ML20210M763

Discusses & Resolves Issues Re Design Live Load Criteria for Load Combination Cases Involving Earthquake Loads for Category I Structures & IE Question on Subj in Engineering Assurance Program.Salp Input Encl

ML20210M763
Person / Time
Site:	South Texas
Issue date:	02/02/1987
From:	Rossi C Office of Nuclear Reactor Regulation
To:	Kadambi N Office of Nuclear Reactor Regulation
Shared Package
ML20210M767	List: ML20210M763 ML20212F281
References
NUDOCS 8702120627
Download: ML20210M763 (3)

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Docket Nos.: 50-498 and 50-499 FEB 021987 MEMORANDUM FOR: N.P. Kadambi. Pro.iect Manaaer PWR Pro.iect Directorate No. 5 Division of PWP Licensino-A FROM: C.E. Rossi, Assistant Director Division of PWR Licensing-A

SUBJECT:

SOUTH TEXAS PROJECT -' DESIGN l.IVE LOAD CRITERIA

References:

1. Memorandum for V. Noonan from P.K. Grimes dated September 15, 1986, on " South Texas Project, Engineering Assurance Program."

2. South Texas Pro.iect Electric Generating Station, finits 1 and 7. "NRC-SER Audit, January 7 through 11, 1985.

Response to Action item la."

3. Memorandum for N.P. Kadambi from R.L. Ballard dated October 17, 1986, on " South Texas Pro.iect. Design Live lead Criteria" with enclosure.

4 Letter ST-HL-AE-1806 from M.R. Wisenburg (HLPCl to V.S. Noonan dated December 10, 1986 on STP Practices for the l'se of Live Loads."

By memorandum (Reference 1) IE reauested NRR to provide assistance for resolution of the subiect issue. During an inspection of the Engineering Assurance Program for the South Texas Pro.iect at the architect-engineer offices in Houston, Texas last August, IE identified in the Civil / Structural discipline an issue which appeared to be a deviation from an FSAR commitment associated with load cor,binations. Specifically, it was noted that only 20%

'of the live load was used when combined with seismic loads in the design of the Reactor Containment Building internal structural steel. As a response to IE's concern, the applicant stated that 25% instead of 20% of the live load was actually used and that a similar issue was raised by the then Structural and Geotechnical Engineerino Rranch of NRR during a January 7,1985 design audit. Action item 14 of this audit raised the question of justifying the use of 25% of live load in the loadino combination where seismic loads are considered, and the response to that particular question (Reference 2) was accepted by the staff.

Contact:

S. Chan X29798

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N.P. Kadambi After reviewing the background of this issue, the Structural and Civil Engineering Section of the Engineering Branch recuested additional information on the modification of live load definition (Reference 3). On November 6, 1986, a meeting was held to discuss design live load criteria and the applicant's responses to staff questions. It was established during the meetino that the applicant had not deviated from an FSAR commitment associated with load combinations, viz, FSAP Section 3.8.4-3 and Table 3.8.4-1. However, it was agreed in the meeting that: (a) the definitions of the live load and its symbol L as used in the load combination expressions are not clear, and needed further explanation and clarification; (b) the load factor 1.0 applied to the symbol L should not be interpreted as the fraction of design live load; (c) the symbol L itself should be interpreted to include a certain percentaoe, say 75%,

of the pertinent design live load for a given structural element as described

'in Section 3.8.4.3.1 of the FSAR when the load combination being considered involves earthquake loads; (d) the definition of L and the load combinations stated in the FSAR should be applied to all Category I structures; and (e) the above listed clarifications (items (al through (dil should be documented in future FSAR amendments.

Subsecuent to the November 6, 1986 meeting, the staff has received and reviewed the applicant's response to the staff request for additional infomation and the proposed FSAR amendment (Reference 41 The applicant clarifies that there are actually two kinds of live loads; pemanent and temporary loads. The permanent live load represents the weight of pemanent equipment and components including piping, cable trays, ductwork and miscellaneous equipment distributed

, throughout floor areas. However, for load combinations which involve earth-cuake loads, this permanent live load is treated as additional dead load without reduction. The temporary live load represents the weight of temporary floor occupancies and construction loads including personnel and maintenance equipment loads that may be periodically imposed on the floors. The reduction factor of 25% is applied exclusively to the temporary live load used for the seismic loading combination. The factor is not applied to the permanent live load, nor to sustained live loads such as laydown area loads, specific and

,qeneric equipment loads, or -fuel storage loads. The staff finds that this

. method of considering live loads is satisfactory. The proposed FSAR amendment

'will clarify the definition of the symbols D and L (Sections 3.8.1.3.1, 3.8.3.3.1 and 3.8.4.3.1) in the load combination equations (Tables 3.8.3-1, 3.8.3-2, 3.8.4-1, and 3.8.4-2) and is therefore acceptable.

This menorandum thus serves to resolve the issue of design live load criteria for load combination cases involving earthquake loads for Category I s

t N.P. Kadambi structures and to resolve IE's question on this subject in the Engineering Assurance Program of South Texas Project.

A SALP Peport for this safety evaluation is enclosed.

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har es E. Rossi, Assistant rector Division of PWR Licensing-A

Enclosure:

As stated cc: R.L. Ballard V.S. Noonan B.K. Grimes D.C. Jeng R. Parkhill S.P. Chan I

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