05000219/LER-2015-001, Regarding Reactor Scram Due to EPR Failure During MPR Troubleshooting
| ML15154A493 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 05/21/2015 |
| From: | Dostal J Exelon Generation Co |
| To: | Office of Nuclear Material Safety and Safeguards |
| References | |
| RA-15-041 LER 15-001-00 | |
| Download: ML15154A493 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 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)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 2192015001R00 - NRC Website | |
text
Exelon Generation.
RA-15-041 10 CFR 50.73 May 21, 2015 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 - 0001 Oyster Creek Nuclear Generating Station Renewed Facility Operating License No. DPR-16 NRC Docket No. 50-219
Subject:
Licensee Event Report (LER) 2015-001-00, Reactor Scram due to EPR Failure During MPR Troubleshooting Enclosed is LER 2015-001-00, Reactor Scram due to EPR Failure During MPR Troubleshooting. This event did not affect the health and safety of the public or plant personnel. This event did not result in a safety system functional failure. There are no regulatory commitments made in this LER submittal.
Should you have any questions concerning this letter, please contact Mike McKenna, Regulatory Assurance Manager, at (609) 971-4389.
Respectfully, CJeffro Plant Manager Oyster Creek Nuclear Generating Station Enclosure: NRC Form 366, LER 2015-001-00 cc:
Administrator, NRC Region 1 NRC Senior Resident Inspector - Oyster Creek Nuclear Generating Station NRC Project Manager - Oyster Creek Nuclear Generating Station
NRC FORM 366 U.S. NUCLEAR REGULATORYCOMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 01311/2017 o0i.2014)
- nflmatnd burden per response to comply with this mandatory collection request 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.
Rpo*led lessons learned are ncorporated into the licendsng process and fed back to industy.
,9nd comments regarding burden estimate to the FOIA, Pdvacy and Information Cotlections SICENSEE EVENT (T-5 F53 U.S. Nuclear Regulatory Comnission, Washington, DC 20556-0o0, or by REPORT (LER) interna e-tni to tfocolets.Rescuhae@nm.gov, and to the Desk Officer, Office of Information and (See Page 2 for required number 0f ikguatoioryAffair, NEOB-1020Z (31500104), Office of Management and Budget, Washington, DC dch03. If a means used to imnpoee an information collection does not dsplay a currently valid OMB digits/characters for each block) control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the wtr lationcolecoon.
- 3. PAGE Oyster Creek, Unit 1 05000219 1 OF 3
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED M AYE FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIALuMR NREVo MOT DAY YEAR N/AN/
NUMBER NO.
MONTH DANYEAE/
03 22 2015 2015 -
001
- - 00 05 21 2015 N/A N/A
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
I20.2201(b) 20.2203(a)(3)(i) 0 50.73(a)(2)(I)(C)
El 50.73(a)(2)(vii)
N 20.2201(d)
E] 20.2203(a)(3)(i)
['
50.73(a)(2)(i)(A)
E.50.73(a)(2)(viii)(A)
N 20.2203(a)(1)
]
20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
_ 20.2203(a)(2)(i) 50.3(c)(1)(i)(A) 50.73(a)(2)(iii)
E 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL 20.2203(a)(2)(ii)
[E 50.36(c)(1)(i)(A)
(0 50.73(a)(2)(iiA) 0l 50.73(a)(2)(x) 1] 20.2203(a)(2)(iii)
El 50.36(c)(2
()
E 50.73(a)(2)(v)(A)
El 73.71 (a)(4)
%l 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71 (a)(5) 1% 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
El OTHER i
Specify in Abstract below or in 20.2203(a)(2)(vi)
[]
50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
NSC Formy MA
- 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME TELEPHONE NUMBER (Include Area Code)
Michael McKenna, Regulatory Assurance Manager (609) 971-4389C S
MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT MANU-REPORTABLE SYSTEM FACTURER TO EPIX FACTURER TO EPIX A
N/A N/A N/A N
N/A N/A N/A N/A N/A
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR
[
YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
El NO DATE 06 19 15 ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewdtten lines)
On March 22, 2015 at 1414, an automatic SCRAM from full power operation occurred at Oyster Creek due to a valid RPS actuation on APRM Hi-Hi flux. The APRM Hi-Hi flux was caused by a rise in reactor pressure due to the failure of the Electric Pressure Regulator (EPR). The backup Mechanical Pressure Regulator (MPR) did not limit reactor pressure.
The scram occurred due to inadvertent contact with degraded wiring during troubleshooting to isolate a DC ground identified within the turbine control indication circuity. The contact caused a loss of signal from the EPR to its controlling Programmable Logic Controller (PLC) resulting in a loss of the EPR. This loss of signal, concurrent with the MPR being out of position, resulted in the subsequent rise of both reactor pressure and APRM flux that caused the SCRAM.
ENS 50916 was submitted on March 22, 2015 as required by 10 CFR 50.72 (b)(2)(iv)(B). This issue is reportable under 10 CFR 50.73(a)(2)(iv)(A), any event or condition that resulted in manual or automatic actuation of any of the systems listed in DaraaraDh (a)(2)(iv)(B).
NRC FORM 366 (01-2014)
Description of Event
On March 19, 2015 the EPR was in control of reactor pressure and the MPR was set as the backup regulator. At 2128, Oyster Creek received a ground on the DC-A bus (9XF-8-e). The DC ground caused the indicating light for the MPR to illuminate while the EPR was in control. Operations validated the EPR was in control and had reasonable assurance the MPR was available as the backup regulator.
On March 20, 2015 at 0944, an AC ground was received which removed multiple indications in the Main Control Room (MCR) including the MPR relay position and pressure set-point position. The last known MPR relay position was 10% from the EPR relay position.
On March 21, 2015, troubleshooting on the DC ground was in progress. At 2115, a lead was lifted and the MPR positon indication light bulb was removed, isolating the DC ground to the circuit for the MPR "in control" light. This circuit contains the MPR "in control" light bulb socket in the MCR and the associated mechanical limit switch, FRS-1, in the Front Standard.
On March 22, 2015, the execution of a troubleshooting action plan (TSAP) determined that the FRS-1 limit switch and associated wiring were the source of the ground. Additionally, it was identified that the limit switch compartment contained water, and wire insulation was degraded within the switch compartment. The source of this water was a local steam leak from the MPR sensing line that had been present since the 1 R25 startup. At approximately 1300, replacement of the FRS-1 limit switch and its degraded wires was pursued.
On March 22, 2015 at 1414, while tracing out the FRS-1 wires to be replaced in a junction box containing various Turbine Controls wiring in the Front Standard, EPR wiring was disturbed and the EPR circuit failed. The MPR relay position was at -22% away from the EPR, which allowed reactor pressure to peak at 1036.6 psig and the reactor to SCRAM on APRM Hi-Hi flux.
Analysis of the Event
Following the actuation, all systems responded as expected; therefore, this event is of low safety significance.
Cause of Event
Subsequent troubleshooting determined that the cause of the EPR failure was due to a loss of a control valve position feedback signal to the EPR circuitry from a linear variable differential transformer, DT-1. This signal was grounded, and as a result, the EPR circuitry defaulted to close the Turbine Control Valves which raised reactor pressure. Failure analysis of a grounded connector plug and wiring associated with DT-1, determined that insulation on individual wires within the wiring bundle was significantly degraded due to age (e.g., stiff, brittle insulation), and was internally grounded. This degraded wire was inside the junction box, and in the immediate vicinity of the FRS-1 switch wires being traced out by the DC ground troubleshooting team at the time of the EPR failure. Interviews concluded that this wire was disturbed during this evolution and caused the EPR failure.
Corrective Actions
Corrective actions will be developed during the ongoing root cause evaluation.
Previous Occurrences
Previous occurrences will be identified through the root cause evaluation.