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{{Adams
#REDIRECT [[05000373/LER-2014-001]]
| number = ML14121A079
| issue date = 04/18/2014
| title = LER 14-001-00 for LaSalle County Station, Units 1 & 2 Regarding Secondary Containment Inoperable Due to Interlock Doors Open
| author name = Vinyard H T
| author affiliation = Exelon Generation Co, LLC
| addressee name =
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000373, 05000374
| license number = NPF-011, NPF-018
| contact person =
| case reference number = RA14-013
| document report number = LER 14-001-00
| document type = Letter, Licensee Event Report (LER)
| page count = 6
}}
 
=Text=
{{#Wiki_filter:Ad o LaSalle Station A2601 North 21st Road Exelon Generation Marseilles, IL 61341 815 415 2000 Telephone www.exeloncorp.com 10 CFR 50.73 RA14-013 April 18, 2014 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 LaSalle County Station, Units 1 and 2 Facility Operating License Nos. NPF-1 1 and NPF-1 8 NRC Docket Nos. 50-373 and 50-374
 
==Subject:==
Licensee Event Report 2014-001-00 Secondary Containment Inoperable Due to Interlock Doors Open In accordance with 10 CFR 50.73(a)(2)(v)(C) and (D), Exelon Generation Company (EGC), LLC, is submitting Licensee Event Report Number 2014-001-00 for LaSalle County Station Units 1 and 2.There are no regulatory commitments in this letter. Should you have any questions concerning this report, please contact Mr. Guy V. Ford, Regulatory Assurance Manager, at (815) 415-2800.Respectfully, Harold T. Vinyard Plant Manager LaSalle County Station
 
==Enclosure:==
 
Licensee Event Report cc: Regional Administrator
-NRC Region III NRC Senior Resident Inspector
-LaSalle County Station NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 01/31/2017 (02-2014)Estimated burden per response to comply with this mandatory collection request 80 hours.Reported lessons learned are incorporated into the lcensing process and fed back to industry.Send comments regarding burden estimate to the FOIA, Privacy and Infornation Collections LICENS EEVENT REPORT (LER) Branch (1-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by L intemet e-mail to Infocollects.Resourcefnrtgov, and to the Desk Officer, Office of Information and (See Page 2 for required number of Regulaty Affirs, NEOB-1 02OZ (3150-0104), Oce of Management and Budget, Washington, DC ,. .e for each block) 2o3. f a means used to impose an informnaton collection does not display a cunently valid OMB digits/characters focontrol number, the NRC may not conduct or sponsor, and a person is not requred to respond to, the information collection.
: 1. FACIUTY NAME 2. DOCKET NUMBER 3. PAGE LaSalle County Station Unit 1 05000373 1 --OF 5" 4. TITLE Secondary Containment Inoperable Due to Interlock Doors Open 5. EVENT DATE 6. LER NUMBER 7. REPORT DATE S. OTHER FACILTIES INVOLVED I FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NEUMENTIA NO.-E MONTH DAY YEAR LaSalle C. yountySainUit20007 Station Unit 2 05000374 FACILITY NAME DOCKET NUMBER 02 18 2014 2014 -001 -00 04 21 2014 05000 9. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)El 20.2201(b)
El 20.2203(a)(3)(i)
[] 50.73(a)(2)(i)(C)
C] 50.73(a)(2)(vii)
El 20.2201(d)
[] 20.2203(a)(3)(ii)
El 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
E] 20.2203(a)(1)
El 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
_ _ 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii)
El 50.73(a)(2)(ix)(A)
: 10. POWER LEVEL El 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
El 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
El 20.2203(a)(2)(Iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71 (a)(4)00 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71 (a)(5)00E 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(C)
El OTHER Specify in Absb'act below or in__ 20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B) 0 50.73(a)(2)(v)(D)
NReC Form3WA 12. UCENSEE CONTACT FOR THIS LER LICENSEE CONTACT TELEPHONE NUMBER (Indude Ama Code)Joe Kutches, Maintenance Director (815) 415-2500 13. COMPLETE ONE UNE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT C I MANU- REPORTABLE CAUSE SYSTEM COMPONENT MANU- REPORTABLE CAUSE SYSTEM COMPONENT FACTURER TO EPIX C S FACTURER TO EPIX X NG IMEC Locknetics Y 14. SUPPLEMENTAL REPORT EXPECTED 15. EXPECTED MONTH DAY YEAR SUBMISSION
[E YES (If yes, complete 15. EXPECTED SUBMISSION DATE) O NO DATES S ABSTRACT (Limit to 1400 spaces, i.e., approdimately 15 single-spaced typewritten lines)On February 18, 2014, Unit 1 was in Mode 5 with fuel moves in progress during refueling outage Li R1 5, and Unit 2 was in Mode 1 at 100% power. At 1820 hours CST, it was reported that both air-lock doors of the Unit 2 Reactor Building 710' elevation between the Unit 2 diesel generator corridor and the Unit 2 Reactor Building were open at the same time for approximately 3 seconds. While both interlock doors were open, Technical Specification (TS) Surveillance Requirement (SR) 3.6.4.1.2
("Verify one secondary containment access door in each access opening is closed") was not met. Secondary containment was declared inoperable for the time that both interlock doors were open. TS 3.6.4.1 Required Action (RA) C.1 to suspend fuel movements on Unit 1 and RA A.1 to restore secondary containment to OPERABLE status within 4 hours were entered and exited at 1820 CST on February 18, 2014.The cause of the event was degradation of the door closure mechanism and door frame seal. A contributing cause was a less than robust design of the door interlock assembly.
Corrective actions from the previous occurrences to identify, procure and install a more robust interlock assembly design were still in progress at the time of the event. Additional corrective actions included creating a periodic preventative maintenance task to inspect, tighten, and replace fasteners as necessary.
NRC FORM 366 (02-2014)
U NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 01/31/2017 (02-2014)
Estimated burden per response to comply with this mandatory collection request 80 hours.Reported lessons learned are incorporated into the licensing process and fed back to industry.r sSend comments regarding burden estimate to the FOIA, Pnivacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by LICENSEE EVENT REPORT (LER) internet e-mail to lnfocodlects.Resource@nrc.gov, and to the Desk Officer, Office at infonmation and Regulatory Affairs, NEO8-102., (3150-0104), Office of Management and Budget, CONTINUATION SHEET Washington, DC 20503. H 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. FACIUTY NAME 2. DOCKET 6. LER NUMBER 3. PAGE SEQUENTIAL REV YEAR NUMBER NO.LaSalle County Station, Units 1 and 2 05000373 j 2 OF 5 r2014 -001 -00 /NARRATIVE LaSalle County Station Units 1 and 2 are General Electric Company Boiling Water Reactors with 3546 Megawatts Rated Core Thermal Power.A. CONDITION PRIOR TO EVENT: Unit(s): 1 /2 Event Date: February 18, 2014 Event Time: 1820 CST Reactor Mode(s): 5/1 Mode(s) Name: Refueling/Power Operation Power Level: 0% / 100%B. DESCRIPTION OF EVENT: On February 18, 2014, Unit 1 was in Mode 5 with fuel moves in progress during refueling outage Li R15, and Unit 2 was in Mode 1 at 100% power. At 1820 hours CST, it was reported that both air-lock doors of the Unit 2 Reactor Building 710' elevation between the Unit 2 diesel generator corridor and the Unit 2 Reactor Building were open at the same time for approximately 3 seconds.While both interlock doors were open, Technical Specification (FS) Surveillance Requirement (SR) 3.6.4.1.2 ('Verify one secondary containment access door in each access opening is closed") was not met. Secondary containment
[NG] was declared inoperable for the time that both interlock doors were open. TS 3.6.4.1 Required Actions (RA) C.1, C.2 and C.3 to immediately suspend irradiated fuel movements, core alterations, and OPDRVs on Unit 1 and RA A.1 to restore secondary containment to OPERABLE status within 4 hours were entered and exited at 1820 CST on February 18, 2014.This occurrence is reportable under 10 CFR 50.73(a)(2)(v)(C) and (D) as an event or condition that could have prevented the fulfillment of the safety function of the structures or systems that are needed to control the release of radioactive material and to mitigate the consequences of an accident.
An ENS report was made to the NRC at 2215 EST (EN# 49840) on February 18, 2014, pursuant to 10 CFR 50.72(b)(3)(v)(C).
An Engineering Evaluation has determined this event did not meet the NEI 99-02 definition of a Safety System Functional Failure.C. CAUSE OF EVENT: Troubleshooting found that the door closure mechanism and door seal were degraded for door #507 (Reactor Building side of the interlock), which prevented the electro-mechanical solenoid operated bolt from properly aligning with the door-mounted catch. This malfunction resulted in the capability to open both interlock doors#507 and #402 at the same time, and was similar to a previous occurrence on October 22, 2013.The degradation of the door closure mechanism and door seal was determined to be due to repeated challenges of the door during personnel ingress/egress.
The design of the interlock mechanism was considered a contributing cause, as it was considered less than robust for the application.
Corrective actions from the previous occurrences to identify, procure and install a more robust design were still in progress at the time of the event. Interim corrective actions were in place to perform quarterly inspections of the assemblies and to tighten the fasteners as required.NRC FORM 366A (02-2014)
NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (02-2014)
LICENSEE EVENT REPORT (LER)CONTINUATION SHEET 1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YER SEQUENTIAL REV YE500NUMBER NO.05000 3 OF 5 NARRATIVE D. SAFETY ANALYSIS: The safety significance of this event was minimal. The Reactor Building-to-outside differential pressure remained negative throughout the period that the secondary containment was inoperable.
The secondary containment was inoperable for approximately 3 seconds, which was significantly less than the four-hour Completion Time to restore the secondary containment to operable status allowed by TS 3.6.4.1 Required Action A.1.The function of the secondary containment is to contain, dilute, and hold up fission products that may leak from the primary containment following a Design basis Accident (DBA). Engineering Evaluation (EC 396711) was performed to show that this event had no impact on the safety function associated with secondary containment.
The time that both doors were simultaneously opened was less than 10 seconds. This event did not result in the reactor enclosure differential pressure dropping below the design bases set point of -0.25 inches w.g. Both the inner and outer doors were promptly closed by station personnel which ended the event. This event did not involve any kind of door or airlock material condition preventing door closure. Additionally, both the inner and outer doors were closed by normal expected means and were capable of remaining closed as designed.The computed dose for EC 396711 was based on the door opening during the 780 second time period prior to Standby Gas Treatment (SBGT) system drawdown and filtration.
This discounts the initial 120 seconds of an event where no release takes place, per calculation L-003068, "Re-Analysis of Loss of Coolant Accident (LOCA) Using Alternative Source Terms".The approximate 3 second opening of the secondary containment doors is bounded by calculation L-003068,"Re-Analysis of Loss of Coolant Accident (LOCA) Using Alternative Source Terms". Should an event occur, with both secondary containment doors open simultaneously for 30 seconds or less, this would result in a potential dose increase of approximately 3.85%. The 3.85% decrease in margin is inconsequential compared to the 10 CFR 100 regulatory limits.EC 396711 also evaluated the pressure impact on the secondary containment and the ability of the SBGT system to achieve the TS required negative pressure.
The results of the evaluation show SBGT would restore secondary containment pressure within 3 minutes which is well below the 15 minute maximum drawdown time required by TS.Based on the short duration of door opening (approximately 3 seconds), no material condition preventing door closure or maintaining the doors closed and attendance by knowledgeable personnel who closed the doors immediately, the secondary containment safety function was maintained.
E. CORRECTIVE ACTIONS:* The door closure mechanism and door frame seal for door #507 was repaired.* Efforts to install a more robust design for the interlock assembly are in progress." Quarterly preventative maintenance to inspect the assemblies and fasteners and tighten or replace as necessary remain in progress.NRC FORM 366A (02-2014)
NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (02-2014)
LICENSEE EVENT REPORT (LER)CONTINUATION SHEET 1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE I SEQUENTIAL REV YEAR NUMBER NO.05000 4 OF 5 NARRATIVE F. PREVIOUS OCCURRENCES:
LER 2013-007-01 On October 22, 2013, both Units 1 and 2 were in Mode 1 at 100% power. At 1129 hours CDT, it was reported that both air lock doors on the Unit 1 Reactor Building 710' elevation between the Chemistry Hot Lab and the Reactor Building were open at the same time for approximately 10 seconds. While both interlock doors were open, Technical Specification (TS) Surveillance Requirement (SR) 3.6.4.1.2
("Verify one secondary containment access door in each access opening is closed") was not met. Secondary containment was declared INOPERABLE for the time that both interlock doors were open. TS 3.6.4.1 Required Action A.1 for both Units 1 and 2 to restore secondary containment to OPERABLE status within 4 hours was entered and exited at 1129 CDT on October 22, 2013.The cause of the event was a less than robust design of the door interlock assembly.
Troubleshooting found that the mounting fasteners that secure the entire locking assembly to the frame of door # 226 (Reactor Building side of the interlock) were loose, which prevented the electro-mechanical solenoid operated bolt from properly aligning with the door-mounted catch. This misalignment prevented the bolt from entering the catch on door #226 when door # 225 (Chemistry Hot Lab side) was opened. This malfunction resulted in the capability to open both interlock doors at the same time, and was similar to a previous occurrence on February 28, 2013.LER 2013-001-02 On February 28, 2013, Unit 1 was in Mode 1 at 100% power and Unit 2 was in Mode 5 for refueling outage L2R14. At 0400 hours CST, it was reported that both air lock doors on the Unit 1 Reactor Building 710'elevation between the Chemistry Hot Lab and the Reactor Building were open at the same time for approximately 10 seconds. While both interlock doors were open, Technical Specification (TS) Surveillance Requirement (SR) 3.6.4.1.2
("Verify one secondary containment access door in each access opening is closed") was not met for Unit 1. Secondary containment was declared INOPERABLE for the time that both interlock doors were open. TS 3.6.4.1 Required Action A.1 to restore secondary containment to OPERABLE status within 4 hours was entered and exited for Unit 1 at 0400 CST on February 28, 2013.The cause of the event was determined to be a less than robust design of the door interlock assembly.Troubleshooting found that the mounting fasteners that secure the entire locking assembly to the frame of door# 226 (Reactor Building side of the interlock) were loose, which prevented the electro-mechanical solenoid operated bolt from properly aligning with the door-mounted catch. This misalignment prevented the bolt from entering the catch on door # 226 when door # 225 (Chemistry Hot Lab side) was opened. This malfunction resulted in the capability to open both interlock doors at the same time.This occurrence was similar to the October 2013 event. In addition to repairing the interlock assembly by tightening the fasteners, actions were initiated to periodically inspect the assemblies and to identify and install a more robust design. The new design had been identified but not installed when the October 2013 event occurred.LER 2012-001-00 On September 18, 2012, Units I and 2 were in Mode 1 at 100% power. At 0115 hours CDT, an Equipment Operator (EO) reported the Unit 2 Reactor Building 761'elevation Interlock Doors 424/314 were both open at the same time for approximately 10 seconds. During the time that both interlock doors were open, Technical Specification (TS) Surveillance Requirement (SR) 3.6.4.1.2
("Verify one secondary containment access door in NRC FORM 368A (02-2014)
NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (02-2014)
LICENSEE EVENT REPORT (LER)CONTINUATION SHEET 1. FACIUTY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEOUENTIAL I REV NUMBER NO.05000 5 OF 5 NARRATIVE each access opening is closed") was not met. The secondary containment was declared INOPERABLE for the time that both interlock doors were open. LaSalle Station entered and exited TS 3.6.4.1 Required Action A.1 for'both Units 1 and 2 to restore secondary containment to OPERABLE status within 4 hours.The cause of the event was determined to be the solenoid bracket being loose on Unit 2 Reactor Building 761'interlock door 424. Two screws that hold the locking solenoid bracket in place were found loose. The two loose screws on the locking solenoid mounting bracket caused the electric lock assembly to become misaligned.
The misalignment of the electric lock assembly prohibited the locking solenoid plunger from being fully engaged with the door catch and damaged the limit switch, which resulted in the capability to open both interlock doors at the same time.G. COMPONENT FAILURE DATA: Locknetics/SDC style lock NRC FORM 366A (02-2014)}}

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