ML20126D100

Forwards Response to NRC Request for Addl Info Re HVAC Design Validation & Concrete Embedments,Per Sser 25 (NUREG-0797) Outstanding Issue 18, HVAC Design Validation & Outstanding Issue 28 Re Concrete Embedments

ML20126D100
Person / Time
Site:	Comanche Peak
Issue date:	12/18/1992
From:	William Cahill, John Marshall TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RTR-NUREG-0797, RTR-NUREG-797 TXX-92630, NUDOCS 9212240036
Download: ML20126D100 (5)

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903.8 Ref. # 10CFR50.34(b)

TUELECTRIC William J. Cahlli, Jr,

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December 18, 1992 l

1 11 S. Nuclear Regulatory Commission Attn: Document Control Desk l Washington, DC 20555

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION (CPSES) -

UNIT 2 DOCKET NO. 50-446 REQUEST FOR ADDITIONAL INFORMATION HVAC DESIGN VALIDATION AND CONCRETE EMBEDHENTS REF: 1) Supplement No. 25 to NUREG-0797 Related to Operation of the Comanche Peak Steam Electric Station, Unit 2 (September 1992)

Gentlemen:

In September 1992. Reference 1 was issued and Section 1.7 identified outstanding issue 18. 'HVAC Design Validation," and outstanding issue 28.

" Concrete embedments". As a result of subsequent discussions with the NRC staff, additional information regarding these two issues was requested.

The response to the request for additional information is provided in the Attachment to this letter. If there are any questions, please call Mr. Carl B. Corbin at (214) 812-8859.

Sincerely, Willi J. Cahill, Jr.

By:

J. S. Marshall Generic Licensing Hanager CBC Attachment c- Mr. J. L. Milhoan Region IV Mr. B. E. Holian. NRR Resident Inspectors, CPSES (2) 230040 9212240036 921218 PDR ADOCK 0500044I 4m N. Obve Street LB. 81 Danas. Texas 15201 hqr A PM

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Attachment to TXX 92630 Page 1 of 4 SUPPLEMENT 2S TO CPSES SER OUTSTANDING ISSUE 18 i

The purpose of this paper is to provide additional information relevant to NRC outstanding issue 18 documented in Supplement 25 to the Safety Evaluation Report (SER) related to the operation of the Comanche Peak Steam Electric Station (CPSES). Unit 2. Outstanding issue 18 pertains to the HVAC design validation: specifically, seismic damping values and structural member weld qualification.

INTRODUCTION l i

Section 1.11 of Supplement 25 to the CPSES SER summarizes the NRC review of the implementation of the CPSES Corrective Action Program (CAP) for Unit 2.

This section identifies differences in the Unit 2 CAP relative to the Unit 1 CAP as described by the NRC in SSERs 13 through 20. These differences are- l described in some detail beginning on page 1-12 items (1) through (25). The '

items which constitute outstanding issue 18 are (6) and (7). The following paragraphs provide additional information to that provided under these items.

OUTSTANDING ISSUE 18 - HVAC DESIGN VALIDATION

, Jtem 6 - Seismic Damping Values The structural damping levels used for the seismic qualification of the CPSES Unit 2 HVAC duct systems (duct and duct supports) were selected based on general structural connection details used in their design'and fabrication. It is well known that connection type is the prime contributor to variations in damping of a vibrating steel structure.

NRC RG 1.61 recognizes this and specifies substantially higher damping levels for analysis of bolted structures versus welded sttuctures. - ,

Since few structures or substructures are either wholly bolted or wholly welded the nature, significance. and connection details of the various-structural components of the entire structure must be evaluated to

- determine the appropriate and conservative damping levels to be used.

The Unit 1 and Unit 2 HVAC duct systems at CPSES have'similar construction. The HVAC duct' segments are joined with either bolted companion angles and gasketing or bolted hemmed flange type joints and gasketing. These joints are spaced along the duct at maximum four foot intervals, with duct supports spaced approximately every eight to' ten feet. Additionally, the ducts at Comanche Peak have either bolted, welded or shimmrd connections to the suoport members. The duct support member-internal connections are generally welded. The duct support attachment to the building structure is typically a clip angle with one or more expansion anchor bolts for attachment to concrete. The general structural design ' philosophy is very similar to the CPSES cabic tray systems (cable tray and cable tray supports).

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Attachment to TXX-92630 Page 2 of 4 Under the CAP for Unit 1 full-scale dynamic tests of cable tray systems were performed to confirm the conservatism in the use of 4% and 7%-

damping values for their seismic qualification when subjected to th'e OBE and SSE earthquake respectively. Because of the similarity in the design philosophy of the cable tray systems and the HVAC systems TU Electric initiated review of the damping values used for the seismic qualification of the CPSES Unit I and Unit 2 HVAC duct systems in May of 1989. This review is documented in Project Technical Report No. 008.

This report concluded that, similar to the cable tray systems, the damping response of the HVAC duct systems is predominated by the_

, behavior of the bolted connections and that it is, therefore, l appropriate and conservative to use the 4% and 7% damping values for the i

seismic qualification of the HVAC duct systems when subjected to the OBE '

and SSE earthquake respectively.

Subsequently, in December of 1989 DBD CS-086 "HVAC Duct and Duct Supports" was revised to state that the seismic analysis / qualification of Unit 1 and Unit 2 HVAC duct systems will utilize-4% and 7% damping values for the evaluation of the OBE and SSE earthquake respectively.

This change was evaluated to be in compliance with NRC RG 1.61 and all CPSES licensing commitments.

Item 7 - Structural Member Weld Qualification Item 7, as appeared on Page 1 - 14 of SSER 25, discusses the computer software used for evaluation of the welds between HVAC duct support structural members. ANGLEWELD, a contractor PC program, was used for .

the design validation of Unit 1 HVAC duct supports, P Delta STRUDL, a ,

vendor standard program has been used for the design validation of Unit 2 HVAC duct supports.

The P-Delta STRUDL program has been used widely throughout the nuclear industry. The program has been verified by the software vendor under-its software OA program. The software-verification activities included.

the execution of an (xtensive set of test problems. The bending effects caused by eccentricities between the centroidal axes of structural members and the welds were included in the test problems, t

The software vendor has been audited by TU Electr.c and is currently on TV Electric's Approved Vendors list. In addition, ABB 1mp611 Corporation, the-contractor responsible for design validation of'the l Unit 2 HVAC duct systems performed hand calculations to verify weld l evaluation results generated by P-Delta STRUDL. These calculations also confirmed that P-Delta STRUDL correctly performs the weld evaluation including proper permutations due to weld eccentricities.

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4 Attachment to TXX-92630 Page 3 of_4 SUPPLEMENT 25 TO CPSES.SER ,

OUTSTANDING ISSUE 28 The purpose of this paper is to provide additional information relevant'to NRC outstanding issue 28 documented in Supplement 25 to the Safety Evaluation Report (SER) related to the operation of the Comanche Peak Steam Electric Station (CPSES). Unit 2. Outstanding issue 28 pertains to the program to evaluate Hilti Bolts which may be installed in close-proximity to through bolts.

INTRODUCTION Section 1.11 of Supplement 25 to the CPSES SER summarizes the NRC review of the implementation of the CPSES Corrective Action Program (CAP) for Unit 2.

This section identifies-differences in the Unit 2 CAP relative to the-Unit _1--

CAP as described by the NRC in SSERs 13 through 20. These differences are described in some detail beginning on page 1-12 items-(1) through (25).

Item (13) corresponds to outstanding issue 28. The following paragraphs provide additional information to that provided under these items.

OUTSTANDING ISSUE 28 - HILTI BOLT PR0XIMITY T0 THROUGH BOLTS Item 13 - Hilti Bolts Proximity to Through Bolts item 13. as appeared on Page 1-15 of SSER 25, discussed evaluation of' existing concrete expansion anchor bolts which were installed in close proximity to through bolts. For Unit 1, an engineering walkdown of a sample of concrete surfaces was performed to obtain as-built anchor bolt locations. Appropriate bolt capacity reductions due to spacing requirements were calculated and compared to the design load. There-were no required hardware changes resulting from this evaluation. . Thus, ,

the results indicated with a high degree of confidence that all existing-concrete anchor bolts comply with the validated CPSES design-requirements and that all existing concrete anchor bolts are acceptable based on the evaluated sample population. .

Since the design and installation of existing concrete anchor bolts in both units utilized the same criteria, the Unit I results of the ,

evaluation of -the anchorage sample is applicable to Unit 2 especially.

considering the large sample size of concrete surfaces evaluated. To-provide added assurance.for Unit 2 concrete anchorages, additional-Unit 2 concrete surf aces were selected for engineering walkdown and evaluation using the identical approach as that used for Unit 1.

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Attachment to TXX-92630-Page 4 of 4 On April 27, 1992. TV Electric by letter logged TXX-92215, submitted a report entitled " Validation Efforts for CPSES. Unit 2* which addressed _

this-issue in_Section 7.6.2(a) (pages 51 and 52). -The last sentence in Section 7.6.2(a) stated, " Additional samples of concrete surfaces were collected for evaluation and the same confidence leve: was achieved."

The original input for this section stated that the~ evaluation was not c ompl et e . However, due to. editorial revisions during the approval process, this section of the report was incorrectly revised to state the evaluation was complete.

Evaluation of the results for Unit 2 is now complete. Similar to-Unit 1, no required hardware changes resulted. This evaluation has-confirmed that the Unit 2 installations are acceptable.

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