ML19095A502

Submit Licensee Event Report Nos. LER 78-013/03L-0 Re Six Snubbers Not Meeting Test Criteria, & 78-014/03L-0 Re Mount Plate Was Warped, & 3 of 8 Bolts Were Insufficiently Embedded

ML19095A502
Person / Time
Site:	Surry
Issue date:	07/07/1978
From:	Stallings C Virginia Electric & Power Co (VEPCO)
To:	O'Reilly J NRC/RGN-II
References
Serial No. 387 LER-1978-013-03L-0, LER-1978-014-03L-0
Download: ML19095A502 (7)

Text

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.. :: LICENSEE EVENT REPORT 10 6

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7 8 60 61 DOCKET NUMBER 68 69 EVENT DATE 75 REPORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES@

JDuring refueling shutdown, a second sequence of snubber functional testing carried out

[Q]I:J lat company choice resulted in testing of 70 snubbers, six of which did. not meet "as

[QEJ jfound" test criteria. The condition of all six sriubbers appeared to have no effect on

[QJ]J 1unit safety and on the health and safety of the public. This is reported per T.S.

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• - QJIJ ~he cause is attributed to drift of the settings during unit operation. All .snubbers o::::m rere adjusted and passed testing to more stringent "as left" criteria.

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7 B 9 10 68 69 80 ;;;

T. L. Baucom (804)-357-3184 0 0.

NAME OF P R E P A R E R - - - - - - - - - - - - - - - - - - - PHONE:-------------

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e Surry Power Station, Unit 1 Docket No: 50-280 Report No: 78-013/03L-0 Event Date: 6-6-78 Snubber Functional Tes-ting

1.

Description:

With unit at refueling shutdown, snubber functional testing, in ac-cordance with Technical Specification 4.17 was conducted with the follow-ing results:

DATE MK. NO. AS FOUND SPEC.

6-6 WFPD- -12 Lock-up 5.0 >6.0 6-9 RH- -5 Bleed 1.5 >2.0 6-10 CH- -302 Bleed 0.4 >2"~0 6_-11: RS- -101 Bleed 1.3 (Tension) >2.0*

0.7(Cornpres- >2.0 sion) 6-18 RH- -2 Lock-up 4.4 >6.0 6-22 RH- -1 Bleed 1.1 (Tension) >2.0 (all figures in inches per minute)

To insure testing was conducted on a representative basis, the snubbers were selected at random. Seventy snubbers in all were tested, reflecting the data shown above and the Technical Specification requirement that t~n snubbers be tested for each snubber that fails to meet acceptance criteria.

It should be noted that this report covers the second sequence of snubber functional testing during this refueling outage. The first se-quence consisted of ten snubbers, all of which met "as found" test cri-teria.

2. Consequences/Status of Redundant Systems:

The functions of the bleed effect are to permit system movements with temperature changes and to allow slow relief of stresses during a seismi~ event. The lock-up function prevents large movements of systems

• relative to building structure during a seismic event. Evaluation of the respective units involved is as.. follows:

WFPD- -12 Lock-up at 83% of minimum permissible would indicate less movement during a seismic event but a stress level well within the rating of the snubber. Since bleed rate was acceptable, the stresses would have been relieved adequately.

RH- -1/-2/-5 These snubbers serve a system normally isolated at power.

In the case of a seismic even*t the stresses could be accomodated. The fact that the unit had been at power and then cooled down with no observa-ble signs of distress to piping or snubbers indicates that the bleed rates, while unacceptable by defined criteria, were satisfactory to accomodate

e Surry Power Station, Unit 1 Docket No: 50-280 R~port*No: 78-013/0JL-0

• Event Date: 6-6-78 Snubber Functional Testing thermal movements.

CH- 302 As above, the bleed rate appeared satisfactory to accomodate all thermal movements since the snubber had not appeared to be distressed.

RS- 101 This snubber serves a system that would be required to func-tion on the dual "LDC.A-plus-earthquake" type mishap - a highly remote event.

The system is "50% system" backed -up by three other 11 50%-systems" and is normally non-pressurized. The relief of stresses incurred by lock-up dur-ing a seismic event appears adequate.

On review, the "as found" conditions of the subject snubbers appear to have had no effect on the unit and, therefore the health and safety of the general public were not affected.

3. Cause:

The apparent cause of the non-acceptable "as found" conditions is considered to be drift of adjustment settings during unit operation.

4. Innnediate Corrective Action:

The six snubbers were adjusted and passed testing to more stringent "as left" criteria. All were reinstalled for service.

5. Subsequent Corrective Action:

No further corrective action was needed.

6. Action to Prevent Recurrence:

None required.

7. Generic Implications:

No generic implications are indicated by this event other than those which mandate the current snubber inspection and test programs.

LICENSEE EVENT REPORT

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~~~~~ ~© 1o I s I o I o 1 . o13 I 3 1s 101 o 16 1o p f7 ts 101 o p Io I 6 17 1s IG) 7 8 60 61 DOCKET NUMBER 68 69 EVENT DATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES@

!With the unit at refueling shutdown, the mount plate of snubber l-WFPD-HSS-10 appeared I

-~ mIJ 1to be separating from the crane wall. Close evaluation revealed that the mount plate

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• mIJ 1was warped and three of eight bolts were insufficiently embedded. Unit may not have

~- ~ I been able to fully sustain stresses of a seismic event. This ii; reportable per T .S.

_ [Q))J" 16.6.2.b. (2). The hea*lth and safety of the public were not affected .

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_CAUSE DESCRIPTION AND CORRECTIVE ACTIONS @

!Bolt embedment had been obstructed by a reinforcing bar in the concrete. The plate ITIIJ !was warped from fabrication. A new plate was fabricated from specs provided by tbe

[I))] 1Architect Engineer. New bolts were embedded to a minimum of five inches required by

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T. L. Baucom PHONE: _ _:(..:;8:.. :.0:..:.:4_,_)--""3.. ,_5-l-7._-.t-3.wl8..i..::L:t..f- - -

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NAME OF P R E P A F ~ E R - - - - - - - - - - - - - - - - - - - l'.i

e e Surry Power Station, Unit 1 Dc.cket No: 50-280 Report No: 78-014/031-0 Event Date: 6-7-78 Snubber Mounting Plate

1. Description of Event:

With the unit at refueling shutdown, on or about May 3, 1978, the anchor base plate for snubber l-WFPD-HSS-10 was found with the plate not flush to the wall and right and left upper corner nuts not installed.

Immediately, the nuts holding the base plate were checked and found tight.

It was also determined that the curvature of the plate was the result of fabri_cation and not caused by any abnormal loading during the period of service. By telephone conversation with the Architect Engineer, the mount was evaluated as satisfactory if at least the bolts at the 12, 3, 6, and 9 o'clock positions were tight. The subject bolts were confirmed as tight and at that time, the snubber was considered operable.

On 6-7-78, the assembly was inspected by the pipe stress specialist from the staff of the Architect-Engineer who then indicated concern for the embedment length of the holding bolts. Further research of records and interviews with personnel involved in the installation indicated that the required embedment may not have been achieved on three of eight bolts because a reinforcing bar in the concrete had been encountered when dril-ling the holes. The bolts installed could not be moved or jacked out to actually determine embedment length. The mount appeared sound by the eval-uative methods available, but positive confirmation of embedment length could not be obtained. The conservative approach was to consider the snubber inoperable due to the uncertainties of the mounting assembly. This condition, as evaluated on 6-7-78, was considered to be contrary to Tech-nical Specification 3.20 and reportable in accordance with Technical Speci-fication 6.6.2.b.(2).

2. Probable Consequences/Status of Redundant Systems:

Had a seismic event occurred, it is possible that the mount plate may not have performed its intended function. The Architect Engineer special-ist's determination was based on "worst case" assumptions that the three bolts had no holding power. This approach was ultraconservative, and in fact, the three bolts in question had some holding strength. Had a seismic event occurred, it is possible that the feed line involved could have been subjected to an unanalyzed condition. Since operation prior to shutdown was normal, the health. and safety of the public were not affected.

3. Cause:

The appearance of loose bolts was the result of curvature of the mount plate, which developed during fabrication. Evaluation of the mounting indi-cated that the three bolts in question were not sufficiently embedded in the wall to provide the assumed holding strength, but were in fact tight in the wall. The installation was performed in'October, 1977 under adverse condi-tions and the short embedment occurred because the bolt holes were blocked by reinforcing bar when they were drilled. (See- Surry RO-Sl-77-18)

--~~-------- ---

• e Surry Power Station, Unit 1 Docket No: 50-280 Report No: 78-014/031-0 Event Date: 6-7-78 Snubber Mounting Plate (Continued)

4. Immediate Corrective Action:

The plate was removed and a new plate was fabricated to specifications and drawings provided by the Architect Engineer. Four new bolt holes were drilled and minimum five inch embedment was achieved. Flush installation of the mounting plate was achieved.

s. Subsequent Corrective Action:

The completed mounting was inspected for conformance to the A-E speci-fications and found correct.

6. Action to Prevent Recurrence:

None required. Mounting is now correct.

7. Generic Implications:

None.