05000285/LER-1997-003, Forwards Assessments Containing OPPD Internal Findings & Recommendations Re Extraction Steam Line Rupture Event That Occurred on 970421.Commitments Made by Util Re LER-97-003, Also Encl

Forwards Assessments Containing OPPD Internal Findings & Recommendations Re Extraction Steam Line Rupture Event That Occurred on 970421.Commitments Made by Util Re LER-97-003, Also Encl

ML20140E360
Person / Time
Site:	Fort Calhoun
Issue date:	06/04/1997
From:	Gambhir S OMAHA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20140E365	List: 05000285/LER-1997-003, Forwards Assessments Containing OPPD Internal Findings & Recommendations Re Extraction Steam Line Rupture Event That Occurred on 970421.Commitments Made by Util Re LER-97-003, Also Encl ML20140E370 ML20140E380 ML20140E388
References
LIC-97-0087, LIC-97-87, NUDOCS 9706120029
Download: ML20140E360 (8)

LER-2097-003, Forwards Assessments Containing OPPD Internal Findings & Recommendations Re Extraction Steam Line Rupture Event That Occurred on 970421.Commitments Made by Util Re LER-97-003, Also Encl

Event date:
Report date:
2852097003R00 - NRC Website

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i Omaha PublicPowerDistrict 444 South 16th Street Mall Omaha NE68102-2247 June 4. 1997 LIC-97-0087 d.S. Nuclear Regulatory Commission l Attn: Document Control Desk  !

Mail Station P1-137 Washington. D.C. 20555-0001

References:

1. Docket No. 50-285

2. LER-97-003 Manual Reactor Trip Due to a Steam Line Rupture I

SUBJECT:

Assessments Related to the Extraction Steam Line Rupture of April 21, 1997 )

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As committed in the May 5.1997 Public Meeting, please find attached the assessments completed in response to the extraction steam line rupture of April 21, 1997. These documents contain Omaha Public Power District's (OPPD) internal firidings and recommendations concerning the Extraction Steam Line Rupture event that occurred at Fort Calhoun Station (FCS) on April 21, 1997.

OPPD's corrective actions for this event are listed in LER-97-003. For the I purpose of providing additional detail to the NRC. the corrective actions in ,

LER-97-003 are expanded upon in Attachment 1 of this correspondence. However. I these specific actions may change as 00PD continues to review and improve its ,

l program and are not meant as additional commitments. j At this time, the failure analysis of the ruptured elbow has not been received. This item will be sent at a later date.

Please contact me if you have ar. riuestions.

%Mj Sincerely. (

9706120029 970604 M [M PDR S

ADOcK 05000285 PDR S. '. Gambhir  :

Division Manager  ;

Engineering and Operations Support l

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l l 45.5124 Errpioyment with EqualOpportunity

l Attachments 1. Additional Information on Commitments .o the NRC for Corrective Actions Listed in LER-97-003

2. Fort Calhoun Station Root Cause and Generic Implications Report Fourth Stage Steam Extraction Line Rupture CR 199700445 Revision 0

3. Damage Assessment Report for the Break in the Extraction Steam Line Revision 0, May 3, 1997

4. Fort Calhoun Station Erosion / Corrosion Program Assessment Report, dated May 2, 1997

5. Fort Calhoun Station Self Assessment Erosion / Corrosion i Program Team Findings, dated May 6, 1997  ;

SKG/ddd c: Winston & Strawn E. W. Merschoff NRC Regional Administrator, Region IV J. L. Shackelford, Senior Reactor Analyst, DRS L. R. Wharton, NRC Project Manager W. C. Walker, NRC Senior Resident Inspector l

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Attachment 1 l

l Additonal Information on Corrective Actions

! Listed in LER-97-003 l

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l l Attachment 1 Additional Information on Corrective Actions Listed in LER-97-003 In LER-97-03 OPPD committed to " Revise the Erosion / Corrosion Program Plan, controlling procedures and modules to be consistent with industry standards.

This revision will include upgrade of the implementing procedures to be consistent with industry standards (e.g.. NSAC 202L. Rev. 1), development of l susceptibility documentation and requirements for use of current industry I experience. This will be completed by the beginning of the 1998 Refueling l Outage." This commitment will address the following issues identified in the self assessment:

1. Procedures should include more specific guidance on how Outage inspection locations are chosen.

2. Measured wear determination process should incorporate the following l industry practices:  ;

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a. Use of accepted practices to determine lifetime component wear (circumferential band moving blanket, point to point). l

b. Clarify the use of engineering judgment relative to wear dcterminations.

c. Process for incorporating measured wear into CHECWORKS models.

3. Sample expansion process should be revised to align it with industry standards. Specific changes include:

a. Clarify wording for small bore piping.

b. Add requirement for inspecting upstream of expanders / expanding elbows.

c. Clarify that pressure / temperature exemption only applies to raw water systems.

d. Clarify that expansion is to parallel components in each train.

e. Define the terms " component" and " highest wearing"

f. Specify highest wearing components in the same train.

l l 4 A document is needed to describe and control the identification of susceptible systems.

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5. A document is needed to describe and control the evaluation of l 4

susceptible systems.

f l 6. Documentation should be provided when grid refinement or scanning is performed'when significant erosion / corrosion is found.

7. The inspection data evaluation for components with PASS 2 CHECWORKS j

analysis should consider current predicted wear rates, j 1

!, 8. The program should employ verification of many elements and a formal. l process for changing program elements needs to be established. l (Examples: CHECWORKS model changes Erosion / Corrosion Program General  !

l Information Table. Erosion / Corrosion Program Technical Data Review.) l

! Also in LER-97-03 OPPD committed to " Revise and verify the Fort Calhoun ,

l CHECWORKS models consistent with industry standards by December 31, 1997." l 1 This commitment will address the following issues identified in the self

assessment:

1. Current plant CHECWORKS models need to be verified. l l

j 2. Inspection data from 1995 and 1996 outages needs to be incorporated into  !

j CHECWORKS models consistent with industry practice.

3. The plant CHECWORKS models need to be updated and controls put in place I

to document changes.

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In addition. OPPD plans to conduct a follow-up self assessment of the erosion / corrosion program following the next refueling outage to evaluate the effectiveness of program enhancements.

u During the implementation of our corrective actions OPPD will review and

, incorporate, as appropriate, the following recommendations of the self assessment team:

1. Program Basis Document should be updated to:

a) Eliminate duplication.

b) Remove unnecessary detail.

c) Make Program Basis Document and inspection procedure consistent.

2. Program Basis Document should describe how susceptible systems are dispositioned with respect to analysis.

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3. Program Basis Document should be updated to enhance communication i

responsibilities between Operations and Maintenance regarding feedback l to Erosion / Corrosion Engineer.

4 Guidance for documenting rationale for inspecting a specific location should be provided.

5. The inspection data form should be enhanced to address the following:

a) Directions for the use of this form.

b) Direction for what to do when measured minimum wall thickness is inconsistent with nominal wall thickness.

c) Direction on what to do when previous thickness is not available and nominal wall thickness is not used.

d) Clarify the step " List expansion of test sites not previously evaluated."

6. Typographical errors in the Program Basis Document should be corrected.

7. Typographical errors and inconsistencies in the inspection procedure should be corrected.

8. The highest allowable value of maximum allowable stress (SE) should be used to eliminate unnecessary conservatism and ensure consistency with CHECWORKS.

9. Program documents should be revised to proceduralize the following:

a) Trending of inspection results.

b) Qualitative evaluation of inspection data.

c) Evaluation of data to ensure thinning is bounded.

10. The acceptance criteria (Design Minimum Wall) being used for inspection data evaluations should be reviewed to ensure that OPPD applicable code requirements are met.

11. The grid size on 6" components should be reduced to comply with recommendations in NSAC 202L.

12. A clear separation in Erosion / Corrosion Program documentation between Flow Accelerated Corrosion (FAC) and other wall degradation mechanisms (such as raw water corrosion) should be provided.

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13. The guidance of NSAC 202L should be employed to address susceptible piping that is not suitable for modeling.

14. Complete CHECWORKS models of susceptible piping that is suitable for modeling should be developed.

15. The isometric drawings identifying CHECWORKS component identifiers are vital tools. A set of these drawings should be placed in retrievable  ;

storage and a second set should be used as a working copy. l

16. Sample expansions should not rely excessively on older inspections and should aggressively seek to ensure thinning is bounded, j 1

17. Sample expansion on tee branches need to be performed on the train I containing the branch, l 1

18. The inspection data evaluation process should address how to handle components with readings greater than nominal wall thickness.

19. Any exceptions to the grid procedures should be noted on the layout )

diagram provided in the outage summary notebook.

20. The CHECWORKS Program should be used to perform inspection data evaluation.

21. Each inspection data package should include a printout showing the inspection data matrix.

l 22. Although it appears that informal communication does exist between l

various departments and the Erosion / Corrosion Engineer the i

Erosion / Corrosion Engineer should perform a review of emergent MWRs via the Daily Emergent list. Review of this list should give a heads up to any developing system abnormalities.

23. The closure review of configuration change and maintenance documents I should be strengthened to identify any issue of concern to the l Erosion / Corrosion Engineer.

24. The Outage Scope Change / Addition Request form should be revised to ensure that requests for deletions and additions to outages are properly evaluated for Erosion / Corrosion scope.

25. Feedwater iron transport information should be added to the Seconday Chemistry Monthly Summary Report.

26. OPPD is a member of the CHECWORKS Users Group (CHUG). but is not an

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I active participant. FAC personnel, especially the Erosion / Corrosion Engineer, should attend the CHUG meetings. These meetings are held twice a year and cover current Erosion / Corrosion technical issues as well as a forum for discussing plant experiences.

27. OPPD should participate in the CHUG Plant Experience Database to ensure Erosion / Corrosion staff obtains future updates to this important industry experience database. '

28. As a one nuclear unit utility, it is recommended that OPPD consider joining with a group of other similar plants at other utilities to form a peer group to share experience and peer assistance.

29. A program to provide flow accelerated corrosion sensitivity training to

applicable plant staff beyond Erosion / Corrosion personnel should be j considered. This will help to ensure that plant conditions that may affect flow accelarated corrosion are communicated to the Erosion / Corrosion Engineer and incorporated into the Pr w am.

30. Use of resistant materials and systematic replacements should be considered.

31. The program should incorporate management involvement in important program elements. (Examples: CHECWORKS models, outage inspection scope.

outage close-out) l 1

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