ML20206N305

Submits RAI Re Replacement of Nuclear Instrument Sys Source & Intermediate Range Channels & post-accident Neutron Flux Monitoring Sys

ML20206N305
Person / Time
Site:	Vogtle
Issue date:	12/08/1998
From:	Beasley J SOUTHERN NUCLEAR OPERATING CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20206N309	List: ML20206N305 ML20206N313
References
LCV-1242-A, NUDOCS 9812160235
Download: ML20206N305 (6)

Text

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s- .. a J. Bernie Reasley, Jr., P.E. ' Southern Nuclear V;ce President Operating Company,Inc.

Vogtle Project 40 invemess Center Parkway PO Box 1295 Birmingham. Alabama 35201 Tel 205.992.7110

. Fax 205 992.0403 SOUTHERN COMPANY December 8,1998 Energy to Serve hur %rld*

LCV-1242-A Docket Nos. 50-424 and 50-425 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 Ladies and Gentlemen:

VOGTLE ELECTRIC GENERATING PLANT REQUEST TO REVISE TECHNICAL SPECIFICATIONS REPLACEMENT OF NUCLEAR INSTRUMENTATION SYSTEM SOURCE AND INTERMEDIATE RANGE CHANNELS AND POST-ACCIDENT NEUTRON FLUX 4 MONITORING SYSTEM REOUEST FOR ADDITIONAL INFORM ATION By way ofletter LCV-1242 dated September 3,1998, Southern Nuclear Operating Company (SNC) requested to amend the Vogtle Electric Generating Plant (VEGP)

Technical Speci6 cations, Appendix A to Operating Licenses NPF-68 and NPF-81. The revision to the Technical SpeciGcations is to support the replacement of the Westinghouse Nuclear Instrumentation System Source Range and Intermediate Range Channels and the Post-Accident Neutron Flux Monitoring System with an equivalent monitoring system supplied by Gamma-Metrics.

In response to discussions with the Staff, this letter contains additional information as clari0 cation to the original amendment request in letter LCV-1242 referenced above.

In addition to the additional information, this letter also contains two additional Technical Specincation Bases changes that were identined subsequent to the original amendment {

request in letter LCV-1242 referenced above. Reactor Trip System (RTS) \

Instrumentation Bases page B 3.3-60 is being revised to include this amendment in the list of references (Reference 6 on page B 3.3-60). High Flux at Shutdown Alarm (HFASA) Instrumentation Bases page B 3.3-172 is being revised to remove reference to the Source Range instrumentation being deenergized. This same change was made to Bases pages B 3.3-14, B 3.3-29, and B 3.3-33 in the criginal amendment request in o\

letter LCV-1242. ,r- g0 O The above-described proposed Bases changes do not alter the conclusion that the amendment request does not involve any signi0 cant hazards consideration as described in the original amendment request in letter LCV-1242.

9812160235 98120e 3 PDR ADOCK 05000424 P PDR

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L U. S. Nuclear Regulatory Commission Page 2 Mr. J. B. Beasley, Jr. states that he is a Vice President of Southern Nuclear Operating Company (Southern Nuclear) and is authorized to execute this oath on behalf of Southern Nuclear and that, to the best of his knowledge and belief, the facts set forth in this letter and enclosures are true.

SOUTHERN NUCLEAR OPERATING COMPANY By: /

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"J. BlBea%y, Jr.

Sworn to and subscribed before me this - day of /h ,1998.

b) C. /

Notary Public gymg My Commission Expires:

Enclosures-1

1. Response to RAI

2. Marked-Up Revisions to Bases Pages

3. Typed Revised Bases Pages xc: Southern Nuclear Operating Company Mr. J. T. Gasser Mr. M. Sheibani SNC Document Management U. S. Nuclear Regulatory Commission Mr. L. A. Reyes, Regional Administrator Mr. D. H. Jaffe, Senior Project Manager, NRR ,

Mr. J. Zeiler, Senior Resident luspector, Vogtle l 1

State of Georgia Mr. L. C. Barrett, Commissioner, Department of Natural Resources LCV-1242-A t

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4 ENCLOSURE 1 RESPONSE TO RAI Y

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Ouestion 1 Was the methodology used for the design change calculations to verify the correct correlation between the source range (SR) neutron flux trip and the P-6 permissive  ;

setpoints for the new Gamma-Metrics instrumentation previously approved by the NRC7 l If yes, please provide date of approval. Otherwise, provide calculations for review. l l

Resnonse to Ouestion 1 The methodology used for the design change calculations which verify the correct correlation between the Source Range (SR) neutron flux trip and the P-6 permissive setpoints is similar to that used by Sequoyah Nuclear Plant for Amendments No.136 (Unit 1) and 185/177 (Unit 1/2), dated April 27,1990 and July 26,1994 respectively. The

Sequoyah Technical Specification changes were associated with the replacement of the l Westinghouse SR and Intermediate Range (IR) detectors with Gamma-Metric detectors, similar to the proposed Vogtle Electric Generating Plant (VEGP) design change.

A further description of the derivation of the setpoints and allowable values for VEGP is provided in the response to Question 3.

Ouestion 2 Will the different method of applying the uncertainty value to the logarithmic instrumentation be included in the current setpoint methodology?

l Resoonse to Ouestion 2 '

The setpoint methodology used by Vogtle is based on Westinghouse WCAP-11269, I which is referenced in Technical Specification Bases B 3.3.1. The derivation of the components of the setpoint calculations account for the logarithmic instrumentation, however, the methodology for statistically combining the components is the same as that described in WCAP -11269. The affected calculations have been revised and will be maintained by Southern Company.

Ouestion 3 List any setpoints that are being changed or state if the setpoint and allowable values are ,

equivalent conversions. Were any allowable values obtained by interpolation? Are the equivalent values typical of four loop Westinghouse plant data?

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,. 1 Response to Ouestion 3 Listed below is a table showing the "WAS" and "IS" values which correspond to before and after the design and Technical Specification changes.

WAS Table 3.3.1-1 ,

Function Allowable Value Trip Setpoint

4. Intermediate Range s 31.1% RTP 25 % RTP

• Neutron Flux

5. Source Range s 1.4 E5 cps 1.0 E5 cps Neutron Flux

16. Intermediate Range 2 6E -11 amp IE -10 amp Neutron Flux, P-6

• (Current Equivalent)-

1E Table 3.3.1-1 Function Allowable Value Trip Setpoint

4. Intermediate Range s 41.9 % RTP*

• 25 % RTP (No Change) ,

Neutron Flux (Changed)

5. Source Range 1.0 E5 cps (No Change) s 1.7 E5 cps **

Neutron Flux (Changed)

16. Intermediate Range 2.0 E -5 % RTP 21.2 E -5 % RTP*

• Neutron Flux, P-6 (Changed) (Equivalent Conversion)

" Derived value based on setpoint calculation.

As shown in the table above, the P-6 value is the only setpoint that is changing. This

. value is an equivalent conversion based on the approximate linear relationship between the Intermediate Range (IR) current and reactor power. This relationship between the Intermediat'e Range current and reactor power has been verified through review of several cycles of plant data from both VEGP units. The P-6 setpoint value was determined by linear extrapolation of the Intermediate Range current versus power to obtain the power equivalent of the P-6 setpoint.

1 L The allowable values were derived based on the rack uncertainty values for the new Gamma- Metrics instrumentation.. The methodology of statistically combining the uncertainty terms has not changed. However, instead of applying the rack uncertainty

l. . values to a linear scale, as is presently done in the Westinghouse setpoint methodology,

.the uncertainty values are applied to a logarithmic scale. This is a more appropriate

' method since the instrumentation is operating in the logarithmic mode.

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. As referenced in the Technical Specification amendment request (letter LCV-1242, l September 3,- 1998), the SR, IR, and P-6 setpoints are consistent with Westinghouse l functional requirements for nuclear startup protection. The functional requirements specify a range of settings for the SR, IR, and P-6 setpoints, which are as follows: ,

SR high neutron flux trip: =10 to =10 % of full power, IR high neutron flux trip: 5 to 30 % of full power, .

P-6: =10 to =10-3 % of full power.

Additionally, a comparison of the proposed VEGP SR,IR, and P-6 setpoints against those of Sequoyah and Watts Bar Nuclear Plants, which are Westinghouse four loop i plants, indicates the values are comparable.

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