05000416/LER-2020-002-02, Reactor Scram Due to Main Turbine Trip
| ML21231A135 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 08/19/2021 |
| From: | Hardy J Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML21231A134 | List:
|
| References | |
| GNRO-2021/00019 LER 2020-002-02 | |
| Download: ML21231A135 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) |
| 4162020002R02 - NRC Website | |
text
~~~ Entergy Entergy Operations, Inc.
P.O. Box 756 Port Gibson, Mississippi 39150 GNRO-2021/00019 August19,2021 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Jeff A. Hardy Regulatory Assurance Manager Grand Gulf Nuclear Station Tel: 601-437-7500 10 CFR 50.73
SUBJECT:
Grand Gulf Nuclear Station, Unit 1 Revised Licensee Event Report 2020-002-02 Grand Gulf Nuclear Station, Unit 1 Docket No. 50-416 Renewed License No. NPF-29 Attached is revised Licensee Event Report 2020-002-02, Reactor Scram Due to Main Turbine Trip. This report is being submitted in accordance with 10 CFR 50.73(a)(2}(iv}(A), for any event or condition that resulted in manual or automatic actuation of the Reactor Protection System (RPS).
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 269-764-2011.
Sincerely, 94l{a Jeff A. Hardy JAH/fas Attachments: Revised Licensee Event Report 2020-002-02
GNRO-2021/00019 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
GNRO-2021/00019 Page 3 of 3 Attachment Revised Licensee Event Report 2020-002-02
NRC FORM366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 08/31/2023 (08-2020)
- 1. Facility Name
- 12. Docket Number
. Page Grand Gulf Nuclear Station, Unit 1 05000 416 1 OF3
- 4. Title Reactor Scram Due to Main Turbine Trio
- 5. Event Date
- 6. LEA Number
- 7. Report Date
- 8. Other Facilities Involved Sequential Rev Facility Name Docket Number Month Day Year Year Month Day Year N/A Number No.
05000 N/A 05 25 2020 2020
- - 002
- - 02 08 19 2021 Facility Name Docket Number N/A 05000 N/A
- 9. Operating Mode
- 11. This Reoort is Submitted Pursuant to the Reauirements of 10 CFR §: {Check all that annlvJ 1
0 20.2201 (b)
D 20.2203(a)(3)(i) 0 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A) 0 20.2201 (d)
D 20.2203(a)(3)(ii) 0 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
D 20.2203(a)(1)
D 20.2203(a)(4)
D 50.73(a)(2)(iii)
D 50.73(a)(2)(ix)(A)
D 20.2203(a)(2)(i) 0 50.36(c)(1 )(i)(A) 181 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x) 1 D. Power Level D 20.2203(a)(2)(ii) 0 50.36(c)(1 )(ii)(A)
D 50.73(a)(2)(v)(A)
D 73.71 (a)(4)
D 20.2203(a)(2)(iii)
D 50.36(c)(2)
D 50.73(a)(2)(v)(B)
D 73.71 (a)(5) 66 D 20.2203(a)(2)(iv)
D 50.46(a)(3)(ii)
D 50.73(a)(2)(v)(C)
D 73.77(a)(1)
D 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A)
D 50.73(a)(2)(v)(D)
D 73.77(a)(2)(ii)
D 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 73.77(a)(2)(iii) 0 50.73(a)(2)(i)(C)
D Other (Specify in Abstract below or in NRG Form 366A
- 12. Licensee Contact for this LEA Licensee Contact r elephone Number (Include Area Code)
Jeff Hardy, Manager Regulatory Assurance I (601) 437-2103
- 13. Complete One Line for each Comoonent Failure Described in this Report
Cause
System Component Manufacturer Reportable To ICES
Cause
System Component Manufacturer Reportable To ICES NA NA NA NA NA NA NA NA NA NA
- 14. Supplemental Report Expected Month Day Year D Yes (If yes, complete 15. Expected Submission Date) [8J No
- 15. Expected Submission Date Abstract (limit to 1400 spaces, i.e., approximately 14 single-spaced typewritten lines)
At 0433 CT on Monday, May 25, 2020, while operating in MODE 1 at approximately 66 percent power, Grand Gulf Nuclear Station (GGNS) experienced an automatic Reactor SCRAM due to a Main Turbine Trip. All systems responded as designed. The plant was stabilized in MODE 3.
The Root Cause of the event is that Entergy Engineering Leadership (Corporate Projects and Site Engineering) did not ensure critical assumptions in EC 72780, Turbine Control Protection System - Non-Safety, were documented or validated for turbine shaft movement during operation where a reduction in margin was present in accordance with EN-DC-115, Engineering Change Process roles and responsibilities were not well communicated across organizations, and leadership behaviors were lacking to promote sufficient challenge to achieve an acceptable result to prevent an unplanned Scram.
The corrective actions to preclude repetition was to revise EN-HU-104, Technical Task Risk & Rigor, to require creation of a detailed table listing generation risk parameters (setpoints, settings, dimensions) for engineering changes with high generation risk.
There were no consequences to the general safety of the public, nuclear safety, industrial safety and radiological safety.
This report is made in accordance with 10 CFR 50.73(a)(2)(iv)(A), for any event or condition that resulted in manual or automatic actuation of the Reactor Protection System (RPS).
NRG FORM 366 (0B-2020)
Plant Conditions
YEAR 2020 SEQUENTIAL NUMBER
- - 002 Grand Gulf Nuclear Station (GGNS) Unit 1 was operating at approximately 66 percent power in MODE 1. There were no Structures, Systems, or Components that were inoperable that contributed to this event.
Event Description
REV NO.
- - 02 At 0433 CT on Monday, May 25, 2020, while operating in MODE 1 at approximately 66 percent power, GGNS experienced an automatic Reactor SCRAM due to a Main Turbine [TA] Trip at a power level beyond the capability of the Turbine Bypass valves. The unit was shutdown without complication using pressure control through the main condenser.
The unit tripped during valve testing in the initial power ascension following implementation of a Digital Turbine Control System upgrade during RF22.
All systems responded as designed. No loss of offsite power or Engineered Safety Feature actuation occurred. No Emergency Core Cooling System or Emergency Diesel Generator initiations occurred. Main Steam Isolation valves remained open and no radioactive release occurred due to this event. The plant was stabilized in MODE 3.
This event was reported under 10 CFR 50.72(b)(2)(iv)(B), for any event that results in tt:ie actuation of the Reactor Protection System (RPS), when the reactor is critical. Event Notification EN54725.
This report is made pursuant to 10 CFR 50.73(a)(2)(iv)(A), as any event or condition that results in manual or automatic actuation of the RPS.
Event Cause(s):
The direct cause of the trip was determined to be inadvertent overspeed signals from two (2) Active Speed Probes which contacted the speed wheel installed on the turbine shaft. The contact resulted from movement of the shaft during operation of the turbine_ The contact occurred when one of four steam lines to the High-Pressure turbine was being isolated during valve stroke testing. The speed sensing probes, and speed sensing wheel had been modified via installation of new equipment during RF22 with a smaller air gap which reduced operating margin.
The Root Cause of the event is that Entergy Engineering Leadership (Corporate Projects and Site Engineering) did not ensure critical assumptions in EC 72780, Turbine Control Protection System - Non-Safety, were documented or validated for turbine shaft movement during operation where a reduction in margin was present. In accordance with EN-DC-115, Engineering Change Process roles and responsibilities were not well communicated across organizations, and leadership behaviors were lacking to promote sufficient challenge to achieve an acceptable result to prevent an unplanned Scram.
Safety Assessment
The Reactor Scram due to the Main Turbine Trip did not result in actual consequences to safety of the general public, nuclear safety, industrial safety or radiological safety. The safety significance of this event is determined to be low. The response to the Scram was performed in accordance with plant procedures. Plant parameters (reactor level, pressure) were maintained within procedure and safety limits. There were no actual nuclear safety consequences or radiological consequences during the event. Page 2 of 3 (08-2020)
_/'°'\\
\\.j U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-colleclions/nuregs/staff/sr1022/@
APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 08/31/2023
- 3. LEA NUMBER YEAR Grand Gulf Nuclear Station, Unit 1 05000-416 2020
Corrective Actions
SEQUENTIAL NUMBER
- - 002 REV NO
- - 02 A work order was implemented to change the active and passive turbine speed probe to speed wheel air gap from 35 mils to 50 mils which bounds the original equipment air gap setting of 47 mils (the minimum air gap is now larger than the original air gap). This action is complete.
To preclude repetition, Entergy's procedure EN-HU-104, Technical Task Risk and Rigor, was revised to require creation of a detailed table listing generation risk parameters (setpoints, settings, dimensions) being revised for engineering changes with high generation risk. This table lists the old parameter, new, and basis for acceptability. This table would then be presented for challenge such as Independent Third-Party Review, and challenge board.
Entergy placed the vendor on Conditional Services until their cause analysis was completed, cause and corrective actions I were accepted by Entergy, and associated actions are completed.
I Previous Similar Event:
Entergy conducted a three-year review of the relevant licensee event reports and determined that there were no
similar events