Patent Description:
Radionuclides are used in various fields of technology and science, as well as for medical purposes. Usually, radionuclides are produced in research reactors or cyclotrons. Since the number of facilities for commercial production of radionuclides is limited and expected to decrease, it is desired to provide alternative production sites.

A commercial nuclear reactor can be used for producing radionuclides. In particular, conventional aero-ball measuring systems or other instrumentation tube systems of the commercial reactor can be modified and/or supplemented to enable an effective and efficient production of radionuclides. Some of the instrumentation tubes for example of a commercial aero-ball measuring system or Traversing Incore Probe (TIP) system are used to guide the irradiation targets into the reactor core and to lead the activated irradiation targets out of the reactor core. The activation of the targets is optimized by positioning the irradiation targets in predetermined areas of the reactor core having a neutron flux sufficient for converting the parent material in the irradiation targets completely into the desired radionuclide.

For example, <CIT> describes a radionuclide generation system comprising:.

The target drive system is typically pneumatically operated, which means that a pressurized gas is driven through the conduit system of the target drive system so as to displace the irradiation targets from one location to another within the radionuclide generation system.

When operating the radionuclide generation system, it is important to be able to count the targets going in and out of the nuclear reactor core in order to ensure that all the targets which have entered the core also leave the core.

However, the sensors described in <CIT> are not entirely satisfactory.

Indeed, due to the pneumatic drive, most of the targets typically move through the conduits of the transport system as target trains, in which the targets are in contact with each other at their axial ends.

<CIT> describes apparatuses and methods produce radioisotopes in instrumentation tubes of operating commercial nuclear reactors.

The inventors of the present invention have found that the existing sensor arrangements, comprising one single sensor at each counting location, do not allow reliably counting the targets of such target trains. Indeed, these targets are vibrating and rotating transversally in the conduit, i.e. moving perpendicularly to their primary movement direction through the conduit, which makes recognition of multiple targets very close to each other very difficult with existing systems, because it is not possible to resolve their geometric profile or the gaps between the carriers.

One aim of the invention is therefore to provide a target transport system for a radionuclide generation system, which allows accurately and reliably counting the number of targets entering or exiting the core of the nuclear reactor.

For this purpose, the invention relates to a target transport system according to claim <NUM>.

The target transport system may further comprise one or more of the features of claims <NUM> to <NUM>, taken alone or according to any technically possible combination.

The invention also relates to a radionuclide generation system according to claim <NUM>.

The radionuclide generation system may further comprise one or more of the features of claims <NUM> or <NUM>, taken alone or according to any technically possible combination.

The invention also relates to a method for counting irradiation targets according to claim <NUM>.

The method may further comprise one or more of the features of claims <NUM> to <NUM>, taken alone or according to any technically possible combination.

The invention will be better understood upon reading the following description, given only by way of example, and with reference to the appended drawings, where:.

The invention relates to a target transport system <NUM> for a radionuclide generation system. The radionuclide generation system is intended for producing activated irradiation targets in a nuclear reactor.

The target transport system <NUM> is in particular located in a nuclear reactor, and for example at least partially in a core of a nuclear reactor.

As shown in <FIG> and <FIG>, the target transport system <NUM> comprises:.

The conduit <NUM> has a central axis A, defining an axial direction of the conduit <NUM>. The conduit <NUM> for example has a circular cross-section.

The target drive system <NUM> is advantageously pneumatically operated, and for example uses a pressurized gas, such as nitrogen or air, for driving the irradiation targets <NUM> through the conduit <NUM>. The target drive system <NUM> for example comprises a source of pressurized gas.

Preferably, the target drive system <NUM> comprises one or more pneumatically operated valve batteries (not shown) for separate control of the insertion and transport of the irradiation targets <NUM> through the conduit <NUM>. Moreover, the target drive system <NUM> may further comprise a gate system (not shown) including several mechanical and/or electromechanical devices configured to guide the irradiation targets <NUM> into selected guide tubes in the reactor core, for example into selected conduits of the instrumentation tube system and instrumentation fingers in the reactor core.

The counting system <NUM> comprises at least two distance sensors <NUM>, each configured for measuring a radial distance d<NUM>, respectively d<NUM>, between the distance sensor <NUM> and the irradiation target <NUM>. In this context, the "radial distance" is measured along a radius of the conduit <NUM>. The distance sensors <NUM> each output a distance signal s<NUM>(t), s<NUM>(t).

The distance sensors <NUM> are preferably inductive sensors, and for example eddy current sensors. Inductive sensors are able to withstand high radiation doses, and their output signal is further not disturbed by the radiation of the passing irradiation targets <NUM>. The signal output of each inductive sensor is proportional to the distance between the sensor and the irradiation target <NUM>. The cut-off frequency of the distance sensors <NUM> is chosen depending on the geometry and speed of displacement of the irradiation targets <NUM>. It is for example equal to <NUM>. The sampling rate is for example greater than or equal to <NUM> kilosample/s.

The inductive sensors are preferably analog sensors.

The at least two distance sensors <NUM> are arranged at a same axial position along the conduit <NUM>. They are regularly spaced along the circumference of the conduit <NUM> with a constant angular spacing.

More particularly, in the target transport system <NUM> according to the first embodiment shown more particularly in <FIG>, the counting system <NUM> comprises exactly two distance sensors <NUM> at a given axial location along the conduit <NUM>, these distance sensors <NUM> facing each other along a radial direction of the conduit <NUM>. The two distance sensors <NUM> are spaced at an angle of <NUM>° from one another. They are arranged along the same axis.

The two distance sensors <NUM> are arranged symmetrically relative to a median plane of the conduit <NUM>, passing through the central axis of the conduit <NUM>.

Each distance sensor <NUM> operates with a different carrier frequency than the other distance sensor(s) <NUM> in order to avoid interference.

As shown in <FIG>, the counting system <NUM>, and more particularly the distance sensors <NUM>, are preferably arranged at a straight portion of the conduit <NUM>.

The target drive system <NUM> is in particular configured for driving the irradiation targets <NUM> through the conduit <NUM> in such a manner than they pass in front of the distance sensors <NUM> with a constant speed.

In the embodiment shown in <FIG>, the target transport system <NUM> further comprises a sensor support <NUM> mounted on said conduit <NUM>. The sensor support <NUM> is not shown in <FIG> and <FIG> to simplify the drawings.

In this example, the distance sensors <NUM> are mounted on the sensor support <NUM> such that no obstacle for the sensor measurement is located between the distance sensor <NUM> and the interior of the conduit <NUM>. In this context, obstacles for the sensor measurement are obstacles which modify the sensor signal, for example obstacles made of a metallic material. In particular, no portion of the conduit <NUM> extends radially between the distance sensor <NUM> and the interior of the conduit <NUM>.

The sensor support <NUM> is in particular configured to be pressure-tight.

A sensor support <NUM> according to an example is shown more particularly in <FIG> and <FIG>. In this example, the sensor support <NUM> comprises a central body <NUM> delimiting a central axial passage <NUM> intended for the passage of the irradiation targets <NUM>. More particularly, as shown in <FIG>, the conduit <NUM> is interrupted at the sensor support <NUM> and extends on either side of the sensor support <NUM> in an axial direction thereof. The central axis A of the conduit <NUM> and the central axis D of the central axial passage <NUM> are aligned.

The central passage <NUM> for example has a circular cross-section.

For each distance sensor <NUM>, the central body <NUM> further comprises a through-hole <NUM>, intended for receiving the distance sensor <NUM>. The through-hole <NUM> extends through the central body <NUM> and opens into the central axial passage <NUM>. In the example shown in <FIG> and <FIG>, the sensor support <NUM> comprises two through-holes <NUM> facing each other across the central axial passage <NUM>. Each distance sensor <NUM> is arranged in a respective through-hole <NUM> so as to be able to measure the radial distance between the distance sensor <NUM> and an irradiation target <NUM> passing through the central axial passage <NUM>. According to the example shown in <FIG>, the diameter of the central axial passage <NUM> is constant from one axial end <NUM> of the central body <NUM> to the other. The diameter of the central axial passage <NUM> is in particular equal to the inner diameter of the conduit <NUM>.

Optionally, the sensor support <NUM> further comprises a tubular insert (not shown) arranged in front of the distance sensors <NUM> inserted in the through-holes <NUM>. The inner diameter of the tubular insert is approximatively equal to the inner diameter of the conduit <NUM>. The tubular insert is made of a material which does not influence the measurements of the distance sensors <NUM>, and in particular of a synthetic material, for example plastic, in particular PEEK (Polyether ether ketone). The purpose of this tubular insert is to protect the distance sensor's surfaces, and to prevent a collision of the irradiation targets <NUM> with the edges of the sensor support <NUM>.

The sensor support <NUM> further comprises, at each axial end <NUM> of the central body <NUM>, a fitting <NUM> configured for mounting the sensor support <NUM> onto the conduit <NUM>. More particularly, in the example shown in <FIG>, where the conduit <NUM> is interrupted at the sensor support <NUM>, each fitting <NUM> is mounted on a respective end of the conduit <NUM>.

The fitting <NUM> is connected to the central body <NUM> and to the conduit <NUM> in a fluid-tight manner, for example through adapted sealing gaskets. In the example shown in <FIG>, the central body <NUM> comprises, at each of its axial ends <NUM>, an enlarged portion <NUM> which delimits a seat <NUM> receiving the fitting <NUM> in a fluid-tight manner.

The distance sensors <NUM> are advantageously mounted on the sensor support <NUM> so as to be displaceable relative thereto along a radial direction. This possibility of displacement allows adjusting the position of the distance sensors <NUM> along a radial direction.

Advantageously, the sensor support <NUM> comprises displacement means configured for displacing the distance sensors <NUM> along the radial direction. In the example shown in <FIG>, these displacement means comprise a piston <NUM> connected to the distance sensor <NUM>, for example through corresponding threads, and a piston cover <NUM> provided on the central body <NUM> and delimiting a piston chamber extending around the through-hole <NUM>. The piston <NUM> is movable along a radial direction inside the piston chamber relative to the central body <NUM>, this movement resulting in a displacement of the distance sensor <NUM> in the radial direction.

The central body <NUM> is advantageously made of metal, and for example comprises steel, for example stainless steel, and/or aluminum.

According to the invention, the transport system <NUM> further comprises a calculator <NUM>, such as a computer. The calculator <NUM> in particular comprises a processor <NUM>, a memory <NUM> and a media reader <NUM>.

In this example, the calculator <NUM> interacts with a computer program product that contains program instructions to be carried out by the processor <NUM>. The computer program product is stored on a data carrier.

The data carrier is a medium that can be read by the calculator <NUM>, usually by the processor <NUM> via the media reader <NUM>. The readable data carrier is a medium adapted for storing instructions and capable of being coupled to a bus of a computer system. For example, the readable data medium is a floppy disk, optical disk, CD-ROM, magnetooptical disk, ROM, RAM memory, EPROM memory, EEPROM memory, magnetic card, optical card, USB stick, or SSD disk.

The computer program product can be loaded by the processor <NUM> of the calculator <NUM> and is adapted to implement a target counting method according to the invention when the computer program is run on the processor <NUM>. The target counting method will be described in detail in the continued description.

In a second example, the computer <NUM> comprises one or more programmable logic components, such as FPGAs (Field Programmable Gate Array), or such as dedicated integrated circuits, such as ASICs (Application Specific Integrated Circuits) adapted to carry out the target counting method according to the invention.

In a third example, the computer <NUM> comprises a central processing unit (CPU) and a graphics processing unit (GPU), with the GPU acting as a co-processor, which are adapted to carry out the target counting method according to the invention.

The target counting method according to the invention will now be described with reference to <FIG> and <FIG>.

The distance signals s<NUM>(t), s<NUM>(t) shown in the graph in <FIG> correspond to the distance signals obtained when using the target transport system <NUM> according to the first embodiment of the invention, in which the counting system <NUM> comprises exactly two distance sensors <NUM> at a considered axial location along the conduit <NUM>. In addition, the distance signals s<NUM>(t), s<NUM>(t) were obtained during the passage of twelve irradiation targets <NUM> through the conduit <NUM>.

In a first step <NUM> of the method, the calculator <NUM> receives the distance signals s<NUM>(t), s<NUM>(t) obtained by the distance sensors <NUM> during the passage of the irradiation targets <NUM>. The distance signals s<NUM>(t), s<NUM>(t) correspond to the radial distance d<NUM>, d<NUM> between the irradiation target <NUM> and the respective distance sensor <NUM> as a function of time or are proportional thereto. These distance signals s<NUM>(t), s<NUM>(t) are shown in <FIG>. As can be seen on this Figure, the distance signals s<NUM>(t), s<NUM>(t) have a chaotic component, which is due to the movement of the irradiation targets <NUM> perpendicular to the axial direction, away or towards the distance sensors <NUM>. Due to this chaotic component, it is not possible to reliably detect the passage of an irradiation target <NUM> in front of the distance sensor <NUM> based on the distance measurement obtained by only one of the distance sensors <NUM>.

According to the invention, in a second step <NUM>, the calculator <NUM> calculates an intermediate signal sint(t) based on the distance signals s<NUM>(t), s<NUM>(t). More particularly, the amplitude of the intermediate signal sint(t) is linearly related to the sum of the distance signals s<NUM>(t), s<NUM>(t) obtained by the distance sensors <NUM>, and for example proportional to or equal to the sum of the distance signals s<NUM>(t), s<NUM>(t) obtained by the distance sensors <NUM>. The amplitude of the intermediate signal sint(t) is linearly related to the diameter profile of the irradiation targets <NUM> passing through the conduit <NUM>. In this context, the diameter profile of an irradiation target <NUM> corresponds to the diameter of the irradiation target <NUM> as a function of the distance from one end of the target <NUM>. Since an irradiation target <NUM> passes the distance sensors <NUM> at a constant speed, this diameter profile can also be expressed as a function of time.

In the first embodiment of the invention, in which the counting system <NUM> comprises exactly two distance sensors <NUM> at a given axial location along the conduit <NUM>, the second step <NUM> advantageously comprises summing the distance signals s<NUM>(t), s<NUM>(t) from the two distance sensors <NUM>. In this embodiment, the intermediate signal sint(t), shown in <FIG>, corresponds to the sum of the two distance signals s<NUM>(t), s<NUM>(t). As can be seen in this Figure, the summing of the two distance signals s<NUM>(t), s<NUM>(t) removes the chaotic component due to the movements of the irradiation targets <NUM> perpendicular to the axial direction of the conduit <NUM>.

In this context, the sum of the distance signals s<NUM>(t), s<NUM>(t) is related to the diameter profile dtarget(t) of the irradiation targets <NUM> by the following formula: dtarget(t) = dconctuit - (s<NUM>(t) + s<NUM>(t)), where dconduit is the inner diameter of the conduit <NUM>.

In a third step <NUM>, the calculator <NUM> determines the number of irradiation targets <NUM> passing through the conduit <NUM> based on the intermediate signal sint(t).

More particularly, the determination of the number of irradiation targets <NUM> passing through the conduit <NUM> comprises the application of a pattern recognition algorithm to the intermediate signal sint(t).

According to an example, the pattern recognition algorithm is an edge detection algorithm.

More particularly, application of the edge detection algorithm comprises the application of a comparator, in particular a comparator with hysteresis, for example a Schmitt trigger, for transforming the intermediate signal sint(t) into a final binary signal sf(t).

In this step, the threshold(s) of the comparator is (are) chosen so as to be able to detect the portions of the intermediate signal sint(t) corresponding to the passage of an irradiation target <NUM> in front of the distance sensors <NUM>. The value of the threshold(s) depends, in particular, on the diameter of the irradiation targets <NUM>. The threshold(s) may for example be adjusted by calibration measurements, preferably in the installation phase of the target transport system <NUM>.

For example, if the intermediate signal sint(t) is above the threshold of the comparator, the value of the final binary signal sf(t) is logic "<NUM>".

In this example, the third step <NUM> further comprises, after the application of the edge detection algorithm, counting the number of irradiation targets <NUM> having passed through the conduit <NUM> based on the final binary signal sf(t). More particularly, counting the number of irradiation targets <NUM> having passed through the conduit <NUM> comprises counting the pulses in the final signal (sf(t)) having a width greater than or equal to a predetermined threshold T. For example, during this step, a filter is applied to the binary final signal sf(t) to determine the number of peaks having a width greater than a predetermined threshold T. The width of the peaks is calculated by detecting the rising and falling edges of the final binary signal sf(t) and determining the time difference between the thus detected rising and falling edges or by applying an integrator circuit to the pulses of the binary signal sf(t).

The predetermined threshold T depends in particular on the length of the irradiation target <NUM>, as well as on the speed of the irradiation target <NUM>. For example, for an irradiation target <NUM> having a length equal to <NUM> and a speed of the irradiation target <NUM> equal to <NUM>/s at the distance sensors <NUM>, it takes roughly <NUM> to pass the sensors <NUM>. Therefore, a threshold T equal to <NUM> may be chosen, to assume the targets will not pass with a speed greater than (<NUM>)/ <NUM> = <NUM>/s. The threshold T is chosen so as to be able to remove particular interferences which may be coupled into the cables of the distance sensors <NUM>.

Advantageously, the irradiation targets <NUM> have specific geometric features, for example diameter variations, which help distinguishing individual irradiation targets <NUM> in the intermediate signal sint(t) through application of an edge detection algorithm with an appropriate threshold T. For example, the irradiation target <NUM> shown in <FIG> has, at its axial ends <NUM>, ends caps <NUM> having a geometry including a variation in diameter. More particularly, the end caps <NUM> comprise, at their axial ends, a section <NUM> of smaller diameter than the rest of the irradiation target <NUM>. This smaller diameter end section <NUM> results in a drop in the intermediate signal sint(t) between two irradiation targets <NUM>, so that the irradiation targets <NUM> can be distinguished through application of an edge detection algorithm. In the example shown in <FIG>, the end caps <NUM> further comprise, next to the small diameter end section <NUM>, a section <NUM> of greater diameter than the rest of the irradiation target <NUM>.

Other examples of pattern recognition algorithms that may be used in step <NUM> are peak detection, template matching or any other adapted pattern recognition algorithm known for example from image processing.

Optionally, the calculator <NUM> applies a deconvolution algorithm to the intermediate signal sint(t) prior to the application of the pattern recognition algorithm, and for example prior to the application of the edge detection algorithm described above. More particularly, the deconvolution algorithm uses the sensor's sensitivity profile s(x) to approximate the original geometric profile of the irradiation targets <NUM>. This allows removing the effect of the sensor's sensitivity profile s(x) and therefore improves the resolution of the approximation of the geometric profile of the target train. Indeed, the intermediate signal sint(t) results from the convolution of two functions: the geometrical profile of the target train g(x) and the sensitivity profile of the sensor s(x), divided by the speed of the passing irradiation target <NUM>.

The sensor's sensitivity profile s(x) may be stored on the data carrier. It is for example determined through testing.

The signal processing involved in steps <NUM>, <NUM>, <NUM> described above is, for example, performed by a computer program product stored on the readable data carrier and executed by the processor <NUM>.

According to an alternative, the signal processing involved in steps <NUM>, <NUM>, <NUM> is done by adapted analog circuits, known to the skilled person. For example, step <NUM> could be carried out using analog circuits comprising flip-flops.

A target transport system <NUM> according to a second embodiment is shown in <FIG>. In the description of this embodiment, the same reference numerals have been used for designating the elements which have already been described with respect to the first embodiment.

The target transport system <NUM> according to the second embodiment differs from the target transport system <NUM> according to the first embodiment only in that the counting system <NUM> comprises three distance sensors <NUM> at a considered axial location along the conduit <NUM>, instead of two.

The three distance sensors <NUM> are regularly spaced along the circumference of the conduit <NUM> with a constant angular spacing. More particularly, in this embodiment, the angle between adjacent distance sensors <NUM> is equal to <NUM>°.

In this embodiment, the sum of the distance signals s<NUM>(t), s<NUM>(t), s<NUM>(t) is related to the diameter profile dtarget(t) of the irradiation targets <NUM> passing through the conduit <NUM> by the following formula: <MAT> where.

The method associated with the target counting system <NUM> according to this third embodiment differs from the method according to the first embodiment described above only in that, in step <NUM>, the intermediate signal sint(t) corresponds to the sum of the three distance signals s<NUM>(t), s<NUM>(t), s<NUM>(t) obtained by the three distance sensors <NUM>.

The target counting system according to a third embodiment (not shown) differs from the target counting system <NUM> according to the first embodiment only in that the number of distance sensors <NUM> at a given axial location along the conduit <NUM> is equal to n, where n is greater than three, the n distance sensors <NUM> being regularly spaced along the circumference of the conduit <NUM> with a constant angular spacing. In this case, the angle between adjacent distance sensors is equal to <MAT>. n is for example smaller than or equal to <NUM>.

In this embodiment, the sum of the distance signals s<NUM>(t), s<NUM>(t),. sn(t) is related to the diameter profile dtarget(t) of the irradiation targets <NUM> passing through the conduit <NUM> by the following formula: <MAT> where.

The method associated with the target counting system according to this third embodiment differs from the method according to the first embodiment described above only in that, in step <NUM>, the intermediate signal sint(t) corresponds to the sum of the n distance signals s<NUM>(t), s<NUM>(t),. , sn(t) obtained by the n distance sensors <NUM>.

The accuracy of the target counting system <NUM> increases as the number of distance sensors <NUM> increases. However, the accuracy obtained with two distance sensors <NUM> as described in the first embodiment is sufficient for most applications.

The counting system according to the invention is advantageous, since it allows counting the number of irradiation targets <NUM> entering or exiting the core of a nuclear reactor in a particular accurate and reliable manner, even at relatively high target speeds, for example greater than <NUM>/s and in the case where the irradiation targets <NUM> are in direct contact within a target train in the conduit <NUM>.

The invention also relates to a radionuclide generation system comprising a target transport system <NUM>;<NUM> as described above, said target transport system <NUM>;<NUM> being configured for inserting the irradiation targets <NUM> into a predetermined location in the core of the nuclear reactor in a predetermined linear order.

The radionuclide generation system more particularly comprises at least one guide tube extending into the core of the nuclear reactor, the target transport system <NUM>,<NUM> being configured for inserting the irradiation targets <NUM> into said guide tube in a predetermined linear order.

According to one embodiment, the nuclear reactor is a heavy water reactor, such as, for example, a CANDU (CANada Deuterium Uranium) type heavy water reactor. In this case, the guide tube is, for example, a guide tube inserted in a port in a reactivity mechanism deck of the heavy water reactor, as is described, for example, in prior application <CIT>.

According to an alternative, the nuclear reactor is a light water reactor, for example a pressurized water reactor. In this case, the guide tube is, for example, an instrumentation finger of the nuclear reactor, as is described, for example, in prior application <CIT>.

Such systems are known to the skilled person and are not described in detail in the present patent application.

The irradiation target <NUM>, which is used in the radionuclide generation system and in the target counting method described above, in particular comprises an envelope encapsulating a core made of non-fissile material and comprising a suitable precursor material for generating radionuclides, which are to be used for medical and/or other purposes.

The envelope has a shape which is rotationally symmetric, and for example a circular cross-section.

The envelope encapsulates the core in a hermetic manner. It is for example made of a material which is not activated neutron flux, for example of a material comprising polyether ether ketone (PEEK). The envelope may preferably comprise a portion made of a metallic material so as to allow for an improved detection, for example using an inductive sensor.

The core in particular comprises the precursor material in powder form.

More preferably, the irradiation targets <NUM> consist of the precursor material, which converts to a desired radionuclide upon activating by exposure to neutron flux present in the reactor core of an operating commercial nuclear reactor. Useful precursor materials are Mo-<NUM>, Yb-<NUM> and Lu-<NUM>, which are converted to Mo-<NUM> and Lu-<NUM>, respectively. It is understood, however, that the invention is not limited to the use of a specific precursor material.

Claim 1:
A target transport system (<NUM>;<NUM>) for a radionuclide generation system, said target transport system (<NUM>;<NUM>) comprising:
- a conduit (<NUM>) for transporting irradiation targets (<NUM>) through the radionuclide generation system;
- a target drive system (<NUM>) configured to drive the irradiation targets (<NUM>) through said conduit (<NUM>);
- a counting system (<NUM>) configured for counting the number of irradiation targets (<NUM>) passing though the conduit (<NUM>);
characterized in that
said counting system (<NUM>) comprises at least two distance sensors (<NUM>), each configured for measuring a radial distance (d<NUM>, d<NUM>) between the distance sensor (<NUM>) and the irradiation target (<NUM>), said distance sensors (<NUM>) being arranged at a same axial position along the conduit (<NUM>) and being regularly spaced along the circumference of the conduit (<NUM>) with a constant angular spacing.