05000395/LER-2013-006
| Virgil C. Summer Nuclear Station Unit 1 | |
| Event date: | 12-04-2013 |
|---|---|
| Report date: | 01-31-2014 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3952013006R00 - NRC Website | |
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2. DOCKET
05000 395 2 OF 3 I REV 2013 - 006 - 0
PLANT IDENTIFICATION
Westinghouse — Pressurized Water Reactor
EQUIPMENT IDENTIFICATION
Control Room Ventilation 1.0 EVENT DESCRIPTION On December 4, 2013, at approximately 1027 EST, 'B' train Control Room (CR) ventilation was in the emergency recirculation mode of operation as required by Technical Specification (TS) 3.3.3.1, Action 29. This Technical Specification action requires that the CR ventilation be in the emergency recirculation mode of operation when the radiation monitor RMA0001 is out of service.
An 18/C technician was calibrating the Control Room Supply Air Atmospheric Radiation Monitor using Surveillance Test Procedure 360.031. An operator was assisting using the system operating procedure (SOP)-505 Control Building Ventilation System. The 18/C technician could not complete the test because the A relay room recirculation damper position could not be verified. The l&C technician told the operator he needed to back out of the procedure and return the Control Room Ventilation back to normal. When 18/C stated to place CR ventilation back to normal the operator understood this to mean, place ventilation back in normal mode even though RMA0001 was still considered inoperable for the test.
The operator followed the SOP-505, Control Building Ventilation System, and restored CR Ventilation to normal lineup.
Control Room Emergency Ventilation was secured for approximately 30 seconds. This was a violation of Technical Specification 3.3.3.1 table 3.3-6 action 29 states: With the number of channels operable less than required by the Minimum Channels operable requirement, within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> initiate and maintain operation of the control room emergency ventilation system in the emergency mode of operation. Condition Report (CR) 13-05083 was generated to document the event and an apparent cause evaluation was performed to determine the appropriate corrective actions.
2.0 EVENT ANALYSIS In the emergency recirculation mode of operation, the CR ventilation is required to remove particulates and radioiodines such that access to and occupancy of the control room under accident conditions and for the duration of the accident does not result in personnel exposures in excess of 5 REM whole body, in accordance with 10 CFR 50 Appendix A, General Design Criteria 19.
FSAR Ch.9.4.1 states the recirculation of CR ventilation is needed upon receipt of a safety injection or high radiation signal from the gaseous activity channel of RM-A1, the system automatically places the dampers in the emergency mode and starts the normal air handling unit and emergency filter fan.
The Control Room Supply Air, Channel RM-A1 is further described in FSAR 12.2.4.2.1. This channel monitors the particulate, iodine, and gaseous activity of air supplied to the control room. A sample of air is taken from the air supply duct through an isokinetic sampler nozzle and is drawn successively through a particulate sampler, an iodine sampler, and a gas sampler. Instrumentation and control is provided to detect abnormal conditions, such as smoke, high temperature or high radiation levels which require operation in a recirculation mode, emergency filtration mode or outside air purging mode.
The cause of the event was human error. The operator mistakenly proceeded to a step in the system operating procedure to return the system to normal which resulted in securing Control Room Emergency Ventilation. Had the operator confirmed this request with shift supervision he would have been directed to not restore CR Ventilation to normal.
3.0 SAFETY SIGNIFICANCE The safety significance of this event was minimal. There were no other system interactions affected by this condition.
There were no releases during the 30 seconds that the Control Room was not in emergency ventilation.
4.0 CORRECTIVE ACTIONS Condition Report (CR) 13-05083 was generated to document the event and results of the apparent cause evaluation.
Station procedure enhancements are being considered.
5.0 PREVIOUS OCCURRENCE A review of operating history identified one previous event related to this event. LER 2006-01-00 was generated due to an event on May 18, 2006 at 2117 EST. This event was associated with, 'B' train Control Room (CR) ventilation was in the emergency recirculation mode of operation as required by Technical Specification (TS) 3.3.3.1, Action 29. RMA 1 was out of service while being calibration tested using Surveillance Test Procedure (STP) 360.031.