ML20212F564

SER Concluding That All of ampacity-related Concerns Have Been Resolved & Licensee Provided Adequate Technical Basis to Assure That All of Thermo-Lag Fire Barrier Encl Cables Operating within Acceptable Ampacity Limits

ML20212F564
Person / Time
Site:	Grand Gulf
Issue date:	09/23/1999
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20212F557	List: ML20212F552 ML20212F564
References
NUDOCS 9909280263
Download: ML20212F564 (5)

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p" k UNITED STATES 4 j 'j NUCLEAR REGULATORY COMMISSION o,, t  : WASHINGTON, D.C. 20066 4 001 s,;& * .

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION

. GENERIC LETTER 92-08 AMPACITY DERATING ISSUES ENTERGY OPE' RATIONS. INC.

4 GRAND GULF NUCLEAR STATION. UNIT 1 DOCKET NO. 50-416 l

1 1,01 BACKGROUND ' l l

By letter dated December 15,1998, Entergy Operations, Inc. (the licensee), submitted a i response to the third NRC request for additional information (RAI) dated June 19,1998, and a telephone conference meeting held between the staff and licensee representatives on September 24,1998, related to Generic Letter (GL) 92-08, "Thermo-Lag 330-1 Fire Barriers,"

for Grand Gulf Nuclear Station (GGNS), Unit 1.

The determination of ampacity derating factors for Thermo-Lag fire barriers at GGNS is based on a similarity analysis. The licensee provided two engineering reports (GGNS-96-0006 and l GGNS-96-0032) to address ampacity derating issues due to Thermo-Lag fire barriers. The licensee used the results from the TXU Electric Company (TXU Electric) ampacity derating

. tests in its evaluation'(Engineering Reports No. GGNS-96-0006 and No. GGNS-96-0032) of GGNS Thermo-Lag fire barriers with nominal % inch base with or without % inch overlay.

Additionally, the licensee used the results from the Tennessee Valley Authority (TVA) ampacity derating tests in its evaluation (Engineering Report No. GGNS-96-0032) of GGNS Thermo-Lag fire barriers with nominal 1-% inch thick panels and/or pre-formed conduit sections.

The licensee provided submittals dated December 20,1996, and June 5,1997, in response to the . staff RAls dated October 28,1996, and February 26,1997, respectively, which had identified a number of open issues and concerns. The licensee's submittal dated December 15, 1998, contained the response to the latest staff questions regarding its ampacity derating methodology. The staff's evaluation of the ampacity derating methodology for GGNS follows.

2.0 EVALUATION 2.1 Amoacity Deratina Analysis Review The ampacity derating analysis questions, the licensee's responses, and the staff's evaluations l of the responses fellow.

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l QUESTION 1 l

l In response to Question 2 (of the statt's RAI dated February 26,1997), the licensee stated that

" Room OC302 has an average temperature of approximately 80 *F and typically at a temperature of less than 86 *F (30 *C)." The staff would like to know what is meant by average l temperature. Ampacity factor of 1.09 per ICEA standard for ambient temperature of 30 *C is acceptable provided the temperature of the room will never exceed 30 *C. (Note that 40 *C for some length of time and 20 *C for the remaining period will not qualify for an ambient temperature of 30 *C). The licensee is requested to identify,in addition to the historical

) temperature range, what procedures,if any, are applicable for monitoring or controlling temperature in the subject area, 1

Licensee Response l In its submittal dated December 15,1998, the licensee responded as follows:

Peak daily room temperature data was obtained from the Plant Data System for a period of several years for the purpose of developing a worst case temperature profile.

l This temperature profile has been used only in performing the service life evaluation for cables 1 AB561041,1 AB561181, and 1 AB561201. The service life evaluation I

conservatively uses 40 degrees C for the entire 3 month summer period and 30 degrees C for the remaining 9 months of the year. Data obtained from the Plant Data System indicates that while the peak daily temperature for Room OC302 does occasionally exceed 30 degrees C during the summer months, it rarely ever approaches 40 degrees C. Therefore, the service life evaluation is very conservative 1 for the conditions normally experienced by the subject cables, and would even I encompass possible increased temperatures resulting during an unexpected fan outage. Therefore, the licensee will use the standard 40 degree C ambient temperature in OC302 for determining derated cable ampacity. l i' Staff Response The information provided by the licensee fully resolves the staff's concerns.

OUESTION 2 l l

Provide the details of analytical method used to calculate ampacity correction factor (ACF) of 44 percent and a copy of the paper entitled," Fire Endurance and Ampacity Testing of One- and Three Hour Rated Thermo-Lag Electrical Raceway Fire Barrier." Was the paper endorsed by IEEE?

Licensee Response l In its submittal dated December 15,1998, the licensee provided the following response:

l The licensee will use the 48% derating published in Omega Point Laboratories Report No.11960-97333, "Ampacity Derating of Cables Enclosed in a Cable Tray with Thermo-Lag 3301/770-1 Upgrade Electrical Raceway fire Barrier System (ERFBS)"

prepared for TVA and TSI. The 44% ampacity derating correlation established in the I

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paper entitled," Fire Endurance and Ampacity Testing of One- and Three Hour Rated l Thermo-Lag Electrical Raceway Fire Barrier System," authcred by Mark H. Salley and 1 Kent W. Brown, will not be used.- l Staff Resoorge

( The information provided by the licensee fully resolves the staff's concerns.

QUESTION 3 The staff understands that all loads except one load (Emergency Switchgear and Battery Rooms Cooling motor) will have at least 100 percent of rated voltage for all conditions.

Emergency Switchgear and Battery Rooms Cooling motor will have at least 98 percent of rated voltage at its terminals for all conditions. Hence, no adjustment of full load amperes (FLA) for constant KVA loads due to voltage contingencies is required. The licensee is requested to provide comments regarding the variation in voltage, which has been experienced in the past by the subject equipment.

Licensee Response In its submittal dated December 15,1998, the licensee provided the following response:

The licensee has used the minimum anticipated grid voltage (0.992 per unit) in deter. mining the minimum available terminal voltage for the continuous duty constant KVA equipment (Z51 - Control Room HVAC and Z77 - Emergency Switchgear and Battery Rooms Ventilation fan motors) that has power cables contained within Thermo-Lag enclosed raceways. As expected, all of these fan motors would experience less than 100% of rated voltage for the 0.992 pu condition.

A detailed service life evaluation was performed for the three cables of concern. The useful service life for cables 1 AB561041 (O2Z77B001 A Low Speed),1 AB561181 (O2Z77C001 AA Low Speed), and 1 AB561201 (Q1Z77C001 AA Low Speed) has been evaluated using Arrhenius methodology and found to be greater than 40 years under the evaluated conditions.

Measures have been established to ensure that the corrected FLA values for these circuits are not exceeded. These measures require that voltage and current measurements are taken when any activity is performed which could cause the corrected FLA value of the equipment to be exceeded. If the corrected FLA value of the equipment exceeds the derated ampacity limits established, the Engineering Department must be notified so that a detailed review can be performed and the appropriate corrective action initiated, if necessary.

The evaluations performed indicate that no corrective actions are currently necessary.

l The measures that are being established will ensure that if conditions change in such a manner as to affect these evaluations, the Engineering staff will be notified so that appropriate corrective actions can be initiated as necessary.

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4 Staff Response The information provided by the licensee fully resolves the staff's concerns. ,

I QUESTION 4 )

In its response to Question 1 (of the staff's RAI dated February 26,1997), the licensee stated

- an ampacity derating factor of 48 percent due to Thermo-Lag. The licensee also calculated an ampacity derating factor of 44 percent using the analytical method described in response to Question 2 (of the staff's RAI dated February 26,'1997). The licensee is requested to clarify which value is correct. In addition, the licensee is requested to identify which raceways .

enclosed by Thermo-Lag fire barriers would have an insufficient design margin given an ampacity derating factor of 40 percent.

Licensee Response -

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ln its submittal dated December 15,1998, the licensee provided the following response:

The previously used 44% derating did not apply to conduit configurations. Given that the licensee will use only the 48% derating, therefore this clarification is no longer necessary.

SJpff Response The information provided by the licensee fully resolves the staff's concerns.

1 QUESTION 5 (WITHDRAWN) '

' During the telephone conference meeting held with the licensee on September 24,1998, Question 5, which pertained to the grouping factor applied to multiple conduits enclosed by a single Thermo-Lag barrier design, was discussed and clarified to the staff's satisfaction.

2.2 Aoolication of Amoacity Deratina Methodoloav The licensee utilizes' TVA and TXU Electric ' test' data to develop ampacity derating parameters for GGNS Thermo-Lag configurations. The licersee verified that the subject configurations are representative in terms of design and construction of the configurations that were tested by TVA and TXU Electric. , in its submittal dated December 15,1998, the licensee agreed to address future age related cable degradation concerns for the three cables 1 AB561041,

'1 AB561181, and 1 AB561201, which were determined to exceed its design ampacity margin under minimum anticipated voltage conditions (See Question.3). The licensee committed to take voltage and current measurements of the subject cables following any activity that could cause the corrected fullload amperage of the applicable equipment to exceed its analyzed

- limits.-

Given the licensee's response to the~ staff's questions and the licensee's commitment previously described, the staff finds that the licensee has provided adequate information to resolve the ampacity related points of concern raised in Generic Letter 92-08.

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3.0 CONCLUSION

S From the preceding evaluation, the staff concludes that for GGNS, Unit 1, all of the i ampacity-related concerns have been resolved and the licensee has provided an adequate j'

technical basis to assure that all of the Thermo-Lag fire barrier enclosed cables are operating -

within acceptable ampacity limits. Therefore, the staff finds that there are no outstanding safety concerns with respect to the Generic Letter 92-08 ampacity issues.

' Principal Contributor. R. Jenkins Date: September 23, 1999 i

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