05000346/LER-1980-091-01, /01T-0:on 801223,during Analysis Per IE Bulletin 80-11,design for Block Wall Between Control Room & Stairway AB-1 Found to Be Less Conservative than Assumed in Fsar. Caused by Outdated Analytical Const Methods

/01T-0:on 801223,during Analysis Per IE Bulletin 80-11,design for Block Wall Between Control Room & Stairway AB-1 Found to Be Less Conservative than Assumed in Fsar. Caused by Outdated Analytical Const Methods

ML19351F519
Person / Time
Site:	Davis Besse
Issue date:	01/06/1981
From:	Mekbel C TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19351F518	List: 05000346/LER-1980-091, Forwards LER 80-091/01T-0 05000346/LER-1980-091-01, /01T-0:on 801223,during Analysis Per IE Bulletin 80-11,design for Block Wall Between Control Room & Stairway AB-1 Found to Be Less Conservative than Assumed in Fsar. Caused by Outdated Analytical Const Methods
References
IEB-80-11, LER-80-091-01T, LER-80-91-1T, NUDOCS 8101130417
Download: ML19351F519 (3)

LER-1980-091, /01T-0:on 801223,during Analysis Per IE Bulletin 80-11,design for Block Wall Between Control Room & Stairway AB-1 Found to Be Less Conservative than Assumed in Fsar. Caused by Outdated Analytical Const Methods

Event date:
Report date:
3461980091R01 - NRC Website

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60 61 DOCKET NUVSER 68 69 EVENT DATE 74 75 REPORT DATE 80 EVENT OESCRIPTION ANO PROSA8LE CONSEQUENCES h o 2 l (NP-32-80-17) On 12/23/80 from the performance of the analysis of concrete block wallsl o

l as required by NRC IE Bulletin 80-11. it was determined that a reportable condition l

l existed. During a seismic event, the block wall between the control room and stair-l o 4 o 5 l vay AB-1 would cause the floor beam above to be overstressed. This design is less l

FTO I conservative than assumed in the FSAR and is reportable per T.S. 6.9.1.8.i.

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, 2 g l in a dynamic instead of a static analysis. Under Facility Change Request 80-277, two I y l struts will be ad Qd to the floor beam.

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TOLEDO ELISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-32-80-17_

DATE OF EVENT: December 23, 1980 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Floor beam at the top of concrete block wall 5107 would be overstressed during a design basis seismic event Conditions Prior to occurrence: The unit was in Mode 1 with Power (NWT) = 1525 and Load (Gross MWE) = 489 Description of Occurrence: While performing the analysis of concrete block walls re-quired by NRC IE Bulletin 80-11, it was determined that during a seismic event, the block wall between the control room and stair AB-1 would cause the floor beam above to be overstressed. This floor beam is attached to the wall and supports a portion of the floor above the control room.

It was determined that this condition was less conservative than assumed in the Final Safety Analysis Report (FSAR) and is being reported under Technical Specification 6.9.1.8.1.

The NRC On-Site Inspector was notified at 0925 hours0.0107 days <br />0.257 hours <br />0.00153 weeks <br />3.519625e-4 months <br /> on December 21, 1980.

Designation of Apparent Cause of Occurrence: This finding is due to a change in the cnalytical methodology used by the architect / engineer since the walls were designed in the early 1970s. Using the methods applicable at that time, the floor beam would be acceptable as built. However, the change in the method treats wall section proper-ties and seismic floor response inputs differently and is a dynamic instead of static cualysis. Under the new methods, the floor beam design is deficient.

Analysis of Occurrence: There was no danger to the health and safety of the public cr to station personnel. The floor beam in question is only overstressed during a maximum probable earthquake. During all other postulated unit operating conditions, the stresses in this beam are within allowables.

A preliminary review of the portion of the floor above the control room supported by this beam has been made. The results are not conclusive but indicate there is a poten-tial that a portion of the floor above may undergo some structural distress. A more detailed analysis would take three months to perform. The modification to correct this condition consists of two small struts which could be installed in about two weeks. Therefore, in the interest of taking the most expeditious approach, Toledo Edison has decided to make the modification at this time witho~ut proceeding with further analytical effort.

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TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-32-80-17 PAGE 2

Corrective Action

Two struts will be added to the floor beam under Facility Change Request 80-277.

Failure Data: There have been no previously similar reported occurrences.

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