05000251/LER-1917-001, Regarding Manual Reactor Trip Due to Lowering Steam Generator Level Caused by Loss of Flow Regulating Valve Positioner Control
| ML17311A666 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 11/07/2017 |
| From: | Summers T Florida Power & Light Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-2017-190 LER 17-001-00 | |
| Download: ML17311A666 (3) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 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)(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) |
| 2511917001R00 - NRC Website | |
text
U.S. Nuclear Regulatoty Commission Attn: Document Control Desk Washington, D. C. 20555-0001 Re:
Turkey Point Unit 4 Docket No. 50-251 Licensee Event Report: 2017-001-00 Date of Event: September 10, 2017 L-2017-190 10 CFR § 50.73 November 7, 2017 Manual Reactor Trip Due to Lowering Steam Generator Level Caused by Loss of Flow Regulating Valve Positioner Control The attached Licensee Event Report 05000251 /2017-001-00 is submitted pursuant to 10 CFR 50.73(a)(2)(iv)(A) due to actuations of the reactor protection and auxiliary feedwater systems.
If there are any questions, please call Mr. Mitchell Guth at 305-246-6698.
Sincerely, Regional Vice President - Southern Region Florida Power & Light Company Attachment cc:
Regional Administrator, USNRC, Region II Senior Resident Inspector, USNRC, Turkey Point Nuclear Plant Florida Power & Light Company 9760 SW 344th St., Homestead, FL 33035
NRC FORM 366 (04-2017)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
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/r3/)
- 1. FACILITY NAME Turkey Point Unit 4
- 2. DOCKET NUMBER 05000 251
- 3. PAGE 1 OF 2
- 4. TITLE Manual Reactor Trip Due to Lowering Steam Generator Level Caused by Loss of Flow Regulating Valve Positioner Control
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL NUMBER REV NO.
MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 05000 9
10 2017 2017 001 00 11 7
2017 FACILITY NAME DOCKET NUMBER 05000
- 9. OPERATING MODE 1
- 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) 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) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x)
- 10. POWER LEVEL 88 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) 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 NRC Form 366A
- 12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT TELEPHONE NUMBER (Include Area Code)
Paul F. Czaya (305) 247-7150 CAUSE SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX
CAUSE
SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED SUBMISSION DATE MONTH DAY YEAR YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
NO ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On September 10, 2017 at approximately 1855 hours0.0215 days <br />0.515 hours <br />0.00307 weeks <br />7.058275e-4 months <br />, the Turkey Point Unit 4 reactor was manually tripped from 88% power due to lowering level in Steam Generator (SG) C. The reactor was stabilized in Mode 3.
Auxiliary Feed Water actuated as expected on low level in SG C and was secured at approximately 1933 hours0.0224 days <br />0.537 hours <br />0.0032 weeks <br />7.355065e-4 months <br />. At the time of the event, the Turkey Point site was experiencing high winds with rain associated with Hurricane Irma. The B and C Main Feedwater Regulating Valves (MFRV) had been in manual control when the C MFRV failed closed. The cause of the event was a degraded signal due to water intrusion into the C MFRV valve positioner hand selector switch enclosure resulting from a less than adequate design and installation. Corrective actions include modifications to the Unit 3 and 4 MFRV hand selector switch enclosures and enclosure penetrations, and repair of a failed component associated with the 4C MFRV. Additionally, the terminal/pull box specifications will be revised to improve direction for installation activities. Safety significance is very low because the unit responded as designed to the trip.
NRC FORM 366 (04-2017)
DESCRIPTION OF THE EVENT On September 10, 2017 at approximately 1855 hours0.0215 days <br />0.515 hours <br />0.00307 weeks <br />7.058275e-4 months <br />, the Turkey Point Unit 4 reactor [AC, RCT] was manually tripped from 88%
power due to lowering level in Steam Generator [SB, SG] C. The reactor was stabilized in Mode 3. Auxiliary Feed Water (AFW)
[BA] actuated as expected on low level in SG C and was secured at approximately 1933 hours0.0224 days <br />0.537 hours <br />0.0032 weeks <br />7.355065e-4 months <br />. At the time of the event, the Turkey Point site was experiencing high winds with rain associated with Hurricane Irma.
The Reactor Protection System (RPS) [JC], and AFW actuations were reported in accordance with 10 CFR 50.72 in Event Notification 52960 and are also reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A).
CAUSE OF THE EVENT
The direct cause of the event was a degraded signal due to water intrusion into the 4C Main Feedwater Regulating Valve (MFRV)
[SJ, FCV] positioner hand selector switch enclosure. The root cause was a latent weakness in the installation of the enclosure. A contributing cause was a less than adequate design change that installed the enclosures.
ANALYSIS OF THE EVENT
The event was initiated by failure of the 4C MFRV. At the time of the event, level in the 4B and 4C SGs was being controlled manually due to positioner issues. The operator controlling SG levels noticed the 4C SG level was not responding as expected to controller inputs. The 4C SG level continued to lower even though the 4C MFRV and its associated bypass valve both were demanded full open. The reactor operator manually tripped the reactor as briefed at the 20% level in the 4C SG.
Troubleshooting identified water intrusion in the 4B and 4C MFRV positioner selector switches (PSS). During troubleshooting, the 4C MFRV PSS was found to have a broken wire weakened by corrosion. The wire appears to have broken when a cover was removed during the troubleshooting.
ANALYSIS OF SAFETY SIGNIFICANCE Safety significance is very low because the unit responded as designed to the trip.
CORRECTIVE ACTIONS
Corrective actions are contained in Condition Report 2224218 and include:
- 1. Modifications were completed on the Unit 3 and 4 MFRV hand selector switch enclosures and enclosure penetrations. The broken wire associated with the 4C MFRV was repaired. Other enclosures in safety significant systems were also included in the scope of work.
- 2. The terminal/pull box specifications will be revised to improve direction for installation of enclosures needing protection from water intrusion.
ADDITIONAL INFORMATION
EIIS Codes are shown in the format [IEEE system identifier, component function identifier, second component function identifier (if appropriate)].
FAILED COMPONENTS IDENTIFIED: None
PREVIOUS SIMILAR EVENTS
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