ML18067A785

Submits Response to NRC RAI on Latteral Load Ductility Evaluation of Cable Tray Supports.Approach Thoroughly Reviewed & Accepted by NRC Staff in Supplemental SER, Providing Listed Staff Position

ML18067A785
Person / Time
Site:	Palisades
Issue date:	06/11/1997
From:	Smith N SEISMIC QUALIFICATION UTILITY GROUP
To:	Stolz J NRC (Affiliation Not Assigned)
Shared Package
ML18067A780	List: ML18067A779 ML18067A782 ML18067A783 ML18067A784 ML18067A785
References
REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR NUDOCS 9711240253
Download: ML18067A785 (2)

Text

SQUG June 11, 1997 Mr. John F. Stolz U.S. Nuclear Regulatory Commission

. Office of Nuclear Reactor Regulations 11555 Rockville Pike - Mail Stop 0-14D07 Rockville, MD 20555

Subject:

SQUG Response to NRC RAI on Lateral Load Ductility Evaluation of Cable Tray Supports

Dear Mr. Stolz:

In a letter dated December 5, 1996, the NRC staff provided an evaluation of SQUG's August 19, 1996, response to six (6) p_otentiaf generic issues which had been identified in Requests for Additional Information (RAis) sent to SQUG member utilities on their USI A-46 programs. In a letter dated April 18, 1997, SQUG provided responses to the NRC.

staff's evaluation of generic: issues #2,_#3, #4, and #6. Generic Issue #1, on the use of Generic Implementation Procedure (GIP) Method A, relates to shallow soil effects and will be answered shortly. This letter provides SQUG's response to generic issue #5, Lateral Load Ductility Evaluation of Cable Trays .

.The subject RAI requested the technical justification for the lateral load evaluation methodology provided in the GIP for cable tray supports. As your are aware from your previous review of this methodology, the cable tray evaluation approach is not based on traditional first-principle analyses. Instead, it is based on an extensive database of successful cable tray performance in strong motion earthquakes and shake table tests. The

• analysis checks described in the GIP process are intended to confirm that .nuclear plant cable tray systems are pounded by the earthquake and test experience. They are not intended to satisfy typical structural analysis criteria. This approach was thoroughly reviewed and accepted by the NRC staff in Supplemental Safety Evaluation Report (SSER) No. 2, pp. 30-31, which provides the following staff position:

• "The staff has reviewed the guidelines proposed by the SQUG for evaluating the seismic adequacy of cable and conduit raceway systems. The main objective of the proposed guidelines was to develop a cost-effective means of verifying the seismic adequacy of raceway supports in USI.A-46 plants. These guidelines were developed on the bases of analytical studies, shake-table experimental model tests, and assessment of the

• performance of cable and conduit support systems in past earthquakes.

9711240253 971114 PDR ADOCK 05000255 P PDR

or,.,

Mr. John F. Stolz June 11, 1997 "The staff considers that the plant walkdown guidelines represent an acceptable approach for evaluating the seismic adequacy of existing cable and conduit raceways in US! A-46 plants. Also, the s(afjagrees that the proposed analyticalprocedure is a reasonable approach to ensure that the cable and conduit raceways and supports in USIA-46plants.

when all the guidelines are satisfied. are as rugged as those obseryed in the past earthquake experience data. Although the proposed guidelines would not require detailed analyses and. therefore. would not predict the structural response of the racewqy support systems. they shouldprovide the needed rationale to judge the seismic adequacy of the raceway support systems with a reasonable factor of safety. Therefore. the staff concludes that the proposed guidelines for evaluation of seismic adeqitacy of cable and conduit raceways and their supports are acceptable subject to the staff evaluations described in this supplement. " [Emphasis added]

In summary, the. GIP cable tray evaluation method is based on extensive earthquake and test data and the NRC has.conclusively accepted the methodology in SSER No. 2.

• Therefore, in the absence of new information that invalidates this previous staff position, we believe additional reviews of this position are unwarranted, unnecessary and wasteful of both NRC and industry resources. To the extent that the NRC staff has new information

. that invalidates this position, please provide the information to us so that SQUG can evaluate whether the GIP should be revised. If there is no new information, we trust that this response closes this issue.

Sincerely, Neil P. Smith, Chaimian Seismic Qualification Utility Group cc: D. H. Dorman, NRC, MS: 0-14C7 .

R. Wessman, NRC, MS: 0-7E23 K Manoly, NRC~ MS: 0~7E23 ,

P. Y. Chen, NRC, MS: 0-7E23:

R. P. Kassawara, EPRI SQUG Steering Group SQUG Representatives and Alternates