ENS 45675
ENS Event | |
|---|---|
19:44 Feb 3, 2010 | |
| Title | Technical Specification Shutdown Required Due to Control Rod Out of Alignment |
| Event Description | A shutdown of South Texas Project Unit 1 was initiated at 13:44 hours [CST] on February 3, 2010. When in Action b.2. of Technical Specification (TS) 3.1.3.1, 'Moveable Control Assemblies Group Height,' a second control rod, B-12, in Shutdown Bank A was declared inoperable when the rod came out of alignment with the remainder of the rods within its bank. The second control rod came out of alignment during the performance of Surveillance Requirement 4.1.3.1.2; a surveillance to determine operability by movement of the rod.
For the above condition, Action c. of TS 3.1.3.1 was entered. When the requirements of the action could not be met, South Texas Project Unit 1 entered TS 3.0.3. and a plant shutdown was initiated. Prior to initiation of this event, South Texas Project Unit 1 was in Action b.2 [of TS 3.1.3.1] with rod C-5 of Shutdown Bank D trippable but inoperable due to causes other than addressed by Action a. The inoperable rod, C-5, was aligned within 12 steps of the remainder of the rods within its group and the rod sequence and insertion limits as specified in the Core Operating Limits Report were being maintained. At the time of this report, South Texas Project Unit 1 was at 30% power and decreasing. The plant will enter Mode 3, Hot Shutdown, at approximately 1800 CST. Shutdown was initiated when rod B-12 could not be aligned within 12 steps of the remainder of rods within its bank as specified in Action c. of TS 3.1.3.1. The licensee has notified the NRC Resident Inspector.
At 1730 [CST] during performance of the Unit 1 shutdown, control rod H-2 in Bank 1C inserted from 246 steps, as indicated by the digital rod-position indication system, to 234 steps indicated without a demand signal applied to the control bank. The group step counter remained at 249 steps with no other rods in Bank 1C indicating movement. The shutdown continued normally from that point. Control rod H-2 stepped with the rest on the rods in the bank down to zero steps. All control rods in Unit 1 are at zero steps. The shutdown rods are currently withdrawn. The licensee has notified the NRC Resident Inspector. Notified R4DO (Gaddy).
This update corrects information provided earlier at 2230 EST on February 3, 2010 after reviewing post shutdown data. During the performance of the Unit 1 shutdown, control rod H-2 in Bank 1C inserted upon demand, as indicated by the digital rod-position indication system, but did not withdraw upon demand, as indicated. This occurred when controlling Bank 1C between 249 and 242 steps by alternating insertion and withdrawal demand signals to control reactivity. At approximately 1731, the shutdown continued normally from that point. Control rod H-2 stepped in with the rest of the rods in the bank down to zero steps. All control rods and shutdown rods in Unit 1 were subsequently driven in to zero step position. The licensee notified the NRC Resident Inspector. Notified R4DO (Gaddy). |
| Where | |
|---|---|
South Texas  Texas (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | |
| Time - Person (Reporting Time:+-3.1 h-0.129 days <br />-0.0185 weeks <br />-0.00425 months <br />) | |
| Opened: | Billy Herzog 16:38 Feb 3, 2010 |
| NRC Officer: | Howie Crouch |
| Last Updated: | Feb 5, 2010 |
| 45675 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (30 %) |
WEEKMONTHYEARENS 456752010-02-03T19:44:0003 February 2010 19:44:00
[Table view]10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Technical Specification Shutdown Required Due to Control Rod Out of Alignment ENS 413922005-02-09T18:22:0009 February 2005 18:22:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown, 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded Technical Specification Required Shutdown Due to Unisolable Pressure Boundary Leak 2010-02-03T19:44:00 | |