ML17310A415

Forwards Response to Request for Addl Info Re NRC Bulletin 88-008.Licensee Will Install Thermocouples on Pressurizer Auxiliary Spray & Main Spray Sys in Unit 3 No Later than Unit 3 Fifth Refueling Outage in Fall of 1992

ML17310A415
Person / Time
Site:	Palo Verde
Issue date:	06/30/1993
From:	Conway W ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
102-02555-WFC-T, 102-2555-WFC-T, IEB-88-008, IEB-88-8, TAC-M69664, TAC-M69665, TAC-M69666, NUDOCS 9307070057
Download: ML17310A415 (12)

Text

ACCEI ERAT DOCUMENT DISTRJ UTION SYSTEM REGULATO INFORMATION DISTRIBUTION, STEM (RIDS)

'k ACCESSION NBR:9307070057 DOC.DATE: 93/06/30 NOTARIZED: NO DOCKET FACIL:STN-50-528 Palo Verde Nuclear Station, Unit 1, Arizona Publi 05000528 STN-50-529 Palo Verde Nuclear Station, Unit 2, Arizona Publi 05000529-STN-50-530 Palo Verde Nuclear Station, Unit 3, Arizona. Publi 05000530 AUTH.NAME AUTHOR AFFILIATION CONWAYiW.F.

Arizona Public Service Co. (formerly Arizona Nuclear Power RECIP'.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

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SUBJECT:

Forwards response to request for addi info re NRC

'Bullet'in 88-008.Licensee will install thermocouples on pressurizer auxiliary spray

& main spray sys in unit 3 no later than unit 3 fifth refueling outage.in Fall of 1992.

DISTRIBUTION CODE:

IE16D COPIES RECEIVED:LTR /

ENCL I SIZE:

TITLE: Bulletin Response 88-08 Thermal Stress in Piping to RCS.

.NOTES:STANDARDIZED PLANT Standardized plant.

Standardized plant.

D 05000528 05000529 05000530 D

D RECIPIENT ID CODE/NAME'DV PD TRAN,L INTERNAL: AEOD/DOA NRR/DRPW/OGCB NRR/EMCB NRR/PDII-1 RES/DSIR/EIB EXTERNAL: NRC'DR COPIES LTTR ENCL 1

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1 1

1 1

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1 1

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1 RECIPIENT ID CODE/NAME TRAMMELL,C

'RR/DE/EMEB NRR/DSSA NRR EMEB EG 02'GN5 FILE 01 NSIC COPIES LTTR ENCL 1

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1 1

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D NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO'REDUCE WASTE} CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 504-2065) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON',T NEED!

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TOTAL NUMBER OF.COPIES REQUIRED:

LTTR 15 ENCL 15

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WILLIAMF. COi'WAY EXECUTIVEVIC PRESIDEIIT NUCLEAR Arizona Public Service Company P O,BOX 53999

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PHOENIX ARIZONA85072.3999 102-02555-WFC/TRB/ZJE, June 30, 1993 U. S. Nuclear Regulatory Commission ATlN: Document Control Desk Mail Station P1-37 Washington, DC 20555 Reference 1:

Letter from the NRC to W. F. Conway, dated April 20, 1993 "Evaluation of the Response by Arizona Public Service Company to NRC Bulletin 88-08" (TAC Nos M69664, M69665, and M69666)

Reference 2:

Letter 161-04571-WFC/JMQ, dated January 15, 1992, "Response to NRC Request for Additional Information on NRC Bulletin 88-08"

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Units 1, 2, and 3 Docket Nos. STN 50-528/529/530 Response to Request for Information Regarding NRC Bulletin 88-08 File No: 93-056-026 The enclosure to this letter contains Arizona Public Service Company's (APS) response to Reference 1 which requested information regarding the status of APS'ctions associated with NRC Bulletin 88-08.

As indicated in Reference 2; APS intended to amend Technical Specification Table 5.7-2 forfuture logging of spray transients and calculation ofthe cumulative fatigue usage factor.

The proposed amendment will enhance the ability to more accurately calculate the pressurizer spray nozzle cumulative fatigue usage factor.

The acquisition of actual plant data has provided the basis for review and analysis to support the proposed amendment.

This amendment is expected to be submitted to the NRC by August 31, 1993.

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9307070057 930630 PDR ADOCK 05000528 6

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U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Information Regarding NRC Bulletin 88-08 Page 2 If. you have additional questions, please contact. Thomas R.. Bradish at (602) 393-5421.

Sincerely, WFC/TRB/ZJE/ap Enclosure cc:

B. H. Faulkenberry J. A. Sloan

ENCLOSURE INFORIVIATIONREGARDING NRC BULLETINSS-08

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'ENCLOSURE ARIZONAPUBLIC SERVICE COMPANY PALO VERDE NUCLEAR GENERATING STATION INFORMATIONREGARDING, NRC.BULLETIN'8-08 Arizona Public Service Company (APS) letter to the NRC dated January 15, 1992,

,identified four actions to.be completed in response to NRC Bulletin 88-08; These actions were: 1) Complete assessment of Unit-3 temperature monitoring data, 2)

'Evaluate the need for additional long term surveillance.

activities;

3) Submit Technical Specification Change to Table 5.7-2, and 4) Perform bounding thermal stratification stress analysis. NRC letter dated April 20; 1993 requested that APS provide the status of. the, following actions:

Assessment of Auxiliary Pressurizer, Spray Piping Temperature Monitoring Data.and of Normal Operating Temperature Data Status:

.Initial review of the temperature data recorded on Auxiliary Pressurizer Spray System,(APSS) piping during Unit-3, Cycle-3, did not indicate effects of in-leakage as o'utlined in.NRC Bulletin 88-08. Specifically, the Unit-3 data did not contain temperature oscillations such as. found at another nuclear facility described in the bulletin. Also, large top-to-bottom temperature differences as may be expected due to steam/water thermal stratification during heatup and cooldown were not evident. Therefore, APS considered the observed temperature differences (60 to 115 degrees Fahrenheit) 'in the APSS piping temperature profiles are, most likely, due to thermocouple bias, insulation effects, and/or pressurizer steam convective cooling.

Since'these. temperature differences exceeded the 50 degrees Fahrenheit criterion specified by the NRC, APS performed a bounding thermal stratification stress analysis-to ensure continued'APSS piping integrity for the life of the plant regardless of the mechanism(s) that led to the observed temperature differences.

However, close examination of the Unit-3 temperature data revealed a

temperature fluctuation effect associated with the initiation and termination of. charging flow.

Although not conclusive, this suggested that valve leakage may be causing the stratification.

A small amount of in-leakage from the charging system, affected by the conductive 'heating of the pressurizer and adjacent

piping, may account for the temperature distribution observed. during. Unit-3 testing. These. results formed the basis for APS to implement permanent monitoring of the APSS piping temperature profiles.

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APS also examined the observed APSS piping temperature distribution for normal operation.

The temperature differences in the APSS temperature profiles (up to 90 degrees Fahrenheit) are, most likely, due to the effects of piping insulation and the ambient conditions around the pressurizer.

Specifically, convection along the exterior of the pipe in a chimney effect may produce erroneous results.

Additionally, cooling of the bottom of the insulation by containment air conditioning units may affect the temperature distribution in the pipe.

Similar to the heatup and cooldown data, no temperature fluctuations were observed in the normal operation data.

The observed temperature differences are bounded by the 115 degrees Fahrenheit value applied in the thermal stratification bounding analysis.

2.

Long Term Surveillance Plan for APSS Piping Status:

APS will install thermocouples on the pressurizer auxiliary spray and main spray systems in Unit-3. These thermocouples will be installed no later than the Unit-3 fifth refueling outage in the fall of 1995.

These thermocouples will serve as a

pilot program to determine which thermocouples should be installed at Units 1 and 2.

It is anticipated that the temperature monitoring program will help determine the mechanism associated with thermal stratification in the APSS piping and willverify that the limitingconditions of service currently used in the stress evaluations are valid.

After the implementation of this long-term surveillance plan, any thermal stratification caused by valve in-leakage will be detected, and the potential for valve degradation willthen be addressed.

3.

Results of the Bounding Thermal Stratification Analysis Status:

Since the observed temperature differences in the APSS temperature profiles exceeded the 50 degrees Fahrenheit criterion set by the NRC, APS performed a bounding thermal stratification stress analysis.

A temperature difference top-to-bottom value of 115 degrees Fahrenheit was used in the APS analysis.

The effects of thermal stratification in the 2-inch APSS line were included for the line segment from the tee above the pressurizer to the check valve approximately three feet upstream of the tee.

This analysis demonstrated that the cumulative fatigue usage

factor, including the effects of thermal stratification, meets ASME B&PV Code Section III ( NB-3653.1 through NB3653.6) for 40 years plant life. Therefore, regardless of the mechanism(s) behind the APSS piping temperature differences, the piping has been qualified for the licensed plant life.

In conclusion, APS has completed the bounding thermal stratification analysis which showed that APSS piping is qualified for the licensed plant life. APS will install additional thermocouples on the AuxiliaryPressurizer Spray and Main Spray systems for long term surveillance of temperature stratification in order to detect valve in-leakage and degradation which may lead to further stratification of piping temperatures.

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