05000278/LER-2019-001, Failure of Reactor Mode Switch Results in Condition Prohibited by Technical Specifications
| ML19354A927 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 12/19/2019 |
| From: | Pat Navin Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 19-142 LER 2019-001-00 | |
| Download: ML19354A927 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 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) |
| 2782019001R00 - NRC Website | |
text
Exelon Generation.
CCN: 19-142 December 19, 2019 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Subject:
Peach Bottom Atomic Power Station (PBAPS) Unit 3 Renewed Facility Operating License No. DPR-56 NRC Docket No. 50-278 Licensee Event Report (LER) 3-19-001 10CFR 50.73 Enclosed is a Licensee Event Report concerning a condition prohibited by Technical Specifications. In accordance with NEI 99-04, the regulatory commitment contained in this correspondence is to restore compliance with the regulations. The specific methods that have been planned to restore and maintain compliance are discussed in the LER. If you have any questions or require additional information, please do not hesitate to contact Dan Dullum at 717-456-3339.
Patrick D. Navin Site Vice President Peach Bottom Atomic Power Station PDN/dnd/lR 4289548 Enclosure cc:
US NRC, Administrator, Region I US NRC, Senior Resident Inspector R. R. Janati, Commonwealth of Pennsylvania D. Tancabel, State of Maryland B. Watkins, PSE&G, Financial Controls and Co-Owner Affairs
bee:
Sr. Vice President, Mid-Atlantic Operations Site Vice President-PBAPS Plant Manager-PBAPS Director Operations-PBAPS Sr. Mgr. - Operations Spt & Svcs Shift Ops Superintendent - PBABS Operations Support Manager - PBAPS Director, Site Training-PBAPS Manager, PBAPS Operations Training Manager, Regulatory Assurance-PBAPS Sr. Regulatory Assurance Engineer-PBAPS Manager, Licensing Manager, PBAPS Nuclear Oversight - PB, SMB4-5 Commitment Coordinator Director, Mid-Atlantic Licensing Sr. Manager, PRA - Corporate Greenlee, Scot Krueger, Greg INPO Records via IRIS Report (Site OPEX Coordinator)
Records Management - PB
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2018) lhe NRC may not conduct or sponsor. and a person ~ not required 10 respond to. the nformalion collect,on 3.Page Peach Bottom Atomic Power Station Unit 3 05000278 1
OF 3
- 4. Title Failure of Reactor Mode Switch Results in Condition Prohibited by 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 Vear Vear Number No.
Month Day Vear 05000 Facility Name Docket Number 10 21 2019 2019 -
001 0
12 16 2019 05000
- 9. Operating Mode
- 11. This Report is Submitted Pursuant to the Requirements of 1 O CFR §: (Check all that apply)
D 20.2201(b)
D 20.2203(a)(3)(i)
D 50. 73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A)
D 20.2201(d)
D 20.2203(a)(3)(ii)
D 50. 73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B) 1 D
D D
D 20.2203(a)(1) 20.2203(a)(4)
- 50. 73(a)(2)(iii) 50.73(a)(2)(ix)(A)
D 20.2203(a)(2)(i)
D 50.36(c)(1)(i)(A)
D 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x) 1 o. Power Level D 20.2203(a)(2)(ii)
D 50.36(c)(1 )(ii)(A)
D 50.73(a)(2)(v)(A)
D 73.71(a)(4)
D 20.2203(a)(2)(iii)
D 50.36(c)(2)
D 50.73(a)(2)(v)(B)
D 73.71(a)(5)
D 20.2203(a)(2)(iv)
D 50.46(a)(3)(ii)
D 50.73(a)(2)(v)(C)
D 73.77(a)(1) 5%
D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
D 50. 73(a)(2)(v)(D)
D 73.77(a)(2)(i)
D 20.2203(a)(2)(vi)
~ 50.73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 73.77(a)(2)(ii)
D 50.73(a)(2)(i)(C)
D Other (Specify in Abstract below or in
Analysis of Event
SEQUENTIAL NUMBER 001 REV NO.
0 The RPS monitors a number of plant parameters and initiates a reactor scram if the parameters are outside of their expected range. The system consists of two trip systems with two automatic channels and one manual channel per trip system. The Reactor Mode Switch provides input signals to each of the manual channels and causes a scram when placed in the Shutdown position. The Mode Switch also interlocks functions such as control rod blocks and refueling equipment restrictions. In the Shutdown position, it bypasses various scram signals such as the main steam line isolation scram and the main condenser low vacuum scram.
The Mode Switch was last operated during a Unit 3 outage in October of 2018. It was rotated from Run to the Shutdown position on 9/30/18 and operated several times during the outage for control rod testing. It was operated twice during startup, from Shutdown to Startup on 10/9/18 and Startup to Run on 10/10/18. The switch was not used between that time and when it failed on 10/21 /19.
As described further in the Cause section below, the switch failed due to wear. No failure mechanism was identified that caused degradation of the switch when it was not being manipulated and the evidence suggest that it would not have been able to perform its safety function at any time after it was operated on 10/10/18. As a result, the Mode Switch was inoperable from 10/10/18 to 10/21 /19. The Mode Switch is required to be operable by TS 3.3.1.1 (Table 3.3.1.1-1, Function 12). If inoperable, it is required to be restored in one hour or the unit needs to be placed in Mode 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Since these times were exceeded, the event is being reported as a violation of TS in accordance with 1 O CFR 50.73(a)(2)(i)(B).
Although the Mode Switch was inoperable, the overall risk to the plant was very low. The RPS relies primarily on input from instrumentation and performs protective functions automatically, which were not affected by this condition. The Mode Switch is not specifically credited in the accident analysis, but provides overall redundancy and diversity for the RPS. There are several other methods to manually scram the reactor, including the manual scram pushbuttons, which were used successfully.
Cause of the Event
Due to the number of functions the switch controls, there is a large number of electrical contacts that change position when the switch is operated, requiring more force to rotate than is typical for a similar switch. A coupling between the handle and the shaft internal to the switch showed wear and deformation, allowing it slip around the square shaft of the switch.
Corrective Actions
The shaft coupling on the Mode Switch was replaced. Additional corrective actions are documented in the corrective action program.
Previous Similar Occurrences No previous similar occurrences have been identified. Page _3_ of _3_