05000346/LER-1980-009-03, /03L-0:on 800122,discovered That NI-7 Indication on Computer Group 38 Was Reading Less than Heat Balance Power,Putting NI-7 Below Instrumentation Operability Limit Line.Caused by Extremely Tight Calibr Band at 100% Power

/03L-0:on 800122,discovered That NI-7 Indication on Computer Group 38 Was Reading Less than Heat Balance Power,Putting NI-7 Below Instrumentation Operability Limit Line.Caused by Extremely Tight Calibr Band at 100% Power

ML19296C575
Person / Time
Site:	Davis Besse
Issue date:	02/15/1980
From:	Werner B TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19296C573	List: 05000346/LER-1980-009, Forwards LER 80-009/03L-0 05000346/LER-1980-009-03, /03L-0:on 800122,discovered That NI-7 Indication on Computer Group 38 Was Reading Less than Heat Balance Power,Putting NI-7 Below Instrumentation Operability Limit Line.Caused by Extremely Tight Calibr Band at 100% Power
References
LER-80-009-03L, LER-80-9-3L, NUDOCS 8002260673
Download: ML19296C575 (2)

LER-1980-009, /03L-0:on 800122,discovered That NI-7 Indication on Computer Group 38 Was Reading Less than Heat Balance Power,Putting NI-7 Below Instrumentation Operability Limit Line.Caused by Extremely Tight Calibr Band at 100% Power

Event date:
Report date:
3461980009R03 - NRC Website

text

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LVENT DATE 14 15 HEPQH T DAT E SJ EVENT DES:RIPil0N AND PRO 3AGLE CCCECUENCES h

,a 2 l On January 22, 1980 at about 1315 hours0.0152 days <br />0.365 hours <br />0.00217 weeks <br />5.003575e-4 months <br />, an operator noticed that NI-7 indication on l o!3 l computer Group 38 was reading less than the heat balance power, putting NI-7 below

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l the NI operability Limit line of ST 5030.01, Reactor Protection Systen Daily Heat l

9 s l 5 1ance Check.

NI-7 was declared inoperable at 1328 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.05304e-4 months <br />.

The unit entered the o

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3.3.1.1.

There was no danger to the public or station per-l 917 l sonnel.

Ilea t balance power was less than 100*: at all times and itss than the other l

~ 0 a j indicated power of NIs 5, 6, and 8.

(NP-33-80-12) l d 9 60 SYSTE M CAU5i

CAUSE

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CAUSE OLSCNPTION AND CORRECTIVE ACTIONS h 2 o l The cause is an extremely tight calibration band at 100% power (see LER NP-32-79-15) l i

i l coupl ed wi th a + 0. 47, variat ion in indica ted power and heat balance power due to nor-l

[ mal plant control variations.

N1-7 was recalibrated per ST 5030.11, checked per l

,3 l ST 5030.01, and declared operable at 1430 hours0.0166 days <br />0.397 hours <br />0.00236 weeks <br />5.44115e-4 months <br /> on January 22, 1980. The tripped j

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condition was cleared, and the unit was taken out of the action statement.

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TOLEDO EDISON COMPANY DAVIS-BESSE SUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-80-12 DATE OF EVENT: January 22, 1980 FACILITY: Davis-Besse Unit 1 NI-7 Reactor Protection System (RPS) Channel 4 out of IDENTIFICATION OF OCCIIRRENCE:

calibration The unit was in Mode 1, with Power (MWT) = 2765.5 Conditions Prior to Occurrence:

and Load (Gross MWE) = 921.

On January 22, 1980 at about 1315 hours0.0152 days <br />0.365 hours <br />0.00217 weeks <br />5.003575e-4 months <br />, it was noted Description of Occurrence:

the NI-7 indication on computer Group 38 was reading less than the heat balance that line of ST 5030.01, RPS Daily power, putting NI-7 below the NI operability limitAfter two subsequent computer updates of Heat Balance Check.

showed NI-7 indication less than the heat balance power, NI-7 was declared inopera-ble at 1328 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.05304e-4 months <br />. This placed the unit into the Action Statement 2 of Table 3.3.1 of Technical Specification 3.3.1.1, which required the channel to be tripped within 1336 hours0.0155 days <br />0.371 hours <br />0.00221 weeks <br />5.08348e-4 months <br />.

RPS Channel 4 was place d in a tripped condition at one hour.

This occurrence is due to the extremely Designation of Apparent Cause of Occurrence:

100% power (see LER NP-32-79-15),

tight calibration band that we are limited to at coupled with the approximately 10.4% variation in indicated power and heat balance For the NI calibration to remain with-power due to normal plant control variations.

in the operating band for any length of time with the inherent variations in power, would require alignment accuracies greater than we are capable of at present.

There was no danger to the health and safety of the public Analysis of Occurrence:

or to station personnel.

Heat balance power was less than 100% at all times and less than the indicated power of NIs 5, 6, and 8.

Corrective Action

NI-7 was recalibrated per ST 5030.11, RPS Power Range Calibration, checked satisfactorily per ST 5030.01, RPS Heat Balance Check, and declared operable at 1430 hours0.0166 days <br />0.397 hours <br />0.00236 weeks <br />5.44115e-4 months <br /> on January 22, 1980. The tripped condition was cleared, and the unit was taken out of the action statement.

There have been no previous similar reportable occurrences.

Failure Data:

LER #80-009