05000456/LER-2016-001, Regarding Auxiliary Feedwater Diesel Intake Design Deficiency Related to Turbine Building High Energy Line Break Resulted in an Unanalyzed Condition Due to Insufficient Validation of Vendor Analysis Inputs
| ML16119A296 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 04/28/2016 |
| From: | Marchionda-Palmer M Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BW160030 LER 16-001-00 | |
| Download: ML16119A296 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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)(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 |
| 4562016001R00 - NRC Website | |
text
n Exelon Generation Company, LLC Braidwood Station 35100 South Route 53, Suite 84 Braceville, IL 60407-9619 April 28, 2016 BW160030 ti n www.exeloncorp.com U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Braidwood Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456 and STN 50-457 10 CFR 50.73
Subject:
Licensee Event Report 2016-001 Auxiliary Feedwater Diesel Intake Design Deficiency Related to Turbine Building High Energy Line Break Resulted in an Unanalyzed Condition Due to Insufficient Validation of Vendor Analysis Inputs The enclosed Licensee Event Report (LEA) is being submitted in accordance with 1 O CFR 50. 73, "Licensee Event Report System."
There are no regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact Mr. Steven Reynolds, Regulatory Assurance Manager, at (815) 417-28~~* ~*
Respectfully, 1~.~
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\\~1 \\Ql~~
\\;\\ \\ Marri Marchionda-~er
~ Site Vice President 'J Braidwood Station
Enclosure:
LER 2016-001-00 cc: NRR Project Manager - Braidwood Station Illinois Emergency Management Agency - Division of Nuclear Safety US NRC Regional Administrator, Region Ill US NRC Senior Resident Inspector (Braidwood Station)
Illinois Emergency Management Agency-Braidwood Representative
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2018 (11-2015)
\\J'-"JlltQ"<.,
, the NRG may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Braidwood Station, Unit 1 05000456 1 OF 4
- 4. TITLE Auxiliary Feedwater Diesel Intake Design Deficiency Related to Turbine Building High Energy Line Break Resulted in an Unanalyzed Condition Due to Insufficient Validation of Vendor Analysis Inputs
- 5. EVENT DATE
- 6. LEA NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.
MONTH DAY YEAR Braidwood Station, Unit 2 05000457 FACILITY NAME DOCKET NUMBER 03 04 2016 2016 - 001
- - 00 04 28 2016 N/A N/A
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
D 20.2201 (bl D 20.2203(a)(3)(il D 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A) 1 D 20.2201 (dl D 20.2203(a)(3Hiil [8l 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
D 20.2203(a)(1)
D 20.2203(a)(4)
D so.13(a)(2)(m)
D 50.73(a)(2)(ix)(A)
D 20.2203(a)(2Hil D 50.36(c)(1 )(i)(A)
D 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
- 10. POWER LEVEL D 20.2203(a)(2)(n)
D 50.36(c)(1 )(ii)(A)
D 50.73(a)(2)(v)(A)
D 13.11(a)(4)
D 20.2203(a)(2)(iiil D so.36(c)(2l [8] 50.73(a)(2)(v)(B)
D 13.11 <aHsi D 20.2203(a)(2)(iv)
D so.46(a)(3)(iil D 50.73(a)(2)(v)(C)
D 13.11(a)(1 i 100 D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
D 50.73(a)(2)(v)(D)
D 13.11(a)(2)(i)
D 20.2203(a)(2)(vi)
[8l 50.73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 13.77(a)(2)(iil D so.13(a)(2)(i)(C)
D OTHER Specify in Abstract below or in
C. Cause of Event
The cause of the condition of inadequate combustion air available for AF diesel engine operation during a main feedwater (FW) [SJ] HELB was insufficient validation of vendor analysis inputs in 1993 while reviewing the AF diesel engine's ability to function during a HELB event. The technical error originated from the AF diesel engine manufacturer. An engineering product that was completed in 1993 utilized the vendor input as a fact and did not perform any independent reviews or analysis to verify the vendor's conclusion.
D. Safety Consequences
This condition had no actual safety consequences impacting plant or public safety since Braidwood Station has not experienced a turbine building HELB event.
During a postulated design basis FW HELB event in the turbine building, the diesel-driven AF pump may not be functional due to the lack of oxygen available at the combustion air intake located in the turbine building. Included in the design basis event is a single active failure of the motor-driven A-train AF pump which would result in the loss of safety function of the AF system. During this postulated event, the RCS would heat up and the resultant volume expansion would begin filling the pressurizer. Station procedures include steps to restore AF flow or a non-safety related water supply to the secondary-side of the steam generators. If all attempts to restore a secondary heat sink are unsuccessful, "feed and bleed" operations would be implemented to cool the RCS while secondary heat sink restoration efforts continued.
The adverse turbine building conditions would be present for a limited duration based on the finite volume in the secondary water systems and the ability to manually isolate a postulated pipe break. As the turbine building conditions return to normal, air would become available at the diesel-driven AF pump combustion air intake and AF flow would be restored to the steam generators if required.
This event has a low safety significance based on the historical availability of the A-train AF pump, the limited population of secondary pipe breaks (low probability of occurrence) which would adversely affect the B-train AF pump, and the ability to restart the B-train AF pump when the turbine building conditions return to normal.
E. Corrective Actions
Interim Corrective Actions Completed -A temporary configuration change was completed to provide engine combustion air intake from the auxiliary building, and install a wire mesh screen cap to prevent incidental intrusion of debris into the air intake. Additionally, compensatory measures were implemented to monitor for a potential radioactive material release from the engine exhaust to the atmosphere and to institute a fire watch due to the configuration change disabling the C02 system and opening the doors for the AF diesel rooms.
Corrective Actions planned - Develop and install a permanent modification to re-route the AF diesel engine intakes for Unit 1 and 2.
F. Previous Occurrences
There have been no previous Licensee Event Reports at Braidwood on this issue.
G. Component Failure Data
Manufacturer Nomenclature NIA NIA NIA
A. Plant Operating Conditions Before the Event
Event Date:
Unit: 1 Unit: 2 March 4, 2016 Mode: 1 Mode: 1 Reactor Power: 100 percent Reactor Power: 100 percent YEAR 2016 Unit 1 Reactor Coolant System (RCS) [AB]: Normal operating temperature and pressure Unit 2 Reactor Coolant System:
Normal operating temperature and pressure SEQUENTIAL NUMBER 001 REV NO.
00 No structures, systems or components were inoperable at the start of this event that contributed to the event.
B. Description of Event
On March 4, 2016, during the NRC Component Design Basis Inspection, a concern was raised regarding why it was acceptable for the diesel-driven auxiliary feedwater (AF) [BAJ pump engine combustion air intake to be located in the turbine building, a non-safety related structure. Combustion air intake draws air from the turbine building via an intake pipe that enters the safety-related auxiliary building to the AF diesel-driven pump room.
On March 6, 2016, during the review of documentation related to the combustion air intake, it was identified that the existing configuration did not adequately support diesel engine operation with high energy line break (HELB) environmental conditions in the turbine building. Prior evaluations did not fully account for the combustion air being a steam-air mixture in a post-HELB environment that reduces the available air density during the event.
On March 6, 2016 at 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br />, Operations entered Technical Specification (TS) Limiting Condition for Operation (LCO) 3.7.5, "Auxiliary Feedwater (AF) System," Condition A, "One AF train inoperable," for one train (B-train) of AF inoperable, for both Units 1 and 2. NRC Event Notification51771 was made on March 7, 2016 at 0100 CST.
A temporary configuration change was implemented to provide engine combustion air intake from the auxiliary building. The change allowed air from the AF diesel-driven pump rooms to supply the Unit 1 and Unit 2 AF diesel engines and a wire mesh screen cap was installed to prevent incidental intrusion of debris that could be present in the proximity of the air intake. On March 7, 2016, following the installation of changes, the AF trains were declared operable. Additionally, compensatory measures were implemented to 1) monitor for a potential radioactive material release from the engine exhaust to the atmosphere, and 2) institute a fire watch due to the configuration change disabling the C02 system and opening the doors for the AF diesel-driven pump rooms.
This condition is reportable in accordance with 10CFR50.73(a)(2)(ii)(B), any event or condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety. Additionally, TS LCO 3.7.5 Condition A requires restoring the AF train to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. As the AF combustion air intake was installed per the original plant design, this condition existed for a longer period of time than is allowed by LCO 3.7.5 Condition A. Therefore, this event is also being reported pursuant to 10 CFR 50.73(a)(2)(i)(B), any operation or condition which was prohibited by TSs. Further, as there were multiple times during the past three years where the Unit 1 and Unit 2 A-train AF system were inoperable for surveillance testing, this event is also being reported pursuant to 1 O CFR 50.73(a)(2)(v)(B) as a condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat.
C. Cause of Event
The cause of the condition of inadequate combustion air available for AF diesel engine operation during a main feedwater (FW) [SJ] HELB was insufficient validation of vendor analysis inputs in 1993 while reviewing the AF diesel engine's ability to function during a HELB event. The technical error originated from the AF diesel engine manufacturer. An engineering product that was completed in 1993 utilized the vendor input as a fact and did not perform any independent reviews or analysis to verify the vendor's conclusion.
D. Safety Consequences
This condition had no actual safety consequences impacting plant or public safety since Braidwood Station has not experienced a turbine building HELB event.
During a postulated design basis FW HELB event in the turbine building, the diesel-driven AF pump may not be functional due to the lack of oxygen available at the combustion air intake located in the turbine building. Included in the design basis event is a single active failure of the motor-driven A-train AF pump which would result in the loss of safety function of the AF system. During this postulated event, the RCS would heat up and the resultant volume expansion would begin filling the pressurizer. Station procedures include steps to restore AF flow or a non-safety related water supply to the secondary-side of the steam generators. If all attempts to restore a secondary heat sink are unsuccessful, "feed and bleed" operations would be implemented to cool the RCS while secondary heat sink restoration efforts continued.
The adverse turbine building conditions would be present for a limited duration based on the finite volume in the secondary water systems and the ability to manually isolate a postulated pipe break. As the turbine building conditions return to normal, air would become available at the diesel-driven AF pump combustion air intake and AF flow would be restored to the steam generators if required.
This event has a low safety significance based on the historical availability of the A-train AF pump, the limited population of secondary pipe breaks (low probability of occurrence) which would adversely affect the B-train AF pump, and the ability to restart the B-train AF pump when the turbine building conditions return to normal.
E. Corrective Actions
Interim Corrective Actions Completed -A temporary configuration change was completed to provide engine combustion air intake from the auxiliary building, and install a wire mesh screen cap to prevent incidental intrusion of debris into the air intake. Additionally, compensatory measures were implemented to monitor for a potential radioactive material release from the engine exhaust to the atmosphere and to institute a fire watch due to the configuration change disabling the C02 system and opening the doors for the AF diesel rooms.
Corrective Actions planned - Develop and install a permanent modification to re-route the AF diesel engine intakes for Unit 1 and 2.
F. Previous Occurrences
There have been no previous Licensee Event Reports at Braidwood on this issue.
G. Component Failure Data
Manufacturer Nomenclature NIA NIA NIA YEAR 2016 -
SEQUENTIAL NUMBER 001 Mfg. Part Number NIA REV NO.
00