05000254/FIN-2011009-05
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Finding | |
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| Title | Diesel Generator Technical Specification Frequency and Voltage Variation not Considered in Loading Calculations |
| Description | While reviewing actions in response to NRC Information Notice (IN) 2008- 002, the inspectors noted the licensee staff had evaluated the effects of lower than nominal frequency on pump flows and pressures and determined there were no adverse effects on pump flow and pressures and the upper frequency limit did not cause the EDG loading to exceed the 200 hour0.00231 days <br />0.0556 hours <br />3.306878e-4 weeks <br />7.61e-5 months <br /> per year rating. The inspectors found that the current calculation (QDC-6700-E-1500, Rev 005A) determined diesel loading based on maximum loads during a design basis accident. The loading was based on nominal 60 hertz (Hz) operation of pumps and fans, and did not account for the +2 percent variations allowed by TS 3.8.1.2. Mechanical affinity laws show power demanded by centrifugal pumps and fans increases by the cube of the ratio of the speeds (1.02 cubed = 1.061). Since the EDG accident loading was comprised primarily of centrifugal loads, the inspectors determined this phenomenon should have been considered in loading calculations. In CR 591442, Effect of EDG Frequency on Loading and Pump Flows, dated February 14, 2007, the licensee had noted this increase in loading and had determined that it was still within the 200 hr per year rating (2973 kW) for the EDGs. The evaluation of decreased frequency loading showed all pumps developed adequate pressure and flow. The inspectors were concerned the maximum loading exceeded the 2000 hr rating of 2864 kW. The inspectors consulted with the Office of Nuclear Reactor Regulations (NRR) and were informed the loading should be compared to the licensed value for the EDGs. Additionally, the licensee should have demonstrated there were no detrimental effects on all systems, structures, and components (SSCs) over the full range of frequency and voltage allowed by TS. Specifically, the torque developed by a motor is directly proportional to the square of the voltage and inversely proportional to the square of the frequency. The inspectors compared the TS limits to the nominal values for voltage and frequency and determined that torque developed by the motors supplied by the EDGs could vary as much as 14 percent from the nominal torque. The inspectors informed the licensee of their concerns about the operability of the supplied motors being able to meet the design requirements, particularly for pumps and motoroperated valves under the worst torque conditions (minimum voltage and maximum frequency) and EDG loading for the best conditions. Additionally, the inspectors noted the UFSAR loading limit was the 2000 hr rating. The inspectors asked for any licensing document that could support using the 200 hr load limit. In response to the inspectors questions, the issue was entered into the licensees corrective action program as AR 01288784, CDBI Technical Specification Limits for EDG, dated November 10, 2011. A review of operating procedures provided reasonable assurance that the EDGs would be operated near the midpoint of the allowed TS range during a potential event until the licensee demonstrates operability over the full TS range. This will be an unresolved issue pending the results of the licensees evaluation of the effects of the full TS voltage and frequency ranges on all SSCs and verifying the licensed load limit for the EDGs. |
| Site: | Quad Cities  |
|---|---|
| Report | IR 05000254/2011009 Section 1R21 |
| Date counted | Dec 31, 2011 (2011Q4) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | Z Falevits S Sheldon W Sherbin D Melendez-Colon C Brown N Feliz-Adomo A Stone J Chiloyenb Palagid Passehl J Laughlin J Mcghee B Cushman J Draper C Mathews R Elliott R Orlikowski M Mitchell C Brown |
| INPO aspect | |
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Finding - Quad Cities - IR 05000254/2011009 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Quad Cities) @ 2011Q4
Self-Identified List (Quad Cities)
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