05000237/LER-2014-001, Regarding Secondary Containment Inoperable Due to Two Interlock Doors Being Open Simultaneously
| ML14160A702 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 05/27/2014 |
| From: | Marik S Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| SVPLTR 14-0033 LER 14-001-00 | |
| Download: ML14160A702 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function 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 |
| 2372014001R00 - NRC Website | |
text
Dresden Nuclear Power Station 6500 North Dresden Road S Exe on Generation Morris, IL60450 Exe~n Ge eratono.815 942 2920 Telephone www.exeloncor-p.com 10 CFR 50.73 SVPLTR # 14-0033 May 27, 2014 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Units 2 and 3 Renewed Facility Operating License Nos. DPR-19 and DPR-25 NRC Docket Nos. 50-237 and 50-249
Subject:
Licensee Event Report 237/2014-001-00, Secondary Containment Inoperable Due to Two Interlock Doors Being Open Simultaneously Enclosed is Licensee Event Report 237/2014-001-00, "Secondary Containment Inoperable Due to Two Interlock Doors Being Open Simultaneously." This report describes an event which is being reported in accordance with 10 CFR 50.73(a)(2)(v)(C), any 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.
There are no regulatory commitments contained in this submittal.
Should you have any questions concerning this letter, please contact Mr. Glen Morrow at (815) 416-2800.
Respectfully, Shane M. Marik Site Vice President Dresden Nuclear Power Station Enclosure: Licensee Event Report 237/2014-001 -00 cc:
Regional Administrator - NRC Region III NRC Senior Resident Inspector - Dresden Nuclear Power Station
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 01/31/2017 102-2014)
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 I
(Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by LICENSEE EVENT REPORTi (LE l) intemet 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 Dresden Nuclear Power Station, Unit 2 05000237 1 OF 3
- 4. TITLE Secondary Containment Inoperable Due to Two Interlock Doors Being Open Simultaneously
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED DA ER
- - FEQETA E
FACILITY NAME IDOCKET NUMBER MONTH YEAR YEAR NUMBER NO.
MONTH DAY YEAR Dresden Unit 3 05000249 FACILITY NAME DOCKET NUMBER 03 X7 014 2014 -
001
- - 00 0
27 141 N/A 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
[1 20.2201(b)
[I 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii)
Ej 20.2201(d)
[I 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)
[I 20.2203(a)(2)(i)
[E 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii)
El 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL
[-
20.2203(a)(2)(ii)
[1 50.36(c)(1)(ii)(A)
El 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
E] 20.2203(a)(2)(iii)
[I 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71 (a)(4) 1E 20.2203(a)(2)(iv)
[I 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71 (a)(5) 100 IZ 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C) pe OTHER
[] 2.223(a(2)vi)
[] 5.73a)()(i(B)[]
5.73a)()(v(D)Specify in Abstract below or in
PLANT AND SYSTEM IDENTIFICATION
Dresden Nuclear Power Station (DNPS), Units 2 and 3, are a General Electric Company Boiling Water Reactor with a licensed maximum power level of 2957 megawatts thermal. The Energy Industry Identification System codes used in the text are identified as [XX].
A.
Plant Conditions Prior to Event:
Unit: 02 Event Date: 3-27-2014 Event Time: 0151 hours0.00175 days <br />0.0419 hours <br />2.496693e-4 weeks <br />5.74555e-5 months <br /> CDT Reactor Mode: 1 Mode Name: Power Operation Power Level: 100 percent Unit: 03 Event Date: 3-27-2014 Event Time: 0151 hours0.00175 days <br />0.0419 hours <br />2.496693e-4 weeks <br />5.74555e-5 months <br /> CDT Reactor Mode: 1 Mode Name: Power Operation Power Level: 100 percent B.
Description of Event
On March 27, 2014, two secondary containment [NG] interlock doors [IMEC] were opened simultaneously. At approximately the same time, an Electrical Maintenance Department (EMD) First Line Supervisor (FLS) approached the interlock from the emergency diesel generator side of the 2/3-5850-137 door and two Equipment Operators (EO) approached the interlock from the Reactor Building (RB) side of the 2/3-5850-59 door. When both work groups proceeded to enter the interlock, it was realized the doors were open simultaneously and they immediately secured both doors in the closed position. At this time, control room operators received alarm "902-4 E-21 U2/3 DIESEL GEN INTLK DOORS INOP/BYP" as would be expected with both doors open simultaneously; the alarm cleared when the doors were secured. The work groups communicated the failure to the Operations unit supervisors and were given instructions to exit through the RB door 2/3-5850-59 without further incident.
The event occurred during a period of elevated traffic through the interlock (i.e., while Diesel Generator work was in progress). To mitigate the potential for an additional failure following the event, the hand switches were administratively controlled and a door attendant was staged in the interlock to operate it. The attendant physically secured the opposite door when either door was opened. The doors were cycled approximately 300 times over the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period following the event; the interlock operated as expected.
An Engineering Evaluation was performed (per NEI 99-02, Regulatory Assessment Performance Indicator Guideline) to show this event did not constitute a Safety System Functional Failure.
C.
Cause of Event
Troubleshooting of the event was performed in accordance with station procedures, and no causal factors could be identified as a result of troubleshooting. Multiple scenarios were postulated but engineering did not identify any as an apparent cause of the event. However, the most probable cause was determined to be a failure of the magnetic vane operated limit switch on the 2/3-5850-59 EDG door. This determination was based off of historical poor performance of the component.
D.
Safety Analysis
The time that both doors were simultaneously opened was about five seconds, which did not result in the reactor enclosure differential pressure dropping below the required vacuum of 0.25 inches water gauge. Both the inner and outer doors were closed by normal expected means and were capable of remaining closed as designed. Based on the short duration of both doors being opened simultaneously, and that there were no material conditions preventing door closure or maintaining the doors closed, the secondary containment safety function was maintained.
From a safety consideration, the primary purpose of the secondary containment is to minimize the ground level release of airborne radioactive materials and to provide a controlled, elevated release of the building atmosphere under accident conditions. Engineering Evaluation (EC) 397055 was performed to show that events of this nature have no impact on the safety function of secondary containment, given that no exfiltration from the reactor building would have occurred as result of the airlock door breaches. Therefore, the dose consequence from postulated releases from the reactor building during these short durations would be bounded by the existing design basis LOCA dose analysis. The safety significance of this event was minimal.
E.
Corrective Actions
The station is completing or has completed the following actions:
- 1. Complete installation of an interlock modification
- 2. Replace the magnetic limit switch on both the EDG and Reactor Building Doors F.
Previous Occurrences
IR Date Sort Description 1493171 3/27/2013 Unit 2/3 Interlock Failure 1530208 6/28/2013 Unit 2/3 Interlock Failure 1562654 9/23/2013 Unit 2/3 Interlock Failure G.
Component Failure Data
Manufacturer Model Type ZERO INTERNATIONAL 361A Air Lock Doors