ML17311A211

Forwards Response to Questions Re TS Amend for Figure 3.2-1

ML17311A211
Person / Time
Site:	Palo Verde
Issue date:	08/11/1994
From:	Stewart W ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
102-03080-WLS-R, 102-3080-WLS-R, NUDOCS 9408230242
Download: ML17311A211 (10)

Text

p REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR: 9408230242 DOC. DATE: 94/08/11 NOTARIZED:

NO DOCKET FACIL:STN-50-529 Palo Verde Nuclear Station, Unit 2, Arizona Publi 05000529 AUTH.NAME AUTHOR AFFILIATXON STEWART,W.L.

Arizona Public Service Co.

(formerly Arizona Nuclear Power p

RECIP.NAME RECXPIENT AFFXLXATXON Document Control Branch (Document Control Desk)

SUBJECT:

Forwards response to questions re TS amend for figure 3.2-1.

DISTRIBUTION CODE:

A001D COPIES RECEXVED:LTR P ENCL g SIZE:

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NOTES:Standardized plant.

05000529 RECXPIENT ID CODE/NAME PD4-2 LA HOLIAN, B INTERNAL: ACRS NRR/DORS/ONDD NRR/DRPW NRR/DSSA/SRXB OC/LFDCB EC -FIQB 01 EXTERNAL: NOAC COPXES LTTR ENCL 1

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N NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACTTHE DOCUMENTCONTROL DESK, ROOM Pl-37 (EXT. 504-2083 ) TO ELIMINATEYOUR NAMEI'ROM DISTRIBUTIONLISTS FOR DOCUMENTS YOU DON'T NEED!

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PHOENIX. ARIZONA85072<999 WILLIAML. STEWART EXECUTIVEVICEPRESIDENT NUCLEAR 102-03080-WLS/RAB/JST August 11, 1994 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station P1-37 Washington, DC 20555

References:

Letter 102-03026, dated July 1, 1994, "Proposed Amendment to Unit 2 Technical Specification Figure 3.2-1," from W. L. Stewart, APS, to NRC,

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Unit 2 Docket No. STN 50-629 Responses to Questions Regarding Technical Specification Amendment Request for Figure 3.2-1 File: 94-005<19.06 94-066-026 The enclosure to this letter provides the responses to questions concerning the technical specification amendment request referenced above. This information was requested by Brian Holian, Senior Project Manager, NRR, and is intended to assist in the NRC's review and approval of the amendment.

Should you have any questions, please contact Richard A. Bernier at (602) 393-5882.

Sincerely, WLS/RAB/JST/rv Enclosure cc:

K. E. Perkins K. E. Johnston B. E. Holian A. V. Godwin (ARRA) 9408230242 940Sil, PDR ADOCK 05000529 P.

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ENCLOSURE RESPONSES TO QUESTIONS REGARDING AMENDMENTREQUEST TO UNIT 2 TECHNICALSPECIFICATION FIGURE 3.2-1

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RESPONSE TO QUESTIONS REGARDING PROPOSED AMENDMENTTO TECHNICALSPECIFICATION FIGURE 3.2-1 FOR PVNGS UNIT2 Page numbers refer to the applicable page number in the reference.

Question: Page 3. The Non-LOCA reanalyses were performed assuming 2000 plugged steam generator (SG) tubes, with a maximum of 1000 plugged tubes per SG. What happens ifthese tube plugging limits are exceeded?

Answer: APS is working on a contingency plan such that, ifthe above numbers are exceeded during the next outage an analysis willhave been performed which would bound the expected results. APS willinform the staff ifthe current tube plugging limits are exceeded, and how any adverse effects are being bounded (e.g., by revising Core Protection Calculator (CPC) penalty factors or Core Operating LimitSupervisory System (COLSS) margin requirements).

Appropriate revisions willbe incorporated into the UFSAR.

Question; Page 12. The LOCA analyses are for a 1100 tube/SG limit.The last two inspections indicate that this limitmay be exceeded in the upcoming inspection. What happens then?

Answer: APS has anticipated that this may occur, and additional LOCA analyses are being performed to bound this eventuality. We willinform the staff ifthe current tube plugging limits are exceeded, and how any adverse effects are being bounded (e.g., by revising the linear heat rate specified fuel design limits). Appropriate revisions willbe incorporated into the UFSAR.

Question: Page 4. Give some examples of CPC coefficient changes (i.e., due to the proposed decrease in allowable T<<td values (550-570 F) at fullpower).

Answer: The CPC filtercoefficients for the affected cycles were evaluated, and no changes were required. These filtercoefficients are designed to compensate for the rate ofchange in temperature (i.e., LPF/sec) during heatup and cooldown events, and are not a function of initial temperature. The current CPC filtercoefficients are valid forreactor coolant system (RCS) initial conditions across the analytical T<<~d range of interest (550-570 F).

Question; Page 4. Have cycle specific analyses forimplementation ofthe main steam safety valve (MSSV) and pressurizer safety valve (PSV) setpoint tolerance been performed?

Answer: The cycle specific analyses are being performed at this time. These analyses, including any corresponding revisions to the Core Operating LimitReports (COLR), willbe completed prior to implementation of the MSSV and PSV T. S. change on December 1, 1994.

Question: Page 5. Why doesn't the change in RCS density (due to changes in allowable temperature) affect the CEA drop times (assumed in the analyses)? Provide further explanation why results are deemed independent ofT<<td.

Answer: The safety analyses assume a CEA drop time of 4.0 seconds. Actual drop times are approximately 2.5 seconds, based on drop tests performed at a nominal T<<~d of 565 F. The slowest drop time to date forPVNGS, all units, is 2.83 seconds. At565 F,2250 psia, RCS water density is 45.863 ibm/ft. At550 F, 2250 psia, the RCS water density is 46.864 ibm/ft. This small change in density has a negligible effect on CEA drop time. Additionally, the average density of the fluidin the core is less than this value as power is increased. There is sufficient

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0 RESPONSE TO QUESTIONS REGARDING PROPOSED AMENDMENTTO TECHNICALSPECIFICATION FIGURE 3.2-1 FOR PVNGS UNIT2 margin in the actual vs. assumed CEA drop times (2.83 vs. 4.0 seconds) to bound RCS density effects for the temperature range of interest.

Question: Page 5. Was credit taken forModerator Temperature Coefficient (MTC)? What values of MTC were used for U1 and U3?

Answer: Yes, credit was taken for a negative MTCin Units 1 and 2, since the units were past the beginning ofcycle. The Unit 3 analysis was performed as part of the reload analysis report. The Unit 1 analysis used a value of-3 percent millirho/F(pcm)(Measured value in January 1994 was

-9.78). Unit 2 used a value of -6 pcm/F (Measured value in October 1993 was -8.3). Both Units have significantly more negative MTC values than the values used in these analyses.

Question: Page 6. Why is 50% power limitingfor the Part Length CEA Drop (PLRDROP) event?

Is this discussed in the UFSAR?

Answer: The COLR power dependent insertion limitforpart length rods applies a step change at 50% power. Above this limit, the part length rods are not allowed to be in a configuration that would cause a positive reactivity insertion, should a rod drop occur. Hence, 50% power becomes the limitingpower at which this event could result in a positive reactivity insertion. The analysis bounds instrument uncertainties for indicated vs. actual power. The PLRDROP analysis is performed for margin setting and/or COLR revision, and is not a Chapter 15 event.

Question: Page 9. Why doesn't the pressurizer spray malfunction event depend on temperature?

Answer: The COLSS/CPC analysis utilizes bounding values for the maximum two second change that can occur for several thermal hydraulic related plant parameters, including RCS pressure, to establish correction factors forcalculating DNBR. The maximum change considered forRCS depressurization is selected to bound the malfunction ofthe pressurizer pressure control system. The current analytical value is -50 psia over a two second interval, and is conservative with respect to the depressurization rate that would occur due to an actual malfunction of the pressurizer pressure control system for Tca~d between 550 to 570 F.

Reference:

102-03026-WLS/RAB/GEC, "Proposed Amendment to Unit 2 Technical Specification Figure 3.2-1, letter from W. L. Stewart to USNRC, dated July 1, 1994.

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