ENS 40272
ENS Event | |
|---|---|
20:40 Oct 23, 2003 | |
| Title | Nonemergency Notification Due to Failure to Maintain Control Structure Habitability Envelope |
| Event Description | During routine monitoring, Control Room personnel noted control structure pressure differential was below the 1/8" [inches of water pressure] required to maintain the Control Structure Habitability Envelope. A walkdown of the Control Structure and initial investigation has revealed no obvious problems that would cause the low positive pressure condition. Due to the inability of the Control Structure HVAC to maintain a positive pressure, both trains of Control Room Emergency Outside Air Supply system were declared inoperable. This is considered a Loss of Safety Function in accordance with 10 CFR 50.72(b)(3)(v)(D).
The licensee has notified the NRC Resident Inspector.
At the time of the original 8-hour ENS notification was made, both trains of the Control Room Emergency Outside Air Supply (CREOAS) system were declared inoperable due to the failure of the Control Structure HVAC system to maintain the control structure habitability envelope at a pressure greater than + 1/8" w.g. [water gauge] with respect to outside atmosphere. Subsequent to this event, an evaluation was performed which determined that the requirement to maintain the control structure habitability envelope at a pressure greater than + 1/8" w.g. is only applicable during emergency operating conditions. Under emergency conditions, the CREOAS system, in conjunction with the Control Structure HVAC system, is required to maintain control structure pressure greater than + 1/8" w.g. in accordance with Technical Specification 3.7.3. However, during normal plant operation, the design function of the Control Structure HVAC system is to maintain the habitability envelope at a positive pressure above atmospheric. No specific value is required. Differential pressure readings for the control structure indicated that pressure was maintained above atmospheric at the time of this event. On October 24, 2003, surveillance testing successfully demonstrated that the Control Structure HVAC and CREOAS systems were capable of maintaining the control structure habitability envelope at a pressure greater than + 1/8" w.g. As such, there was no loss of safety function. The licensee has notified the NRC Resident Inspector. Notified R1DO (A. Della Greca) |
| Where | |
|---|---|
Susquehanna  Pennsylvania (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+0.83 h0.0346 days <br />0.00494 weeks <br />0.00114 months <br />) | |
| Opened: | Gordon Robinson 21:30 Oct 23, 2003 |
| NRC Officer: | Jeff Rotton |
| Last Updated: | Dec 12, 2003 |
| 40272 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |