05000323/LER-2018-001-01, Automatic Reactor Trip of Unit 2 Following a Load Rejection
| ML19101A435 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 04/11/2019 |
| From: | Welsch J Pacific Gas & Electric Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| DCL-19-030 LER 2018-001-01 | |
| Download: ML19101A435 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v), Loss of Safety Function 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) |
| 3232018001R01 - NRC Website | |
text
Pacific Gas and Electric Company*
April 11, 2019 James M. Welsch Vice President Nuclear Generation and Chief Nuclear Officer Oiablo Canyon Power Plant P.O. Box 56 Avila Beach, CA 93424 805.545.3242 E-Mail: James.Welsch@pge.com PG&E Letter DCL-19-030 10 CFR 50.73 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 Licensee Event Report 2-2018-001-01, Automatic Reactor Trip of Unit 2 Following a Load Rejection Reference: PG&E Letter DCL-19-007, "Licensee Event Report 2-2018-001-00, Automatic Reactor Trip of Unit 2 Following a Load Rejection," dated January 30, 2019 (ADAMS Accession No. ML19030B857)
Dear Commissioners and Staff:
In the above reference, Pacific Gas and Electric Company (PG&E) submitted a Licensee Event Report (LER) regarding an automatic reactor trip of Diablo Canyon Power Plant (DCPP) Unit 2 that occurred on December 1, 2018. In the LER, PG&E indicated that it would provide a supplemental LER following completion of the Root Cause Evaluation. PG&E hereby submits the enclosed supplemental LER.
This supplemental LER provides an updated event cause and corrective action summary based on the completed Root Cause Evaluation.
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,
_/j_ *--M_,~
~Welsch dqmg/6192/51006788-34 Enclosure cc/enc:
Scott A. Morris, NRC Region IV Administrator Christopher W. Newport, NRC Senior Resident Inspector Balwant K. Singal, NRR Senior Project Manager Diablo Distribution A
m ember of t he STARS Alliance Callaway* Diablo Ca nyon
- Pa lo Verde* Wo lf Creek
NRC FORM366 U.S. NUCLEAR REGULA TORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-201 8)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
3.Page Diablo Canyon Power Plant, Unit 2 05000 323 1
OF 4
- 4. Title Automatic Reactor Trip of Unit 2 Following a Load Rejection
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved Month I
Sequential I Rev Facility Name Docket Number Day Year Year Number No.
Month Day Year 05000 Facility Name Docket Number 12 01 2018 2018 -
001 -
01 04 11 2019 05000 1--
- 9. Operating Mode
- 11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply) 20.2201(b) 20.2203(a)(3)(i)
- 50. 73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2201(d) 20.2203(a)(3)(ii)
- 50. 73(a)(2)(ii)(B)
- 50. 73(a)(2)(viii)(B) 1 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(iii)
- 50. 73(a)(2)(ix)(A)
- 20. 2203( a)(2)(i) 50.36(c)(1)(i)(A) 0 50.73(a)(2)(iv)(A) 50.73(a)(2)(X)
- 10. Power Level 20.2203(a)(2)(ii) 50.36(c)(1 )(ii)(A) 50.73(a)(2)(v)(A) 73.71(a)(4) 20.2203(a)(2)(iii) 50.36(c)(2)
- 50. 73(a)(2)(v)(B)
- 73. 71 (a)(5) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(C) 73.77(a)(1) 100 20.2203(a)(2)(v) 50 73(a)(2)(i)(A)
- 50. 73(a)(2)(v)(D) 73.77(a)(2)(i) 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(vii) 73.77(a)(2)(ii) 50.73(a)(2)(i)(C)
Other (Specify in Abstract below or in C. Status of Inoperable Structures, Systems or Components that Contributed to the Event There were no inoperable structures, systems or components that contributed to the event.
D. Other Systems or Secondary Systems Affected None.
E. Method of Discovery
REV NO.
01 The event was immediately apparent to plant operators due to alarms and indications associated with the load rejection received in the control room.
F. Operator Actions
Control room personnel responded in accordance with established procedures, confirmed the reactor trip, verified proper engineered safety feature actuations, and stabilized the unit in Mode 3.
G. Safety System Responses The trip was not complex; all safety systems responded as designed.
IV. Cause of the Problem The DCPP Unit 2 trip was caused by the automatic actuation of the DC-SPS that occurred when DC-SPS sensed two out of three 500 kV lines out of service when all three lines were in service. The DC-SPS ROD logic used local current, independent of breaker position, for detecting a remote-end outage to determine if 500k kV lines were in service.
V. Assessment of Safety Consequences
There were no safety consequences as a result of this event. The Operations crew responded to the event in accordance with plant operating procedures. Equipment necessary for Unit 2 decay heat removal was available and operated as required by plant design. Unit 1 was not affected by this event. There was no impact on the health and safety of the public or plant personnel.
VI. Corrective Actions
The ROD logic portion of the DC-SPS circuitry has been disabled and mitigation measures have been implemented, including improved communications with the Grid Control Center. In addition, PG&E Transmission Operations, in partnership with DCPP, is redesigning the ROD logic of the DC-SPS. Page 4
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