ML17059B242

Suppl 4 NMP-1 Shroud Repair Hardware Stress Analysis.

ML17059B242
Person / Time
Site:	Nine Mile Point
Issue date:	08/13/1996
From:	Dalcher A, Gleason T, Ranganath S GENERAL ELECTRIC CO.
To:
Shared Package
ML17059B240	List: ML17059B239 ML17059B241 ML17059B242 ML17059B243 ML17059B244 ML18040A180
References
GENE-B13-01739, GENE-B13-01739-04, GENE-B13-1739, GENE-B13-1739-4, NUDOCS 9608210137
Download: ML17059B242 (20)

Text

0 ATTACHMENT8.2

, 0 SUPPLEMENT 4 MILE POINT 1 SHROUD REPAIR HARDWARE STRESS ANALYSIS

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GE Nuclear Energy GENE B13-01739-04 Supplement 4 August 1998 Supplement 4 Nine Mile Point 1 Shroud Repair Hardware Stress Analysis Prepared for:

Niagara Mohawk Power Corporation Nine Mile Point Unit 1 Prepared by:

GE Nuclear Energy Reactor Modification Services 175 Curtner Avenue, N/C 571 San Jose, California 95125

GE Nuclear Energy GENE B13-01739-04 Supplement 4 August 1996 Supplement 4 Nine Mile Point 1 Shroud Repair Hardware Stress Analysis Prepared by:

T.'. Gleason, Principal Engineer Reactor Modification Services Reviewed by:

A, N Dalcher, Principal Engineer Reactor Modification Services Approved by:

S. Ranganath, Engineering Fellow GE Nuclear Engineering

GENE B13-01739-04 Supplement 4 August, 1998 REVISION STATUS SHEET Revision A roval Date Descri tion P. Walier Jan., 199o Shroud Repair Hardware Stress Analysis Suppl. 1 H. iVehta Feb., 1995 Crack separation evaluation with 360'hrough wall cracks at H2 and H3.

Suppl. 2 P. Walier April, Addresses the changes and deviations in the as-1995 built hardware.

Suppl. 3 S. Ranganath April, Evaluation of the 270'tabilizer assembly with the 1996 lower spring bearing on a nozzle blend radius.

(Not re uired iflower s rin is relocated.)

Suppl. 4 S. Ranganath August, Relocated Lower Spring and Lower Spring 1996 Spacer evaluation.

GENE B13-01739-04 Supplement 4 August, 1998 IMPORTANT NOTICE REGARDING CONTENTS OF THIS REPORT Please read carefully The only undertakings of the General Electric Company (GE) respecting information in this document are contained in the contract between Niagara Mohawk Power Corporation (NMPC) and GE, and nothing contained in this document shall be construed as changing the contract. The use of this information by anyone other than NMPC, or for any purpose other than that for which it is intended is not authorized; and with respect to any unauthorized use, GE makes no representation or warranty, express or implied, and assumes no liability as to the completeness, accuracy, or usefulness of the information contained in this document, or that its use may not infringe upon privately owned rights.

GENE B13-01739-04 Supplement 4 August, 1998 CONTENTS 1 .0 INTRODUCTIONeooeoeoo ~ eoe ~ oe ~ ~ oo ~ ooooooooooeo ~ ~ ~ ~ oo ~ oooo ~ ~ ~ ~ ~ ~ oo ~ ~ ~~~ ~ ~ ~ ooeoooeoooooo ~ oooooo ~~ 6 2.0

SUMMARY

AND CONCLUSIONS ................................."........................ 6 3 .0 EVALVATI0 N o~~~~~oo~~eo~~~~~~~~~oo ~~~~~~~~~~~~~~~~~~~eo~~ ~ ~ ~~ ~ ~ oee ~~~~ oe ~~~oooo~ ~ ~ ~~ee ~oe oe ~ooe ~oe oo~~~~~ 6 3.1 BOTTOM SPRING SPACER ......................................................................... 6 3o2 CORE PLATE DISPLACEMENTe ~~ o. ~ oo ~ ~ ~ ~ ~ eoooooo ~~~~~~ oo ~~~~~ .error ~ oe ~ eo ~ ~ ~ ~ ~ ~ ~ ooooooeooooooo ~e 8 3 3 HARDWARE STRESSES

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4.0 CORE SPRAY PIPING........................................... ~ e ~ ~ ~ ~ ~ ~ ~ ~ ~ e ~ ~ ~ e ~ ~ e ~ ~ ~ ~ ~ ~ ~ ee ~ ~ ~ 9 5..0 REFERENCES ee ~ ~ ~ ~ ~ ~ ~ oo ~ ~ ~ ~ ~ ~ oo ~ ~ ~ ~ ~ ~ ~~~~ oo ~ ~ ~ ~ eooo ~ oo ~ ~ ~ ~ ~ ooo oo ~ ~ ~ ~ ~ ~ oo ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ oooo ~ oooooo ~~~~ 9

GENE B13-01739-04 Supplement 4 August, 1996

1. INTRODUCTION The purpose of this stress report supplement is to address the addition of the Bottom Spring Spacer (148C6912) to the shroud repair hardware and to address the affects of relocating the 270'ottom spring to the opposite side of the tie rod. The addition of the Bottom Spring Spacer extends the lower spring contact b'eyond weld H6A and restores the function of the lower contact to its intended design condition. Relocating the lower spring changes the equivalent spring characteristics which affects the seismic response for several assumed shroud cracked conditions. Reference 5.1 addresses the loads and displacements for the revised configuration.

2.

SUMMARY

AND CONCLUSION Adding the Bottom Spring Spacer restores the lower spring to its intended design function. The Bottom Spring Spacer limits possible temporary and permanent shroud displacements at weld H6A to less than the allowable values. The added piece is captured in all directions and is held firmly in place by a spring loaded clamping force.

The stresses in the added part are well below the allowable values for all operating conditions and accident events.

Moving the lower spring on the 270'ie rod changes the lower spring loads and displacements for certain assumed shroud cracked conditions. The loads on the stabilizer hardware were calculated and found to remain less than the bounding loads used in the original stress analysis. The core plate displacement for certain accident conditions exceed those previously calculated, but remain well below the allowable values.

3. EVALUATION 3.1 Bottom Spring Spacer (148C6912)

The Bottom Spring Spacer rests on the existing lower contact and extends beyond the potential crack location at weld H6A. The 3 inch extension accounts for the weld height, the heat affected zone (HAZ) and the calculated vertical weld separation during a steam line LOCA. The extended length also accounts for the initial mismatch, bearing area and margin. The weld dimension and HAZ are based on the design drawings and the inspection videos of this area.

GENE B13-01739-04 Supplement 4 August, 1998 The Bottom Spring Spacer is attached to the existing lower contact and includes features which capture it in all directions. The steps at the end of each leg fit under the existing lower contact to prevent vertical movement. A tang at the back of the contact block fits in the gap between the lower contact and the lower spring to prevent horizontal movement. A positive spring loaded clamping force (40 to 50 pound) against the sides of the lower contact prevent vibrations or any free movements. The Bottom Spring Spacer is made of Inconel X-750.

When installed, the legs of the Bottom Spring Spacer are sprung up to 0.215 inches to provided the clamping load on the lower contact. The resulting bending stress:

Bending Stress = 3E5c/L' 42,500 lb/in.'

= modulus of elasticity = 28.85 x 10'si

=

5 deflection = 0.215 in.

. c = spring thickness/2 = 0.205/2 = 0.1025 in.

L = spring leg length = 6.7 in.

The allowable bending stress for normal conditions is 1.5 Sm or 71,250 lb/in'.

The installation tooling may temporarily hold the legs sprung out to a maximum of 0.405 inches. Accounting for the greater deflection and the elastic modulus at the installation temperature, the bending stress during installation is:

Installation Bending Stress =(0.405/0.215) x(31.00/28.85) x 42,500 = 86,024 lb/in'his remains well below the 120,000 lb/in'ield stress for this material. There will be no permanent set during installation.

In the event of separation at weld H6A, (only during a steam line LOCA) the Bottom Spring Spacer limits the possible shroud movement and, together with,the core plate spacers, provide a redundant load path for the horizontal seismic loads. (The core support structure is also held in position by the core support bolts and by the core support aligner pins.) Without taking credit for the core support bolts or aligner pins, the limiting load on the Bottom Spring Spacer is the entire 63,800 Ib maximum horizontal seismic load. The Bottom Spring Spacer bears against the 4 inch wide lower spring and carries the load over the portion extending beyond weld H6A. A 1.2 square inch load carrying area is a conservative value.

Bearing Stress = P/A = 63,800 lb/1.2 in' 53,170 lb/in'he allowable bearing stress during a faulted event is 3 Sy or 276,900 psi.

GENE B13-01739-04 Supplement 4 August, 1998 3.2 Core Support Displacement The lower stabilizer spring bears against the shroud at the core support ledge and on the H6B weld crown. The contact extends beyond the H6A weld, but there is up to a 0.28 inch spacing between the contact surface and shroud above weld H6A. The 0.28 inches includes an estimated 0.13 inch weld crown height. The spacing above weld H6A means the shroud can move 0.28 inch in the direction of the spring before contact is made Ifthe movement is in the direction midway between the contacts the shroud movement may be up to 0.48 inches [0.28/COS(108'/2) = 0.48]

108'part, before contact is made.

The maximum transient core plate displacement midway between the springs for Upset and Emergency events is 0.26 inches as reported in Reference 5.1. The allowable transient displacements for these events is 0.75 inches and 1.12 inches respectively. There is no permanent displacement for these events.

A Faulted event may include permanent displacement ifthere is separation at weld H6A and the shroud moves before contact is made with the spring. With separation at weld H6A the shroud cylinder bears against the spring and its affects are included in the net spring characteristics. For this case, the maximum spring compression increases to 0.37 inches as shown in Table 1 of Reference 5.1. Including the permanent displacement, the maximum transient displacement during the faulted event is 0.85 inches (0.48+ 0.37 = 0.85). The maximum permanent displacement is 0.48 inches. During a faulted event, the allowable transient displacement is 1.49 inches and the allowable permanent displacement is 0.66 inches. These core support displacements supercede the displacement values reported in Table 4.8 of the original stress report, GE-NE-B13-01739-04, Rev. 0.

3.3. Hardware Stresses Reference 5.1 calculates the spring loads and displacements assuming the bottom springs are located 108'part and again with the bottom springs spaced 76'part.

The equivalent spring constants are 2782 k/ft and 5,000 k/ft respectively. There is no change to the tie rod spacing or to the upper spring spacing. The loads calculated in Reference 5.1 are the resultant of the loads applied by the two adjacent springs. Since two springs are actually sharing the total load, the load on any one spring is less than the load calculated in Reference 1.

GENE B13-01739-04 Supplement 4 August, 1996 9.9.1 Lower Spring The highest equivalent load at the lower spring is 68.33k and occurs midway between the lower springs 76'part. The load on the two adjacent springs is:

P = 68.33k/2 COS (76'/2) = 43.36k The 63.8k load used in the previous analysis remains the bounding load condition.

The shroud contact on the replacement 270'ower spring is modified to extend beyond the H6A weld and remains 316 SST. The bearing area on this contact is greater than 2.5 square inches.

/

Bearing stress = 63,800 lb 2.5 in' 25,520 lb/in'he allowable bearing stress for a faulted event is 3 Sy or 46,350 psi.

3.3.2 Upper Spring The analysis in Reference 5.1 show there are no changes to the loads at the upper spring and there are no changes to the previous stress analysis.

9.9.3 Tie Rod Repositioning the lower spring has no eQ'ect on the maximum tie rod load. The maximum tie rod load is governed by the MSLB uplift and any change in spring coefficient has insignificant affect on the net load. The bounding 92k tie rod load used in the original analysis remains valid.

4. CORE SPRAY PIPING The analysis in Reference 5.1 show there is no changes in the horizontal displacements at the upper spring. There is no changes in the core spray piping loads as result of the lower spring relocation.

5. REFERENCES 5.1 Supplement 1, Nine Mile Point 1, Seismic Analysis, Core Shroud Repair Modification, GENE-B13-01739-03, Rev. 0 5.2 Nine Mile Point 1, Seismic Analysis, Core Shroud Repair Modification, GENE-B13-01739-03, Rev. 0