05000338/LER-1981-035, Updated LER 81-035/03X-1:on 810429 & 0519,pipe Support Arrangements & Unacceptable Pipe Hangers Were Identified During Evaluations.Caused by New & Larger Accelerations Imposed on Pipe Sys.Affected Hangers Modified

Updated LER 81-035/03X-1:on 810429 & 0519,pipe Support Arrangements & Unacceptable Pipe Hangers Were Identified During Evaluations.Caused by New & Larger Accelerations Imposed on Pipe Sys.Affected Hangers Modified

ML20009G029
Person / Time
Site:	North Anna
Issue date:	07/22/1981
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20009G022	List:
References
LER-81-035-03X-01, LER-81-35-3X-1, NUDOCS 8108030257
Download: ML20009G029 (5)

LER-1981-035, Updated LER 81-035/03X-1:on 810429 & 0519,pipe Support Arrangements & Unacceptable Pipe Hangers Were Identified During Evaluations.Caused by New & Larger Accelerations Imposed on Pipe Sys.Affected Hangers Modified

Event date:
Report date:
3381981035R00 - NRC Website

text

UPDATE REPORT - PREVIOUS REPORT DATE 05-28-81 U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT CONTROL BLOCK / / / / / / / (1)

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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DOCKET NUMBER EVENT DATE REPORT DATE EVFhT DESCRIPTION AND PROBABLE CONSEQUENCES (10)

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/_0n April 29, 1981, the ongoing multiple structure ARS evaluation effort identi- /

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/ fied 7 pipe support arrangements in various Unit 1 systems which did not meet the/

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/ the operability criteria due_to overstressed conditions. On May 19, 1981, a total /

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/ of 13 unacceptable pipe hanters on Unit 2 were identified.

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/ sis indicates that the pipe stress of a Unit I atmospheric steam dump line ex-

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/ ceeds FSAR allowables. This additional analysis does not change the original d,e-/

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/ sign basis selection of ARS for application to bounded piping problems.

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SYSTEM

CAUSE

CAUSE COMP.

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ACTION FUTURE EFFECT SHUTDOWN ATTACHMENT NPRD-4 PRIME COMP. COMPONENT TAKEN ACTION ON PLANT METHOD HOURS SUBMITTED FORM SUB. SUPPLIER UANUFACTURER

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/ The requested seismic stress reanalysis of piping sections spanning multiple

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NAME OF PREPARER W. R. CARTWRIGHT PHONE (703) 894-5151

Virginia Electric and Power Company North Anna Power Station, Unit #1

Attachment:

Page 1 of 4 Docket No. 50-338 Report No. LER 81-035/03X-1

Description of Event

On April 29, 1981, Vepco was informed by Stone & Webster that the angoing multiple structure amplified response spectrum (ARS) evaluation requested by the NRC had identified 7 pipe support arrangements on Unit I which did not meet operability critieria due to overstressed conditions.

On May 19, 1981, 13 pipe supports on Unit 2 were reported as not meeting the required criteria.

In addition, preliminary reanalysis indicates pipe stress on Unit 1 main steam atmospheric dump line 6"-SHP-39-601-Q2 to be over FSAR allowables. The Station was informed of this condition on June 23, 1981. This event is reportable pursuant to T.S. 6.9.1.9.b.

The hangers involved are as follows:

UNIT 1 Hanger No.

Location Unacceptable Condition WFPD-H-1 Main Feedwater Header 26"-WFPD-6-901-Q2 Weld overstressed I

WFPD-H-2 Main Feedwater Header 26"-WFPD-6-901-Q2 Weld overstressed RS-H-206A and B "C" Recirculation Spray Cooler Snubbers stressed over Discharge Line 10"-RS-11-153A-Q2 rated allowable RS-H-208A and B "A" Recirculation Spray Cooler Snubbers stressed over Discharge Line 10"-RS-3-153A-Q2 rated allowable QS-H-107 "B" Quench Spray Header Supply Snubber stressed over Line 8"-QS-39-153A-Q2 rated allowable QS-H-209A and B "A" Quench Spray Header Supply Snubbers stressed over Line 8"-QS-37-153A-Q2 rated allowable l

SHP-H-224 "A" Main Steamline 32"-SHP-57-601 Snubber stressed over I

rated allowable i

UNIT 2 l

Hanger No.

Location Unacceptable Condition WFPD-H-213 "C" Steam Generator Feedwater Brace plate Line 16"-WFPD-409-601 overstressed WFPD-H-214 "B" Steam Generator Feedwater Brace plate Line 16"-WFPD-413-601 overstressed i

WFPD-H 215 "A" Steam Generator Feedwater Brace plate l

Line 16"-WFPD-417-601 overstressed WGCB-H-151 "C" Steam Generator Blowdown Hanger exceeds normal l

Line 3"-WGCB-403-601-Q3 upset stress allowable

Attachment:

Page 2 of 4 UNIT 2 (cont)

Hanger No.

Location Unacceptable Condition WGCB-H-513 "A" Steam Generator Blowdown Hanger exceeds normal Line 3"-WGCB-414-601-Q2 upset stress allowable WGCB-H-514 "C" Steam Generator Blowdown Hanger exceeds normal Line 3"-WGCB-416-601-Q2 upset stress allowable WGCB-H-515 "C" Steam Generator Blowdown Hanger exceeds normal Line 3"-WGCB-403-601-Q3 upset stress allowable WGCB-H-516 "B" Steam Generator Blowdown Hanger exceeds normal Line 3"-WGCB-415-601-Q2 upset stress allowable WGCB-H-517 "B" Steam Generator Blowdown Hanger exceeds normal Line 3"-WGCB-402-601-Q3 upset stress allowable WGCB-H-518 "A" Steam Generator Blowdown Hanger exceeds normal Line 3"-WGCB-414-601-Q2 upset sp 'an allowable WGCB-H-608 "C" Steam Generator Blowdown Hanger exceeds normal Line 3"-WGCB-403-601-Q3 upset stress allowable SI-H-56A High Head Safety Injection Weld size and bolt torque Lines 3"-SI-417-1502-Q1 and under required values 3"-SI-457-1502-Q1 for points 1 and 2 RP-H-4 Refueling Purification Pump Weld overstressed Discharge Header 6"-RP-41-152-Q3 l

Probable Consequences of Occurrence The additional analysis performed, due to the NRC request, does not change the original design basis selection of ARS for application to

(

bounded piping problems.

As a result, the health and safety of the general public were not affected by the results of the review. The consequences are also minimized by the fact that necessary pipe support modifications were implemented during unit shutdown and satisfactorily completed prior to startup and all atmospheric steam dump line pipe stress is well below faulted allowable limits which provide sufficient justification for interim operation.

i l

Cause of Event

l The seismic stress reanalysis of piping sections spanning multiple l

building structures, by considering the appropriate accelerations from l

each of the independent structures to which the piping supports are attached, imposed new and larger accelerations on the pipe systems resulting in the overstressed conditions. The overstress on the atmospheric steam dump j

piping was caused by a support being coded in at a valve during the initial stress analysis instead of 18 inches away from the valve which

Attachment:

Page 3 of 4 is as close to the valve as it could be placed and consequently the correct as-built condition.

Immediate Corrective Action

Each of the overstressed hangers were modified as follows by Design Change 80-S46 to meet the new operability criteria:

Hanger No.

Modification WFPD-H-1 Added stiffener plates to the support WFPD-H-2 Added stiffener plates to the support RS-H-206A and B Replaced existing snubbers with larger snubbers RS-H-208A and B Replaced existing snubbers with larger snubbers QS-H-207 Replaced existing snubber with larger snubbers QS-H-209A and B Replaced existing snubbers with larger snubbers SHP-H-224 Added an additional snubber to the support and replaced the existing snubber WFPD-H-213 Changed clamps on snubber and added stiffener plates to the support WFPD-H-214 Changed clamps on snubber and added stiffener plates to the support WFPD-H-215 Changed clamps on snubber and added stiffener plates to the support WGCB-H-161 Removed portion of pipe trunnion from the support WGCB-H-513 Added sway strut to the support WGCB-H-514 Added sway strut to the support WGCB-H-515 Added sway strut to the support WGCB-H-516 Added sway strut to the support WGCB-H-517 Added sway strut to the support WGCB-H-518 Added sway strut to the support WGCB-H-608 Added a plate to the support

Attachment:

Page 4 of 4 Hanger No.

Modification SI-H-56A Added special clamp anchor to the support and changed welds RP-H-4 Added tube steel stiffener plates and shim plates to the support Scheduled Corrective Action iD,e support modifications will be made such that all atmospheric steam dump piping and supports meet FSAR allowables.

Stone & Webster is presently analyzing the as-built piping and designing the necessary support modifications.

Actions Taken to Prevent Recurrence No further actions required.

a Generic Implications Potential generic implications exist on plants requiring multiple structure ARS evaluations or any other analysis which uses more severe seismic conditions as a criterion.