ML19320C090
| ML19320C090 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 06/16/1980 |
| From: | Crouse R TOLEDO EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEB-79-14, NUDOCS 8007150824 | |
| Download: ML19320C090 (4) | |
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UUN 1819804 TOLEDO EDISON Docket No. 50-346 RcmanoP CnoacE License No. NPF-3 p;P7 seat (41912*,9 5221 Serial.No. 1-137 June 16, 1980 Mr. James G. Keppler Regional Director, Region III Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137
Dear Mr. Keppler:
IE Bulletin No. 79-14, dated July 2, 1979, requested that we develop and implement an inspection program to verify that the Davis-Besse Nuclear Power Station Unit I seismic analysie input of safety related piping systems conforms to the actual field conditions.
On October 19, 1979, we submitted to yc.. the results of our detailed engineering reviews for normally accessible safety related piping.
As part of that submittal, we transmitted our schedule for follow-on analytical work required under Item No. 4B of the Bulletin. On March 25, 1980, we submitted a revised schedule for the above follow-on analytical work. Attached is a description of the results of our follow-on analysis of the identified discrepancies for normally accessible safety related piping in accordance with Item No. 4B of the Bulletin.
Yours very truly, ff
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U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Division of Reactor Operation Inspection Washington, D.C.
20555 U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Division of Operation Reactors Washington, D.C.
20555 THE TOLEDO EDISON COMPANY EDISON PLAZA 300 MADISON AVENUE TOLEDO. OHIO 43652 8 0 0 715 pS M
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Dockst N2. 50-346 License No. NP F-3 Serial No. 1-137 June 16,1980 f
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Seismic Analysis For As-Built Safety Related Piping Systems Response to NRC IE Bulletin No. 79-14
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Davis-Besse Nuclear Power Station Unit 1,
I.
INTRODUCTION NRC IE Bulletin 79-14, dated July 2,1979, Revision 1, dated July 18, 1979, supplement 1, dated August 15, 1979, and Supplement 2, dated September 7, 1979, required all power reactor facility licensees to verify that the seismic analysis of safety-related piping systems applies to the actual as-built configuration of systems.
The action items identified in the Bulletin apply to all safety-related piping, 2-1/2 inches in diameter and greater, and to Seismic Category I piping, regardless of size, which
.was analyzed by computer.
The response to Item 1 of the Bulletin was submitted on August 1, 1979 (Serial No.
1-81).
A response to Item 2 of the Bulletin was submitted on October 1,1979 and October 19, 1979 (Serial Nos. 1-93 and 1-95).
The October 19, 1979 submittal also contained a partial response to Item 4 of the Bulletin.
The partial responte included the evaluation of the identified nonconformances upon system operability and an estimated date for completion of the reenalysis of the piping and supports for the normally accessible systems. On March 24, 1980 (Serial No. 1-121), a status report on the progress of the reevaluation ef fort for the accessible piping was submitted, along with the revised estimated completion date and the schedule for the submittal of the results of the reanalysis.
This report provides a partial response to Item 4 of the Bulletin, describing the results of the normally accessible piping stress reanalysis incorporating the as-built configuration of the piping and support systems.
II.
Review of Inspection and Results Inspection of all normally accessible safety-related piping as defined in the Bulletin, including both redundant trains, was performed as described in our response to Item 1 of the Bulletin. The inspectior, teams began the walkdown inspections at the site on July 30, 1979 and completed the ef fort on September 21, 1979.
Clearances for all whip restraints on accessible piping were checked during the April 1980 refueling outage and have been found to have no af fect on the stress analysis.
Preliminary evaluation and detailed engineering reviews were ca;pleted in accordance with Supplements 1 and 2 of the Bulletin.
Dincrepancies identified by both the inspection team and _the stress analyst were tabulated and shown in Attachment 1 to the October 19, 1979 submittal.
These reviews supported the preliminary evaluation that the operability of safety-related systems were unaf fected.
,n III. Description of Stress Reanalysis and Results In Attachment I to the October 19, 1979 submittal, it was anticipated that 89 of the 220 original stress calculations would require complete computer reanalysis.
An additional 98 of the 220 stress calculations were to require a simple hand calculation to ' resolve the discrepancies, and 33 calculations did not require any piping reanalysis. During the course of the reanalysis effort, a number of stress calculations were re-evaluated by the stress analyst based on the results of the calculations performed thus far and it was determined that a more extensive computer analysis would be required.
As a result, the reanalysis consisted of a total of 150 stress calculations which were completely computer reanalyzed, an additional 40 stress calculations which were resolved by means of a simple hand calculation, and 30 calculations which required no resnalysis.
None of the 190 stress calculations reanalyzed required the rerouting of any piping.
Several of the stress calculations did require the addition or relocation of a support.
However, the vast majority of the stress calculations, that were reanalyzed, only revised the calculated load transmittal to the existing supports.
IV.
Support Reanalysis and Modifications Pipe supports / anchors on the accessible safety-related piping, as defined by the bulletin, were reanalyzed for two different reasons.
The piping system stress calculation reanalysis generated revised support loads that were higher than the original design loads or the inspection identified descrepancies that existed between the design drawings and the as-built configuration.
In the first case, the supports were reanalyzed for the higher loads and, in the latter, an analysis was performed to verify the adequacy of the support.
Both of these cases combined have generated structurel reanalysis for a total of approximately 1000 supports and anchors out of the total of 2500 on the accessible piping. Of this 1000, approximately 210 supports / anchors have been identified as requiring some modification to the structure to either return it to its design condition or to modify it to accommodate its new loading condition.
These modifications can be classified into three categories.
1.
a minor revision 2.
a moderate change or addition, and 3.
a major structural rework or complete redesign of the support.
l Typically, minor revisions consist of the replacement of a missing weld or the j
addition of a small stiffener or gusset plate.
Such minor modifications comprise j
approximately 48 percent of the total number of support modifications.
The modera.*.e change or addition includes, for example, the replacement of a baseplate or the addition of a brace or kicker to the support structure. Modifications in this require the complete dismantling of the support.but wop'upport ld rather category would not affect only a portion of the structure.
Approximately 43 percent of the s modifications fall in this category.
The addition of a pipe support / anchor or the redesign or relocation of the entire support is considered a major modification.
Such major modifications consist of approximately 9 percent of the total number of support / anchor rework.
-3 o '.
In addition, some structural redesigns were due to a lack of consideration of the location of the building seismic joint in the design process.
Fourty-four (44) supports and one (1) anchor were redesigned se that the differential seismic movement of separate building arean would not have to be considered in either the piping stress calculation or in the structural analysis of the support / anchor.
V.
Schedule for Completion of Support Modifications As stated previously, approximately 210 pipe supports / anchors have been identified as requiring some modification to the structure. At this time, work packages for 67 supports / anchors have been issued providing the engineering design requit ad to make the field modification. The remainder of these design modifications asc in some stage of the engineering design cycle.
The remaining work packages are being given expeditious treatment and the projected completion date for issue of the last package is November 1,1980.
Based on this engineering schedule, implementation of the work packages in the station is expected to be complete by March 1,1981.
V1.
Schedule for Issue of As-Built Drawings The current schedule for completion of as-built drawings for piping supports /
anchors located on accessible safety-related piping is July 1,1981.
Vll. Conclusions IE Bulletin 79-14 inspection of the normally accessible piping did uncover minor discrepancies between the design and the as-built configuration of the piping and supporting systems. The affect of these discrepancies has been evaluated in detail and the preliminary conclusions made in our October 19, 1979 response are still valid, that, no deficiency has been discovered that would have adversely affected the operability of any safety-related system.