ML20195G864
| ML20195G864 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/08/1987 |
| From: | Tai M NCT ENGINEERING, INC. |
| To: | |
| Shared Package | |
| ML20127A683 | List:
|
| References | |
| NUDOCS 8712210071 | |
| Download: ML20195G864 (7) | |
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SEQUOYAH NUCLEAR PCWER PLANT, UNITS 1 & 2 TECHNICAL EVALUATION REPORT FOR EMPLOYEE CONCERNS ELEMENT REPCRT 220.11(B), PEVIS. ION 2 "SUPPORT DESIGN GENERAL Temperature variation Consideration"
SUBJECT:
This report summari:es the NRC audit of TVA's corrective action of empicyee cencern regarding TVA's failure to consider temperature variations in pipe / hanger calculations for thermal stresses.
f By:
Moha:r. mad K.
Tai-Consultant NCT Engineer 1ng, Inc.
Date:
December 6, 1987 i
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NCT ENGINEERING, INC.
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.g SEQUOYAH liUCLEAR POWER PLAliTS Ut!IT 1 & 2 TECHNICAL E //.%UATICli REPORT FOR EMPLOYEE CCliCERNS ELEMENT REPS T 720.11 (B) REV. 2 "SUPPORT DESIGli GEllERAL" I.
SUBJECT CATEGORY:
Engineering (20000)
SUBCATEGCRY:
Support Design General (22000)
ELEMENT !!O:
Temperature Variation Consideration.
(22011)
CCNCERNS:
I11-85-103-002 IU-85-103-002 "In several cases, temperature variations were not considered in pipe / hanger calculations for thermal stress.
No further I
information available in file.
Construction department concern."
II.
SUMMARY
OF ISSUES The ECTG report interpreted the employee. concern and came up with the j
I following two issues:
i 1.
The expansion of structural members restrained between two rigid i
points (such *s concrete surfaces) will cause additional loading j
on members.
i 2.
The thormal expansion of pipe will impose loads on the pipe supp,rts.
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2 III.
EVALUATION
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The -
first issue involves the thermal expansion of restrained structural members.
The ECTG report discusses the SCN design criteria for thermal expansion of structural members.
According to the ECTG report, the design criteria (SQN-DC-V-1.3.3.1, Rev.
4) for reinforced
- concrete, structural steel and miscellaneous
- steel, requires consideration of thermal loads for Category I
structure design for the following conditions:
(i)
Normal plant operation and shutdown (ii)
Postulated high energy pipe break accident However, the SCN pipe support design criteria reviewed by ECTG (SCN-DC-V-24.1, Rev.
0) did not require consideration of these loads for pipe support design.
Therefore, the ECiG report. concludes that SCN pipe supports with strudtural members restrained between.two rigid points have not been designed to account for temperature variations.
The ETCG report also references section NF of the 1983 edition of the ASME
',de which states that the evaluation of thermal -stresses in supports is not required.
Although the pipe support design criteria did not require evaluation of thermal temperature stresses in
- supports, TVA did initiate action to evaluate structural members restrained rigidly between two points.
According to the ECTG
- report, structural members rigidly restrained between two points will result in considerable thermal loading if the temperature variation is significant and the review of such supports in high temperature zones would be prudunt.
TVA has subsequently issued a revised pipe support design criteria SCN-DC-V-24.2 as a part of the pipe support calculations regeneration effort.
This design critaria requires evaluation of environmental thermal effects for structures spanning between
- welds, floors, and
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columns.
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The ECTG report discussed TVA's corrective action. plan which would identify and evaluate supports with steel structures having design features that' restrain' thermal growth.
TVA's implementation of this' corrective action was reviewed during an.NRC audit of the' employee concerns.
This corrective-action implementation by TVA involved the review of four general categories of supports.
These four. categories are discussed in the following paragraphs.
Succorts with Gusset elates TVA's review of supports with gusset plates was based on a qualitative evaluation.
According to TVA, gusset plates are relatively small in dimensions and the thermal loads are self limiting in
- nature, therefore t;.ase gusset plates were determined to have no significant impact on the integrity of supports.
Based on the short lengths of these gusset
- plates, it is agreed that the thermal deflections are small.
In addition, SCM-DC-V-1.3.3.1 which requires evaluation of thermal loads on structural members allows justification based on ductility considerations.
Therefore, TVA's evaluation of the gusset 4
plates is considered acceptable, j
Suroort s with cenet'rator sleeves:
4 These were addressed in TVA calculations SCR CES 8510 (Load Review for ECN L5851, Rim No. B25870903 812) and SCG1S159, sheet 12.1.
These calcula'tions present a
qualitative justification similar to the.one provided for supports with Gusset plates.
These support members are relativ.ely short in length and the same considerations discussed for gusset plates also apply.
Therefore, TVA's evaluation of supports with penetration sleeves is censidered adequate.
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s Sucrorts with header beams :
TVA evaluated these supports and determined that support 2H3-255 did not qualify the restart criteria without modifications to it.
- However, instead of modifying the support, a "failure analysis" was performed where 2H3-255 was assumed non-existent (failed) and the load redistributed to other supports in the system.
Re-evaluation of the remaining supports resulted in the failure of two supports 2H3-331 and 2H3-341 to meet the restart criteria.
TVA performed an additional detailed analysis of these supports to demonstrate that the restart design criteria were met.
This evaluation was considered acceptable for restart.
During the review of these calculations, minor issue was identified.
In the calculations, to determine thermal expansion
- loads, TVA has used thermal expansion coef ficient, oc, value at 170 instead of the actual temperatures which in some cases were substantial 2y higher.
- However, this error would be compensated to a large extent by a similar error of using
'E' value at the same temperature as 'cc',
thus resulting in essentially the same loads, and is not considered to have a significant impact on the calculations.
Succert s between walls er columns :
TVA's p,reliminary evaluation of these supperts found that eight (8) supports needed further detailed evaluation.
Based on the detailed evaluation, three supports, 2-HIM-104, 2-H21-5, and 2-H34-323 were modified and support 2-H34-500 was fcund to be acceptable.
During the review of this element report, the remaining four supports 2-HIM-101, 2-HIM-102, 2-HIM-103, and 2-H36-111 were still being re-evaluated and calculations were not available for review.
Based on the review of calculations, TVA's evaluation of the four completed supports was considered acceptable. <
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During the review of the ~ issue of restrained thermal expansion of pipe support structural members, it was identified that ECTG had a concern with the field modifications performed as part of TVA's corrective action.
Resolution of this concern was nOt complete at the time of the review of this element report.
It is recemmended that the final resolution of the ECTG concern be reviewed.
The second issue addressed by the ECTG report involves the loads on supports due to piping thermal expansion.
The ECTG report discusses the SCN procedures and criteria for piping stress analysis and pipe support design.
These criteria require the evaluation of piping thermal loads.
Based on the review of TVA's criteria for rigorous piping analysis and pipe support
- design, TVA has adequate ' design provisions for the consideration of piping thermal loads.
The implementation of these design provisions is further discussed in the evaluation of element report 213.1.
Also, there was a valid concern
. with TVA's evaluation of piping thermal loads for alternate analysis.
The alternate analysis criteria for thermal loads is the subject of a separate NRC evaluation and 15 additionally addressed in the review of element report 218.4 IV.
CCNCLUSICN Based on the review of the ECTG report and the review of calculations recently performed, TVA's technical resolution of the issue of restrained thermal growth for pipe support structural members was considered adequate.
It is recommended that the resolution of the ECTG concern with the implementation of field modifications be reviewed whe,n this issue is resolved.
It is further recommended to perform additional review of the four supports, 2-HIM-101, 2-HIM-102, 2-HIM-103, and 2-H36-111, when the calculations are ccmplete.
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Based on the review of TVA's design criteria documents, piping-thermal e.xpansion loads were adequately addressed by the design criteria for the rigorously analy:ed piping system.
Additional discussion on the implementation of this criteria is contained in the evaluation of element report 218.1.
The d9 sign criteria for alternately analy:ed piping systems is discussed in the evaluation of element report'218.4 3
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