05000454/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
| ML16124A048 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 05/03/2016 |
| From: | Kanavos M Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BYRON 2016-0046 LER 16-001-00 | |
| Download: ML16124A048 (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)(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)(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) 10 CFR 50.73(a)(2)(i) |
| 4542016001R00 - NRC Website | |
text
Byron Generating Station 4450 North German Church Road Exe1.0n Generat ion May 3,2076 LTR:
BYRON 207 6-0046 File:
7.10.0101 (1D.101) 2.07.01 00 (5A.108)
United States Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0007 Byron Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455
Subject:
Licensee Event Report (LER) No. 454-2016-001 -00, 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 Enclosed is Byron Station Licensee Event Report (LER) No. 454-2016-001-00 regarding an unanalyzed condition due to insufficient validation of vendor analysis inputs for the Auxiliary Feedwater diesel combustion air intake. This condition is being submitted in accordance with 10 CFR 50.73, Licensee Event Report System.
There are no regulatory commitments in this report.
Should you have any questions concerning this submittal, please contact Mr. Douglas Spitzer, Regulatory Assurance Manager, at (815) 406-2800.
Respectfully, Mark E. Kanavos Site Vice President Byron Generating Station MEK/GC/sg
Enclosure:
LER 454-201 6-007 -00 cc:
Regional Administrator NRC Region Ill NRC Senior Resident Inspector Byron Generating Station
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 10/31/2018 (11-2015)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Byron Station Unit 1 05000454 7
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. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED v
FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEAL MONTH DAY YEAR Byron Station Unit 2 05000455 FACILITY NAME DOCKET NUMBER 03 04 16 2016 001 00 05 03 16 N/A N/A
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
LI 20.2201(b)
LI 20.2203(a)(3)Ø)
LI 50.73(a)(2)(ii)(A)
LI 50.73(a)(2)(viii)(A)
LI 20.2201(d)
LI 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(B)
LI 50.73(a)(2)(viii)(B) 1 (both units)
LI 20.2203(a)(1)
LI 20.2203(a)(4)
LI 50.73(a)(2)(iii)
LI 50.73(a)(2)(ix)(A)
LI 20.2203(a)(2)(i)
LI 50.36(c)(1)(i)(A)
LI 50.73(a)(2)(iv)(A)
LI 50.73(a)(2)(x)
- 10. POWER LEVEL LI 2o.2203(a)f2)ti)
[] 50.36(c)(1)(ii)(A)
LI 50.73(a)f2)(v)(A)
LI 73.71(a)(4)
LI 20.2203(a)(2)(ii)
LI 50.36(c)(2) 50.73(a)(2)(v)(B)
LI 73.71(a)(5)
LI 20.2203(a)(2)(iv)
LI 50.46(a)(3)Øi)
LI 50.73(a)(2)(v)fC)
LI 73.77(a)(1) 100% (both units)
LI 20.2203(a)(2)(v)
LI 50.73(a)(2)(i)(A)
LI 50.73(a)(2)(v)f0)
LI 73.77(a)(2)(i)
LI 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B)
LI 50.73(a)(2)(vH)
LI 73.77(a)(2)(ii)
LI 50.73(a)(2)(i)(C)
LI 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 FW HELB was insufficient validation of vendor analysis inputs in 1993 while reviewing the AF diesel engines ability to function during a turbine building 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 per(orm any independent reviews or analysis to verify the vendors conclusion.
D. Safety Consequences
This condition had no actual safety consequences impacting plant or public safety since Byron Station has not experienced a turbine building HELB event.
During a postulated design basis Main Feedwater (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 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
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 Byron on this issue.
G. Component Failure Data
Manufacturer Nomenclature Model Mfg. Part Number N/A N/A N/A N/A
A. Plant Operating Conditions Before the Event
Event Date:
March 4, 2016 Unit:
1 Mode:
1 Reactor Power: 100 percent Unit: 2 Mode:
1 Reactor Power: 100 percent Unit 1 Reactor Coolant System (RCS) [AB]:
Normal operating temperature and pressure Unit 2 Reactor Coolant System:
Normal operating temperature and pressure 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 Braidwood NRC Component Design Basis Inspection, a concern was raised regarding why it was acceptable for the diesel driven auxiliary feedwater (AF) [BA] 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 room.
During the review of documentation related to the air intake for Byron Station, 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.
This issue was determined to be applicable to Byron Station and on March 7, 2016 at 0400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br />, Byron 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 Notification51772 was made on March 7, 2016 at 1118 hours0.0129 days <br />0.311 hours <br />0.00185 weeks <br />4.25399e-4 months <br />.
A temporary configuration change was implemented to provide engine combustion intake air 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 8, 2016, following the installation of changes, the Byron 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 rooms.
This condition is reportable in accordance with 10CFR5O.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 10 CFR 50.73(a)(2)(v)(B) as a condition that could have prevented the fulfillment of a systems safety function.
C. Cause of Event
The cause of the condition of inadequate combustion air available for AF diesel engine operation during a FW HELB was insufficient validation of vendor analysis inputs in 1993 while reviewing the AF diesel engines ability to function during a turbine building 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 per(orm any independent reviews or analysis to verify the vendors conclusion.
D. Safety Consequences
This condition had no actual safety consequences impacting plant or public safety since Byron Station has not experienced a turbine building HELB event.
During a postulated design basis Main Feedwater (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 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
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 Byron on this issue.
G. Component Failure Data
Manufacturer Nomenclature Model Mfg. Part Number N/A N/A N/A N/A