ML18139A299

Ro:Several Lines in Low Head & High Safety Injection Sys Were Not Analyzed for Effects of Fluid Temp Below 70 F. Review of New Nozzle Loads Showed Load on Pump Exceeded Vendor Allowable Load.Multiphase Program Proposed

ML18139A299
Person / Time
Site:	Surry, North Anna
Issue date:	06/06/1980
From:	Sylvia B VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
References
NUDOCS 8006110324
Download: ML18139A299 (18)

Text

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e VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND,VIRGINIA 23261 June 6, 1980 Mr. Harold R. Denton, Director Serial No. 510 Office of Nuclear Reactor Regulation NO/JTR:smv Attn: Mr. Robert A. Clark, Chief Docket Nos. 50-280 Operating Reactors Branch No. 3 50-281 Division of Licensing 50-338 U. S. Nuclear Regulatory Commission 50-339 Washington, D.C. 20555 License Nos. DPR-32 DPR-37 NPF-4 NPF:-7

Dear Mr. Denton:

NORTH .ANNA UNIT 1 MULTIPLE STRUCTURE ARS CONCERN Licensee Event Report LER/RO 80-034/0lT-0 submitted by the Virginia Electric and Power Company informed the NRC that several lines in the low head and high head safety injection systems installed at North Anna Unit 1 had not been analyzed for the effects of fluid temperature below 70°F. The subject lines transport water from the Refueling Water Storage Tank (RWST) to, the Reactor Coolant System cold legs during the injection phase of the Emergency Core Cooling System (ECCS) operation. Under certain conditions, these lines would be exposed to temperatures in the 40-50°F range. To verify adequate design of the pipe supports and equipment nozzles/supports in the affected piping sec-tions, the pipe stress analyses were rerun using the revised temperature conditions. Review of the new nozzle loads on the low head safety injection pumps revealed the load on pump 1-SI-P-lB exceeded the pump vendor's allowable load. In order to reduce nozzle loads to within the allowable, it was neces-sary to modify the function of some supports on the affected lines.

During discussions of this problem with the NRC staff on May 30, 1980, the NRC expressed a concern regarding the Amplified Response Spectra (ARS) curves used as a basis of analyses when a piping system is subjected to more than one ARS such as when the piping system traverses multiple building structures and contains piping supports from both structures. The original design basis selection of ARS for application to bounded piping problems was based upon a case by case evaluation process. This evaluation considered the potential sets of response spectra which might be applicable to the piping, the particu-lar geometry and support configuration of the piping itself, and the analyst's knowledge and experience of anticipated or predicted piping responses. This selection, by its nature, involved a comparison of the ARS curves themselves.

Our evaluation, during the past several days, has confirmed that this judgmen-tal selection process was applied on a wide scale, was effective, and produced conservative results when compared with the licensing requirements. We believe 8 0 0 6 1 1* 0 3;). '/

e e VIRGINIA ELECTRIC AND POWER COMPANY TO Mr. Harold R. Denton, Director that this was a reasonable and proper design basis for this era plant. Regu-latory guidance in this area was not available until 1975 and there were no FSAR questions or comments on this item following the FSAR submittal of 1973.

Our efforts since May 30 have included a compilation and examination of all pipe stress problems between buildings as well as those pipe stress problems involving piping runs between the containment internal and external struc-tures. Some stress analyses were performed by consultants other than Stone &

Webster (S&W) under contract to S&W. These problems are also part of the examination. Attachment 1 provides a list of the 68 stress problems involved.

In order to determine the effect of using an enveloped ARS curve on the piping systems and supports outside of the containment, several sample stress pro-blems on key safety-related systems were reanalyzed using an enveloped curve.

The problems were representative since at least one problem was reanalyzed for each building combination traversed by a critical system. Additionally, an evaluation was made of other key piping runs outside of containment as well as key piping runs inside of containment with supports on both the containment internal and external structures. This evaluation considered the actual ARS curves used, modes of response, frequencies of systems, and the resulting responses. The results of this evaluation and reanalysis are summarized in Attachment 2. To date, this effort has found no system, piping supports, or nozzles that are not operable.

Following our telephone discussions of June 3, 1980, and acknowledging our obligation to continue our efforts in this area, we propose a multi-phase plan to address NRC concerns. The sequence of events includes detailed engi-neering review of all piping problems subject to potential effect of more than one set of response spectra (Phase I) and calculational evaluation of these problems or of those localized problem areas, where necessary, to demonstrate suitability of design (Phase II).

Phase I The effort designated as Phase I consists of an engineering review and evaluation of all problems identified in Attachment 1 not already so evaluated (Attachment 2), thus completing all piping problems subject to the original expressed concern. This effort will commence immediately.

Piping located both inside and outside of containment will be included.

Additionally, this effort will also include an evaluation of the multiple ARS effect on small bore piping systems. This effort will then provide a comprehensive assessment of the effect of potential enveloping procedures should they be applied to the unit.

The evaluation will consider the original design basis, i.e., design basis code allowables, original support design loads and material allow-ables, vendor equipment allowables, design margin, etc., as a means to determine potential effect of enveloping criteria.

Results of the evaluation will be categorized as follows:

Category A problems consist of those which the evaluation has indicated would not be subject to increased responses beyond the capability of the piping, piping supports and equipment nozzles, and are thus not in doubt

e e VIRGINIA ELECTRIC AND POWER COMPANY TO Mr. Harold R. Denton, Director as far as adequacy of the piping or supports is concerned. Problems falling into this category will require no additional effort beyond the documented engineering evaluation activity.

Category B problems will consist of those problems where the engineering evaluation indicates that a determination cannot be made without further, more detailed evaluation and/or analysis which will be done in Phase II.

Phase I can be accomplished in approximately one month. Our anticipated completion date is July 15, 1980.

Phase II The evaluation procedure required for Phase II problems would typically consist of a computer reanalysis of the problem and detailed evaluation of pipe stresses, support loads and equipment nozzles. Support evalua-tions and possible reanalyses of existing designs would be done as well as reevaluation of the resulting equipment loads against existing vendor supplied allowables. Potentially, it may be necessary to submit revised equipment loads to vendors for a determination of acceptability.

Where necessary, the detailed evaluation procedure would be supplemented by additional engineering studies, or evaluations, which would provide justification of the original designs, Such additional studies might include, but not be limitied to, the introduction of Independent Support Methods of ARS (utilizing, for example, the NUPIPE-CDC program) in order to calculate the multi-support effect on a particular problem. In any event, the Phase II effort would justify the existing plant piping de-signs against a potentially imposed enveloping criteria for selecting amplified response spectra on an engineering basis.

At this time, it is difficult to predict the exact number of problems falling into the Phase II effort, but we believe that a minimum of two months would be required for Phase II. Therefore, our target date for completing Phase II is September 15, 1980.

If at any time during the detailed Phase I and II effort, results obtained clearly show that a design of a particular piping system or support cannot be justified against the concept of multiple structure ARS input, the system will be reviewed per Technical Specifications requirements and appropriate action taken, As the result of multiple structure ARS concerns on North Anna 1, we have reviewed the situation with regard to our other operating plants, Surry Units 1 and 2 and North Anna 2.

In the seismic analysis of Category I piping for Surry Units 1 and 2 where the piping is within one building, the ARS of the mass point above the highest elevation of the support point of the piping was used. Where the piping is supported by two separate buildings, it was analyzed for the envelope of the ARS of the appropriate elevations of the two buildings. For the containment

vrn01N1A ELECTRIC AND PowEH CoMPANY To e

Mr. Harold R. Denton, Director building, the internal structure and the containment shell were treated as two separate buildings and the enveloping procedure applied for the purpose of the response spectra analysis of piping.

On North Anna Unit 2, the same approach was used as on North Anna Unit 1. Due to the similarity of the units and the design methods used, the conclusions resulting from the evaluations completed thus far on Unit 1 apply to Unit 2.

If in the detailed Phase I and Phase II effort on Unit 1 discussed above a design of a piping system or support cannot be justified against the concept of multiple structure ARS, the system will be promptly evaluated on Unit 2 in this regard and the Unit 2 Technical Specification will be followed.

Please let us know if you have any questions or comments on the above. As we proceed, we would be happy to discuss our progress on this matter with you at any time. In any event, we plan to submit a final detailed report upon com-pletion of this effort.

Very truly yours,

Vd-~~~

B. R. Sylvia Manager - Nuclear Operations JTR/smv:C4 Attachments cc: Mr. B. J. Youngblood, Chief Licensing Branch No. 1 Division of Licensing Mr. S. A. Varga, Chief Operating Reactors Branch No. 1 Division of Licensing Mr. James P. O'Reilly, Director Office of Inspection and Enforcement Region II

ATTACHMENT 1 LIST OF MULTI-STRUCTURE PROBLEMS NORTH ANNA UNIT 1 Problem Analysis ARS No. System Fune t:lon Buildings Responsibility Curve Used 101A 101B Main Steam Main Steam Main Steam to Turbine Main Steam from "A" Containment-MSVH-Service Containment-Internal/External S&W S&W Containment Internal e

Generator lOlC Main Steam Hain Steam from "B" Containment-Internal/External S&W Internal Generator 101D Main Steam Hain Steam from "C" Containment-Internal/External S&W Internal Generator 102A Feedwater Feedwater to "A" Steam Containment-Internal/External S&W Internal Generator 102B Feedwater Feedwater to "B" Steam Containment-Internal/External S&H Internal Generator 102C Feedwater Feedwater to "C" Steam Containment-Internal/External S&W Internal Generator l02D Feedwater Fe.edwater to Generators Containment-MSVH-Service S&W Containment 103B Component Cooling Supply to "B" RHR Heat Containment-Internal/External S&W Internal Exchanger 103C Component Cooling Return from "A" RHR Heat Containment-Internal/External S&W External Exchanger l03D Component Cooling Return from "A RCP Containment-Internal/External S&W Internal

ATTACHMENT 1 (Continued)

LIST OF MULTI-STRUCTURE PROBLEMS NORTH ANNA UNIT 1 Problem Analysis ARS No. System Function Buildings Responsibility Curve Used 11 e

103E Component Cooling Re turn from "B RHR Containment"."'Internal/External S&W Internal Heat Exchanger 11 103F Component Cooling Return from C11 RCP Containment-Internal/External S&W Internal 103G Component Cooling

• Supply to "B II RCP Containment-Internal/External S&W Internal 103J Component Cooling Supply to "A" RHR Heat Containment-Internal/External S&W Internal Exchanger 103K Safety Injection Cold Leg Injection Containment-Internal/External S&W Internal 103R Safety Injection Cold Leg Injcccion Containment-Internal/External S&W Internal 103AC 103AE Safety Injection Safety Injection Hot Leg Injection Hot Leg Injection Containment-Internal/External Containment-Internal/External S&W S&W Internal Internal e

103At\.f Component Cooling Supply to "C" RCP Containment-Internal/External S&W Internal 103AN Component Cooling Supply to "A" RCP Containment-Internal/External S&W Internal 103AP Component Cooling Return from "B" RCP Containment-Internal/External S&W Internal 104A Low Head* Safety Pump Discharge to Containment-Safeguards S&W *Containment/

Injection Containment Safeguards

• Used containment horizontal and safeguards vertical

ATTACHMENT 1 (Continued)

LIST OF MULTI-STRUCTURE PROBLEMS NORTH ANNA UNIT 1 Problem Analysis ARS No. System Fune tion Buildings Responsibility Curve Used l04D Recirc. Spray Outside P:ump A Containment-Safeguards S&W Containment. -

Discharge 104F Residual Heat Pump Back. to RWST Containment-Safeguards S&W Containment Removal after an Outage 104G Quench Spray Flow to Spray Header- Containment-Safeguards S&W Containment B Pump 104H Quench Spray Flow to Spray Header- Containment-Safeguards S&W Containment A Pump lOSF Service Water Supply Recirc, Spray Containment-Internal/External S&W Internal Heat Exchanger 105G Service Water Return from Recirc. Containment-Internal/External S&W Internal 105H Service Water

. Spray Heat Exchanger Flow from the Contain- Containment-MSVH S&W Containment e

ment Recirc, Spray Heat Exchanger 105J Service Water Flow to the Containment Containment-MSVH S&W Containment Recirc, Spray Heat Exchanger 107B Safety Injection Low Head to High Head MSVH-Safeguards S&W MSVH Cross Connect

ATTACHMENT 1 (Continued)

LIST OF MULTI-STRUCTURE PROBLEMS NORTH ANNA UNIT 1 Problem Analysis ARS No. System Function Buildings Responsibility Curve Used 107C Quench Spray Pump Discharge to MSVH-Safeguards S&W MSVH Containment-B Pump l07D Quench Spray Pump Discharge to MSVH-Safeguards S&W MSVH Containment-A Pump lllB Safety Injection Low Head to High Head MSVH-Auxiliary S&W Auxiliary Cross Connect A Pump lllC Safety Injection Low Head to'High Head MSVH-Auxiliary S&W MSVH Cross Connect B Pump-RWST Suction 111N Safety Injection Hot Leg Injection Containment-Auxiliary S&W Containment lllQ Safety Injection Discharge of Boron Ir~j ect:i.on Tank Containment-Auxiliary S&W Containment e l llS Safety Injection Hot Leg Injection Containment-Auxiliary S&W Containment 114B .Quench Spray "B II Pump Discharge Containment-Internal/External S&W External to Spray He'ader.

11 ll4D Recirc. Spray D" Heat Exchanger Containment-Internal/External S&W External to Spray Hea'der 114E Quench Spray ,"A" Pump Discharge Containment-Internal/External S&W External to Spray Header

ATTACHMENT 1 (Continued)

LIST OF MULTI-STRUCTURE PROBLEMS NORTH ANNA UNIT 1 Problem Analysis ARS No. System .Function Buildings Responsibility Curve Used 114F Rec ire. Spray "A" Outs.ide Pump to Containment-Internal/External S&W Internal "D" Heat. Exchanger 114G Recirc. Spray "B" Outs.ide Pump to Containment-Internal/External S&W Internal 11 c II Heat Exchanger 114K Recirc. Spray "B" Cooler to Spray Containment-Internal/External S&W External Header 1141 Rec ire. Spray 11 A" Heat Exchanger Containment-Internal/External S&W External to Spray Header 114M Recirc, Spray rrc" Heat Exchanger Containment-Internal/External S&W External to Spray Header 118A Component Cooling Supply to RCP C Containment-Auxiliary S&W Envelope 118B Component Coolint Supply to RCP A and B Containment-J\uxil iary S&W Auxiliary e 118C Component Cooling Supply Header to Containment-Auxiliary S&W Auxiliary Containment 118D Component Cooling Return Header to Containment-Auxiliary S&W Auxiliary Containment 118E Component Cooling Return from RCP A and B Containment-Auxiliary S&W Auxiliary 118F Component Cooling Return*from RCP C Containment-Auxiliary S&W Auxiliary

ATTACHMENT 1 (Continued)

LIST OF MULTI-STRUCTURE PROBLEMS NORTH ANNA UNIT 1 Problem Analysis ARS No. System Function Buildings Responsibility Curve Used e

118G Component Cooling Return from Recirc. Containment-Auxiliary S&W Auxiliary Air Cooling 118H Component Cooling Supply to Recirc. Containment-Auxiliary S&W Auxiliary Air Cooling 118K Component Cooling Main Supply to Unit 2 Containment-Auxiliary S&W Auxiliary Containment 118N Component Cooling Mai.n Return froff1 unit 2 Containment-Auxiliary S&W Auxiliary Containment 121A Component Cooling Supply to Fuel Pool Fuel-Auxiliary S&W Fuel Heat Exchanger 121B Component Cooling Return from Fuel Pool Fuel-Auxiliary S&W Auxiliary

• neat Exchartger 121E Containment Vacuum Line to Air Ejector Containment-Auxiliary S&W Containment Used in Startup SSR-7 Seal Injection Iniection to "A"-RCP Containment-Internal/External Contract Envelope of SA-7223 Interior SSR-7 Seal Injection Injection to "B"-RCP Containment-Internal/External Contract Envelope of SA-7209 Interior SSR-7 Seal Inject ion Inject ion to "C 11 -RCP Containment-Internal/External Contract Envelope of SA-7198 "C" RCP Interior

• -_** ~

ATTACHMENT 1 (Continued)

LIST OF MULTI-STRUCTURE PROBLEMS NORTH ANNA UNIT 1 Problem Analysis ARS No. System Fune tion Buildings Responsibility Curve Used SSR-7 SA-7236 Seal lnj ection Manifold to "A", * "B" 11 11 C RCP Containment-Auxiliary Contract Containment e SSR-8 Seal Return Combined return "A"' Containment-Internal/External Contract Envelope of SA-7217 "B II' 11c1i RCP Interior SSR-8 Seal Return Combined return IIAII' Containment-Internal/External Contract Containment SA-7234 IIB'1, "C II RCP SSR-11 Charging Piping upstream of Containment-Internal/External Contract Envelope Regenerative Heat Exchanger SSR-14 Letdown Piping downstream of Containment-Internal/External Contract Envelope Regenerative Heat Exchanger

ATTACHMENT 2 SAMPLE PROBLEMS OUTSIDE CONTAINMENT STATUS AS OF JUNE 6, 1980 Problem N*o. System Status 104A Safey Injection One of six in:i.tial sample problems outside the containment.

prohlem with envelope curves.

Reraf' Preliminary review shows all pipe stresses and pipe supports and equipment loads are such that system operability is maintained.

104D Recirculation Spray One of six initial sample problems outside the containment. Reran problem with envelope curves. Preliminary review shows all pipe stresses, pipe supports and equipment are within allowables.

105J/105H Service Water Problem No. lOSJ was one of six initial sample problems outside the containment, Review of system frequencies show that the curve used in analyses envelopes the other possible curve for all system frequencies.

Therefore, no computer re~analysis with an enveloped ARS was required.

The same evaluation results apply to Problem No, lOSH. ~

107B Safety Injection One of six initial sample problems outside the containment, Reran problem with envelope curves. Preliminary review shows all pipe stresses and pipe supports loads are such that system operability is maintained, lllC Safety Injection One of six initial sample problems outside the containment, Reran problem with envelope curves. Preliminary review shows all pipe stresses and pipe supports loads are such that system operability is maintained,

• ATTACHMENT 2 (Continued)

SAMPLE PROBLEMS OUTSIDE CONTAINMENT STATUS AS OF JUNE 6, 1980 Problem No. Status lllQ Safety Injection One <?f six initial sample problems outside the containment, Reran problem with envelope curves. Preliminary review shows all pipe s t r -

and pipe supports are within allowable. ~

e

ATTACHMENT 2 (Continued)

EVALUATION RESULTS - INSIDE CONTAINMENT PROBLEMS STATUS AS OF JUNE 6, 1980 Problem No. System Status 101B Main Steam In each of the three cases, no piping frequencies fall within t h ! '

lOlC portion of the curve subject to the Hz peak effect of the external 101D structure. Two system fundamental modes exist in the area of 6.5 Hz, but these can be clearly and distinctly attributed to response of the steam generator. These steam generator modes cannot be excited by the external struc.ture,. and the effect of these modes in the vicinity of the containment pen~tration is negligible.

102A Feedwater Detailed review indicates the presence of similar system generator 102B modes as in the main steam case, which cannot be excited by the 102C external structure.* There is a single mode in the area of 9 Hz which falls into the range of possible external structure excitation. A detailed review of this mode's potential contribution indicates that predicted responses due to a postulated envelope situation would be minimal, perhaps on the order of a one to five percent increased iiA seismic response. ...,

103K Safety Injection The system frequencies were reviewed and found to be of values such that the curve used envelopes the other possible curve for the fre-quencies in question.

105G Service Water The system fundamental frequency is greater than 10 Hz. Therefore, the curve used envelopes the other possibl~ curve.

ATTACHMENT 2 (Continued)

EVALUATION RESULTS - INSIDE CONTAINMENT PROBLEMS STATUS AS OF JUNE 6, 1980 Problem No. Status 114B Quench Spray Several modes could be potentially affected by the interior structure peak but the modal responses were in areas of the pipe system tha"A could only be excited by the external structure. ~

ll4D Recirc. Spray The system frequencies were reviewed and found to be of values such that the curve used envelopes the other possible curve for the fre-quencies in question.

114E Quench Spray A review of the modes of the problem indicated that only 1 mode occurred with significant increased response potential for the curve not used, Local load increases are expected but function will be maintained. The vertical curve used envelopes the other possible curve, Relatively low stresses exist in the area of modal response, 114K Recirc, Spray The system frequencies were reviewed and found to be of values sucJ;ja.

that the curve used envelopes the other possible curve for the freJIJIIII' quencies in question, 1141 Recirc. Spray The system frequencies were reviewed and found to be of values such that the curve used envelopes the other possible curve for the fre-quencies in questions, 114M Rec ire, Spray The system frequencies were reviewed and found to be of values such that the. curve used envelopes the other possible curve for the fre-quencies in question,

ATTACHMENT 2 (Continued)

EVALUATION RESULTS - LINES OUTSIDE CONTAINMENT STATUS AS OF JUNE 6, 1980 Problem No. System Status 101A Main Steam The three main steam leads are treated individually for seismic anal~

sis and as a joint problem for thermal expansion and for combined loads analysis. The leads are very similar but not exactly identified in geometry and in location of pipe supports. Reactor containment external

• ARS were used in the analysis. Review of one of the three leads shows that 2 modes fall into areas subject to increased accele-ration due to MSVH peaks and loads will therefore increase. Prelimi-nary review of the potential increases indicates that the system will maintain operability. Review of the two remaining leads is continuing.

102D Feedwater The three feedwater leads outside of containment are treated indepen-dent for seismic analysis and as a join~ problem for thermal expansion for combined loads analysis, The leads are very similar but not exactly identical in geometry and in location of pipe supports. Reac-tor containment external ARS were used in the analysis. Prel imina7A review indicates that the load increases_ are expected but the syste!91!'

is complex and the effect of such increases cannot be reasonably determined. Priority effort is underway to complete this more detailed review.

I 104F Residual Heat Removal The containment building external structure ARS was used for analysis.

The responses of the modes which are not enveloped by that ARS are not expected to increase sufficiently so - as to significantly increase total response. Changes in support loads*and stresses are expected to be minimal,

ATTACHMENT 2 (Continued)

EVALUATION RESULTS - LINES OUTSIDE CONTAINMENT STATUS AS OF JUNE 6, 1980 Problem No. System Status 104G Quench Spray The containment external structure ARS was used for the analysis.

Although some modal response could increase as a result of the appli~

cation of enveloped ARS, the low level of response in the presen,w analysis indicates that total support loading would not increase significantly and that stress levels would remain acceptable.

104H Quench Spray The ARS used for the analysis is for containment external structure.

This problem was rerun, using an ARS envelope of the containment and Safeguard building. As a result, the maximum stress increased mini-mally while the increase in resultant support loads was well within acceptable margins, 107C Quench Spray All supports except the last anchor on the Safeguard wall are connected to the Main Steam Valve House, The present analysis uses the Main Steam Valve House ARS, but review of potential changes due to use of 11n.envl;!loped Cl.!rve i.nd:l,c;,;it~s tha,t expe.<;ted changes a,re minimal, e

l07D Quench Spray All supports except the last anchor on the Safeguard wall are connected to the Main Steam Valve House. The present anlaysis uses the Main Steam Valve House ARS, but review of potential changes due to use of an enveloped curve indicates that expected changes are minimal,

ATTACHMENT 2 (Continued)

EVALUATION RESULTS - LINES OUTSIDE CONTAINMENT STATUS AS OF JUNE 6, 1980 Problem No. Status lllB Safety Injection Both the Valve House and the Auxiliary building ARS were separatel, used for analysis. The results from the more severe Valve House curve were used for all supports except for two located at the opposite end of the system away from the Valve House anchor. Since only the anchor is located in the Valve House, the system response is controlled by the Auxiliary building. While further evaluation of a possible curve enveloping will be required, it is expected that supports would be within the functional range and stresses will be within faulted limits-.

111N Safety Injection The system is .bounded on one end by an anchor attached to the Reactor Containment external structure and on the other end by a containment penetrRtion. Since there are no other supports and since the contain-ment external structure ARS was used in the analysis, no enveloping of ARS is required, e

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