OA20852A - Measuring device for radiological characterisation of a geographical region of interest and associated methods. - Google Patents

Abstract

The invention relates to a measuring device (10) for the radiological characterisation of a geographical area of interest (12), the device (10) comprising : - a pole (14), the pole (14) comprising a lower end (18) intended to be in contact with the geographical area of interest (12), the pole (14) defining at least one internal volume (36), - at least one nuclear measurement unit (38), received in the at least one internal volume (36), and configured to measure at least one nuclear quantity, - a positioning unit (52) configured to measure a position of the pole (14), the positioning unit (52) comprising at least one antenna (54) attached to the pole (14), for receiving a positioning signal, the measured position of the pole (14) being associated with the at least one measured nuclear quantity

Description

Titre : Measuring device for radiological characterisation of a geographical région of interest and associated methods.

Abrégé :

The invention relates to a measuring device (10) for the radiological characterisation of a geographical area of interest (12), the device (10) comprising:

- a pôle (14), the pôle (14) comprising a lower end (18) intended to be in contact with the geographical area of interest (12), the pôle (14) defining at least one internai volume (36), at least one nuclear measurement unit (38), received in the at least one internai volume (36), and configured to measure at least one nuclear quantity, a positioning unit (52) configured to measure a position of the pôle (14), the positioning unit (52) comprising at least one antenna (54) attached to the pôle (14), for receiving a positioning signal, the measured position of the pôle (14) being associated with the at least one measured nuclear quantity.

Fig. 1

O.A.P.I. - B.P. 887, YAOUNDE (Cameroun) - Tel. (237) 222 20 57 00-Site web: http:/www.oapi.int- Email: oapi@oapi.int

MEASURING DEVICE FOR RADIOLOGICAL CHARACTERISATION OF A GEOGRAPHICAL REGION OF INTEREST AND ASSOCIATED METHODS

The présent invention relates primarily to a measuring device for the radiological characterisation of a geographical area of interest.

The measurement is typically a nuclear measurement.

Nuclear measurement is a technique that involves measuring radiation produced by, for example, a radioactive material. The radioactive material contains, for example, one or more natural or artificiel radionuclides.

The nuclear measurement provides information on the nature of the radioactive material, such as the Chemical composition and more specifically the isotopic composition of a given element, and information on its content.

The geographical area of interest is, for example, an open pit mine. Altematively, the geographical area of interest is an industrial site with radioactive substances, such as an industrial site undergoing decommissioning.

In the case of an open pit mine, the radioactive material is uranium ore.

A nuclear measurement by gamma counting, for example, provides information on the mass concentration (or content) of uranium in the ore.

At an industrial site, a nuclear measurement by gamma and/or neutron counting provides information on the level of contamination of civil engineering structures and their surroundings, and also on the nature of the radionuclides present.

In both cases, it is necessary to accurately characterise the radioactive material in order to facilitate its further processing, whether for in-plant processing in the case of uranium ore or for decontamination in the case of an industrial site being decommissioned. These radiometric measurements are usually carried out with a Geiger-Müller counter, which is a relatively heavy and cumbersome instrument that is tedious for the operator to use.

The purpose of the invention is to provide a measuring device that enables reliable, accurate and convenient in situ radiological characterisation of a geographical area of interest.

To this end, the invention reiates to a measuring device ofthe aforementioned type, comprising:

- a pôle extending mainly in a main direction, the pôle comprising a lower end intended to be in contact with the geographical area of interest, the pôle defining at least one internai volume,

- at least one nuclear measurement unit, received in the at least one internai volume, and configured to measure at least one nuclear quantity,

- a positioning unit configured to measure a position of the pôle, the positioning unit comprising at least one antenna attached to the pôle, for receiving a positioning signal, the measured poie position being associated with the at least one measured nuclear quantity.

Thus, thanks to the device according to the invention, the radiological characterisation of the geographical area of interest is reliable and précisé. Each (nuclear) measurement is associated with a position of the device. This information is stored in the memory of the storage unit and can be used to facilitate further processing of the radioactive material from the geographical area of interest. Furthermore, the device according to the invention is easily movable and manipulable by a user in the geographical area of interest.

According to particular embodiments, the device according to the invention comprises one or more of the following features taken in isolation or in any combination that is technically possible:

- the pôle comprises an upper part and a lower part removably connected to the upper part, the lower part comprising the at least one nuclear measurement unit;

- the at least one nuclear measurement unit comprises at least one scintillation detector and/or a neutron measurement probe;

- the device further comprises a radio transmission unit for transmitting to a remote receiving equipment at least the measured position and the measurement of the nuclear quantity and/or a nuclear characteristic related to the measured nuclear quantity;

- the device comprises a storage unit for storing the at least one nuclear quantity and the associated position ofthe pôle;

- the pôle and the storage unit are configured to communicate in a wired or wireiess manner with the nuclear measurement unit and the positioning unit;

- the at least one nuclear measurement unit comprises an upper scintillation detector and a lower scintillation detector, preferably identical, accommodated in the at least one internai volume, separated from each other in the main direction;

- the pôle has a substantially tubular shape, the ratio between a dimension in the main direction and a dimension in a direction substantially perpendicular to the main direction being between 20 and 80.

- the device comprises at least one battery connected to the at least one nuclear measurement unit and to the positioning unit for powering said units.

The invention further relates in a second aspect to a method of nuclear characterisation of a geographical area of interest using a device as described above, the method comprising:

- bringing the lower end of the pôle into contact with the geographical area of interest,

- measuring a pôle position using the positioning unit,

- measuring at least one nuclear quantity using the at least one nuclear measurement unit,

- associating the measured pôle position with the at least one measured nuclear quantity.

According to a particular embodiment, the method comprises a step of characterising the heterogeneity of a part of the geographical area of interest by comparing, for the same position of the device, a first nuclear quantity measured by the upper scintillation detector and a second quantity measured by the lower scintillation detector.

According to another embodiment, the step of characterising heterogeneity comprises calculating a ratio of the first nuclear quantity to the second nuclear quantity for a predetermined time.

Finally, according to a third aspect, the invention relates to a method for sorting ore from an open pif mine, the ore occupying a predetermined volume, the method comprising the following steps:

- partitioning the volume into a plurality of sub-elements, for each sub-element:

- at least one nuclear characterisation according to the method described above, the geographical area of interest being the sub-element,

- determining at leastone nuclearcharacteristicofthe sub-element using the at least one nuclear quantity measured by the at least one nuclear measurement unit,

- extracting at least part ofthe sub-element,

- storing the at least one extracted part according to the nuclear characteristic.

In particular embodiments, the method comprises one or more of the following features:

- the method comprises for each sub-element, before the step of determining the nuclear characteristic, a step of comparing the at least one measured nuclear quantity with at least one reference nuclear quantity,

- the method comprises determining a position of the sub-element using the pôle position measurement and a step of creating a three-dimensional model of the nuclear characteristic of the volume using the nuclear characteristic and the position of at least some of the sub-elements,

- the steps of nuclear characterisation and of determining the at least one nuclear characteristic are performed for a plurality of sub-elements in a first operational phase, and the steps of extraction and storage are performed in a second operational phase subséquent to the first operational phase.

The invention will be better understood upon reading the following description, given only as an example, and with reference to the drawings, in which:

- [Fig 11 Figure 1 is a schematic depiction of a device according to the invention, and

- [Fig 2] Figure 2 is a schematic depiction of a method for sorting ore from an open pit mine according to the invention.

A measuring device 10 and more particularly a nuclear measuring device for the radiological characterisation of a geographîcal area of interest 12, according to the invention is shown in figure 1.

Nuclear measurement is a technique that consists of measuring the radiation, for example gamma or neutron radiation, emitted by a radioactive material.

The radioactive material contains, for example, one or more naturel or artificial radionuclides.

Examples of naturally occurrlng radionuclides include Thorium 232, Potassium 40, and Uranium 238.

Artificial radionuclides include, for example, Césium 137 and Cobalt 60.

The geographîcal area of interest 12 is for example an open pit mine, for example a uranium open pit mine,

Alternatively, the geographîcal area of interest 12 is an industrial site to be decommissioned, for example former basic nuclear installations (BNI).

The device 10 according to the invention comprises a pôle 14 extending mainly in a main direction P. In the remainder of the description, this main direction corresponds to the vertical direction when the pôle 14 is used under normal conditions.

The pôle 14 thus comprises an upper end 16 and a lower end 18 opposite the upper end 16, intended to be in contact with the ground 20 of the geographîcal area of interest 12 to be inspected (Figure 2).

The pôle 14 typically has a dimension in the main direction P of between 1 m and 2 m, for example 2 m between the lower end 18 and the upper end 16.

The pôle 14 is preferably tubular in shape. The diameter of the pôle 14 is for example between 30 mm and 60 mm, for example 40 mm.

The ratio between the dimension along the main direction P and a dimension substantially perpendicular to the main direction P is for example between 20 and 80.

For example, the pôle 14 is made of aluminium. Altematively, at least part of the pôle 14 is made of carbon, for example carbon fibre.

Altematively, at least part of the pôle 14 is made of composite material.

This makes it easier to grip the pôle 14. The pôle 14 can be held by the user 22 with one hand.

The pôle 14 comprises a grip area 24 for gripping by a user 22. The grip area 24 advantageously extends between 20 cm and 1.20 m from the upper end 16 of the pôle 14. This makes it easier for the user 22 to grasp the nuclear measuring device 10 regardless of the height of the user 22. Thus, a standing user 22 can easily hold the measuring device 10 in the vertical direction.

Preferably, the pôle 14 comprises a gripping member 26 attached to an outer wall 28 of the pôle 14. This further facilitâtes the grasping of the measuring device 10 and its movement over the geographical area of interest 12. Advantageously, the gripping member 26 can be moved along the wall of the body of the pôle 14 so that the user can position it in an idéal manner given their height.

Preferably, the poie 14 comprises means for measuring the inclination 30 ofthe poie relativetothevertical,toensuretheverticalityofthe pôle 14when it is placed on the ground 20 of the geographical area of interest 12. For example, the means of measuring the inclination 30 is a spirît level.

Advantageously, alternativeiy or additionally, the device 10 comprises a levellîng unit (not shown) configured to enable/disable the acquisition of a measurement with the device 10 according to the value of the inclination of the device 10 with respect to the vertical.

To facilitate its transport, the pôle 14 is preferably made of two tubular parts, namely an upper part 32 and a lower part 34 detachably connected to the upper part 32. For example, the lower part 34 and the upper part 32 are screwed together.

The upper and lower parts 32, 34 hâve, for example, an approximately equal dimension in the main direction P.

Preferably, the upper part 32 comprises the grip area 24 and/or the gripping member 26.

The lower part 34 defines at least one internai volume 36.

The device 10 comprises at least one nuclear measurement unit 38 configured to measure at least one nuclear quantity.

The nuclear measurement unit 38 comprises, for example, at least one scintillation detector 42.

The measuring unit 38 is advantageously accommodated in the at least one internai volume 36. This is particularly advantageous as the unit 38 is protected by the outer wall ofthe lower part 34 ofthe pôle 14. In addition, the nuclear measurement unit 38 does not form any external protrusions on the pôle 14, which further improves the robustness of the nuclear measuring device 10.

Furthermore, in the case where the lower and upper parts 34, 32 are detachably connected, the device 10 is modular as different lower parts 34 with different nuclear measurement units 38 can be attached to the upper part 32 of the pôle 14 depending on the type of nuclear characterisation desired.

The at least one nuclear measurement unit 38 is for example a gamma measurement unit. The at least one measurement unit 38 comprises at least one scintillation detector 42. The at least one scintillation detector 42 is for example a sodium iodide (Nal) detector. Alternatively, the at least one scintillation detector 42 is a lanthanum bromide (LaBrs) detector optionally doped with césium or césium iodide (Csl).

The nuclear quantîty measured by the measurement unit 38 is thus for example a gamma count expressed in counts per second, or an absorbed dose rate expressed in nGy/h or Sv/h or in its multiples and sub-multiples.

Alternatively, the nuclear quantîty is for example a uranium grade. For example, the uranium grade is determined from the gamma count using the formula T = K χ C, where T is the uranium grade, for example, expressed in ppm, K is a calibration factor and C is the gamma count in counts per second.

Alternatively, the at least one nuclear measurement unit 38 is a measurement unit adapted to measure neutron radiation, alpha radiation or beta radiation.

The sampling frequency of the nuclear quantîty is preferably between 0.25 Hz and 5 HZ, for example 1 Hz.

The at least one scintillation detector 42 comprises a crystal 44 having a volume of between 10 mL and 50 mL, for example 25 mL. The crystal 44 can be of any shape, for example cubic, paralleiepipedal or circular cylindrical.

Advantageously, as visible in Figure 1, the nuclear measurement unit 38 comprises two scintillation detectors 42: a lower scintillation detector 46 and an upper scintillation detector 48 spaced apart from each other along the main direction P of the pôle 14.

The upper detector 46 and the lower detector 48 are advantageously identical.

The lower detector 48 is preferably arranged at a distance of between 5 cm and 15 cm, for example 10 cm, from the lower end 18.

The upper detector 48 is preferably located between 0.8 m and 1.2 m from the lower end 18 of the pôle 14, for example 1.0 m.

This is particularly advantageous, as each of the detectors 46, 48 has a different détection field 46A, 48A.

“Détection field means the volume of space in the geographicai area of interest 12 contributing to measurement by the detector 46,48.

The détection field 48A of the upper detector 48 is larger than the détection field 46A of the lower detector 46.

Preferably, the device 10 further comprises a shielding system arranged around the upper detector 48. The shielding system is for example formed by a lead cylinder. The shielding system allows the solid angle of the détection field 48A of the upper detector 48 to be constrained.

The lower part 34 ofthe pôle 14 preferably comprises a shock-absorbing end cap 50 attached to the lower end 18.

The end cap 50 is, for example, a processor. The end cap 50 also has an anti-slip function.

The nuclear measuring device 10 comprises a posîtioning unit 52 configured to measure a position of the device 10. The posîtioning unit 52 is connected to the at least one nuclear measurement unit 38.

The posîtioning unit 52 comprises at least one antenna 54 attached to the pôle 14, in particular to the upper part 32 of the pôle 14.

For example, the antenna 54 is attached to the upper end 16 of the pôle 14 as shown in Figure 1.

The posîtioning unit 52 is for example a Global Navigation Satellite System (GNSS) unit, preferably by differential posîtioning.

In this mode of operation, the posîtioning unit 52 uses at least one fixed reference station which transmits the déviation between the positions indicated by the satellites and their actual known positions. The posîtioning unit 52 receives the différence between the pseudo-distances measured by the satellites and the true pseudo-distances and thus corrects its position measurements.

The accuracy ofthe position measurement is advantageously 10 cm in the horizontal plane and 15 cm in the vertical plane.

The use of differential posîtioning makes it possible to achieve such accuracy even for acquisition times of the nuclear measuring device 10 of the order of a second.

The nuclear measuring device 10 further comprises at least one battery 56 connected to the at least one nuclear measurement unit 38 and to the posîtioning unit 52 for supplying power to said units 38, 52.

Preferably, the device 10 comprises at least one battery 56 arranged in the at least one internai volume 36 of the upper part 32 of the pôle 14 for powering the at least one nuclear measurement unit 38, and for powering the posîtioning unit 52.

Alternatively, the positioning unit 52 comprises an antenna for its power supply.

Preferably, the at least one battery 56 is removable. The battery 56 is then recharged using a charger connected to the electrical network.

Alternatively, the device 10 comprises a charging module (not shown) for recharging the at least one battery 56 by connecting the pôle 14 to the mains and leaving the at least one battery 56 in the internai volume 36.

The nuclear measuring device 10 further comprises a storage unit 58 comprising a memory configured to store the at least one nuclear quantity and the associated position ofthe device 10 provided by the positioning unit 52.

As shown in Figure 1, the storage unit 58, which is not an intégral part of the pôle, is configured to communicate with the positioning unit 52 and the at least one nuclear measurement unit 38 via a wireless link. The wireless link is for example a Bluethooth® link, a link using NFC (Near Field Communication), LoRa™, or Wi-Fi technology.

Alternatively, the storage unit 58 is for example connected to the positioning unit 52 and the at least one nuclear measurement unit 38 by a wired connection. The pôle 14 may thus comprise connectivity, for example using the USB standard, to allow the connection of a cable for data transfer with the storage unit 58 or to receive a removable storage medium.

Advantageously, the nuclear measuring device 10 comprises a human-machine interface 60 connected to the storage unit 58. The interface 60 is, for example, a touchsensitive display device allowing the measurement of the nuclear quantity to be triggered, the nuclear quantifies and associated positions stored in the memory to be displayed, etc.

Preferably, the human-machine interface 60 is equipped with a dedicated application allowing the display of a previously loaded map and thus locating the user in real time in the geographical area of interest 12 under operation.

Even more preferably, the human-machine interface 60 comprises a device for connecting the interface 60 to a computer (not shown). The connection is for example wired or wireless.

Advantageously, the nuclear measuring device 10 (i.e. the pôle 14 or the storage unit 58) comprises a radio transmission unit 62 for transmitting at least the position measured by the positioning unit 52 and the measurement of the nuclear quantity measured by the at least one nuclear measurement unit 38 and/or a nuclear characteristic related to the measurement ofthe nuclear quantity to a remote receiving equipment 64. In the example shown in Figure 1, the radio transmission unit 62 is arranged at the upper end 16 of the pôle 14. In another embodîment, the radio transmission unit 62 is arranged on the outer wall of the pôle 14.

The association between the measurement of the position of the pôle 14 and the measurement of the nuclear quantity (or the nuclear characteristic) is for example carried out at the positioning unit 52, or at the nuclear measurement unit 38, or at the radio transmission unit 62 or at the human-machine interface 60,

The nuclear characteristic is, for example, a class related to an ore grade classification. For example, the classification has three predefined classes: These include high-grade, low-grade and medium-grade. Each of the classes corresponds, for example, to a range of content: between 0 and 2%a for the ''low-grade class, between 2%o and 4%o for the medium-grade class, and at a content above 4 %o for the high-grade class.

Of course, the number of classes in the classification is variable. The classification comprises for example between 2 and 10 classes.

These classifications are used, for example, to sort the ore for the processing plant. The ore treatment process is typically tailored to the average uranium grade of the ore and it is therefore important to correctiy classify the ore from the open pit as discussed below.

A method for nuclear characterisation of a geographical area of interest 12 using a nuclear measuring device 10 as mentioned above will now be described.

The method firstly includes a step of bringing the lower part 34 of the pôle 14 in contact with the ground 20 of the geographical area of interest 12.

For example, the pôle 14 is held by the user 22 substantially in the vertical direction by means of the spirit level 30.

Alternatively (not shown), the pôle is held by the user 22 substantially in the horizontal direction substantially perpendicular to the vertical direction for example to make measurements on a vertical barrier, such as a wall.

The method then comprises measuring a position of the device 10 using the positioning unit 52 and measuring at least one nuclear quantity using the at least one nuclear measurement unit 38.

These two measurements may take place either one before the other or substantially concurrently.

Preferably, the method further comprises storing in the storage unit 58 the measured position and the at least one nuclear quantity and/or a nuclear characteristic related to the measurement of the nuclear quantity.

Advantageously, the method comprises a step of characterising the heterogeneity of a région of the geographical area of interest 12 by comparing, for the same position of the device 10, a first nuclear quantity measured by the upper detector 48 and a second quantity measured by the lower detector 46.

Indeed, as mentioned above, the détection field 48A, 46A of the upper detector 48 and lower detector 46 is different. The détection field 48A of the upper detector 48 is larger than the détection field 46A of the lower detector 46.

Also, in the case where the nuclear quantity is the uranium grade and the upper scintillation detector 48 and the lower scintillation detector 46 are similar, if the first nuclear quantity is substantially similar to the second nuclear quantity, it means that the région of the geographical area of interest 12 around the measuring device 10 is relatively homogeneous in terms of the radioactive élément content. The région of the geographical area of interest 12 corresponds substantially to a ground dise centred on the upper detector 48 and corresponding to the base of the conical détection field 48A of the upper detector 48,

Conversely, if the first nuclear quantity and the second nuclear quantity are different, this means that the région of the geographical area of interest 12 around the measuring device 10 is heterogeneous.

In the case where the nuclear quantity is the gamma count, the upper scintillation detector 48 and the lower scintillation detector 46 are similar, and the geographical area of interest 12 around the measuring device 10 is relatively homogeneous in terms of radioactive element content, the ratio of the first nuclear quantity to the second nuclear quantity is related to the ratio of the distance to the ground of the upper detector 48 to the distance to the ground of the lower detector 46 by the relationship: C1/C2 = a * h1/h2, where C1 is the gamma count measured by the upper detector 48, C2 is the gamma count measured by the lower detector 46, a is a constant, h1 and h2 are the heights above ground of the upper detector 48 and the lower detector 46 respectively.

Thus, preferably, the step of characterising the heterogeneity of a région of the geographical area comprises calculating the ratio of the first nuclear quantity to the second nuclear quantity and a variation in the value of the ratio over time.

For example, the first nuclear quantity and the second nuclear quantity are measured, for the same position of the pôle, for a predetermined time.

The predetermined time is for example between 30 seconds and 10 minutes, preferably between 1 minute and 5 minutes.

Thus, when the calculated ratio is substantially constant over time, i.e. the variation in the value of the ratio over time is less than a predetermined threshold, this means that the région of the geographical area of interest 12 around the measuring device 10 is homogeneous.

A method of sorting uranium ore from an open pît mine using a nuclear measuring device 10 as mentioned above will now be described.

Typically, before an open pit mine is developed, a model ofthe volume of mineable ore is created from radiometric measurements in first boreholes (not shown).

Radiometric measurements in the first boreholes provide information on the average uranium grade as a function of depth. This is done, for example, by moving a scintillation detector into the borehole.

The first boreholes are for example between 0 and 100 m deep, typically 60 m. The first boreholes are préférably spaced at a distance of between 10 m and 100 m, for example 25 m.

After rénovai of the barren topsoil, further radiometric measurements are usually made in second boreholes called shot holes. The distance between the second boreholes is smaller than the distance between the first boreholes. For example, the distance between the second boreholes is 5 m.

The ground in the geographical area of interest 12 is then undermined using explosives in successive panels 66. The panels 66 are, for example, 50m by 50m and 6 m thick (Figure 2).

The volume occupied by the ore in a panel 66 is then partitioned into a plurality of sub-elements 68. For example, sub-elements 68 hâve a dimension of 5 m by 5 m by 0.5 m. The sorting is done on the scale of each sub-element 68.

To do this, the user 22 performs at least one nuclear characterisation using the method described above. In this way, they obtain at least one nuclear quantity relating to the sub-element 68 and at least one position of the device 10.

For example, the user 22 takes a position substantially in the centre of the subelement 68 to perform the nuclear characterisation. For example, they use the nuclear quantity measured by the upper detector 48 of the device 10.

Altematively, the user 22 visually observes that the floor of the sub-element 68 is heterogeneous, for example from the colour ofthe ore. In this case, the user 22 more locally performs at least one measurement of a nuclear quantity using the lower detector 46 which has a more limited détection field 46A compared to the upper detector 48. The lower detector 46 is thus more suitable for characterising a heterogeneous area of more limited size, smaller than the size of a sub-element 68.

Advantageously, the user 22 compares the at least one nuclear quantity measured for the sub-element 68 with a reference nuclear quantity.

The reference nuclear quantity is, for example, the quantity obtained by the modelling carried out with the radiometric measurements made in the first and/or second boreholes.

The comparison is facilitated because the position measurement ofthe device 10 aliows the user 22 to know exactly where they are in the geographical area of interest 12.

The user 22 then détermines at least one nuclear characteristic of the sub-element 68 using the at least one nuclear quantity.

As mentioned above, the nuclear characteristic is for example a class relating to the uranium content of the ore: The term low-grade, medium-grade, high-grade.

The position of the device 10, the at least one nuclear quantity, and/or the at least one nuclear characteristic are advantageously sent to at least one remote receiving equipment 64 using the radio transmission unit 62 of the device 10.

For example, the at least one remote receiving equipment 64 is an excavator and/or a dump truck.

The remote receiving equipment 64 moves to the sub-element 68 or part of the subelement 68.

The method then comprises extracting at least part of the sub-element 68.

If the sub-element 68 ts relatively homogeneous, the entire volume of the subelement 68 is extracted.

The extracted part is then stored according to the nuclear characteristic.

For example, the extracted part is stored in the dump truck according to the nuclear characteristic. The method is repeated for each of the sub-elements 68.

Thus, a single dump truck comprises ore with the same nuclear characteristic from a pîurality of sub-elements 68.

The ore is thus optimally sorted for processing in the plant, owing to the nuclear measuring device 10. The method is particularly advantageous because the extraction and nuclear characterisation of the sub-elements 68 can be performed independently of each other. The remote receiving equipment 64 receives the information relating to the position of the device 10, the nuclear quantity and/or the nuclear characteristic, and can thus act autonomously with respect to the user 22, who can continue the nuclear characterisation of the other sub-elements 68 on their own.

In an embodiment not shown, the positioning unit 52 and the nuclear measurement unit 38 are connected to an intermediate connection module. The intermediate connection module aliows, for example, the measurement of the position of the pôle 14 to be associated with the measurement of the nuclear quantity measured by the nuclear measurement unit 38 (or the nuclear characteristic). The intermediate connection module is advantageously connected to the radio transmission unit 62.

In a particular embodiment, the position of the sub-elements 68 is determined using the measurement of the position of the pôle 14.

Thus, a three-dimensional position and a nuclear characteristic are associated with each of the sub-elements 68.

It is then possible to create a three-dimensional model of the nuclear characteristic of the volume from this data.

The three-dimensional model is constructed, for example, as the nuclear characterisation of each of the sub-elements 68 is carried out or after the nuclear characterisation of a plurality of sub-elements 68 has been carried out.

The three-dimensional model is preferably produced by measuring the position of the pôle 14 using differential positioning. The method uses the antenna 54 carried by the pôle 14 to determine the position in the vertical direction with an uncertainty on the order of ten centimètres and a fixed positioning station on the terrain to be surveyed which can integrate over a period of time its position xO, yO, and zO, which serve as reference coordinates. The positioning unit 52 is configured to calcuiate the position of the pôle 14 relative to the fixed positioning station and, by différence, to determine the x,y,z coordinates of the pôle 14 with low uncertainty even for acquisition times on the order of a second.

Advantageously, the steps of nuclear characterisation and détermination of the nuclear characteristic are performed for a plurality of sub-elements in a first operational phase.

The first operational phase is carried out, for example, by one or more operators.

The extraction and storage steps are, for example, carried out in a second operational phase after the first operational phase, using the information acquired in the first operational phase.

Claims (14)

1, A measuring device (10) for the radiological characterisation of a geographical area of interest (12), the device (10) comprising:

- a pôle (14) extending mainly in a main direction (P), the pôle (14) comprising a lower end (18) intended to be in contact with the geographical area of interest (12), the pôle (14) defining at least one internai volume (36),

- at least one nuclear measurement unit (38), received in the at least one internai volume (36), and configured to measure at least one nuclear quantity,

- a positioning unit (52) configured to measure a position ofthe pôle (14), the position ing unit (52) comprising at least one antenna (54) attached to the pôle (14), for receiving a positioning signal, the measured position ofthe pôle (14) being associated with the at least one measured nuclear quantity, the pôle (14) comprising an upper part (32) and a lower part (34) removably connected to the upper part (32), the lower part (34) comprising the at least one nuclear measurement unit (38).

2. The device (10) according to claim 1, wherein the at least one nuclear measurement unit (38) comprises at least one scintillation detector (42) and/or a neutron measurement probe.

3. The device (10) according to eîther one of claims 1 to 2, further comprising a radio transmission unit (62) for transmîtting to a remote receiving equipment (64) at least the measured positron and the measurement of the nuclear quantity and/or a nuclear characteristic related to the measured nuclear quantity.

4. The device according to any one of claims 1 to 3, comprising a storage unit (58) for storing the at least one nuclear quantity and the associated position of the pôle (14).

5. The device according to claim 4, wherein the pôle (14) and the storage unit (58) are configured to communicate in a wired or wireless manner with the nuclear measurement unit (38) and the positioning unit (52).

6. The device (10) according to any one of claims 1 to 5, wherein the at least one nuclear measurement unit (38) comprises an upper scintillation detector (48) and a lower scintillation detector (46), preferably identical, received in the at least one internai volume (36), separated from each other in the main direction (P).

7. The device (10) according to any one of claims 1 to 6, wherein the pôle (14) has a substantiaily tubular shape, the ratio between a dimension along the main direction (P) and a dimension along a direction substantiaily perpendicular to the main direction (P) being between 20 and 80.

8. A method of radiological characterisation of a geographical area of interest (12) using a device (10) according to any of claims 1 to 7, the method comprising:

- bringing the lower end (18) ofthe pôle (14) into contact with the geographical area of interest (12),

- measuring a position ofthe pôle (14) using the positioning unit (52),

- measuring at least one nuclear quantity using the at least one nuclear measurement unît (38),

- associating the measured position of the pôle (14) with the at least one measured nuclear quantity.

9. The method of characterisation according to claim 8 with the device (10) according to daims 7 or 8, the method comprising a step of characterising the heterogeneity of a part of the geographical area of interest (12) by comparing, for the same position ofthe device (10), a first nuclear quantity measured by the upper scintillation detector (48) and a second quantity measured by the lower scintillation detector (46).

10. The characterisation method according to claim 9, wherein the step of characterising heterogeneity comprises calculating a ratio ofthe first nuclear quantity to the second nuclear quantity for a predetermined time.

11. A method of sorting uranium ore from an open pit mine, the ore occupying a predetermined volume, the method comprising the following steps:

- partitioning the volume into a plurality of sub-elements (68), for each sub-element (68):

- at least one nuclear characterisation according to the method of any one of daims 8 to 10, the geographical area of interest being the sub-element (68),

- determining at least one nuclear characteristic of the sub-element (68) using the at least one nuclear quantity measured by the at least one nuclear measurement unit (38),

- extracting at least part of the sub-element (68),

- storing the at least one extracted part according to the nuclear characteristic.

12. The method according to claim 11, comprising for each sub-element (68), before the step of determining the nuclear characteristic, a step of comparing the at least one measured nuclear quantity with at least one reference nuclear quantity.

13. The method according to claim 11 or 12, comprising determining a position ofthe subelement (68) using the pôle (14) position measurement and a step of creating a threedimensional model ofthe nuclearcharacteristic ofthe volume using the nuclear characteristic and the position of at least some of the sub-elements (68).

14. The method according to any one of daims 11 to 13, the steps of nuclear characterisation and of determining the one nuclear characteristic are performed for a plurality of sub-elements (68) in a first operational phase, and the steps of extraction and storage are performed in a second operational phase subséquent to the first operational phase.