IR 05000267/1981005
| ML19347F616 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 04/06/1981 |
| From: | Randy Hall, Tapia J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML19347F613 | List: |
| References | |
| 50-267-81-05, 50-267-81-5, IEB-80-11, NUDOCS 8105220118 | |
| Download: ML19347F616 (3) | |
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U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT
REGION IV
Report No. 50-267/81-05 Docket No. 50-267 License No. DPR-34 Licensee:
Public Service Company of Colorado Post Office Box 840 Denver, Colorado 80201 Facility Name:
Fort St. Vrain Nuclear Generating Station Inspection at:
Fort St. Vrain Site, Platteville, Colorado Inspection Conducted: March 16-18, 1981 Inspector:.d'
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J. I. Tapia, Reactor Inspector, Engineering and Materials 06td Section
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Approved: p e
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R. E. Hall, Acting Chief, Engineering and Materials Section 06t(
Inspection Summary:
Inspection conducted durino March 16-18,1981 (Report No. 50-267/81-05)
Areas Inspected: Special, announced inspection involving review of the licensee's
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response to IE Bulletin No. 80-11, " Masonry Wall Design."
The inspection involved seventeen inspector-hours on site by one NRC inspector.
Results:
In the area inspected, one violation was found in the area of operability evaluation (violation - failure to provide prompt notification of operability evaluation - paragraph 2).
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DETAILS
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Persons Contacted
R. A. Gunnerson, Structural Engineer, PSC
- Denotes attendance at the exit interview.
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2.
Response to IE Bulletin No. 80-11, " Masonry Wall Design" The licensee response to IE Bulletin No. 80-11. " Masonry Wall Design,"
was addressed during this inspection.
The inspection included observation of completed wall modifications, selective review of re-evaluation criteria, j
and specifically, a review of the system operability evaluations required
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to be perfonned for those systems associated with masonry walls found to
be structurally inadequate.
As a result of the re-evaluation of sixty-five masonry walls associated with safety-related equipment, sixteen walls were identified as not being capable of withstanding the wall inertia and attachment loads during the Safe Shutdown Earthquake without exceeding the allowable re-evaluation criteria stresses.
It was shown that the sixteen walls would exceed the maximum allowable tension stress in flexure.
In order to increase the moment capacity of the walls, steel bar straps were installed on both sides of the wall using through-wall bolted round bar stock.
The design of the area of steel required for the bar straps included the conservative assumption that only the bars would take the resulting seismic moment.
This assumption excluded the contribution of the wall and as such did not include a check for exceeding the maximum allowable compression stress in flexural failure.
This analysis was performed during this inspection by the NRC inspector and it was determined that, for the seismic moments
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resulting from the re-evaluation,- the maximum allowable compression stress would not be exceeded.
Twelve of the sixteen walls requiring.the instal-
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lation of bar straps were observed during the inspection.
It was noted that in one instance the electrical conduit attached to the masonry wall was oriented such that it had the potential to impart an eccentric vertical load under seismic loading.
The licensee's analyses had not included a determination of the value of the eccentric vertical load to assure that the maximum allowable eccentric load specified in Section 12.6 of the ACI Report No. 67-23, " Concrete Masonry Structures - Design and Construction,"
had not been exceeded.
The licensee representative verbally committed to perform this evaluation for the wall observed and for any other walls exhibiting eccentric vertical load conditions.
The attachment of the elec-trical conduit to the masonry walls was discussed with the licensee repre-
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sentatives.
From those discussions, the specific method of attachment
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could not be determined.
It was the opinion of the licensee representatives that the attachments were prcbably of the expansion shield type. The-2-I
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licensee representatives verbally committed to define the method of attachment and to perform a load test of representative attachments for the purpose of verifying that the attachments are capable of withstanding the horizontal and vertical seismic loadings defined in Site Document Control Center Procedure No. 011, issue 3, " Pipe Support Analysis Procedure." Additionally, the licensee representatives verbally committed to review the forty-one walls originally deemed nonsafety-related for the purpose of assuring (0 pen Item that no safety-related electrical conduit is attached to the walls.
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Through further discussions and from the review of the supporting data to the licensee's response to the IE Bulletin No. 80-11, it was deter-
mined by the NRC inspector that the licensee had not described those systems associated with the sixteen walls found to be structurally inadequate.
There was no analysis of system operability performed as required by the IE Bulletin.
Additionally, and contrary to the Technical Specification requirement in Section 7.5.2.a.9, the condition requiring remedial action to prevent the existence of an unsafe condition with respect to the performance of masonry wall structures was not promptly reported to the NRC.
The failure to define and analyze system operability for the structurally inadequate rasonry walls had the undefined and unreported potential to clace the licensee in a situation where a Technical Specification Limiting condition for Operation would be exceeded withoutsatisfying the appropriate Action Statement.
This represents a measurable degradation in the safety of operations and is therefore a violation.
3.
Exit Interview The NRC inspector met with the licensee representative denoted in paragraph 1 at the conclusion of the inspection.
The NRC inspector summarized the scope and findings of the inspection.
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