ML20030B301
| ML20030B301 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 07/30/1981 |
| From: | Curtis N PENNSYLVANIA POWER & LIGHT CO. |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, PLA-893, NUDOCS 8108060308 | |
| Download: ML20030B301 (7) | |
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@ Pennsylvania Power & Light Company Two North Ninth Street + Allentown, PA 18101 + 215 I 770L5151 Norman W. Curtis Vice President-Engineering & Construction-Nuclear 215 / 770-5381
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July 30, 1981 u
Mr. Boyce H. Grier
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Director, Region I
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King of Prussia, PA 19406
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s fG SUSQUEHANNA STEAM ELECTRIC STATION INTERIM REPORT OF A POTENTIAL DEFICIENCY INVOLVING THE DESIGN AND WELDING OF PRIMARY CONTAINMENT VENT PIPE (DOWNCOMER)
BRACING ERs 100450/100508 FILES 821-10/900-10 PLA-893
Dear Mr. Grier:
This letter serves to provide the Commission with an interim report of a potential deficiency relating to the discovery of nonconforming welds and inadequate design in the downcomer bracing system. A potentially reportable deficiency was originally reported under the provisions of 10 CFR 50.55(e) in a telephone call between M1. R. Schwan (PP&L) and Mr. L. Narrow (NRC. Region I) on June 3, 1981. The verbal report consisted of a description of only the nonconforming welds for the downcomer bracing as furnished by Industrial Engineering Works. Subsequent investigation of this problem led to the discovery of the other related deficiency involving the design of the bracing system and its inability to accommodate combined seismic and hydrodynamic loads (Phase II loads). The expanded scope of the potential deficiency was reported to Mr. L. Narrot by Mr. A. Sabol of PP&L on June 26, 1981. The information contained in its report is submitted pursuant to the provisions of 10 CFR 50.55(e).
The attachment to this letter contains a descriptior. of the deficiencies, their safety implications, corrective actions taken and planned.
We trust the Commission will find the information forwarded by this letter to be satisfactory. We expect to issue a final report on the deficiency by November, 1981.
Veq tru1 - ivurs, 1
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i N. W. Curtis Vice President-Engineering & Construction-Nuclear 1
8108060308 810730 e
PDR ADOCK 05000387 7
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.S PDR
Mr. Boyce H. Grier July 30, 1981 Attachment cc:
Mr. Victor Stello (15)
Director-Office of Inspection & Enforcement U. S. Nuclear Regulatory Commission Washington, D.C. 20555 Mr. G. Mcdonald, Director (1)
Office of :'anagement Information & Program Control U. S. Nuclear Regulatory Commission Washington, D.C. 20555 Mr. Gary Rhoads U.
S. Nuclear Regulatory Commission P.O. Box 52 Shickshinny, PA 18655
' ATTACHMENT TO PLA-893 1.0 PURPOSE This report provides interim information as required by 10 CFR 50.55(e) subsequent to notification of a potentially reportable deficiency. This deficiency involves downcomer bracing welds and the bracing system design.
2.0 DESCRIPTION
OF DEFICIENCY Th'e containment structure of Susquehanna Steam Electric Station (Units 1 and 2) is provided with a system of primary containment vent pipes, commonly called downcomers. These downcomers, which are illustrated in Figure 1, have a lateral bracing system at elevation 668'-0" which ties together the downcomers and main steam relief valve (MSRV) discharge lines. This sysham, which is shown in Figure 2, is a horizontal truss separated into 4 independent quasrants and anchored to the containment wall. Bracing members are generally 6 inch diameter double extra strong steel pipe, although members bracing the MSRV lines are either W10 x 45 or W10 x 66 rections. Two identifiable deficiencies have developed in association with the downcomer bracing system.
Deficiency #1:
Connections at one end of each 6 inch diameter bracing member have fcur (4) shop welds of the brace to either a 1-1/4 inch or 1-3/4 inch thick connection plate. Design drawing 8856-C-372, Sheet 2, requires these welds tc be fillet welds 5/8 inch by 5 inches long. The welds furnished by Industrial Engineering Works (IEW) of Trenton, New Jersey are of proper length but have throat measurements generally ranging between 1/4 inch and 3/8 inch with most around 1/4 inch. These measurements indicate a nominal weld size varying between 9/32 ano 17/32. These welds are shown in Figure 3.
Deficiency #2:
Upon detection of the first deficiency relating to undersized welds, a review of the complete downcomer bracing system was undertaken to ascertain the scope of the problem.
It was during this review of the bracing system that the second deficiency was discovered. Deficiency #2 is a design related problem concerned with the inability of the present bracing system to accommodate the Phase II combined seismic and hydrodynamic loads. Results of the design review indicate that the bracing system is overstressed at three locations: the downcomer collar plate, the bolted connection between the collar and horizontal connection plate, and the 1-1/4 inch or 1-3/4 inch thick connection plate described in Deficiency #1.
Further analysis by Bechtel project engineering is required to determine the scope of the problem when the effects of the latest hydrodynamic load (Phase III load) definition as obtained from Kraftwerk Union (KWU) are included.
CAUSE The cause for deficiency #1 appears to involve the welding activity at IEW.
Bechtel Project procurement is conducting an investigation of the cause of the undersigned IEW shop welds and will report the results to Bechtel Project engineering.
Page 1 of 5
CAUSE (Continued)
The cause for deficiency #2 appears to reflect upon the bracing design as originally specified by Bechtel. Further review is underway to clarify this apparent design deficiency.
3.0 ANALYSIS OF SAFETY IMPLICATIONS / TECHNICAL EVALUATION Bechtel Project engineering has evaluated both conditions and concluded that they are potentially reportable. The original design load for the bracing connection was 320 kips. This load produces a calculated linear shear stress of 64.0 ksi on the 1/4 inch throat weld furnished by Industrial Engineering Works (Deficiency #1). The ultimate tensile capacity of the E70XX electrodes is 70 ksi. The ultimate shear capacity of these electrodes is 70/ 3 = 40.4 ksi.
Similar problems exist in terms of allowable versus actual stress levels at the three locations described in Deficiency #2.
Project engineering is evaluating the accuracy of this design value of 320 kips using refined analytical methodologies. This re-evaluation includes j
effects of the latest hydrodynamic load definition as obtained from KWU
' Phase III loads).
g 4.0 CORRECTIVE ACTIONS TAKEN AND RESOLUTION PLAN Deficiency #1 r
The undersized welds have been documented via established project procedures.
NCR-7346 and NCR-7489 for Units.2 and.1, respectively, provide proper controls.
These NCR's were validated on March 13, 1981 and April 6, 1981, respectively.
Project quality assurance issued QAR-F-688 which requested project engineering evaluation of reportability under the provisions of 10 CFR 50.55(e) on April 29, 1981. Project engineering responded on May 28, 1981 and MCAR-1-70 was subsequently issued by project quality assurance on May 29, 1981.
Bechtel Project engineering will evaluate the results of Bechtel Project procurement's investigation into the cause of the IEW undersize shop welds.
Bechtel Project construction is performing an investigation of other shop l
welds on materials supplied by IEW to the jobsite. This investigation I
will include the downcomer bracing and a survey of other materials. The investigation will be completed and forwarded to project engineering for evaluation.
Deficiency #2 Bechtel Project engineering is completing the refined analysis described in section 3.0.
The results of this analysis will be used to prepare a plan for corrective action. The design fixes established as a result of the analysis will be discussed in the final report which will be issued
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by November, 1981. The final report will include a discussion o:. tia resolution of both deficiencies outlined in this interim report.
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