ML20043B571

LER 90-008-00:on 900425,safety Features Actuation Sys Level 1 Actuation Occurred,Resulting in Trip of Containment Radiation Monitors.Caused by High Radiation Fields While Lifting Core Support Assembly.Mod initiated.W/900525 Ltr

ML20043B571
Person / Time
Site:	Davis Besse
Issue date:	05/25/1990
From:	Storz L, Stotz J TOLEDO EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-008, NP33-90-009, NUDOCS 9005300236
Download: ML20043B571 (4)

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' TOLEDO. OHIO 4DO S 03D1 Log No.: BB90-00700 l' May 25, 1990 NP33-90-009 l o '- Docket No. 50-346 *

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United States Nuclear Regulatory Commission r Document Control Desk  :

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P LER 90-008 Davis-Desse Nuclear Power Station, Unit flo. 1 Date of Occurrence - April 25, 1990 I

Enclosed please find Licensee Event Report 90-000 which is being written to provide 30 days ncvification of the subject occurrence. This report is being submitted in accordance with 10CFR$0.73(a)(2)(iv).

Yours truly, s ?f Louis F. Storz Plant Manager Davis-Besse Nuclear Power Station LFS/p1f Enclosure cc: Mr. A. Bert Davis Regional Administrator USNRC Region III Mr. Paul Byron DB-1 NRC Sr. Resident Inspector 9005300236 900523 h

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Unnecessary SFAS Level 1 Actuation During Core Support Assembly Move

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On April 25, 1990, at 2043 hours0.0236 days <br />0.568 hours <br />0.00338 weeks <br />7.773615e-4 months <br />, the Station experienced an SFAS Level 1 actuation. The Core Support Assembly (CSA) was being returned to the reactor vessel and was lifted higher than planned. This caused radiation fielde high enough to trip two of the nearby Containment SFAS Radiation Monitors (RE2004 and 2005) which completed the logic for the SFAS actuation. Vith the reactor defueled, there is no Technical Specification requirement for SFAS to be operable. The design of the system does not allow the system to be de-energized, when not required, without causing an output logic signal to move equipment to their safety position. The radiation fields were higher than expected, but there were no personnel overexposures.

The event was initially determined to be part of a planned evolution and therefore not reportable. Subsequent evaluation concluded that although the CSA move was a planned evolution, the SFAS actuation was not. The NRC was notified vin the EMS ut 1830 hours0.0212 days <br />0.508 hours <br />0.00303 weeks <br />6.96315e-4 months <br /> on May 2, 1990, per 10CFR50.72(b)(2)(li).

This LER is being submitted per 10CFR50.73(a)(2)(iv).

Previously LER 90-007 committed Toledo Edison to determining the need for a modification or procedural strategies to prevent unnecessary ESF actuation.

These actions were not yet in place to prevent this event.

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' Description'of Occurrences ;3 On April 25, 1990, at 2043 hours0.0236 days <br />0.568 hours <br />0.00338 weeks <br />7.773615e-4 months <br />, during the transfer of the Core Support Assembly (CSA) from the deep end of the refueling. canal back into the reactor-vessel, the. Station experienced a Safety Features Actuation System (SFAS-JE)

Level 1 actuation. It occurred when two of the Containment SFAS Radiation  ;

Honitors, RE2004 and RE2005, exceeded their trip setpoints when the.CSA transfer caused higher radiation fields than expected. Vith the reactor i defueled, there was no Technical Specification requirement for SFAS to be  ;

operable. The SFAS radiation monitors vere in their normal location for l< refueling activities with setpoints appropriate for that activity.

l All actuated equipment was returned to its pretrip status by 2050 hours0.0237 days <br />0.569 hours <br />0.00339 weeks <br />7.80025e-4 months <br />.

L The event was initially determined to be a planned evolution that did not require reporting. The possibility of an SFAS actuation had been. discussed before the CSA move was started. Operators were prepared to make any necessary restorations. Subsequent reassessment on May 2, 1990, concluded c

that although the movement of the CSA was a planned evolution, the SFAS L actuation was not an inevitable outcome of the evolution.

This was reported to the NRC via ENS at 1836 hours0.0213 days <br />0.51 hours <br />0.00304 weeks <br />6.98598e-4 months <br /> on May 2, 1990, per-

{ 10CFR50.72(b)(2)(1) as an automatic actuation of an Engineered Safety Feature E y s t t ?,SF) .

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I ibis is being reported as an LER per 10CFR50.73(a)(2)(iv) for the same reason.

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f Apparent Cause of Occurrence i l, The SFAS actuation occurred because the radiation fields were higher than l expected. The precautions taken for the expected fields to prevent the rad monitor actuations were inadequate for the higher fields encountered. The fields were higher because the CSA was lifted higher for this move than it was when it was removed in March 1990. The lift specialist was trying'to assure that he cleared'some materials on the floor of- the refueling canal that were not there when the CSA vas Temoved.

p The design of SFAS does not permit the cabinets to be de-energized, when not required by Technical Specifications, without causing some of the actuated equipment to move to its safety position.

l Analysis of Occurrence:

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' Vith the reactor defueled, there are no Technical Specification requirements for SFAS to be operable. There are no credible accident scenarios in this condition for which SFAS protection is required. The lift was being closely monitored by Radiological Controls personnel who reacted properly when the l c now u.. .u s oao isse o e 4 saa 4ss

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g; ,,j radiation level rose above what was expected. Although the personnel m' exposune were higher than expected, there vere no 10CFR20 limit ~

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overexposurev nor were any Station administrative levels exceeded.- -

Corrective Action to Prevent Recurrence Toledo Edison previously committed in LER 90-007 to determine the need for'a.

modification and/or procedural strategies to protect against unnecessary ESF :

actuations. 'These actions were not yet in place to prevent this event. '

Failure Data: '

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Previous unnecessary SFAS actuations were reported in LERs90-006 and 90-007.

U These LERs also involved actuations of SFAS vhen the reactor-vas defueled, i

L REPORT NO.: NP33-90-009 PCAO NO. 0361.  :

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