ML20205S203

Safety Evaluation Supporting Interim Operability of Piping Sys

ML20205S203
Person / Time
Site:	Cooper, 05000290
Issue date:	11/03/1988
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20205S200	List: ML20205S195 ML20205S203
References
NUDOCS 8811100290
Download: ML20205S203 (7)

Text

,

/[ g UNITED STATES g g NUCLEAR REGULATORY COMMISSION ,

5 e WASHINGTON, D. C 20666 s ,

• .... t ENCLOSURE SAFETY EVALUATION BY THE OFFICE OF hUCLEAR REACTOR REGULATION RELATING TO THE INTERIM OPERABil.lTY OF PIPING SYSTEMS NEBRASKAPUBLICPOWERDISTRig 4

COOPER NUCLEAR STATION DOCKET NO. 50-298

1. INTRODUCTION ,

On January 19, 1988, a flonconfornance Report, NCR No.88-019, was issued by Nebraska Public Power District (NPPD) to document that pipe support RF-H53 did not conform with the requirements of the Code of Record for the plant. This i,

was discovered when an NPPD consultant (CYGNA) was designing a 1" drain and ,

vent line connection to the 14" High Pressure Coolant Inspection (HPCI) system I piping and checked the structural adequacy of supports near the connection.

As a result of this NCR, the other supports on the HPCI system were evaluated and 17 out of 33 were identified as not meeting code allowables for the existing ,

design loadings. This nonconformance was reported by NPPD on April 28, 1988 in  ;

NCR No.88-119. In response to this NCR, the HPCI system was evaluated on an "operability" basis and c plant-wide assessment was made of all pipe supports ,

on safety-related systems. Since from the outset it was NPPD's intention to '

bring all deficient supports te full compliance with the original design basis, the purpose of the reviews were to scope the problem plant wide and to develop I 4

a basis to justify operation in t.'e interim before full corpliance is achieved. ,

Brookhaven National Laboratory (ENL) provided the NPC with technical assistance in the review of the licensee's efforts to assess the operability status of the l Cooper Station piping systems. The BNL effort included attendance at meetings with the licensee and staff on May 18, May 31, and June 24, 1988 at the staff offices in White Flint, Maryland and participation with the staff in an audit  :

of NPPD activities at the Cooper Nuclear Station (CNS) on May 23-26, 1988. The j adequacy of the overall operability evaluation was assessed from a review of >

the documents provided in the NPPD June 12 subnittal, references 1-3, and their earlier drafts. The evaluation of analysis rethodology was based on the review i of selected calculations from the operability evaluation, references 4-7. This l report provides a sunnary description of the review activity and the staff /BNL '

evaluation. l 4 ,

l l

i

)

i G311100290 631103

HEW ADOCK 050002$$

PDG

2 2.0 EVALUATION 2.1 Su w.ary Desc i tion Fo11twing the discovery of the underdesigned surport in the HPCI systtm NPPD, usig its consultant CYGNA, performed a review cf other supports in the HPCI piping system and additional nonconforming pipe supports were identified.

j Given that result, NPPD took the following actions:

• Modified the affected HPCI discharge piping system supports to l

obtain full code qualification,

• Performed an operability evaluation of the as-found HPCI discharge piping system; and, Reviewed other essential piping systems to ascertain whether the HPCI nonconferming supports were an isolated occurrence.

The evaluations of the HPCI system were more detailed than the original calcula-tions in that actual support stiffnesses and realistic thermal conditions were used. The results of these analyses indicated that the piping system was operable in accordance with the requirerents of CNS Technical Specifications in the as-found condition. This detailed evaluation is prosented in the CYGNA report Doc. No. TR-88037A-2 Peference 2, included as attachnent 1 to the NPPD l subrittal dated June 12, 1988, titled Justification for Interim Operation, Reference 1.

The review of other essential systems indicated that other nonconforming supports existad. These were all found to be associated with the original design and construction at CNS. Dele;ing from revicw systems which had under-gene design and analysis subsequent to original design, a review and evaluation of all supports on essential piping system wes undertaken (1157 supports in 11 sy s tems) . In inis effort all Class IN supports were analyzed and modified, as necessary, to enNre full code qualification. Operability of all other supports were analyzed on a sampling basis (satole of 170 from 1157) in accordance with an interir operability criteria and the results corpared with the results of th6 HPCI operability evaluations. As a result of this methodology, all existing emntial supports at CNS were found to be enveloped by the HPCI results, except certain deadweight supports and welded pipe support anchors which had unique attributes. One hundred percent of these deadweight supports and welded pipe support anchors were then reviewed leading to the redification of seventeen deadwe.ight supports and the need for modification of four welded aachors. The detailed evaluation supporting the operability status of existing essential piping system other than the HPCI system is presented in the CYGNA report Doc.

No. TR 88037A-3, Reference 3 included as Attachrent 2 to the NPPD June 12, 1988, submittal. ,

5 r

i 2.2 N, PPD,0perabilityleviewCriteria D

The CNS Code of Record for Class IN/15 piping is ANSI B31.1 "Power Piping",

1967 Edition. Piping support design is also in accordance with ANSI B31.1, ,

1967 and the AISC code allowables. In perforcing the operability assessments for essential piping and supports the allowables from the code of record were used for piping while the following operability criteria was used for supports:

Support Allowable Component Ovel Reference Structural Normal Stress - S y AISC, 7th Edition Merbers Shear .57xS y j Welds Weld .45 S T

AISC, 7th Edition with Base .47 S y 1.5 increase Vender Level D, or As listed in vendor Hardware Fr ellow catalogue  ;

i Base plates S y

AISC, 7th Edition Concrete Wedge Type: SF=2.0 NRC !E Bulletin i Anchor Bolts Shell Type: SF=2.5 79-04 and S = yield stress, S = tensile strength and Sp = safety factor applied tu  !

ancho bolt ultirate 1 ad I In the HPCI operability evaluation the operability criteria were used in +

conjunction with new assessrents of system stresses and loads. In making i' these new assessrents, efforts were made to eiinimize the conservathe:s inherent in piping system design as used in the original design. Examples of analysis refinerentsincludetheuseofCodeCaseN-411darping,themodelingofsupport stiffnesses e.9d the use of realistic rather than enve oping definitions of therral conditions, i t

In the operability review of other essential piping systems the sare acceptance  ;

c-iteria for operability was used. In that review, hcwever, the sampled I su,70rts were assessed for the loads shown on the latest revisions of the i support drawings. Specifically a load case consisting of the cortination i of deadweight, thermal and twice the seismic OBE loads were considered. [

23 LPff.ppyab,1,1,1,ty= Review Results As a result of the operability reviews NPPD concluded in their June 12, 1988 submittal that the status of the essential piping systems at CNS is:  ;

All pipe supports associated with the reactor coolant pressure  ;

boundary are fully code qualified.  !

i i

(

l

i 4

All piping supports associated with the HPCI discharge line are fully code qualified.

• Alldeadweightsupports(17)experiencingupliftduringdesignbasis seismic events have been modified to acconnodate such loads.

All we'ved pipe anchors ( O that werd overstressed will be modified prior '..s startup.

All pipe supports designed subsequent to the initial CNS design were previously analyzed and documented, resulting in a conclusion that they are not within the scope of the identified nonconforming condition.

All other essential supports have been statistically evaluated on the basis of the HPCI Pump Discharge System Operability Evaluation.

With Statisti,. certainty, the essential piping systems are considered to be operable.

Based on these findings, NPPD submitted the June 12, 1988, "Justificatien for -

Interim Operation". In that submittal, NPPD coccitted to have all nonconforming supports modified to neet the design basis prior to startup from the 1990 refueling outage. A detailed plan to ac w nlish the redifications will be provided by August 15, 1988.

At the time of the site audit, NPPD and its consultant CYGNA were actively engaged in performing the operability evaluations. At that stage the analysis procedures and acceptance criteria could be characterized as aggressive in that current era analysis practices were being coupled with liberal definitions for lotds and allowables. The audit teani focused its efforts in a review of analysis procedures, load definition, acceptance criteria and statistical sanpling methods. A description of the audit team activities and findings are presented in the audit trip report, reference 8. The significant findings and observations were discussed with NPPD at the audit exit meeting. The following is a listing of these items:

a) There are no further concerns with the HPCI sys'.em since all supports nave been breeght into code compliance, b) Concerns with CYGNA criteria were expressed by SpSS is not acceptable.

1. Coebination of two earthquake components by SRSS is not acceptable.

2. High values of dar9tr.) with original response spectra is not acceptable,.

3. Vertical floor response (2/3 of ground horizontal) is acceptable if all other pertinent FSAR costnitrents are adhered to.

4 PPCI system design temperature of 120'F is p vbably acceptable.

5. Strain criteria are not acceptable.

e O

s ,

5-c) Result of sampling of plant supports (i.e. 125 supports) does not support the CYGNA contention that all safety-related supports are satisfactory for interim operation.

d) We snderstand that all Class IN supports are going to be analyzed and brought into code corplianci before start-up.

e) Assuming that all concerns regarding pipe support operability are

• atisfied, NPDD is to develop a long-range plan to analyze each support

! for code compliance and modify where required. The plan should be I

presented before restarting the plant and should contain the methodology for performing the analysis, criteria for judging acceptability and a schedule for completing the work.

i

! The auJit team also recomended that before CNS is permitted to return to

power operation

1. All class IN supports be brought into code compliance, j 2. NPPO demonstrate that all essential system supports when evaluated for i

original design loads will meet "operability" criteria acceptable to the NRC.

i 3. The "operability" assessment should be based on "as-built" data.

4 In cases where integral attachrent loads lead to excessive local pipe f stresses NDE should be performed to assure that no damage has occurred. [

5. A long-range plan, acceptable to NRC, be developed by NPPD to brirs all i supporte into code compliance.

(

Following the site audit, NPPD and its contractor attended a eeeting at the i i staff offices on May 31, 1988. At that meeting, NPPD was advised that interir ,

j operation would only be considered af ter items 1 thru 4 of the aucit team '

reconcendation list above were complied with.

l In its June 12, 1988 submittal to the staff NPPD provided justification for interim operation of the Cooper Nuclear Station. As detailed in that submittal,

{ full code qualification of all supports associated with reactor coolant piping was ensured the operability of all essential supports were verified with a l statisticadysalidsarple,allsupportswithuniqueattributesproneto deficiencies were reviewed and a lo.1 term plan was in preparation and will t>e provided by August 15, 1988.

A review of the June 12 submittal le.' to the conclusion that the NPFu etions essentially complied with the staff's requests. In performing the rev h v however, additional concerns were raised. These were expressed as eight written questions, five requiring resolution prior to the restart and three requiring response subsequent to restart, docunented in a June 16, 1968 remorandun to the Project Manager, reference 9. The questions were addressed by the licensee curing a conference call on June 16, 1988 and at the meeting at the staff offices on June 24, 1988. Based on the licensee's responses the staff concluded:

l 1

l 6-a) the allowable stresses used to demonstrate operabilit3 are accepta'.le b) the analysis options deemed unacceptable to the staff werc not used by  ;

the licensee to demonstrate the operability of the essential systems c) all supports which had operability stress ratios greater than 1.0 were or i will be modified prior *o interim operation 3.0 CONCLOSIONS, The licensee's effora to scope, characterize and remedy the support problems  !

at the Cooper Nuclear Station have been comprehensise, timely and aggressive.  !

through these dforts the licensee has, a) restored all HpCI supports to full code compliance b) restored all supports associated with the reactor coo' ant pressure  !

boundary to full code compliance P

c) demonstrated with a statistically acceptable sarple the operability cf l 4 essential piping systems Based on these actions and the June 24, 1988 connitments by the licensee to f bring all supports to full code con:pliance prior to start-up in 1989, the restart ar.d operation of the plant in the interim period is deened acceptable.

r Principal Contributors: P. T. Kuo l P. O'Connor l

Dated: Nosember 3,1988 l

i i

I l

l

i .. ,

n .

4 REFERENCES ,

1. Letter from G. A. Trevors, NPPD to NRC dated June 12, 1988 l

2. "Operability Evaluation of the HPC1 Pump Discharge System", CYGNA report Doc. No. TR-88037A-2, Rev. 1 1

3. "Ope,* ability Evtluation of Essential Piping Systems". CYGNA report Dec.

No. TR-88037A-3, Rev.1  :

4 "NPPD Functionality Analysis of Essential Systems, Statistical Analysis",

CYGNA Cal'c No. 88037A/8/F, May 6, 1988

5. CNS hPCI, Pipe Stress, CYGNA Cal'c No. 88037A/a/F, STR-1, April 19,1988 '

, l

6. Ct:5 HPCI, Pipe Stress, CYGNA Cal'c No. 88037A/7/F, STR-4, Pay 23,1988 '

7. "Essential Systems Support Furectionality Evaluation", CYGNA Cal'c No.  ;

88027A/6/F, May 1988

(

I

8. "Trip Report - Site Audit of Safety Related Pipe Supports at Cooper l Nuclear Station, May 23-26, 1988", from P.T. Kuo to L.B. Marsh, June 8, '

1988  ;

f

, 9. Memoranda from L.B. l'arsh, Chief HE8 to W.O. Long, Project Manager,  ;

Projer.t Directorate IV, June 16,19B8 ,

, 1 i

i i

r

. i I.

t 4

i l

i

[

1 i t l

i

I L -- - - . . _ _ _. . - - - -_ - - - .