05000277/LER-2010-004, Regarding Improper Credit for Function of Off-Site Power Source Transformer Load Tap Changer
| ML103280505 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 11/24/2010 |
| From: | Stathes G Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 10-004-00 | |
| Download: ML103280505 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 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)(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)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2772010004R00 - NRC Website | |
text
Exelon.
Exelon Nuclear www.exeloncorp.com Nuclear Peach Bottom Atomic Power Station 1848 Lay Rd.
Delta, PA 17314 10CFR 50.73 November 24, 2010 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Peach Bottom Atomic Power Station (PBAPS) Units 2 and 3 Facility Operating License Nos. DPR-44 and DPR-56 NRC Docket Nos. 50-277 and 50-278
Subject:
Licensee Event Report (LER) 2-10-04 Enclosed is a Licensee Event Report concerning a condition involving various plant equipment that were considered inoperable due to improper credit given to the operation of an off-site power source transformer load tap changer. In accordance with NEI 99-04, the regulatory commitment contained in this correspondence is to restore compliance with the regulations.
The specific methods that are 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 us.
Sincerely, Garey L. Stathes Plant Manager Peach Bottom Atomic Power Station GLS/djf/IR 1119440 / 1125359 / 762371 Attachment cc:
US NRC, Administrator, Region I US NRC, Senior Resident Inspector R. R. Janati, Commonwealth of Pennsylvania S. Grey, State of Maryland P. Steinhauer, PSE&G, Financial Controls and Co-owner Affairs INPO Records Center CCN: 10-95
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)
, the NRC may sfor each block) not conduct or sponsor, and a person is not required to respond to, the digits/characters finformation collection.
- 3. PAGE Peach Bottom Atomic Power Station (PBAPS) Unit 2 05000277 1 OF 6
- 4. TITLE Improper Credit for Function of Off-Site Power Source Transformer Load Tap Changer
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NO.
MONTH DAY YEAR PBAPS Unit 3 05000278 IFACILITY NAME DOCKET NUMBER 09 29 2010 10 004 00 11 24 2010 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMI'TED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
El 20.2201(b)
El 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii) 5 El 20.2201(d)
[I 20.2203(a)(3)(ii)
El 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
El 20.2203(a)(1)
El 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
[I 50.73(a)(2)(viii)(B)
El 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii)
[I 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
[I 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
El 50.36(c)(2) 0l 50.73(a)(2)(v)(A)
E] 73.71(a)(4) 0%
El 20.2203(a)(2)(iv)
Cl 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71(a)(5)
El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
E] OTHER El 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in Description of the Event, continued Common to Units 2 and 3:
- 1. Limiting Condition for Operation (LCO) 3.8.1, AC Sources - Operating - Because the MCC contactors for the following equipment were in a non-conforming condition, a condition prohibited by TS LCO 3.8.1 is considered to have occurred (10CFR 50.73(a)(2)(i)(B)):
O E-1 EDG Ventilation Supply Fan (0AV064) motor O E-1 EDG Fuel Oil Transfer Pump (OAP060) motor O E-3 EDG Supplemental Ventilation Fan (OCV091) motor O E-4 EDG Ventilation Supply Fan (0DV064) motor Unit 2:
- 1. LCO 3.5.1, Emer-gency Core Coolinq Systems (ECCS) and Reactor Core Isolation Cooling (RCIC) System - Because the MCC contactor for the 2B Core Spray Room Cooler Fan (2FV024) motor was in a non-conforming condition, a condition prohibited by TS LCO 3.5.1 is considered to have occurred (10CFR 50.73(a)(2)(i)(B)).
In accordance with the PBAPS Technical Requirements Manual Section 3.11, Engineered Safeguards (ES) Compartment Cooling and Ventilation, the associated Core Spray pump is required to be declared inoperable if the associated room cooler unit is inoperable. Therefore, the non-conforming condition of the 2B Core Spray Room Cooler would have resulted in an entry into the appropriate conditions of TS LCO 3.5.1 for an inoperable low pressure ECCS subsystem being inoperable.
- 2. LCO 3.6.2.3, Residual Heat Removal (RHR) Suppression Pool Cooling and LCO 3.6.2.4.,
Residual Heat Removal (RHR) Suppression Pool Spray -
Because the motor MCC contactors / motor-operators for the following valves were in a non-conforming condition, a condition prohibited by TS LCOs 3.6.2.3 and 3.6.2.4 is considered to have occurred (10CFR 50.73(a)(2)(i)(B)):
o 2B RHR Suppression Pool Cooling Valve (MO-2-10-034B) - MCC contactor o
2A RHR Pump Discharge Valve (MO-2-10-154A) - motor-operator o
2B RHR Pump Discharge Valve (MO-2-10-154B) - motor-operator The 2B RHR Suppression Pool Cooling Valve is required to open to provide a flow path for Suppression Pool Cooling and Suppression Pool Spray.
The 2A and 2B RHR Pump Discharge Valves (pressure isolation valves) are required to close after the Low Pressure Coolant Injection (LPCI) mode of RHR has performed its function in order to line the system up for Suppression Pool Cooling / Spray.
Description of the Event, continued
- 3. LCO 3.6.1.3. Primary Containment Isolation Valves (PCIVs) - Because the MCC contactors for the motors for the following valves were in a non-conforming condition, a condition prohibited by TS LCO 3.6.1.3 is considered to have occurred (10CFR 50.73(a)(2)(i)(B)):
o 2B RHR Suppression Pool Cooling Valve (MO-2-10-034B) o 2B RHR Drywell Spray Inboard Isolation Valve (MO-2-10-031B)
If the above normally-closed valves were opened to perform their Suppression Pool Cooling
/ Suppression Pool Spray / Drywell Spray function, it could not be assured the valves could be re-closed while in the non-conforming condition.
- 4. LCO 3.7.1, High Pressure Service Water (HPSW) System - Because the MCC contactor for the 2A HPSW / Emergency Service Water (ESW) area exhaust fan (2AV083) motor was in a non-conforming condition, a condition prohibited by TS LCO 3.7.1 is considered to have occurred (10CFR 50.73(a)(2)(i)(B)). In accordance with the PBAPS Technical Requirements Manual Section 3.11, Engineered Safeguards (ES) Compartment Cooling and Ventilation, the associated HPSW subsystem is required to be declared inoperable if the associated area exhaust fan is inoperable. Therefore, the non-conforming condition of the 2A HPSW /
ESW area exhaust fan would have resulted in an entry into the appropriate conditions of TS LCO 3.7.1 for an inoperable HPSW subsystem.
Unit 3:
- 1. LCO 3.6.1.3. Primary Containment Isolation Valves (PCIVs)-
Because the MCC contactors
/ motor-operator for the following valves were in a non-conforming condition, a condition prohibited by TS LCO 3.6.1.3 is considered to have occurred (10CFR 50.73(a)(2)(i)(B)):
o 3B RHR Suppression Pool Cooling Valve (MO-3-10-034B) - MCC contactor o
3B RHR Drywell Spray Inboard Isolation Valve (MO-3-10-031B) - MCC contactor o
3B RHR Drywell Spray Outboard Isolation Valave (MO-3-10-026B) - motor-operator If the above normally-closed valves were opened to perform their Suppression Pool Cooling
/ Suppression Pool Spray / Drywell Spray function, it could not be assured the valves could be closed while in the non-conforming condition.
- 2. LCO 3.6.2.3, Residual Heat Removal (RHR) Suppression Pool Cooling and LCO 3.6.2.4, Residual Heat Removal (RHR) Suppression Pool Spray - Because the motors for the MCC contactors / motor-operators for the following valves were in a non-conforming condition, a
,condition prohibited by TS LCOs 3.6.2.3 and 3.6.2.4 is considered to have occurred (10CFR 50.73(a)(2)(i)(B)):
O 3B RHR Suppression Pool Cooling Valve (MO-3-10-034B) - MCC contactor o
3A RHR Pump Discharge Valve (MO-3-10-154A) - motor-operator o
3B RHR Pump Discharge Valve (MO-3-10-154B) - motor-operator
Description of the Event, continued The 3B RHR Suppression Pool Cooling Valve is required to open to provide a flow path for Suppression Pool Cooling and Suppression Pool Spray.
The 3A and 38 RHR Pump Discharge Valves (pressure isolation valves) are required to close after the Low Pressure Coolant Injection (LPCI) mode of RHR has performed its function in order to line the system up for Suppression Pool Cooling / Spray.
Cause of the Event
The plant engineering staff (utility, non-licensed) had previously assumed that credit could be taken in the design basis for the operation of the load tap changers associated with the offsite power source transformers. This was based on the incorrect assumption that this credit had been found acceptable as part of the licensing associated with Technical Specification amendment 143/145 that was approved by the NRC on 4/13/89. It was determined that the individual component design bases must be determined without reliance on the load tap changers and must use voltages associated with the TS 3.3.8.1 Loss of Power (LOP)
Instrumentation Degraded Voltage LOCA relay allowable value.
Analysis of the Event
There were no actual safety consequences associated with this event. This condition has been determined to be of very low safety significance. Analyses performed by NRC personnel have determined that this design deficiency impacted operability but not functionality of the affected equipment. There was no loss of safety function involved with this design deficiency. There were no affects on the ability of the offsite power system (EIIS: EA) to maintain adequate voltage during a design basis LOCA.
Two qualified circuits between the offsite transmission network and the onsite Class 1 E electrical power distribution system (EIIS: EK) are supported by multiple, independent power sources. The voltage of the three offsite sources that are available to the two qualified circuits is stepped down using transformers that are equipped with load tap changers. These load tap changers automatically adjust the transformers (EIIS: XRMR) to produce sufficient voltage to supply the onsite power distribution network. The load tap changers, although not considered as safety related, are highly reliable.
The onsite power distribution network is equipped with loss of power instrumentation (EIIS:
RLY) that monitors incoming bus voltage.
This monitoring equipment can detect degraded voltage / loss of voltage and initiate actions to transfer the associated onsite distribution network buses from the qualified offsite circuits to the onsite EDGs.
Analysis of the Event, continued The non-conforming condition had no impact on the LOCA / loss-of-offsite power design basis event.
The only impact this condition had was on LOCA events that involved a degraded voltage event where the voltage did not go low enough to transfer to the EDGs, but was not high' enough to power all required equipment. Due to the extreme low likelihood of this postulated design basis event, the event was not considered to be risk significant.
Corrective Actions
Components with affected MCC contactors that directly impacted TS have been upgraded.
An operability evaluation was promptly completed for other valves that require upgrading of the associate motor-operator. Compensatory measures were put in place to ensure operability until design margin improvements can be made. These compensatory measures include procedural controls to verify appropriate voltages exist prior to operating the associated valves.
Appropriate design upgrades will be performed for affected components.
Other components that did not directly impact TS operability are also being evaluated for upgrades.
Previous Similar Occurrences There were no previous similar events identified.