05000346/LER-1979-031-03, /03L-0 on 790219:two Computer Points Were Not Updating.Caused by Procedural Deficiency & Random Failures of Bailey Computer Sys.Surveillance Test Has Been Revised

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/03L-0 on 790219:two Computer Points Were Not Updating.Caused by Procedural Deficiency & Random Failures of Bailey Computer Sys.Surveillance Test Has Been Revised
ML19259B797
Person / Time
Site: Davis Besse Cleveland Electric icon.png
Issue date: 03/19/1979
From: Marley J
TOLEDO EDISON CO.
To:
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19259B794 List:
References
LER-79-031-03L, LER-79-31-3L, NUDOCS 7903230168
Download: ML19259B797 (3)
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LER-1979-031, /03L-0 on 790219:two Computer Points Were Not Updating.Caused by Procedural Deficiency & Random Failures of Bailey Computer Sys.Surveillance Test Has Been Revised
Event date:
Report date:
3461979031R03 - NRC Website
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text

NRC FORM 366 (7-77)

LICENSEE EVENT REPORT CONTROL BLOCK: l l

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7 8 9 LICENSEE CODE 14 15 LICENSE NuYSER 25 26 LICENSE TYPE J0 57 CAT 68 CON'T Ll@

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8 60 61 DOCKET NUVBER 68 69 EVENT D ATE 74 75 REPORT DATE 80 3o R EVENT DESCRIPTION AND PROB ABLE CONSEQUENCC.S h o 2 i At 0215 hours0.00249 days <br />0.0597 hours <br />3.554894e-4 weeks <br />8.18075e-5 months <br /> and again at 1320 hours0.0153 days <br />0.367 hours <br />0.00218 weeks <br />5.0226e-4 months <br /> on 2/19/78, while in the Action Statement of l

Technical Specification 4.2.1 requiring manual calculation of Axial Power Imbalance }

,g,3, (AxPI), it was noted that two of the computer points being used in the calculation, l

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l due to the process computer alarm being inoperable, were not updating. An alternate loIsI o 6 l procedure for AxPI calculation was then performed. There was no danger to the health A review of the data indicated that l

l o 17 ) I and saf ety.of the public or station personnel.

the AxPI did not exceed Technical Specification limits.

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40 41 42 43 44 47 33 34 J5 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h l The apparent cause of the occurrence was a procedural deficiency and a random f ailure 1 i

o I of the Bailey Computer System. A modification to Surveillance Test ST 5020.01 has l

3 been written to caution operators that when computer group 38 f ails to update, there l i

l is a possibility that computer points C927 and C928 will also be inoperable.

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DVR 79-041 NAVE OF PREPARER

TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-79-35

'DATE OF EVENT: February 19, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Verification of Axial Power Imbalance failed to satisfy surveillance requirements Conditions Prior to Occurrence: The unit was in Mode 1, with Power (MWT) = 2440, and Load (Gross MWE) = 819.

Description of Occurrence:

On February 19,1979, at 0015 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br />, process computer display Group 38 (tilt, imbalance insertion) on the Control Room cathode ray tube (CRT) was observed to have stopped updating. Group 38 was declared inoperable on February 19, 1979 at 0015 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br />. With Group 38 display inoperable, the axial power imbalance alarm becomes inoperable, thus requiring an increase in the frequency of surveillance requirements per Technical Specification 4.2.1.

Technical Specifica-tion 4.2.1 requires the axial power imbalance to be determined to be within limits once every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> when above 40% of rated thermal power except when the axial power imbalance alarm is inoperable, then calculate the axial power imbalance at least once per hour. The axial power imbalance manual calculation, Surveillance Test ST 5020.01, specifies Section 7.1 is to be performed hourly to satisfy sur-veillance requirements of Technical Specification 4.2.1 when Group 38 is inoperable.

Section 7.1 of ST 5020.01 verifies axial power imbalance by a calculation which utilizes computer points C927 and C928.

Section 7.1 of ST 5020.01 was performed hourly from 0015 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> until 0215 hours0.00249 days <br />0.0597 hours <br />3.554894e-4 weeks <br />8.18075e-5 months <br /> on February 19, 1979, when it was discovered that computer points C927 and C928 were not updating. With computer points C927 and C928 inoperable, Section 7.1 f ailed to satisfy surveillance requirements for Technical Specification 4.2.1.

Section 7.4 was then performed from 0220 hours0.00255 days <br />0.0611 hours <br />3.637566e-4 weeks <br />8.371e-5 months <br /> to 0720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br />, satisfying surveillance require-ments for Technical Specification 4.2.1.

Section 7.1 of ST 5020.01 was inadvertently performed from 0820 hours0.00949 days <br />0.228 hours <br />0.00136 weeks <br />3.1201e-4 months <br /> until 1220 hours0.0141 days <br />0.339 hours <br />0.00202 weeks <br />4.6421e-4 months <br /> when it was discovered that computer points C927 and C928 were not updating.

Section 7.3 of ST 5020.01 was then performed at 1320 hours0.0153 days <br />0.367 hours <br />0.00218 weeks <br />5.0226e-4 months <br /> and continued to be per-formed hourly until Group 38 was declared operable on February 20,1979 at 0002 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, satisfying surveillance requirements for Technical Specification 4.2.1.

Surveillance requirements for Technical Specification 4.2.1 were therefore not satisfied from 0115 hours0.00133 days <br />0.0319 hours <br />1.901455e-4 weeks <br />4.37575e-5 months <br /> to 0215 hours0.00249 days <br />0.0597 hours <br />3.554894e-4 weeks <br />8.18075e-5 months <br /> and from 0820 hours0.00949 days <br />0.228 hours <br />0.00136 weeks <br />3.1201e-4 months <br /> to 1220 hours0.0141 days <br />0.339 hours <br />0.00202 weeks <br />4.6421e-4 months <br /> on Febru-ary 19,1979 due to Section 7.1 of ST 5020.01 being performed with bad data result-ing from inoperable computer points.

Group 38 was declared operable on February 20, 1979 at 0002 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.

r Designation of Apparent Cause of Occurrence:

The apparent cause of the occurrence was procedural deficiency. A random hardware f ailure in the Bailey Computer System caused Group 38 and canputer points C927 and C928 to stop updating.

ST 5020.01 calls for Section 7.1 to be used to satisfy surveillance requirements of Technical Specification 4.2.1 when Group 38 is inoperable. Unaware that the hardware f ailure LER #79-031

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TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE PAGE 2 SUPPLEMENTAL INFORMATION FOR LER NP-33-79-35 had also caused computer points C927 and C928 to be inoperable, Section 7.1 was performed until the discovery of the inoperable camputer points. The procedure (ST 5020.01) was deficient in that there was no warning or caution that when Group 38 fails to update, there is a possibility that computer points C927 and C928 will not be operable.

Analysis of Occurrence: There was no danger to the health and safety of the public or to unit personnel. A review of hourly axial power imbalance data taken from the computer daily log sheets, indi:ated that the axial power imbalance did not exceed Technical Specification limits during the occurrence.

Corrective Action

Upon the discovery of the inoperable computer points C927 and C928 at 0215 hours0.00249 days <br />0.0597 hours <br />3.554894e-4 weeks <br />8.18075e-5 months <br /> on February 19, 1979, Surveillance Test ST 5020.01, Section 7.4 was performed instead of Section 7.1 of ST 5020.01 in order to satisfy Technical Specification 4.2.1.

Upon the discovery of the inoperable computer points at 1320 hours0.0153 days <br />0.367 hours <br />0.00218 weeks <br />5.0226e-4 months <br /> on February 19, 1979, Section 7.3 of ST 5020.01 was performed ~and was con-tinued to be performed throughout the remainder of the inoperability of Group 38.

A modification to ST 5020.01, T-3538, has been written to caution operators that when Group 38 fails to update, there is a possibility that computer points C927 and C928 will also be inoperable.

Failure Data: There has been one prior occurrence of the failure to satisfy axial power imbalance surveil ance requirements, previously reported in Licensee Event Report NP-33-78-136.

LER #79-031

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