05000323/LER-2020-001, Shutdown Required by Technical Specifications
| ML20100K071 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 04/09/2020 |
| From: | Gerfen P Pacific Gas & Electric Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| DCL-20-023 LER 2020-001-00 | |
| Download: ML20100K071 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown |
| 3232020001R00 - NRC Website | |
text
Pacific Gas and Electric Company*
April 9, 2020 PG&E Letter DCL-20-023 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-323, OL-DPR-82 Diablo Canyon Power Plant, Unit 2 Paula Gerfen Site Vice President Diablo Canyon Power Plant Mail code 104/6/605 P.O. Box 56 Avila Beach, CA 93424 805.545.4596 Internal: 691.4596 Fax: 805.545.4234 10 CFR 50.73 Unit 2 Licensee Event Report 2020-001-00, Unit 2 Shutdown Required by Technical Specifications
Dear Commissioners and Staff,
In accordance with the requirements of 10 CFR 50.73(a)(2)(i)(A), Pacific Gas and Electric Company (PG&E) hereby submits the enclosed Diablo Canyon Power Plant (DCPP) Unit 2 Licensee Event Report regarding a Technical Specification required shutdown due to control rod misalignment.
PG&E makes no new or revised regulatory commitments (as defined by NEI 99-04) in this report. All corrective actions identified in this letter will be implemented in accordance with the DCPP Corrective Action Program.
This event did not adversely affect the health and safety of the public.
Sincerely,
"* f>Q.ct:: -rQ <
Paula Gerten dqmg/51067154 Enclosure cc/enc:
Scott A. Morris, NRC Region IV Administrator Christopher W. Newport, NRC Senior Resident Inspector Balwant K. Singal, NRR Senior Project Manager INPO Diablo Distribution A member of the STARS Alli ance Callaway
- Diab l o Canyon
- Pa l o Verde
- Wo l f Creek
NRCFORM366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2018)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the informatio_n --(
collection.
YEAR Diablo Canyon Power Plant, Unit 2 05000-323 2020
- 3. LER NUMBER SEQUENTIAL NUMBER
- - 001 REV NO.
- - 00 TS 3.1.4, "Rod Group Alignment Limits," Action D, a shutdown to Mode 3 (required within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />) was commenced at 1233 hours0.0143 days <br />0.343 hours <br />0.00204 weeks <br />4.691565e-4 months <br />. While ramping the unit to Mode 3, an existing issue with Main Feedwater Regulating Valve FCV-510 resulted in temporarily placing the ramp on hold. In order to maintain T-ave, the control system withdrew Control Bank D to respond to the T-ave / power mis-match. When Bank D moved out, Group 1 did not respond to the rods out demand while Group 2 responded appropriately.
This caused Control Bank D to be misaligned. The shutdown ramp was recommenced; however, was temporarily placed on hold again due to main generator stator cooling water delta temperature. Unit 2 was subsequently shut down and Mode 3 was entered at 1545 hours0.0179 days <br />0.429 hours <br />0.00255 weeks <br />5.878725e-4 months <br />.
Following the shutdown, Maintenance investigation into the cause of the rod misalignment determined that Unit 2 A410 Slave Cycler Decoder Lift card had functioned incorrectly during the surveillance test and shutdown, which resulted in incorrect timing signals to be sent to the affected rods. The A410 Slave Cycler Decoder Lift card controls both Shutdown Bank B and Control Bank D. The Slave Cycler Decoder Lift card had been in service since May 2016 without any similar issues noted.
C. Status of Inoperable Structures, Systems or Components that Contributed to the Event Except as noted above, other structures, systems, and components functioned properly during the event.
D. Other Systems or Secondary Systems Affected No other systems or secondary systems were affected by the rod misalignment.
E. Method of Discovery
Self-identified. This condition was discovered during the quarterly control rod exercise surveillance testing.
F. Operator Actions
Upon discovery of the control rod mis-alignment during the performance of the quarterly surveillance test, TS 3.1.4, "Rod Group Alignment Limits," Action D, a Unit 2 shutdown to Mode 3 was commenced. Mode 3 was entered at 1545, and the associated TS were exited. The Operations crews responded to this event in accordance with plant operating procedures.
G. Safety System Responses There were no safety system responses as a result of this event.
IV. Cause of the Problem The cause of the rod misalignment was a result of the failure of the Unit 2 A410 Slave Cycler Decoder Lift card to provide proper timing signals.
Neither DCPP nor outside testing facility could reproduce the card anomaly in subsequent testing.
V. Assessment of Safety Consequences
There were no safety consequences as a result of this event. At no time was rod control unable to perform its intended safety function of inserting or tripping control rods There was no impact on health and safety of the public or plant personnel. (04-2018)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 3/31/2020 LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form l)ttp://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3Q
, the NRC may not conduct or sponsor, and a person is not required to respond to, the informatioD _ ---(
collection.
- 3. LER NUMBER YEAR Diablo Canyon Power Plant, Unit 2 05000-323 2020
VI. Corrective Actions
SEQUENTIAL NUMBER
- - 001 REV NO.
- - 00 The failed card has been replaced. Follow-up corrective actions to prevent recurrence will be managed in accordance with the DCPP Corrective Action Program.
VII. Additional Information
There have been no similar events at DCPP in the previous three years.