ML20125E432
| ML20125E432 | |
| Person / Time | |
|---|---|
| Site: | 07105364 |
| Issue date: | 04/08/1985 |
| From: | Schwoerer F NEUTRON PRODUCTS, INC. |
| To: | Macdonald C NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| 25082, NUDOCS 8506130113 | |
| Download: ML20125E432 (3) | |
Text
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NEUTRON PRODUCTS inc a
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22301 Mt. Ephraim Road, P.O. Box 68
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!y April 8,1%5 Mr. Charles E. Mcdonald 77)
Chief, Transportation and Certification Branch O.S. Nuclear Regulatory Commission 3ECEl'C d
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Subject:
Certificate of Compliance No. 5364
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Dear Mr.:
Mcdonald:
Duringad'IscussionofseveralmattersatNRCTransportatio'nb[
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.we described a failure of the drain / vent line in Section 8 of the Model %.
NPI-67-0442 cask system and dispussed our plans for effecting its repai d NRC representatives recomended that we treat the matter as reportable under 10 CFR 71.95. This letter is in response to that recommendation.
It also addresses related experiences of drain line failures in Section C of the cask system.
Although we are willing to file such reports, we have not considered drain line
-failures to be reportable under 10 CFR 71.95, because actions and precautions taken by Neutron Products have precluded significant reduction in the safety and effectiveness of the packaging.
We have occasionally experienced failures of drain / vent lines resulting-in
- comunication between the internal cavity (source chamber) and the internal volume containing. lead shleiding, in no case has the integrity of the boundary between the interior of the cask and the environment been affected. -The-consequences of internal leakage are radioactive contamination of the shielding cavity and, in a hypothetical accident condition, possible loss of some lead shleiding by migration of lead into the shipping chamber. The potential loss of lead shielding is limited by our practice of filling the unused volume of the shipping chamber with stainless steel rods and/or brass disks.
Section C is the bottom section of cask Modes II and IV, as described in the Certificate of Compliance. On several occasions the drain / vent lines have failed where they are welded to the stainless steel lining of the source chamber. The problem was first identified in.1974 and the weld was repaired.
The problem _ recurred and repairs were made in.1980, 1983, 1984, and 1985. The cause of the failures is thought to be differential thermal expansion between
-the lead shleIding and the stainless steel lining and possibly also differential movement when the cask is set down, which events impose stresses on the drain line.where it is welded to the lining of the source chamber.
In the latest repair, recently completed, the old drain / vent tubes have been removed and replaced with heavier wall tubing.
In addition, shims have been
' installed in the expansion void at the bottom of Section C to restrain movement of the lead.
In our judgement, this repair is in accordance with the Certificate of Compilance and the basic design of the shipping container.
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r Mr. Charles E. Mcdonald April 8, 1985 Page No. 2 Section B is the bottom section of cask Modes I and III, as described in the Certificate of Compliance.
In 1980 Neutron Products identified an Internal leak in e drain / vent line in a location not accessible for repair. An internal review of the safety significance was performed at that time and it was determined that the only potential concern was loss of some lead shielding, by migration into the source. chamber, in a hypothetical accident condition. This possibility is mitigated by filling the unused volume o/ the source chamber as described above. Section B was removed from service in 1984 for the purpose of effecting repairs. The planned repair involves installing a stainless steel sleeve in the 4-1/2 inch diameter central hole and sealing the holes in the upper tube sheet, thereby isolating the source chamber from the cavity containing lead shielding, and providing for drainage through the top.
Although we do not believe a structural review is required, our approach involves a change in the method of cask drainage and, prior to initiating these repairs, we will review with you the planned repairs and detailed drawings, with the hope that you will concur.
Very truly yours, NEUTRON PRODUCTS, INC.
Frank Schwoerer Vice President FS:mbn DOUTROD 3RODUCTS inc
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