05000416/LER-2021-004, Procedure Inadequacy Resulted in Core Monitoring System Miscalibration and Violation of Technical Specification
| ML22019A270 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 01/19/2022 |
| From: | Hardy J Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| GNRO2022/00004 LER 2021-004-00 | |
| Download: ML22019A270 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4162021004R00 - NRC Website | |
text
Jeff Hardy Digitally signed by Jeff Hardy Date: 2022.01.19 15:21:23 -06'00'
....... Entergy GNRO2022/00004 January 19, 2022 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Entergy Operations, Inc.
P.O. Box 756 Port Gibson, Mississippi 39150 Jeffery A. Hardy Manager Regulatory Assurance Grand Gulf Nuclear Station Tel: 802-380-5124 10 CFR 50.73
SUBJECT:
Grand Gulf Nuclear Station, Unit 1 Licensee Event Report 2021-004-00, Procedure Inadequacy Resulted in Core Monitoring System Miscalibration and Violation of Technical Specification Grand Gulf Nuclear Station, Unit 1 Docket No. 50-416 Renewed License No. NPF-29 Attached is Licensee Event Report 2021-004-00, Procedure Inadequacy Resulted in Core Monitoring System Miscalibration and Violation of Technical Specification. This report is being submitted in accordance with 10 CFR 50.73(a)(2)(i)(B) any operation or condition which was prohibited by the plant's Technical Specifications.
This letter contains no new Regulatory Commitments. Should you have any questions concerning the content of this letter, please contact Jeff Hardy, Regulatory Assurance Manager at 802-380-5124.
Sincerely, JAH/saw Attachments: Licensee Event Report 2021-004-00
GNRO2022/00004 Page 2 of 3 cc:
NRC Senior Resident Inspector Grand Gulf Nuclear Station Port Gibson, MS 39150 U.S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
GNRO2022/00004 Page 3 of 3 Attachment Licensee Event Report 2021-004-00
Abstract
On November 18, 2021, a Past Operability Evaluation determined that an issue associated with jet pump summer miscalibration was a reportable event. Specifically, while performing, 17-S-02-5, Post Refueling Recirculation System Flow Instrumentation Calibration (site procedure), it was discovered that multiple conversion calculations in the procedure were incorrect and the procedural guidance for which data points to use in the calculation was unclear. This affects the transmitter and computer point calibration data used by Instrumentation and Control (l&C) personnel. This caused an incorrect core flow indication to the control room panel indication and the Core Monitoring System. Resulting in a violation of Technical Specification (TS) 3.2.2 for Minimum Critical Power Ratio (MCPR).
There were no actual safety consequences for this event. Reactor Engineering and Operations had agreed to a Compensatory Measure and issued Standing Order 21 -05 (Administrative Limit for Maximum Fraction of Limiting Core Power Ratio MFLCPR) to establish an administrative reduction in MFLCPR limit to 0.970. Standing Order 21-018 (Total Core Flow Indication) was issued to provide operators the ability to calculate total core flow using reactor recirculation drive flow indications that were not impacted by the calibration of the jet pump instrumentation.
There were no consequences to the general safety of the public, nuclear safety, industrial safety, or radiological safety. No radiological releases occurred due to this event.
Plant Conditions
YEAR 2021 SEQUENTIAL NUMBER
- - 004 Grand Gulf Nuclear Station (GGNS) Unit 1 was operating at 100 percent power in MODE 1. There were no Structures, Systems, or Components that were inoperable that contributed to this event.
Event Description
REV NO.
- - 00 On January 29, 2021, due to errors in the site procedure, Reactor Engineering provided l&C personnel incorrect voltage inputs that resulted in the miscalibration of the Jet Pump Loop Flow Summers for Loop A and Loop B. This miscalibration caused an incorrect core flow indication to the control room panel indication and the Core Monitoring System, resulting in a violation of Technical Specification (TS) 3.2.2 MCPR.
On July 29, 2021, it was determined that multiple conversion calculations in the procedure were incorrect, and the procedural guidance was unclear. This resulted in the wrong data for jet pump flow being used to calibrate Jet Pump Loop Flow Summers for Loop A and Loop B. Additionally, it was determined that the core flow signal from the jet pump summers to the core monitoring software was 1.95 [Mlbm/hr] higher than actual core flow (a difference of approximately two percent of rated flow) and there was an adverse effect on thermal limits generated by the core monitoring software to satisfy technical specification Limiting Condition for Operation 3.2.2. In response to this issue, an administrative reduction in MFLCPR limit to 0.970 was applied. This was put in place via Standing Order 21-015.
On November 18, 2021, a Past Operability Evaluation determined that an issue associated with jet pump summer miscalibration was a reportable event. Specifically, while performing the site procedure, it was discovered that multiple conversion calculations in the procedure were incorrect and the procedural guidance for which data points to use in the calculation was unclear. This affects the transmitter and computer point calibration data used by l&C personnel. This caused an incorrect core flow indication to the control room panel indication and the Core Monitoring System Resulting in a violation of Technical Specification (TS) 3.2.2 for MCPR.
The Human Performance Evaluation identified two factors that contributed to the condition. First, the procedure used for performing the core flow instrumentation calibration, contains gaps in process as well as confusing and vague steps for calculations. The other factor identified was gaps in knowledge of the core flow calibration process, including gaps in knowledge of the methodology used in the jet pump calibration spreadsheet used with the site procedure to perform the calculations.
The Organizational and Programmatic (O&P) process identified two factors that contributed to the condition - process weaknesses and organizational problems with program execution. Procedure contains errors and there are inconsistencies between it and the spreadsheet used to perform the calculations. The procedure also contains gaps in the core flow calibration process compared to the standard method from the General Electric Station Nuclear Engineering Manual, and it is unclear and vague on certain steps performing calculations. There are also inconsistencies between the procedure and the spreadsheet used to perform the calculations. The responsibility to implement the Software Quality Assurance (SQA) program is not well understood for utilizing spreadsheets in the reactor engineering group. Page 2 of 3 (08-2020)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 08/31/2023
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- fl" LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form https:/iwww.nrc.qovireading-rrn/doc-collect1ons/nureqs staff sr1022/r3/)
Grand Gulf Nuclear Station, Unit 1 05000 - 416 YEAR
- 3. LEA NUMBER SEQUENTIAL NUMBER REV NO.
2021
- - 004
- - 00
Safety Assessment
There were no actual consequences for this event. Reactor Engineering and Operations agreed to a Compensatory Measure and issued Standing Order No: 21-015 to establish an administrative reduction in MFLCPR limit to 0.970.
Standing Order 21-018 was issued to provide operators the ability to calculation total core flow using reactor recirculation drive flow indications that were not impacted by the calibration of the jet pump instrumentation. As a result, there was no impact to the health and safety of the public or plant personnel from this condition. In addition, this event does not meet the criteria for a Safety System Functional Failure.
Event Cause(s):
The site procedure, and the spreadsheet used to implement the procedure contain errors and gaps in the core flow calibration process.
The spreadsheet used by Reactor Engineering to perform the Core Flow Calibration process is not in the SQA Program.
There is a knowledge gap in Reactor Engineering of the Core Flow Calibration process.
The Apparent Cause Analysis from CR-GGN-2018-8553 had inadequate corrective actions. The 2018 evaluation determined that a lack of questioning attitude was a causal factor in that it was not applied to question the validity of the results. Corrective actions completed included revising the site procedure to compare new data to past data.
However, the evaluation and corrective actions did not go a step further to question the procedure and process used.
In the revision (12), the computer code program (JRPUMP) was retired, and the procedure was revised to perform the calibration without it. The 2018 revision did not clearly and adequately accomplish removing the use of JRPUMP while keeping to the calibration process. Inadequate technical rigor used when the site procedure was revised, which led to the technical errors.
Corrective Actions
Revise the site procedure to correct the conditions identified associated with gaps and errors in the procedure. Due Date 06/30/2022. Completion tracked by Corrective Action Program Reperform Jet Pump Calibration. Due Date 07/29/2022. Completion tracked by Corrective Action Program.
Correct errors in jet pump calibration spreadsheet and align with procedure. Due Date 07/13/2022. Completion tracked by Corrective Action Program.
Standing Order 21-005 to establishing an administrative reduction in MFLCPR limit to 0.970. Complete.
Standing Order 21-018, to provided operators the ability to calculate total core flow using reactor recirculation drive flow indications that are not impacted by the calibration of the jet pump instrumentation. Complete.
Previous Similar Events
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