05000331/LER-2015-001-01, LERs 15-001-01 and 15-003-01 for Duane Arnold Regarding Both Doors in Secondary Containment Airlock Opened Concurrently
| ML15181A336 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 06/25/2015 |
| From: | Vehec T NextEra Energy Duane Arnold |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NG-15-0236 LER 15-001-01, LER 15-003-01 | |
| Download: ML15181A336 (7) | |
| 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) 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 |
| 3312015001R01 - NRC Website | |
text
NExTera ENER :Y June 25, 2015 NG-1 5-0236 10 CFR 50.73 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555-0001 Duane Arnold Energy Center Docket 50-331 Renewed Op. License No. DPR-49 Licensee Event Reports #2015-001-01 and #2015-003-01 Please find attached the subject reports 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 III, USNRC Project Manager, DAEC, USNRC Resident Inspector, DAEC, USNRC NextEra Energy Duane Arnold, LLC, 3277 DAEC Road, Palo, IA 52324
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 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.
- - W
,*Send comments regarding burden estimate to the FOIA, Privacy and Information Collections IEOBranch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by LICENSEE EVENT fREPORT (LER) internet e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and (See Page 2 for required number of 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 digits/characters for each block) control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Duane Arnold Energy Center 05000-331 1 OF
- 4. TITLE Both Doors in Secondary Containment Airlock Opened Concurrently
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MD FACILITY NAME DOCKET NUMBER YER NUMBER NO.
MOT A
ER N/A N/A IFACILITY NAME DOCKET NUMBER 03 21 2015 2015 -
001 01 06 25 2015 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)
El 20.2203(a)(3)(i)
[j 50.73(a)(2)(i)(C)
[L 50.73(a)(2)(vii)
LI 20.2201(d)
LI 20.2203(a)(3)(ii)
LI 50.73(a)(2)(ii)(A)
LI 50.73(a)(2)(viii)(A)
LI 20.2203(a)(1)
LI 20.2203(a)(4)
EL 50.73(a)(2)(ii)(B)
LI 50.73(a)(2)(viit)(B)
LI 20.2203(a)(2)(i)
LI 50.36(c)(1)(i)(A)
LI 50.73(a)(2)(fii)
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)
EL 50.73(a)(2)(v)(A)
LI 73.71 (a)(4)
L0 20.2203(a)(2)(iv)
LI 50.46(a)(3)(ii)
LI 50.73(a)(2)(v)(B)
LI 73.71 (a)(5) 1 % 20.2203(a)(2)(v)
[L 50.73(a)(2)(i)(A)
Z 50.73(a)(2)(v)(C)
LI OTHER El 20.2203(a)(2)(vi)
[] 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in
- 12. LICENSEE CONTACT FOR THIS LER
- - ICENSEE CONTACT Laura B. Swenzinski, Senior Licensing Engineer (3L19H)NE NUMBER (IncludeArea 85o1e7 I(319) 851-7724CAUSE SYSTEM COMPONENT FMANU-REPORTABLE
CAUSE
FACTURER TO EPIX I
X JM IEL Alarm Lock N
N/A
- 14. SUPPLEMENTAL REPORT EXPECTED LI YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
Z NO ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On March 21, 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#50914).
Following the event, the doors were verified to be functioning properly and no deficiencies were noted on either door.
A Root Cause Evaluation was conducted and 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.
This event did not result in a safety system functional failure. There were no radiological releases associated with this event.
NRC FORM 366 (02-2014)
I.
Description of Event
On March 21, 2015 at 0030, while operating at 100% power, the Control Room Supervisor (CRS) received a call that Door 225 and Door 228, 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#50914). 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 interlock device 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, the doors were verified to be functioning properly and no deficiencies were noted on either door. On March 22, 2015 at 1619 hours0.0187 days <br />0.45 hours <br />0.00268 weeks <br />6.160295e-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.
II.
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) determined 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 calculation.
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 and 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 Secondary Containment door interlocks is performed monthly via STP 3.6.4.1-02, Secondary Containment Airlock Verification. Additionally, signs have been 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 corrective action introduces a time delay, which allows additional time for the interlock mechanism to actuate and prevent the other door from being opened. TSTF-551, "Revise Secondary Containment Surveillance Requirements" will be implemented once approved.
V.
Additional Information
Previous Similar Occurrences:
A review of DAEC Licensee Event Reports from the past 5 years identified three similar occurrences, reference LER 2013-006, LER 2014-002 and LER 2014-003.
A review of the corrective action program identified additional occurrences of airlock conditions causing momentary secondary containment inoperability - seven additional occurrences in the past two years, with five of those occurring in the last year.
EIIS System and Component Codes:
IEL Interlock Reportinq Requirements:
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, 10CFR50.73(a)(2)(v)(C).
I.
Description of Event
On April 16, 2015 at 1320, 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#50989). 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 interlock device 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 areallowed to open. Immediately following the event, on April 16, 2015 at 1535 hours0.0178 days <br />0.426 hours <br />0.00254 weeks <br />5.840675e-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.
II.
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) determined 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 calculation.
This event did not result in a safety system functional failure. There were no automatically or manually initiated safety system responses.
I1l.
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 and 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 Secondary Containment door interlocks is performed monthly via STP 3.6.4.1-02, Secondary Containment Airlock Verification. Additionally, signs have been 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 corrective action introduces a time delay, which allows additional time for the interlock mechanism to actuate and prevent the other door from being opened. TSTF-551, "Revise Secondary Containment Surveillance Requirements" will be implemented once approved.
V.
Additional Information
Previous Similar Occurrences:
A review of DAEC Licensee Event Reports from the past 5 years identified four similar occurrences, reference LER 2013-006, LER 2014-002, LER 2014-003 and LER 2015-001.
A review of the corrective action program identified additional occurrences of airlock conditions causing momentary secondary containment inoperability - eight additional occurrences in the past two years, with six of those occurring in the last year.
EIIS System and Component Codes:
IEL Interlock
Reporting Requirements
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, IOCFR50.73(a)(2)(v)(C).