TXX-4385, Responds to 841106 Request for Addl Info Re Safe Shutdown & Alternate Safe Shutdown Design of Facilities.Util Will Complete Associated Circuit Analysis & Rept Prior to Exceeding 5% Power

Responds to 841106 Request for Addl Info Re Safe Shutdown & Alternate Safe Shutdown Design of Facilities.Util Will Complete Associated Circuit Analysis & Rept Prior to Exceeding 5% Power

ML20101F748
Person / Time
Site:	Comanche Peak
Issue date:	12/20/1984
From:	Beck J TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:	Youngblood B Office of Nuclear Reactor Regulation
References
TXX-4385, NUDOCS 8412270289
Download: ML20101F748 (9)

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TEXAS UTILITIES GENERATING COMPANY Log # TXX-4385 NKYWAY TOWER . 400 NORTH OLIVE NTHEET, L.H. 81 e DALLAN.TEXAM TS208 FiIe # 10010 907.4 JOHN W. SECK .

December 20, 1984 Director of Nuclear Reactor Regulation Attention: Mr. B. J. 'Youngblood, Chief

Licensing Branch No. 1 Division of Licensing U. S.. Nuclear Regulatory Commission -j Washington, D.C. 20555 i

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SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION DOCKET NOS. 50-445 AND 50-446 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION- i ON SAFE SHUTDOWN AND ALTERNATE SAFE SHUTDOWN REF: (1)-B. J. Youngblood to M. D. Spence letter of  !

November 6,1984 entitled " Request for l Additional Information Pertaining to the Safe Shutdown and Alternate Safe Shutdown Design of Comanche Peak Steam Electric Station (Units 1 and 2)"

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Dear Sir:

Reference (1) provided six requests for additional information.

The responses to these questions are attached. Please note that copies of the Comanche Peak Steam Electric. Station Fire Protection Program Review Task report are being submitted (under separate cover) in support of these responses.

Respectfully, f_&/

v John W. Beck DRW:tls Attachment Distribution: Original + 40

/Ob 0412270289 841220 PDR ADOCK 05000445 9

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(i A Dit' INION OF TEXAN E71LITIEN ELECTRIC COMPANY

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F CP SES/FSAR Q010.26 The analysis of associated circuits as they relate to safe shutdown' systems and high'-to-low pressure interfaces in incomplete. The applicant has committed to complete the associated circuit analysis -

prior to exceeding 5% power. To conplete this review we. need the following information.

a. identification of high-to-low pressure interfaces, 4

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b. verification that each redundant valve's power and control cabling are properly separated.

R010.26 Texas Utilities will complete the associated circuit analysis and will report this completion prior to exceeding 5% power.

a. The high-to-low pressure interfaces are listed below:

1. RHR/RCS Boundary Isolation Yalves

2. Pressurizer Power-0perated Relief Yalves

3. Normal Letdown Isolation Valves

. 4. Excess Letdown Isolation Yalves

5. Reactor Head and Pressurizer Vent Valves

b. The CPSES design _ protects against a high-to-low pressure failure at these interfaces as described in the CPSES Fire Protection Program Review Report. A tabular summary is provided in

. Table 3-3.1 of that report.

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CPSES/FSAR '

. Q010.27 The applicant has not verified that protective

devices, that are ' relied upon to prevent fires in associated circuits from affecting safety related equipment, are located outside of the fire zone containing the affected associated circuits.

t R010.27- ' Associated circuits can develop an electrical fault

.due to a fire. If the fire is not in the same fire area as the protective device for that circuit, the protective device will clear the fault to prevent the circuit from generating new fires in other locations.

The fire will not propogate along the wire due to the fire resistant characteristics of the wire and the use of fire stops.

If the fire develops in the same area as the protective device for an associated circuit, the fire safe shutdown analysis does not take credit for that protective device to clear an electrical fault. The

, analysis assumes that the -next upstream protective

device (not in that fire area) will clear the fault.

The only area of concern is that portion of the circuit between the fault and the protective device and that portion of the circuit is already in the affected fire area. The fire will not propagate along the cable to other fire areas for the same reasons mentioned above. For the credible fire

, scenarios that we have defined, a fire in a fire area that contains an associated cable and its protective

. device will not jeopardize the integrity of the cables required for safe shutdown.

4 In evaluating associated circuits powered from a coianon power supply, multiple high resistance grounds

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_j CPSES/FSAR could be' postulated on. several different associated circuits.with the same power supply such that the protective devices for the associated circuits would not trip but the protective device for the common power supply would trip. This situation was considered but the-probabilities of getting the needed high . resistance grounds on .the proper associated circuits simultaneously .was considered too low to merit additional consideration.

CPSES/FSAR Q010.28 The' applicant has not confirmed that acceptable coordination and selective tripping is provided for safe shutdown circuits on the ac and de power systems.

R010.28 In order to ensure that associated circuits that share a common power supply with safe shutdown

. circuits do not trip the coianon power supply during a fire, the protective device for the associated circuit must be set to trip before the protective device for the common power supply. -This is commonly referred to as breaker / fuse coordination and selective tripping. Proper coordination is usually assured by verifying that the protective device for the. branch circuit has a lower instantaneous trip setting than the protective device for the cosanon power supply or verifying that the time current curve for the branch circuit protective device will actuate

, before the time current curve for the common power supply protective device for the anticipated range of fault currents of concern.

The design criteria for the protective devices at CPSES included requirements to ensure proper breaker / fuse coordination and selective tripping. A small audit was conducted to confirm this portion of the design. Although no confirmed problems were uncovered by this audit, the audit did reveal that many setpoints for protective devices are variable and that verification that the branch protective ,

device will trip first is not always an easy task.

To provide better assurance that our design is adequate, TUGC0 plans to evaluate these audit results 010-58

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CPSES/FSAR l

more closely. If necessary, additional circuits will

- be examined. If any doubts are raised, a 100%

confirmation of the protective devices of concern will be performed.

This confirmation effort is a complex task that could take a significant period of time. In the interim, however, the high confidence established by our design requirements and the high level of compliance by CPSES in the overall fire protection area, justifies CFSES operation until the confinnation effort is completed. TUGC0 can commit that this confirmation effort will be completed prior to startup for the second operating cycle.

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CPSES/FSAR

-Q010.29 The applicant has comitted to ensure 'that electrically induced secondary fires in comon ent.losures will not occur by reviewing a sufficient number of cables that share a common enclosure with safe shutdown equipment. The purpose of this review is to confirm that the design provides adequate

. electrical protection. We require the applicant to demonstrate that the design provides adequate electrical protection by reviewing all cables that share a common enclosure with safe shutdown equipment.

R010.29 The design at CPSES provides adequate electrical protection for all power circuits. The protective devices were selected to meet the requirements of the National Electrical Code. The confirmatory audit was done as part of our overall fire protection review to provide additional confidence that the design requirements were properly met. The CPSES design provides adequate electrical protection for all cables that share common enclosures.

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CPSES/FSAR QC10.30 The applicant has not verified that all plant design I changes ~ are incorporated into the fire safe shutdown analysis. The applicant has committed to this verification prior to exceeding 5% power.

Q010.'30 Texas Utilities will. coglete verf fication' that all plant design changes are incorporated into the fire safe shutdown analysis and will report the cogletion of this verification effort prior to exceeding 5%

power.

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CP SES/FSAR

.Q010.31 The applicant has not confirmed that their design has the capability to achieve and mintain hot shutdown condition without repairs to the safe shutdown systems.

R010.31 The design of CPSES includes the capability to achieve and mintain a hot shutdown condition without repairs to the safe shutdown systems.

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