ENS 48949
ENS Event | |
|---|---|
08:22 Apr 20, 2013 | |
| Title | Accident Mitigation - Common Control Room Emergency Air Conditioning System |
| Event Description | Salem Unit 2 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 signal initiated on April 20, 2013 at 0422 hours0.00488 days <br />0.117 hours <br />6.977513e-4 weeks <br />1.60571e-4 months <br /> [EDT].
Salem Unit 1 is currently in Mode 6 with core offload in progress. Salem Unit 2 is in Mode 1 at 100% power. Unit 2 has two shutdown LCOs in effect. The first is for the CREACS, which is shared between Unit 1 & 2, being aligned for single train operation with the Unit 1 CREACS train out of service per LCO 3.7.6. The second shutdown LCO is for single source of offsite power due to scheduled maintenance. With Unit 1 having an invalid radiation monitor signal, the CREACS automatically aligned to 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 1 radiation monitor signal the Unit 1 CREACS intake dampers close and the Unit 2 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 Criteria (GDC) 19 can only be met during the worst case design basis accident if the Unit 2 CREACS intake dampers are closed and the Unit 1 CREACS intake dampers [are] open. Therefore, until the CREACS intake dampers were reset and realigned, Salem Unit 2 would not have been able to mitigate the consequences of an accident and is reportable in accordance with 10CFR50.72(b)(3)(v). The CREACS system actuation was reset after the failed radiation monitor (2R1B ch. II) was removed from service and the dampers were realigned to their pre-actuation alignment at 0457 hours0.00529 days <br />0.127 hours <br />7.556217e-4 weeks <br />1.738885e-4 months <br />, restoring Salem Unit 2 to within the assumptions of the dose analysis. Total duration in the condition was 35 minutes. The only pieces of major equipment out of service on Salem Unit 2 are the 4 Station Power Transformer and 23 Station Power Transformer which are out of service for scheduled maintenance." The licensee will notifying Lower Alloways Creek township and the NRC Resident Inspector.
On April 20, 2013, Salem Unit 2 was placed in a configuration that was contrary to the current dose analysis of record due to an invalid actuation of the common Control Room Emergency Air Conditioning System (CREACS). The CREACS was initiated as a result of an invalid actuation of Control Room Air Intake Duct Radiation Monitoring Channel, 2R1B Channel 2. At the time of the actuation, the Unit 1 Train of CREACS was out of service due to scheduled maintenance leaving only the Unit 2 CREACS train operable. Unit 2 was at 100% power and Unit 1 was in Mode 6. With one train of CREACS out of service at the start of an accident the dose analysis of record requires that the CREACS Emergency Air Intake Dampers for the accident unit go closed and the opposite unit's emergency intake dampers go open. The actuation of the radiation monitoring channel 2R1B Channel 2 caused the Unit 2 Emergency Air Intake Dampers to open. If a design basis LOCA were to have occurred on Unit 2 during that period the alignment would have been 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 two exceptions. Actual measured Engineered Safety Feature system leakage outside containment and Containment Leakage at the time of the event were utilized in the evaluation. This evaluation determined that if a design basis LOCA had occurred on Unit 2 with the CREACS in accident pressurized mode with Unit 1 Emergency Intake Dampers closed and Unit 2 Emergency Intake Dampers opened, Control Room design dose limits would not have been exceeded. Based upon this evaluation, the CREACS system would have been able to maintain dose to Control Room operators below the limits of GDC-19 and the dose analysis of record. Since the CREACS was capable of performing its accident mitigation function, this event is being retracted." The licensee will notify the NRC Resident Inspector. Notified R1DO (Dentel). |
| 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:+1.4 h0.0583 days <br />0.00833 weeks <br />0.00192 months <br />) | |
| Opened: | Harry Wiedman 09:46 Apr 20, 2013 |
| NRC Officer: | Pete Snyder |
| Last Updated: | Jun 13, 2013 |
| 48949 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |