TXX-2395, Deficiency Rept Re Polar Crane Support Brackets.Initially Reported 770506.Vendor Removed from Bidders List for Future Work Until QC Problems Fully Resolved

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Deficiency Rept Re Polar Crane Support Brackets.Initially Reported 770506.Vendor Removed from Bidders List for Future Work Until QC Problems Fully Resolved
ML20235B756
Person / Time
Site: Comanche Peak  Luminant icon.png
Issue date: 06/21/1977
From: Gary R
TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To: Seidle W
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML17198A319 List:
References
FOIA-87-508 TXX-2395, NUDOCS 8709240218
Download: ML20235B756 (8)
v • d • e


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4 TEXAS UTILITIES GENERATING COMPANY 2003 HRY AN TOWEH. D ALLAN TVN AM 7*m June 21, 1977

n. .r. G ARY TXX-2395
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Mr. W. C. Seidle, Chief Reactor Construction &

Engineering Support Branch U. S. Nuclear Regulatory Commission Office Of Inspection & Enforcement Docket Nos. 50-445 4 611 Ryan Dr., Suite 1000 50-446 .i Arlington, Texas 76102 COMANCHE PEAK STEAM: ELECTRIC STATION POLAR CRANE SUPPORT BRACKETS FILE No. 10110 ,

1

Dear Mr. Seidle:

In accordance with 10CFR50.55(e) we are submitting the attached l report of actions taken to correct deficiencies with the Polar Crane Support Brackets.

We previously made-a verbal report to Mr. R. C. Stewart by telephone on May 6,1977, that potentially reportable deficiencies existed in the Brackets.

If we can provide any additional information, please advise.

Very truly yours, e

R. e . Gary RJG:pgk Attachment cc: Director, Office of Inspection & Enforcement (15)-

Director, Office of Management Information & Program Control- (1)

U. S. Nuclear Regulatory Commission -

Washington, D. C. 20555-L /

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8709240218 870921? - ( l( . p PDR FOIA \

WILLIAMBB7-508 PDR:

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TXX-2395 Attachment June 17, 1977 Page 1 POLAR CRANE SUPPORT BRACKETS l

l During receiving inspection of 15 Polar Crane Support Brackets l supplied by Bostrom-Bergen Metal Products, the surface condition of some welds was found to be unacceptable. While cleaning up the Brackets, it was found that the surface defects on some Brackets led to sub-surface weld defects.

Description of Deficiencies

1. Listed below are typical sub-surface defects found on the Polar Crane Support Brackets (Figure 1 provides piece number locations)
a. Heavy slag entrapment and incomplete welds were found in the full penetration weld between pieces pa and pab at the intersection with stiffener plates, pav, pas, and pan. There are six such stiffener plates on each Bracket and this weld problem at the stiffener was found on nearly all of the Support Brackets.
b. On two assemblies, A2-7 and A2-10, a corner area on the full penetration welds between the head assembly, pieces pw and ps, and the thickened liner plate, piece pa, had surf ace indications. These indications opened up into interconnected sub-surface slag pockets.
2. Additionally, support bracket A2-14 exhibited a slag line in the full penetration weld between pieces pa and pab which started at a stif fener and ran one-half inch under the surface of the weld for approximately two inches. This opened up into a series of slag deposits connected by cracks.
3. Bostrom-Bergen Metal Products reported that on the 13 assemblies still in their shop, they also had found the heavy slag entrapment and inccmplete welds in the full penetration weld between pieces pa and pab at the stif fener plates.
4. Based on the deficiencies encountered, TUCCO and TUSI initiated an Ultrasonic Testing (UT) Program to verify the soundness and quality of the welding performed by Bostrom-Bergen Metal Products. Southwest Research Institute (SwRI) was requested to supply a team of Ultrasonic Testing (UT) personnel headed by a Level III UT engineer who would examine the Polar Crane Support Bracket velds for additional sub-surf ace defects.

A procedure for conducting this examination was approved and appropriate calibration blocks were f abricated. Then a longitudinal examination and a. 450 and 600 shear wave examination was made of the entire length of the full

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TKX-2395 Attachment June 17, 1977 )

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penetration . welds between pieces pa and pab on the eight l Brackets listed in table 1. In addition the same UT j examinations were performed on the full penetration welds between pieces ps to pa, pw to pa, pv to pa, and ps to pt on ,

Brackets A2-3, A2-7,fA2-19, and A2-24, and between pieces '

pab to paa and pieces pad and paa on Bracket A2-7.

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These eight brackets were chosen as a random sample of the 15 Brackets on site. at that time. The pa to pab welds were selected because'they are the main load bearing welds between the shell and Bracket and because weld defects were ,

found in. these welds at the junction with the stif fener I plates. The UT evaluation of the other weld ~ junctions I listed'above was made to assure'that the weld defects found )

in these junctions'were of an isolated nature and to assure the overall quality of these full penetration welds was also acceptable.- 1 I

SwRI's UT examination and evaluation found small indications  !

in the 8 Brackets examined. See table 1 for summary of UT results. The number and size of the indications listed in table 1 was judged to be acceptable by Gibbs and Hill and l TUSI engineers for welds such as these which require visual '

and magnetic testing examinations but do not require a UT examination. However, to verify the accuracy of the UT results, exploratory grinding was.done on an area of Bracket A2-7 which had small UT indications. The grinding located the defects and verified that they were in fact small and acceptable.

5. The Polar Crane Support Bracket weld defects were caused by poor fabrication practices as follows:
a. The sequence of f abrication and welding of plate pa, pab, and the stiffeners was as follows: . (1) the f ull penetration weld was completed between pa and pab up to the last few layers; (2) at this time, the I stiffeners were added to compensate for potential plate deformation and a small snipe was cut in the stiffener to allow access to the full penetration weld under the stiffener; (3) the full penetration weld was then completed, but the small snipes prevented proper welding access to the area under the stiffener and resulted in slag deposits and lack of fusion;- (4) after completing the full penetration weld, the snipe area was filled in with weld metal to provide a finished weldment contour. This last step resulted in obscuring the incomplete fusion and slag entrapment that existed in the completed full penetration weld under the snipes except for a few surface pin holes.

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b. The deep full penetration welds and difficult access between plates pw, ps, pa and pt resulted in slag inclusions and inadequate weld fusion in the corners between these plates.

I Safety Implications The Polar Crane Support Brackets are welded to a thickened portion of the containment steel liner shell. These brackets are designed to resist maximum loading combination, including a Safe Shutdown Earthquake, without subsequent loss of the liner integrity due to excessive deformation from bracket load.

Had these support Brackets been installed without repair to the defective welds, it is conceivable that the defects could induce cracking of the welds under a maximum loading conditions, and possible failure of the support.

Corrective Actions When the magnitude of the problem was recognized by Brown & Root and by TUGC0 and TUSI representatives, Polar Crane Support Bracket installation was halted.

Disposition of Weld Defects

1. The defects noted in preceding paragraphs were cleaned up as follows:
a. The defects noted at the stiffeners were removed by cutting a rat hole in the corner of each stiffener to allow access to the full penetration weld. This was done at each stiffener on each of the 15 brackets--a total of 80 stiffeners. These areas were arc-gouged and ground to sound metal then magnetic particle inspected to ensure all defects had been removed.

Finally the areas were rewelded followed by final magnetic particle inspection. Excavation to a depth of about three-fourths of an inch was required to clean up the welds.

b. To remove the defects in assemblies A2-7 and A2-10, it was necessary to arc-gouge and grind almost all the way through the weldments, weld up the execvated area, back gouge and grind the back side of the newly deposited weld metal, and then reweld this back side to achieve the appropriate surface contours. Magnetic particle inspection was used throughout the repair process to ensure metal soundness.
c. The slag line in bracket A2-14, was removed by excavating approximately one and three-quarter inches deep to remove all slag and cracks in the weld. This area ' ens repaired as above by arc-gouging and grinding

TXX-2395 Attachment June 17, 1977 Page 4 to sound metal then magnetic particle inspected to ensure all defects had been removed. Finally the area was rewelded followed by final magnetic particle inspect ion.

In summary all velds behind the stiffeners and all observed weld surface defects were removed down to a point where magnetic particle testing revealed sound metal. Then, as required, the cavity was welded up to restore the original weldment contour.

2. Bostrom-Bergen Metal Products conducted a similar repair program for the full penetration weld behind the stiffeners on the 13 Polar Crane Support Brackets remaining at their plants. Further on-site inspection of the next two shipments of Brackets from this vendor revealed additional sub-surface defects that had not been previously identified.

For example, corners at the intersection of the side plate, pab, girder seat, paa, and thickened liner plate, pa, on assemblies A2-18, A2-26, and A2-28 showed visual surface indications such as cold laps and slag entrapment. These j areas were ground and in each case opened up into a slag  ;

entrapment area. l 1

J The defective welds were excavated at the CPSES site by 1 Brown & Root to completedly remove the defects. After I l verifying metal soundness by magnetic particle inspection, the excavation was rewelded followed by final magnetic particle inspection.

3. For Unit II Polar Crane Support Brackets, Bostrom-Bergen Metal Products have revised their fabrication and inspection activities as followes:
a. In the stiffener area, the snipe will be enlarged to approximately 1 1/2 x 2 inches to provide accessability for placing the weld and inspection.
b. All inspectors and the appropriate fabrication personnel have been made aware of the problems.
c. Unit 2 corner weld areas, areas corresponding to areas that were found to be defective on Unit 1 Supports, will be velded in such a sequence that " pin holes",

poor fusion and/or slag inclusions will be minimized.

Included in this welding sequence is an in-process inspection program.

4. Products being supplied by this supplier have been routinely inspected by B & R and TUCCO QA representatives at CPSES as part of corrective actions implemented to compensate for internal quality control weaknesses discovered at the suppliers facilities in the later part of 1976. This program has been effective in that the results of the site inspections led directly to identification of the previously documented weld defects.

4 m .s TXX-2395 Attachment June 17, 1977 Page-5' When the weld defects were noted, additional effort ~was made:

to prevent further rejectable Brackets from being shipped from the vendor's. plant. This' effort consiste' of Brown &-

Root sending one of their CPSES non-destructive examination inspectors in addition to a TUGC0 QA representative to the vendor's plant to inspect the Brackets prior to shipment.

Until all quality control problems with this supplier are satisfactorily resolved, the, augmented inspection established by TUGC0 and TUSI will continue to be carried out on products received from this vendor. In addition the vendor has been removed from the bidders list for future work until quality control problems _ are fully resolved.

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. TABLE 1 WELD DEFECTS NOTED DURING UT EXAMINATION 4

j OF ASSEMBLY MAXIMUM DAC NUMBER DEFECTS SIZE REMARKS NOTED nc es) {

skewed.45 looking up corner between A2-1 1 50 spot pab and pa and stiffener plate A2-2 none - - -

1 90 ~ 3/8 1 50 ~ 3/8 q A2-3 1 80 ~ 3/8 .I l

4 50 spots 'l 1 50 3/4 A2-7 80 intermittent excavated pw-pa j along pw-pa weld to locate j weld and this defect but pv-pa weld found only tiny I slag inclusions 1 25 spot A2-8 1 80 spot A2-14 1 110 ^ 1/2

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intermittent A2-19 "I "" ""-"" "Id 2 159 ~4-6 on ps-pa 2 50 spots intermittent on 20-125 na to na 6n lef6 Interaltt nt on 20-110 os to na En right f AS-M 1 200 ~1/2 1 159 ~7/8 2 50 spot ,

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