ML20215G289

Forwards SER & 870323 Contractor Technical Evaluation Rept of Util Calculation Sqnaps 008, Short Circuit Study Medium Voltage Sys. Correction of Deficiencies Before Restart Recommended

ML20215G289
Person / Time
Site:	Sequoyah
Issue date:	04/02/1987
From:	Rossi C Office of Nuclear Reactor Regulation
To:	Zwolinski J NRC OFFICE OF SPECIAL PROJECTS
Shared Package
ML20214F629	List: ML20214F626 ML20215G278 ML20215G289
References
NUDOCS 8704090238
Download: ML20215G289 (2)

Text

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Docket Nos.: 50-327/328 02 W MEMORANDUM FOR: John A..Zwolinski, Assistant Director for Projects TVA' Projects Division Office of Special' Projects FPON' Charles E. Rossi, Assistant Director Division of PWR Licensing-A

SUBJECT:

EVALUATION OF SEQUOYAH UNITS 1 AND 2 SHORT-CIRCUIT STUDY-MEDIUM VOLTAGE (6.9KV) SYSTEM Plar.t Name: Seouoyah Nuclear Power Plant, Units 1&2 Utility: Tennessee Valley Authority Docket Nos.: 50-327/328 Resp. Directorate: PAD #4 Project Managers: John Thompson / Joe Holonich Review Branch: PAEI Review Status: Incomplete Tennessee Valley Authority (TVA), by letter dated December 29, 1986, submitted electrical calculations fer Sequoyah Nuclear Plant Unit 2 for NRC audit reviews to support the design bases of Sequoyah Nuclear Plant Unit 2 for restart. NRC requested its contractor, Science Applications Internttional Corporation (SAIC), to conduct an independent technical evaluation of selected samples of the TVA Sequoyah electrical calculations. SAIC was requested to evaluate the TVA calculation rrethods for conformance to industry standards and practices, and to identify conditions adverse to the quality of the installed equipment. The Technical Evaluation Report (TER), dated March 23, 1987, prepared by SAIC (attachment to the Safety Evaluation Report) addresses the TVA calculation SONAPS 008 "Short Circuit Study Medium Voltage System," dated December 22, 1986. The Electrical, Instrumentation and Control Systems Branch / Division of PWR Licensing-A (PAEI) has prepared a Safety Evaluation Report (Enclosure 1) on this issue which concurs in the SAIC finding of deficiencies in regard to the short circuit interruption capability of the Sequoyah design.

The calculational methods and assumptions used by TVA for determining the available short circuit currents in the 6.9KV electrical supply system are consistent with industry standards and practices. Powever, the installed electrical protective devices (6.9KV circuit breakers) are undersized for the available short circuit currents and de not conform to the requirements of industry standards. As a result of a failure of an installed protective device to interrupt the maximum available fault current, the 6.9KV Class 1E or non-Class IE switchgear may fail catastrophi-cally and could possibly involve cascading failure of normal and alternate supply sources.

Contact:

A. S. Gill, PAEI -~

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f g John A. Zwolinski 2-The staff, therefore, recomends that TVA take appropriate action to correct this deficiency before restart.

V h Charles E. Rossi, Assistant Dir ctor Division of PWR Licensing-A

Enclosures:

As stated cc: T. Novak B. Liaw J. Holonich J. Thompson i

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