ML20147H491

Responds to 781205 NRC Ltr Requesting Addl Info Immediately to Q212.74 & Q221.387 Re Transient Analysis & Feedwater Sys. Advises NRC That ASME Code Case N-196 Is Being Applied to This Dkt

ML20147H491
Person / Time
Site:	Zimmer
Issue date:	12/22/1978
From:	Borgmann E CINCINNATI GAS & ELECTRIC CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
NUDOCS 7812270305
Download: ML20147H491 (3)

Text

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q . 1 pw 3 p myg f jk!kif$h TIIE CINCINNATI GAS & ELECTRIC COMPANY 55 EEEE CINCIN N ATI OHIO 4 S201 C. A. 50 AQ M AN N vie t pet siotw a=w.stewJ Docket No. 50-358 December 22, 1979 l- Mr. Harold Centon, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Ccmmission Washington, D.C. 20555 l

PE: WM. H. ZIMMER NUCLEAR POWER STATION - UNIT 1 i RESPONSE TO STAFF QUESTIONS 212.74 AND 221.387, Ay9 ASME CODE CASE N-196 Dear Mr. Denten By letter of December 5,' 1978, Mr. John Stol:: transmitted a request for additional information. The requested information was in the form of  ;

questiens/ positions in the 110, 121, 212, and 221 categories. Revision 51 to the FSAR, scheduled to be filed on January 2,1979, will centain the App 1Mant's response to all of these . questions / positions.

The Staff has expressed an interest in being advised promptly of the responses to Q212.74 and Q221.387. In order to accom:.odate the Staff, Attachment 1 of this letter contains the responses to these two questions.

They will m further documented in Revision 51 to the FSAR.

The NRC is advised that ASME Code Case N-196 is being api' in this docket. Revision 51 of the FSAR will also reflect thir Very truly yours, THE CINCINNATI GAS & ELECTR.~'

E. A. BORGMANN Vice President - Engin'Ars.

EAB: dew and Electric Productiot' c Enclosure cc: Charles Bochhoefer State cf Chio

)

Glenn O. 3right County of Hamilton)**

Frank F. Hooper Troy B. Conner, Jr. Swcrn te and subscribed before me this James P. Fenstermaker J2 /d day of December, 1978.

Petr H..Forster M.liiam J. Moran b J. Robert Newlin William G. Fortor, Jr. hw James D. Flynn {lotaryP'iblic Thomas A. Luebbers MARGARET . HUBER Stephen Schumacher _ Nctary rubne. state or onio l John D.'Woliver My Commission Expires Aug. 13,1983

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0212.74-In' analyzing anticipated operational transients, the applicant has taken credit for plant operating equipment which has not i been shown to be reliable as required by General Design Criterion 29. The staff has discussed the application of this 1

equipment generically with Ganeral-Electric. Based on these discussions, it is the staff's understanding that the most limiting transient that takes credit for this equipment is I the excess feedwater event. Further, it is the staff's under- I standing that the only plant operating equipment that plays l a significant role in mitigating this event is the turbine' i

bypass system and the Level 8 high water level trip (closes turbine stop valves).

! In order to assure an acceptable level of p.erformance, it is the staff's position that this equipment be identified in the

, plant Technical Specifications with regard to availability,

i. set points, and surv 111ance testing. The applicant must submit his plan for implementing this requirement along with any system modifications that may be required to fulfill the requirements.

Response

In discussions between GE and the NRC on November 20 and 21, 1978, GE reported on the results of transient analysis when performed to design basis accident conditions assumptions, and equipment 4

availabilities, that failure to give credit to the L8 Turbine Trip and the Main Turbine Bypass system could respectively result in diCPR's of 0.02 and'O.08. In no manner could these postulated accident events result in unacceptable impacts on the health and safety of the public as GDC criteria #29 requires.

L8 Tech spec The L8 instrumentation is already subject to technical spec-ifications requirements associated with the HPCS. If the NRC should require such a trip tech spec, such a requirement can be accommodated by the present design.

Main Turbine Bypass System Tech Spec The turbine bypass system and stop valves are furnished with the main turbine generator by Westinghouse and have exhibited high reliability on existing nuclear and fossil fueled oper-ation units.

Normal CG&E operating procedures require that the valves be functionally exercised daily. This will ensure valve operability and provide adequate. assurance that the valves will operate when required.

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0221.387 It is the staff's position that the Zimmer FSAR is not sufficiently complete so as to demonstrate that feedwater system level sensors N004A, N004B, and N004C are electrically isolated from each other. Therefore, the staff requires that you 4

(1) Revise the FSAR, Section 7.7 to clearly describe the design and qualification of the circuitry and equipment which is common to two or more of the level 8 sensor / alarm trip unit channels l utilized in the feedwater control system. This revision should contain sufficient information and drawings to permit the staff

, to review the feedwater control system as specified in Section 7.7 of the Standard Review Plan.

(2) Demonstrate by using the material which is provided in the responce to (1) above, that the N004A, N004B and N004C signal paths are independent.

i (3) Justify not removing the plant process computer inputs A1723 and A1727 from the feeduater control system.

Response

In discussions between GE and the NRC Reactor Systems and C&I Branches on November 20 and 21, 1978, the failure of the reactor feedwater level sensing subsystem was shown to have resulted in no dkCPh effects on the four leading limiting transients. The failure of the L8 instrumentation, including computer would result in a negligible ZiCPR effect (0.02). Therefore, it would seem inappropriate to further explore the failure aspects of this subsystem since even given their failure, they do not result in any effect on the previously described (FSAR) transient analysis.

An adequate description of the feedwater control system is con-tained in Section 7.7.1.3 and figure 7.7-8.

A failure of the computer inputs, as discussed above, would have a negligible effect on ZiCPR.

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