ML20127H146
| ML20127H146 | |
| Person / Time | |
|---|---|
| Site: | 07105364 |
| Issue date: | 06/14/1985 |
| From: | Macdonald C NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Schwoerer F NEUTRON PRODUCTS, INC. |
| References | |
| NUDOCS 8506260222 | |
| Download: ML20127H146 (3) | |
Text
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3%-SS FCTC: RHO JUN 141985 71-5364 Neutron Products, Inc.
ATTN: !!r. Frank Schwoerer P.O. Box 68 Dickerson,f1D 20842 Centlemen:
During a meeting on fiarch 29, 1985 Neutron Products, Inc. (IlPI) inforned the NRC staff that a cask designated as the !!odel No. NPI-67-0442 package (cask) has developed a leak into the shielding area between the inner and outer shells of Section B of the cask as a result of failure of the drain / vent line. By follow-up letter dated April 8,1985, NPI stated the problem was first identified in 1974 and the drain / vent line weld was repaired. The problem recurred and repairs were made in 1980, 1983, 1984, and 1985 in both Sections B and C of the cask. TIPI stated it thought the failure was due to differential themal expansion between the lead shielding and the inner and outer stainless steel shells and possibly movement when the cask is set down. The April 8 letter states in the latest repairs the old drain / vent lines have been replaced with heavier wall tubing. In addition, shins have been installed in the expansion void at the botton of Section C to restrain movement of the lead.
On April 16, 1985, fiPI (a flaryland Agreement State licensee) was infomed by the NRC staff that based on the information contained in their letter dated April 8,1985, that we do not believe the current package design, as modified, meets the requirements of Certificate of Compliance No. 5364.
We also stated we are concerned about the possibility of entrained water and radioactive naterial between the inner and outer shells of the package. The NRC staff further stated in their April 16 letter that "until effective repairs are made to the package, entrainment of water and radioactive naterial between the inner and outer shells is considered, and the package drawings are updated and referenced in the Certificate of Compliance, this package should not be used." By copies of the April 16 letter, both the Department of Transportation and liaryland State, Division of Padiation Control were notified of the NRC staff recommendation.
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a fleutron Products, Inc. By letter dated f'ay 3,1985, NpI inforred the imC staff of effective repairs nade to Section C of the cask, vacuun drying of the area between the inner and outer shells, a radiation survey of Section C following conpletion of the drying operation, and updating of the package drauings and operating and raintenance procedures. MPI also agreed not to use the cask pending our review.
As a direct result of the problens with the drain / vent lines in Sections C and C of the cask, the NRC staff reviewed the previous safety analysis for the cask which was originally approved in 1967. The r,ackaging is a steel encased, lead shielded shipping cask of circular cross-section.
The outer carbon steel shell is 7/0-inch thick, has a 30-inch On and is finned with 1/2-inch x 4-inch high fins spaced on 3-inch centers. The inner stainless steel shell is 1/4-inch thick. A nininun 6-inch lead shield is provided on the sides and ends. The cask is coe 4rised of two axially connected sections which are chosen fron four different sections.
The sections are connected in pairs to forn four cask configurations.
The sections are connected by 36, 3/4-16 UHF studs ecually spaced around 34-inch OD grooved flange rings which are welded to each section. An 0-ring or flat ring gasket provides a seal between the connected pairs which forn the cask configurations which range in cask length fron 33 to 114 inches. The cask weight configurations range fron 8,000 to 30,000 pounds and ray contain from 120,000 to 600,000 curies (1.9 to 9.4 thernal watts) of cobalt-60. The certificate of conpliance requires the raterial to rcet special forn radioactive raterial requirements.
In reviewinq the safety analysis for the cask, it was found, among other things, that the strenqth of the bolts connecting the sections in the middle of the cask was not addressed for the drop and puncture tests.
Prelininary calculations by the MC staff indicate that if the cask was dropped 40 inches onto the 6-inch diaracter punch, the cask could separate at the bolted joint with a loss of shielding and the limits of 10 CFR 571.51(a)(2) being excecded.
Also, the assur.ption nade in the original thernal analysis of an air gap between the lead and outer shell is not considered reasonable. The presence of a gap sheuld not be assuned because of " cold flew" properties of lead which tends to close the gaps. FRC staff calculations without the gap indicate rost of the lead will relt as a result of the t5ernal test requirenents in 10 CFR 571.73(c)(3) and possible loss of liquid lead due to a weld failure which could result in a loss of shielding and the limits of 10 CFP $71.51(a)(2) being exceeded. There is cnly one known cask fabricated to the design.
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lieutron Products Inc. In view of the foregoing and in the interests of public health and safety, we have detemined that all casks of this design should be withdrawn from use until a detemination can be nade that the package design neets the requirements of 10 CFR Part 71.
Accordingly, Certificate of Compliance No. 5364 for cask !!odel flo fiPI-67-0442 is hereby withdrawn. Any request for reinstatenent of the Certificate of Compliance nust provide sufficient infomation to demonstrate that the cask design neets the requirements of 10 CFR Part 71 and that any packages built to the design meet the design approved by the Connission.
This withdrawal of the Certificate of Compliance is effective imediately for any owner / users under the general license provisions of 10 CFR 971.12.
Sincerely, Original Signed W CHARLES E. F.ACDONALD Charles E. !!acDonald, Chief Transportation Certification Branch Division of Fuel Cycle and Itaterial Safety, INSS cc: f4r. Richard R. Rawl
.Departnent of Transportation Distribution:
fir. Robert E. Corcoran RH0degaarden (2)
Division of Radiation Control Docket File 201 West Preston Street NRC PDR Baltinore, !!D 21201 IE HQ Region I Department of Energy IMSS R/F ATTN: Ifr. Roy F. Garrison FCTC R/F DP-122.2 Washington, DC 20545 IRT Corporation ATTft: tir. Paul R. Moschka P.O. Box 35317 San Diego, CA 92138 Vcmont Yankee Electric Company ATTN: Licensing Engineering 1671 llorchester Road Framinghan, ftA 01701 a .J WMJW
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