05000331/LER-2015-004, Regarding Both Doors in Secondary Containment Airlock Opened Concurrently

Regarding Both Doors in Secondary Containment Airlock Opened Concurrently

ML15286A054
Person / Time
Site:	Duane Arnold
Issue date:	10/06/2015
From:	Vehec T NextEra Energy Duane Arnold
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NG-15-0296 LER 15-004-00
Download: ML15286A054 (5)

LER-2015-004, Regarding Both Doors in Secondary Containment Airlock Opened Concurrently

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
3312015004R00 - NRC Website

text

NExTeraT M.

October 6, 2015 NG-1 5-0296 10 CFR 50.73 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555-0001 Duane Arnold Energy Center Docket 50-33 1 Renewed Op. License No. DPR-49 Licensee Event Report #2015-004 Please find attached the subject report submitted in accordance with 10 CFR 50,73. This letter makes no new commitments or changes to any existing-

commitments

T. A. Vehec Vice President, Duane Arnold Energy Center NextEra Energy Duane Arnold, LLC cc:

Administrator, Region Ill, USNRC Project Manager, DAEC, USNRC Resident Inspector, DAEC, USNRC-NextEra Energy.Duane Arnold, LlC, 3277 DAEC Road, Palo, IA 52324

NRCFORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 01/31/2017 (02-014,. :,

,*,"*,,,:..Estimated bsrden 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 />.

• ,_,,*,I,

• °,,!

.Reported lessons learned are incorporated into the licensing process and fed back to industry.

i. 1:.

.. : *Send comments regarding burden estimate to the FOIA, Privacy and Information Collections

.u,- u (Lu

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Ir-,

Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by

'LICENSEE'~ EVENTI REPORT.~

~LER) internet e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of information and

................(See Page 2 for required number of.......

Regelatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC digis/carater foreac blck)20503.

If a means used to impose an information collection does not display a currently valid 0MB digis/carater foreac blck)control number, the NRC may not conduct or sponsor, and a person is not reqeired to respond to, the information collection.

13. PAGE Duane Arnold Energy Center05 0-3 1O 4

4. TITLE Both Doors in Secondary Containment Airlock Opened Concurrently

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED MNT DA YERSQETA RE FACILITY NAME DOCKET NUMBER MOT A ER YEAR SEUMENILREVO MONTH DAY YEAR N/AN/

205-04 "0

IFACILITY NAME DOCKET NUMEER 08 27 2015 205 04

- 0 10 06 2015 IN/A N/A

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)

]

20.2201(b)

LI 20.2203(a)(3)(i)

El 50.73(a)(2)(i)(C)

LI 50.73(a)(2)(vii)

Lii 20.2201(d)

LI 20.2203(a)(3)(ii)

[]

50.73(a)(2)(ii)(A)

LI 50.73(a)(2)(viii)(A)

LI 20.2203(a)(1)

LI 20.2203(a)(4)

LI 50.73(a)(2)(ii)(B)

Lii 50.73(a)(2)(viii)(B)

Lii 20.2203(a)(2)(i)

LI 50.36(c)(1)(i)(A)

LI 50.73(a)(2)(iii)

LI[ 50.73(a)(2)(ix)(A)

10. POWER LEVEL LI 20.2203(a)(2)(ii)

LI 50.36(c)(1)(ii)(A)

LI 50.73(a)(2)(iv)(A)

LI 50.73(a)(2)(x)

LI 20.2203(a)(2)(iii)

- LI 50.36(c)(2)

LI 50.73(a)(2)(v)(A)

LI 73.71 (a)(4)

LI 20.2203(a)(2)(iv)

LI 50.46(a)(3)(ii)

LI 50.73(a)(2)(v)(B)

LII 73.71 (a)(5) 100%

LI 20.2203(a)(2)(v)

LI 50.73(a)(2)(i)(A)

[]

50.73(a)(2)(v)(C)

LI OTHER LI 20.2203(a)(2)(vi)

LII 50.73(a)(2)(i)(B)

LI 50.73(a)(2)(v)(D) specify in Abstract below or in

______________NRC___FoNRCForm66A

12. LICENSEE CONTACT FOR THIS LER

_IOENSEE CONTACT TLPOENME(nldeAaCoeCAUSE I SYSTEM COMPONENT MANTU-RE PORTABEIX

CAUSE

SYSTEM COMPONENT MN-RPRAL II FACTURER TO EPIX I

ATRR TEI X

JM IEL Alarm Lock N..

N/A N/A N/A N/A N/A

14. SUPPLEMENTAL REPORT EXPECTED

15. EXPECTED MONTH DAY YEAR SUBMISSION LI YES (If yes, complete 15. EXPECTED SUBMISSION DATE)

[]

NO DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)

On August 27, 2015, while operating at 100% power, workers opened doors concurrently when entering a secondary containment access airlock. The individuals involved each closed their respective doors upon encountering this unexpected condition; however, the result was a brief inoperability of secondary containment integrity. This resulted in an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> reportable event. The Resident Inspector was notified, and an Event Notification was made pursuant to 10 CFR 50.72(b)(3)(v)(C) due to a condition at the time of discovery that prevented the fulfillment of the Secondary Containment safety function (Reference EN#52353).

Following the event, the doors were verified to be functioning properly via Surveillance Test Procedure. A Root Cause Evaluation was conducted in May 2015 which determined the root cause of this event is that the airlock door interlock i not designed to prevent more than one airlock door from opening under all possible conditions.

• This event did not result in a safety system~functional~failu~.e.. There were no radiological releases associated with this event...

NRC FORM 366 (02-2014) m A.

I.

Description of Event

On August 27, 2015 at 0752, while operating at 100% power, the Control Room Supervisor (CRS) was notified that Door 225 and Door 227, both in Secondary Containment Airlock 216, had been opened concurrently. The doors being open at the same time caused a failure to meet SR 3.6.4.1.2 to verify that either the outer door(s) or the inner door(s) in each Secondary Containment access opening are closed. The identified condition caused Secondary Containment to be considered inoperable per TS LCO 3.6.4.1. The individuals involved immediately closed their respective doors upon encountering this unexpected condition. This action allowed SR 3.6.4.1.2 to be met, and restored Secondary Containment to an operable status.

This resulted in an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> reportable event. The Resident Inspector was notified, and an, Event Notification was made pursuant to 10 CFR 50.72(b)(3)(v)(C) due to a condition at the time of discovery that prevented the fulfillment of the Secondary Containment safety function (Reference EN#51353). Secondary containment leak tightness is required to ensure that the release of radioactive materials from the primary containment is restricted to those leakage paths and associated leakage rates assumed in the accident analysis and that fission products entrapped within the secondary containment structure will be treated by the Standby Gas Treatment System prior to discharge to the environment.

The Secondary Containment airlock utilizes an interlockdevice with an adjustable permanent magnet (mounted on the door), and an electromagnet (on the door frame) arranged in an electrical circuit so that door(s) are held closed and/or are allowed to open. Immediately following the event, on August 27, 2015 at 0952 hours0.011 days <br />0.264 hours <br />0.00157 weeks <br />3.62236e-4 months <br />, surveillance testing was performed satisfactorily per Surveillance Test Procedure (STP) 3.6.4.1-02, Secondary Containment Airlock Verification.

There were no radiological releases associated with this event. There were no other structures, systems or components inoperable at the start of this event that contributed to the event.

I1.

Assessment of Safety *Consequences:

There were no actual safety consequences associated with this event; the potential--safety consequences were minimal. Both doors on the airlock were open simultaneously for less than 10 seconds, and were able to close immediately upon discovery of the condition.

This event will not be reported as a safety system functional failure since an engineering analysis.

(Corrective Action ACE1968923-01) deter~mined that the system is capable of performing its safety function during events,when. the airlock is open for less than 10 seconds. The post-LOCA dose calculation does not credit secondary *containment integrity for mitigation of on-site and off-,site doses for the first 5 minutes of the event;.Therefore, this event is bounded by the existing dose calc~ula~tion,

This event did not result in a safety system functional failure. There were no automatically or manually initiated safety system responses.

Ill.

Cause of Event

Technical Specifications Surveillance Requirement SR 3.6.4.1.2 requires one inner or one outer secondary containment airlock door to be closed at all times. A Root Cause Evaluation was conducted in May 2015 which determined the root cause of this event is that the airlock door interlock is not designed to prevent more than one airlock door from opening under all possible

• conditions. Specifically, the interlock may allow opening both doors in an airlock if both permissive buttons are depressed simultaneously.

IV.

Corrective Actions

An operational check of the Sepondary Containment door-interlocks is performed monthly via STP 3.6.4.1 -02, Secondary Contain~nent Airlock Verification. Signs are installed at each airlock door

• instructing personnel who are accessing or leaving the airlock to wait 2 seconds after activating the interlock before opening the door. This 2 second delay allows additional time for the interlock mechanism to actuate and prevent the other door from being opened.

To further reduce the likelihood of recurrence, cameras have been installed at Door 228 on the Reactor Building side and at Door 225 on the Access control side. Monitors showing the view of the opposite camera are installed at these locations. Personnel have been instructed on how to use the monitors to prevent simultaneous airlock access. Additionally, Door 227 has been posted as emergency use only.

V.

Additional Information

Previous Similar Occurrences:

A review of DAEC*Licensee Event Reports from the past 5 years identified five similar occurrences, reference LER 201 3-006, LER 2014-002, LER 2014-003, LER 2015-001 and LER 2015-003.

A review of the corrective action program identified additional occurrences of airlock conditions causing momentary secondary containment inoperability - nine additional occurrences in the past two years, with five of those occurring in the last year.

EIIs System and Component Codes:

IEL Interlock l i I

I I

ReDortinQ Reciuirements:

This event is being reported as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material, I10CFR5O.73(a)(2)(v)(C).

I.

Description of Event

On August 27, 2015 at 0752, while operating at 100% power, the Control Room Supervisor (CRS) was notified that Door 225 and Door 227, both in Secondary Containment Airlock 216, had been opened concurrently. The doors being open at the same time caused a failure to meet SR 3.6.4.1.2 to verify that either the outer door(s) or the inner door(s) in each Secondary Containment access opening are closed. The identified condition caused Secondary Containment to be considered inoperable per TS LCO 3.6.4.1. The individuals involved immediately closed their respective doors upon encountering this unexpected condition. This action allowed SR 3.6.4.1.2 to be met, and restored Secondary Containment to an operable status.

This resulted in an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> reportable event. The Resident Inspector was notified, and an, Event Notification was made pursuant to 10 CFR 50.72(b)(3)(v)(C) due to a condition at the time of discovery that prevented the fulfillment of the Secondary Containment safety function (Reference EN#51353). Secondary containment leak tightness is required to ensure that the release of radioactive materials from the primary containment is restricted to those leakage paths and associated leakage rates assumed in the accident analysis and that fission products entrapped within the secondary containment structure will be treated by the Standby Gas Treatment System prior to discharge to the environment.

The Secondary Containment airlock utilizes an interlockdevice with an adjustable permanent magnet (mounted on the door), and an electromagnet (on the door frame) arranged in an electrical circuit so that door(s) are held closed and/or are allowed to open. Immediately following the event, on August 27, 2015 at 0952 hours0.011 days <br />0.264 hours <br />0.00157 weeks <br />3.62236e-4 months <br />, surveillance testing was performed satisfactorily per Surveillance Test Procedure (STP) 3.6.4.1-02, Secondary Containment Airlock Verification.

There were no radiological releases associated with this event. There were no other structures, systems or components inoperable at the start of this event that contributed to the event.

I1.

Assessment of Safety *Consequences:

There were no actual safety consequences associated with this event; the potential--safety consequences were minimal. Both doors on the airlock were open simultaneously for less than 10 seconds, and were able to close immediately upon discovery of the condition.

This event will not be reported as a safety system functional failure since an engineering analysis.

(Corrective Action ACE1968923-01) deter~mined that the system is capable of performing its safety function during events,when. the airlock is open for less than 10 seconds. The post-LOCA dose calculation does not credit secondary *containment integrity for mitigation of on-site and off-,site doses for the first 5 minutes of the event;.Therefore, this event is bounded by the existing dose calc~ula~tion,

This event did not result in a safety system functional failure. There were no automatically or manually initiated safety system responses.

Ill.

Cause of Event

Technical Specifications Surveillance Requirement SR 3.6.4.1.2 requires one inner or one outer secondary containment airlock door to be closed at all times. A Root Cause Evaluation was conducted in May 2015 which determined the root cause of this event is that the airlock door interlock is not designed to prevent more than one airlock door from opening under all possible

• conditions. Specifically, the interlock may allow opening both doors in an airlock if both permissive buttons are depressed simultaneously.

IV.

Corrective Actions

An operational check of the Sepondary Containment door-interlocks is performed monthly via STP 3.6.4.1 -02, Secondary Contain~nent Airlock Verification. Signs are installed at each airlock door

• instructing personnel who are accessing or leaving the airlock to wait 2 seconds after activating the interlock before opening the door. This 2 second delay allows additional time for the interlock mechanism to actuate and prevent the other door from being opened.

To further reduce the likelihood of recurrence, cameras have been installed at Door 228 on the Reactor Building side and at Door 225 on the Access control side. Monitors showing the view of the opposite camera are installed at these locations. Personnel have been instructed on how to use the monitors to prevent simultaneous airlock access. Additionally, Door 227 has been posted as emergency use only.

V.

Additional Information

Previous Similar Occurrences:

A review of DAEC*Licensee Event Reports from the past 5 years identified five similar occurrences, reference LER 201 3-006, LER 2014-002, LER 2014-003, LER 2015-001 and LER 2015-003.

A review of the corrective action program identified additional occurrences of airlock conditions causing momentary secondary containment inoperability - nine additional occurrences in the past two years, with five of those occurring in the last year.

EIIs System and Component Codes:

IEL Interlock l i I

I I

ReDortinQ Reciuirements:

This event is being reported as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material, I10CFR5O.73(a)(2)(v)(C).