05000237/LER-2008-001
| Docket Number Sequential Revmonth Day Year Year Month Day Year N/A N/Anumber No. | |
| Event date: | 11-19-2007 |
|---|---|
| Report date: | 03-17-2008 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2372008001R00 - NRC Website | |
Dresden Nuclear Power Station (DNPS) Unit 2 is a General Electric Company Boiling Water Reactors with a licensed maximum power level of 2957 megawatts thermal.
A. Plant Conditions Prior to Event:
Unit: 02� Event Date: 11-19-2007 �Reactor Mode: 2� Mode Name: Startup Power Level: 10 percent Reactor Coolant System Pressure: Approximately 900 psig
B. Description of Event:
On January 15, 2008, a DNPS Qualified Nuclear Engineer was performing mentoring with a reactor engineering trainee on control rod sequencing and discussing the reference documents used to prepare a sequence. One of the required reference documents identified was the results from the Cycle 20 cycle-specific control rod drop accident analyses were reviewed. During this review it was identified that the control rod sequence used for startup of Unit 2 following the refueling outage in November 2007 did not comply with the control rod drop accident analysis. The control rod pull order used in the analysis did not match the order used for the Unit 2 startup sequence. The analysis used control rod group pull sequence 3-4-1-2-7-8-10-9 while the Unit 2 startup sequence used control rod group pull sequence 3-4-1-2-8-7-10-9. A review of the Unit 2 conditions on November 19, 2007, identified that for approximately 5 1/2 hours the unit did not comply with the requirements of Technical Specification 3.1.6, "Rod Pattern Control.
This event is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B), "Any operation or condition which was prohibited by the plant's Technical Specifications.
C. Cause of Event:
The Root Cause of this event was human performance and was attributed to failure of Dresden Nuclear Power Station personnel to follow procedures due to a lack of understanding of the requirements for using a Level 2 procedure and the qualified individual incorrectly assumed that the "Level 2 — Reference Use" procedures did not need to be reviewed in detail during preparation of the sequence.
The evaluation of this event identified the following:
following the November 2007 refuel outage was identified and scheduled to allow adequate time for the preparation, review and approval of the sequence.
- An adequate pre-job brief was conducted with all individuals involved in the preparation, review and approval of the sequence. The pre-job brief identified the procedures required for the activity including NF-AB-720, "Control Rod Sequence Package Preparation, Review, Revision and Implementation," Revision 2, and NF-DR-721, "Control Rod Sequences and Forms," Revision 3. Both procedures are classified as "Level 2 — Reference Use." Exelon procedure HU-AA-104-101, Revision 1, "Procedure Use and Adherence," defines the term "Level 2 — Reference Use" as a procedure requiring periodic referencing during the performance of an activity to confirm that all procedure segments of an activity have been performed, performing each step in the sequence specified and, where required, signing appropriate blocks to certify that all segments are completed. The procedure is required to be at the work location. Also, HU-AA-104-101 Step 4.3.2 states that all numbered steps are performed for "Level 1 — Continuous Use" and "Level 2 — Reference Use" procedures in sequence unless otherwise specified within the procedure or work order.
- No procedural inadequacies were identified that would prevent an individual from developing a startup sequence that complies with the control rod drop accident analysis as there are a number of references to the control rod drop accident analysis through use of the term "Analyzed Rod Sequence" in NF-AB-720 and NF-DR-721. Analyzed Rod Sequence is defined as the order of rod withdrawal or insertion that has been analyzed to conform to control rod drop accident analysis requirements below the Low Power Setpoint utilizing a NRC approved methodology.
- The evaluation did identify that the preparation and independent review of the control rod group pull sequence was flawed because the sequence developed by the DNPS personnel did not follow procedural requirements to develop a sequence that complies with the control rod drop accident analysis.
The following statements provided by DNPS personnel associated with this event confirmed this conclusion.
- A detailed review of the sequencing procedures was not performed when preparing the startup sequence due to the procedures being Reference Use — Level 2.
- A detailed review of the sequencing procedures was not performed when preparing the startup sequence, only selected sections were reviewed because the individual believed they knew how to perform the task and the procedures are 'reference use'. The individual's understanding of 'reference use' meant that all, part, or none of the procedure is reviewed based on the individual's confidence in their ability to perform the task.
- The sequencing procedures were reviewed during the independent review of the startup sequence. The independent reviewer stated that it was assumed that the control rod drop accident analysis for Unit 2 was the same as Unit 3 and the individual knew what was in the Unit 3 analysis.
The corrective action to prevent recurrence of this event was to counsel and coach the individuals associated with this event.
A review of the control rod group pull sequence for the startup of DNPS Unit 3 following the refuel outage in November 2006 did not identify any flaws.
D. Safety Analysis:
The safety significance of the events is minimal. A vendor analysis of the control rod group pull sequence used on November 19, 2007 for Unit 2 startup confirmed that the control rod drop accident analysis was met. Therefore, the consequences of the events had minimal impact on the health and safety of the public and reactor safety.
E. Corrective Actions:
The corrective action to prevent recurrence of this event was to counsel and coach the individuals associated with this event.
The requirements for the use of a "Level 2-Reference Use" procedure as specified in procedure HU AA-104-101 was discussed with the individuals involved in this event.
A sample of documents prepared by DNPS reactor engineering personnel to a "Level 2-Reference Use" procedure will be reviewed for procedure compliance.
F. Previous Occurrences:
A review of DNPS LERs for the last three years did not identify any LERs associated with human performance that was attributed to failure of DNPS personnel to follow procedures due to a lack of understanding of the requirements for using a Level 2 procedure or assuming that the "Level 2 - Reference Use" procedures did not need to be reviewed in detail during work.
G. Component Failure Data:
NA