05000331/LER-2014-002, Regarding Both Doors in Secondary Containment Airlock Opened Concurrently

Regarding Both Doors in Secondary Containment Airlock Opened Concurrently

ML14108A329
Person / Time
Site:	Duane Arnold
Issue date:	04/17/2014
From:	Richard Anderson NextEra Energy Duane Arnold
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NG-14-0104 LER 14-002-00
Download: ML14108A329 (4)

LER-2014-002, 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
3312014002R00 - NRC Website

text

NEXTera BNERAYE ARNOLD April 17, 2014 NG-14-0104 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 Report #2014-002 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

Tichrd L n eson Vice President, Duane Arnold Energy Center NextEra Energy Duane Arnold, LLC cc:

Administrator, Region Ill, USNRC Project Manager, DAEC, USNRC Resident Inspector, DAEC, USNRC U4~

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.

Send comments regarding burden estimate to the FOIA, Privacy and Information Collections LICENSEE EVENT R(LER)

Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by REPORT internet e-mail to lnfocollects.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 3

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 YEARSEOUENTIAL REV J

FACILITY NAME DOCKET NUMBER YEAR NUMBER NO.

MONTH DAY YEAR N/A N/A FACILITY NAME DOCKET NUMBER 02 18 2014 2014 -

002

- 00 04 17 2014 N/A N/A

9. OPERATING MODE

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

ED 20.2201(b) 0 20.2203(a)(3)(i)

D1 50.73(a)(2)(i)(C)

El 50.73(a)(2)(vii)

D 20.2201(d)

[

20.2203(a)(3)(ii)

[

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

D 50.73(a)(2)(viii)(A) 1

[] 20.2203(a)(1)

[]

20.2203(a)(4)

[]

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

[]

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

[] 20.2203(a)(2)(i)

[]

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

[]

50.73(a)(2)(iii)

[]

50.73(a)(2)(ix)(A)

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

[: 50.36(c)(1)(ii)(A)

El 50.73(a)(2)(iv)(A)

D 50.73(a)(2)(x)

D 20.2203(a)(2)(iii)

D 50.36(c)(2)

D 50.73(a)(2)(v)(A)

D 73.71(a)(4)

[] 20.2203(a)(2)(iv)

[]

50.46(a)(3)(ii)

[]

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

[]

73.71 (a)(5) 100%

1 % 20.2203(a)(2)(v)

[: 50.73(a)(2)(i)(A)

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

D OTHER El 20.2203(a)(2)(vi)

D 50.73(a)(2)(i)(B)

[

50.73(a)(2)(v)(D) specify in Abstract bel....

in

12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT TELEPHONE NUMBER (Include Area Code)

Laura B. Swenzinski, Senior Licensing Engineer (319) 851-7724CAUSE SYTE COPNN MANU-REPORTABLE

CAUSE

SYSTEM COMPONENT MANU-REPORTABLE C E SYSTEM COMPONENT FACTURER TO EPIX FACTURER TO EPIX X

JM IEL Alarm Lock N

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

14. SUPPLEMENTAL REPORT EXPECTED 15.SEXPECTED MONTH DAY YEAR SUBMISSIONcB III YES (If yes, complete 15. EXPECTED SUBMISSION DATE)

ZNO DATEI ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)

On February 18, 2014, 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 Event Notification 49838 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.

The apparent cause of the event was determined to be excess strength of a permanent magnet on one of the doors. The monthly surveillance test has been revised to check the permanent magnet for proper adjustment and to adjust it as needed.

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)

NIRC =

I.

Description of Event

On February 18, 2014 at 0944 CST, while operating at 100% power, the Control Room Supervisor (CRS) received a call that Door 245 and Door 239A, both in Secondary Containment Airlock 222 were 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 each 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. The CRS stationed individuals to control access to the door to ensure.

no other violations occurred.

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 Event Notification 49838 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. 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. It was determined that the adjustable permanent magnet on Door 245 allowed the airlock to sense Door 245 was closed prior to it latching closed. Because of this, the interlock no longer prevented Door 239A from opening, which ultimately led to both doors being opened concurrently. The Door 245 permanent magnet was adjusted, and surveillance testing was performed satisfactorily per Surveillance Test Procedure (STP) 3.6.4.1-02, Secondary Containment Airlock Verification, to verify the airlock was functioning properly. The airlock was then restored to functional status at 1323 on February 18, 2014.

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 failures since an engineering analysis (Corrective Action ACE 1941869-02) was performed which determined that the system was capable of

performing its safety function during events when the airlock was 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

An Apparent Cause Evaluation was completed. The evaluation identified the apparent cause of Door-245 and Door-239A being open at the same time as excess permanent magnet strength.

After the permanent magnet was adjusted, the interlock was able to prevent both doors from opening.

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. STP 3.6.4.1-02 has been revised to check the permanent magnet for proper adjustment by verifying that the red interlock light(s) turn OFF as close to when the door latches as possible. The permanent magnet will then be adjusted as needed.

V.

Additional Information

Previous Similar Occurrences:

A review of DAEC Licensee Event Reports from the past 5 years identified one similar occurrence, reference LER 2013-006.

A review of the corrective action program identified additional occurrences of airlock conditions causing momentary secondary containment inoperability - two additional occurrences in the past year and nine occurrences in the past two years.

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, 10CFR50.73(a)(2)(v)(C).