05000443/LER-2018-003, Overpower Delta T Setpoint Exceeded Allowable Value for Time Longer than Permitted by the Technical Specifications
| ML18330A208 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 11/26/2018 |
| From: | Browne K NextEra Energy Seabrook |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| SBK-L-18184 LER 2018-003-00 | |
| Download: ML18330A208 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4432018003R00 - NRC Website | |
text
November 26, 2018 10 CFR 50.73 Docket No. 50-443 SBK-L-18184 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Seabrook Station NEXTeraM ENERGY~
Licensee Event Report (LER) 2018-003-00 Overpower Delta T Setpoint Exceeded Allowable Value for Time longer than Permitted by the Technical Specifications Enclosed is Licensee Event Report (LER) 2018-003-00. This LER reports an event that occurred at Seabrook Station on September 27, 2018. This event is being reported pursuant to the requirements of 10 CFR 50.73(a)(2)(i)(B).
Should you require further information regarding this matter, please contact me at (603) 773-7932.
Sincerely, NextEra Energy Seabrook, LLC cc:
D. Lew, Acting NRC Region I Administrator J. Poole, NRC Project Manager P. Cataldo, NRC Senior Resident Inspector NextEra Energy Seabrook, LLC P.O. Box 300, Seabrook, NH 03874
Enclosure to SBK-L-18184
NRC FORM 366 (04-2018)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 LICENSEE EVENT REPORT (LER)
(See Page 2 for required number of digits/characters for each block)
(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r30
, the NRG may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. Page Seabrook Station 05000 443 1
OF 2
- 4. Title Overpower Delta T Setpoint Exceeded Allowable Value for Time Longer than Permitted by the Technical Specifications
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved I
Sequential I Rev Facility Name Docket Number Month Day Year Year Number No.
Month Day Year 05000 Facility Name Docket Number 09 27 2018 2018 -
003 -
00 11 26 2018 05000
- 9. Operating Mode Manufacturer I Reportable to ICES Month Day Year On September 27, 2018 with the plant operating in Mode 1, control room operators discovered spiking and elevated operation of the reactor coolant loop 4 overpower delta T (OPDT) setpoint during a computer trend review. The OPDT setpoint spike and elevated operation, which exceeded its allowable Technical Specifications (TS) value, started at approximately 0200 on September 25, 2018 and remained above the allowable value until 1600 on September 26, 2018.
The cause of this condition was the erratic operation of one of the four associated Westinghouse 7300 cards. The corrective action was to replace all four of the 7300 cards.
The condition had no impact on public health and safety because the three other redundant OPDT channels remained operable during the time the loop 4 instrument was inoperable.
NRG FORM 366 (04-2018)
Description of the Event -
On September 27, 2018 with the plant operating in Mode 1, control room operators discovered spiking and elevated operation in the reactor coolant [EEIS: AB] loop 4 overpower delta T (OPDT) setpoint during a computer trend review. The OPDT setpoint spike and elevated operation, exceeded its allowable Technical Specifications (TS) value for a time longer than permitted by the TS, which started at approximately 0200 on September 25, 2018 and remained above the allowable value for approximately 38 hours4.398148e-4 days <br />0.0106 hours <br />6.283069e-5 weeks <br />1.4459e-5 months <br /> until 1600 on September 26, 2018.
Cause -
Initial troubleshooting identified that a malfunction in one of the four associated Westinghouse 7300 cards [EEIS: CBD]
was the most likely cause of the setpoint spike and elevated operation, but no one board was found to be the direct
cause
Analysis of the Event -
The reactor trip system automatically keeps the reactor operating within a safe region by shutting down the reactor whenever the limits of the region are approached. The OPDT trip protects against excessive power (fuel rod rating protection), and trips the reactor using a two out of four coincidence using a variable setpoint that is continuously calculated by the 7300 system analog circuitry. The OPDT trip is designed to provide sufficient protection for slow transients.
Three other redundant OPDT channels remained operable during the time the loop 4 instrument was inoperable. Since two OPDT channels are sufficient to initiate a reactor trip, the condition did not result in a safety system functional failure and had no adverse impact on the plant or on the health and safety of the public. No inoperable structures, systems, or components contributed to this event.
Corrective Actions-The corrective action was to replace all four of the 7300 cards.
Additional Information-The Energy Industry Identification System (EllS) codes are included in this LER in the following format: [AB - Reactor Coolant System, CBD - Board, Control].
Similar Events -
None.
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