Induced nuclear reactions: processes – systems – and elements – Testing – sensing – measuring – or detecting a fission reactor... – Position detection
Reexamination Certificate
2000-09-25
2003-04-15
Carone, Michael J. (Department: 3641)
Induced nuclear reactions: processes, systems, and elements
Testing, sensing, measuring, or detecting a fission reactor...
Position detection
C376S245000, C073S625000
Reexamination Certificate
active
06549600
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method and a device for inspecting a fuel element in a nuclear reactor. Such a fuel element includes a bundle of fuel rods. At one end of the fuel rods is a head part, and at the other end a foot part. Situated between the head and foot parts are spacers disposed one above another at axial spacings. Fuel elements in boiling water reactors are usually further surrounded by boxes.
As a rule, these fuel elements have a square cross section, that is to say the outer surfaces of the fuel element, which are formed by the outer surfaces of the head and foot parts and of the spacers or the fuel element box, are situated opposite one another in pairs. In the ideal case, two outer surfaces of a spacer are in each case parallel to one another and to the corresponding outer surfaces of the fuel element foot or head.
Wear phenomena and damage to the fuel elements can occur during operation of the reactor. Thus, for example, the cladding tube wall of the fuel rods can corrode and/or water can penetrate into individual fuel rods.
The intensive neutron emission to which the fuel element is exposed leads to a radiation-induced growth of the fuel rods and, possibly, also of the fuel element box. Inhomogeneities in the distribution of the thermal energy and the neutron flux render the growth in length dependent on location, and this can lead to bending, bowing and twisting of the fuel element. Due to irradiation and corrosion, the webs from which the spacers are produced are also subjected to growth which depends, moreover, on the rolling direction during the rolling-out of the sheet metal used.
Since the fuel elements in the reactor core are seated at a mutual spacing of only a few millimeters, such changes falsify the physical states for which the reactor operation is configured. Moreover, there are problems in removing and inserting fuel elements when the spacers have become wider or are deformed in a barrel-shaped fashion.
Usually, spent fuel elements are extracted from the reactor core in time intervals of approximately one year. The remaining fuel elements are relocated, and samples of them are checked for damage. This investigation must be carried out under water, since the irradiated fuel element is highly radioactive and must be cooled because of the development of heat during the decay of fission products. To date, the underwater inspection has mainly been undertaken using video cameras with the aid of which it is possible to detect external damage to the fuel elements such as, for example, spacers with broken corners. U.S. Pat. No. 4,605,531 discloses devices which scan the fuel elements with the aid of ultrasonic probes. For such investigations, the fuel element is brought into a defined position relative to the probes used. It is possible thereby to find damage to fuel rod cladding tube walls into which water has penetrated.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method and a corresponding device for inspecting a fuel element which overcome the above-mentioned disadvantages of the heretofore-known methods and devices of this general type and which allow to detect changes in a fuel element in a simple way.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for inspecting an irradiated fuel element in a nuclear power plant, the method includes the steps of:
measuring, with a measuring device, a spacer of a fuel element for providing measurements of the spacer;
measuring, with the measuring device, a calibration rod for providing measurements of the calibration rod, the calibration rod having known dimensions; and
calibrating the measurements of the spacer by using the measurements of the calibration rod.
In accordance with another mode of the invention, a measured value for a spacing between the outer surfaces and a further measured value for a spacing between the subareas is formed for respective two points situated opposite one another on two outer surfaces of the spacer pointing in opposite directions and respectively situated opposite one another on two subareas of the calibration rod pointing in the opposite directions; and the measured value for the spacing between the outer surfaces is converted into a calibrated measured value by using the known dimensions of the calibration rod and the further measured value for the spacing between the subareas.
In accordance with yet another mode of the invention, further subareas of the calibration rod are measured, the further subareas pointing in the opposite directions and being provided offset relative to the subareas of the calibration rod.
In accordance with a further mode of the invention, further subareas of a further calibration rod are measured, the further subareas pointing in the opposite directions and being provided offset relative to the subareas of the calibration rod.
With the objects of the invention in view there is also provided, a method for inspecting an irradiated fuel element, the method includes the steps of:
providing, in a nuclear power plant, a fuel element having a bundle of fuel rods, end pieces respectively configured as a foot piece and a head piece at respective ends of the bundle, a spacer penetrated by the fuel rods between the end pieces, and further structural elements;
positioning the fuel element with one of the end pieces or the spacer against a frame, the frame defining a z-axis of a Cartesian reference system;
holding, on the frame, a calibration rod having known dimensions in an x-direction of the Cartesian reference system;
measuring a respective relative position of two outer surfaces of the spacer and of corresponding subareas of the calibration rod, the two outer surfaces of the spacer extending along a y-direction of the Cartesian reference system; and
forming, with the aid of the known dimensions of the calibration rod, at least one calibrated maximum value for a spacing between the two outer surfaces of the spacer from measured values obtained during the measuring step.
In accordance with another mode of the invention, a relative position of the fuel element is varied in the Cartesian reference system for measuring further outer surfaces of the spacer by using probes and the calibration rod.
In accordance with yet another mode of the invention, the probes measure further outer surfaces of the spacer and corresponding further subareas of the calibration rod, the further outer surfaces and the further subareas extending along the x-direction.
In accordance with a further mode of the invention, the probes measure subareas of a further calibration rod, the subareas of the further calibration rod extending along the x-direction.
In accordance with another mode of the invention, further subareas of the calibration rod are measured, the further subareas being offset relative to the subareas of the calibration rod.
In accordance with another mode of the invention, given subareas of a further calibration rod are measured; and further given subareas of the further calibration rod are scanned, the further given subareas being offset relative to the given subareas of the further calibration rod.
With the objects of the invention in view there is also provided, a device for inspecting an irradiated fuel element in a nuclear reactor, including:
a positioning device for positioning a fuel element having a spacer with two outer surfaces pointing in opposite directions;
a measuring device operatively connected to the positioning device, the positioning device fixing a relative position of the spacer relative to the measuring device, the measuring device having a calibration rod with known dimensions and two subareas respectively pointing in the opposite directions, the measuring device being directed toward the two outer surfaces of the spacer and the two subareas of the calibration rod for forming measured values defining relative positions of the outer surfaces and the subareas; and
a computer connected to the measuring device and
Beier Martin
Hummel Wolfgang
Kindlein Wolfram
Uckert Jürgen
Carone Michael J.
Framatome ANP GmbH
Greenberg Laurence A.
Locher Ralph E.
Matz Daniel
LandOfFree
Method and device for inspecting a fuel element in a nuclear... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for inspecting a fuel element in a nuclear..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for inspecting a fuel element in a nuclear... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3061700