ENS 49476
ENS Event | |
|---|---|
21:30 Oct 27, 2013 | |
| Title | |
| Event Description | At 1730 EDT on 10/27/2013, SQN [Sequoyah Nuclear] discovered that Unit 1 containment penetration X-108 had a maintenance flange installed with a service air connection attached. The service air connection was connected to a temporary air compressor supplying air to maintenance loads inside Unit 1 containment. Contrary to the requirements of the breaching permit, personnel were not stationed at the penetration to isolate the service air connection in the event of the air line rupturing inside Unit 1 containment or upon initiation of an auxiliary building isolation signal. Since the Unit 1 containment is open to the auxiliary building as part of outage activities, if the service air line had ruptured, the additional air into the Unit 1 containment could have exceeded the capacity of the Auxiliary Building Gas Treatment System (ABGTS) and potentially have impacted the ability of the ABGTS to perform its design safety function. This resulted in both trains of the ABGTS being declared inoperable requiring Unit 2 to enter the action of LCO 3.0.3. The service air line was isolated immediately and Unit 2 exited the action of LCO 3.0.3 at 1732 EDT. At the time of the event, Unit 1 was defueled and did not require ABGTS to be operable. Unit 1 subsequently entered Mode 6 at 1904 EDT on 10/27/2013 and is currently conducting refueling operations. Unit 2 remains in Mode 1, 100% power and stable. There were no actual operational impacts to either unit.
The licensee has notified the NRC Resident Inspector.
Sequoyah Nuclear Plant, Units 1 and 2, are retracting the 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> non-emergency notification made on October 27, 2013 at 2229 EDT (EN# 49476). The notification on October 27, 2013, reported that if the service air line (associated with penetration X-108) had ruptured, the additional air into the Unit 1 containment could have exceeded the capacity of the Auxiliary Building Gas Treatment System (ABGTS) and potentially have impacted both trains of ABGTS from performing its safety function(s). Subsequent engineering analysis concluded acceptable margin was available. Both trains of ABGTS would have remained operable and capable of performing its design function(s) at all times. The engineering analysis results are captured in the licensee's corrective action program. Based on the new analysis, the condition reported in EN #49476 did not result in a potential uncontrolled radioactive release. This event report is being retracted. The NRC Resident Inspector has been briefed on the analysis results and informed of this retraction. Notified R2DO (McCoy). |
| Where | |
|---|---|
Sequoyah  Tennessee (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | |
| Time - Person (Reporting Time:+0.98 h0.0408 days <br />0.00583 weeks <br />0.00134 months <br />) | |
| Opened: | Matthew Leenerts 22:29 Oct 27, 2013 |
| NRC Officer: | John Shoemaker |
| Last Updated: | Jan 30, 2014 |
| 49476 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |