ML20147B295
| ML20147B295 | |
| Person / Time | |
|---|---|
| Site: | 07109196, 07100192 |
| Issue date: | 01/24/1997 |
| From: | Franceschi V VECTRA TECHNOLOGIES, INC. |
| To: | Shankman S NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| VF-97-15, NUDOCS 9701300167 | |
| Download: ML20147B295 (4) | |
Text
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VECTRA l
January 24,1997 VF-97-15 Ms. Susan Shankman Chief, Transportation Safety and Inspection Branch U.S. Nuclear Regulatory Commission 1 White Flint North 11555 Rockville Pike Rockville, MD 20852
Subject:
VECTRA UX-30 Overpacks, Certificate of Compliance No. 9196, Evaluation of Potential Excess Grinding on Overpack Corners
Dear Ms. Shankman:
As requested by Mr. Paul Narbut at the recent UX-30 inspection exit meeting, VECTRA is submitting the enclosed evaluation of the potential excess grinding on UX-30 Overpacks.
If you have any additional questions on the enclosed evaluation, please do not hesitate to contact me.
Sincerely,
/
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Vincent Franceschi Vice President and General Manager VECTRA Fuel Services cc:
Paul Narbut - USNRC David Faulstich - VECTRA Dick Ayres - VECTRA 0%
d' Chuck Temus - VECTRA Usama Farradj - VECTRA Jack Rollins - VECTRA I
9701300167 970124 ?
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PDRj VECTRA Technologies, Inc.
6203 San Ignacio Ave., Suite 100 San Jose, CA 95119 Tel(408) 629 9800 Fax:(408) 2814186 / (408)281-6202
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l Evaluation of Potential Excess Grinding in the Corner Areas of UX-30 Overpacks During the audit of Schneider Simpson, one of two manufacturers of UX-30 Overpacks, inspection of UX-30's in production showed some grinding in the base metal in an area one to three inches oelow the outside corner of some upper o.-lower assemblies. This was observed on some but not all corners. This was caused by grinding of a weld build up and blending of that weld where three weld been co ae together. Extra we'd is put in this area due to a small notch in the outer end cover to accommodate the fit up of the pieces meeting in thejoint. This is where the z-section, the cylindrical shell, and end plate are connected (i.e., a lap joint on a curved seam).
The weld causes some distortion to the curved surfaces of the base metal as it comes together in the lap joint in this area and in some cases gives the appearance of potential thinning.
Consequently, this distortion and the geometry make it very difficult to determine the amount of any thinning due to the grinding.
After review of the areas affected, photographs of the test units used to initially qualify the package, photographs of additional test units, and a design evaluation, it is concluded that the production units are consistent with the test unit configuration which forms the basis for the licensed product and does not adversely affect the performance of the package.
The purpose of the package skin is to perform three functions:
- 1. Prevent separation of the two halves of the UX-30 during an accident scenario.
2 Hold the foam in place during impacts.
- 3. Contain and direct the pressure build up from the off gassing of the foam during a fire scenario.
The role of the skin and the subject joint is as follows:
1.
The load path involved in preventing the separation of the two halves is parallel to the thinned area and has a small effect on the overall strength of thejoint. Due to the corner configuration, even if the area in question was deeply ground the area affected by the thinning would be stronger than the adjoining areas in the load path. These other areas are adjacent to the 3/16 inch plate (through which the load bearing connecting pin is welded) and the shell to z-section weld. The metal adjacent to the 3/16 inch plate is loaded in shear and the weld is loaded in tension. Testing has shown that the base metal of the z-section failed prior to the welds or the outer skin. Hence, thinning or complete removal of the ground base metal in the adjacent area would not change the load path or the results.
These areas are 100% Penetrant Inspected including the adjacent parent metal.
The best example of this is Photograph I which show the corner configuration and demonstrates that failure occurs in the parent metal of the z-section rather than in the area 1
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of potential thinning. This photograph is from the test unit which was used during the Type B qualification tests (yet to be submitted for NRC approval).
2.
The small area has an insignificant effect on the ability of the skin to hold the foam in place. Multiple drops of the package showed some failure of the base metal and welds in this area with no detrimental affect on performance. In the actual tests, the tearing of the skin in the immediate area due to deformation was larger than the potentially thinned area.
The foam remained intact and performed its intended function during multiple drops.
3.
The potentially thinned areas on the test units had no detrimental effect during the fire. As demonstrated in the fire test, if an area in the skin is violated it produces another vent path for offgassing the foam / fire produced gases and reduces the potential for pressure in the foam cavity. The small localized area in question would not lead to a catastrophic failure of the skin. The pressure capability of the foam cavity is significantly above the blowout pressure of the built-in plastic plugs. Due to the nature of the foam, it as has been demonstrated both in the laboratory and by test (see section 3.6.1 of the SAR ) the integrity of the skin is not required for the foam to protect the 30B cylinder during the fire event.
In conclusion, the configuration of the corner and the weld distortion in the welded joint make it very difficult to determine the amount of thinning that has occurred. Similar distortion with grinding is evident on the test unit which successfully passed all required performance tests and were used in qualifying the licensed product. Evaluation of the functions the shell serves demonstrates any localized thinning in the area in question would have no significant effect on the performance of the UX-30 Overpack to meet its functional requirements.
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