RU2797858C1 - Method for controlling the chipping of fuel pellets in the assembled fuel cell - Google Patents

Abstract

FIELD: nuclear power industry.

SUBSTANCE: invention relates to nuclear power, namely to a method for controlling the chips of fuel pellets in an assembled fuel cell. At the entrance of the detection units, slot collimators are additionally installed, one of which is equipped with a controlled screen that partially overlaps the collimator slot with a gap on the side of the small chord of the section of the fuel cell. The mechanism for controlling the movement of the fuel cell is additionally equipped with a rotation drive of the fuel cell. The fuel cell is moved. Counting pulses coming from gamma-ray detectors are processed, in particular, subtracted and summed. By the signal of the difference of the counting pulses, the possible presence of a chip in the gap zone of the fuel pellets is judged. When the difference is higher than the permissible threshold value, the fuel cell is stopped, a screen is inserted into one of the slot collimators and the fuel cell is rotated, after which, upon the appearance of an extremum of counting pulses at the output of the detector with this controlled collimator, a conclusion is made about the presence and magnitude of the chip of fuel pellets in the assembled fuel element.

EFFECT: increase in the reliability of detecting fuel pellet chips with the ability to control the presence and magnitude of fuel pellet chips in the assembled fuel cell.

1 cl, 2 dwg

Description

SUBSTANCE: invention relates to nuclear power industry and can be used at enterprises manufacturing fuel elements when developing methods for controlling fuel pellet chipping in an assembled fuel element (hereinafter referred to as a fuel element).

Known "Device for monitoring the continuity of the fuel column" according to the patent of the Russian Federation for the invention No. RU 2108631 C1, application: 97102876/25, 27.02.1997, IPC: G21C 17/00, G01N 9/24, G01N 23/08, in which control is carried out by passing a fuel element at a known speed through orthogonally mounted detection units. The counting rate at the outputs of the blocks is used to judge the size of the gap in the fuel pellets and the presence of a chip. However, a cleavage rejection value of 0.3 mm against the background of a fuel pellet diameter of ~9 mm ensures low control sensitivity near the “noise” level, which leads to an increase in the probability of occurrence of errors of the first and second kind in the control and rejection of fuel elements.

Known "Method of controlling the fuel column of a fuel element of a nuclear reactor and a device for its implementation (RF patent for invention No. RU 2483373 C2, application: 2011134934/07, 19.08.2011G21C 17/00 - prototype).

In this invention, to increase productivity, several detection units are installed in series, and to ensure the required uniformity of the pulling speed, current control of the position of the fuel element using photo sensors with sequential disconnection-connection of the pulling mechanisms.

The disadvantages of this technical solution is that the reliability of the detection of chipped fuel pellets when checking the gap does not increase significantly, because an increase in the count rate can be identified as an increase in the gap between the fuel pellets. In addition, it is not possible to control the presence and size of fuel pellet cleavage in the assembled fuel element.

The objective of the proposed technical solution is to create a method for monitoring the presence of fuel pellet chips in the assembled fuel element, which provides control of the length of the fuel column, the coordinates of the fuel column and components, control of single gaps, control of the total gap, but at the same time additionally providing the ability to control the presence and size of chipped fuel pellets in the assembled fuel element.

The solution to this problem is achieved by the fact that in the proposed method for monitoring fuel pellet chipping in the assembled fuel element of a nuclear reactor, which includes pulling the fuel element through detection units installed orthogonally to the fuel rod axis and containing sources and detectors of gamma radiation and subsequent analysis of the results obtained, according to the invention, slit collimators are additionally installed at the input of the detection units, one of which is equipped with a controllable screen that partially covers the collimator slot with a clearance on the side of the minor chord of the fuel element section, while the mechanism for controlling the movement of the fuel element is additionally equipped with a fuel element rotation drive, and the fuel element is moved, after which the counting pulses coming from the gamma radiation detectors are processed, in particular, subtracted and summed, while the signal of the difference of the counting pulses is used to judge the possible presence of a chip in the gap zone of the fuel pellets, if the difference is above the allowable threshold value, the fuel element is stopped, a screen is inserted into one of the slit collimators and the fuel element is rotated, after which, by the appearance of an extremum of counting pulses at the output of the detector with this controlled collimator, a conclusion is made about the presence and size of the fuel pellet chip in the assembled fuel element.

The essence of the invention is illustrated in the drawings, where in Fig. 1 shows a diagram of a device that implements the proposed method of control, in Fig. Figure 2 shows the state of the detection units during the translational drawing of the fuel rod (a) and during its rotation (b).

The proposed method can be implemented as follows.

The fuel rod 1 is moved by means of the driving rollers of the drives of the longitudinal displacement 2, the pressure rollers of which are simultaneously the total wheels of the sensors of the longitudinal displacement of the fuel rod 3. self-guided steady rest with driving rollers. Detection blocks, installed with working axes at 90° to each other, are placed in one control section and contain a gamma radiation source 5, a gamma radiation sensor 6. In one of the blocks, a slit collimator with a constant section window 7 is used, and in the other, with a window of variable section 8, a slit collimator with an additional screen and a mechanism for its movement was used.

In FIG. 2(a) shows the state of the detection units during the forward pull of the fuel rod.

In FIG. 2(a), both slit collimators are fully open and the flow of gamma quanta to sensors 6 is formed by the cross section of the fuel column of fuel rod 1 moving in a perpendicular plane and slit collimators 7 and 8 with a slit lying in the image plane. Upon receipt of a differential signal from the gamma radiation sensors that exceeds the threshold voltage value, the movement of the fuel rod is stopped, the pressure rollers are retracted, and the rollers of the drive steady are clamped for subsequent rotation of the fuel rod.

In FIG. 2(b) shows the state of the detection units during the subsequent rotation of the fuel rod.

The screen of the collimator 8 is introduced into the window with the formation of a passage of gamma radiation along the minor chord of the fuel pellet section, thereby covering a significant part of the fuel gap and the fuel element begins to rotate around the longitudinal axis. If there is a chip on the fuel pellet, the count rate at the output of the corresponding gamma radiation sensor will have a pronounced extremum when the chip crosses the radiation flux from the source, while the value of this extremum will be proportional to the fuel pellet chip.

The use of the proposed technical solution will make it possible to create a method for monitoring the presence of fuel pellet chips in the assembled fuel element, which provides control of the length of the fuel column, the coordinates of the fuel column and components, control of single gaps, control of the total gap, and additionally provides the ability to control the presence and size of chipped fuel pellets in the assembled fuel element. heat generating element.

Sources of information taken into account when filing an application for an invention.

1 RF patent No. 2108631 C1, IPC: G21C 17/00, G01N 9/24, G01N 23/08, publ. 04/10/1998

2 RF patent No. 2483373 C2, IPC: G21C 17/00, publ. May 27, 2013

Claims (1)

A method for controlling fuel pellet chipping in an assembled fuel element of a nuclear reactor, which includes pulling the fuel element through detection units installed orthogonally to the fuel rod axis and containing sources and detectors of gamma radiation and subsequent analysis of the results obtained, characterized in that slit collimators are additionally installed at the entrance of the detection units , one of which is equipped with a controllable screen that partially covers the collimator slot with a gap on the side of the minor chord of the fuel element section, while the fuel element movement control mechanism is additionally equipped with a fuel element rotation drive, and the fuel element is moved, after which the counting pulses coming from the detectors gamma radiation is processed, in particular, subtracted and summed, while the signal of the difference of the counting pulses is used to judge the possible presence of a chip in the gap zone of the fuel pellets, while, if the difference is above the permissible threshold value, the fuel element is stopped, the screen is inserted into one of the slotted collimators and rotate the fuel element, after which, by the appearance of an extremum of counting pulses at the output of the detector with this controlled collimator, a conclusion is made about the presence and size of the fuel pellet chip in the assembled fuel element.

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