05000461/FIN-2012002-01
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Finding | |
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| Title | Evaluation of Apparent Nonconforming Condition Affecting Circulating Water Pump Auto Stop Feature During a Flooding Event |
| Description | The inspectors opened an Unresolved Item (URI) pending evaluation of an issue that affects the function of a flood protection design feature intended to automatically stop running CW pumps in the event of flooding in the Turbine Building Condenser Pit. As described in the UFSAR (Sections D3.6.4 and 10.4.5.5), each condenser cavity designed to contain flooding to Elevation 715 is equipped with a redundant system of level switches, which will alarm in the Control Room if the water level in the condenser cavity reaches an elevation of more than 1 foot (Elevation 710) above the condenser cavity floor at Elevation 709. These level switches will close a motor-operated valve in the floor drain piping between the condenser cavity and the Turbine Building floor drain sump to slow flooding of the Turbine Building. Isolating the condenser pit from the Turbine Building floor drain sump slows early flooding of the Turbine Building basement. A second system of redundant level switches will automatically stop the CW pumps if the flood water reaches an elevation of 714 within the condenser cavity. An additional foot, from Elevation 714 to Elevation 715 remains to contain the water flow due to coast down of the CW pumps after they are initially shut off. Neither set of level switches are safety related; however, they are important internal flooding mitigation features as described in the UFSAR. During review of Action Requests (ARs) 01192988 and 01197763, the inspectors noted that operators discussed a known design issue affecting the function of the CW pump auto stop feature. If CW Pump A has power removed then all CW pump tripping protection is lost during a flooding event. With power removed from CW Pump A, CW Pumps B and C would not auto stop during a flooding event because the tripping power comes through the CW Pump A tripping fuses. This appeared to the inspectors to be a nonconformance with the UFSAR description under the above specified circumstance. This design issue has apparently been known by operators for many years, yet no engineering evaluation was performed for the condition and no corrective action other than a procedure enhancement has been initiated by the licensee to address it. As stated in AR 01197763: Another lesson learned was to plan ahead for off service CW pumps and that if possible, do not have A CW Pump tagged out due to this removes the CW pump trip on high-high CW Pit level. The procedure for isolating a waterbox requires tagging out the off-service CW pump to preclude inadvertent start. Having this trip defeated while performing an evolution with the potential to cause CW Pit flooding is contrary to good industrial safety practices. The inspectors reviewed CPS 3113.01, Circulating Water (CW), Revision 37e, and noted that Step 4.11 described the condition. The High-High level (~714) in the Condenser Pit CW Pump Trip Circuitry is electrically powered by 1CW01PA DC [direct current] control power. If the A pump is de-energized, then no CW pump tripping will be received from condenser pit flooding. The 710 floor drain sump floats which give Main Control Room alarm and 1TF013 valve closure would be the only indication of flooding. The inspectors discussed this issue with the licensee and in response to the inspectors questions; the licensee initiated AR 01355130 to evaluate the design concern. This issue is considered to be an Unresolved Item pending additional review of the licensees evaluation by the inspectors |
| Site: | Clinton  |
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| Report | IR 05000461/2012002 Section 1R06 |
| Date counted | Mar 31, 2012 (2012Q1) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.06 |
| Inspectors (proximate) | B Kemker C Brown D Lords D Szwarc J Bozga J Cassidy M Ring R Orlikowski S Bell S Mischkeb Kemkerd Lords D Reeser M Phalen M Ring R Walton S Mischke |
| INPO aspect | |
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Finding - Clinton - IR 05000461/2012002 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Clinton) @ 2012Q1
Self-Identified List (Clinton)
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