ENS 44120
ENS Event | |
|---|---|
16:59 Apr 4, 2008 | |
| Title | Accident Mitigation - Common Control Room Emergency Air Conditioning System |
| Event Description | Salem Unit 1 was placed in a configuration that affected the ability to mitigate the consequences of an accident due to an inadvertent actuation of the common control room emergency air conditioning system (CREACS). CREACS was actuated as a result of an invalid Control Room air intake duct radiation monitor initiated on April 4, 2008 at 1259 hours0.0146 days <br />0.35 hours <br />0.00208 weeks <br />4.790495e-4 months <br />. Salem Unit-2 is currently defueled. Salem Unit 1 is in Mode 1 at 100% power. Unit 1 has two shutdown LCOs in effect. The first is for the CREACS system, which is shared between Unit 1 & 2, being aligned for single train operation with the Unit 2 CREACS train out of service per LCO 3.7.6. The second shutdown LCO is for two outside air intake dampers being inoperable for scheduled maintenance. With Unit 2 having an invalid Radiation Monitor signal, the CREACS system actuates in accident pressurized mode. This mode of actuation starts the CREACS fans, isolates the Control Room Envelope from the normal control room ventilation system and aligns the two sets of CREACS outside air intake dampers. With a Unit 2 Radiation Monitor signal, the Unit 2 CREACS intake dampers close and the Unit 1 CREACS intake dampers open. These damper positions are locked in until manually reset. With only one train of CREACS operable, the dose analysis indicates that the requirements of General Design Criterion (GDC) 19 can only be met during the worst case design basis accident if the Unit 1 CREACS intake dampers are closed and the Unit 2 CREACS intake dampers open. Therefore, until the CREACS intake dampers were reset and realigned, Salem Unit 1 would not have been able to mitigate the consequences of an accident and is reportable in accordance with 10CFR50.72(b)(3)(v)(D). The CREACS system actuation was reset after the failed radiation monitor (1R1B ch II) was removed from service and the dampers were re-aligned to their pre actuation alignment at 1316 hours0.0152 days <br />0.366 hours <br />0.00218 weeks <br />5.00738e-4 months <br />, restoring Salem Unit 1 to within the assumptions of the dose analysis. Total duration in the condition was 17 minutes.
The only piece of major equipment out of service on Salem Unit 1 is the 15 Service water pump which is out of service for scheduled maintenance. The Licensee notified the NRC Resident Inspector.
On April 4, 2008 Salem Unit 1 was placed in a configuration that was contrary to the current dose analysis of record due to an inadvertent actuation of the common control room emergency air conditioning system (CREACS). CREACS was initiated as a result of an invalid actuation of a Control Room air intake duct radiation monitoring channel (1R1B ch II). At the time of the actuation, the Unit 2 train of CREACS was out of service due to scheduled maintenance leaving only the Unit 1 CREACS train operable. Unit 1 was at 100% power and Unit 2 was defueled. With one train of CREACS out of service at the start of an accident the dose analysis of record requires that the CREACS emergency intake dampers for the unit having the accident to close and for the opposite units emergency intake dampers to open. The actuation of the radiation monitoring channel 1R1B channel II caused the Unit 1 emergency intake dampers to open which was contrary to the dose analysis of record. Subsequent to this event, an evaluation was performed utilizing the assumptions of the dose analysis of record with the exception of the actual measured engineered safety feature system leakage outside containment and the atmospheric dispersion factors (x/Q) associated with the Unit 1 CREACS intake. Based upon this evaluation, the CREACS system with one filtration train operable and the emergency intakes open on Unit 1 would have been able to maintain doses to the Control Room operators below the limits of GDC-19 and the dose analysis of record. Since the CREACS system was capable of performing its accident mitigation function, this event is being retracted. The licensee will notify the NRC Resident Inspector. Notified R1DO (Schmidt) |
| Where | |
|---|---|
Salem  New Jersey (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:+0.67 h0.0279 days <br />0.00399 weeks <br />9.17766e-4 months <br />) | |
| Opened: | John Garecht 17:39 Apr 4, 2008 |
| NRC Officer: | John Knoke |
| Last Updated: | Apr 17, 2008 |
| 44120 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |