IR 05000346/1979023
| ML19259D603 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 09/14/1979 |
| From: | Danielson D, Yin I NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML19259D599 | List: |
| References | |
| 50-346-79-23, TAC-40076, NUDOCS 7910250155 | |
| Download: ML19259D603 (9) | |
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U.S. NUCLEAR REGULATORY COMMISSION
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OFFICE CT INSPECTION AND ENFORCEMENT
REGION III
Report No. 50-346/79-23 Docket No. 50-346 License No. NPF-3 Licensee: Toledo Edison Company Edison Plaza 300 Madison Avenue Toledo, OH 43652 Facility Name:
F-
- se Nuclear Power Station, Unit 1 Inspection At
- Davis-Besse Site, Oak Harbor, Ohio, the A-E, and the NSSS supplier offices, and the NRC office Inspection Conducted: June 20-22, 1979, at the site; July 2, and August 14-15, 1979, at Bechtel Power Corporation, Gaithersburg, Maryland; and July 3, 1979, at Babcock and Wilcox Company, Lynchburg, Virginia; and September 7, 1979 at the NRC office, Bethesda Ma land Ym% W 9hh7 Inspector:
I. T. Yin Accompanying Personnel:
D. H. Danielson lTN'
9!/4 77 Approved By:
D. H. Danielson, Chief Engineering Support Sectior. 2 Itspection Summary Inspection on June 20-22, July 'z-3, August 14-15, September 7, 1979 (Report No. 50-346/79-23)
Areas Inspected:
Investigation of allegation that thr. steam generator support and pipe restraints were underdesigned. The inspection involved a total of 28 inspector-hours on site, at the A-E's office,at the NSSS's office and at the NRC office by one NRC inspector.
Results: Within the areas inspected, no apparent items of noncompliance or deviations were identified relative to the steam generator support design and installation. Hewever, questions were identified rela'.ive to the design and calculations for the prinary piping system pipe whip restraints.
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DETAILS
Personnel Contacted Site Inspection on June 20-22, 1979 Toledo Edison Company (".ECo)
T. Murrary, Plant Superintendent B. R. Beyer, Assistant Plant Superintendent C. R. Domeck,.;uclear Project Engineer C. T. Daft, Operations QA Manager Engineering Review at Bechtel Power Corporation - Gaithersburg Power Division (B-GPD) on July 2, 1979 TECo C. L. Mekbel, Senior Engineer B-GFD R. Rosenthal, Project Manager M. Malcom, Project Engineer R. Peyton, Engineering Manager E. J. Ray, Licensing Laison Engineer J. T. Vogel, Engineering Supervisor MPR Associates S. J. Weems, Consulting Engineer Engineering Review at Babcock and Wilcox Company (B&W) on July 3, 1979 TECo C. L. Mekbel, Senior Engineer B&W J. T. Willse, Licensing Engineer
} 2 l.b
C. Wills, Component Engineer MPR Associates 5. J. Weems, Consulting Engineer
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Engineering Review at B-GPD on August 14-15, 1979
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TECo C. L. Mekbel, Senior Engineer B-GPD M. Malcom, Project Engineer J. C. Ventura, Assistant Project Engineer J. S. Whiteraft, Engineering Supervisor J. T. Vogel, Engineering Supervisor J. M. Ogle, Engineering Sunarvisor MPR Associates D. G. Strawson, Senior Engineer H. W. McCurdy, Senior Engineer Technical Discussions at NRC office on September 7, 1979 TECo E. C. Novak C. L. Mekbel B-GPD J. Ogle J. T. Vogel J. W. Fay K. Lee F. C. Cheng NRC/ DOR /EB A. Lee NRC/ DOR /0RB4
)2l3 29b D. J. Garner NRC/IE: HQ E. L. Jordan H. Wong
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L,
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NRC/IE: RIII
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D. H. Danielson T. N. Tambling I. T. Yin Functional or Program Areas Inspected 1.
Summary of Investigation An allegation was made to the NRC in June 1979, stating that the Davis-Besse Nuclear Power Station, Unit 1 (D-B1) steam generator supports were underdesigned by serveral orders of magnitude. The alleger desires to remain anonymous and presents his problems through a friend or acquaintance. The alleger refuses to discuss his problems with the RIII stai'. directly. This refusal coupled with the vague allegations made investigation very difficult.
Based on the information provided, on June 20-22, 1979, the RIII inspector observed the installation and arrangement of the steam generator supports and restraints at the site; reviewed drawings and loading distributions on July 2,1979, at Bechtel Power Corporation, Gaithersburg Power Division (B-GPD), and reviewed steam generator support and restraint design and calculations on July 3, 1979, at Babcock and Wilcox Company (B&W), Lynchburg, Virginia.
No apparent deficiencies were identified within the areas reviewed.
Suesequent to the above inspection, the anonymous alleger informed the NRC that the problem was related to the wall to which the supports were attached. Furthermore, the alleger indicated he believed that the supports for the reactor coolant system hot leg piping was incorrect in that a " belt-like" component was improperly placed or improperly designed.
The RIII inspector returned to B-GPD on August 14-15, 1979, to review the alleger's problem based on the expanded but still vague scope of his problems. During his review the inspector identified areas where the provisions for the design of restraints that are required during the LOCA condition were subject to question.
2.
Areas Observed and Findings at the Site on June 20-22, 1979 The inspector observed the condition and general arrangement of the steam generator supports, including (1) upper restraints, (2) the large snubbers installed on the vessel skirt, (3) the vessel skirt, (4) the rigid sliding restraints on the vessel skirt, (5) the skirt lower spider radial plates and (6) the sliding support base and hold down structure assembly. All structure conditions observed appeared to be sound.
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3.
Areas Reviewed and Findings at B-GPD on July 2, 1979
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The inspector reviewed installation drawings and discussed loading magnitudes and conditions and concluded:
(1) the upper restraint method and design appeared to be straight forward, (2) the lower bumper and related structure appeared to be simple and with ample rigidity.
Documents reviewed included:
B-GPD Drawing C-165, Rev. 5, " Containment Internal Structures,
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Steam Generator Foundations, Sheet 1."
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B-GPD Drawing C-167, Rev. 8, " Containment Internal Structures, Steam Generator Foundations, Sheet 3."
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B-GPD Drawing C-178, Rev. 10, " Steam Generator Upper Support, Plan and Sections, Sheet 1."
4.
Areas Reviewed and Findings at B&W on July 3, 1979 The inspector reviewed the (1) upper restraint design, (2) design of the vessel skirt, (3) LOCA loading conditions, (4) SSE loading conditions, and (5) skirt buckling analysis. The review identified that:
a.
The upper restraint is located at the upper tube sheet, one of the most rigid portions on the vessel.
b.
The combined LOCA and SSE effects for the XYZ directions, using a conservative combination method, are within the established allowable stress. The calculated moment of inertia took into consideration the skirt openings, i.e.
(1) 2 pipe penetrations, (2) 1-ISI service entrance hole, and (3) 1-hand hole. The OBE loadings for the skirt were also within the allowable stress.
c.
Based on a simplified column slenderness ratio stress calculation assuming full vertical skirt length and no curving of the plate between skirt openings, the critical loading was within the elastic stress range.
d.
The local high stress areas where the large hydraulic snubbers are bolted onto the vessel skirt, are stiffened with gusset plates welded between all bolts.
e.
A finite element analysis was performed on the lower spider radial plate assembly, where the vessel skirt rests, to ensure overall structural integrity.
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Documents reviewed included:
B&W Report No. 12, Contract No. 620-0014-55, a part of the
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design report, " Stress Analysis of Steam Generator Support Skirt and Attachments for Mechanical Loads," dated April, 1972.
B&W Drawings 151929E, Rev. 5, and 151930E, Rev. 9, " Assembly
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and Detail of Support Skirt."
B&W Drawing 145210E, Rev. 7, " Steam Generator Assembly and
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Detail of Lower Restraint."
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B&W Drawing 170497E, Rev. O, " Steam Generator Lower Restraint Details."
The inspector concluded that no apparent problems existed within the areas reviewed.
5.
Areas Revieweu and Findings at B-GPD on August 14-15, 1979 The inspector reviewed the design functions related to the primary system cold and hot legs. The review identified:
a.
Inconsistant Design '<orce The inspector's review of the LOCA design condition for the primary system cold and hot legs identified on apparent deviation from FSAR commitments for systems inside the containment.
(1) FSAR, Rev. 16, October 1975, Section 3.6.2.5.6., indicated a value of 1.67 was used as the dynamic amplification factor (DAF).
(2) FSAR Staff Question 3.6.7 (October 4, 1974) questioned the adequacy of the factor of
.67 and suggested using a factor of 3.78 which is a composite product of a thrust coefficient of 1.26, a gap rebound factor of 1.5 and a dynanic load factor of 2.0.
(3) Response to Staff Question 3.6.7 (October 4, 1974)
indicated to use a DAF = 1.67 with a gap of 2.5-inch DAF = 1.83 with a gap of 5.0-inch Thrust Coefficient = 1.2 Rebound Factor = 1.0 (bast on rupture force equal to or greater than pipe resistance)
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Example: most critical condition 26" 0.D.
- Main Steam line F = 1.2 x 1.2 x 1.68 x P x A
= 2.4 PA Thrust Coefficient = 1.2 Rebound Factor = 1.2 DAF = 1.67 Operating Pressure = P Pipe Flow Area = A (4) B-GFD " Pipe Restraint Criteria for Containtment" dated June 17, 1971, checked on October 2, 1976, stated F = 1.5 PA including the 26" O.D. Main Steam line.
(5) B-GPD " Davis-Besse Design Criteria Manual," dated December, 1970, Section 2.?.?.c.4, states use a dynamic load factor = 1.5.
(6) Combined factors used in actual pipe whip restraint calcu-lations for the cold and hot leg varied. Factors noted that were actually used were 1.5, 1.22, and 1.56.
b.
Inconsistant Design Allowables The inspector's review of pipe whip restraint calculations, identified the use of allowable stresses that were incon-sistant. The values used were:
S = 1.5 (0.45) Sy at 200*F for hot leg pipe whip restraint
= 0.68 Sy structure.
S = 0.5 Sy at 200*F for hot leg pipe whip elbow strap connecting pins.
S = 1.5 Sm at 650*F for cold leg pipe whip restraint structure.
The design allowable shown in the response to FSAR Staff Question 3.6.7 (October 4, 1974) stated:
Design allowable: Stress = 1.2 Fy Apparently the licensee committed to the design of inelastic structures in the FSAR but calculated the pipe whip restraints within elastic limits. This means a gap rebound factor of 1.5 as suggested by the NRC Staff should be used in the analysis instead of the value of 1.0 or 1.2 specified in the licensee response.
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c.
Cable Type Pipe Whip Rescraints
The inspector reviewed some of the calculations for the hot leg pipe whip cable type restraints and considered them to be questionable for the following reasons:
D was considered, (1) AlthoughtheloadreductionfactorofNressesdueto the local and system elongations and s dynamic impact of the pipe moving a gap of more than 3-inches were not analyzed or tested.
(2) The cable manufacturer's design data was not applicable to the design of pipe whip restraints.
(3) The design spring rate used in the calculations is for a 1 1/4" rope supplied by Bethlehem Steel Corporation (6 x 41 Type M, Purple Plus rope). The design drawings called for the use of 2 1/8", and 3" cables of 6 x 37 class or equal.
d.
Design Criteria, Design Change Control and Design Verification As stated in Paragraph 5.a and 5.b the design criteria, i.e.
design forces and acceptance was not in accordance with FSAR commitments. During his review of the hot leg pipe whip cal-culations, the inspector observed independent checks had actually altered the original design and became the actual installation without additional independent review. Furthermore, there appeared to be no established and approved instructions or procedures to control the quality of calculations including design basis, acceptance criteria, change control, and veri-fication. Simple mathamatical errors were found in the calcu-lations reviewed.
e.
Pipe Whip Restraint Gap Design and Verification As stated in Paragraph 5.a.(3) the DAF of 1.67 used was based on a restraint gap dimension of 2.5-inen.
In fact, the insulation itself is 5" thick and adding a protector and small shimming gap, the total gap could become 3.25-inch and require a DAF =
1.72 (straight line ratio between DAF = 1.67 at 2.5" gap and DAF = 1.83 at 5.0" gap). Relative to the gap dimensions, there appeared to be no operational requirement to inspect after periods of plant service, to verify the actual gap dimensions after pipe system configuration adjustment and material reiaxation.
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During the plant inspection on June 20-22, 1979, non-uniform tensioning and sagging of the cable restraints on the primary coolant pumps was observed by the inspector. This was pointed out to the accompanying licensee site representative for followup.
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6.
Discussions with the NRC Staff A meeting was held on September 7, 1979, to discuss the RIII a.
findings with the licensee and his representatives.
In response to these findings the licensee made the following commitments:
(1) Perform a pipe whip restraint analysis based on B-GPD Topical 2, " Design for Pipe Break Effects". This will be a time-history analysis and will be performed on one complete reactor coolant hot and cold leg piping system.
(2) The modeling of the pipe system will be based on the actual piping configuration and include the ring type and cable type restraint physical properties and actual locations.
(3) If actual restraint gaps are not measured at the site, sensitivity studies will be performed to establish the most severe conditions.
(4) Submit a report of the re-analysis to the NRC (IE RIII)
by November 9, 1979.
b.
Subsequent to the meeting a telephone discussion was held with the licensee where additional clarification was obtained concerning the previous commitments. Areas clarified included:
(1)
If the loads that result from the new analysis exceed the original design loads, the existing structures (walls and steel embedments) will be modified or justification provided to assure their adequacy for safe operation.
(2) The analysis will be performed in accordance with the applicable present day QA manual requirements.
Exit Interview The inspector met with the licensee representatives at the conclusion of each inspection. The inspector summarized the scope of the inspection in this report.
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