05000316/LER-1979-050-01, /01T-0:on 791227,during Field Insp,Discrepancies Noted Between as-designed & as-built Location of Seismic Support on Injection Lines from Accumulators 2 & 3.Piping Modified & Addl Hangar Installed

/01T-0:on 791227,during Field Insp,Discrepancies Noted Between as-designed & as-built Location of Seismic Support on Injection Lines from Accumulators 2 & 3.Piping Modified & Addl Hangar Installed

ML19211D254
Person / Time
Site:	Cook
Issue date:	01/11/1980
From:	Stietzel J INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19211D253	List: 05000316/LER-1979-050, Forwards LER 79-050/01T-0 05000316/LER-1979-050-01, /01T-0:on 791227,during Field Insp,Discrepancies Noted Between as-designed & as-built Location of Seismic Support on Injection Lines from Accumulators 2 & 3.Piping Modified & Addl Hangar Installed
References
LER-79-050-01T, LER-79-50-1T, NUDOCS 8001170351
Download: ML19211D254 (4)

LER-1979-050, /01T-0:on 791227,during Field Insp,Discrepancies Noted Between as-designed & as-built Location of Seismic Support on Injection Lines from Accumulators 2 & 3.Piping Modified & Addl Hangar Installed

Event date:
Report date:
3161979050R01 - NRC Website

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ATTACHMENT TO LER #79-050/0lT-0 The ensuing report supplements Mr. D. V. Shaller's letter of December 31, 1979 concerning four (4) significant non-conformances identified in Unit No. 2 during our inspection / evaluation program performed in accordance with IE Bulletin No. 79-14.

Submittal of this report fulfills the reporting requirements of Technical Speci fication 6.9.1.8.i. The required modifications have been completed and the systems retumed to a status which corresponds to the original design criteria. The corresponding piping systems in Unit No.1 were also inspected and found to have been installed as per the design requirements and, consequently, acceptable.

Accumulator Injection Lines - Loop Nos. 2 and 3 During field inspection, a discrepancy was noted between the "as designed" and the "as-built" location of a seismic support on the injection lines from accumulators 2 and 3.

Subsequent computer analysis of the "as-built" piping configurations revealed that, in the OBE and DBE conditions, the support loads were excessive.

In the unlikely case that the supports were to fail completely, the piping would be overstressed.

The pipe would be overstressed between the accumulator discharge nozzle and the first check valve downstream of the nozzle (SI-166-2 on Loop No. 2 and SI-166-3 on Loop No. 3).

Therefore there is no possible issue of breaching of RCS pressure boundary in this significant non-conformance.

Modifications of the support rystem have been completed and all stresses are within the allowablu limits of the original design criteria. The post-modification stresses are shown below.

Calculated Stress FSAR Load Combination After Modification Allowable Stress DW + Pressure + GBE 11,222 psi 19,320 psi DW + Pressure + DBE 17,255 psi 28,980 psi Thermal 18,543 psi 27,588 psi Note:

DW = Dead Weight Upper Volume Containment Spray / Piping Field inspection of the Containment Spray System (CTS) revealed a significant discrepancy between the "as designed" and the "as-built" piping configuration of one train of the CTS.

Subsequent computer

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Attachment to LER #79-050/0lT-0 Page 2 analysis of the "as-built" configuration indicated that the calculated stress levels in the piping were above the code allowable limit during the OBE and during the DBE events. The required modification which consisted of the installation of an additional hanger has been completed and the system meets original design criteria.

Calculated stresses for the modified piping systen are given below.

Calculated Stress FSAR Load Combination After Modification Allowable Stress DW + Pressure + OBE 14,110 psi 19,200 psi DW + Pressure + DBE 27,299 psi 28,800 psi Themal 13,511 psi 27,438 psi The non-conformance discussed above was identified in the upper volume CTS line which is fed from the east CTS pump.

The west-CTS train, and both redundant trains of RHR upper volume sprays, were found to be acceptable during IEB 79-14 inspections / evaluations.

Temperature Instrumentation - RC Loop No. 3 Field inspection of the sensing lines to and from the RTD manifold on loop No. 3 revealed a significant discrepancy between the "as-designed" and the "as-built" configuration of the pipirig system.

Subsequent computer analysis of the "as-Built" configuration indicated that the sensing line would have been overstressed for the OBE and DBE loading conditions. The sensing lines to the RTD manifolds are fed from the RCS hot leg (l" D nozzle at the loop connection) and the cold leg (2" 0 nozzle at the loop connection).

The return lines from the hot and cold leg manifolds feed into a comon header which is fed in turn into the crossover leg (3" 0 nozzle at the loop connection). The piping system was reanalyzed with two additional hangers installed and one existing hanger removed and all calculated stresses are within the code allowable limits.

The required modifications, installation of two additional hangers and removal of one existing hanger, have been completed and the system meets its original design criteria.

The post-modification stresses are shown below.

Calculated Stress FSAR Load Combination After Modifications Allowable Stress DW + Pressure + OBE 10,369 psi 17,200 psi DW + Pressure + DBE 17,953 psi 25,800 psi Thermal 22,705 psi 26,980 psi.

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Attachment to LER #79-050/01T-0 Page 3 Temperature Instrumentation - RC Loop No. 4 Field inspection of the RTD sensing lines on Loop No. 4 revealed a significar' discrepancy between the "as designed" and the "as-built" configurat.a of the piping system.

Subsequent computer analysis of the "at alt" configuration indicated that the piping would have been overstressed in the event of an OBE or a DBE. The piping was reanalyzed with an additional hanger and all stresses are within the code allowable limits.

The required modification, installation of an additional hanger, has been completed and the system retumed to a seismically acceptable condition.

The post-modification stresses are given below.

Calculated Stress FSAR Load Combination After Modification Allowable Stress DW + Pressure + OBE 15,468 psi 17,200 psi DW + Pressure + DBE 25,478 psi 25,800 psi Thermal 24,126 psi 26,980 psi Safety Evaluation In evaluating overall seismic design safety, it should be noted that the allowable stress values for DBE loads used in the design of the Cook Plant are below those currently given in NC3600 for ASME Class 2 piping, a type of piping comparable to that employed at the Cook Plant for Seismic Class I Systems, by approximately 33% (1.8Sh vs. 2.4S )-

h Today's design analysis of the piping systems involved would also use higher damping factors in both the building and piping which, in. turn, would have resulted in lower seismic stresses.

There are three points of importance in discussing the impact of the non-conformances on plant safety.

First the earthquake itself at the Cook Plant site is a very unlikely event (no historic record exists of an earthquake of the OBE or DBE magnitudes at the site). Simultaneous or quasi-simultaneous DBE and large LOCA events are even more unlikely.

Second, the postulated zero period seismic acceleration for which the plant is designed is typically five times bigger than the biggest earth-quake ever experienced in the surrounding areas.

Third, exceeding the code allowable values and/or the specified minimum yield limits does not automatically mean loss of system operability.

In summary, a best estimate engineering judgment supports the conviction that the found discrepancies did not endanger the health and safety of the public.

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