05000324/LER-2007-001
| Brunswick Steam Electric Plant (Bsep) | |
| Event date: | 03-26-2007 |
|---|---|
| Report date: | 05-22-2007 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3242007001R00 - NRC Website | |
Energy. Industry Identification System (EIIS) codes are identified in the text as [XX].
Introduction Initial Conditions At the time of this event, Unit 2 was in Mode 5. Three of four source range monitors (SRMs) [IG] were operable. The fourth SRM had been declared inoperable due to spiking, however, it was available and providing an accurate count rate. No other core alterations were in progress.
Reportability Criteria Surveillance Requirement (SR) 3.3.1.2.2 of Technical Specification (TS) 3.3.1.2, "Source Range Monitor Instrumentation," requires, in part, that there be an operable source range monitor (SRM) in the core quadrant where core alterations are being performed. Contrary to this requirement, control rod [AA] 10-35 was withdrawn a single notch in a fueled quadrant of the core where there was not an operable SRM. This condition is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B) as operation prohibited by the plant's TSs.
Event Description
On March 26, 2007, at approximately 1015 hours0.0117 days <br />0.282 hours <br />0.00168 weeks <br />3.862075e-4 months <br /> (EDT), Operations began returning seven Unit 2 control rods to service. These control rods had been removed from service for position indicating probe (PIP) maintenance and replacement. The post-maintenance testing for this activity requires the control rods to be withdrawn one notch (i.e., to position 02) to verify that the "Full-In" indicating light extinguishes and then to be re-inserted to full-in position. Plant procedure 20P-08, "Control Rod Drive Hydraulic System Operating Procedure," governs performance of this testing. Prior to initiating this activity, two Senior Reactor Operators (SROs) (i.e, a SRO assigned to control rod drive activities and the Unit SRO) reviewed TS requirements for control rod movement in Mode 5, including TS Table 3.3.1.2-1, "Source Range Monitor Instrumentation." For Mode 5, TS Table 3.3.1.2-1 requires two operable SRM channels. SRMs B, C, and D were operable. SRM A was considered inoperable due to spiking. However, SRM A was available and providing an accurate count rate. The Unit SRO confirmed, with a Control Operator, that TS surveillances required to support the control rod movement were current. Based on these actions, authorization to begin the control rod testing was provided. However, SR 3.3.1.2.2 requires that, during core alterations, an operable SRM be located in: (a) the fueled region, (b) the core quadrant where core alterations are being performed, when the associated SRM is included in the fueled region, and (c) a core quadrant adjacent to where core alterations are being performed, when the associated SRM is included in the fueled region. Since SR 3.3.1.2.2 was previously performed within the 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> frequency, the SROs did not refer to SR 3.3.1.2.2 when authorizing testing of the seven control rods. Restoration of the seven control rods was completed by approximately 1130 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.29965e-4 months <br /> on March 26, 2007.
Event Description (continued) Subsequently, during performance of SR 3.3.1.2.2, per procedure 201-03.2, "Control Operator Daily Surveillance Report," in preparation for additional control rod manipulations related to venting and timing, a Reactor Operator questioned verbiage in the procedure which indicated that an operable SRM was required in the quadrant where core alterations are being performed. At this point, it was recognized that control rod 10-35 had been withdrawn during the previous testing evolution and that this rod was located in the same core quadrant as the inoperable SRM A. As stated above, SR 3.3.1.2.2 was current when the SROs previously authorizing testing of the seven control rods. As such, procedure 201-03.2 was not reviewed until re-performance of SR 3.3.1.2.2 became necessary.
Event Cause The root cause of this event was inadequate procedures. Existing operating procedures did not provide adequate guidance identifying prerequisites required to be met prior to performing core alterations, due to control rod movement.
Additionally, although not the root cause of the event, the detailed Limiting Condition for Operation (LCO) requirements within SR 3.3.1.2.2 (i.e., specific location requirements for operable SRMs) were not provided in the LCO requirements contained in Table 3.3.1.2-1. This is not typical of the format of the improved Standard Technical Specifications GE Plants, BWR/4 (i.e., NUREG-1433, Revision 3.1). This non-typical format, which matches the existing NUREG-1433, was a contributing factor to the event. Had Table 3.3.1.2-1 included the operability requirements consistent with those of SR 3.3.1.2.2, the LCO requirements would have been identified when the SROs referred to the table.
Safety Assessment The safety significance of this condition is considered minimal.
Control Operators were monitoring all SRM indications during movement of control rod 10-35, including SRM A which, although inoperable, was providing an accurate count rate. No abnormal indications were noted. Additionally, the control rod was withdrawn only one notch. Therefore, there was no potential for inadvertent criticality.
Corrective Actions
The following corrective actions to prevent recurrence have been established as a result of this event.
- Plant procedures 1(2)OP-08 will be revised to include an attachment used to verify all prerequisites are met prior to moving a control rod in various modes of operation. These revisions are currently scheduled to be completed by July 17, 2007.
Corrective Actions (continued
- Other plant procedures which could result in a core alteration due to movement of a control rod will be reviewed to determine their adequacy. This review is currently scheduled to be completed by July 17, 2007.
Although not intended to prevent recurrence, the following corrective action is planned.
- A license amendment request will be submitted to revise TS Table 3.3.1.2-1, "Source Range Monitor Instrumentation," to include operability requirements consistent with SR 3.3.1.2.2. The amendment request is currently scheduled to be submitted by August 16, 2007.
Previous Similar Events
A review of LERs and corrective action program condition reports for the past three years identified the following similar event.
- LER 1-2005-003, dated June 16, 2005, documents operation prohibited by TSs that occurred when LCO 3.0.5 was misapplied resulting in control rod 46-15 being inappropriately re-armed. The corrective actions associated with LER 1-2005-003 could not have reasonably been expected to prevent the condition reported in this LER.