ML20085D143

Forwards Suppl 1 to BAW-2127, Plant-Specific Analysis in Response to NRC Bulletin 88-011, 'Pressurizer Surge Line Thermal Stratification,' Davis-Besse Nuclear Power Station, Unit 1

ML20085D143
Person / Time
Site:	Davis Besse
Issue date:	10/08/1991
From:	Shelton D CENTERIOR ENERGY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20085D144	List: ML20085D143 ML20085D147
References
IEB-88-011, IEB-88-11, TAC-72128, NUDOCS 9110150273
Download: ML20085D143 (8)

Text

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CENY2RIOR ENERGY Donald C. Shelton X0 Ma$ son Aveme

%ce PtrM Nxicar 1c400, OH 43f 52 0001 Davis Besse (419)249 2330 Docket Number 50-346 License Number NOF-3 Setfal Number 1982 October 8, 1991 United States Nuclear Regulatory Commissiors Document Control Desk Vashington, D. C. 20555

Subject:

Justification fot Continued opetation (JCO) and Response to Part 1.d NRC Bulletin Number PB-ll, Pressuticer Surge Line Thermal Stratification (T/.C Number 72128)

Gentlemen:

Toledo Edison submitted a letter (Serial Number 1873) dated November 19, 1990 which justified continued plant opetation until restatt from the Seventh Refueling Outage (7RFO) during the continuing effort to complete the final fatigue analysis in accordance with Action 1.d of NRC Bulletin 88-11, "Pressurizet Surge Line Thermal Stratification". This submittal included a commitment that, prior to the restart from the 7RF0, Toledo Edison vouldt (1) Submit the final fatigue analysis for the Davis-Besse Nuclear Power Station Unit 1 (DBNPS) to ensure compliance with applicable code requirements and regulatory commitments, or (2) submit a JC0 and a desetiption of proposed corrective actions to effect a long tetm resolution. Toledo Edison has completed a JC0 as described in option (2) above. This JC0 vill be effective until the heatup following the Ninth Refueling Outage which is ptesently schedule, for October 1994.

Backgtound on December 20, 198R, the NRC issued Bulletin 88-11, " Pressurizer Surge Line Thermal Stratification" (Toledo Edison tog Number 1-1988). The Bulletin addressed the phenomena of thermal stratification and striping and their etfects on the Pressurizer Surge Line (PSL). Thermal stratification and striping may cause mechanical loads on the PSL vhich vere not accounted for in the original design basia thereby invalidating the existing fatigue analysis, oltOt96273 911009 FDR ADOCt: O'~iOOO946 r.

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• . Docket Number 50-346 *

• License Number NPFr3 Serial Number 1982 Page 2 The bulletin as it applies to the DBNPS requited four actions -

1.a. Conduct a visual inspection of the PSL to determine any gross discernible distress or structural damage, including piping, piping supports, pipe vhip restraints and anchor bolts.

1.b. Demonstrate that the pressurizer surge line meets the applicable design codes and other Final Safety Analysis Report (FSAR) and regulatory commitments for the licensed life of the plant, considering thermal stratification and thermal striping in the fatigue and stress evaluations, using a plant-specific or generic bounding analysis. If this analysis does not equal or exceed the duration of the operating License, then submit a JC0 for the period bounded by the analysis.

l.c. If the aforementioned analysis does not equal or exceed the j operating License duration, then obtain plant data on thermal  !

stratification, striping, and deflection.

1.d. Utilizing data from 1.c. above, complete an updated stress and fatigue analysis that ensures compliance with applicable code requirements and regulatory commitments within two years after receipt of this Bulletin (January 2, 1991). If unable  !

to show compliance, submit a JC0 and description of the proposed corrective actions for effecting long team ,

resolution.

In accordance with Bulletin Action 1.a., Toledo Edison submitted a  !

letter (Serial Number 1633) dated March 3, 1989, to the NRC. The letter reported the initial results of the Toledo Edison program to assess the integrity of the surge line, which included a visual inspection. The visual inspection detected no gross discernible distress or structural damage to the surge line, including piping, piping supports, pipe whip restraints, and anchor bolts.

4 Pursuant to Bulletin Action 1.b., Toledo Edison, in conjunction with the B&W Owners Group (BV0G), submitted a letter (Serial Number 1671) {'

dated June 2, 1989 to the NRC. 1he letter transmitted the results of the BV0G and DBNPS-spectfic analysis, as well as the DBNPS JCO. .The DBNPS JC0 vas submitted as a result of the conservative analysis, justifying a total of 57 heatup/cooldown cycles for a fatigue usage factor of 1.0. This was less than the design basis of 240 alloveble cycles, but a sufficient margin of 17 full cycles was still available to ensure safe plant operation vell beyond the end of the Seventh Fuel Cycle. By a letter (Log Number 1-2344) dwted August 7, 1990 (NRC Bulletin Number 88-11. " Pressurizer Surge Line Thermal .

Stratification-Evaluation of DV0G Bounding Analysis "(TAC Number M72128)), the NRC issued the results of its review of she BV0G bounding analysis,-Topical Report (BAV-2085), and found that sufficient information had been provided to justify continued plant operation until Toledo Edison completed its final report by January 2, 1991 (as committed by letter Serial Number 1671).

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. Docket Number 50-346 *

• License Number NPFr3 ,

Serial Number 1982 l Page 3 i Toledo Edison, in conjunction with other B&V plant ovners, initiated '

the BV0G PSL Thermal Stratification Program. 'In accordance with i Bulletin Action 1.c., this program was designed to utilize collective  ;

efforts in data acquisition. The bulletin stipulated the acceptability i of this approach provided that similarity of the PSL design, geometry i and plant operation could be demonstrated. The DV0G PSL program .

recognized the difference in the geometry of the DBNPS PSL with respect  !

to the other B&V plants and was tailored to reconcile those  !

difforences. The program provided for the instrumentation of the Duke  !

I Power Company's Oconec Unit 1 PSL for both temperature and deflection.

The intention was to account for the geometric differences between DBNPS and Oconee Unit I through use of thermal-hydraulic analytical modeling of the surge line. Verification of the.model against the thermal measurements at Oconee Unit 1 vould permit confident prediction  ;

of the DBNPS thermal stratification conditions based upon a similar model adjusted to acevunt for DBNPS geometry. . The output of the '

program would be the updated stress and fatigue analysis in accordance with Action 1.d. of the Bulletin.  ;

Toledo Edison was subsequently informed by B&V Nuclear Service Company (BVNS) that the correlation of the thermal-hydraulic model against Oconee Unit I data proved inadequate for reliable use in characterizing  ;

thermal stratification conditions at the DBNPS. The BVNS recommended ,.

that Toledo Edison install special instrumentation on the surge line to  ;

gather the necessary information on thermal stratification and the related piping deflections.. A temperature and deflection data acquisition system on the DBNPS PSL vas installed during the DBNPS Sixth Refueling Outage. The data acquisition system was in place to monitor the PSL during restart from the 6RF0 (hentup for Seventh fuel i Cycle) to acquire DBNPS plant specific data. ,

During the heatup for the Seventh Fuel Cycle (July 1990), data was gathered to characterize both the thermal stratification conditions and  ;

the resulting deflection of the surge line. Both tbn thermal and deflection conditions vete to be-quantified to provide the necessary information to reviso the ifME Code Stress Report in compliance with ,

Action 1.d. of the NRC Bulletin 88-11 by January 2, 1991. Ilovever, due i to the extent of the effort required,-this analysis could not be completed for the DBNPS by January 2, 1991.

Toledo Edison submitted a letter (Serial Number 1873) to the NRC dated November 19, 1990. This letter justified continued plant operation for the DBNPS until restart from 7RF0 vhile efforts were' ongoing'to >

complete the final fatigue analysis. This submittal stated that, priot to restart from the 7RFO. Toledo Edison voulds (1) submit the final ,

fatigue analysis for the DBNPS to ensure compliance with applicable code requirements and regulatory commitments. or-(2) submit a JC0 and a description of proposed corrective actions to effect a long term resolution.

On December 31, 1990, the BV0G submitted the Topical Report BAV-2127, .

" Final Submittal - Pressurizer Surge Line Thermal Stratification", in i accordance with Action 1.d. of the Bulletin.

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Docket Numbet 50-346 ' '

License Number NPPr3' Serial Number 1982

-Page 4 Although much of the methodology developed by the 11V0G and repot ted to the NRC in Topical Report BAV-2127 vas directly applicable to DBNPS, analyses were performed following the heatup from the 6RPO to specifically consider the DBNPS PSL configuration and the information obtained inom the special sutge line insttumentation installed during the 6RPO. The analyses also considered the operating history of the unit, the specific history of vhip restraint cicarances, the free motion limits of supports, stresses from velded attachments, effectiveness of thermal insulation and the specific plant operating ptocedutes and practices. The detailed review of opetating history

-shoved that the surge line has experienced 40 heatup and cooldown cycles through cooldown from Cycle Seven operation and including hot functional testing.

Justification for_ Continued Operation The enclosed report, BAV-2127 Supplement 1, " Plant-Specific Analysis in Response to NRC !)ulletin 08-11 Pressurizer Surge Line Thermal Stratification," provides the plant-specific analysis for the DHNPS.

The repott shows that stresses for the surge line pressure boundary components temain within allovable limits and that accumulated fatigue usage vill satisfy the applicable code requitements and regulatory commitments-for the 40 year licensed life of the DBNPS.  !

Toledo Edison has also confirmed that the surge line drain line and its suppet ts vill remain within code ellovable limits over the lif etime of the plant considering displacements of the drain nozzle connection due to surge line thermal stratification. The surge line snubbers and variable spring support have been evaluated for potential interfarences reculting from the surge line stratification deflections as predicted by the plant specific analysis. The snubbers were found to have sufficient travel to accommodate the increased stratification movements: however, the variable spring support PSt!-ill could interf ere with the downward travel of the surge line as documented in DAV-2127, Supplement 1. The suppott structure for PSU-H1 vas evaluated for the increased loading due to the '

potential travel intetference and was found to meet all design allovables except for the anchor bolts utilized on the structure which have a minimum safety factor of approximately 2.9 versus a nnrmal design safety factor of 4.

The conclusion that the surge line vill meet code and regulatory requitements for the 40-year licensed life of the plant is based upon plans to limit future temperature differences between the pressurizer and reactor coolant system during heatup and cooldown consistent with the commitments made to the NRC by other utilities in the BV0G. It is also based upon certain commitments for physical modifications, described in more detail in Section 8 of the enclosed supplemental report, which include increasing clearances in the surge line whip restraints and the upgrading of surge line thetmal insulation. ,

The surge line whip restraint modification was initially intended to he pertoimed during the 7RFO. However, consideting the recent results of the stress and fatigue analyses performed in response to NRC Bulletin

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.- Docket Number $0-346 ' '

LicenFe Numbet NPF,-3 Settal Number 1982 ,

Page $ l Number 88-11, additional containment valkdowns and evaluations ate I requited in otdet to confitm that-the modification remains in  ;

conf ormance with the NRC 11 ranch Technical Position HED 3-1, " Postulated .

Ruptute 1ocations in Fluid Systems Piping Inside and Outside i containment". Therefore, the modification of the surge line whip restraints vill not be performed during 7RF0 as originally planned.

The analysis for DBNPS used the same methodology in determining stress indices for certain surge line elbows as used in the DV0G's Topical Report BAV-2127. In reviewing IIAV 2127, the NRC has identified an untesolved issue with ngards to this methodology (NRC letter dated July 24, 1991). Toledo Edison is patticipating with the DV0G's effoit to resolve this issue.

In view of these remaining two issues and in accordance with Action i 1.d. of NRC Bulletin Number 8B-11. Toledo Edison is proceeding on the basis of this JC0 vith an updated description of ptoposed corrective actions to effect long tetm resolution.

Toledo Edison vill delay completion of the physleal modifications described in Section 8 of the encloss d supplemental report pending the ,

completion of the evaluations on the whip restraint modifications and the DV0G's tesolution of the issue on methodology for determining fatigue usage of the surge line c)bovs. That votk and any necessary physical mofi!! cations and sitets and tatigue reanalysis will be completed prior to heatup from the Ninth Refueling Outage. ,

Accordingly, BVNS has recalculated (calculations are available for  !

reviev) the maximum fatigue usage for all the surge line ptessure boundary components up to the rtart of the heatup (tom the Ninth Refueling Outage with the following results Susge 1,lne Fatigue Usage C,omponent Factor Surge line 0.22 Pressurieer Nozzle 0.23 ,

Hot Leg Nozzle 0.21 This evaluation is conservatively based upon the historical evaluation described'in the enclosed report, and upon the assumption that no imptovements are made in eithet operation or in configuration until the Ninth Refueling Outage. Ten additional heatups and cooldovns are assumed to occur during the period between cooldown for the curtent 7RF0 and cooldown for the Ninth Refueling Outage. This vould raise the total count from 40 at start of the 7RF0 to 50 heatups and cooldovns at the end of-the Ninth *el Cycle. Based on the operating performance of the DbNpS in recent y is, this is a conservative estimate. r

' ' .* Docket Number 50-346 , ,

License Number NPFr3

Serial Number 1982 l j Page 6

-Corrective Actions to Effect a Long Term Resolution

. -t l In order to ensure long term acceptability of the surge line, Toledo

Edison pl1tns to carry out the following actions which are consistent

> vitS the assumptions and findings of the analysis in the enclosed 4

reports i .

i. 1. Procedures vill be modified to ensure operation within the bounds  !

of pressure-temperature limito during heatup and cooldovn as described in Section 8 of BAV-2127, Supplement 1. These are i l planned to be completed by startup from the Seventh Refueling Outage.

• i i 2. The cycling of the makeup flov vill be reviewed to ensure that any

related fatigue effects due to thermal striping in the surge line l vill not significantly affect surge line reliability.. In the event

, that plant modifications a e requited, they are planned to be l completed before heatup from the Ninth Refueling Outage.

i l 3. Hodifications vill be completed ensuring that the surge line whip i -restraints and spring support PSU-ill do not interfere with piping j thermal displacement. Also, the anchor bolts on the support

structure for PSU-ill vill be restored to a safety factor of 4.

These modifications are planned to be completed before heatup from j the Ninth Refueling Outage. +

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4. Consistent with modifications to the surge line whip restraints,

the surge line thermal insulation performance vill be upgraded by

{ suitable modifications. The improvement in the insulation vill

result in reduced top-to-bottom temperature differences, more j nearly resembling those observed at Oconee Unit 1. This action is

planned to be completed before heatup from the Ninth Refueling j Outage, i

5. During the heatup following completion of the insulation [

I improvements, the surge line thermal conditions vill be monitored i 'to confirm the conservatism of the analysis for future surge line i conditions.

6. .The number of heatups and cooldowns will-be monitored to ensure that 50 heatup/cooldown cycles are not exceeded prior to-heatup from the Ninth Refueling Outage. +

Summary Toledo Edison believes that. continued operation of the DBNPS during the completion of the above planned actions is justified by the ample  ;

fatigue margin remaining beyond the Ninth Refueling Outage. Prior to beatup from the Ninth-Refueling Outage Toledo Edison vill submit-a second supplement to BAV-2127 containing a revised analysis for the full 40 year licensed lifetime of the DBNPS. It is planned that the revised analysis-vill utilize elbov stress and fatigue methodology as accepted by the NRC upon completion of development by the BV0G and vill incorporate the effects of the above planned actions.

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• • - Docket Number $0-346 ' '

i License Number NPP-3

. Serial Number 1982 I. Page 7 F

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Should you have any questions or require additionn) information, please l contact Mr. Robert V. Schrauder, Hanager --Nuclear Licensing, at (419) j 249-2366.

j Vety-truly,yours, .

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j. Pnclosute l ces A. D. Davis, Regional Administrator, NRC Region III 4 J. B. Ilopkins NRC Senior Ptoject Manager V. 1,evis. DB-1 NRC Senior Resident Inspector

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. Docket Number 50-346 *

• License Number NPT-3 Set f ul Numbai- 1982 i Enclosure l Page 1 i L

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RESPONSE TO NRC llVLLETIN 14UMllER 88-11 PRESSURIZER SURGE LINE TilERHAL STRATIFICATION FOR DAVIS-IlESSE NUCLEAR POVER STATION P

UNIT NUMBER 1 This letter is submitted in conformance with the Atomic Energy Act of  !

1954 Section 182a, in response to NRC llulletin 88-11 Pressurizer Surge  :

Line Thetmal Stratification. ,  ;

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D. CF Shelton, Vice President, Nuclear sworn and subscribed before me this 6th day of October. 1991. .

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