ML20195G837
| ML20195G837 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/06/1987 |
| From: | Tai M NCT ENGINEERING, INC. |
| To: | |
| Shared Package | |
| ML20127A683 | List:
|
| References | |
| NUDOCS 8712210056 | |
| Download: ML20195G837 (10) | |
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l SEQUOYAH NUCLEAR PCWER PLANT, UNITS 1& 2 TECIINICAL EVALUATICN REPORT FOR EMPLOYEE CCNCERNS ELEMENT P2 PORT 218. 4 (3), REVISICN 2 "PIPE STRESS CALCULATICNS Wide Spread Deficiencies Within Pipe Stress Calculations" 1
SUBJECT:
This report sumarizes the NRC audit of TVA' s corrective actions ragarding the concern about wide spread deficiencies in the alternately analyzed piping at SCN.
By:
Mohamad K.
Tai Consultant NCT Engineering, Inc.
Date:
December 6, 1997 e
NCT ENGINEERING, INC.
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e' .A_-.+ 4>.a.. .As SEQUOYAH NUCLEAR POWER PLANTS UNIT 1 & 2 TECHNICAL EVALUATION REPORT FCR. EMPLOYEE CONCERNS ELEMENT REPORT 213.4 (B) PIV. 2 ~ "PIPE STRESS CALCULATIONS" I. SUBJECT CATEGORY: Engineering (20000) SUBCATEGORY: Pipe Stress Calculations (21800) ELEMENT NO: Wide Spread Deliciencies Within Pipe Stress Calculations (21804) l CONCEPalS : SCN-86-001-01 j SON-86-002-01 1 SCN-86-001-01 1 "During the exit interview, the CI stated that there is an ' Alternate j Criteria NCR for the inadequacy of alternate piping. Any concerns relating to any alternate piping are put under the NCR. The concern is that this is a ' catch-all' and individual items could go unresolved beyond startup." SCN-86-002-01 "During the exit interview the CI stated that alternate piping analysis does not get as specific as it s hould '. Instances where this piping is not qualified gets put into a ' catch-all' NCR. This item was. addressed and corrected at Watts Bar." s,,_-
~ II.
SUMMARY
OF ISSU2S The Element Report has translated'the concerns into a broad issue as follows: Alternate analysis is not as detailed as it should be. Although a Non-Conformance Report (NCR) was created to resolve all discrepancies associated with this analysis
- method, some discrepancies could remain unresolved beyond startup.
III. EVALUATICN For the Sequoyah plant, TVA has generally performed piping designs by two types of analysis: Rigorous Analysis and Alternate Analysis. Rigorous Analysis was performed by a computer code analysis. Alternate Analysis was performed by a simplified handbook method for locating and si:ing pipe supports. The ECTG report addresses TVA's alternate analysis criteria and the implementation of this criteria. A "J ordi.v, to the ECTG
- report, TVA performed a
review of the a...r. ate'.y analyzed piping designs in 1982. This review resulted in non-conformance reports (NCR, SCNSWP8215, Rev. O and !"CR,. SCNSWP8222, Rev. 0). This review had identified deficiencies in the SCN Alternate Analysis piping designs and design documentation. These deficiencies were listed as follows by the ECTG report. 1. The Alternate Analysis criteria reports may not have considered seism'id response spectra for all buildings for which they may have been used. 2. Alternate Analysis piping may not have been supported to take the loads that may be imposed by adjoining deadweight supported piping which is not seismically restrained. - -
4: P s W L 3. Flanges have not been evaluated for bolt stress. 4. _ Equipment no::le loads have not always been evaluated. 5. Valves and other' concentrated weights may not have always been supported in accordance with the design criteria. 6. Axial supports may not have always been located according to the design criteria. 7. Documentation of design data CEB 74-2 has not been verified.~ 8. Stress intensification factors may not have been considered in alternate criteria CEB 80-5. 9. Revision 2 Addenda to CEB 80-5 is not in MIDS (MEDS is an acronym for a TVA document control system). 10. Support loads in CEB 80-5 are significantly higher than in CEB 76-5. 11. The rm: 1 expan'sion and anchor movement may sometimes have been ignored. 12. Ng documentation was found to support CEB 75-9 (SCN-and >GN-Design Data for Support of Category I stainless Steel and Copper Tubing). 13. Docum~entation of analyses in many cases has not been completed in enough detail to document the scope and basic assumptions used. I l 14. The general technic,al errors identified during the WBN review and-I documented in NCR WBNSWP8231 were also generally evident on SON analyses that used CEB 7 6-5. 1. 1
15. Some analyses have not been reviewed and kept current for support and piping rerisions that occurred subsequent to the original design. A two-phase program was instituted by TVA to resolve the above issues. This program was reviewed by the NRC and is a subject of the separat.e evaluation. Although TVA's alternate analysis program has been audited and reviewed previously by the
- NRC, the previous NRC evaluation did not specifically address all deficiencies cited above.
This NRC evaluation reviewed the deficiencies addressed in TVA's Phase I program. These deficiencies included issues 2, 5, 6, and 11. In the Phase II
- program, TVA has committed to review all reismic Category I alternate analysis piping systems to demonstrate that the licensing criteria has been met (reference SCN-AA-001).
The Phase II program will be performed af ter the LCN re-start. - According to
- TVA, the detail of the Phase II program implementation has not been developed yet.
This evaluation will address the specific deficiencies identified above that were not directly addressed by the previous NRC review. ITEM NO. 1: UNCCNSERVATIVE SEISMIC RESPCNSE SPECTRA The ECTG report references the results of the WBN alternate analysis p rogram,. which identified the specific design deficiencies that were shown to be significant problems. These deficiencies were evaluated during the Phase I program at SON and are reviewed in a separate URC report. TVA will verify the design criteria used for alternate ' n' the Phase II program. Based on review of the design analysis i documents CEB 76-5 and CEB 80-5 and the results of the NEN review, it 9 is concluded that the criteria is suf ficiently conservative to juctify final verification in the Phase II program. _4
ITEM NO. 3: FLANGE BOLT STRESS EVALUATIONS ECTG report states that the SQN piping design is based on USAS B31.1.0-1967 Code. The report further states that bolts when. selected in accordance with sections 104'.5.and 108.5.1 of the Code are already qualified and therefore the flange bolt stresses need not be evaluated. Based on the review of USAS B31.1.0-1967
- Code, it is concluded that the selection of flange bolts in accordance with section 108.5.1 eliminates the need for flange belt stress evaluations.
ITEM 4: EQUIPMENT NOZZLE LOADS s TVA performed equipment no::le evaluations for the no::les affected by the deficiencies addressed in Phase I of the program. New no::le loads were determined and qualified by simple conservative methods. No::les which could not be qualified by the simple method were further evaluated by less conservative methods. According to the.TVA personnel, only 5-10% of the no::les failed the conservative criteria and none failed the less conservative calculations. This was verified by a brief review of TVA's no::le calculations where one no::le which failed conservative criteria shown to have met the allowables by detailed calculations. Based on this
- review, it is considered acceptable to complete the review of the no::le loads in the Phase II progr&q.
ITEM 7: DOCUHENTATICN OF CES 74-2 According ho*TVA, CEB 74-2 was used in a very limited area. According to the ECTG report,CEB 74-2 is no longer used for design. Phase II of the program will evaluate all Alternate Analysis piping including those designed by CED 74-2. Since the concern is documentation and no technical aeficiencies have been identified, resolution of this issue during Phase II program is considered adequate. -S-
ITEM 8: CEB 80-5 STRESS INTENSIFICATION FACTCRS 1 CEB 80-5 stated, on page 15, that the stress intensification factors were considered and it provides separate tables, in Appendix B, for different fittings. The re f o're, it is apparent that-SIFs were considered. l ITEM 9: CEB 80-5, REV. 2 NOT IN MEDS { ECTG report states that this would be corrected by TVA in Phase II,
- however, during the NRC audit of employee concern, it was determined that TVA has corrected this deficiency and CEB 80-5, Rev. 2 is now in TVA's HED SYSTEM.
ITEM 10: CEB 80-5 DE3IGN LOADS ARE HIGHER THAN CEB 76-5 DESIGN LOADS Based upon discussion with TVA personnel and the review of documents i CEB 80-5 and CEB 76-5, it was determined that CEB 80-5, developed for ]
- SCN, used envelop of worst spectra of different structures to i
determine the loads. Whereas CEB 76-5, developed later for
- WBM, considers specific structures and locations and thus is less conservative than CEB 80-5.
According to TVA personnel, ground acceleration for WBN and SCN are the sa.ge, however, WBN spectra are higher than SCN. However, the SCN Alternate Analysis criteria CEB 80-5 gives higher support loads than WBN criteria CEB 76-5. Since CEB 76-5 and CEB 80-5 are based on different design criteria, it wculd be expected that thny would result in differe'nt* loads. TVA has stated that these doc'2ments will be verified as part of the Pl.sse II program. Based on the review of these documents cited in Item 1, this is considered acceptable. ITEM 12: CEB 75-9 MAY BE UNVERIFIED CEB 75-9 allocated allowable stresses for pressure, dead weight. and seismic loads. It is a conservative approach, however, the allocated allowables add up to slightly mbre than (1. 2 S ) the total allowable stress (see page 6 of CEB 75-9). TVA will address this concern in Phase II
- program, which is acceptable in view of the overall conservatism of CCB 75-9.
. ITEM 13: INCCMPLETE DCCUMENTATION TVA's review of the application of alternate analysis at SCN found-that generic documentation problems did exist. As a part of corrective action for the ECTG
- report, TVA revised SQN-AA-001 to require document of compliance with all aspects of Design Criteria.
This will be performsd as part of the Phase II effort. Since the specific technical issues that were considered the most significant were addressed in the Phase I
- program, the completion of the documentation for alternate analysis in the Phase II program is considered adequate.
ITEM 14: WATTS BAR REVIEW f This issue deals with the applicability of the WBN review results to SCN. As indicated in the ECTG report, t'.te basis for the specific-issues addressed in the SQN Phase I ef fort are based en the results of WBN evaluations. The Phase II program will require documentation of complia'nce with design criteria as stated in item 13. Therefore, the results of the WBN review are adequately considered in SQN alte nate analysis program. ~7-
w ITEM 15: ANALYSES NOT CURPENT According to the ECTG
- report, one. of the primary purposes of the Alternate Analysis review program is, to address this issue.
As discussed in item 13, the SQN Alternate Analysis. program will require docum9ntation of compliance with all aspects-of Design Criteria. Therefore, upos completion of this program, the analyses will become ~ current. In addition to the items addressed above, one other item was reviewed. This item deals with the statement contained in item 11 -of the ECTG' report The statement indicates that the alternately ana1ysed piping considers temperatures greater than 120 F for thermal expansion anTlysis. Tc address piping systems with temperatures less than 1209, TVA pr-4ded with a qualitative justification. One document included with this practice at LaSalle"Nuclear Station in a NEC's concurrence meeting en September 15, 1980. However, these justifications providad by TV, arn applicable for small-bore (up to 2" diameter) pipes wneret. :. 0 scme instances TVA has used AlternAce Analysis fur pipes much larcar than 2" diameter. Therefore, large diameter piping for which no thermal expansion evaluation was performed should be revie ed or additional justification should be developed for larger pipo s1:es for che Phase II program. l IV. CCUCLUSION l The.ECTG report concluded that the employees' concerns were valid at the time,they were expressed and that the Alternate Analysis Review Program is adequatr resol' e the employees' concerns provided that: 4 2t to upgrade the program to require a. the cenm! that docur. > -ed in Phase II to demonstrate that .re met for all alternatively analyzed all desiga piping,, J l ,---g . ~.., ,..,,---w --,4 p. e.,..,ry,.,. ,.I
R-- 44 +42.a .g 4 y y. g ,/ b. the commitment is carried out to verify that all Alternate-Analysis piping support spacings conform with all. design criteria requirements by. completion of Phase II. Based on review of the specific. issues addressed in this evaluation - and the previous NP.C review of the Alternate Analysis program, it,is concluded that TVA's Phase II program-is adequate to. address the issues considered'in this evaluation. HowcVer, it is reccmmended that TVA develop further justification in the Phase. II ' program for not performing thermal analysis for larger pipe sizes having temperatures of less than 120*F. a e 4 f G i l J T i i 1 4 r+
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