ML20206G026
| ML20206G026 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 11/17/1988 |
| From: | Shawn Smith TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 88-15, NUDOCS 8811220004 | |
| Download: ML20206G026 (4) | |
Text
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TENNEOSEE VALLEY AUTHORITY Sequoyah Nuclear Plant Post OffLee Nox 2000 Soddy-Daisy. Tennessee 37379 November 17, 1988 U. S. Nuclear Regulatory Co m lssion Document Control Desk Washington, CC 20555 Gentlement TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAR PLANT UNIT 1 - DOCKET NO.
50-327 - FACILITY OPERATINC LICENSE DPR-?? - SPECIAL REPORT 84-15 The enclosed licensee event report Provides details concerning a posLtLve moderator temperature coef ficient measured on the unit 1, cycle 4 core.
This event is Teported in accordance with Technical SPecLfications 3.1.1.3.
Very truly yours, TENNESSEE VALLEY AUTHORITY f,f
~
S J.
it ont Manager Rnclosure cc (Enclosure):
J. Nelson Crace, Regional Administrator U. S. Nuclear Regulatory Comission Sulte 2900 101 Marietta Street, W Atlanta, Georgia 30323 Records Center Instltute of Nuclear Power Operations suite 1500 1100 Circle 75 Parkway Atlanta, Georgia 30339 NEC Inspector Seguoyah Nuclear Plant h1220004seggg7 I \\
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ADOCK 05000327 P[c An Eqvat Opportunity Employer
SEQUOYAH NUCLEAR PLANT UNIT 1 SPECIAL rep 0RT 88-15 DESCRIPTION OF EVENT On November 9, 1988, with unit 1 in mode 2 (0 percent power, 2235 psis 547 degrees F), a positive moderator temperature coef ficient (MTC) of 0.64X10-5 detta k/k per degrso F was measured in accordance with Restart Test Instruction (RTI)-4, "Boron End point Determination and Isothermal coefficient Measurement".
While restarting unit 1 on its cycle 4 core, Survel11ance Instruction (SI)-139, "Determination of The Moderator Temperature Coefficient" was implemented as required by Technical Specification (TS) SurvoL11ance Requirement (SR) 4.1.1.3.a.31-139 requires the performance of RTI-4 to determine the data necessary for MTC calculation.
Based upon core desi dataandreactivityversustemperaturemeasurements,anMTCof0.64X10gn delta k/k per degree F was determined to exist for the all rods out (ARO),
l hot zero rated thermal power, beginning of cycle life (BOL) condition.
Upon determination of a positive MTC, SI-139 further tequires that the rod withdrawal limits necessary to ensure a negative MTC as required by TS 3.1.1.3 are calculated according to Tachnical Instruction (TI)-42, "Negative Moderator Temperature Coefficient Maintenance Calculation." These withdrawal limits are shown on the enclosed figure and have been included in TI-28, "Curve Book," revision 10 for operator reference.
In addition, caution ordet number 1-88-1555 has been placed on the unit 1 control room board to remind the operators of the withdrawal limits.
CAUSE OF EVENT The cause of the unit 1 cycle 4 BOL positive MTC was a premature shutdown of the unit in August 1985 because of concerns with 10 CFR 50.49, at which time it was decided to proceed with the cycle 4 fuel loading. This premature shutdown allowed the approximately two-thirds core which remained in the cycle 4 core to provide an additional excess reactivity.
ANALYSIS OF EVENT As a result of the calculated positive MTC, a special report is required by TS action 3.1.1.3.a.3 and 6.9.2.
Operations within the shown rod withdrawal limits ensures a negative MTC at all times which gives a negative reactivity change with increasing reactor coolant temperature, thus assuring that the core response remains bounded by the accident analysis.
Current calculations indicate that after 70 effective full power days (less than 2100 MWD /MTU burnup), an MTC of
-1.0110-5 delta k/k per degree F will be achieved and operation within the action statement can be terminated.
i CORRECTIVE ACTION Rod withdrawal limits have been estabilched and made available to the operator.
In addition, caution order number 1-88-1555 has been established to remind the operator of these limits.
These will remain affect until a negative NTC is obtained due to core burnup.
ADDITIONAL INFORMATI0W There has been one prevlous special report on a positive MTC - SQR0-50/328 -
Special Report 81-8 COMMITMENTS Nono l
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