ML20205F338
| ML20205F338 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 10/20/1988 |
| From: | Michael Ray TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8810280046 | |
| Download: ML20205F338 (3) | |
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TENNEOCEE VALLEY AUTHORITY CH ATTANOOG A. TENNESSEE 374ol SN 157B Lookout Place 08T 201988 TVA-SQN-TS-87-27 10 CFR 50.90 U.S. Nuclear Regulatz y Consnission ATTN Document Control Desk Washington D.C.
20555 Gentlemen In the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 SEQUOYAH NUCLEAR PLANT (SQN) - TECHNICAL SPECIFICATION CHANGE 87-27 Reference TVA letter to NRC dated August 5, 1987. "Sequoyah Nuclear Plant -
Technical Specification Change 87-27" The enclosed information regarding technical specification change 87-27 is provided in accordance with a request from Jack Donohew during a September 27, 1988 telephone conference call. The enclosure provides information regarding the adequacy of overpressure protection for the residual heat removal system.
Please direct questions concerning this issue to R. W. Meadors at (615) 870-6649.
Very truly yours.
TENNESSEE VALLEY AUTHORITY 0\\
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U.S. Nuclear Regulatory Commission.
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Ma. S. C. Black, Assistant Director for Projects TVA Projects Division U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. F. R. McCoy Assistant Director for Inspection Programs TVA Projects Division U.S. Nuclear 3egulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. Michael H. Mobley, Director (w/o enclosures) 3 Division of Radiological Health T.E.R.R.A. Building 150 9th Avenue, N Nashville, Tennessee 37203 f
Aaerican Nuclear Insurors Attention Librarian The Exchange, Suite 245 270 Farmington Avenue Farmington, Connecticut 06032 1
j Sequoyah Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road
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ENCLOSURE SUPPLEMENTAL INFORMATION REGARDING TVA-SQN-TS-87-27 The following paragraphs provide information regarding the adequacy of overpressure protection for the residual heat removal system (RHRS) when the letdown valves (74-1 and 74-2) from the reactor coolant system (RCS) are open. Also addressed below is why the automatic closure interlock (ACI) setpoint for 74-1 and 74-2 is above the RHRS design pressure.
The ACI for flow control valves (FCV-74-1 and FCV-74-2) provides backup overpressure protection. A relief valve located on the suction line from the RCS hot leg provides the primary protection from inadvertent overpressurization. This valve is located inside containment, downstream of 74-1 and 74-2, and relieves to the pressurizer relief tank should pressure reach 450 pounds per square inch gauge (psig). Additionally, the automatic closure function of the letdown valves is not used during plant heatup. General operating instructions require the operator to manually close 74-1 and 74-2 before RCS temperature exceeds 212 degrees Fahrenheit and approximately 400 psig.
The ACI setpoint is set at 700 psig to ensure the RHRS is isolated before pressure reaches 750 psig. The setpoint is set at the maximum allowable value to minimize the potential for inadvertent isolation of the RHRS because inadvertent isolation would lead to a complete loss of.RHRS capability. RHRS design pressure is 600 psig.
The American Society of Mechanical Engineers' Code, section III, requires the hydrostatic test pressure to be 1.25 times the system design pressure. Therefore, the RHRS has been tested to withstand a pressure of 750 psig.
Manual valve closure, along with relief valve protection for inadvertent pressure transients, provides adequate assurance of RHRS integrity. The ACI is a backup feature for overpressure protection.