Ionizing radiation detector

Abstract

The invention relates to an ionizing radiation detector, the detector comprising:- a monomer in a crystalline form,- and a catalyst incorporated within the crystalline form of the monomer, the catalyst catalyzing the polymerization of the monomer following absorption of ionizing radiation, the polymer resulting from the polymerization of the monomer having a different color from the monomer. Figure for abstract: Figure 1

Description

Title of the invention: Ionizing radiation detector Technical field

[0001] The invention relates to a method for detecting and a detector of ionizing radiation as well as a method for manufacturing such a detector. STATE OF THE ART

[0002] As part of any industrial activity carried out under ionizing radiation, particularly in nuclear power plants in operation or being dismantled, checks and maintenance of the various equipment are scheduled. The main risks for workers carrying out said operations are contamination and irradiation. Irradiation corresponds to the case where the worker is exposed from the outside to radiation emitted by emitting particles far from said worker. Contamination corresponds to the case where the worker has come into direct contact with the particles emitting ionizing radiation: either by inhalation or ingestion (this is internal contamination), or by direct contact with the skin (this is external contamination). If irradiation stops when the worker is no longer exposed to the radiation source, this is not the case for contamination.A source of irradiation and contamination of workers is, for example, radioactive material which is disseminated in the air and on the surfaces (floor, pipes, etc.) of the premises where the said workers are working during a leak in the circuits and which contaminates the said premises.

[0003] It is necessary, in each room, to measure the surface activity of radioactive particles possibly disseminated in the air and on surfaces in order to define the types of collective protection (containment airlocks, etc.) and individual protection (ventilated waterproof suit, etc.) necessary to limit the exposure of operators to ionizing radiation emitted by radioactive particles, or radionuclides, and to prevent them from contaminating themselves, whether by internal contamination or external contamination. The activity of a radionuclide is the number of entities of said radionuclide which disintegrate per second, expressed in becquerels (Bq). The surface activity is the activity of the radionuclides present on a surface divided by the Faire value of said surface and is expressed in becquerels per square centimeter (Bq / cm2).

[0004] The measurement of surface activity, in particular for alpha radiation emitters (particle consisting of two protons and two neutrons) and for beta radiation emitters (electrons or positrons), proves to be complicated to implement for reasons linked to the nature of the particles emitted and the physics of their interaction with matter. Thus, alpha particles, due to their mass and high charge, interact with matter through Coulomb interaction by ionizing and exciting atoms and molecules. They are very weakly penetrating but highly ionizing and the most dangerous if ingested or inhaled. Beta particles also interact with matter through Coulomb interaction by ionizing atoms and molecules. These particles are more penetrating but less ionizing than alpha particles.

[0005] The means commonly used in nuclear power plants for detecting radioactive particles contaminating a room are devices called contaminameters. Contamination meters measure a surface activity value (in Bq / cm2) or a count (cps, counts per second), but they do not allow direct visualization of the contamination.

[0006] To use a contaminameter, several actions are possible. Direct measurement consists of taking the measurement directly on the surface that is suspected of being contaminated by particles emitting ionizing radiation while keeping the contaminameter as close as possible to said surface (between a few millimeters and 5 cm depending on the nature of the contamination). In the case where the surface to be tested is large, it is also possible to scan said surface with the contaminameter, for example at a speed close to 5 cm / s. Indirect measurement consists of taking a smear sample on the surface that is suspected of being contaminated, transferring said smear to a room with low gamma background noise and then taking the measurement on the smear while keeping the closest possible distance between the contaminameter and the smear or using a smear changer (for example of the NT200 type).Indirect measurement is necessary in some cases, especially if the gamma background noise is high enough to disturb direct measurements (for a gamma background noise greater than about 1 pSv / h, said gamma background noise can be caused for example by the elements 60Co, 58Co, 110Ag and by a lot of radiation scattered by surfaces, pipes, etc.).

[0007] Such direct or indirect measurements with a contaminameter have several drawbacks. During a direct measurement or screening, as previously mentioned, it is particularly necessary to bring the probe used as close as possible to the surface to be measured. Indeed, a very short distance (a few centimeters to tens of centimeters) in the air is sufficient to stop alpha and beta particles. The detection efficiency therefore decreases rapidly with the distance between the probe and the surface to be measured. Such near-contact measurements require the operator to remain close to the potentially contaminated area, thus exposing him to an increased risk of internal and / or external contamination. In addition, Screening, due to a limited scanning speed, can be time-consuming, especially if the surface to be checked is large or has a complex and / or non-flat geometry, which leads to prolonged exposure of the workers carrying out the measurements to the potentially contaminated environment and therefore increases the risk of contamination of said workers. Indirect measurement, for its part, leads to additional working time in a potentially contaminated irradiating area as well as additional dressing / undressing steps and, therefore, an increased risk of dissemination of contamination and / or contamination of the operator. Finally, measurements by contaminameter, whether direct or indirect, give the value of the surface activity at the time of measurement or sampling. They are not visual and to know the temporal evolution of the contamination, it is necessary to repeat the measurement several times, with the associated risks..

[0008] Other solutions are proposed to be able to visualize the contamination in a room. For example, the "alpha-camera" can be used to detect alpha particles. The detection of said alpha particles is carried out indirectly by measuring the radioluminescence emitted by the nitrogen molecules in the air following the ionization of said molecules by the alpha radiation to be detected. Thus, the emission frequencies of the radioluminescence used by the alpha-camera are in the ultraviolet range, between 200 nm and 400 nm, so that an optical sensor and processing of the captured data are necessary. Access to the contamination information is therefore not directly visible to the naked eye. In addition, a power supply is necessary for the operation of the alpha-camera.Finally, the use of the alpha camera is restrictive for the user since, to avoid light pollution, measurements must be carried out in the dark (cover around the target). Thus, the applications of the alpha camera are mainly aimed at controlling contamination in glove boxes and controlling the decontamination of objects (measurements before and after decontamination).

[0009] Another solution consists of using radiochromic films comprising a monomer from the diacetylene family trapped in a self-supporting neutral polymer matrix. When said film is exposed directly to ionizing radiation (X-rays, gamma, beta or alpha), the diacetylene monomer polymerizes. Optical density analysis of the film makes it possible to highlight the blackening of the radiochromic film due to the transition from the uncolored or slightly colored monomer state (pale yellow, pale blue or white) to the colored polymer state. In the medical field, the blackening of radiochromic films is used, for example, to check the collimation of beams for radiotherapy. The sensitivity of such radiochromic films depends on the nature of the ionizing radiation. For the detection of alpha particles, the change in color of said films is visible to the naked eye only for activities of the order of a few Mega Becquerels (MBq). For example, the color change of an EBT3 film from Gafchromic is observed following exposure of said EBT3 film to a 241Am source of 3.7 MBq. Such films are therefore not efficient enough to detect leaks of radioactive material on construction sites carried out on industrial installations where there is a risk of exposure to ionizing radiation, for example on construction sites carried out on the site of a nuclear power plant in operation or being decommissioned. Indeed, the activity to be detected on these sites is generally between ten Becquerels and a few kilos of Becquerels. For such low activities, the color change of said radiochromic films is not visible to the naked eye and it is actually necessary to use a scanner to be able to detect the color change of the film. The detector's response is therefore neither visual nor immediate. BRIEF DESCRIPTION OF THE INVENTION

[0010] An aim of the invention is to design a detector of ionizing radiation, in particular alpha radiation, which allows detection with the naked eye of activities between about ten Becquerels and a few kilo Becquerels (kBq) without it being necessary to resort to an additional reading device.

[0011] The detector must in particular be able to visually alert an operator to the presence of radioactive material contaminating a worksite carried out on a nuclear power plant site in operation or being dismantled, for example due to a leak in the circuits, or contaminating the operator himself (contamination on the skin or clothing), the activity of the contamination being between about ten Becquerels and a few kilos Becquerels. The detector must also quickly inform him of the presence of said contamination. Thus, the operator is not obliged to approach the area suspected of contamination to carry out the measurement and he is not exposed to said contamination for a prolonged period without being warned.

[0012] The detector must finally be able to operate autonomously for the entire duration of the worksite until the appearance of contamination or irradiation due to the presence of radioactive particles emitting ionizing radiation on the worksite or on the skin or clothing of the workers on said worksite.

[0013] For this purpose, the invention proposes an ionizing radiation detector, the detector comprising:

[0014] - a monomer in a crystalline form, and

[0015] - a catalyst incorporated within the crystalline form of the monomer, the catalyst catalyzing the polymerization of the monomer following absorption of ionizing radiation,

[0016] the polymer resulting from the polymerization of the monomer having a color different from the monomer.

[0017] According to other optional characteristics of the ionizing radiation detector taken alone or in combination when technically possible: - the polymerization of the monomer is further activated following absorption of ionizing radiation by the monomer; - the monomer is in the form of a crystalline powder; - the monomer is included in a layer, in particular an arranged layer on a support; - the layer has a thickness of between 10 pm and 2 mm, preferably a thickness of between 50 pm and 100 pm; - the layer does not include a polymer binder and / or additives; - the layer consists only of the crystalline powder of the monomer compacted or wherein the layer consists of a mixture of compacted powders comprising the crystalline powder of the monomer; - the monomer is a diacetylenic monomer of the following formula (I):

[0018] R'-C=CC=C-R2 (I)

[0019] wherein R1 and R2 are independently selected from an optionally substituted C1-C18 hydrocarbon chain, an optionally substituted aryl group and an optionally substituted heteroaryl group, wherein one or more, preferably 1 to 4 methylene groups of said hydrocarbon chain are optionally replaced by O, C(O), NH or N-(C1-C6alkyl); - the catalyst is chosen from quinones and benzoquinones.

[0020] The invention also relates to a method for detecting ionizing radiation comprising the following steps:

[0021] E0) Provision of a detector as previously described, El) Polymerization of the monomer, the polymerization being catalyzed by the catalyst, following absorption by the catalyst of ionizing radiation, the resulting polymer having a color different from the monomer, E2) Observation with the naked eye of the color change.

[0022] Finally, the invention relates to a method for manufacturing an ionizing radiation detector comprising the incorporation of a catalyst within the crystalline form of a monomer, the catalyst catalyzing the polymerization of the monomer following absorption of ionizing radiation and the resulting polymer having a color different from the monomer. In this method, the catalyst is in particular incorporated within the crystalline form of the monomer by a recrystallization process. BRIEF DESCRIPTION OF THE FIGURES

[0023] Other characteristics and advantages of the invention will emerge from the detailed description which follows, with reference to the appended drawings, in which:

[0024] - [Fig.l] represents a detector of ionizing radiation emitted by a contamination according to an embodiment of the invention in which the crystalline form of the monomer in which the catalyst is incorporated is included in a layer arranged on a support, the layer forming the active layer of the detector.

[0025] - [Fig.2A] represents a reference detector, said detector consisting of a crystalline powder of pure (without catalyst) hexane-6-diacetylene-l-diurethane butyl monomer, said crystalline powder being light blue in color;

[0026] - [Fig.2B] represents the detector of [Fig.2A] after 64 hours of exposure to an alpha source with a flux ranging from 70 to 150 alpha / s (source characteristics: 241Am of 3.5 MBq of diameter 80 mm with a flux of 1700 a / s / 2pi sr), said crystalline powder then having a dark blue color;

[0027] - [Fig.2C] represents the detector of figures 2A and 2B after 350 hours exposure to said alpha source, the crystalline powder then having a navy blue color;

[0028] - [Fig.2D] represents a detector according to an embodiment of the invention, said detector consisting of a crystalline powder of the monomer of Figures 2A to 2C in which the catalyst (camphorquinone) has been incorporated after 192 hours of exposure of said detector to the same alpha source as the detector of Figures 2A to 2C, the crystalline powder having a navy blue color.

[0029] For reasons of readability, the drawings are not necessarily drawn to scale. DETAILED DESCRIPTION OF EMBODIMENTS Definitions

[0030] In the following, the term ionizing radiation refers to radiation with an energy level high enough to cause atoms to lose electrons and ionize directly or indirectly. Ionizing radiation can be in the form of particles with an energy greater than 20 eV, such as alpha or beta particles. Said particles, by virtue of their mass and charge, will, when passing through matter, disrupt the electronic procession of the atoms encountered and eject electrons from the outer layers of said atoms. This is called direct ionization. Alternatively or additionally, ionizing radiation can be in the form of electromagnetic waves such as gamma rays and / or X-rays. The absorption of X-rays and gamma rays by certain atoms causes the ejection of the internal electrons of said atoms. The electrons thus ejected having a mass and a charge non-zero will then ionize other atoms. This is called indirect ionization. These high-energy particles and electromagnetic waves are released from radioactive atomic nuclei which disintegrate.

[0031] Alpha radiation is understood to mean a particle consisting of two protons and two neutrons charged 2+ also identified as a helium nucleus 4He2+. The mass of the alpha particle is 6.6 1027 kg and its mass energy is between 3 MeV and 9 MeV. For example, the decay reaction of Am into Np emits alpha radiation, the most significant of which are 5.486 MeV and 5.443 MeV. As another example, the decay reactions of Ra into Rn then into Po and of U into Th also emit alpha radiation.

[0032] Beta radiation is understood to mean a particle consisting of a positive charge or a negative charge of mass 9.1 1031 kg also identified as a positron or an electron respectively. The energy of the beta particle is between zero and the maximum energy allowed by the beta decay reaction at the origin of the emission. For example, the decay reactions of 60Co into 60Ni, of IA 1 A H to He and C to N emit beta radiation.

[0033] Gamma radiation is understood to be electromagnetic radiation with a wavelength between 10 14 m and 10 12 m. Gamma radiation is generally emitted during the de-excitation of an atomic nucleus resulting from a disintegration. For example, the beta decay reaction of 60Co to 60Ni generates a first gamma radiation at 1.17 MeV and a second gamma radiation at 1.33 MeV. The beta decay reaction of Cs to Ba generates gamma radiation at 661 keV. As another example, the alpha decay reaction of 241 Am to 239 Nb generates gamma radiation at 60 keV.

[0034] X-rays are understood to be electromagnetic radiation with a wavelength between 10 8 m and 10 11 m. X-rays are emitted during the rearrangement of the electronic layers of an atom following the ejection of an electron from an inner electronic layer, for example by collision with a target electron or interaction with gamma radiation. More precisely, during said rearrangement, an electron from an outer electronic layer fills the inner vacancy, releasing energy in the X-ray range.

[0035] The term catalyst is understood as a molecule capable of increasing the kinetics of a chemical reaction, said catalyst being able to be regenerated or not at the end of the reaction.

[0036] The term contamination designates the presence of radioactive substances - in other words emitting ionizing radiation - on any surface of a biological nature (for example skin or hair) or non-biological nature (for example walls or objects in a room, tools or clothing of workers) or in solids, liquids or gases where their presence is involuntary and / or undesirable. Ionizing radiation detector

[0037] The invention relates to a detector of ionizing radiation, for example of ionizing radiation emitted by radioactive substances disseminated in a room, or on the skin, hair or clothing of a human being. Preferably, the invention relates to an alpha particle detector. Place of use of the detector

[0038] The detector according to the invention can be used in any industrial installation in which ionizing radiation is likely to be emitted or contamination emitting ionizing radiation is likely to be disseminated, in order to detect said contamination or said radiation and thus protect the workers in said industrial application with the appropriate level of protection. The detector according to the invention is of particular interest in nuclear power plants in operation or being decommissioned where the risk of encountering this type of contamination is significant. The detector according to the invention can also be used in biology or in irradiation tests.

[0039] By way of example, the detector according to the invention can be formulated in solid form as a coating (for example gel), film, strip, pellet, flexible collars. The size and shape of the detector can be adapted according to the geometry of the object or surface to be controlled. The coating or strip advantageously makes it possible to detect contamination over large surfaces. The pellet can advantageously be positioned in a location that is difficult to access to make a smear.

[0040] In solid form, the detector can be placed directly on construction sites, in premises likely to be contaminated or exposed to ionizing radiation, for example on the walls of contamination containment airlocks, pipes, valves, taps, etc. which are areas where early detection of contamination is necessary. It can be placed on tools (hammers, screwdrivers, etc.) or complex-shaped construction site equipment, the control of which by contaminameter is time-consuming (for example scaffolding). The detector can also be placed on the clothing of construction site operators so as to identify which ones are contaminated and thus avoid external or internal contamination of the worker. The detector can also participate in the analysis of the transfer of contamination onto the clothing of workers during the undressing phase.

[0041] Typically, radioactive particles emitting alpha or beta radiation will be detected by the detector if the detector is positioned at the maximum approximately 5 cm of said particles and gamma radiation can be detected up to a few meters from their source. These characteristics make it possible, in particular, to determine the number and location of the most suitable detectors for the site.

[0042] Alternatively, the detector can be used off-site to analyze a smear (material rubbed near a suspected source of contamination) during indirect measurements.

[0043] General principle of the detection of ionizing radiation by the detector

[0044] The detector according to the invention comprises a monomer and a catalyst.

[0045] The monomer used in the detector according to the invention is in a crystalline form and polymerizes in the solid state, which in particular makes it possible to avoid the use of a solvent and therefore possible problems of leaktightness of the detector and / or toxicity of said solvent.

[0046] The catalyst included in the detector according to the invention is specifically chosen so that, when the detector according to the invention is exposed to ionizing radiation, the catalyst absorbs said ionizing radiation and said absorption catalyzes the polymerization of the monomer, i.e. initiates and accelerates the polymerization reaction of the monomer. Indeed, the absorption of ionizing radiation by the catalyst induces the formation of sites initiating the polymerization of the monomer, thus initiating the polymerization and therefore the change in color of the detector, thereby signaling to an operator the presence of contamination emitting ionizing radiation.

[0047] For example, the absorption of ionizing radiation by the catalyst causes a homolytic cleavage of a bond of said catalyst, thus generating highly reactive free radicals at the origin of a radical chain polymerization, which corresponds to a type I catalysis. For example again, the absorption of ionizing radiation by the catalyst causes the passage of said catalyst into an excited state, the catalyst in the excited state then interacting with another molecule called a co-catalyst, thus generating free radicals, which corresponds to a type II catalysis. The co-catalyst may be chosen from amines and benzophenones. For example, the co-catalyst is chosen from triethylamine, methyldiethanolamine and / or 4,4'-bis(dimethylamino)benzophenone.

[0048] In the detector according to the invention, the catalyst is incorporated inside the crystalline form of the monomer. In other words, inside the crystalline form of the monomer, the monomeric units are arranged in a well-ordered and regular spatial arrangement, and the catalyst is inserted between said well-ordered monomeric units. Such an organization of the catalyst very advantageously makes it possible to obtain a very close proximity between the catalyst molecules and the monomer molecules, so that all the initiator sites of the polymerization created following the absorption of ionizing radiation by the catalyst will then be able to add to the monomeric units and thus cause the polymerization of the monomer.

[0049] The monomer is further specifically chosen so that its polymerization results in a change or appearance of color between the monomer state and the polymer state. Thus, if the monomer is colored, the polymer is of another color. Alternatively, if the monomer is not colored, the polymer is colored. Thus, if the monomer is colored and the polymer of another color, the presence of ionizing radiation is deduced from the detector by a change in color of the detector. Alternatively, if the monomer is not colored and the polymer is colored, the detection of ionizing radiation by the detector of the invention is based on the appearance of a coloration.

[0050] The detection of ionizing radiation is therefore based on the change in color of the detector. A change in color is understood to mean a change in color visible to the naked eye, i.e. one that the eye can detect directly, without the use of other measuring devices. The detector, particularly in its solid form, can be placed by the operator near the area of ​​the construction site that the said operator wishes to monitor. During the intervention, the visual inspection of the detector allows the operator to remotely and continuously monitor the radiological state of the construction site (corresponding to the absence or presence of contamination). When contamination occurs, the operator can see it with the naked eye by the change in color of the detector: he can initiate decontamination of the equipment concerned, or change the collective and individual protections put in place on the basis of theoretical studies of site preparation.

[0051] According to a particular embodiment of the detector according to the invention, the color of the polymer varies with the polymerization rate, said polymerization rate being related to the absorbed dose, so that the detector can further give a quantitative value of the absorbed energy or dose (energy per kilogram of material exposed to radiation). For example, the detector is provided with a color scale relating a given color of the detector to the corresponding dose. The evaluation of the absorbed dose for the establishment of said scale can comprise: - Evaluation of the polymerization rate associated with a given color by differential scanning calorimetry; - From the said polymerization rate, the calculation of the absorbed dose using a prior calibration.

[0052] In one variant, the monomer does not absorb ionizing radiation, and it is only the presence of the catalyst which makes it possible to initiate the polymerization reaction, following the absorption by the catalyst of ionizing radiation. In other words, the detection of ionizing radiation would not be possible without the use of the catalyst.

[0053] In a preferred variant, the catalyst and the monomer both absorb the incident ionizing radiation and the polymerization of the monomer is further activated following absorption of at least a portion of the ionizing radiation by the monomer. In other words, when the chosen monomer absorbs at least a portion of the ionizing radiation by the monomer, said absorption causes the formation of polymerization initiator sites from said monomer, for example the formation of primary radicals which will then add to other monomeric units. The simultaneous absorption of the ionizing radiation by the catalyst makes it possible to catalyze, i.e. to accelerate the polymerization.

[0054] Consequently, in the presence of the catalyst generating polymerization initiator sites, the response time of the detector and the minimum activity necessary to generate a color change observable to the naked eye are reduced, including for alpha radiation. Reading the result then does not require an additional reading device, the result is given directly without correction or interpretation and can be observed remotely. The device is a passive device not requiring an external power supply which can therefore be put in place from the start of the worksite and which informs the operator of the appearance of contamination quickly without repeated measurements or interventions by the operator to recharge the device.

[0055] The sensitivity of the detector is defined as being, for a source emitting ionized radiation, the minimum activity of the source from which the color change of the detector is visible to the naked eye.

[0056] The response time of the detector is defined as being, for a source emitting ionizing radiation of a given activity, the time after which the change in color of the detector is visible to the naked eye.

[0057] Typically, the color change is observable with the naked eye on the detector of the invention after an exposure time of between 1 hour and 8 hours of said detector to a source of alpha radiation with an activity of between 130 Bq and 330 Bq. When the source is a smear, such an activity range is representative of a surface contaminated at a level of 4 Bq / cm2 to 10 Bq / cm2. Such sensitivity makes the detector according to the invention compatible with use on a nuclear power plant operating or dismantling site lasting a few hours or a few days. Definition of monomer

[0058] The monomer is advantageously a monomer from the family of diacetylenic compounds. A diacetylenic compound designates a compound comprising two C=C triple bonds. The polymerization of diacetyl monomers can result from a 1,4 addition between the C1 carbon atom of a diacetyl unit and the C4 atom of the adjacent diacetyl unit. Indeed, diacetyl monomers polymerize in the solid state.

[0059] Diacetylene monomers have the advantage of not being colored or having a pale yellow, white or even slightly bluish coloring unlike their polymerized form, which is colored, so that the polymerization reaction causes a color change visible to the naked eye. In addition, the color of the polymer typically depends on the polymerization rate (ranging from light blue for low polymerization rates to dark blue, violet, dark violet, black to golden black for polymerization rates close to saturation). This correspondence between color and polymerization rate can advantageously be exploited by establishing for each type of ionizing radiation UV, X, gamma, beta and alpha, a calibration linking the polymerization rate to the energy deposited on the detector, i.e. the absorbed dose, as described above.For example, the detector may be supplied with a color scale indicating the absorbed dose corresponding to each color. Thus, the detector provides quantitative information on the absorbed dose by simply observing the color of said detector and reading the absorbed dose associated with said color on the color scale.

[0060] For example, the monomer is a diacetylenic monomer of the following formula (I):

[0061] R'-C=CC=C-R2 (I)

[0062] wherein R1 and R2 are independently selected from an optionally substituted C1-C18 hydrocarbon chain, an optionally substituted aryl group and an optionally substituted heteroaryl group, wherein one or more, preferably 1 to 4, methylene groups of said hydrocarbon chain are optionally replaced by O, C(O), NH or N-(C1-C6alkyl).

[0063] For the purposes of the present invention, the term "C1-C18 aliphatic chain" means a saturated, linear or branched monovalent hydrocarbon chain comprising 1 to 18, in particular 1 to 12, carbon atoms. According to the invention, an aliphatic chain covers substituted or unsubstituted, linear or branched alkyl, alkenyl or alkynyl groups.

[0064] For the purposes of the present invention, the term “(C1-C6)alkyl” group means a saturated, linear or branched monovalent hydrocarbon chain, preferably comprising 1 to 6 carbon atoms. By way of example, mention may be made of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl or hexyl groups.

[0065] For the purposes of the present invention, the term “alkenyl” group means a monovalent, linear or branched hydrocarbon chain comprising at least one double bond. By way of example, mention may be made of ethenyl, propenyl, allyl, butenyl, pentenyl or hexenyl groups.

[0066] For the purposes of the present invention, the term “alkynyl” group means a monovalent, linear or branched hydrocarbon chain comprising at least one triple bond. By way of example, mention may be made of ethynyl, propynyl, butynyl, pentynyl or hexynyl groups.

[0067] For the purposes of the present invention, the term "aryl" means an aromatic hydrocarbon group, preferably comprising from 6 to 10 carbon atoms, and comprising one or more fused rings, such as, for example, a phenyl or naphthyl group. Advantageously, this is phenyl.

[0068] For the purposes of the present invention, the term "heteroaryl" means an aromatic group comprising 5 to 10 cyclic atoms including one or more heteroatoms, advantageously 1 to 4 and even more advantageously 1 or 2, such as, for example, sulfur, nitrogen or oxygen atoms, the other cyclic atoms being carbon atoms. Examples of heteroaryl groups are furyl, thienyl, pyrrolyl, pyridinyl, imidazolyl, triazolyl, tetrazolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, pyrazolyl, oxadiazolyl, thiadiazolyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, quinolyl, isoquinolyl, quinoxalyl or indyl.

[0069] By "optionally substituted" is meant, for the purposes of the present invention, that the group in question is optionally substituted by one or more, preferably 1 to 3 and in particular 1 or 2, substituents chosen from the group consisting of a halogen atom, a C1-C6 alkyl group, OH, oxo, aryl, heteroaryl, N3, CN NO2, NRa Rb, CORC, CO2Rd, CONReRf, and ORS, in which Ra to Rs represents, independently of one another, H, C1-C6 alkyl, or aryl.

[0070] Advantageously, R1 and R2 independently represent a C1-C18 hydrocarbon chain, optionally substituted by an aryl group, such as a phenyl, or heteroaryl, such as a pyridinyl, in which between 1 and 4 methylene groups are optionally replaced by O, C(O), NH or N-(C1-C6alkyl).

[0071] Preferably, the monomer of formula (I) comprises at least one hydrogen bond donor site and one hydrogen bond acceptor site.

[0072] A hydrogen bond is a non-covalent interaction between an atom carrying a lone pair and a hydrogen atom bound to an electronegative atom (N, O or S). The hydrogen bond donor site is this electronegative atom and the hydrogen bond acceptor is the atom carrying the lone pair.

[0073] When the monomer is in crystalline form, these hydrogen bonds formed between an acceptor site of a first monomer of formula (I) and a donor site of a second monomer of formula (I) make it possible to promote a spatial arrangement of the monomer molecules relative to each other which is optimal for the topochemical polymerization to take place, in particular via a 1,4 addition between the carbon atom C1 of a diacetylenic unit and the atom C4 of the adjacent diacetylenic unit.

[0074] Thus, the monomer of formula (I) advantageously comprises one or more functions carrying hydrogen bond donor and acceptor site(s) such as the amide function of formula -NH-C(O)-, the urea function of formula -NH-C(O)-NH, the carbamate function of formula -OC(O)-NH, where the -NH- site is the donor of a first hydrogen bond and where the -C(O)- site is the acceptor of a second hydrogen bond.

[0075] In a preferred embodiment, the monomer of formula (I) comprises at least one urethane function of formula -NH-C(O)-O-Ci-Ci2 alkyl or -OC(O)-NH-C i-C12 alkyl.

[0076] Thus, preferably, R1 and R2 independently represent a C1-C18 hydrocarbon chain, optionally substituted by an aryl group, such as a phenyl, or heteroaryl, such as a pyridinyl, said hydrocarbon chain being interrupted by one or more urea groups of formula -NH-C(O)O-.

[0077] More preferably, R1 and R2 independently represent a group of formula -(CH2)mOC(O)-NH-(CH2)n-CH3 or -(CH2)m-NH-C(O)-O-(CH2)n-CH3, m and n each being independently an integer ranging from 0 to 9.

[0078] R1 and R2 may be the same or different. Preferably, R1 and R2 are the same.

[0079] Preferably, the monomer of formula (I) is chosen from the group consisting of:

[0080] in which n and m are each independently of the other an integer ranging from 1 to 10.

[0081] More preferably, the monomer of formula (I) corresponds to the following formula (IA):

[0082] In the monomer of formula (I) in crystalline form, the spatial organization is particularly ordered, which makes the topochemical polymerization of said monomer particularly efficient. Such an organization is advantageous for obtaining high degrees of polymerization and therefore a color change easily visible to the naked eye, which makes it possible to dispense with the use of other additives such as an opacifier or a colorant in the detector. In addition, said monomer is not sensitive to the presence of dioxygen, which makes it possible to dispense with the use of an antioxidant in the detector.

[0083] For example, the monomer (IA) has a pale blue color, while the polymer has a blue coloration which is darker as the degree of polymerization increases, thus making it possible to quantify the absorbed dose using a color scale.

[0084] The monomers of formula (I) according to the invention typically absorb ionizing radiation emitted between 200 nm and 450 nm. Definition of catalyst

[0085] The catalyst used in the detector of the invention and as described in the present description may be chosen so that its absorption spectrum extends in a wavelength range between 250 nm and 475 nm. The catalyst used in the detector of the invention is typically chosen from the group consisting of type I or type II catalysts, including benzoquinones, quinones and their derivatives.

[0086] The catalyst is present in a small amount relative to the monomer in the crystal of said monomer. For example, the amount of catalyst is between 0.01% and 10% by mass relative to the mass of monomer initially present in the detector.

[0087] Arrangement of the crystal form of the monomer in the detector

[0088] The crystalline form of the monomer, in which the catalyst is incorporated, is arranged in the detector, so that when the detector is in the presence of ionizing radiation, all or part of said ionizing radiation can be absorbed directly by the catalyst and possibly the monomer. Typically, the detector is arranged so that ionizing radiation external to said detector does not pass through a thickness of material of said detector greater than 15 μm, preferably greater than 10 μm before reaching the catalyst. Preferably, the detector is arranged so that ionizing radiation external to said detector does not pass through any material before reaching the catalyst. Detector for direct measurements

[0089] The monomer may be in the form of a crystalline powder, in other words in the form of a powder consisting of monomer crystals, the catalyst being incorporated inside each of said monomer crystals. More specifically, in each monomer crystal which constitutes the crystalline powder, the monomeric units are ordered according to a well-defined spatial organization, and the catalyst molecules are intercalated between said monomeric units thus ordered. Alternatively, the monomer may be in the form of at least one macroscopic crystal, the catalyst being incorporated inside the macroscopic crystal.

[0090] In a particular embodiment, the monomer is included in a non-agglomerated or non-compacted solid composition. Typically, the composition comprises the monomer crystal powder as previously mentioned without additional shaping, optionally mixed with additives, for example opacifiers. Preferably, the detector does not comprise such additives and the non-agglomerated solid composition consists of the crystalline monomer powder as described above.

[0091] In an alternative embodiment, the monomer is included in a layer, in particular a layer arranged on a support. By layer is meant any agglomerated or compacted solid composition.

[0092] For example, the monomer crystal powder as previously mentioned is agglomerated in a polymer binder in the form of a layer, said layer possibly further comprising one or more additives.

[0093] Preferably, the layer does not comprise a polymer binder and / or additives other than the monomer and the catalyst. For example, the layer does not comprise an opacifier, colorant, and antioxidant. Typically, if the monomer is present in the form of a powder of monomer crystals in which the catalyst is incorporated, the layer may consist solely of said compacted powder of monomer crystals. Alternatively, if the monomer is available in the form of a macroscopic crystalline block in which the catalyst is incorporated, the layer may consist solely of such a crystalline block.

[0094] Arranging the monomer in the form of a non-compacted crystalline powder or a layer not comprising a polymer binder advantageously makes it possible not to dilute the monomer in a neutral polymer matrix which could lead to the formation of monomer clusters, and therefore to a lower visual impact of the color change compared to the configuration in which the same quantity of monomer would be distributed homogeneously. In addition, by intercalating polymer chains of the polymer binder between the monomers, there is a risk of breaking the spatial arrangement of the monomers and therefore of obtaining a lower reactivity of the monomer. Thus, for the same absorbed dose of ionizing radiation, the use of a polymer binder leads to a less pronounced color change.

[0095] A layer not comprising additives makes it possible to have a detector that is easier to shape. As previously mentioned, the catalyst of the detector according to the invention advantageously makes it possible to increase the sensitivity of said detector, so that the change in color is visible to the naked eye for very low activities (change in color visible to the naked eye after a period of between 1 hour and 8 hours of exposure of said detector to a source of alpha radiation with an activity of between 130 Bq and 330 Bq) without it being necessary to add an opacifier and / or a dye to said detector.

[0096] As previously mentioned and with reference to [Fig.l], the detector may therefore comprise a layer comprising, in particular consisting of, the monomer in a crystalline form and the catalyst incorporated in said crystalline form, otherwise called active layer 2, and said active layer 2 may be arranged on a support 1. The active layer 2 is according to any one of the embodiments previously described. The thickness of the active layer 2 is typically between 10 μm and 2 mm.

[0097] The support 1 is for example in the form of a polymer film typically comprising polyester, polyethylene, polypropylene and / or polyethylene terephthalate. The thickness of the support is for example between 10 μm and 2 mm.

[0098] Direct exposure of the active layer 2 of the detector of [Fig.l] to ionizing radiation will induce the color change of the active layer 2.

[0099] Preferably, the detector further comprises means for fixing the active layer 2 to the support 1 which are reversible. For example, the detector does not comprise glue at the interface between the active layer 2 and the support 1. Thus, the active layer 2 can be replaced after use of the detector and said detector reused. For this purpose, the means for fixing the active layer 2 to the support 1 may comprise an outer frame. For example, the outer frame may comprise a back board, a front board and a press. When the detector is positioned inside the outer frame, the active layer 2 is arranged on the support 1 and the superposition of the active layer 2 and the support 1 is interposed between the back board and the front board of the outer frame, the press of the outer frame applying a clamping pressure of the front board against the back board, so that the active layer 2 is kept fixed against the support 1. Alternatively, the support may form the back board of the outer frame.

[0100] The press comprises for example at least two butterfly screws. According to this embodiment, the rear board and the front board each comprise at least two orifices, each orifice of the rear board coinciding with an orifice of the front board when the detector is mounted inside the outer frame. Each butterfly screw is configured so that, when the detector is mounted inside the outer frame, the butterfly screw passes through an orifice of the front board and the orifice of the rear board which coincides with the orifice of the front board, and applies a clamping pressure of the front board against the rear board. The butterfly screws advantageously make it possible to limit the FME (acronym for the English term "Foreign Material Exclusion") risk, in particular when the detector is intended to be used in a building of a reactor of a nuclear power plant, because said screws are configured not to unscrew on their own.In fact, in this type of building, it is important not to lose tools which, if they fall into the reactor, could damage the fuel assemblies of the reactor in operation.

[0101] Alternatively, the pressure comprises at least two clamps, for example at least two toggle clasps or at least two butterfly clasps: the pressure for clamping the front board against the rear board is applied by said clamps when the superposition of the rear board and the front board inside which the detector is inserted is inserted between the clamps.

[0102] Preferably, the outer frame is configured so that when the detector is mounted inside said outer frame, the change in color of the active layer can be visually observed directly without removing the frame. For example, the front board of the outer frame comprises a through hole.

[0103] Detector for carrying out indirect measurements

[0104] A smear of the area suspected of contamination can be deposited on the detector or at a sufficiently close distance (in particular less than or equal to 5 cm) so that the catalyst and possibly the monomer, arranged according to one of the techniques described above, absorb the ionizing radiation emitted by the contaminations. present on the smear, which triggers polymerization and causes the color change. Absence of scintillator

[0105] The detector according to the invention is typically devoid of a scintillator. The absorption of ionizing radiation by the catalyst and possibly the monomer is therefore maximized, thereby accelerating the polymerization of the monomer. The detector is also easier to implement without a scintillator.

[0106] Filtering layer for external non-ionizing radiation

[0107] Regardless of the embodiment mentioned above, the detector preferably comprises an external layer arranged so as to filter non-ionizing radiation, for example ultraviolet radiation, external to the devices. Such a non-ionizing radiation filtering layer advantageously makes it possible to protect the active layer from natural and artificial non-ionizing radiation, in particular when the monomer and / or the catalyst are likely to absorb said non-ionizing radiation, which would have the effect of initiating the polymerization reaction and the change in color of the detector without any link to a dose of ionizing radiation potentially absorbed by the catalyst.For example, an ultraviolet ray filtering layer can be advantageously used when the monomer is a diacetylene compound and the catalyst is a compound chosen from quinones and benzoquinones due to the high sensitivity of said monomer and of the quinones and benzoquinones to ultraviolet radiation.

[0108] In the embodiment of [Fig. 1], the filtering film 9 can be arranged on a front face of the active layer 2 opposite the support 1, so that the active layer 2 is located between the filtering film 9 and the support 1. Such an arrangement of the layers advantageously makes it possible not to expose the active layer 2 to non-ionizing radiation external to the device.

[0109] The thickness of the filtering film 9 preferably ranges from 1 μm to 10 μm. Such a thickness of the filtering film 9 advantageously makes it possible not to block the diffusion of ionizing radiation, in particular alpha radiation, towards the active layer 2.

[0110] The filtering film 9 may be a transparent film comprising a polymer, for example polyester, polyethylene, polypropylene and / or polyethylene terephthalate, and a compound which absorbs non-ionizing radiation, in particular ultraviolet radiation, for example bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and / or methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate. Such a filtering film 9 is for example advantageously obtained by a spin-coating, coating or dip-coating process. [YES] Specific detector for the detection of alpha radiation

[0112] In a particular embodiment, the detector is specific to alpha radiation, that is to say that it changes color in the presence of alpha radiation and not in the presence of beta radiation and / or gamma radiation.

[0113] For this, the detector is for example according to the embodiment of [Fig.l] and further comprises one or more characteristics described below which confer the specificity of the detector to alpha radiation.

[0114] Thus, the detector is advantageously configured so that the thickness of the active layer is between 50 pm and 100 pm, the support being further made of a polished material, for example glass, mylar or aluminum. Indeed, the alpha particles will deposit all their energy in the scintillating solid layer over a thickness of at most 50 pm, or even 25 pm. The thickness of the active layer must therefore be as small as possible so that the beta particles passing through said layer deposit little energy there and so that the gamma radiation is not absorbed. A polished support advantageously makes it possible not to reflect the beta particles and the gamma radiation, so that said particles and said radiation are not backscattered in the active layer when they arrive on the support.

[0115] An embodiment of the detector optimized to be specific for the detection of alpha radiation also makes it possible to obtain a detector that is not very sensitive to the previously mentioned gamma background noise and therefore to avoid the need to implement indirect measurements by first carrying out smears and then analyzing said smears in the low gamma background noise zone. Method for detecting ionizing rays

[0116] The invention also relates to a method for detecting ionizing radiation, for example a method for detecting ionizing radiation emitted by radioactive substances contaminating a room.

[0117] The method for detecting ionizing radiation comprises a preliminary step E0 of providing a monomer and a catalyst. The monomer and the catalyst are as defined previously.

[0118] The method for detecting ionizing radiation comprises a first step E1 of polymerization of the monomer, the polymerization being catalyzed by the catalyst, following absorption by the catalyst of ionizing radiation, the resulting polymer having a color different from the monomer. The ionizing radiation is for example emitted by a particle emitting ionizing radiation.

[0119] Preferably, the polymerization of step E1 is also induced by the absorption by the monomer of ionizing radiation. Thus, the polymerization is jointly initiated by polymerization initiator sites generated from the catalyst and by polymerization initiator sites generated from the monomer.

[0120] The method for detecting ionizing radiation comprises a second step E2 of observing with the naked eye a change in color when the absorbed dose value of ionizing radiation by the detector exceeds a threshold value. The change in color may in particular be the appearance of a color. The change in color is preferably observable with the naked eye on the detector of the invention after an exposure time of between 1 hour and 8 hours of said detector to a source of alpha radiation with an activity of between 130 Bq and 330 Bq.

[0121] Optionally, the observation with the naked eye of the color change can be supplemented by a step E3 of quantification of the absorbed dose. Said evaluation can comprise the comparison of the color of the polymer to a scale linking said color to the measured activity. Implementation of direct measures

[0122] In a particular embodiment of the detection method according to the invention, the supply E0 of the monomer and the catalyst comprises the arrangement E0' of said monomer and catalyst in a construction site area or on an object of said construction site and then the implementation E0'' of the work to be carried out on said construction site, so as to carry out so-called "direct" measurements. Construction site means any area on which maintenance or dismantling work is to be carried out, said area being likely to be contaminated during the course of said work. For example, it may be a maintenance or dismantling site of a nuclear power plant. As another example, the detector may be arranged on the walls of a room, or on a pipe, a hose, a hammer, scaffolding or any object of complex shape.

[0123] According to this particular embodiment of the detection method, the observation of the change in color with the naked eye in step E2 may be followed by an additional step of stopping the work and / or decontaminating the area of ​​the construction site or the contaminated object.

[0124] The detection method according to this embodiment advantageously allows a site operator to continuously monitor during work carried out on said site and remotely, by simple visual inspection, the radiological state (defined by the absence or presence of contamination) of the area of ​​the site in which the monomer and the catalyst or the tool on which they are placed are arranged. When contamination occurs during the work, the operator is immediately informed of said contamination simply by perceiving the change in color without needing to approach to carry out an additional measurement, which limits the risk of contamination of said operator during the measurement operation. In addition, the change in color allows him to immediately adapt his intervention as needed.

[0125] Alternatively or additionally, the arrangement E0' of said monomer and catalyst can be made on the outfits of the workers, in the airlocks and / or to monitor the undressing operations of said workers.

[0126] In the particular case where the detector comprises an active layer, said active layer being reversibly fixed to the other elements of the detector, the detection method may further comprise a step E3 of changing the active layer which has changed color with a new non-colored active layer. Implementation of indirect measures

[0127] In an alternative embodiment of the indirect measurements, the supply E0 of the monomer and the catalyst may comprise a sub-step EO-a of carrying out a smear on an area or a tool of a construction site suspected of being contaminated, a sub-step EO-b of bringing the monomer and the catalyst into contact and then a sub-step EO-c of bringing said smear into contact or bringing it closer to a maximum distance of 5 cm with the monomer and the catalyst, so that the ionizing radiation absorbed by the catalyst and possibly the monomer in step E1 is the ionizing radiation emitted by the contaminations on the smear.

[0128] Method of manufacturing an ionizing ray detector

[0129] The invention extends to a method of manufacturing an ionizing radiation detector comprising a monomer and a catalyst for the polymerization reaction of the monomer, in particular to a method of manufacturing an ionizing radiation detector according to any one of the embodiments previously described.

[0130] In particular, the method of manufacturing the ionizing radiation detector comprises incorporating the catalyst within the crystalline form of the monomer, the catalyst catalyzing the polymerization of the monomer following absorption of ionizing radiation and the resulting polymer having a color different from the monomer.

[0131] Preferably, the incorporation of the catalyst inside the crystalline form of the monomer is carried out in a recrystallization process.

[0132] According to a particular embodiment of the recrystallization, the monomer and the catalyst are dissolved hot in a solvent. In an alternative embodiment of the recrystallization, the monomer and the catalyst are melted together without solvent. Such an embodiment of the recrystallization has the advantage of not comprising a potentially toxic solvent to be evaporated. Said embodiment of the recrystallization is therefore easier to implement and less dangerous.

[0133] In the following, a particular example of the embodiment of recrystallization with solvent is described. The solvent is for example tetrahydrofuran or chloroform. Then, the solution obtained is left to cool to room temperature. ambient temperature, i.e. between 18°C ​​and 25°C. Said solution is then placed in the cold for a period preferably between 30 minutes and 48 hours, for example for one hour, so as to precipitate a crystal comprising the monomer and the catalyst. When the solution is placed in the cold, the temperature is preferably between -20°C and 5°C. Then, the solution is filtered, so as to recover the precipitated crystal. Finally, the crystal is preferably dried under vacuum at room temperature in order to remove the residual solvent.

[0134] In the following, a particular example of the embodiment of the solvent-free recrystallization is described. The monomer and the catalyst are melted together without solvent at a temperature which may be between 90°C and 120°C. Then, the mixture obtained is allowed to cool to room temperature, i.e. between 18°C ​​and 25°C.

[0135] Alternatively to recrystallization, the incorporation of the catalyst into the monomer crystal may comprise the hot dissolution of the catalyst and the monomer in a solvent followed by evaporation at room temperature, under vacuum or at atmospheric pressure, of said solvent.

[0136] Formation of a layer comprising the crystalline form of the monomer in which the catalyst is incorporated

[0137] The manufacturing method may further comprise a step of forming a layer, called an active layer, comprising the monomer in its crystalline form and the catalyst incorporated in the crystalline form of the monomer.

[0138] For example, in the case where the crystalline form of the monomer in which the catalyst is incorporated is a crystalline powder, the formation of the active layer may comprise the agglomeration of the crystalline powder alone or mixed with other powders with a polymeric binder.

[0139] Preferably, however, the formation of the active layer does not include additional steps of introducing a polymer binder or additives into the powder or powder mixture prior to deposition. For example, the formation of the active layer may include compacting the crystalline powder alone or mixed with other powders: the powder or powder mixture comprising the monomer and the catalyst is deposited on a press support and then the powder is compacted using a press, so as to form the active layer.

[0140] Preferably again, the active layer comprises only the crystalline form of the monomer in which the catalyst is incorporated.

[0141] The thickness of the active layer is typically between 10 μm and 2 mm, preferably between 50 μm and 100 μm.

[0142] The manufacturing method may further comprise a step of arranging the active layer on a support.

[0143] The attachment system may be reversible, and comprise for example an external frame as previously described. An arrangement between the active layer and the reversible support advantageously makes it possible to replace the active layer after use of the detector while keeping the same support.

[0144] Alternatively, the arrangement of the non-scintillating active layer on the support may comprise bonding using an adhesive which preferably does not degrade under radiation and does not emit parasitic non-ionizing radiation.

[0145] Alternatively, the arrangement of the non-glittering active layer on the support may comprise bonding the non-glittering active layer and the support by heating. In a first step of the bonding by heating, the two layers are heated to a temperature close to their melting point. For example, in the case where the non-glittering active layer is a layer of compacted powder of diacetylene monomer crystal, the two layers are heated to a temperature between 90°C and 120°C. Then, the two layers are brought into contact and left to cool together under pressure.

[0146] The support may be a polymer layer or film comprising for example polyester, polyethylene, polypropylene and / or polyethylene terephthalate, the thickness of the support being able to be between 10 μm and 2 mm.

[0147] Arrangement of a filtering film on the layer comprising the crystalline form of the monomer in which the catalyst is incorporated

[0148] The method for manufacturing the ionizing radiation detector may further comprise a step of arranging a non-ionizing radiation filtering film on a front face of the active layer opposite the support if said layer is deposited on a support, so that the detector then comprises from its rear face to its front face: the support, the active layer and the non-ionizing radiation filtering film.

[0149] Preferably, the film for filtering external non-ionizing radiation has a thickness of between 1 μm and 10 μm. Such a thickness of the film for filtering external non-ionizing radiation is sufficiently low so as not to block the diffusion of alpha radiation towards the active layer.

[0150] The arrangement of the external non-ionizing radiation filtering film is advantageously implemented so that no additional material is present between the external non-ionizing radiation filtering film and the active layer. In particular, the arrangement of the non-ionizing radiation filtering film preferably does not use glue. Indeed, any additional material can absorb or diffuse ionizing radiation.

[0151] The arrangement of the external non-ionizing radiation filtering film may comprise the prior preparation of said filtering film, for example by spin-coating, coating or dip-coating, so as to obtain a self-supporting external non-ionizing radiation filtering film.

[0152] By "dip coating" is meant a deposition means where the surface to be treated is immersed and then removed from a solution / suspension at a defined speed (LD Landau, VG Levich, Acta physicochimica, USSR, 17, (1942), 42).

[0153] By "spin coating" is meant a deposition means where a solution / suspension is deposited on the surface to be covered. This same surface is fixed on a spinning wheel which rotates it at a controlled speed which allows the suspension solution to spread there and wet the whole surface (D. Meyerhofer, J. Appl. Phys., 49, (1978), 3993).

[0154] By coating is meant a deposition means where a solution / suspension is deposited onto the surface to be coated at a controlled rate.

[0155] More specifically, the prior preparation of the external non-ionizing radiation filtering film may comprise the deposition, by coating, spin-coating or dip-coating as previously mentioned, on a support, of a solution comprising a polymer and additives which absorb non-ionizing radiation, for example on a polytetrafluoroethylene support, then the drying of said solution on the support so as to obtain the filtering film, and finally the detachment of the filtering film which is self-supporting from the support. The polytetrafluoroethylene support advantageously makes it possible to avoid adhesion between said support and the newly generated film. For example, the solution comprising the polymer and the additives is a polyethylene solution comprising the additive TINUV-2 from the company Stardust.

[0156] Such a method for preparing the filter film advantageously makes it possible to precisely control the thickness of the filter film and to obtain a filter film with a thickness of less than 10 μm. A filter film having such a low thickness is not commercially available.

[0157] Following the prior preparation of the self-supporting external non-ionizing radiation filtering film, the arrangement of the external non-ionizing radiation filtering film preferably comprises an additional step of fixing said self-supporting external non-ionizing radiation filtering film to the active layer, preferably with fasteners allowing reversible fixing between the filtering film and the rest of the detector. For example, the fastener is an external frame as previously described.

[0158] In an alternative embodiment, the arrangement of the external non-ionizing radiation filtering film may comprise the preparation of said external non-ionizing radiation filtering film directly on the active layer. For example, the preparation of the external non-ionizing radiation filtering film may comprise the deposition by spin-coating, coating or dip-coating of a solution comprising a polymer and additives as previously described directly at the surface of the active layer. According to this alternative, however, if the adhesion between the active layer and the newly formed filtering film is good, the adhesion between said newly formed filtering film and the active layer is definitive. In particular, the arrangement of the external non-ionizing radiation filtering film does not comprise an additional step of fixing said external non-ionizing radiation filtering film to the active layer.

[0159] Example of an ionizing ray detector according to an embodiment of the invention

[0160] The monomer 6-BU (hexane-6-diacetylene-l-diurethane butyl) in the form of a crystalline powder obtained by recrystallization with solvent is exposed to an alpha source at a flux ranging from 70 to 150 alpha / s (source characteristics: 241Am of 3.5 MBq of diameter 80 mm with a flux of 1700 a / s / 2pi sr). The distance between the source and the powder is between 1 mm and 20 mm.

[0161] In the solvent recrystallization carried out, the solvent is tetrahydrofuran or chloroform. The 6-BU monomer is dissolved hot in the solvent and then the solution obtained is left to cool to room temperature, i.e. between 18°C ​​and 25°C. Said solution is then placed between -20°C and 5°C for one hour, until precipitation of the monomer. Then, the solution is filtered, so as to recover the precipitated crystal. Finally, the crystal is dried under vacuum at room temperature in order to remove the residual solvent.

[0162] The crystalline powder of the monomer is initially light blue in color (see [Fig.2A]). After 64 hours of exposure to said alpha source, said crystalline powder has a dark blue color and the polymerization rate is evaluated as being less than 1% (see [Fig.2B]). After 350 hours of exposure, the color of the crystalline powder has evolved into navy blue and the polymerization rate is evaluated as being 8% (see [Fig.2C]).

[0163] The same monomer in the form of a crystalline powder in which the camphorquinone catalyst obtained by recrystallization with solvent under the conditions described above has been incorporated, is exposed to the same alpha source under the same conditions as the crystalline powder without catalyst. The navy blue color is observed after 192 hours of exposure to said source (see [Fig.2D]) and the polymerization rate is then evaluated at 7%.

[0164] Thus, the color of the monomer changes with the absorbed dose, so that the color of the monomer can be used to evaluate the absorbed dose. In addition, the catalyst makes it possible to achieve the same polymerization rate in a time almost half as short. In other words, the catalyst has effectively made it possible to improve the kinetics of the polymerization reaction under exposure to ionizing radiation of the alpha radiation type.

[0165] All the previously mentioned polymerization rates are evaluated by differential scanning calorimetry according to the following protocol.

[0166] Device used: DSC 25 TA

[0167] 3 to 10 mg of 6-BU powder are placed in a crucible.

[0168] - Characteristics of the test:

[0169] o Scanning speed of 50 ml / min with a nitrogen flow (in order to avoid parasitic reactions

[0170] with the oxygen in the air, the tests are carried out under an inert atmosphere);

[0171] o Temperature ramp program:

[0172] —> Cooling from T = 20 °C to T = -20 °C in 1 min (to bring

[0173] the sample at the scanning start temperature);

[0174] —> 2 min isotherm;

[0175] -> Heating from T = -20 °C to T = 170 °C in steps of 10 °C / min;

[0176] —> 1 min isotherm;

[0177] ->Cooling from T = 170 °C to T = -20 °C in steps of 10 °C / min.

Claims

Claims

1. An ionizing radiation detector, the detector comprising: - a monomer in a crystalline form, - and a catalyst incorporated within the crystalline form of the monomer, the catalyst catalyzing the polymerization of the monomer following absorption of ionizing radiation, the polymer resulting from the polymerization of the monomer having a different color from the monomer.

2. Detector according to the preceding claim, in which the polymerization of the monomer is further activated following absorption of ionizing radiation by the monomer.

3. A detector according to any preceding claim, wherein the monomer is in the form of a crystalline powder.

4. Detector according to one of the preceding claims, in which the monomer is included in a layer, in particular a layer arranged on a support.

5. Detector according to the preceding claim, in which the layer has a thickness of between 10 pm and 2 mm, preferably a thickness of between 50 pm and 100 pm.

6. A detector according to claim 4 or 5, wherein the layer does not comprise a polymer binder and / or additives.

7. A detector according to one of claims 4 to 6, wherein the layer consists solely of the compacted crystalline powder of the monomer or wherein the layer consists of a mixture of compacted powders comprising the crystalline powder of the monomer.

8. Detector according to one of the preceding claims, in which the monomer is a diacetylenic monomer of the following formula (I): R'-C=CC=C-R2 (I) in which R1 and R2 are independently chosen from an optionally substituted C1-C18 hydrocarbon chain, an optionally substituted aryl group and an optionally substituted heteroaryl group, in which one or more, preferably from 1 to 4 methylene groups of said hydrocarbon chain are optionally replaced by O, C(O), NH or N-(CrC6alkyl)

9. Detector according to one of the preceding claims, in which the catalyst is chosen from quinones and benzoquinones.

10. A method for detecting ionizing radiation comprising the following steps: E0) Providing a detector as defined in claims 1 to 9, E1) Polymerizing the monomer, the polymerization being catalyzed by the catalyst, following absorption by the catalyst of ionizing radiation, the resulting polymer having a color different from the monomer, E2) Observing the color change with the naked eye.

11. A method of manufacturing an ionizing radiation detector comprising incorporating a catalyst within the crystalline form of a monomer, the catalyst catalyzing the polymerization of the monomer following absorption of ionizing radiation and the resulting polymer having a color different from the monomer.

12. A method according to the preceding claim, wherein the catalyst is incorporated within the crystalline form of the monomer by a recrystallization process.

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