ML20247H576

Ack Receipt of & Requests Addl Info Re Rept on Events of 890423 & 0505 Re Backflow Through Auxiliary Feedwater Sys

ML20247H576
Person / Time
Site:	Comanche Peak
Issue date:	09/14/1989
From:	Warnick R Office of Nuclear Reactor Regulation
To:	William Cahill TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
References
NUDOCS 8909200024
Download: ML20247H576 (8)

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SEP ,4 1969 In Reply Refer To:

Dockets: 50-445/89-30 50-446/89-30 TU Electric ATTN: W. J. Cahill, Jr.

Executive Vice President 400 North Olive Street, Lock Box 81 Dallas, Texas 75201 Gentlemen:

Thank you for your letter of August 18, 1989,-in response to our letter dated July 10, 1989, which transmitted the report of the Augmented Inspection Team. As a result of our review, we find that additional information is needed. Our comments and questions are enclosed.

We note from your response that you plan to incorporate lessons learned into a formalized incident investigation procedure. The NRC staff desires to review the procedure as soon as it is finalized.

Please keep us informed. .

Please provide the supplemental information within 30 days of the date of this letter.

Sincerely,

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ORIGINAL C'GG EY R. F. W??JECr R. F. Warnick, Assistant Director for Inspection Programs t /

Comanche Peak Project Division Office of Nuclear Reactor Regulation

Enclosure:

As stated.

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(See attached).

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L *\ ...../ SEP i 41989 .

s In Reply Refer To:

Dockets: 50-445/89-30 50-446/89-30 1 TU Electric ATTN: W. J. Cahill, Jr.

Executive Vice President

'400 North Olive Street, Lock Box 81 Dallas, Texas 75201 Gentlemen:

Thank you for your letter of August 18, 1989, in response to our.

letter dated July 10, 1989, which transmitted the report of the Augmented Inspection Team. As-a result of our review, we find that additional information is needed. Our comments and questions are enclosed.

We note from your response that you plan to incorporate lessons learned into a formalized incident investigation procedure. The NRC ,

staff desires to review the procedure as soon as it is finalized.

Please keep us informed.

Please provide the supplemental information within 30 days of the date of this letter.

Sincerely, R F u)A R. F. Warnick, Assistant Director for Inspection Programs Comanche Peak Project Division Office of Nuclear Reactor Regulation

Enclosure:

As stated.

cc w/ enclosure:

(See attached).

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f'p W/' J . Cahill, Jr.

cc w/ enclosure:

. Roger D. Walker 'IU Electric Manager, Nuclear Licensing c/o Bethesda Licensing TU Electric 3 Metro Center, Suite 610 Skyway Tower Bethesda, Maryland 20814 400 North Olive Street, L.B. 81 Dallas, TX 7t201 E. F. Ottney P- O. Box 1777 Juanita Ellis Glen Rose, Texas 76043 President - CASE 1426 South Polk ~ Street Jack R. Newman Dallas, TX 75224 Newman & Holtzinger 1615 L Street, NW Texas Radiation Control Suite 1000 Program Director Washington, DC 20036 Texas Department of Health 1100 West 49th Street George R. Bynog Austin, Texas 78756 Program Mgr./ Chief Inspector Texas Dept. of Labor & Standards GDS Associates, Inc. Boiler Division 1850 Parkway Place. Suite 720 P,0. Box 12157, Capitol Station Marietta, GA 30067-8237 Austin, Texas 78711 Honorable George Crump County Judge Glen Rose, Texas 76043 Ms. Billie Pirner Garde, Esq.

Garde Law Office 104 East Wisconsin Avenue Appleton, WI 54911 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlingten, Texas 76011 William A. Burchette, Esq.

Counsel for Tex-La Electric Cooperative of Texas Heron, Burchette, Ruckert & Rothwell 1025 Thomas Jefferson St., NW Washington, DC 20007 l l

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'NRC COMMENTS / QUESTIONS REGARDING THE TU ELECTRIC RESPONSE:

" REPORT'ON EVENTS'OF APRIL 23 AND MAY 5, 1989, INVOLVING BACKFLOW THROUGH THE AUXILIARY FEEDWATER SYSTEM"'

l. General i Numerous commitments are stated in your response to'the NRC Augmented Inspection Team (AIT) report regarding testing, engineering evaluations, calibration of instrumentation, procedural changes, etc. How will these commitments be tracked?

2. Paragraph I.C, p.5 Your response did not clearly address the circumstances which permitted the April 23 event to be nearly identically recreated on May 5. Rather,-the two events are treated, for the most part, as independent occurrences. Please provide a more complete assessment of how and why the May 5 event occurred given the (then) recent experience of the April 23 event.

3. Paragraph II, p.9 Your letter states that the NRC was informed May 6, 1989, of the backflow events which occurred on May'5. Our information indicates that the AIT team and the Task team were notified by the system engineer of the additional pipe paint burning (and, therefore, the second event) at a team meeting on Monday, May 15, 1989, at 3:00 p.m.- Please provide information and details to support your statement.

4. Paragraph III.A, p.12 It is not clear that the feedwater isolation bypass valves are suitable for service as installed? If they are not, what modifications or administrative measures are going to be taken to lessen the probability of additional backflow events through these valves?

5. Paragraph IV.A, p.14 This paragraph provides the introduction to the root cause investigation and identifies certain areas which could have been improved by TU Electric. In part, one statement asserted that "In addition, the Task Team did not fully understand the information needs or expectations of the AIT." As a matter of record, the complete scope of the NRC's AIT inspection at Comanche Peak relative to the multiple check valve failures in

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2 I the AFW system were: identified to TU Electric management by the AIT leader during-the entrance conducted by the NRC on May 2, 1989. It would~ appear that plant management failed.to recognize the significance.of the NRC:AIT inspection as revealed'during the NRC entrance or.that this information was

'not adequately transmitted to the' Task team. .In either case, please clarify your statement that the information needs and expectations of the AIT were not fully understood by the Task team.

6.. . Paragraph IV.C,'p.15 Your letter states that you used ". . . the computer Assisted Drawing (CAD) program to determine the actual measurements of critical' valve-internal components." This would appear not to be so.as these dimensions are input to create the drawing.

Please clarify what your statement intended to convey.

7. Paragraph IV.E, p.18 The summary presented states, in part, that the " Check valve failures occurred because of incorrect instructions for reassembly." This conclusion was also confirmed by the AIT; however, no mention is made in your response of~the apparent inadequate post-maintenance testing of these valves; testing that would have detected the incorrect reassembly. Please provide additional information relative to the omission of this item and TU Electric plans for corrective actions to strengthen post-maintenance and post-modification testing.

8. Paragraph V.A, p.20 This paragraph describes the " actual significance" of the April 23 and May 5 events; however, this section is incomplete.

Specifically, the AIT report had identified a concern relative to the lack of objective evidence to support the applicant's statement that steam generator blowdown had been secured on all steam generators at approximately 6:25 a.m. on April 23, 1989.

Please provide supporting evidence that steam generator blowdown was secured during the event.

9. Paragraph V.B, p.20 & 21 This paragraph describes the piping and pipe support stress analyses which were performed and inspections which were performed as a result of these analyses. Please provide the following additional information:

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l a. The report states that ultrasonic inspections verified that no plastic deformation had occurred in several areas where piping Code allowable stress was exceeded. Without baseline thickness measurements taken prior to the event, ultrasonic inspections can not establish whether plastic deformation occurred. .Therefore, there is no basis for your conclusion that the piping stresses due to this event were in the elastic range.

b. This paragraph omits reference to the one support that was visibly damaged (see Executive Summary, paragraph ID, i p.5). A discussion of this support is necessary. The i discussion should clarify if damage to this support was predicted by the analysis and if not, why not. In addition, if failure of this support was included, please clarify the impact on the analysis in regards to load transfer to other supports.

10. Paragraph V.E, p.22 It is the position of the AIT that as a result of the precursor events on April 5 and 19, and again as a result of the backleakage events on April 23 and May 5, the backleaking check valves should have been considered inoperable and, therefore, the AFW system should have been considered inoperable. Please address operability.

11. Paragraph VI.A, p.24 Your letter states that Diablo Canyon attributed its check valve leakage problems to the uncertainty involved in aligning the disc parallel to the seat during assembly. Your letter goes on to say in the same paragraph, that this problem is unrelated to the check valve failures of April 23 and May 5, 1989.

The AIT notes that two check valves reworked to the new height adjustments failed their reverse flow system leakage tests.

The root cause was determined to be rotational misalignment of the bonnet disc and valve body seat during installation. This would appear to contradict your conclusion.

12. paragraph VI.B, p.25 This paragraph states that "It is TU Electric's position that applicable provisions in Section XI of the ASME Code do not require that check valves be tested other than in the forward direction." Concerning this statement, it is the AIT's position that ASME Code requirements are minimum requirements and that it is imperative that safety-related systems be maintained operable. That is one reason preoperational testing and post-maintenance / modification testing are required by the

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l NRC. If you feel your system would have detected these failures, then please provide additional information clarifying your position and identify in detail your preoperational I testing program which would have identified the check valve failures.

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13. Paragraph VI.B, p.25-26 The paragraph states that TU Electric revised its post-modification test procedures in 1988 to require post-work testing for backleakage. please provide information as to why these post-modifica"Lan procedures were not applied to previously modifia? c'veck valves. Were they applied to check valve 1AF-069 aftet April 19, 1989?

14. Paragraph VI.B, p.27 Your letter states that the manager of Operations felt that the valve positioning error of April 23 was isolated to the shift in question. How can this operator error, or any other, be considered isolated to one particular shift given the homogeneity of the training and certification process? It seems evident that any operator error must be considered a generic problem. Please comment on this and explain further how the original assumption was made that this error was isolated to one shift. Additionally, describe how management will ensure proper consideration of the generic implications of future incidents of personnel error.

15. Paragraph VII.B, p.29-32 Paragraph VII.B.2.c states that a check valve was bench tested following adjustment of the bonnet elevation in accordance with the revised procedure and that the test showed the procedure was adequate. However, valves 1AF-075 and 1AF-078 failed the backleakage test following reassembly using the modified installation methods for correct bonnet elevation adjustment.

Both valves were found to have been installed with rotational misalignment between the bonnet-disk assembly and the valve seat. The revised installation procedure was not adequate for valves lAF-075 and 1AF-078. Please comment.

16. Paragraph VII.B.1.b, p.30 Your response states that following an evaluation that is in process, TU Electric will determine whether to increase the distance between orifices and check valves, and will base the timing of implementing design changes on a determination of whether check valve failure is imminent. Please provide  !

additional information on this issue and explain how the l probability of imminent failure will be determined. This issue should be resolved prior to fuel load.

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17. Appendix 1, paragraph B.3, p.49 Your letter states that Operations management, in light of the known check valve problems, decided to proceed with testing activities based on the conclusion that administrative controls in place would compensate for the identified deficiencies.

Please explain which administrative controls were relied upon i

to provide this assurance and why they failed to prevent the May 5 event.

18. Appendix 2, p.53 It is our understanding that the main feedwater upper penetration check valves could not be backleakage tested individually and thus, perhaps only one out of each pair of valves held. Please clarify.

Does the "GPM Leakage" identified for the valves listed in the table on page 53 (approximately 5.4 GPM) represent the true leakage or a minimum value due to limitations in the test equipment?

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