ML20052G768
| ML20052G768 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 09/08/1981 |
| From: | Oprea G HOUSTON LIGHTING & POWER CO. |
| To: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| Shared Package | |
| ML20052G764 | List: |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, ST-HL-AE-722, NUDOCS 8205180660 | |
| Download: ML20052G768 (6) | |
Text
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The Light Company n, i.,,, ueisi,a n,-
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.1~m m uusen September 8, 1981 ST-HL-AE-722 SFH: V-0530 Mr. Karl Seyfrit Director, Region IV Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76012
Dear Mr. Seyfrit:
South Texas Project Units 1 & 2 Docket Hos. STN 50-498, STN 50-499 Beam to Column Connection Design in the Reactor Containment Building On September ?_4, 1980, pursuant to 10CFR50.55(e) Houston Lighting & Power Company notified your office of an item concerning the Beam to Column Connection Design in the Reactor Containment Building. Our final report is attached.
If there are any questions, please contact Mr. Michael E. Powell at (713) 676-8592.
Very truly yours, o
G. W. Oprea, J r.
Executive Vice President RRH/amj Attachment 820518066d
Irons in Lightingh Power Company cc:
J. H. Goldberg September 8, 1981 J. G. Dewease ST-HL-AE-722 1
D. G. Barker SFN: V-0530 C. G. Robertson Page 2 Howard Pyle R. L. Waldrop H. R. Dean D. R. Beeth J. D. Parsons J. W. Williams J. W. Briskin J. E. Geiger STP RMS H. S. Phillips (NRC)
J. O. Read (Read-Poland, Inc.)
M. D. Schwarz (Baker & Botts)
R. Gordon Gooch (Baker & Botts)
J. R. Newman (Lowenstein, Newman, Reis, & Axelrad)
Director, Office of Inspection & Enforcement Nuclear Regulatory Commission Washington, D. C. 20555 R. L. Range /G. W. Muench Charles Bechhoefer, Esquire Central Power & Light Company Chairman, Atomic Safety & Licensing Board P. O. Box 2121 U. S. Nuclear Regulatory Commission Corpus Christi, Texas 78403 Washington, D. C.
20555 R. L. Hancock/G. Pokorny Dr. James C. Lamb, III City of Austin 313 Woodhaven Road P. O. Box 1088 Chapel Hill, North Carolina 27514 Austin, Texas 78767 J. B. Poston/A. vonRosenberg Mr. Ernest E. Hili City Public Service Board Lawrence Livermore Laboratory P. O. Box 1771 University of California San Antonio, Texas 78296 P. 0. Box 808, L-46 Livermore, California 94550 Brian E. Berwick, Esquire William S. Jordan, III Assistant Attorney for the State of Texas Harmon & Weiss P. O. Box 12548 1725 I Street, N. W.
Capitol Station Suite 506 Austin, Texas 78711 Washington, D. C.
20006 i
Lanny Sinkin Citizens for Equitable Utilities, In.c.
Citizens Concerned About Nuclear Power c/o Ms. Peggy Buchorn 5106 Casa Oro Route 1, Box 1684 San Antonio, Texas 78233 Brazoria, Texas 77422 Jay Gutierrez, Esquire Hearing Attorney Office of the Executive Legal Director U. S. Nuclear Regulatory Commission Washington, D. C.
20555 Revision Date 7-28-81
FINAL REPORT CONCERNING BEAM TO COLUMN CONNECTION DESIGN IN THE REACTOR CONTAINMENT BUILDING
SUMMARY
The design of the structural steel inside the Reactor Containment Building has been determined to be reportable under 10CFR50.55(e).
Although a substantial safety hazard has not been identified to date, reverification of calculations and modifications will be required to assure compliance with project criteria. Concerns were first identified to your office in October,1978 and Houston Lighting & Power Company (HL&P) committed to a reverification program. As this program progressed, problems in addition to those discussed in late 1978 were found. Thus, HL&P provided notification to your office in September, 1980 of these additional problems. As of this date, the program is in the final stages of implementation and this Final Report is being submi tted. The remaining actions are:
Finalization of Specific Design Loads November 15, 1981 Completion of Reanalysis January 9,1982 Completion of Redesign / Modification April 17, 1982 Effort Completion of Redetailing June 1,1982 Issuance of Drawings for Construction September 1,1982 DESCRIPTION OF THE INCIDENT On September 24, 1980, pursuant to 10CFR50.55(e), HL&P identified further concerns related to a previously closed item regarding the Reactor Containment Building (RCB) Structural Steel Beam to Column Connection Design.
Originally, on October 25, 1978, HL&P had notified your office of an item involving the failure of the designer to properly consider the application of certain postulated loads in the RCB Internal Structural Steel beam design for the South Texas Project (STP). Further investigation of design calculations revealed numerous examples of design errors involving the improper consideration of loads, loading r
combinations, allowable stresses and design inputs. Accordingly, on l
November 27, 1978, HL&P notified the NRC that this item was considered to be reportable.
Subsequently, in HL&P's first interim report on this item in December,1978, a detailed description of all findings to that point was i
provided.
For the ultimate resolution and closure of this deficiency, i
.certain commitments were made for a plan of action,. including the following:
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1 (1) A detailed investigation of the specific findings reported at that time, (2) To perform a complete reverification of all RCB structural steel calculations with correction of calculations as neces-sary, and to modify any members whose design was found to be inadecuate.
Investigations required under Item (1) above were performed during the early part of 1979 and a final report was provided on this defi-ciency in June,1979.
In this activity, the affected calculations were corrected without the necessity for changes to the design itself.
Subsequently, pursuant to the commitment identified as Item (2) above, the designer has been involved in an extensive program to:
(a) define and refine loads and loading conditiens for the RCB Internal Structural Steel, (b) investigation of original design calculation, (c) reanalysis of substantial portions of the structures, and (d) identifi-cation of certain required design changes.
During the course of this reverification, other significant design errors were identified, involving as before, the omission or misapplication of design loads.
In nunerous instances it has been determined that the correction of these errors would result in modification of the original design in order to ensure that design allowables will not be exceeded.
Therefore, HL&P notified your office on September 24, 1980, that the reverification effort had identified design problems for the same structural steel but of a nature not previously discussed in the earlier report.
Our report of October 24, 1980 provided the description of the new problems.
CORRECTIVE ACTION The corrective action for this concern has been our commitment of a reverification program that confirms that the design of the RCB structural steel conforms to the design criteria and to correct any errors.
A special structural design team has been cre3ted and charged with the responsibility for conducting a complete review and reanalysis of the RCB Internal Structural Steel.
This special review team is also charged with the responsibility of performing the modifications and the redetailing required to bring the original design into conformance with project design criteria. The reanalysis performed by this special structural design team will also be required to be design verified in accordance with project procedures.
l The following paragraphs provide a discussion of the problems and i
actions being taken by this reverification program:
1 As the original calculations performed were prepared manually and did not include all design parameters, it was decided that these calculations would not be used in this reverification ef fort, and a complete reanalysis and design would be required. This reanalysis is being executed by using ICES (STRUDL) computer program for all steel framing inside the RCB. All vertical, axial and transverse loads are being J
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t included in the reanalysis in order that the stability of steel framing will be ensured. The reanalysis will also ensure that adequate transfer of loads from the point of application down to the top of containment mat is being provided.
During this reverification process, it was found that previous calculations were adequate for loading in the vertical direction only.
Horizontal components of forces such as Accident Thermal Loads, Seismic Loads, and Reactor Containment Fan Coolers (RCFC) Duct Design Pressure Load were not properly taken into consideration or were assumed to be negligible.
The Accident Thermal Load is a self limiting load, where the magnitude of force is reduced in direct proportion with the freedom of a member to expand. Also, this load increases in direct relation with any increase in the cross sectional area of the structural member.
The RCFC Duct Design Pressure load is applicable to a portion the floors at elevations (-) 2'-0" and 19'-0" only.
Based on the completion of a preliminary analysis, it has been determined that replacement of some existing connections by expansion joints will provide the best solution to qualify the steel framing for Accident Thermal Loads. Location of these expansion joints will be selected in such a way as to i
provide maximum thermal expansion without impairing the stuctural functionality under other design loading conditions.
Since the internal steel columns were designed initially to carry only vertical and local eccentric loads, the horizontal seismic loads will be now transferred to RCB Secondary Shield concrete walls and the concrete floors. Some connections at the interface between steel beams and concrete walls will be required to be replaced by heavier connections to allow for this load transfer and to secure the steel framing to the concrete walls. Also, some interior steel connections in the line of the load transfer will also be replaced with heavier connections.
The RCFC Duct Design Pressure Load is a result of a pressure differential between the Design Accf dent Pressure within the RCB and the Internal RCFC Duct Pressure. This differential pressure acts from the outside direction of the RCFC Duct towards the inside of the Duct. Thus, in order to transfer this load from its point of application to the RCB Secondary Shield concrete wall, some connections will require modification, and some beams will require additional stiffeners or cover plates.
Also, additional bracing may also be required in the high pressure zones.
e RECURRENCE CONTROL As stated earli_r in the report this item of concern was identified through the implementation of a revised design verification progran on the South Texas Project.
This design verification program was initiated as a result of a commitment made by HL&P regarding recurrence control in the first interim report issued on this item.
Details of the design verification program are contained in the Final Report on the Reportable Deficiency Concerning Beam to Column Connections for Unit I which was submitted in June,1979.
SAFETY EVALUATION Detailed calculations have not been performed to determine whether the original RCB Internal Steel framing system design, if lef t uncor-rected would have resulted in a significant safety hazard.
Rather, it is Houston Lighting & Power's intent to correct the design errors to ensure that the final design configuration is in conformance with project criteria.
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