ENS 49279
ENS Event | |
|---|---|
05:30 Aug 14, 2013 | |
| Title | Valve Failed to Close as Required on Low Temperature Interlock |
| Event Description | At 2230 [PDT] on 8/13/2013, AREVA Richland Dry Conversion Operations notified AREVA Safety personnel that a low temperature interlock on one of the uranium hexafluoride (UF6) headers activated and that the valve, HV1-1054, did not close as required, and therefore the process has been shut down pending investigation. The system remains down and will remain down pending thorough investigation and appropriate corrective actions.
The low temperature interlock is not an IROFS [Item Relied on for Safety]. However, further investigation this morning determined the valve, HV1-1054, impacted the function of four IROFS, which would not have performed as required. Of these four, two were found to be used in accident sequences that only credited one additional IROFS for nuclear criticality accident sequences. In each of the cases accidental nuclear criticality remained highly unlikely due to the robustness of the remaining IROFS and the low occurrence frequency of the initiating event. Operating with only one IROFS to protect against accidental nuclear criticality is reported within one hour of discovery under 10CFR70 Appendix A criterion (a)(5). AREVA determined that this criterion had been met at approximately 0900 [PDT, on 8/14/2013]. It is estimated that this particular process line had operated for less than 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> in this condition. The licensee has notified NRC Region II.
Based on the following discussion, AREVA formally withdraws the notification made in NRC event 49279 with this update. After careful review of this plant condition, the apparent causes and the extent of condition, AREVA NP has concluded that the plant condition that precipitated the initial notification did not meet the criteria for reporting to the NRC under 10CFR70 Appendix A. This conclusion is based primarily on the fact that closure of valve HV1-1054 (for UF6 isolation) was not required to meet the safety function specified by the IROFS credited to prevent the accident sequences related to this plant condition. Specifically, the temperature triggers for IROFS 1005, 1006, and 1018 each activate both the UF6 Isolation and the Reaction Gas Shutoff interlocks. The UF6 isolation interlock causes valve HVx-1054 to close. However, UF6 isolation was not required to meet the safety function specified for IROFS 1005, 1006, and 1018. AREVA was compliant with the performance requirements of 10CFR70.61 at all times during the condition reported to the NRC on 8/14/2013. A more detailed write-up of this conclusion was previously provided to NRC Region II and additional information will be provided to them later today [9/6/13]. Notified R2DO (Ernstes) and NMSS (Guttmann). |
| Where | |
|---|---|
| Areva Np Inc Richland Richland, Washington (NRC Region 2) | |
| License number: | SNM-1227 |
| Reporting | |
| Part 70 App A (A)(5) | |
| Time - Person (Reporting Time:+7.03 h0.293 days <br />0.0418 weeks <br />0.00963 months <br />) | |
| Opened: | Calvin Manning 12:32 Aug 14, 2013 |
| NRC Officer: | John Shoemaker |
| Last Updated: | Sep 6, 2013 |
| 49279 - NRC Website | |
Areva Np Inc Richland with Part 70 App A (A)(5) | |
WEEKMONTHYEARENS 494752013-10-27T17:55:00027 October 2013 17:55:00
[Table view]Part 70 App A (A)(5) Failure of a Steam Supply Vacuum Breaker ENS 492792013-08-14T05:30:00014 August 2013 05:30:00 Part 70 App A (A)(5) Valve Failed to Close as Required on Low Temperature Interlock ENS 473602011-10-20T16:10:00020 October 2011 16:10:00 Part 70 App A (A)(5) One Hour Report Due to a Failed Item Relied on for Safety ENS 433972007-05-31T23:40:00031 May 2007 23:40:00 Part 70 App A (A)(5) One Hour Report Notification: Combustible Material Exceeding Item Relied on for Safety (Irofs) Limits Found 2013-08-14T05:30:00 | |