US5402570A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for repairing boiling water reactor shrouds
Assignee: MPR Associates Inc
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Filing: 1994-02-02
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Granted: 1995-04-04
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Expires: 2014-02-02
Abstract
Abstract A method of repairing nuclear reactor core shrouds having horizontal cracks in heat affected zones of welds includes applying vertical compressive forces to the shroud in situ to urge opposed surfaces of the cracks toward one another. A plurality of tie rods, angularly spaced about the shroud periphery, is used to selectively apply the longitudinally compressive forces. Preferably, the method utilizes existing hardware secured to the shroud for attaching the tie rods thereto. The tie rods may be used in connection with horizontal and/or vertical spacers inserted between the shroud and the reactor vessel. Horizontal spacers serve to resist horizontal seismic loads and hold the shroud in place in spite of cracking. Vertical spacers resist vertically upward loads resulting from main steam line breaks.
Inventors
- 👤 Sterling J. Weems
- 👤 Noman Cole
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 15:48
CPC Classifications
B; B23; B23P; B23P6/00; B23P6/04; G; G21; G21C; G21C17/00; G21C17/003; G21C17/01; G21C19/00; G21C19/20; G21C19/207; Y; Y02; Y02E; Y02E30/00; Y02E30/30; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/4935; Y10T29/49352; Y10T29/49718; Y10T29/49732; Y10T29/49739; Y10T29/49741; Y10T29/49748
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
82 words
A method of repairing a nuclear reactor core shroud having at least one horizontally extending crack along a heat affected zone of a weld joining adjacent shroud plate segments, said method comprising the steps of: (a) shutting down the reactor; (b) urging opposing surfaces of said crack toward one another by applying axially compressive forces to said shroud along substantially all of the shroud length; and (c) maintaining application of the axially compressive forces after the reactor has been restored to operation.
Claim 2
Independent Claim
82 words
A method of repairing a nuclear reactor core shroud having at least one horizontally extending crack along a heat affected zone of a weld joining adjacent shroud plate segments, said method comprising the steps of: (a) shutting down the reactor; (b) urging opposing surfaces of said crack toward one another by applying axially compressive forces to said shroud along substantially all of the shroud length; and (c) maintaining application of the axially compressive forces after the reactor has been restored to operation.
Claim 3
Dependent Claim
70 words
The method of claim 1 wherein steps (b) and (c) include the steps of: (d) securing a plurality of tie rods to sites on the shroud adjacent the top and bottom of the shroud at a respective plurality of angularly spaced locations about the shroud periphery; and (e) urging the sites adjacent the top of the shroud toward the sites adjacent the bottom of the shroud along respective tie rods.
Claim 4
Dependent Claim
66 words
The method of claim 2 wherein step (e) includes the steps of: (f) attaching the lower end of each tie rod to structure secured to the bottom of the shroud; and (g) threadedly engaging the upper end of each tie rod such that selective tightening of the threaded engagement forcefully urges a respective site adjacent the top of the shroud toward the bottom of the shroud.
Claim 5
Dependent Claim
27 words
The method of claim 3 wherein step (f) includes hooking the lower end of each tie rod onto said structure secured to the bottom of the shroud.
Claim 6
Dependent Claim
28 words
The method of claim 3 wherein step (f) includes engaging the lower end of each tie rod with a support member supporting said shroud on the reactor vessel.
Claim 7
Dependent Claim
22 words
The method of claim 3 further comprising the step of applying radially inward compressive forces from said tie rods to said shroud.
Claim 8
Dependent Claim
28 words
The method of claim 3 further comprising the step of inserting radial spacers at plural angularly spaced locations in abutting relation between said shroud and the reactor vessel.
Claim 9
Dependent Claim
40 words
The method of claim 7 further comprising the step of inserting vertical spacers at plural angularly spaced locations between structure on said shroud and structure on said vessel to preclude upward vertical movement of said shroud relative to said vessel.
Claim 10
Dependent Claim
28 words
The method of claim 1 further comprising the step of inserting radial spacers at plural angularly spaced locations in abutting relation between said shroud and the reactor vessel.
Claim 11
Dependent Claim
41 words
The method of claim 1 further comprising the step of inserting vertical spacers at plural angularly spaced locations between structure on said shroud and structure on the reactor vessel to preclude upward vertical movement of said shroud relative to said vessel.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-04-03 | 1998-10-03 | 1999-04-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-04-03 | 2002-10-03 | 2003-04-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-04-03 | 2006-10-03 | 2007-04-04 | $7700.00 | Window Closed / Lapsed |