ML19274E513

Forwards Responses to Questions 3 & 10 of 790119 Request for Addl Info

ML19274E513
Person / Time
Site:	Sequoyah
Issue date:	03/23/1979
From:	Gilleland J TENNESSEE VALLEY AUTHORITY
To:	Varga S Office of Nuclear Reactor Regulation
References
NUDOCS 7903290158
Download: ML19274E513 (4)

Text

TENNESSEE VALLEY AUTHORITY CH ATTANOOGA. TEN N ESSEE 37401 500C Chestnut Street Tower 11 MAR 2 31979 Director of Nuclear Reactor Regulation Attention: Mr. S. A. Varga, Chief Light Water Reactors Branch No. 4 Division of Project Management U.S. Nuclear Regulatory Commission Washington, DC 20555

Dear Mr. Varga:

In the Fbtter of the Application of ) Docket Nos. 50-327 Tennessee Valley Authority ) 50-328 Enclosed are TVA's responses to questions 3 and 10 of your January 19, 1979, request for additional information. These responses will be incorporated into the Sequoyah Nuclear Plant Final Safety Analysis Report by Amendment 61 as questions Q6.53B and Ql7.78, respectively.

This completes the TVA response to your January 19 letter.

Very truly yours, 03 O/h>p J. E. Gilleland

'f Assistant Manager of Power Enclosure (10)

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7903290 /6 9 h An Equal Opportunity Employer

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e fk 3.(RSB) Bypasses SIS Q6.53B The applicant's response to staff question 212.104 concerning an RllR line break with SIS bypassed did not supply sufficient information for the staff to complete its review. The applicant indicated that the safety injection signal could be unlocked in two seconds in order to mitigate an RllR line break. However, the applicant's cubmittal on water solid overpressure protection included locking out power to most of the emergency core cooling system when on the RilR system. Provide a list of equipment needed to mitigate an RllR line break to ensure core coverage when on the RiiR system. Describe the required operator actions which may be credited 10 minutes after the first alarm warning the operator of the line break and justify the time required to initiate equipment operation and perform the indicated tasks.

Justify your break size and location.

Response

As discussed in the response to question 6.53, the occurrence of a break in the MllR line during a normal shutdown or heatup when in the RiiR mode of operation is considered highly unlikely. For example, the RCS pressure in that mode would be 425 PSIG compared to an HER piping design pressure ppg of 600 PSIG. Ilowever, such a postulated event has been addressed and discussed below.

An analysis has been performed for a postulated RiiR moderate energy line break during shutdown. An assessment was also made to determine the equip-ment necessary to mitigate an RllR line break to ensure core coverage.

The analysis has shown that the operator has 58 minutes after the initial alarm to take appropriate action to ensure core coverage.

The analysis further establishes that (i) one centrifugal charging pump or one SI pump will provide adequate flow to sustain the system in a safe condition and (ii) an alarm signal (low pressurizer level deviation alarm - zero power programmed level) would be sounded within 30 seconds of the event initiation. The analysis conservatively addressed the largest RilR line which could adversely impact both RllR pumps simultaneously.

The break area was developed consistent with moderate energy line break criteria and was established to be 0.01 ft2 Results of the analysis confirm that the required pump flow could be provided by a single operator action (assuming no failure of the operating centrifugal charging pump). The single operator action would be manual SI initiation f rom within the control room. -

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b Additional conservatisms applied to the above analysis would be excessive.

(~5 liowever, even if (1) a 10-minute delay time for operator action and (ii)

("N a single failure assumption were assumed, they would not result in an unsafe condition. Specifically, 48 minutes would still remain available for initiation and effective operation of necessary safety grade eguipment.

Moreover, only under the assumption of a single failure of the operating centrifugal charging pump are cperator actions involving leaving the main control room required. For this postulated condition, it would be necessary to unlock the breaker for either of the two safety injection pumps or for the remaining centrifugal charging pump in order to place a safety grade pump into operation. These breakers are located on the 6.9-kV shutdown boards immediately outside the main control room at elevation 734.

In conclusion, response 6.53 has already established the conservatism of addressing the postulated scenario. An assessment of such a scenario f t:rther confirms the ample margins available in retaining the core in a safe condition.

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10.(QA) We have concluded that Reculatory Guide 1.68.2, " Initial Startup Test (17.76) Procran to Demonstrate Remote Shutdown Capability for Water Cooled Iluelcar Power Plants" (Revision 1 3July 197d) and Regulatory Guide 1.103, " Periodic Testing of Diesel Generator Units Used as Onsite Electric Ibwer Systems at Iluelcar Power Plants" (Revision 1, August 1377) are applicable for your facility. Modify your FSAR to describe how your initial test pro;ran will conform to Regulatory Guide 1.u8.2 and Regulatory Positions C.2.a and C.2.b of Reculatory Guide 1.103 or describe how you will provide for equivalent alternative testing.

Recr>onse

'Ihrcuch preoperation, startup, and surveillance testing, Sequoyah Ihiclear Plant will fully comply with Regulatory Guide 1.68.2 (Revision 1) and Regulatory Guide 1.103, Positions C.2.a and C.2.b (Revision 1).

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