05000237/LER-2013-001
| Dresden Nuclear Power Station, Unit 2 | |
| Event date: | 06-28-2013 |
|---|---|
| Report date: | 12-20-2013 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material |
| 2372013001R01 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
Dresden Nuclear Power Station (DNPS) Units 2 and 3 are General Electric Company Boiling Water Reactors 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: 06-28-2013 Event Time: 0749 hours0.00867 days <br />0.208 hours <br />0.00124 weeks <br />2.849945e-4 months <br /> CDT Reactor Mode: 1 Mode Name: Power Operation Power Level: 100 percent Unit: 03 Event Date: 06-28-2013 Event Time: 0749 hours0.00867 days <br />0.208 hours <br />0.00124 weeks <br />2.849945e-4 months <br /> CDT Reactor Mode: 1 Mode Name: Power Operation Power Level: 100 percent
Description of Event:
At 0749 CDT on June 28, 2013, indication was received in the control room that two secondary containment [NG] doors leading to the Unit 2/3 EDG room were opened simultaneously. Two individuals from the Operations Department staff were exiting 2/3 EDG Room at the same time that a Radiation Protection Department technician in the Unit 2 Reactor Building was heading towards the 2/3 EDG room. The individuals were able enter the interlock at the same time which resulted in both doors opening simultaneously. The interlock was empty at the time the doors were opened simultaneously and it was reported that both red lights were out (i.e., indicating the other door was shut and the interlock logic would allow the door to open) prior to the buttons being pushed to open the doors.
This event 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.
Cause of Event:
Maintenance troubleshooting efforts recreated the failure scenario in the plant, and further investigation of the component identified the latch bolt monitor switch tripper as the failure mechanism. This failure mechanism was determined to be an isolated and rare premature failure.
Safety Analysis:
The Secondary Containment interlock doors were open for approximately seven seconds and based upon the short duration of the secondary containment doors being opened simultaneously and that the Secondary Containment differential pressure remained negative during the course of this event, this event is of low safety significance.
Corrective Actions:
September 23, 2013 event, site engineering performed an apparent the need to develop a modification to improve the interlock has completed the engineering change under EC 395616, and Work Order 1679716.
the number of previous occurrences for this event over table presents these results for the Unit 2/3 Interlock:
door the the event As a result of this event, and a cause evaluation that identified circuit. Dresden engineering modification was installed under
Previous Occurrences:
past The related being A search was performed to determine two years. The following 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 Component search revealed that there to a failure of the Unit reported in this LER.
Failure Data:
was one prior occurrence, within the past two years, that specifically 2/3 Interlock. Additionally, there was one occurrence after the Manufacturer Model Part Type Vendor Folger Adam Model 310 Series 310-1 Door Strike Hanchett Entry Systems, Inc