ML19256G111

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Submits Addl Info Re LER 79-151/01T-0.During Review of IE Bulletin 79-14 Re Seismic Analysis,Discovered That Amplified Response Spectrum Curves Had Two or More Values of Acceleration for Same Period.Tables Encl
ML19256G111
Person / Time
Site: North Anna Dominion icon.png
Issue date: 12/19/1979
From: Stallings C
VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To: James O'Reilly
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 7912270468
Download: ML19256G111 (11)
v • d • e


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VIRGINIA ELECTRIC AND Pow e a ConrANY Rzcarwown,VznorwzA n3262 December 19, 1979 Mr. James P. O'Reilly, Director Serial No.1152 Office of Inspection and Enforcement P0/RMB:sav U.S. Nuclear Regulatory Commission Docket No. 50-338 Region II License No. NPF-4 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303

Dear Mr. O'Reilly:

Pursuant to North Anna Power Station Technical Specifications, the Virginia Electric and Power Company submitted Licensee Event Report No. LER-79-151/01T-0 dated November 20,.1979 which identified an inconsistency in the seismic analy-sis of some safety related lines at North Anna Unit No. 1. The purpose of this letter is to fully describe the type of inconsistencies found to exist in the seismic analysis, to identify the systems affected, and to describe the cor-rective action taken.

During the 1&E Bulletin 79-14 review on North Anna Unit No. I to determine the effect of changes in valve weight on pipe stress analysis, an inconsistency was discovered in the way which certain of the Amplified Response Spectrum (ARS) curves were used as input to the seismic stress analysis. A full review was then =ade of all ARS curves and seismic calculations to identify the number and type of inccusistencies that exist. This review indicated that three types of inconsistencies exist as described below:

1. Certain ARS carves had two or more values of acceleration for the same period (i.e., multiple periods) and in some cases the smaller acceleration value was the one used in the calculation.
2. Peak spr"Mng of some curves was not exactly 15 percent of the peak's period as described in FSAR Section 3.7.3.
3. The ARS curve used in the seismic analysis 'of a few piping sys-tems did not envelope the current ARS curve developed for the area in which the piping was installed.

It has been deter =ined, by a complete review of the ARS input to the pipe stress calculations, that there are no inconsistencies other than those de-scribed above. These discrepancies affect only the dynamic analysis of the piping systems; the static analysis involving seismic building movement is not affected.

The inconsistencies described were found to exist in 44 MSK's (an MSK is an isometric piping drawing constituting a stress problem) on Unit No. 1. The specific piping systems affected, the location, and type of inconsistency found are listed in Table No. I hd is letter. The affected systems are

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VanOaxtA ELzcTaic A.1D POWER COM S Mr. James P. O'Reilly, Director located in the Service Water Pump House, the Auxiliary Building, the Safe-guards Building, the Fuel Building, the Auxiliary Feedwater Pump House, and the Main Steam Valve House. The systems affected are Service Water, Quench Spray, Safety Injection, Main Steam, Charging and Volume Control, Auxiliary Feedwater, Boron Recovery, Fuel Pool Cooling, Component Cooling, Refueling Purification, and Containment Vacuum. No portion of these systems within the containment or the reactor coolant system pressure boundary are affected.

Since the inconsistencies found could potentially result in nonconservative pipe stresses, pipe support loads, and equipment loads in safety related sys-tems, a program was developed to ensure adequate design of these systems and further to evaluate the effect, if any, on the high energy pipe break analysis.

The program consists of re-running the piping dynamic analysis on the affected systems using the proper ARS input. After completion of the stress analysis, pipe stress and pipe support loads will be evaluated to ensure that pipe stresses are less than the code allowable and pipe supports are adequate.

Piping or pipe supports found to be inadequate will be modified to be accept-able under the revised loading. Equipment nozzle loading and equipment support loading will be reviewed. Should the load be unacceptable, approval of new loads will be obtained from the equipment manufacturer or the system will be modified to be acceptable under the new loading. Revised structural loading at anchor points and wr.:nt supports will be evaluated and modifications made if necessary. Also, since three of the affected MSK's contain high energy lines, these lines will be reviewed using the revised ARS data and existing high energy pipe break criteria. If required, new or different break points will be postulated and the effect analyzed. Pipe whip restraints, impingement shields, etc., will be added or modified if necessary. The re-stress analysis and s=pport review will be done in accordance with the methods of the original desiz1.

The results of the analysis to date is shown in Table 2 and is summarized be-low:

1. Total calenlations to be reviewed. 44
2. Total c=1mintions in which pipe stress review 44 is complete.
3. Stress / pipe support calculation review complete. 43
4. Total number of hangers to be reviewed. 439
5. Total number of hangers found satisfactory to date. 422
6. Total nu=ber of hangers remaining to be reviewed. 4
7. Total modifications to existing hangers required. 13
8. Total new hangers to reduce pipe stress to less 12 than code allowable.
9. Equipment problems - Quench Spray Pump Nozzles (To be resolved with the addition of 9 44 }g} hangers)

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' Cc c . a v:ROINIA Es.zersac AND Powen COMPANY TO J O'hmn Dh av -b All MSK's have been re-run with the proper ARS curve and new pipe stress and support loads have been determined. As indicated above, twelve new supports are required to reduce pipe stress to less than code allowable. These new supports are being designed and installed at this time and will be completed prior to power operation of North Anna Unit No. I currently scheduled for the week of December 23, 1979. Of the total number of hangers reviewed to date, only thirteen hangers have been found to be inadequate to support the new loads. These hangers are being re-designed and will be modified. In addition, nh (9) new hangers will be designed and installed prior to power pperation to reduce the Quench Spray Pump nozzle loads to less than the current Manu-facturer's allowable load. We are attempting to complete the required review of the remaining 4 hangers by December 22, 1979. All hangers on systems necessary to . reach and maintain the unit in a Safe Shutdown status will be reviewed and modified if necessary prior to power operation of Unit No. 1.

Safe shutdown systems are considered to be all Engineered Safeguards Systems, the Auxiliary Feedwater System, the Main Steau System and those systems neces-sary to operate the Residual Heat Removal System. The systems necessary for safe shutdown are shown in Table 1. Analysis of equipment nozzle loads and equipment support loads will continue through February, 1980.

A procedure has been developed to ensure a timely and thorough review of the remaining pipe hangers it non-safe shutdown systems and equipment nozzle and equip::ent support loads in all affected systems following the start-up of Unit No. 1. Stone and Webster, our Architect-Engineer, will continue the analysis and will notify us w%n a nonconformance is identified. A problem will be identified as a nonconformance if any of the following criteria are met:

1. Pipe stress above code allowable.
2. Pipe w u., member stress above design allowable.
3. Equipment nozzle loads above design allowable.
4. Equipment support loads above design allowable.

If a mufur - is identified, an evaluation of the significance of the noncon u 2.uce vill begin immediately to determine if the operability of the systes ihr be jeopardized during a seismic event. The evaluation will be dona 12 two (2) phases similar to that required when a nonconformance is ident M in accordance with the requirements of I.E. Bulletin 79-14. Follow -

ing htification, an initial engineering judgement will be made within two (2) days followed by an analytical engineering evaluation within thirty (30) days. ~e two day effort will determine the affect on system operability considaring available margins and other factors relative to system operability.

In the thirty (30) day effort, an evaluation will be performed using the same analytical technique used in the seismic analysis, or alternative methods may be used providing they are conservative. If either evaluation indicates that the system operability may be in jeopardy during a seismic event, the appli-cable Technical Specification action statement will be complied with.

In su= mary, the re-analysis effort has progressed substantially during the current outage on Unit No. 1. All modifications necessary to reduce pipe stress to less than the code allowable will be completed during the current outage. In addition, all pipe hangers will be reviewed and modified as neces-sary on all systems required for safe shutdown prior to power operation of Unit No. 1. Evaluation of remaining hangers, if any, equipment nozzle loads (644 293

Vinoim EucTaic no Powna Cowpaxy To Mr. James P. O'Reilly, Director - and equipment support loads will continue following return of the unit to power operation. This work is scheduled to be complete by February 29, 1980.

Any nonconformance identified during operation will be handled in accordance with the applicable Technical Specification. Compliance with the program will ensure that the Unit can be put back into service while the analysis continues without affecting the health and safety of the public or our operating person-nel.

We would appreciate your prompt review and response on this matter. .

D**D *D oe o S.. _a Very truly yours, 4bCf C. M. Stallings Vice President - Power Supply And Production Operations RMB/s:xv:1K4 Enclosures (3 copies) cc: 5. Victor Srello, Director Office of Inspection and Enforcement 1644 294

TABLE 1 - LIST OF AFFECTED SYSTEMS Calculation No.

(11715-MSK- ) System Location Curve Problem

  • 107B Charging and Volume Control MSVH Spread
  • 107C Quench Spray MSVH Spread
  • 107D Quench Spray MSVH Spread
  • 107E Quench Spray MSVH Spread
  • 107F Quench Spray MSVH Spread
  • 107H Charging and Volume Control MSVH Spread
  • 111D Charging and Volume Control Aux. Building Outdated ll6E Boron Recovery Aux. Building Outdated ll7A Fuel Pool Cooling Fuel Building Duplicate Period 117B Fuel Pool Cooling Fuel Building Duplicate Period 117C Fuel Pool Cooling Fuel Building Duplicate Period ll8B Component Cooling Aux. Building Outdated ll8C Component Cooling Aux. Building Outdated
  • ll8D Component Cooling Aux. Building Outdated ll8E Component Cooling Aux. Building Outdated 118F Component Cooling Aux. Building Outdated ll8G Component Cooling Aux. Building Outdated 118H Component Cooling Aux. Building Outdated
  • 118J Component Cooling Aux. Building Outdated 118K Component Cooling Aux. Building Outdated
  • ll8N Component Cooling Aux. Building Outdated 118P Component Cooling Aux. Building Outdated 1644 295

TABLE 1 - LIST OF AFFECTED SYSTEMS (Continued)

Calculation No.

(11715-MSK- ) System Location Curve Problem 118Q Component Cooling Aux. Building Outdated 118R Component Cooling Aux. Building Outdated 118S Component Cooling Aux. Building Outdated 118T Component Cooling Aux. Building Outdated 118U Component Cooling Aux. Building Outdated 118V Component Cooling Aux. Building Outdated 118W Component Cooling Aux. Building Outdated

  • 118Z Component Cooling Aux. Building Outdated 121A Componest Cooling Fuel Building Duplicate Period 121B Component Cooling Fuel Building Daplicate Period 121H Refueling Purication Aux. Building Duplicate Period 121J Containment Vacuum Aux. Building Outdated

1644 296

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CO TABLE 2 - STATUS OF PIPE STRESS RE-ANALYSIS DUE TO ARS REVISIONS AS OF DECEMBER 18, 1979 ON 33 MSK LINE FUNCTION PIPE STRESS TOTAL NO. OF NO. OF HANCER MODIFICATIONS REMARKS "C2' NO. RESULTS NO. OF SATIS- SUPPORTS REQUIRED *** "CE SUPPORTS FACTORY TO BE *Q

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  • 1078 From Lowhead SI pump (P-1B) stress 18 13 0 5 redesigns Review complete to charging pump suction sa t is fac tory
  • 107C Discharge line from quench stress 6 5 0 1 redesign Nozzle and equipment review in spray pump (P-1B) satisfactory 2 new supports to reduce progress nozzle loads
  • 107D Discharge line from quench stress 4 3 0 1 redesign Nozzle and equipment review in spray satisfactory 3 new supports to reduce progress nozzle loads
  • 107E Suction line to quench stress 2 2 0 None Review complete spray pump (P-1A) satisfactory
  • 107F Suction line to quench stress 2 0 1 1 redesign Review complete spray pump (P-1A) satisfactory 4 new supports to reduce nozzle loads
  • 10 7H Charging pumps suction stress 4 4 0 None Review complete from RWST satisfactory
  • lllD SI pump (P-1A) to charging stress 5 4 0 I support redesign Review complete pump suction satisfactory Il6E Distillate from Br-Evap stress 32** 32** O -

Equipment review in progress to overhead condenser satisfactory 32 32 0 ll7A Fuel pool cooling from stress 14 14 0 -

Equipment review pending HX to pool satisfactory 117B Fuel pool cooling pump stress 15 15 0 None Review complete suction satisfactory

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