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Addendum 1, Lab Collapse Tests, Revision 0,to Steam Generator Evaluation,Ginna Steam Tube Failure Incident, 820125,RE Ginna Nuclear Power Plant
	ML17256A977
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Issue date:	05/18/1982
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Steam 'Generator Evaluation Ginna Steam Generator Tube Failure Incident January.

25.,

1982 R; E. Ginna Nuclear Power Plant Docket No. 50-244 Addendum 1

Laborator Colla se Tests SRQ pecan ItEfllN.MPl)lKf8FlifM Revision 0

May 18, 1982

MODEL 44 STEAM GENERATOR TUBE-(7/8" O.D. x 0.050" WALL)

COLLAPSE TESTS UNDER COMBINED EFFECTS OF EXTERNAL PRESSURE AND LATERAL IMPACT LOADING MAY 1982 0198s:10

LABORATORY COLLAPSE TESTING PROGRAM INTRODUCTION The purpose of this testing program was to experimentally verify that repeated lateral load impacts on a 0.875 inch outside diameter (0.050 inch nominal wall) steam gener ator tube subjected to an external pres-sure could ultimately result in tube collapse.

The postulated collapse mechanism begins with initial plastic deformation of a tube under the combined influence of external pressure and lateral impact loads.

The tube continues to deform progressively with subsequent lateral impacts and eventually the deformed tube section reaches a limiting ovality at which time the section collapses under the influence of the secondary side (external) pressure.

Two types of tests were performed:

a lateral load bench test and a

dynamic collapse test.

The lateral load bench testing was performed to determine a meaningful lateral load magnitude to initiate plastic defor-mation in the test specimens.

The test set-up was designed to simulate the shell mode deformation of tubing when impacted by an object such as the edge of a plate.

In the dynamic collapse tests, tube specimens were mounted inside a

larger diameter tube to permit application of an external pressure and lateral loads were applied by an impact rod driven by a hydraulic cylinder.

The impact rod head was in the form of a chisel to simulate the edge of a plate impacting the tube surface.

This report describes the specimens, equipment and procedures used to perform the tests and summarizes the results of the tests performed.

Additional details of the test program will be included in a

Westinghouse Research and Development Report.*

'WR D Report (82-7P6-EVMTL-RZ) entitled "Dynamic Collapse of Steam Generator Tubes", in the process of being released.

0198s:10'

I ~

~Sec i mens The specimens were Inconel 600 steam generator tubes with 0.875 inch 0.D. and 0.050 inch nominal wall.

The bench test tube lengths were 6

inches.

The test lengths for the dynamic collapse tests were either 19.2 inches or 52.0 inches.

~Eui ment For the lateral load bench tests, two 2-inch long V-blocks were used to support a

6 inch tube specimen, which was held in place by means of plates over the V-blocks.

Force was applied to the tube by means of a Baldwin Tensile Machine with a chisel type device similar to that used in the dynamic collapse test attached to the crosshead.

For this test, the scale was set at 5000 lb. with a sensitivity of + 5 lb.

Micrometers were used to measure the outside diameters of the tube at the various loading points.

The test fixture schematic and photographs of the test setup for the dynamic collapse tests are. shown in Figures 1 through 3.

The photograph in Figure 3 shows the instrumentation details.

For the dynamic collapse tests, the tube specimen was mounted inside a

2.00-inch diameter tube with associated end caps,

tees, seals, etc.

A hydraulic cylinder applied the impact force through a rod and a

hydraulic controller and function generator controlled the servovalve which controlled the fluid supplied to the hydraulic cylinder.

The force, deflection, and acceleration were measured by a load cell, LVDT and accelerometer respectively.

The LVDT and accelerometer can be seen in Figure'.

The transducer signals were monitored and recorded on a Nicolet storage scope.

The cyclic frequency and deflection were set to give the specified test load.

At high frequencies, the hydraulic system could not react fast enough to provide a large load.

Therefore the frequency and/or deflection was adjusted appropriately.

0198s:10

0

Test Procedure The following procedure was followed to perform the bench tests:

1.

Mount the tube specimen in the V-blocks.

2.

Attach the chisel in the crosshead of the Baldwin Tensile Machine.

3.

Measure initial O.D. and I.D. of tube, using the micrometers.

4.

Initialize crosshead deflection.

5.

Load to 50 lb. and measure crosshead deflection.

6.

Release load (to zero).

7.

Measure O.D. under load (major) and O.D. perpendicular to load (minor).

8.

Repeat Steps 5 through 7 for higher loads.

The final load will be reached when the minor O.D. is about 0.500 inch.

The following procedure was used to perform the dynamic collapse tests.

Prior to each test the specific test parameters were determined and were used where the test procedure calls for "as specified" test requirement.

1.

Cut tube to the "as specified" length.

2.

Measure and record I.D., O.D.,

and ovality of the tube in the test section.

Mark the end of the tube to indicate the smallest diameter if there is ovality.

3.

Install the tube in the test fixture ensuring the smallest diameter is in line with the impact rod.

4.

Adjust collars to reduce effective tube span and increase portion of impact load reacted by a shell mode rather than a bending mode.

0198s:10

5.

Install end cap seals and other test fixture hardware.

6.

Turn set screws to provide a hand tight contact with the tube.

7.

Align the impact rod to meet the test requirements.

8.

Apply water or gas (as specified) external pressure.

Check for leaks and eliminate if they exist.

9.

Apply axial load if specified.

10. Apply the lateral

load, as specified, at various locations on the tube surface over an area centered four inches from the simulated tube sheet

support, and approximately two or three inches long (as specified) in the axial direction and roughly forty degrees in the circumferential direction.

Lateral Load Bench Tests Two tests were conducted:

one to simulate an impact by a relatively sharp edge (0.030 inch wide sharp chisel) and the other to simulate an impact by a somewhat blunt edge (0.125 inch wide blunt chisel ).

Ovality changes were monitored by measuring the permanent deformation of tube diameters along (O.D'min) and normal (O'D max) to the line of the applied load.

Tabulated results of the two tests are given in Tables 1 and 2 and shown graphically in Figures 4 and 5.

The test loads at room temperature were compared with their equivalents in the steam generator at 550 F.

Because the test specimens were thicker and had a relatively high yield

strength, the test loads required to cause plastic deformation and ultimate failure were high.

The load correlation for the test is shown in Table 3.

From the table, the steam gener ator load equivalent to a test load of 525 lb. is only 308 lb. with the average tube properties and 226 lb. with the minimum tube properties.

0198s:10

0 namic Collapse Tests The loading sequence prescribed for the tests was a series of impact positions with 10 to 25 impacts per position.

A convenient impact line was selected and the impact positions were spaced 0.25 inch apart throughout along a prescribed length.

At the end of the prescribed length the impact position was offset 1/8 inch and the procedure was repeated whi le backtracking along the initial impact line.

When the original poi nt plus the offset was reached, the specimen was rotated 20 circumferentially and the process was repeated.

Upon completion of this cycle, the specimen was rotated 40 circumferentially in the other direction and the impacting cycle was repeated to completion.

The three impacting procedures are termed a "sequence".

It is to be noted that two collars were inserted to support the tube in such a manner as to shorten the effective span.

In this way, the beam mode of tube deflection was minimized.

The results of four tests are presented in Tables 4 to 7.

The first test was done with 1000 psig argon gas and 600 lb. lateral load on the "sharp" chisel (0.30 inch wide chisel) impactor.

After four loading sequences, the impactor was changed to a 1/4 inch square chisel and 1000 psig water was used.

In the last stage, the spacers were removed and the specimen impacted continually at one location in the center of the deformed zone.

After a total of, nearly 23,000 impacts with the square impactor, the specimen developed a crack and the test was stopped.

The final ovality was 23.5 percent.

The second test had 10 loading sequences:

4 with 1000 psig argon gas and 6 with 1000 psig water.

The impactor was an 1/8 x 1.0 inch rectangular faced "blunt" chisel and the applied load was 650 lb.

At the tenth sequence, the ovality reached a value of 74 percent without showing any sign of collapse.

The specimen was finally subjected to 5650 impacts in the center of the test section with the impactor parallel to the tube axis and the tube began to deform on the back side.

0198s:10

The third test had the same impactor rod as the second test.

The load was reduced to 600 lb.

However, the impact length was i ncreased to 3 inches and the pressure was also increased to 1500 psig.

After three sequences, the tube collapsed, as shown in Figures 8 and 9.

The fourth test was similar to the third test except that the load was decreased to 450 lb. during the first four sequences, followed by an increase to 500 lb. for the next two sequences and 525 lb. in the last three sequences.

The tube collapsed during the ninth sequence.

The changing load was dictated by the magnitude of the change of the I.D.

after each sequence.

When the impacting process began to show a

diminishing effect, the load was increased.

Conclusions The tests show that plugged tubes in a steam generator environment can collapse due to a series of impacts applied over an area about 40 circumferentially by 2 to 3 inches axially.

The impact loading deforms the tube wall to such a degree that with the resulting ovality, the tube will collapse under the influence of the external pressure.

It is sig-nificant to note that the actual lateral force can be significantly lower than that used in the test, depending on other factors such as the area of impact, the total number of impacts and the initial ovality of the tube.

The number of impacts and sequences, in addition to the area of impact, appear important in reaching the deformation state of the tube surface just prior to collapse.

When the impacting surface is small, there is a possibility of local cold working and potential cracking which can hasten fatigue failure.

Three events are postulated from these findings:

1) the tube could fully collapse,

2) the tube would not collapse but could crack and eventually fail in fatigue, and 3) the tube would deform badly without collapsing and could also fail in fatigue eventually.

0198s:10

TABLE 1 LATERAL LOAD BENCH TEST SHARP CHISEL IMPACTOR Loads

~lb.

50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 O.D.

1

~in. )

.8720

.8715

.8710

.8700

.8695

.8690

.8682

.8652

.8630

.8620

.8585

.8550

.8535 O.D.

2

~in.

.8720

.8725

.8735

.8735 Percent Ovality Remarks Initial I.D..7659 inch; Mall =.053 inch

.06

.22

.28

.34

.43

.78 1.09 1.21 1.73 2.14 2.31 800

.8480

.8740 3.01 850 900 950 1000

.8432

.8385

.8271

.8262

.8768

.8752

.8762

.8774 3.90 4.28 5.76 6.01 0198s:10

TABLE 2 LATERAL LOAD BENCH TEST BLUNT CHISEL IMPACTOR Loads

~lb.

50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 O.D.

1

~in. )

.8719

.8715

.8709

.9702

.8700

.8690

.8678

.8665

.8632

.8612

.8578

.8538

'8488

.8442 O.D.

2

~(in.

.8719

.8720

.8732

.8735

.8740

.8742

.8746

.8759 Percent

~oval it

.06

.12

.20

.22

.34

.62

.80 1.18 1.47 1.87 2.36 2.99 3.68 Remarks Initial I.D..7658 inch; Mall =.053 inch 0198s:10

TABLE 3 CORRELATION OF TEST LOADS WITH THE EQUIVALENT LOADS IN THE STEAM GENERATOR AT 550 F

Test Loads Equivalent SG Load at Temp (550 F)

Average Pressure*

Minimum Pressure**

Lateral Loads 650 600 525 450 Pressure 1000 1500 381 352 308 264 622 933 280 258 226 194 507 760 a (ksi) 59.0

- t (mi ls) 53 38.9 50 35;2 45 0198s:10

11

TABLE 4 DYNAMIC COLLAPSE TUBE TEST Specimen:

2609-1-B1 Impact Rod:

Chisel with.030 radius tip Load:

Pressure:

Sequence:

600 lb.

1000 psig, argon gas 0, 20

ccw, 20 cw x 2.0 in. length, 0.25 in. increments with 0.125 inch offset coming back.

10-25 impacts at each location.

~Se uence O.D.

~in. )

.884/.861

.750

.734

.711

.689 Percent

~Oval it Remarks 2.6 Preset ovality

.9165/.781

.668 16.0 Tube removed for inspection After completion of above test, the following dynamic tests were run with a 600 lb. load, 1000 psig water Impactor 1/2 x 1 1/4 x 1/4 1/4 x 1/4 1/4 x 1/4

~lm acts 750 700 9,000 12,645 I.D.

.642

.633

.632 Remarks Tube removed to change impactors Mithout spacers-speciment developed crack.

Test stopped.

Final O.D. =.9278/.7328 Ovality = 23.4 percent 0198s:10

TABLE 5 DYNAMIC COLLAPSE TUBE TEST Specimen:

2609-1-B-2 Impact Rod:

Rectangular face:

1/8" x 1.0" Load:

~

Pressure:

Sequence 650 lb.

1000 psig, argon gas (Seq. 1-4); deionized water (Seq.

5-10) 0, 20

ccw, 20 cw x 2.0 in. length, 0.25 in. increments with 0.125 inch offset coming back.

10-25 impacts at each location.

0.D.

~Se uence

~in.

0

.873/.873

.766

.7341

.6953

.6643 Percent

~Ovalit Remarks 0

Wall =.053 inch 4

.923/.766

.6467 18.5 Tube removed for inspection Tube rei nstalled:

10-25 axial impacts added at end of each sequence

.6093

.5872

.5561 8

.9812/.6721

.5463 37.3 Tube reinstalled:

Sequence same as 5-8

.5201 10 1.0587/.4851

.3952 Tube removed for inspection.

Tube removed for inspection.

Final test:

5650 axial impacts in center of test section.

Comments:

Tube began to deform on back side during sequences 9 and 10.

0198s:10

TABLE 6 DYNAMIC COLLAPSE TUBE TEST Specimen:

2609-1-C Impact Rod:

1/8 x 1 inch chisel Load:.

Pressure:

Sequence:

600 lb.

1500 psig, deionized water 0

20

ccw, 20 cw x 3.0 in. length, 0.25 in. increments with 0.125 inch offset coming back.

10-25 impacts at each location.

O.D.

~Se uence

~in. )

I.D.

~in. )

Percent

~Oval it Remarks

1. 1925/. 3694

.6914

.5331 0

.878/.8605

.756 Initial:

0.0.

=.871 inch; I.D. =.765 inch; Wall =.053 inch; Ovality = 0 inch Tube collapsed.

0198s:10

TABLE 7 DYNAMIC COLLAPSE TUBE TEST Specimen:

2609-1-C-2 Impact Rod:

1/8 x 1.0 inch chisel point Pressure:

Sequence:

1500 psig, deionized water 0,

20

ccw, 20 cw x 2.0 in. length, 0.25 in. increments with 0.125 inch offset coming back.

10-25 impacts at each location and in center after completion of sequence..

.8705

.7652 0

.881/.859

.7531 2.52

0. D.

I.D.

Percent

~Se uence Load

~in.

~in..

Ovality Remarks Initial diameter Initial ovality 450 450 450 450 500 500 525 525 525

.7161

.6995

.6851

.6771

.6584

.6378

.5882

.5067 1.1597/.492

.3723 80.8 Start using 1/2 in.

increments.

Increased load.

Tube collapsed.

Removed for inspection.

0198s:10

DECL. SQOICQ2 AIR EhLRRD hue (TYP. SDT~ aeOS)

EVD CAP SPECIMEN CAP SCRl,W II LD OIA.Turd

~I SW~E<m Q,.O DIA.TEE "D" RING%a

~r. e,o~ a~)

IDDDPel wATER O'R GA%

DYI4AiAIC IMPACT ROD STANDOFF 6 LOAD CELL NYDRAUIIC CYLINDER HYDRAULICCVI INDE MDUNTIHQs F I)CTURE.

Test Fixture for Collapse Of,Steam..Generator Tubes.

FIGURE 2:

PHOTOGRAPH SHOWING THE TEST SET-UP FOR TUBE COLLAPSE TEST

~

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CL ED

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,+~pig%l\\

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UJ CXlI-LLII-ED U

C/l I-LJJ C5 5l-N I

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,.- n'.s

'i i lE I

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~ o LLI OC C9

IMPACT ROD-TIP 0.030" x 1.00",90'APER CLAMP CLAMP 2400 2200 BLOCK 0

II IIgll

'LOCK 2000 1800 1600 O.D.MIN.

0.D.MAX.

TUBE, O.D.

=.872" I.D.

=.766" OVALITY

= "0" I 1400

~ 1200

)

Gi c> 1000 800 600 400 200

.872"

.400

.500

.600

.700

.800

.900 1.00 1.10 1.20 DIAMETER, IN.

FIGURE 4:

RESULTS OF LATERAL LOAD BENCH TEST WITH SHARP CHISEL IMPACTOR

IMPACT ROD - TIP.125 x 1.00, 90 TAPER Clamp 7/8 x 6.0 TUBE Clamp TUBE, O.D.~.872" I.D.=.766 "

iiVii B3ock 2.0 llvll Block OVALITY= "0"i 2400 2200 2000 1800 O.D. MIN.

O.D.

MAX.

1600 1400

~-

1200 1000 800 600 400 200

.872

.400

.500

.600

.700

.800

.900 1.00 1.10 1.20 DIAMETER, IN.

FIGURE 4.7.1-5 RESULTS OF LATERAL LOAD BENCH TEST WITH BLUNT CHISEL IMPACTOR

t

FIGURE 6:

'RONT VIEW OF THE COLLAPSE SPECIMEN IN TEST 3

FIGURE

-7 PROFILE VIEW OF THE COLLAPSED SPECIMEN TEST 3, SHOWS THE DEFORMED TUBE WALL OF THE FRONT AND AT THE BACK

l l

I'

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