US 5,179,515 A · Neutron flux detector positioning

Abstract

Fine and coarse resolvers are used to detect the length of cable withdrawn from a spool to provide an indication of the position of a neutron flux detector at the end of the cable. The position indicated by the resolvers when the neutron flux detector passes a withdrawn limit switch is stored in nonvolatile memory as an offset when the cable is first installed in a flux mapping system. Thereafter, the position indicated by the resolvers, each time the neutron flux detector passes the withdraw limit switch, is compared to the offset. If the difference between the two is significant, a warning is generated, but operation of the flux mapping system continues. During movement of the flux detector, the change in position between two readings of the resolvers is divided by an amount of time measured by a programmable interval timer to determine average speed. A warning is generated if the average speed is outside an expected range. The expected range may vary depending upon the position of the detector. The position indicated by the resolvers when the flux detector indicates a reduction in neutron flux due to the presence of grid straps is compared with predetermined grid strap positions to determine an accurate top of thimble limit.

Claims13

Dependent claims

A method of controlling withdraw of a strand from a storage unit, the strand having a total strand length, said method comprising the steps of:

(a) sensing a length of the strand extracted from the storage unit using a resolver, the resolver completing less than one revolution for the total strand length;
(b) performing speed and position diagnostics based upon the length of the strand sensed in step (a) and a previous length sensed a measured time interval earlier;
and
(c) calibrating an offset using an initial reading received from the resolver when an end of the strand reaches a known position after the strand is initially loaded into the storage unit.

1 more element

A system for controlling a length of strand withdrawn from a storage unit, the strand having a total strand length, comprising:

a reservoir for sensing the length of the strand extracted from the storage unit, said resolver completing less than one revolution for the total strand length;
and
diagnostic means for performing speed and position diagnostics based upon the length of the strand and a previous length sensed a measured time interval earlier;
a programmable interval timer for measuring the measured time interval between each sensing of the length;
a withdraw limit switch for sensing when an end of the strand reaches a withdraw limit position;
and
a processor for calibrating an offset using an initial reading received from said resolver when an end of the strand reaches the withdraw limit position and for detecting when the length sensed by said resolver, at each time said withdraw limit switch indicates the end of the strand has reached the withdraw limit position, does not correspond to the offset.

4 more elements

A method of controlling positioning of neutron flux detectors in a flux mapping system for a pressurized water nuclear reactor, the neutron flux detectors attached to ends of cables stored on spools and routed into thimbles, one of the thimbles having a top located a maximum distance from the spools, said method comprising the steps of :

(a) sensing resolver positions of resolver units, each resolver unit corresponding to one of the cables and including a coarse resolver completing less than one revolution when the corresponding cable is extended the maximum distance;
(b) receiving a withdraw limit signal from one of a plurality of withdraw limit switches when a corresponding flux detector on the corresponding cable reaches the one of the withdraw limit switches;
(c) calibrating each resolver unit by storing the resolver position as an offset when the withdraw limit signal is received after a corresponding cable is initially loaded on the reel in the flux mapping system;
(d) converting the resolver position to a cable length by subtracting the offset stored in step (c) and multiplying by a conversion factor;
(e) generating a warning when the cable length, produced by said converting performed when the withdraw limit switch is received after said calibrating has been performed, is different from zero by a predetermined amount;
and
(f) continuing operation of the flux mapping system when the warning is generated in step (e).

4 more elements

Dependencies are inferred from the claim text.

Neutron flux detector positioning

Life of this patent

Neutron flux detector positioning

Life of this patent

Abstract

Claims13