1-2017-00198, 1-2021-02078, C-2021-01252
Procedures
1015.036
Containment Building Closeout
Procedures
1015.048
Shutdown Operations Protection Plan
Procedures
1102.002
Plant Startup
115
Procedures
1102.008
Approach to Criticality
Procedures
1102.010
Plant Shutdown and Cooldown
Procedures
1102.016
Power Reduction and Plant Shutdown
Procedures
Fatigue Management Program
Procedures
Shutdown Safety Management Program
Procedures
PWR Startup Critical Predictions and Evaluation Process
Corrective Action
Documents
CR-ANO-
1-2019-02484, 1-2020-00202, 1-2021-00677, 1-2021-00697,
1-2021-01780, 1-2021-01951, 2-2008-01469, 2-2009-03483,
2-2020-02492
Drawings
M-213
Laundry Waste and Containment and Aux. Building Sump
Drainage
Miscellaneous
CALC-ANO1-NE-
21-00005
ANO-1 Cycle 30 BMAC Summary Report
Procedures
OP-1042.003
Radiochemistry Routine Surveillance Schedule and
Technical Specification Reporting
Procedures
OP-1104.036
Emergency Diesel Generator Operation
Procedures
OP-1302.005
Core Power Distribution for Physics Testing
Procedures
OP-1302.012
Periodic Core Power Distribution Testing
Procedures
OP-1305.018
Local Leak Rate Testing - Type C
Procedures
OP-1305.040
Service Water Full Flow Testing
Procedures
OP-1306.017
Unit 1 Main Steam Safety Valve Test
Procedures
OP-1607.001
Reactor Coolant System Sampling
Procedures
OP-2302.009
Moderator Temperature Coefficient at Power
Work Orders
WO 494948-04, 52901710-01, 52901711-01, 52901712-01,
2901831-01, 52902401-01, 52902483, 52931737-01
Corrective Action
CR-ANO-
1-2020-00776, 1-2020-00818, 1-2020-01134, 1-2021-00083,
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Documents
1-2021-00095, 1-2021-00832, 1-2021-01151, 2-2020-01509,
2-2020-01511, 2-2020-01714, 2-2020-02481, 2-2020-02917,
2-2021-00627, C-2020-01365, C-2020-01882, C-2020-
267, C-2021-00935, C-2021-00937, C-2021-01139
Miscellaneous
Annual Inventory of the Miscellaneous Material in the ANO
Spent Fuel Pools (SFPs)
08/18/2020
Procedures
Control of Non-Fuel Materials
Procedures
Radiation Worker Expectations
Procedures
Access Control for Radiologically Controlled Areas
Procedures
Radiological Control
Procedures
EN-RP-106-1
Radiological Survey Guidelines
Procedures
Radiation Protection Posting
Procedures
Radioactive Material Control
Procedures
Conduct of Radiation Protection
Radiation
Surveys
Air Samples
(ANO-AS-)
2821-0043, 041921-0242, 042021-0247, 042021-0248,
2021-0249, 042021-0250, 043020-0369
Radiation
Surveys
ANO-
20-01-00178, 20-07-00342, 21-04-00202, 21-04-00225, 21-
04-00226, 21-04-00228, 21-04-00786, 21-04-00826, 21-04-
00829, 21-04-00831, 21-04-00833, 21-04-00837, 21-04-
00856, 21-04-00865, 21-04-00868, 21-04-00870, 21-04-
00871, 21-04-00892, 21-04-00971
Radiation Work
Permits (RWPs)
20-2471
Perform Inspections on Unit 2 Reactor Head During 2R27
Radiation Work
Permits (RWPs)
20-2900
Emergent Minor Maintenance Activities During 2R27
Radiation Work
Permits (RWPs)
21-1054
Unit-1 Transfer Spent Resin to T-13 or 2T-13 Spent Resin
Storage Tanks; to Include T-13 to Train Bay Activities
Radiation Work
Permits (RWPs)
21-1406
1R29 Radwaste Processing and Shipping
Radiation Work
Permits (RWPs)
21-1442
1R29 Steam Generator (SG) Primary Side Eddy Current
Inspection and Repair Activities
Radiation Work
Permits (RWPs)
21-1454
1R29 Motor Operated Valves (MOV) and Air Operated
Valves (AOV) Activities
Radiation Work
21-1471
1R29 Reactor Pressure Vessel Closure Head - Volumetric
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Permits (RWPs)
and Surface Exams
Self-Assessments LO-ALO-2020-
00048
Radiation Safety - Hazard Assessment, Airborne Controls,
and Performance Indicators
2/09/2020
Calibration
Records
Unit 1 RCS Radiation Leak Detection System 18 Month
Calibration
2/12/2019
Calibration
Records
Calibration of Fuel Handling Area 2RX-9830 (SPING 7)
04/01/2021
Corrective Action
Documents
CR-ANO-
1-2019-04739, 2-2020-00573, C-2019-04031, C-2019-
04065, C-2019-04193, C-2020-01357, C-2020-01366
Corrective Action
Documents
CR-HQN-
2019-02415
Miscellaneous
TRI Air Testing Laboratory Report - Compressed Air/Gas
Quality Testing: Eagle Air (C-82A) on 08/01/2019;
01/28/2020; 07/28/2020; 01/27/2021; and 02/26/2021
Miscellaneous
TRI Air Testing Laboratory Report - Compressed Air/Gas
Quality Testing: BAUER (C-82C) on 01/28/2020;
07/28/2020; 01/28/2021
Miscellaneous
TRI Air Testing Laboratory Report - Compressed Air/Gas
Quality Testing: Unit 2 Breathing Air Compressor (2BA-
1009) on 10/21/2019 and 03/12/2020
Miscellaneous
Air Sample and Results Log from 03/27/2020 through
04/05/2021
Miscellaneous
1601.406
6.5 Breathing Air Analysis Sample Sheet - Dive
Compressor on: 11/06/2019; 02/25/2020; 03/15/2020;
06/01/2020; and 10/27/2020
Miscellaneous
1601.406
6.5 Breathing Air Analysis Sample Sheet - C-
2C (Burn Building) on: 11/08/2019; 12/26/2019;
01/16/2020; 03/28/2020; 04/30/2020; 05/21/2020;
06/04/2020; 08/13/2020; 09/22/2020; 10/27/2020; and
11/09/2020
Miscellaneous
1601.406
6.5 Breathing Air Analysis Sample Sheet - C-
2A (Warehouse 2) on: 12/26/2019; 02/11/2020; and
08/11/2020
Miscellaneous
1601.406
6.5 Breathing Air Analysis Sample Sheets -
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Inline Air: (2BA-1009) 03/09/2020; (1IA-191) 03/16/2020;
and (2IA-1090) 03/04/2020
Miscellaneous
Inspection and Maintenance of Respiratory Protection
Equipment, Attachment 9.1, Face Piece Inspection Log from
11/29/2019 through 12/01/2020
Miscellaneous
9.5
Annual Respiratory Protection Equipment Inventory and
Inspection
11/30/2020
Procedures
1001.008
Surveillance Frequency Control Program
Procedures
1601.406
Setup and Operation of Breathing Air Sampling Kits
Procedures
Air Sampling
Procedures
DOP Challenge Testing of HEPA Vacuums and Portable
Ventilation Units
Procedures
Operation and Maintenance of HEPA Vacuum Cleaners and
HEPA Ventilation Units
Procedures
Respiratory Protection Program
Procedures
Inspection and Maintenance of Respiratory Protection
Equipment
Procedures
Selection, Issue and Use of Respiratory Protection
Equipment
Procedures
Breathing Air
Self-Assessments LO-ALO-2020-
00048
Radiation Safety - Hazard Assessment, Airborne Controls
and Performance Indicators
2/09/2020
Work Orders
In-Place Testing of the Emergency Operations Facility
Filtration System
11/30/2018
Work Orders
In-Place Testing of the Unit 1 Control Room Filtration
System
04/22/2019
Work Orders
In-Place Testing of the Emergency Operations Facility
Filtration System
2/05/2020
Work Orders
In-Place Testing of the Unit 1 Control Room Filtration
System
08/24/2020
71151
Calibration
Records
AMS-025
Calibration Data Ebeline Model AMS-4 Beta
Particulate/Noble Gas Monitors
10/08/2020
71151
Calibration
Records
AMS-031
Calibration Data Ebeline Model AMS-4 Beta
Particulate/Noble Gas Monitors
06/05/2019
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
71151
Calibration
Records
AMS-044
Calibration Data Ebeline Model AMS-4 Beta
Particulate/Noble Gas Monitors
10/08/2020
71151
Calibration
Records
AMS-045
Calibration Data Ebeline Model AMS-4 Beta
Particulate/Noble Gas Monitors
05/20/2020
71151
Miscellaneous
Radiological Controlled Area Entries Greater than 100
millirem Report: 03/26/20 - 01/28/2021
03/22/2021
71151
Miscellaneous
ANO-1 and ANO-2 NRC Performance Indicator
Technique/Data Sheets - RCS Leakage
Q2-2020
71151
Miscellaneous
ANO-1 and ANO-2 NRC Performance Indicator
Technique/Data Sheets - RCS Leakage
Q3-2020
71151
Miscellaneous
ANO-1 and ANO-2 NRC Performance Indicator
Technique/Data Sheets - RCS Leakage
Q4-2020
71151
Miscellaneous
ANO-1 and ANO-2 NRC Performance Indicator
Technique/Data Sheets - RCS Leakage
Q1-2021
71151
Miscellaneous
ANO-1 and ANO-2 NRC Performance Indicator
Technique/Data Sheets - RCS Specific Activity
Q2-2020
71151
Miscellaneous
ANO-1 and ANO-2 NRC Performance Indicator
Technique/Data Sheets - RCS Specific Activity
Q3-2020
71151
Miscellaneous
ANO-1 and ANO-2 NRC Performance Indicator
Technique/Data Sheets - RCS Specific Activity
Q4-2020
71151
Miscellaneous
ANO-1 and ANO-2 NRC Performance Indicator
Technique/Data Sheets - RCS Specific Activity
Q1-2021
71151
Miscellaneous
ANO-1 and ANO-2 NRC Performance Indicator
Technique/Data Sheets - SSFF
Q2-2020
71151
Miscellaneous
ANO-1 and ANO-2 NRC Performance Indicator
Technique/Data Sheets - SSFF
Q3-2020
71151
Miscellaneous
ANO-1 and ANO-2 NRC Performance Indicator
Technique/Data Sheets - SSFF
Q4-2020
71151
Miscellaneous
ANO-1 and ANO-2 NRC Performance Indicator
Technique/Data Sheets - SSFF
Q1-2021
71151
Miscellaneous
0CAN042102
20 Annual Radioactive Effluent Release Report
04/21/2021
71151
Procedures
Regulatory Performance Indicator Process
71151
Procedures
OP-1042.003
Radiochemistry Routine Surveillance Schedule and Tech
Spec Reporting
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Corrective Action
Documents
CR-ANO-
1-2021-00457, 2-2017-02384
Procedures
Causal Analysis Process
Arkansas Nuclear One, Unit 1
Momentary Loss of Power to 4160 Vac bus A2 Event
Detailed Risk Evaluation
A regional senior reactor analyst performed a detailed risk evaluation and determined that the
finding associated with the momentary loss of power to 4160 Vac bus A2 event was of very low
safety significance (Green).
The analyst performed an initiating event analysis as called for in Section 8.0, Initiating Event
Analyses, of Volume 1, Internal Events, of the RASP Handbook. The analyst chose to run
this analysis as a transient (or reactor trip) with circuit breaker 1A-409 failed open (basic
event ACP-CRB-CO-1A409 set to TRUE). During the event, power was lost to bus A2, the
reactor was manually tripped, and power to bus A2 was subsequently restored within 1 minute.
When power was lost to bus A2, breaker 1A-409 (which supplies offsite power to bus A4)
opened and was not reclosed during the initial phases of the event. The resulting conditional
core damage probability was estimated to be 3.50E-7. This estimate equated to an increase in
core damage frequency from internal events of 3.5E-7/year.
The analyst assumed that external events would be an insignificant contributor to the increase
in core damage frequency because the probability of any external event coinciding with the
momentary loss of power to bus A2 event would be extremely low. As a result, only the
increase in core damage frequency from the initiating event was used in the final estimate,
making the total safety significance of the finding very low (Green).
After reviewing Manual Chapter 0609, Appendix H, Containment Integrity Significance
Determination Process, the analyst determined that transient sequences were not significant
contributors to large early release frequency and screened the finding to Green for large early
release frequency.
The analyst ran the Arkansas Nuclear One, Unit 1, SPAR model, Revision 8.60, on SAPHIRE,
Version 8.2.1, to calculate the conditional core damage probability using a cutset truncation of
1.0E-12.