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Reliability study of friction stir welded copper canisters containing Sweden's nuclear waste

Cederqvist, Lars LU and Öberg, Tomas (2008) In Reliability Engineering & System Safety 93(10). p.1491-1499
Abstract
The plan for the final disposal of spent fuel front Swedish nuclear power plants is to place it in copper canisters that are sealed and stored in a deep repository. The canisters will be sealed by friction stir welding (FSW) and the reliability of this process has now been evaluated. The reliability study was performed in three steps: first an optimization experiment to identify optimal process settings and establish the process window; then a demonstration experiment with welding tinder production-like conditions; and finally a postdemonstration series to evaluate an adjustment in the welding equipment. A process window was defined around the optimal process setting, i.e., the limits within which the welding variables must lie in order... (More)
The plan for the final disposal of spent fuel front Swedish nuclear power plants is to place it in copper canisters that are sealed and stored in a deep repository. The canisters will be sealed by friction stir welding (FSW) and the reliability of this process has now been evaluated. The reliability study was performed in three steps: first an optimization experiment to identify optimal process settings and establish the process window; then a demonstration experiment with welding tinder production-like conditions; and finally a postdemonstration series to evaluate an adjustment in the welding equipment. A process window was defined around the optimal process setting, i.e., the limits within which the welding variables must lie in order for the process to produce the desired result. In the demonstration experiment, a series of 20 scaling welds was carried out under production-like conditions. The maximum discontinuity in each weld-detected by non-destructive testing-was fitted to a generalized extreme value distribution. The 95% confidence interval for the maximum discontinuity in a production series of 4500 canisters was estimated at 4.5-7.7mm. The best estimate from the postdemonstration series suggests that the maximum size of a discontinuity will not exceed 2.3 mm. A main conclusion is that the FSW process produces reliable results, fulfilling the predetermined requirements for minimum copper thickness by a very good margin. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
friction stir welding, design of experiments, extreme value statistics, system reliability
in
Reliability Engineering & System Safety
volume
93
issue
10
pages
1491 - 1499
publisher
Elsevier
external identifiers
  • wos:000256985500010
  • scopus:43249108832
ISSN
0951-8320
DOI
10.1016/j.ress.2007.09.010
language
English
LU publication?
yes
id
78626709-2031-492f-ab47-c232ff18e88c (old id 1187289)
date added to LUP
2008-09-05 11:23:30
date last changed
2017-08-27 04:34:21
@article{78626709-2031-492f-ab47-c232ff18e88c,
  abstract     = {The plan for the final disposal of spent fuel front Swedish nuclear power plants is to place it in copper canisters that are sealed and stored in a deep repository. The canisters will be sealed by friction stir welding (FSW) and the reliability of this process has now been evaluated. The reliability study was performed in three steps: first an optimization experiment to identify optimal process settings and establish the process window; then a demonstration experiment with welding tinder production-like conditions; and finally a postdemonstration series to evaluate an adjustment in the welding equipment. A process window was defined around the optimal process setting, i.e., the limits within which the welding variables must lie in order for the process to produce the desired result. In the demonstration experiment, a series of 20 scaling welds was carried out under production-like conditions. The maximum discontinuity in each weld-detected by non-destructive testing-was fitted to a generalized extreme value distribution. The 95% confidence interval for the maximum discontinuity in a production series of 4500 canisters was estimated at 4.5-7.7mm. The best estimate from the postdemonstration series suggests that the maximum size of a discontinuity will not exceed 2.3 mm. A main conclusion is that the FSW process produces reliable results, fulfilling the predetermined requirements for minimum copper thickness by a very good margin.},
  author       = {Cederqvist, Lars and Öberg, Tomas},
  issn         = {0951-8320},
  keyword      = {friction stir welding,design of experiments,extreme value statistics,system reliability},
  language     = {eng},
  number       = {10},
  pages        = {1491--1499},
  publisher    = {Elsevier},
  series       = {Reliability Engineering & System Safety},
  title        = {Reliability study of friction stir welded copper canisters containing Sweden's nuclear waste},
  url          = {http://dx.doi.org/10.1016/j.ress.2007.09.010},
  volume       = {93},
  year         = {2008},
}