ML20246H865

Supplemental Deficiency Rept CP-88-11 Re Battery Charger Overheating.Initially Reported on 880617.Transformance in Two Chargers Replaced.Class IE Battery Chargers Derated to Lower Amperage Rating & Charger Loads Redistributed

ML20246H865
Person / Time
Site:	Comanche Peak
Issue date:	08/28/1989
From:	William Cahill TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CP-88-11, TXX-89550, NUDOCS 8909010393
Download: ML20246H865 (3)

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. Log #.TXX-89550

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Fi1e # 10110 r C 908.3 1EIELECTRIC August 28, 1989 Enacuober M President '

. U. S. Nuclear' Regulatory Commission

. Attn: Document 1 Control Desk Washington, D. C. 20555

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)

. DOCKET NOS. 50-445 AND 50-446 BATTERY CHARGER OVERHEATING SDAR: CP-88-11 (SUPPLEMENTAL REPORT)

Gentlemen:

On June 17, 1988, the'NRC was informed via a final report logged TXXL88490 of a deficiency involving battery charger overheating. It wascreported in TXX-88490 that the deficiency was not generic.to all of the chargers and did not. meet the criteria for deportability pursuant to 20CFR50.55(e) or 20CFR21.

After further testing and evaluation, it has been concluded.that this deficiency does meet the criteria for deportability pursuant to 10CFR50.55(e).

The required information follows.

DISCUSSION. ,

As discussed in previous correspondence, the concerns related to potential

-overheating of.the eight safety related battery chargers in Unit I were originally: identified during preoperational_ testing. Based on additional testing conducted at CPSES on three of the eight battery' chargers, it was

. concluded that the deficiency was not a generic concern but was related to a defective transformer coil (T1-B coil) in one charger. The results of this testing were discussed in'TXX-88490. It was also indicated that investigation with the charger vendor was continuing in an effort to identify the problem associated with this single coil. This effort led to the performance of additional site testing and testing at the vendor's facility. Overheating of

, charger transformers was experienced during this testing and, based on this testing, it was concluded that the battery chargers had a generic problem with operational temperatures in excess of the qualified limits when loaded near the full power rating of the equipment or operated in the current limit mode.

On December 27, 1988, Power Conversion Products notified TU Electric and the NRC of this information pursuant to 10CFR21.

890901039? 890828 PDR ADOCK 05000445 a S PDC

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400 North Olive Street LB lt! Dallas. Trans 75201

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TXX-89550 August 28, 1989 Page 2 of 3 Subsequent to this notification, TU Electric has pursued resolution of this deficiency as it applies to CPSES.. Due to the design margins existing at _

Cr$ES, this issue was resolved by evenly distributing connected loads and derating the chargers in accordance with vendor instruction to a lower amperage rating for full load and. current limit operation while still meeting design and regulatory requirements.

Site testing performed subsequent to the charger modifications identified operational problems with the chargers in the " current limit" mode. TU Electric considers this to be an additional example of the inadequate. vendor design that is the cause of this deficiency.

SAFETY IMPLICATIONS Each battery charger is sized to recharge the battery from the design minimum charge state to the fully charged state within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> while supplying the steady. state. loads under all modes of plant operation. A common mode failure mechanism' associated with charger overheating may have resulted.in multiple charger failures and the inability to meet the design objectives. Therefore, this issue represents a significant final design deficiency as approved and released for construction and, were it to have remained uncorrected, could have adversely affected the safety of plant operations.

CORRECTIVE ACTIONS The following corrective actions have been or will be performed to resolve this deficiency:

1. The transformers in two chargers that experienced overheating during testing were replaced as a conservative measure.

E. The Class IE battery chargers have been derated to a lower amperage rating for full load and current limit operation that maintains the charger transformers within the qualification temperature limits.

3. Modifications will be made to the charger current limit and sensing board in order for the chargers to be operable at the revised current limit rating.

4. An equipment qualification analysis has been performed to consider the impact of the operational temperatures resulting from the overheating. This analysis has demonstrated a qualifed life in excess of 40 years.

5. Charger loads have been redistributed and are now consistent with the derated capacity.

The above mentioned corrective actions will be completed prior to Unit I fuel load for Unit I and prior to Uriit 2 fuel load for Unit 2.

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. d TXX-89550 August 28, 1989 Page 3 of 3 This action is technically justified because evaluations considering the operating history to date have been performed which demonstrate that the 40 year qualified life of the derated chargers has not been compromised. Records of this information are available for your review.

Sincarely.

/ , .'

William J. hill. Jr.

WJH/vid c - Mr. R. D. Martin, Region IV Resident Inspectors. CPSES (3) l l l i

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