ML19270H726
| ML19270H726 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 11/26/1979 |
| From: | Andognini G BOSTON EDISON CO. |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| IEB-79-14, NUDOCS 8001020706 | |
| Download: ML19270H726 (6) | |
Text
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-7 A BCGTON EDIBON CCMPANY GENERAL OFFICES 800 GovLStom STatrT GOSTON, MASSACHUSETTS O219 9
- o. cA=6 ANooa.NI November 26, 1979 SUPERINTENOCNT NUCLEAR CPERATIONS QCPARNENT BECo. Ltr. #79-242 Mr. Boyce H. Grier, Director Office of Inspection and Enforcement Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA.
19406 License No. DPR-35 Docket No. 50-293 120 Day Response to IE Bulletin #79-14
Dear Sir:
In Section 3 of IE Bulletin #79-14, Seismic Analysis for As-Built Safety Related Systems, Boston Edison was required to complete an inspection of all normally accessible
- safety related systems and all normally inaccessible safety related systems and to submit a description of the results of this inspection within 120 days from receipt of the bulletin.
The inspections of all normally accessible safety related systems have been completed and the results of this inspection are attached. As indicated in BECo Letter #79-216 dated November 2, 1979, all normally inaccessible safety related systems will be inspected during the upcoming refueling outage scheduled to commence on January 5, 1980.
We believe this letter is responsive to your concerns.
However, should you have any further questions or comments please contact me.
Very truly yours, h
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- Normally accessible refers to those areas of the plant, excluding high radiation areas, that can be entered during reactor operation.
Attachments cc:
Director Division of Operating Reactors Office of Nuclear Reactor Regulation 1674 090 U.S. Nuclear Regulatory Commission Washington, D. C.
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a Results of Inspections to Date The inspections conducted in accordance with the requirements of IE Bulletin 79-14 have been completed with the exception of various systems that are located in areas designated as being inaccessible.
These areas include the drywell, steam tunnel, fuel pool filter room, transverse incore probe room, and the reactor water clean-up heat exchanger room.
It is BECo's intention to inspect these remaining areas during the 1980 refueling outage which will commence January 5, 1980.
To implement the requirements of IE Bulletin 79-14 two independent activities were undertaken; namely the actual walkdown and verification of the as-built conditions of the various safety related systems and the analytical ef fort re-quired to disposition any deviations found either in the field or in the original analysis.
The walkdown of the specific systems was conducted in accordance with a temporary procedure developed for the implementation of this bulletin.
This walkdown of safety related systems resulted in the issuance of forty-seven (47) deviations of which thirty-five (35) were classified as insignificant, eleven (11) were classified as minor, and one (1) was classified as significant.
To date no major deviations have been identified as a result of the walkdown effort.
(Note: For the definition of insignificant, minor, significant and major see Attachment 1).
The analytical effort in support of IE Bulletin 79-14 can be broken down into three broad categories:
- 1) evaluation of deviations discovered as a result of the field walkdown; 2) identification and evaluation of seismic analysis input document deviations; and 3) identification and evaluation of pipe support problems.
'The results of our findings to date with respect to the first category have al-ready been discussed above. The results of our findings to date with respect to the two remaining categories are as follows:
A.
Input Document Deviations Following the walkdown effort, the design documents which should have been inputs to the seismic analyses were compared with the latest seismic calcu-lations for 42 isometrics.
These isometrics represent one loop of all ac-cessible redundant systems plus those non-redundant systems that are accessible. As a result of deviations noted in this comparison and the review of walkdown deviations, 33 isometrics that had been walked down were judged to require reanalysis.
The noted deviations between input design documents and seismic calculations primarily involved missing flange weights and differences in valve weights, suppert locations and types of supports.
The reanalysis concluded that three isometrics had calculated stresses due to seismic loads slightly over code allowable stresses and one isometric had a calculated stress above the criteria for piping system operability.
(The criteria being used for piping system operability is presented in Attachment 2).
The inoperable line was in Loop "B" of the Salt Service Water System (SSWS); the overstress being due to the fact that the flange weights had not been incorporated into the original seismic cal-culation.
A review of the redundant SSWS loop showed that, while the flange weight had not been included in the original analysis, stress levels remained below code allowables.
This problem is considered to be an isolated example and is not expected to reoccur in subsequent review work associated with IE Bulletin 79-14.
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, This particular situation was reported by Licensee Event Report (LER) 79-036/01T-0 transmitted to you on October 9, 1979.
The situation was remedied by the addition of two new supports and, upon completion of this work, the system was returned to service.
B.
Pipe Supports Upon completion of the seismic reanalysis, new hanger guidance sheets are prepared and the supports are evaluated for the revised seismic loading.
The following, which is preliminary in that it is based to a large extent on unchecked calculations, summarizes the results of the pipe support review conducted to date:
Percentage of supports for which the reanalysis resulted in higher loads 60%
Percentage of pipe supports with calculated stresses above code allowables but still operable 22%
Percentage of pipe supports with calculated str<ases above the Operability Criteria 13%
It should be noted that an inoperable pipe support does not necessarily mean that the piping system itself must be declared inoperable.
In cases where this has been experienced to date further reanalyses with the sup-ports in question assumed failed have demonstrated that the system can indeed be considered to remain operable.
As a result of this ef fort and the preliminary information that we have obtained it appears that the problems with the supports may be attributed to one or more of the following:
- increase in loads due to reanalysis taking into account as-built conditions;
- errors made in the original selection of support member sizes;
- certain loads (most notably seismic loads) either neglected or inappropriately accounted for in some support designs;
- complete load information not available at the time of design.
We are continuing to investigate these potential causes and will report the results of our findings in our final report.
To date design changes have been issued to twelve supports to return them to the original design margins.
This activity will continue until all supports have been restored to these margins.
It is planned that all analyses and resulting modifications will be completed prior to the end of the 1980 refueling outage.
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. Summary The substantial effort expended to date in response to IE Bulletin 79-14 has not identified any significant reasons why Pilgrim I cannot continue to operate safely until the January 1980 refueling outage. With the exception of one deviation, the Phase I walkdown deficiencies were either insignificant or minor as summarized herein. The seismic reanalysis, which was undertaken primarily as i result of the review of input design documents, resulted in only one major problem (the SSWS) for which the original design, conditions were res tored.
within the time allowed by the technical specification and the line returned to operable status.
Although inoperable pipe supports have been identified through preliminary data no systes inoperability situations are expected to result from these deficiencies.
(On the basis of a preliminary analysis, LER #79-039/01T-0 was issued to report that the RBCCW was deemed to be inoperable. However, a more detailed analysis of the affected isometric has subsequently indicated that the system could have been considered operable even though individual supports were declared inoperable.)
It is believed that the above considerations offer adequate justification for continued operation until the January,1980 refueling outage.
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Attachment #1 Deviation Summary Sheet System Number Deviations Insignificant Minor Significant Major RBCCW 6
4 2
0 0
SSW 3
3 0
0 0
RilR 8
4 3
1 0
HPCI 4
2 2
0 0
1 0
0 0
Fuel Pool Cooling 4
3 1
0 0
RCIC 4
2 2
0 0
TBCCW 14 14 0
0 0
Head Spray 2
1 1
0 0
1 0
0 0
Insignificant - Little or no ef fect on seismic stress levels, no fix required, acceptable as is.
Minor
- Minor effect on seismic stress levels, system maintains operability, in some cases study calculation run to verify operability, fix may be recommended, seismic stress levels will not exceed code allowables.
N Significant
- Seismic stress levels above code allowabics - system A
considered operable.
Major
- Seismic stress levels above operability criteria -
system considered inoperable.
~
Pilgrim Unit No. 1 Seismic Category I Piping Systems Operability Criteria A.
Purpose The design criteria provided herein is utilized solely for determining the operability of seismic category I piping systems in response to NRC IE Billetin 79-14.
Those aspects of pipe supports which are addressed by NRC IE Bulletin 79-02 are excluded from the scope of these criteria.
B.
Piping System piping will be considered operable if the maximum calculated pipe stress does not exceed 2.4 Sh.
C.
Pipe Supports 1.
Load Combination and As-Built Drawings The design load of a pipe support shall be the worst combination of dead weight, thermal expansion load and the SSE seismic load.
The design load shall be applied to the as-built drawings to determine the operability of a pipe support.
2.
Allowable Loads of Catalog Items Allowable loads may be taken as 3 times the non NF catalog rating with the following exceptions.
(a) Allowable loads for riser clamps shall not be increased.
(b)
For rigid struts level D (i.e. faulted condition) allowable load from manufacturer's NF catalogs may be used.
(c)
The allowable load for a hydraulic snubber shall not be increased without manufacturer's written approval.
3.
Allowable Stresses for Non-Catalog Items Allowable stresses for non-catalog items will be 41000 psi (0.7 SU) in tension and 25000 psi in shear.
Load combinations excluding seismic load will not be considered.
As an exception, allowable stresses or allowable loads for buckling shall not be increased by more than 25%.
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