ML17227A435
| ML17227A435 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 05/28/1992 |
| From: | Vickery D TIOGA PIPE SUPPLY CO., INC. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| REF-PT21-92 NUDOCS 9206020142 | |
| Download: ML17227A435 (21) | |
Text
ACCELERATED DISTRIBUTION DEMONSTRATION SYSTEM REGULATORY INFORMATION DISTRIBUTXON SYSTEM (RIDS)
ACCESSION NBR:9206020142 DOC.DATE: 92/05/28 NOTARIZED:
NO FACIL:50-335 St. Lucie Plant, Unit 1, Florida Power
& Light Co.
50-389 St. Lucie Plant, Unit 2, Florida Power
& Light Co.
AUTH.NAME AUTHOR AFFILIATXON VICKERY,D.M.
Tioga Pipe Supply Co., Inc.
RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)
SUBZECT: Part 21 rept re util Units 1
& 2
& root cause investigation by Tioga Pape Supply.
DISTRIBUTION CODE:
IE19D COPIES RECEIVED:LTR ENCL.
'IZE:
TITLE: Part 21 Rept (50 DKT)
NOTES:
DOCKET 05000335 05000389 RECIPIENT XD CODE/NAME PD2-2 LA NORRIS,Z INTERNAL: AEOD/DSP/ROAB NRR/DRIS/RVXB9 D RES/DSIR/EIB RGN2 RGN4 SECY VANDERMEL EXTERNAL: INPO RECORD CTR NSIC SILVERIE COPIES LTTR ENCL 1
0 1
1 1
1 1
1 1
1 1
1 1
1 1
1 1
1 1
1 RECIPIENT ID CODE/NAME PD2-2 PD NRR/J3OE5/OGCB11
.XG~~
0 1 GN1 RGN3 RGN5 NRC PDR COPIES LTTR ENCL 1
1 2
2 1
1 1
1 1
1 1
1 1
1 D
D R
D NOTE TO ALL"RIDS" RECIPIENTS:
D D
PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!
TOTAL NUMBER OF COPIES REQUIRED:
LTTR 18 ENCL 17
~,
1
T4OGA PIPE SUPPLY COMPANY INC. Q 2450 WHEATSHEAF LANE, ~$~~
PHILADELPHIA PA. 19137 CI 215 831 0700 May 28 1992 WATS NUMBER 800 523 3678 0 TELEX 834650 TWX II 7106701650 0 TELECOPIER 215-5331645 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Subject:
Root Cause Investigation by Tioga Pipe Supply
Reference:
Florida Power and Light St. Lucie Units 1 and 2
Docket Nos.
50-335 and 50-389 10CFR21 Tioga Pipe has concluded its investigation concerning the above referenced'eports.
This investigation, as detailed
- herein, encompasses examinations of other material of the same
- alloy, further examination of the defective material, evaluation for Root
- Cause, and proposed Corrective Actions.
Initially, samples of a product meeting the alloy and heat treat cycle were tested in order to determine if other products of the same alloy which were heat treated at the same time were defective.
This testing was performed on three SB564 UNS N04400 ANSI B16.11 3" 90 Degree Elbows and one SB564 UNS N04400 3" 90 Degree Elbow solid forging.
All 90 Degree Elbows tested were Heat Code "KP".
Testing of the 90 Degree Elbows included Dye Penetrant, Tension
- Testing, ASTM E112 Grain Size Determination, and Microstructure Evaluation.
The results of the testing on the 90 degree elbows are listed below in Table g1.
TABLE g1 The material was 100% Liquid Penetrant inspected in accordance with L.T.I. Procedure LP-III-1, Rev.
4 dated 5/28/91 using the Visible Dye method and three pieces were found to be acceptable with no indications observed.
SERIAL NO.
TENSILE STRENGTH YIELD
~ 2+o STRENGTH ELONGATION
~IN 4D CMTR RESULTS REQUIRED 86,000 PSI 70,000 PSI 80,278 PSI 82,998 PSI 81,387 PSI 39,000 PSI 25,000 PSI 39,364 PSI 40,903 PSI 40,000 PSI 42<
- 35. 04 45.3%
46.44 42.54 NOTE:
.250" SUB-SIZE TENSILE SPECIMENS WERE USED FOR TESTING.
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TIOGA Page 2 of 11 TABLE g1 (continued)
A Grain Size Examination was performed on the submitted Test Specimens in accordance with ASTM E-112, Comparison Method with the following results SERIAL NO.
1 2
3 GRAIN SIZE INSIDE DIAMETER ASTM g2.5 ASTM g2.0 ASTM g2.0 GRAIN SIZE OUTSIDE DIAMETER ASTM g7.0 ASTM g5.0 ASTM g5.0 A Microstructure evaluation was performed with the following results SERIAL P1:
SERIAL g2:
SERIAL g3:
Insid'e
No grain boundary particles; twins Outside No grain boundary particles; twins Inside
No grain boundary particles; twins Outside No grain boundary particles; twins Inside
No grain boundary particles; twins Outside No grain boundary particles; twins FORGING HEAT CODE /
" TENSILE AREA ID STRENGTH YIELD (. 24)
STRENGTH ELONGATION (IN 4D)
KP-1 KP-2 NOTE:
- 45. 4%
.250" sub-size tensile specimens were used for testing per Customer's drawing.
A Grain Size examination was performed on the submitted Test Specimens in accordance with ASTM E-112, Comparison Method with the following results:
HEAT CODE /
AREA ID KP-1 (INSIDE)
KP-2 (OUTSIDE)
GRAIN SIZE ASTM g2 ASTM g2 ASME OSC467
'I ~
~
~
TIOGA Page 3 of ll TABLE g1 (continued)
A Microstructure evaluation was performed on the submitted Test Specimens with the following results:
HEAT CODE PKP-KP-1 (Inside)
No grain boundary particles;twins KP-2 (Outside)-
No grain boundary particles;twins Next, the seven 3" 30001 SB564 N04400 Tees of Heat Code "MA" were replaced by Tioga Pipe with seven tees of Heat Code "HW".
Heat Code "HW" was produced from billet material supplied by a different melter but was forged by the original forger within the same parameters as Heat Code "MA" except that the finished forging temperature was dropped from 2150 Degree F. to 2050 Degree F.
The temperature at which the 90 Degree Elbows Heat Code "KP" and the Tees Heat Code "MA" were forged was 2150 Degree F.
Independent testing of the representative 3" Tee forging (1 forging of the 8
manufactured) is reflected in the results found in Table g2.
HEAT CODE AREA ID TENSILE STRENGTH TABLE g2 YIELD
.24 STRENGTH ELONGATION IN 4D CMTR RESULTS 83,500 PSI REQUIRED 70,000 PSI 36,000 PSI 25,000 PSI 44.04 35.04 HW-3 HW-4 76,351 PSI 76,212 PSI 31, 164 PSI 31,864 PSI 44.04 43.
2%'OTE:
250" sub-size tensile specimens were used for testing per Customer's drawing.
CMTR results are from a forged test bar.
ASME asc~er
)I
TldGA page 4 of 11 TABLE 2 (continued)
Microstructure evaluation was performed on the submitted Test Specimens with the following results:
HEAT CODE gHW:HW-4 HW-3 (Inside)
No grain boundary particles; twins (Outside) No grain boundary particles; twins A Grain Size examination was performed on the submitted Test Specimens in accordance with ASTM E-112, comparison Method with the following results:
AREA ID GRAIN SIZE HW-4 (Inside)
HW-3 (Outside)
ASTM g2 ASTM g2 The forging manufacturer also tested a
section of the same representative forging with the following results; Tensile Strength 78,000
- PSI, Yield Strength (0.24) 33,000
- PSI, Elongation (4D) 41.0%,
Specimen Size
.252 round.
II
TIOGA Page 5 of 11 Shown in Table g3 are the results of comparison Tension Tests performed by the forging manufacturer on a representative forged test bar and a production forging of the same Heat Lot.
This testing was performed on SB564 NO4400 products of various sizes and configurations:
TABLE g3 HT CODE TENSILE(PSI)
YIELD(PSI)
ELONGATION FORGING TEST BAR 54 54 H1319 H1319 GT GT H1321 H1321 84,500 82,000 79,000 81,000 83,500 80,500 79,000 81,500 38,'000 34,000 30,000 36,000 35,200 34,800 30,600 40,600 47.0 43.0 47.0 42.0 43.0 42.0 47.0 44.0
(.255RD)X
(. 253RD) X
(. 255RD) X
(. 505RD) X
(.255RD)X
(.505RD)X The conclusions from the testing results contained in Tables 1, 2, and 3 are as follows:
A)
All material tested
- met, the material specification requirements.
B)
Subsequent testing of production forgings and forged test bar for comparison testing of products would be inconclusive without first determining the parameters for
-size, configuration, temperature, and time at temperature.
C)
Comparison results generally reflect that the supplied product is representative of the certifications.
The Yield Strengths and Elongation generally vary less than the Tensile results.
The variations in the Yield Strength may be attributed to working during machining of a test specimen.
The Tensile results vary the least in Table g3.
ASME OSC~er
~ s
~
~
I
'A
TIOGA Page 6 of 11 Evaluation of the subsequent test results did not reveal any evidence that products other than the 3" 3000g SB564 N04400 Tees with Heat Code "MA" were defective.
The forging manufacturer had reported that this had been the first time that fittings of alloy SB564 N04400 of this size, specification, and configuration had been manufactured by their company.
In light of the above, the Root Cause Investigation then focused on the starting material and forging practices associated with these tees.
Florida Power 6 Light had already performed tension tests on one of the tees.
The remaining six tees were returned by Florida Power 6 Light.
These six tees and a tee solid were subjected to Grain Size Examination and Microstructure Evaluation for Tioga Pipe.
The results of these tests are reported in Table g4.
Note: Serial g7 is the solid tee forging.
The serial numbers correspond to the serialized Tension Test Results in the Florida Power and Light Final Report.
TABLE 4
A Grain Size examination was performed on the submitted Test Specimens in accordance with ASTM E-112, Comparison Method with the following results:
- Adjacent areas not photographed, Grain size 2
to 3.
SERIAL NO.
GRAIN SIZE INSIDE DIAMETER GRAIN SIZE OUTSIDE DIAMETER 1
2 3
4 5
6 7
ASTM g0.5 ASTM gl.O ASTM g1.0 ASTM gO ASTM g0.5 ASTM g0.5 ASTM gl.0 ASTM ASTM ASTM ASTM ASTM ASTM ASTM kO-5 k3-0 g6.0*
81.0 g1.0 g0.5 gl. 0 A Microstructure Evaluation was performed on the submitted Test Specimens with the following results:
SERIAL gl g8 inclusive Inside Particles in boundaries; twins Outside Particles in boundaries:
1 h
A
<8 V
Page 7 of 11 Subse'quent testing of the solid Tee (Serial ¹7) with Heat Code "MA" was performed with variations on specimen location and orientation.
The results of this testing is shown in Table
¹5.
TABLE ¹5 HEAT CODE AREA ID TENSILE STRENGTH YIELD
.24 STRENGTH ELONGATION IN 4D REQUIRED 70,000 PSI 25,000 PSI 35.04 MA-1
- 67,143 PSI MA-1 (Retest)
- 22.04
- 20.24 39.04
- Under minimum specification requirements.
NOTE:.250" sub-size tensile specimens were used for testing A Grain Size examination was performed on the submitted Test Specimens in accordance with ASTM E-112, comparison Method with the following results:
HEAT CODE AREA ID GRAIN SIZE MA-3 (Inside)
MA-1 (Outside)
ASTM ¹1 ASTM ¹2 A Microstructure evaluation was performed on the submitted Test Specimens in accordance with Customer's instructions with the following results:
HEAT CODE ¹MA: MA-3 (Inside)
Grain boundary particles; twins MA-1 (Outside) - Grain boundary particles; twins ASME asc.ocr
I ~
rj 4
- ~
T)OGA Page 8 of 11 An initial SEM/EDS Examination was performed by Florida Power and Light as part of their Failure Analysis.
This Examination found a high sulphur content on the surface of the cracked area of the forged tee.
Quantitative chemical analysis were acceptable.
- Also, an initial SEM/EDS Examination was performed by an independent lab on behalf of the material melter on a portion of the forged tee identified as Serial Number 2.
This Serial Number was found, by the forging manufacturer, to exhibit a deep crack.
The examination found debris at the crack enriched with SN, C, 0, SX, and AL.
Only after a Visible Dye Penetrant Examination had been performed on Serial Number 5
was a significant indication found.
This indication was visually examined and determined to be a through the wall crack.
Subsequent SEM/EDS Examination was performed by the material melter's independent laboratory on a portion of this specimen.
- Also, this same laboratory evaluated the mounted specimens and the broken tension specimens previously identified as Serial Numbers 6 and 7 which were supplied by Tioga Pipe. Serial number 5 and 6 represented low tension results and Serial Number 7 represented acceptable tension results.
The written results of these examinations as summarized by the material melter are quoted, in part, herein:
"We examined fracture surfaces from forging g5 as well as tensile test fractions from forgings g5, g6, and g7.
We also examined micros obtained from forgings g6 and g7 from Tioga Pipe but the particles observed at grain boundaries turned out to be pits, apparently from etching, so no identification could be made.
The EDS evaluation of the fracture surface of forging g5 agrees with the Florida Power
& Light findings of sulfur.
The alloy's content of sulfur was very low and besides we are unaware of any tendency of sulfur to migrate to grain boundaries so it seems likely that this came from an outside source.
ASME OSC487
Y)OGA Page 9 of 11 The EDS of the tensile specimen fractures shows elevated aluminum and silicon which is puzzling since no significant aluminate or silicate inclusions have been seen in any of the microscopic specimens examined.
- Again, these are elements that are not expected to migrate to grain boundary. locations.
This alloy does contain significant aluminum and silicon levels.
The carbides found in the grain boundaries would be the result of the thermal history of the forging.
We do not believe that the presence of carbides at grain boundaries is significant to the problem.
...At this time we do not new light on the problem.
of tin in these
- samples, results may have been due feel that this testing has shed any Since we did not find any evidence it would appear that our original to contamination. "
In an excerpt from the material melter's independent laboratory, the following characterization of particles found are stated herein:
"The particles are of at least two types.
The larger particles (which were seen on all of the fracture surfaces examined) are on the order of 2-4g in diameter and are thought to be carbides.
This spectrum indicates elevated levels of carbon, and perhaps, Fe, when compared with a spectrum of the metallic matrix.
The second type of particle, which was encountered on the fracture surface of the low ductility tension specimen, contains elevated levels of Si and Al.
These particles are usually smaller than the carbon-rich particles, on the order of 2q and less in diameter.
Also,....
a spectrum was taken of a large area of the low ductility tensile fracture surface.
This spectrum indicates elevated levels of Sl and Al on this surface.
The microstructure of this fracture surface exhibits many small fracture nucleation 'sites which presumably contain particles.
These particles are very small and were not able" to be probed to obtain meaningful EDS data.
These data suggest to me that there may exist a grain boundary film that is causing reduced ductility in this material.
I am unable to characterize the suspected film beyond the suggestion that it may contain elevated Si and Al."
ASME OSmer
Page 10 of 11
- Since, in the Summer of
- 1991, the material melter decided for commercial reasons to no longer produce this alloy, no further Corrective Action by'he melter, if needed, can be taken at this time.
Based on the results of the examinations, Tioga Pipe cannot document that the Root Cause of the problem was due to raw material defects.
Therefore Tioga Pipe concurs with the Florida Power and Light conclusion that the forging process may have been conducted improperly.
The forging manufacturer contends that'aw material defects are the Probable Cause and believes this contention can be supported by their interpretation of the objective evidence.
Addressing Corrective Action to preclude reoccurrence, the forging manufacturer has committed to the following actions:
1)
"Forging temperatures for Monel 400 have been reduced to 2050 Degree F. max rather than 2150 Degree F. max.
This will reduce the grain size and preclude the possibility of localized overheating.
2)
To avoid the possibility of detrimental imperfections-for example those exceeding ASME SA182 Section 11 All Nuclear Monel 400 fittings will be liquid penetrant inspected according to Ideal procedures."
Tioga Pipe Supply considers these Corrective Actions as effective measures and believes such measures should help to preclude the reoccurrence of this type of defect.
Since there does not appear to be any direct correlation between (a) maximum grain size and product specification conformance or (b) tensile testing of a
forged test bar vs. tensile testing of a production forging and product specification conformance, the invocation of such additional requirements would not be effective as an overall solution for all sizes and configurations.
ASME asc d'or
P f
I I B
TIOGA
, Page 11 of 11 Although an absolute documented Root Cause may never be established to the satisfaction of all concerned, the actions taken to isolate this problem and preclude reoccurrence address and follow acceptable quality practices.
Unless additional concerns develop subsequent to this Report that may have an effect on these conclusions, Tioga Pipe considers this investigation closed, with no further action required other than verification of implementation of Corrective Action.
If there are any questions on this Report, please contact the undersigned.
Douglas M. Vick y
Quality Assurance Manager DMV:bd cc:
Florida Power and Light Jon Priolo Alloy Stainless Products Annemarie Appleton Ideal Forging Jim Oberholtzer Slater Steel Daniel Schram ASME OSC~er