ML20050B244

Forwards Final Response to NRC Questions on Fluid Dynamics Re Hydrodynamic LOCA Loads & Proprietary Grand Gulf Hydraulic Control Unit Floor Capability Proprietary Calculation. Proprietary Info Withheld (Ref 10CFR2.790)

ML20050B244
Person / Time
Site:	Grand Gulf
Issue date:	03/31/1982
From:	Trickovic R BECHTEL GROUP, INC.
To:	Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML19268D133	List: ML20050B244
References
VB-82-0075, VB-82-75, NUDOCS 8204050138
Download: ML20050B244 (8)

Text

3 Bechtel Power Corporation Engineers-Constructors 15740 Shady Grove Road Gaithersburg, Maryland 20760 301-258-3000 March 31, 1982 g United States Nuclear Regulatory Commission 1 Office of Nuclear Reactor Regulation m R CEIMEU Division of Licensing 2 T

gA,p g 0 5 1582 ;8 Washington, D.C. 20555 6 Attention

Mr. Harold R. Denton \

Director g

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Dear Mr. Denton:

Nuc] ear QA Is Applicable Middle South Energy Inc.

Grand Gulf Nuclear Station Bechtel Job No. 9645 File: 0266/0862/L-860.0 Transmittal of Final Response to NRC Questions on Fluid Dynamics - Hydro-dynamic LOCA Loads Docket Nos. 50-416, 50-417, Units 1 and 2 VB-82/0075 Portions of the enclosed final response to NRC requests for additional information regarding hydrodynamic LOCA loads (Enclosure 1 and Enclosure 2) are confidential and proprietary to Bechtel Power Corporation. Therefore, j fifteen (15) copies of Enclosure 1 and Enclosure 2 are being submitted to you l

directly by Bechtel Power Corporation as agent for Mississippi Power & Light Company. The enclosed final response contains information requested by members of the NRC's Structural Engineering Branch.

The enclosed Proprietary Information (Enclosure 2) consists of design calculations that support the conclusions contained in the enclosed nonproprietary final response (Enclosure 1).

l Under terms of our affidavit and cover letter, D. E. Huffman, Bechtel Power l Corporation, to Edward C. Shomaker, NRC, dated June 6, 1980, the attached

information contained in Enclosure 2 is of the type described in the affidavit l

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l 0204050138 820331 PDIJ ADOCK 05000416 99 /.hI W b l

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Bechtel Power Corpolation United States Nuclear Regulatory Commission March 31, 1982 Bechtel Job No. 9645 VB-82/0075 and cover letter and should be treated as confidential and proprietary for the same reasons as the previously submitted information.

Very truly yours,

1. .4 _

R. S. Trickovic Project Engineer RLB:n11

Enclosures:

1. Final Response - Hydrodynamic LOCA Loads

2. Calculation C-G755.0, Rev. 0 (Proprietary) cc: L. F. Dale, 2w/2

• T.11. Cloninger, w/l*

T. E. Reaves, w/l*

C. K. McCoy, w/l*

J. F. Pinto, w/l*

M. D. Archdeacon, w/l*

L. Ruhland, w/l*

J. P. McGaughy, w/l*

J. D. Richardson, w/l*

J. D. Ileaton, w/l*

E.11. Duda , 2w/l*

J. N. Ward, w/o C. D. Wood, w/o ,

D. E. Stewart', w/o R. J. Casamento, w/o A. Zaccaria, w/o

• Enclosure 1 only; Enclosure 2 is Proprietary with distribution to addressee only

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r Enclosure 1 to VB-82/0075 FINAL RESPONSE Grand Gulf Containment Building HCU Floor Capability j

Enclosure 1 to VB-82/0075 Grand Gulf Containment Building HCU Floor Capability Evaluation I. Background During the course of the generic review of Mark 111 containment LOCA loads specified by General Electric Company in GESSAR II, Appendix 3B, the NRC raised concerns regarding the methodology to be used for determining drag loads on grating type structures and concerns regarding the specified froth impact pressure derived from GE test data.

At a meeting in San Francisco, California, on September 24, 1981, between the NRC, Bechtel, MP&L and CE, the NRC CSB Staf f requested that MP&L address several NRC questions regarding pool swell f roth drag and f roth impact loads and how these . loads are applied to the Grand Gulf containment building HCU floor. This request was made in order to enable NRC to resolve this issue as cn open item identified in the Grand Gulf Safety Evaluation Report. MP&L provided the NRC with responses to all questions (AECM-81/401, dated October 9, 1981; VB-81/0577, dated November 10, 1981). Appropriate portions of these responses will be incorporated in the next available amendment to the Grand Gulf FSAR.

At a meeting between GE and the NRC held November 20, 1981, GE's presentation to the NRC provided further justification that the GESSAR 11 f roth impact specification was bourding and conservative.- The NRC indicated that GE's additional information still may prove to be insufficient and presented a "best estimate" alternate methodology for froth impact loads. This "best estimate" methodology correlates the f roth impact pressure with the height of the impacted structure above the maximum suppression pool surf ace. The NRC also presented a concern that a single impulse duration may not be conservative due to structure natural f requency variations as well as GE test data interpretation.

To further assist in the resolution of froth impact loads for Grand Gulf, the NRC requested that MP&L perform further HCU capability evaluations using the NRC's "best estimate" methodology for f roth impact loads considering variable froth impact pulse durations. At a meeting between the NRC, MP&L and Bechtel v. December 16, 1981, the NRC was given a status of the work completed as of that date. Based upon discussions at that meeting, the NRC further clarified the criteria to be used in

_ performing the HCU floor capability evaluativa. The criteria are as follows:

1. Due to the dynamic nature of the froth impact / froth drag load, the capability of the structure may be evaluated using Elasto-Plastic Methods.

2. Figure 1 shows the pressure time history of froth impact / froth drag loads. The froth impact pressure on structures will vary with distance from the suppression pool surface as defined by Figure 4 of NRC's (G. Maise) presentation of "Best Estimate Methodology for Froth Impact Loads." As requested by the NRC, these pressures will r be increased by 3 pai for further conservatism (Figure 2).

4 to VB-82/0075

3. Froth drag is considered to be a constant at 11 psi.

4. The dynamic nature of the load function (froth impact / froth drag) should be considered.

5. Permisrible ductility ratios should be consistent with those accepted by the NRC for other similar type loads, as defined by Regulatory Guide 1.142 (concrete) and SRP Section 3.5.3 (steel).

11. Method of Analysis The load function as described in Figure 1 is considered an impulsive load. Impulsive loads as defined in ACI 349-80 are time-dependent loads which are not associated with the collision of solid masses. Other loads classified as impulsive loads in the design of the Grand Gulf Nuclear Station are:

1. Jet impingement

2. Blast preFsure

3. Compartment pressurization

4. Pipe-whip restraint reactions.

When structural elements such as concrete and steel are subjected to these loads, the structural response is determined by one of the following methods:

1. For structural elements which respond elastically, the dynamic effects of the impulsive los4 are considered by calculating a dynamic load factor (DLF). The structural resistance available to carry the impulsive load must be at least equal to the peak of the impulsive load transient multiplied by the DLF.

2. For structural elements which respond inelastically, the dynamic effects of impulsive loads are considered by performing a time-history dynamic analysis. Mass and inertial properties are included, as well as the nonlinear stiffness of structural elements under consideration. The applicable permissible ductilities are as follows:

Concrete Slabs Flexure 0.05/e-e' 10 Shear 1.0 Dynamic Increase Factor 1.1 Steel Beams Flexure 10 Dynamic Increase Factor 1.1

I Enclosure 1 to MPB-82/0075 III. Summary of Results The following results summarize the Grand Gulf IICU floor capability:

1. Maximum Dynamic Load Factor (DLF)

A study has been performed to determine the maximum dynamic load

' factor to be expected from the froth impact / froth drag loading specification. Froth impact duration (t ) was varied in 40 d

millisecond increments from 0.020 seconds to 0.220 seconds to address the NRC concern regarding this parameter. Froth impact peak pressure was varied from 11 psi to 16 psi to address the application of the NRC's "best estimate" methodology for froth impact pressure relative to the distance of the impacted surface above the maximum suppression pool surface. Froth drag pressure was taken as 7.4 psi or 11 psi in combination with the aforementioned variables to-

= address the calculated Grand Gulf wetwell pressure and the GESSAR specified wetwell pressure following pool swell.' This study showed that the maximum dynamic load factor is insensitive to the relationship between the peak froth impact pressure and the peak froth drag pressure.

The maximum DLF is approximately equal to a constant (1.45) which occurs when the structural. period is equal to t

d. Since the structural periods in question are in the range of 0.020 to 0.220 seconds, the maximum transient pressure is multiplied by a DLF of 1.45 for elastic structural evaluations.

2. Concrete Slabs The critical portions of the concrete slabs are located at Azimuths 90' (south) and 270' (north) as shown in FSAR Figure 3.8-67. The maximum froth impact pressure applied at the bottom of the concrete slab is equal to 14.5 psi (11.5 + 3). Using a DLF of 1.45 and concrete cylinder break test results, the shear stresses are within

the code allowable as defined in Section 11.4 of AC1 318.71. The bending of the slab is not critical and the stresses in the reinforcing steel are well within the code allowable.

3. Steel Beams i The steel beams at the same location as the critical concrete slab j will be subjected to a froth impact pressure of 18.0 psi (15 + 3).

For steel beams in the grating areas, the critical beams are located at azimuths 40' (south-east) and 315' (north-east) . The froth impact pressures calculated for these beams vary from 14.5 (11.5 +

3) to 19.0 psi (16 +3). In all areas, the ductility ratios are well within the permissible ductility of 10. The highest ductility ratio calculated is less than 3.2; the majority of the ratios are less l than 2.0.

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