Control rod position indication system

• US 5,229,066 A
• Filed: 08/05/1991
• Issued: 07/20/1993
• Est. Priority Date: 08/05/1991
• 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: Heibel, Michael D., Impink, Albert J. Jr., Grobmyer, Louis R.
• Primary Examiner(s): Walsh, Donald P.
• Assistant Examiner(s): CARROLL, CHRISMAN DION
• Application Number:
  US07/740,354
• Time in Patent Office: 715 Days
• Field of Search: 376/258, 376/259, 376/254, 376/255, 364/559, 364/560, 364/167.01, 250/391, 250/392, 250/390.12
• US Class Current: 376/258
• CPC Class Codes: G21C 7/12 Means for moving control elements to desired position dropping rods in an emergency G21C9/02
• CPC Class Codes: G21C 7/36 Control circuits
• CPC Class Codes: Y02E 30/30 Nuclear fission reactors

Abstract

The present invention is a system which determines nuclear reactor control rod axial position using a deviation signature database generated from a current or reference signal pattern produced by one or more strings of axially dispersed fixed incore detector sections in the reactor core. The deviation signature database is produced by assuming deviant axial positions for the control rods in the core, calculating expected detector signals for the assumed positions and storing the deviation of expected signals from a calibration reference along with corresponding assumed rod positions. The signature database is periodically updated to take into account changed core conditions. When a change in detector responses is detected the system performs a signature analysis of the deviations in the signature database using the current deviation from the reference to search for the closest match. The change indicates not only the bank or individual rod that has moved but also the direction of movement allowing the search of the database to be circumscribed to the portion associated with the bank or individual rod and direction of movement. The closest match is used to incrementally search for the exact rod position by calculating expected response deviations for each assumed incremental move and comparing the expected response deviation to actual response deviations. If the system searches past the actual position, the last assumed position is output.

Claims

1. An axial rod position determination system for a control rod in a nuclear reactor core, said system comprising:

fixed incore detectors;

analytical, on-line signature means for periodically creating a response signature database of expected detector response deviations for assumed rod positions from a reference detector response produced at the current rod position by said fixed incore detectors; and

rod position determination means for continuously determining a moved rod position of the control rod by scanning the signature database for a signature match between the expected detector response deviations and current detector response deviations produced by said fixed incore detectors with the control rod at the moved rod position.

2. An axial rod position determination system for a control rod in a nuclear reactor core, said system comprising;

fixed incore detectors;

signature means for creating a response signature database of expected detector response deviations for assumed rod positions from a reference detector response produced at the current rod position by said fixed incore detectors, said signature database being divided into inward and outward movement directions from the current rod position and according to control rod bank and individual control rod;

rod position determination means for determining a moved rod position of the control rod by scanning the signature database for a signature match between the expected detector response deviations and current detector response deviations produced by said fixed incore detectors with the control rod at the moved rod position;

classification means for classifying the current detector responses according to direction and bank and individual control rod; and

said determination means scanning a portion of the signature database corresponding to the direction and the bank and individual control rod.

3. An axial rod position determination system for a control rod in a nuclear reactor core, said system comprising:

fixed incore detectors;

signature means for creating a response signature database of expected detector response deviations for assumed rod positions from a reference detector response produced at the current rod position by said fixed incore detectors; and

rod position determination means for determining a moved rod position of the control rod by scanning the signature database for a signature match between the expected detector response deviations and current detector response deviations produced by said fixed incore detectors with the control rod at the moved rod position and selecting a closest expected detector response deviation; and

incremental search means for incrementally searching for an incremental match between calculated expected detector response deviation and the current detector response deviation starting with the closest expected detector response deviation when the signature match is not found.

4. A rod position determination system for a control rod in a reactor core, said system comprising:

fixed incore detectors;

signature means for creating a response signature database of expected detector response deviations for assumed rod positions, a reference detector response produced at the current rod position by said fixed incore detectors and current core conditions, said signature database is divided into inward and outward move directions from the current rod position and according to control rod bank;

rod position determination means for determining a moved rod position of the control rod by scanning the signature database for a signature match between the expected detector response deviations and current detector response deviations produced by said fixed incore detectors with the control rod at the moved rod position and selecting a closest expected detector response when the signature match does not exist;

classification means for classifying the current detector responses according to direction and bank or individual control rod and said determination means scanning a portion of the signature database corresponding to the direction and the bank or individual control rod; and

incremental search means for searching for an incremental match between calculated expected detector responses and the current detector responses starting from the closest expected detector response when a signature match does not exist.

5. A position determination method for determining a position of a control rod in a reactor core using a fixed incore detector, comprising:

(a) creating a signature database of expected detector response deviations and corresponding rod positions;

(b) detecting a change in a detector signal producing a detector signal deviation;

(c) scanning the signature database for a match between the detector signal deviation and the expected detector response deviation;

(d) outputting the corresponding rod position when a match occurs;

(e) selecting, when a match does not occur, the closest match between the detector signal deviation and the expected detector response deviation to determine a closest rod position;

(f) incrementing the closest rod position by a predetermined step movement producing an incremented position;

(g) determining a calculated detector response deviation from the incremented position; and

(h) outputting the incremented position if the calculated detector response deviation matches the detector signal deviation.