ENS 50457
ENS Event | |
|---|---|
13:00 Sep 15, 2014 | |
| Title | Failed Fuel Assembly Identified During Core Off-Load |
| Event Description | With North Anna Unit 2 in Mode 6 during a scheduled refueling outage, discharged assembly 4Z9 was identified as a failed fuel assembly by In-Mast Sipping. The fuel assembly was located in core location B11. Initial inspection of the fuel assembly identified two (2) visibly split fuel pins of eight (8) to ten (10) inches long with visible damage to the top of the pins. The internals of the affected pins are visible and the springs from the top of each pellet stack are touching the top nozzle. The fuel assembly has been placed into its designated location in the Spent Fuel Pool. No abnormal increase was noted on any radiation monitor either after or during fuel assembly movement. This fuel assembly had been used during three (3) previous operating cycles and is not scheduled for reuse.
On September 15, 2014, at 0900 [EDT], subsequent video inspection of the fuel assembly identified that the top springs of the two (2) fuel pins were dislodged. Video inspection of the reactor vessel identified debris that has the potential to be fragments of fuel pellets resting on the core plate. Additional investigations are in progress. Due to the fact that the failure exceeded expected conditions, this event is being reported per 10 CFR 50.72(b)(3)(ii)(A), as any event or condition that results in the condition of the nuclear plant, including its principle safety barriers, being seriously degraded. The licensee has notified the NRC Resident Inspector and will notify local county authorities.
Event Notification #50457 was provided on September 15, 2014, at 1454 hours0.0168 days <br />0.404 hours <br />0.0024 weeks <br />5.53247e-4 months <br />, pursuant to 10 CFR 50.72(b)(3)(ii)(A), to provide notification that North Anna Unit 2 discharged assembly 4Z9 had two visibly split fuel pins and debris on the core plate that had the potential to be fuel pellet fragments. Detailed video inspections estimated that fifteen (15) fuel pellets were dislodged from fuel assembly 4Z9. For reference, the reactor core contains approximately 15 million fuel pellets. Efforts to identify and recover the fuel pellets were performed. Debris fragments, estimated to represent five (5) fuel pellets, were located within the damaged fuel assembly that is currently in the spent fuel pool. In addition, an estimated three (3) pellets worth of material was retrieved by the foreign object search and retrieval (FOSAR) efforts in the reactor vessel. The remaining seven (7) fuel pellets have already or are expected to granulate into fine particles that will remain in low flow areas of the primary plant systems or be removed by normal purification processes. However, since the specific location of the seven (7) fuel pellets is undesignated, a report is being made pursuant to 10 CFR 74.11(a) for the loss of special nuclear material. The seven (7) fuel pellets contain licensed material in a quantity greater than 10 times the quantity specified in Appendix C of 10 CFR 20; therefore a report is also being made pursuant to 10 CFR 20.2201(a)(ii). The cause of the fuel clad degradation is understood and is being addressed. It has been evaluated that the dispersion of fuel pellet material will pose no threat to the integrity or operation of the reactor fuel and primary system components. Reactor Coolant System activity will remain below Technical Specification limits during power operation. In addition, there are no adverse radiological consequences to the public as a result of this issue. The licensee will be notifying the state of Virginia, local authorities in Louisa County and has notified the NRC Resident Inspector. Notified R2DO (Vias) and IRD (Stapleton). |
| Where | |
|---|---|
North Anna  Virginia (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded 10 CFR 74.11(a) 10 CFR 20.2201(a)(1)(ii) | |
| Time - Person (Reporting Time:+1.9 h0.0792 days <br />0.0113 weeks <br />0.0026 months <br />) | |
| Opened: | Page Kemp 14:54 Sep 15, 2014 |
| NRC Officer: | John Shoemaker |
| Last Updated: | Sep 30, 2014 |
| 50457 - NRC Website
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North Anna with 10 CFR 20.2201(a)(1)(ii), 10 CFR 74.11(a), 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | |
WEEKMONTHYEARENS 567742023-10-03T15:54:0003 October 2023 15:54:00
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