Machine and method for decontaminating nuclear steam generator channel head

• US 4,219,976 A
• Filed: 08/01/1978
• Issued: 09/02/1980
• Est. Priority Date: 08/01/1978
• Status: Expired due to Term

• Current Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Shaffer, Robert, Burack, Robert D.
• Primary Examiner(s): Smith, Gary L.
• Application Number:
  US05/930,091
• Time in Patent Office: 763 Days
• Field of Search: 51/319, 51/320, 51/321, 51/411, 51/415, 51/416, 134/8, 134/24, 134/167 R, 134/168 R, 134/180, 134/181
• US Class Current: 451/38
• CPC Class Codes: F22B 37/005 Positioning apparatus specially adapted therefor F22B37/64 takes precedence
• CPC Class Codes: G21F 9/00 Treating radioactively contaminated material; Decontamination arrangements therefor

Abstract

The machine comprises a first assembly including a vertical post and a carriage track with a movable carriage thereon, the carriage track being pivotally secured to the upper end portion of the post so that the assembly can be collapsed to a size permitting entry into the channel head through a manway, with the assembly being sufficiently light in weight to permit its installation in the channel head by no more than two individuals, the machine further including a separate horizontal support beam and a separate curved track which are independently separably secured to the vertical post and to the outer end of the carriage track so that a generally quadrantally shaped frame is provided, the carriage track carrying an adjustable decontamination blaster means, and means are provided for moving the carriage along the carriage track and for swinging the carriage track both horizontally and vertically in the frame so that the decontamination means has the capability of sweeping past substantially all of the interiorly facing walls in the channel head. The method of carrying out the decontamination of all of the interiorly facing walls in the space in the channel head is accomplished by traversing the areas to be decontaminated by energizing selective drive means for successive sweeps at rates corresponding to the area to be traversed and then stepping the blaster means to different positions and varying the sweep rate in accordance with the different position.

Claims

1. A decontamination machine for decontaminating substantially all of the interiorly facing walls on one side of a divider wall in a channel head of a nuclear steam generator having a manway, comprising:

a first assembly comprising a vertical post and a carriage track carrying a movable carriage, said carriage track being pivotally secured to the upper end portion of said post to permit the assembly to be collapsed to a size permitting entry through said manway into said channel head, said assembly being sufficiently lightweight to permit the manipulation and installation thereof in said channel head by no more than two individuals in a location in which said vertical post is closely adjacent the vertical center line of said divider wall;

a horizontal support beam including fastener means at its radially inner end adapted to be separably secured to the upper end portion of said vertical post;

a curved track shaped to complete a generally quadrantal shaped frame also including said post and said beam, said curved track means including fastener means at both ends adapted to be separably secured to the radially outer end of said horizontal beam and the lower end portion of said vertical post, said curved track engaging the outer end of said carriage track in movable relation;

both said beam and said curved track also being sufficiently ligthweight to permit their manipulation and attachment to said first assembly by no more than two individuals;

adjustable decontamination blaster means attached to said carriage; and

means for moving said carriage along said carriage track, and means for swinging said carriage track both horizontally and vertically so that said decontamination means has the capability of sweeping past substantially all said interiorly facing walls of said channel head.

2. A decontamination machine according to claim 1 wherein:

said carriage moving means comprises a first DC drive motor;

said means for swinging said carriage track horizontally comprises a second DC drive motor; and

said means for swinging said carriage track vertically comprises a third DC drive motor.

3. A machine according to claim 2 wherein:

said first and third drive motors are carried by said carriage track; and

said second drive motor is carried by said post.

4. A machine according to claim 1 wherein:

said vertical post is vertically extensible for wedging said post into a vertical position closely adjacent the middle area of the dividing wall.

5. A machine according to claims 2 or 3 including:

means to energize each of said DC motors independently and to control their speed.

6. A machine according to claims 2 or 3 including:

means for shielding each of said DC motors and associated gearing to protect from decontamination blasting material.

7. A machine for decontaminating substantially all of the interiorly facing wall surfaces on one side of a divider wall and a channel head, having a manway, of a nuclear steam generator, comprising:

a machine frame which, as assembled in the space in said channel head, is generally quadrantal in outline and includes a vertical post, a horizontal support beam, and a curved track forming the outline, both the support beam and the curved track being separably secured to said vertical post and to each other, the support beam having its inner end secured to the upper end portion of the post, and the curved track having its lower inner end secured to the lower end portion of said post;

a carriage track having its radially inner end pivotally secured to the upper end portion of said vertical post, and its radially outer end engaging said curved track, so that said track can be pivoted from a position generally paralleling said support beam to a position generally paralleling said vertical post;

a carriage movable in a longitudinal direction on said carriage track;

decontamination means carried by said carriage, said decontamination means including nozzle means adjustable to a number of different angular positions;

first drive means for moving said carriage along said carriage track;

second drive means carried by said vertical post for pivoting the intermediate part of said post through approximately 180 degrees from one position parallel to said dividing wall to the opposite position also generally parallel to the dividing wall; and

third drive means carried by said carriage track for moving the outer end of said track along said curved track.

8. The method for decontaminating substantially all the interiorly facing walls of a space defined by an upper tube sheet, a divider wall and a channel head wall of a nuclear steam generator, with a directionally adjustable blast nozzle carried by a carriage on a track, with the blast nozzle being movable radially in and out on the track by one drive, and the track being swingable horizontally by a second drive, and swingable vertically by a third drive, comprising:

traversing the area of said tube sheet by energizing said second drive for successive sweeps at a rate according to the radial position of said carriage on said track, and energizing said one drive between successive sweeps to position said carriage on said track;

traversing the area of said divider wall by energizing said third drive for successive sweeps at a rate according to the radial position of said carriage on said track, and energizing said one drive between these successive sweeps to position said carriage on said track;

positioning said carriage at its radially outer position and then traversing the area of said channel head wall by energizing said second drive for successive sweeps at a rate according to the length of each of these sweeps along the channel head wall, and energizing said third drive between these successive sweeps to successively step said track between opposite generally horizontal and generally vertical positions.