05000324/LER-1981-056-01, /01T-0:on 810624,notification Received That 38 Pipe Supports Would Have Failed During Design Basis Seismic Event.Caused by Higher than Normal Slenderness Ratio. Identified Supports Upgraded

/01T-0:on 810624,notification Received That 38 Pipe Supports Would Have Failed During Design Basis Seismic Event.Caused by Higher than Normal Slenderness Ratio. Identified Supports Upgraded

ML20009G089
Person / Time
Site:	Brunswick
Issue date:	07/08/1981
From:	Poulk R CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20009G082	List: 05000324/LER-1981-056, Forwards LER 81-056/01T-0 05000324/LER-1981-056-01, /01T-0:on 810624,notification Received That 38 Pipe Supports Would Have Failed During Design Basis Seismic Event.Caused by Higher than Normal Slenderness Ratio. Identified Supports Upgraded
References
LER-81-056-01T, LER-81-56-1T, NUDOCS 8108030317
Download: ML20009G089 (3)

LER-1981-056, /01T-0:on 810624,notification Received That 38 Pipe Supports Would Have Failed During Design Basis Seismic Event.Caused by Higher than Normal Slenderness Ratio. Identified Supports Upgraded

Event date:
Report date:
3241981056R01 - NRC Website

text

NRC FORM 366 U. S. NUCLEAR REGULATORY COMMISSib"1

-(7 77)

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60 61 DOCK ET NUMBER 69 EVENT DATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h

.l o l 2 l l Notification was received from the Brunswick Engineer ing Support Unit that an analysis l

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loisi lin their original as-designed /as-installed condition during a Design Basis S ismic l

l0 ls l l Event. This could have caused a failure of the CRD insert and withdrawal lines. This, ll0 l 7 l levent did not affect the health or safety of the public.

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LER 2-81-56 ATTACHMENT Facility: BSEP Unit No. 2 Date: June 24, 1981 During a review of CRD supports, 60 CRD supports were identified as Potential Short-Term Fixes (STF). These supporcs were immediately epgraded in December 1981 and January 1981 and an analysis performed on the as-found condition. The initial premise for identifying sixty (60) gang frames as Potential Short-Term l

Fixes was that the "Kt/r" ratios of all the frames exceeded the accepted limit of 200. The ratios in excess of 200 were determined in association with a "K" factor of 2.1, which assumes that the structures will act as pure cantilevers.

In this regard the analysis concurred that a less conservative "K" factor could be considered for assessing "Short-Term" operability. As it is probable that the lower portions of the f rames, surrounding the CRD bundles, will remain in a nearly vertical attitude when subjected o out-of plane displacement, the structures will act similar to guided cantilevers in most cases. The "K" factor for guided cantilevers is 1.2 as per the AISC Manual's " Recommended Design Value When Ideal Conditions Are Approximated." Thus, a "K"

factor of 1.2 was considered in the reanalysis of the gang frames.

1 Since there were two (2) major generic types.of gang frames identified as

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Potential Short-Term Fixes, two (2) supports from each type were chosen to be analyzed. The major criteria used for choosing the "best" and " worst" frames l

from each category was the total load imposed on the frames, the overall dimen-i sions of the frame and the end connections used in construction. The frames I

which were not analyzed were grouped according to their similarity to the frames being analyzed.

Support 1-BSEP-7-4 was considered to be representative of the "best" of the large gang frames directly outside of containment.

Reanalysis of the frame indicates that it did not meet the Short-Term Criteria. The support considered to be the " worst" of the large gang frames was not analyzed since the "best" case configuration was found to be deficient. Based on the reanalysis of Support 1-BSEP-7-4, it is projected that all four (4) of the la :ge gang frames in each unit were Short-Term Fixes.

Support 2-BSEP-6-7 was considered to be representative of the '*best" of the smaller gang frames outside containment. Reanalysis of the frame indicates that it meets the Short-Term Criteria.

Based on the Short-Term qualification of 1

Support 2-BSEP-6-7, it is projected that twelve (12) of the Unit No. 1 smaller gang frar.es and ten (10) of the Unit No. 2 smaller gang frames initially identified as Potential Short-Term Fixes are acceptable in association with the Short-Term Criteria.

Support 2-BSEP-7-16 was considered to be representative of the " worst" of the j

smaller gang frames outside containment. Reanalysis of the frame indicates that it did not meet the Short-Term Criteria. Based on the reanalysis of Support 2-BSEP-7-16, it is projected that thirteen (13) of the Unit No. I smaller gang frames and seventeen (17) of Unit No. 2 smaller gang frames initially identified as Potential Short-Term Fixes did not meet the Short-Term Criteria.

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e In view of the locations of the frames projected to be Short-Term Fixes, it appears that all of the Insert and Withdrawal Lines did not meet the Short-Term Criteria, due to seismic inertial effects.

Note that the number of gang frames identified as Short-Term Fixes is based on the reanalysis of three (3) frames. In this regard, it is conceivable that a detailed analysis of each individual frame may reduce the number of frames identified as Short-Term Fixes. However, since all of the frames initially identified as Potential Short-Term Fixes have subsequently been modified in the field to meet the Short-Term Cri:3ria, we do net consider it beneficial to continue the analysis of structures that no longer exist in the plant.

The design and installation of the CRD System was a turn-key scope project by a subcontractor who performed no other work at the Brunswick site. Therefore, this is considered an isolated case with no generic implications with respect to other plant systems. As explained in letters on December 31, 1981, and February 25, 1981, a detailed line-by-line review of all plant systems is underway to ensure compliance with IE Bulletins 79-02, 79-07, and 79-14. Long-Term Fixes to the CRD lines will be completed by the completion of each unit's next respective refueling outage.

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