ML15257A131

LER 15-003-00 for Browns Ferry, Units 1, 2 and 3, Regarding Loss of Cooling to the Unit 1 and Unit 2 Shutdown Board Rooms Due to Fouled Chiller Coils

ML15257A131
Person / Time
Site:	Browns Ferry
Issue date:	09/14/2015
From:	Bono S M Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 15-003-00
Download: ML15257A131 (9)

Text

Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609-2000 September 14, 2015 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Unit 1, 2, and 3 10 CFR 50.73 Renewed Facility Operating License Nos. DPR-33, DPR-52, and DPR-68 NRC Docket Nos. 50-259, 50-260, and 50-296

Subject:

Licensee Event Report 50-259/2015-003-00 The enclosed Licensee Event Report provides details of the inoperability of both Unit 1 and 2 Control Bay Chillers, resulting in a loss of cooling to the Shutdown Board Rooms. The Tennessee Valley Authority (TVA) is submitting this report in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50. 73(a)(2)(v)(A), (B), (C), and (D), as any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to shut down the reactor and maintain it in a safe shutdown condition, remove residual heat, control the release of radioactive material, or mitigate the consequences of an accident. There are no new regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact J. L. Paul, Nuclear Site Licensing Manager, at (256) 729-2636.

Enclosure:

Licensee Event Report 50-259/2015-003-00 -Loss of Cooling to the Unit 1 and Unit 2 Shutdown Board Rooms Due To Fouled Chiller Coils. cc (w/ Enclosure): NRC Regional Administrator -Region II NRC Senior Resident Inspector -Browns Ferry Nuclear Plant ENCLOSURE Browns Ferry Nuclear Plant Unit 1, 2, and 3 Licensee Event Report 50-259/2015-003-00 Loss of Cooling to the Unit 1 and Unit 2 Shutdown Board Rooms Due To Fouled Chiller Coils See Enclosed NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (01-2014) LICENSEE EVENT REPORT (LER) APPROVED BY OMB NO. 3150-0104 EXPIRES 01/31/2017 Estimated 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 />. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection. 1. FACILITY NAME Browns Ferry Nuclear Plant (BFN), Unit 1 2. DOCKET NUMBER 05000259 3. PAGE 1 of 7 4. TITLE: Loss of Cooling to the Unit 1 and Unit 2 Shutdown Board Rooms Due To Fouled Chiller Coils 5. EVENT DATE 6. LER NUMBER 7. REPORT DATE 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL NUMBER REV NO. MONTH DAY YEAR BFN, Unit 2 05000260 7 14 2015 2015 - 003 - 00 9 14 2015 BFN, Unit 3 05000296 9. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 1 20.2201(b) 20.2201(d) 20.2203(a)(1) 20.2203(a)(2)(i) 20.2203(a)(2)(ii) 20.2203(a)(2)(iii) 20.2203(a)(2)(iv) 20.2203(a)(2)(v) 20.2203(a)(2)(vi) 20.2203(a)(3)(i) 20.2203(a)(3)(ii) 20.2203(a)(4) 50.36(c)(1)(i)(A) 50.36(c)(1)(ii)(A) 50.36(c)(2) 50.46(a)(3)(ii) 50.73(a)(2)(i)(A) 50.73(a)(2)(i)(B) 50.73(a)(2)(i)(C) 50.73(a)(2)(ii)(A) 50.73(a)(2)(ii)(B) 50.73(a)(2)(iii) 50.73(a)(2)(iv)(A) 50.73(a)(2)(v)(A) 50.73(a)(2)(v)(B) 50.73(a)(2)(v)(C) 50.73(a)(2)(v)(D) 50.73(a)(2)(vii) 50.73(a)(2)(viii)(A) 50.73(a)(2)(viii)(B) 50.73(a)(2)(ix)(A) 50.73(a)(2)(x) 73.71(a)(4) 73.71(a)(5) OTHER Specify in Abstract below or in NRC Form 366A 10. POWER LEVEL 100 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME Baruch Calkin, Licensing Engineer TELEPHONE NUMBER (Include Area Code) (256) 614-6713 13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT CAUSE SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX CAUSE SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A 14. SUPPLEMENTAL REPORT EXPECTED YES (If yes, complete 15. EXPECTED SUBMISSION DATE) NO 15. EXPECTED SUBMISSION DATE MONTH DAY YEAR N/A N/A N/A ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) outlet water temperature to be higher than specified limits. CB CHLR A was declared inoperable. Because CB CHLR B was concurrently inoperable for maintenance, no chilled water within temperature limits was available to electric board rooms housing Unit 1 and 2 4kV Shutdown Boards, therefore, these boards were declared inoperable. This resulted in a Safety System Functional Failure for safety systems on all three Units. The event also resulted in the loss of two trains of Standby Gas Treatment, and the initiation of a Unit 1, 2, and 3 shutdown in accordance with Technical Specifications (TS) Limiting Conditions for Operation (LCO) 3.0.3. The cause of this event was the failure of plant processes to address increased monitoring following debris/dust-producing events, which allowed fouling of the condenser coils with dirt and insects. Corrective actions include re-evaluating the CB CHLR significance for Probabilistic Risk Assessment calculations, revising procedures for plant equipment susceptible to natural phenomena to enhance inspection during operator rounds, adding walkdown guidance for inspecting and evaluating the condition of the redundant equipment when walking down equipment to be worked, and creating a conditional walkdown requirement on walkdown sheets to check for insect infestation.

NRC FORM 366A LICENSEE EVENT REPORT (LER) U.S. NUCLEAR REGULATORY COMMISSION (02-2014) CONTINUATION SHEET 1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEQUENTIAL NUMBER REVISION NUMBER Browns Ferry Nuclear Plan, Unit 1 05000259 2015 003 00 2 of 7 NARRATIVE NRC FORM 366A (02-2014) outlet water temperature to be higher than specified limits. CB CHLR A was declared inoperable. CB CHLR B had been declared inoperable for planned maintenance on July 13, 2015. The concurrent inoperability of A and B CB CHLR required BFN, Unit 1 and 2 to enter Technical Requirements Manual (TRM) LCO 3.7.6, Electric Board Room Air Conditioning (A/C) System, Condition B. This LCO requires the unit, with two Unit 1 and 2 electric board room A/C subsystems inoperable, to declare the electrical equipment in the electric board rooms inoperable immediately. For BFN, Unit 1 and 2, all four 4160 V (4kV) Shutdown Boards (SDBs)[ECBD] were declared inoperable. BFN, Unit 1 and 2, declared DG A, DG B, DG C, and DG D inoperable. BFN, Unit 1 and 2, declared SGT A, SGT B, and CREV A inoperable. With SGT A and B inoperable, BFN, Unit 1, 2, and 3, entered TS LCO 3.6.4.3, SGT System, Condition D. This LCO requires, with two or three SGT subsystems inoperable in MODE 1, 2, or 3, that the unit enter TS LCO 3.0.3 immediately. BFN, Units 1, 2, and 3, entered TS LCO 3.0.3 with required action within one hour to initiate action to place Unit 1, 2, and 3 in MODE 2 within 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />, in MODE 3 in 13 Hours, and in MODE 4 in 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br />. On -Title 10 of the Code of Federal Regulations NRC FORM 366A LICENSEE EVENT REPORT (LER) U.S. NUCLEAR REGULATORY COMMISSION (02-2014) CONTINUATION SHEET 1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEQUENTIAL NUMBER REVISION NUMBER Browns Ferry Nuclear Plan, Unit 1 05000259 2015 003 00 3 of 7 NARRATIVE NRC FORM 366A (02-2014) outlet water temperature stabilized within operable limits. - No component failures were identified that occurred during the event.

NRC FORM 366A LICENSEE EVENT REPORT (LER) U.S. NUCLEAR REGULATORY COMMISSION (02-2014) CONTINUATION SHEET 1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEQUENTIAL NUMBER REVISION NUMBER Browns Ferry Nuclear Plan, Unit 1 05000259 2015 003 00 4 of 7 NARRATIVE NRC FORM 366A (02-2014) of discovery of each component or system failure or procedural error: The failure of CB CHLR A was discovered when the outlet water temperature was observed by Operations personnel to be 47 degrees Fahrenheit (F), which is greater than the maximum allowable chilled water outlet temperature of 44 degrees F. The failure mode, mechanism, and effect of each failed component, if known: There were no failed components related to this event. H. Operator actions: Identified chilled water outlet temperature was out of band, declared outlet water temperature returned to operable band following inspection and cleaning, declared CB CHLR operable, exited TS LCO 3.0.3. I. Automatically and manually initiated safety system responses: There were no automatic or manual safety responses associated with this event.

NRC FORM 366A LICENSEE EVENT REPORT (LER) U.S. NUCLEAR REGULATORY COMMISSION (02-2014) CONTINUATION SHEET 1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEQUENTIAL NUMBER REVISION NUMBER Browns Ferry Nuclear Plan, Unit 1 05000259 2015 003 00 5 of 7 NARRATIVE NRC FORM 366A (02-2014) The cause of each component or system failure or personnel error, if known: The apparent cause of this event was the failure of plant processes to address increased monitoring following debris/dust-producing events, which allowed fouling of the condenser coils with dirt (from onsite construction and excavation activities), and insects (from a large willow fly hatch). The direct cause of this event was a lack of existing actions to address natural phenomena affecting plant equipment. There are no routine actions that System Engineers, Operators, or Maintenance personnel take to respond to a natural occurrence, such as a willow fly hatch, which can negatively impact operation of critical plant equipment. The cause(s) and circumstances for each human performance related root cause: There were no human performance root causes associated with this event. The Tennessee Valley Authority (TVA) is submitting 10 CFR 50.73(a)(2)(v)(A), (B), (C), and (D), as any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to shut down the reactor and maintain it in a safe shutdown condition, remove residual heat, control the release of radioactive material, or mitigate the consequences of an accident. This event resulted from fouling of the CB CHLR A condenser coils by dirt from onsite construction and excavation activities, and by insects from a seasonal willow fly hatch. This fouling caused the inoperability of the chiller, concurrent with a second Unit 1 and 2 chiller which was already inoperable for maintenance. Equipment in electric board rooms rely on chilled water from this system for proper functioning in all conditions, including accident conditions. Therefore, all Unit 1 and 2 4kV SDBs and associated diesels were declared inoperable along with the chiller. The safety function of the 4kV SDBs, as part of the Standby AC Power System, is to provide a self-contained, highly reliable source of power, as required for the Engineered Safeguards System, so that no single credible event can disable the core standby cooling functions or their supporting auxiliaries. Inoperability of the Unit 1 and 2 4kV SDBs and diesels caused the loss of several safety systems and the required initiation of plant shutdown for BFN Units 1 and 2. The loss of two trains of SGT also caused the required initiation of a Unit 3 shutdown. inoperability of all four Unit 1 and 2 4kV SDBs and their associated DGs; however the equipment remained available during the event. This equipment was declared inoperable because it was unable to perform its safety function under all design basis conditions for supplying reliable power to safety-related equipment in order to shut down the reactor and maintain it in a safe shutdown condition, remove residual heat, NRC FORM 366A LICENSEE EVENT REPORT (LER) U.S. NUCLEAR REGULATORY COMMISSION (02-2014) CONTINUATION SHEET 1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEQUENTIAL NUMBER REVISION NUMBER Browns Ferry Nuclear Plan, Unit 1 05000259 2015 003 00 6 of 7 NARRATIVE NRC FORM 366A (02-2014) control the release of radioactive material, or mitigate the consequences of an accident. The 4kV SDBs are located in the Unit 1 and 2 Electric Board Rooms (EBR). Total system failure could result if the equipment operating temperature in the EBRs exceeded the 104 degree F operability limit. During this event non-qualified temporary cooling was available to ensure the temperature in the EBR would not exceed the 104 degree F operability limit of the associated safety-related components. Therefore, during the time period that the 4kV SDBs were inoperable, sufficient systems were available to provide the required safety functions to protect the health and safety of the public. During this event non-qualified temporary cooling was available to ensure the temperature in the EBR would not exceed the 104 degree F operability limit of the associated safety-related components. This event resulted in inoperability of multiple plant safety systems for approximately seven hours, from 1715 CDT when the CB CHLR A chilled water high temperature was discovered until 2352 CDT when the CB CHLR A condenser coils were cleaned and the unit was returned to normal operation. VI. Corrective Actions: Condition Report (CR) 1056829. The following corrective actions are in progress: 1. Add guidance for maintenance walkdown crews to inspect and evaluate the condition of redundant equipment when walking down equipment to be worked. 2. Develop a list of plant equipment susceptible to natural phenomena and revise procedures to enhance equipment inspection during operator rounds. 3. Create conditional walkdown requirements on walkdown sheets to check for insect infestation. 4. Re-evaluate the most recent Probabilistic Risk Assessment calculation revision involving CB CHLRs in order to determine if the current CB CHLR Equipment Reliability Classification is appropriate.

NRC FORM 366A LICENSEE EVENT REPORT (LER) U.S. NUCLEAR REGULATORY COMMISSION (02-2014) CONTINUATION SHEET 1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEQUENTIAL NUMBER REVISION NUMBER Browns Ferry Nuclear Plan, Unit 1 05000259 2015 003 00 7 of 7 NARRATIVE NRC FORM 366A (02-2014) A. B. There is no additional information. - a. b. c. d. - D. There are no new commitments.