ML19246C440
| ML19246C440 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 05/25/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19246C438 | List: |
| References | |
| SER-790525, NUDOCS 7907240627 | |
| Download: ML19246C440 (3) | |
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PILGRIM NUCLEAR POWER STATION UNIT 1 REVIEW 0F PIPING REANALYSIS PER I&E BULLETIN 79-07 SAFETY EVALUATION REPORT ENGINEERING BRANCH DIVISION OF OPERATING REACTORS INTRODUCTION /B ACKGROUND In their April 24, 1979 response to I&E Bulletin 79-07 Boston Edison Company (BECO) identified that the recirculation ar.d main steam piping had been analyzed by GE using a computer code that combined directional seismic responses by algebraic summation. BECo has supplied supplemental information on this subject at a May 18, 1979, meeting with the NRC staff and in letters dated May 23 and 25, 1979.
DISCUSSION The affected systems identified by the licensee are:
Recirculation Main Steam High Pressure Coolant Injection Reactor Core Isolation Cooling Reactor Water Cleanup Residual Heat Removal The last four systems listed above are branch lines off either the recirculation or main steam lines.
BECo has stated that a reanalysis of all affected piping in the "as-built" con-dition, has been completed and the results show all piping stresses remain below their allowable values, as specified in the Pilgrim 1 FSAR. Additionally, all loads on attached equipment (nozzle loads) are acceptable. Upon completion of modifications to some snubbers, including snubber replacement and attachment weld and support steel modification, all snubbers attached to safety related piping or equipment in the plant will be " operable" and within FSAR criteria.
These modifications will be completed prior to return to power.
The recirculation and attached lines were reanalyzed by GE and the main steam lines by Teledyne. The responses from two directions, the most disadvantageous combination of one horizontal with the vertical, were combined by the absolute sum.
The licensee's response to I&E Bulletin 79-04 states that no VELAN swing check valves are in any of the affected piping.
,7907240 6 7 362 249 I&E Bulletin 79-02 was addressed when modifications to a support were necessary.
The licensee has stated that the reanalysis has no effect on pipe break criteria since all affected piping is irside the drywell and break locations were not postulated based on stress levels.
EVALUATION The reanalysis technique employed was a lumped mass response spectra modal analysis. This dynamic analysis procedure is an acceptable method. The absolute combina. ion of responses in two directions is also acceptable to the staff.
Once the support modifications are complete, the affected piping stresses, attached equipment loads, and support designs will al be in accordanc '
with FSAR criteria and acceptable to the staff.
We find the licensee's responses concerning I&E Bulletins 79-02 and 79-04 acceptable. The reanalysis has no effect on Pilgrim 1 pipe break criteria committed to in the FSAR.
The staff scill has some concern as to whether the reanalyses effort reflects the true as-built conditions in the plant. However, BECo will complete a walk-down of the recirculation piping, prior to startup, to verify that the as-built condition has' indeed been utilized. Additionally, the licensee has committed to a field verification of the main steam lines at the earliest oppo rtuni ty.
We find this commitment acceptable.
CODE VERIFICATION The licensee has indicated that the following computer programs were used in the reanalysis of this plant:
PISYS-General Electric Company STARDYNE-Teledyne Eng. Services (TES)
GE has stated that the code PISYS combines the responses due to seismic multi-axial excitation by absolute summation; the modal responses due to each excit-ation are combined by methods as specified in Regulatory Guide 1.92.
A Fortran listing of the dynamic response calculation section of PISYS has been sut,mitted by GE and these statements have been verified and confirmed. GE is also presently solving a set of NRC generated benchmark problems as part of the code verification e f fort.
TES has stated that the code STARDYNE is being used to generate responses to individual seismic uniaxial excitation.
These responses are then combined exter-nally (manually) by absolute summation; the modal response due to each excitation are combined (internally) by methods as specified in Regulatory Guide 1.92.
Since 362 oc-ou
. the combination is performed externally TES has not been requested to submit the necessary Fortran listing of STARDYNE; they have, however, described their method of combination and have committed to solve a set of NRC generated benchmark problems as part of the code or technique verification effort. We find this com.nittment acceptable.
In addition to satisfying the code verification requirements, the licensee has also agreed to provide the NRC two problems for confirmatory analysis, namely:
GE - recirculation piping problem TES - main steam piping problem These confirmatory problems will be solved indepentently by the Brookhaven National Lab. as consultant to the NRC. The models submitted for these piping problems will be confirmed by the licensee as corresponding to the "as-built" condition. We find these committments acceptable.
CONCLUSION Based on the discussion and evaluation presented above, we conclude that the requirements set forth in I&E Bulletin 79-09 are adequately satisfied to allow resumption of operation upon ;)mpletion of the modifications identified in Attachment B to your May 23, id79, letter and as-built verification on the recirculation sysem and main steam line D.
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