05000317/FIN-2011005-04
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Finding | |
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| Title | Inadequate Inspection of Floor Drains led to clogging and EDG Failure during hurricane |
| Description | The inspectors identified a Green NCV of TS 5.4.1, Procedures, because Constellation did not adequately implement the procedural requirements to conduct floor drain inspections. Specifically, operators did not ensure that floor drains were free to drain and clear of debris in the 80 foot elevation of the 1A EDG building. This contributed to the inoperability of the 1A EDG due to clogged floor drains during Hurricane lrene on August 28, 2011. During the evening of August 27, 2011, through the early morning of August 28, 2011, precipitation from Hurricane lrene entered the 1A EDG building top elevation through the air intake openings that allow air flow to support diesel operation. The water accumulated on the top elevation floor, flowed under a door to the 1A EDG combustion air intake piping, leaked through the combustion air intake piping penetration to the floors beneath, and dripped onto the 1A EDG speed switch. The wetted speed switch caused the 14 EDG field flash circuit to attempt to flash the magnetic field in the 1A EDG. Because the generator shaft was not turning, the magnetic field was not established. This condition resulted in a field flash too long alarm. Electrical maintenance personnel removed fuses to de-energize the field flash circuit in order to prevent damage to the circuit, preventing any subsequent 1A EDG start. As a result, Operations declared the 1A EDG inoperable. Electrical maintenance and operations personnel conducted a tour of the 1A EDG building and observed approximately two inches of water on the top elevation floor. The floor drains on the top elevation were backed up due to a paste like material that formed from dust, dirt, and pollen when the drain filters became wetted. After operators removed the drain filters, the drains were able to perform their function thereby eliminating the source of water leaking on the 1A EDG speed switch. Constellation conducted a RCAR to identify the cause of this event. The RCAR stated that the root cause of the event was a failure of combustion intake piping penetration (boot seal) to remain leak tight. The RCAR further stated that a contributing cause was a failure to perform an engineering evaluation when the drain filters were installed in the 1A EDG building in 2005. An engineering evaluation would have identified the need for a PM to clean and inspect the filters on a periodic basis. The inspectors determined that Constellation failed to identify that operators were not adequately implementing housekeeping requirements established in CNG-OP-1.01-20A0, Operations Log keeping and Station Rounds. Paragraph 4 of section 5.3.B, Auxiliary Operator Rounds, in CNG-OP-1.01-2000 stated that Plant Operators shall perform thorough inspections of their assigned area to include the following general inspection items and equipment checks as they conduct their routine duties and take appropriate actions to report and properly correct deficiencies noted. The inspectors noted that the general inspection items included floor drains and sump gratings free to drain and clear of debris. The inspectors interviewed several operations department personnel to verify the expectations regarding floor drains inspections. Discrepancies were identified on how to meet the requirements of CNG-OP-1.A12000. The inspectors concluded that Constellation did not maintain the floor drains clear of debris and free to drain, and determined that this was an additional contributing cause to the failure of the 1A EDG on August 28, 2011. Immediate corrective actions included entering this issue into their CAP, removing all the drain filters from the 1A EDG building, and installation of a curb around the combustion intake penetration. Planned corrective actions include replacing the combustion intake penetration boot seal. Constellation\'s failure to ensure that floor drains in the 1A EDG building were free to drain and clear of debris in accordance with procedures is a performance deficiency. The finding is more than minor because it is associated with the human performance attribute of the Mitigating System cornerstone and affected the cornerstone\'s objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences (i.e., core damage). A phase 3 SDP was required in accordance with IMC 0609, Attachment 4, phase 1- initial Screening and Characterization of Findings, Table 4b question 2c, because the finding degraded the 14 EDG, one train of a safety system, and is therefore potentially risk significant due to a seismic, flooding, or severe weather initiating event. A Region I SRA conducted the Phase 3 assessment of the finding utilizing the Calvert Cliffs Unit 1, Standardized Plant Analysis Risk model, version 8.15, in conjunction with the System Analysis Programs for Hands-On lntegrated Reliability Evaluations, version 8.0.7.17, dated May 1 8,2011, to estimate the severe weather risk contribution. Given that the condition impacted the availability of the 1A EDG during a severe weather event, the SRA made the following modeling changes and assumptions. The only initiating event of concern was a weather related loss of off-site power (LOOPWR). A new basic event, EPS-DGN-FS-H2O, was added to account for the condition in which water intrusion from high wind and rain would challenge the 1A EDG. Given the unique configuration of the building and weather conditions needed to challenge the EDG, a failure probability of 1E-1 was assigned. No adjustments were made to the LOOPWR frequency. This is considered conservative since this frequency also includes all weather related LOOPS. The condition existed for 1 year. Given that the finding did not impact the likelihood of a steam generator tube rupture or inter-system loss of coolant accident, large early release frequency was not impacted. The resulting change in core damage frequency was approximately 1.8E-7. The dominant sequence was a weather related loss of offsite power, with a failure of the emergency power system combined with a failure of turbine driven auxiliary feedwater and recovery of offsite power. Given this, the finding was determined to be Green. The finding has a cross-cutting aspect in the area of human performance, work practices, because Constellation did not ensure that personnel work practices support human performance by defining and effectively communicating expectations regarding procedural compliance and personnel following procedures. Specifically, Constellation did not establish and communicate clear expectations to operators on the implementation of the floor drain inspection in accordance with their procedures (H.4.b per IMC 0310). TS 5.4.1, Procedures, states in part, that written procedures shall be established, implemented and maintained in accordance with Regulatory Guide (RG) 1.33, Revision 2, Appendix A, recommended procedures\' RG 1.33, Appendix A, section 1.b , Administrative procedures, requires procedures for Authorities and Responsibilities for Safe Operation and Shutdown. CNG-OP-1.01-2000 establishes the controls, standards and expectations for the monitoring of plant equipment, components, and the recording of Operating Log readings, including Operating Logs, Narrative Logs, and Station Rounds. Section 5.9.8, step 4.a, states, in part, that plant operators shall perform thorough inspections of their assigned areas to include the inspection of floor drains and sump gratings to ensure they are free to drain and clear of debris. Contrary to this, prior to August 28,2011, Constellation failed to adequately implement the guidance in CNG--OP-1.01-2000 to ensure that floor drains in the 1A EDG building were free to drain and clear of debris. This contributed to the inoperability of the 1A EDG due to clogged floor drains during Hurricane Irene on August 28,2011. Because this violation was of very low safety significance and it was entered into Constellation\'s CAP as CR-201 1-00870b and CR-2012-00051 1, this violation is being treated as an NCV, consistent with the Enforcement Policy. |
| Site: | Calvert Cliffs  |
|---|---|
| Report | IR 05000317/2011005 Section 4OA3 |
| Date counted | Dec 31, 2011 (2011Q4) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | D Silk S Pindale G Dentel P Presby S Kennedy D Kern R Rolph J Hawkins E Torres K Cronk M Jennerich |
| CCA | H.8, Procedure Adherence |
| INPO aspect | WP.4 |
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Finding - Calvert Cliffs - IR 05000317/2011005 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Calvert Cliffs) @ 2011Q4
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