05000341/FIN-2007003-05
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Finding | |
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| Title | INRUSH CURRENT OF SPRING CHARGING MOTORS NOT CONSIDERED (Section 1R21.3.b.5) |
| Description | The inspectors identified an unresolved item concerning calculation DC-0213, Sizing of 130/260V Batteries, for not considering the inrush current of the spring charging motors associated with closing mechanism of 4160V and 480V switchgear circuit breakers. The licensee recognized this condition in 2003 and issued a CARD to incorporate the inrush current of spring charging motors into the calculation and re-evaluate the batterys 1 minute rating. However, four years later the licensee has failed to revise the calculation. At the end of the inspection, the licensee was still evaluating the impact of the inrush current on the batterys 1 minute rating and had not completed their final assessment. The inspectors needed this information to complete the assessment of this issue. Description: During a review of battery sizing calculation DC-0213, the inspectors identified that the calculation used average current values instead of inrush current values of spring charging motors associated with closing mechanism of 4160V and 480V switchgear circuit breakers. Per IEEE Standard 485-1997, IEEE Recommended Practice for Sizing Lead-Acid Batteries for Stationary Applications, momentary loads such as the switchgear operations and inrush currents should be used when determining batterys 1 minute rating. Momentary loads could occur one or more times during the duty cycle, but would be of short duration, not exceeding 1 minute at any occurrence. Although momentary loads may exist for only a fraction of a second, it was common industry practice to consider that each load would last for a full minute because the battery voltage drop after several seconds often determined the batterys 1 minute rating. Sizing for a load lasting only a fraction of a second, based on the batterys 1 minute performance rating, would result in a conservatively sized battery. When several momentary loads occur within the same 1 minute period and a discrete sequence cannot be established, the load for the 1 minute should be assumed to be the sum of all momentary loads occurring within that minute. During the minute, depending on how many momentary loads occur, the inrush current pulls the battery voltage down and therefore it would be necessary to ensure that the battery was adequately sized to provide the required voltage to the loads. Because of the failure to consider the inrush 15 Enclosure current in sizing the batteries, the inspectors were concerned that the batteries might not have been adequately sized to provide the required voltage to the loads. The licensee recognized this condition in 2003 and entered this issue into their corrective action program, CARD 03-16683, which called for revising the calculation based on inrush current of the spring charging motors. This CARD was assigned a low priority level of four and closed out to Technical Service Request 34807. As a result, four years later, this calculation had not been revised. The licensee tested three spring charging motors to determine their inrush currents because the information was not available. Out of the three motors tested, one motor registered twice the inrush current of the other two. The licensee had the breaker manufacturer (Asea Brown-Bovari) conduct tests on Ametek charging motors in Kline 800 amp breakers. At the end of the inspection, the licensee had not finished their assessment, but took some temporary compensatory measures to reduce load on the batteries as part of operability determination, EFA R32-07-002. The compensatory measures consisted of turning off power to the spring charging motors associated with breakers feeding non-safety-related loads. However, the inspectors noted that the licensee did not follow the 10 CFR 50.59 process for implementing compensatory measures as required. The licensee performed 10 CFR 50.59 screening 07-0162 that concluded a safety evaluation was not required. The inspectors review of the licensees operability determination and 10 CFR 50.59 screening did not identify any concerns with their conclusions. Since the licensee had not finished their assessment and had not validated the battery sizing calculation based on incorporating the inrush current of the spring charging motors, the NRC concluded that additional review and evaluation were required to assess whether or not the batteries were adequately sized for the application. Therefore, this issue is considered an unresolved item (URI 05000341/2007003-05) pending the licensee completion of an analysis to assess the battery sizing and subsequent NRC review. |
| Site: | Fermi  |
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| Report | IR 05000341/2007003 Section 1R21 |
| Date counted | Sep 30, 2007 (2007Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | T Steadham D Reeser M Bielby M Franke R Morris A Wilson R Lerch K Barclay A Muniz C Lipa J Moore K Streit M Holmberg M Munir R Jickling J Cassidya Dunlopm Munir B Palagi D Passehl M Shlyamberg F Baxter C Acosta Aceved |
| INPO aspect | |
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Finding - Fermi - IR 05000341/2007003 | |||||||||||||||||||||||||
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Finding List (Fermi) @ 2007Q3
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