RU195097U1 - Device for detecting explosive, poisonous and fissile materials on the seabed - Google Patents

Abstract

A utility model relates to the field of research or analysis of materials by radiation methods with the measurement of nuclear radiation. EFFECT: increased probability of detecting highly shielded weapons-grade uranium in an object of research located on the seabed. A device for detecting explosive, poisonous and fissile materials on the seabed contains a pulsed neutron deuterium-deuterium generator, scintillation gamma detectors and an amplitude analyzer with a time window for measuring gamma rays of neutron radiation capture, scintillation gamma detectors and pulsed neutron deuterium-deuterium generator connected to an amplitude analyzer, gamma-ray scintillation detectors are placed in a fluorine-containing substance surrounding gamma-ray scintillation detectors, The amplitude analyzer has a time window for measuring gamma rays of the isotope N generated by the interaction of fission neutrons emitted during neutron irradiation of a test object containing fissile material with a fluorine-containing substance, the volume and location of the fluorine-containing substance, as well as the volume and location of scintillation gamma detectors be such that the product of the isotope N production time in a fluorine-containing substance by fission neutrons and the probability of detecting gamma rays with an energy of 6.1 3 MeV, leaving fluorine-containing substances, with scintillation gamma detectors was not less than 6.25 / T, where T is the time of detection. 4 ill., 1 tab.

Description

The utility model relates to the field of research or analysis of materials by radiation methods with the measurement of nuclear radiation arising under the influence of neutrons, and can be used to detect hazardous (explosive, poisonous and fissile) substances on the seabed using neutron analysis.

Indirect (visual, electromagnetic, chemical) and direct nuclear-physical methods can be used to control hazardous substances on the seabed. Indirect methods detect hazardous substances by their physical properties (color, density, dielectric constant, etc.). Direct methods determine the key chemical compounds or elemental composition of explosives. According to experts, only direct methods of neutron analysis, based on the registration of nuclear reaction products in hazardous substances when they are probed by neutron radiation, can provide reliable control of hazardous substances on the seabed [Sudac D., Matika D. and Valcovic V. Detection of Explosives in Objects on the Bottom of the Sea // Application of Accelerators in Research and Industry, AIP Conf. Proceedings, Vol. 1099, 2009, pp. 574-577].

A device for detecting hazardous substances is placed on a submarine, the shell of which prevents the device from contacting with sea water. Features of using neutron analysis methods under these conditions are:

- the difficulty of approaching the detection device to the object of study at short distances due to various factors (sea currents, the dynamics of the submarine, etc.), because of this, the thickness of the water layer between the detection device and the object of study can be up to 0.3 m [Laikin A.I., Grishin D.S., Kyzyurov V.S. et al. Experience in the development of a submersible complex for the identification of explosive, poisonous and radioactive substances in underwater potentially hazardous objects - “Varyag-ChS” // Collection of reports of the international scientific and technical conference “Portable neutron generators and technologies based on them”. - M.: VNIIIA, 2012. - S. 525-534]. This leads to a strong attenuation of both probing neutron radiation and response neutron and gamma radiation;

- large depth (> 10 m) at which the object of study is located. As a result of this, there is practically no neutron and gamma background due to cosmic radiation;

- small usable volume of the submarine to accommodate equipment;

- limited measurement time.

A device for detecting explosives under water using the method of labeled neutrons [Aleksakhin V.Yu., Bystritsky V.M., Zamyatin N.I. et al. Application of the tagged neutron method for the detection of hazardous substances under water // Collection of reports of the international scientific and technical conference “Portable neutron generators and technologies based on them”. - M.: VNIIIA, 2012. - S. 555-567]. The device is housed in a sealed container for underwater operations and contains a neutron generator - a source of monochromatic 14 MeV neutrons with a built-in alpha particle detector, a gamma radiation detector and recording electronics. With the passage of "tagged" neutrons in the object of study, the gamma-ray spectrum is measured. From the analysis of the spectrum, the number of gamma rays arising from inelastic scattering of “labeled” neutrons by the nuclei of carbon, nitrogen and oxygen that are part of the explosives is determined, and the relative concentration of carbon, nitrogen and oxygen in the object under study is determined. A sign of the presence of explosives in the object of study is finding the relative concentration of carbon, nitrogen and oxygen in a certain range of values. The disadvantage of this device is that with its help you can detect only explosives, but you can not detect poisonous and fissile substances.

A known device adopted for the prototype for the detection of explosive, poisonous and fissile substances on the seabed [Laikin A.I., Grishin D.S., Kyzyurov V.S. and others. The experience of developing a submersible complex for the identification of explosive, poisonous and radioactive substances in underwater potentially hazardous objects - "Varyag-ChS" // Collection of reports of the international scientific and technical conference "Portable neutron generators and technologies based on them." - M .: VNIIA, 2012. - S. 525–534], containing a pulsed neutron deuterium-deuterium generator, scintillation gamma detectors, and an amplitude analyzer with a time window. The neutron deuterium-deuterium generator generates pulsed fluxes of probing neutrons with an energy of 2.5 MeV, which slow down in water to thermal energies. Scintillation gamma detectors detect gamma rays arising from the radiative capture of thermal neutrons in the object of study. Explosives are identified by measuring 10.83 MeV gamma rays emitted by nitrogen nuclei. This is due to the fact that all industrial explosives have a high (from 15% to 40%) mass content of nitrogen. Poisoning substances are identified by measuring gamma rays with energies of 5.42 MeV and 3.22 MeV emitted by sulfur nuclei. Sulfur in high concentration is contained in mustard-like poisonous substances, which were massively buried under water. The amplitude analyzer allows for a pulsed neutron generator to obtain a gamma-ray spectrum in a given time window corresponding to the maximum signal-to-noise ratio for the measured gamma-quanta of radiation capture of neutrons. Detection of fissile substances by the prototype device is performed by the passive method of detecting gamma rays of spontaneous radioactive decay.

The disadvantage of this device is the low probability of detection of highly shielded weapons-grade uranium in the object of study located on the seabed. This is due to the fact that the detection of fissile substances by the prototype device is performed by the passive method of detecting gamma rays of spontaneous radioactive decay in the presence of a background of gamma radiation emitted by radioactive isotopes contained in sea water and the seabed. Consider a hypothetical model of a nuclear warhead containing 12 kg of weapons-grade uranium with a tungsten piston, presented in [Fetter S., Frolov A.V., Miller M. Detecting Nuclear Warheads // Science and Global security, Vol. 1, 1990, pp. 225-302]. This model, which represents a nuclear warhead in the form of a set of concentric spheres, was proposed for assessing radioactive radiation from nuclear munitions for the tasks of their control. According to the calculations there, the intensity of gamma radiation emerging from the warhead is J = 30 1 / s. The gamma radiation flux density near the gamma detector can be estimated as

(1)

(1)

where L _W is the range of gamma rays in water. At a distance to the detector r = 30 cm φ _γ = 1,0 · 10 ^-3 1 / (cm ² s). The natural radioactivity of sea water is about q = 1.5 · 10 ^-4 Bq / cm ³ and is mainly due to the spontaneous decay of potassium-40, as well as isotopes of uranium and thorium [Sapozhnikov Yu.A., Aliev R.A., Kalmykov S.N. Radioactivity of the environment. - M: BINOM, 2006. - 286 S.]. The flux density of gamma radiation from radioactive isotopes uniformly dissolved in water is [Gusev N.G., Mashkovich V.P., Suvorov A.P. The physical basis of radiation protection. - M .: Atomizdat, 1980. - 461 S.]

(2)

(2)

where µ is the linear attenuation coefficient of gamma rays in water, equal to 0.03 1 / cm for gamma radiation energy of 1.46 MeV (spontaneous decay of potassium-40). Hence b = 2.5 · 10 ^-3 1 / (cm ² s). When approaching the seabed, the background can increase by almost 10 times, since it contains radioactive isotopes in a higher concentration than in water [Sapozhnikov Yu.A., Aliev R.A., Kalmykov S.N. Radioactivity of the environment. - M: BINOM, 2006. - 286 S.]. Thus, the effect φγ is much smaller than the background b, in addition, the background value can fluctuate depending on the position of the object of study on the seabed. Therefore, we can conclude that the passive registration of gamma quanta of spontaneous radioactive decay does not allow using a prototype device to reliably detect some types of highly shielded fissile substances, for example, highly shielded weapons-grade uranium. Some types of fissile materials, for example, based on plutonium warheads, can be detected by passive detection of gamma radiation from spontaneous radioactive decay, since they have a relatively short half-life [Fetter S., Frolov AV, Miller M. Detecting Nuclear Warheads // Science and Global security, Vol. 1, 1990, pp. 225-302].

The technical result of the proposed proposal is to increase the likelihood of detecting highly shielded weapons-grade uranium in the object of study located on the seabed. At the same time, the utility model, as well as the prototype, makes it possible to detect explosives located on the seabed, poisonous substances, as well as highly emitting fissile materials (for example, plutonium as part of a nuclear warhead) by the passive method.

The technical result is achieved by the fact that a device for detecting explosive, poisonous and fissile substances on the seabed, containing a pulsed neutron deuterium-deuterium generator, scintillation gamma detectors and an amplitude analyzer with a time window for measuring gamma rays of neutron capture, scintillation gamma detectors and a pulsed neutron deuterium-deuterium generator connected to an amplitude analyzer,

scintillation gamma detectors are located in a fluorine-containing substance surrounding the scintillation gamma detectors,

the amplitude analyzer has a time window for measuring gamma quanta of the ¹⁶ N isotope generated by the interaction of fission neutrons emitted during neutron irradiation of the object of study containing fissile matter with a fluorine-containing substance,

moreover, the volume and location of the fluorine-containing substance, as well as the volume and location of scintillation gamma detectors, must be such that the product of the rate of production of the ¹⁶ N isotope in the fluorine-containing substance by fission neutrons and the probability of detecting gamma quanta with an energy of 6.13 MeV coming out of the fluorine-containing substance, scintillation gamma detectors were at least 6.25 / T ₀ , where T ₀ is the detection time.

The essence of the proposed device and its operation is illustrated by drawings.

In FIG. 1 shows a sketch of the claimed device.

In FIG. 2 shows a timing diagram of the operation of the device during operation of a neutron deuterium-deuterium generator in a pulsed mode.

In FIG. 3 shows an example implementation of the inventive device.

In FIG. Figure 4 shows a model of a nuclear warhead in the form of a set of concentric spheres of various materials, where the material, internal and external radii are indicated for each sphere.

The positions in the illustrations indicate:

1 - submarine,

2 - pulsed neutron deuterium-deuterium generator,

3 - scintillation gamma detectors,

4 - fluorine-containing substance,

5 - amplitude analyzer,

6 - object of study,

7 - the seabed,

8 - sea water,

9 is a time window for measuring gamma rays of radiation capture of neutrons,

10 is a time window for measuring gamma rays of the isotope ¹⁶ N.

The device comprises a pulsed neutron deuterium-deuterium generator 2, gamma-ray scintillation detectors 3 located in a fluorine-containing substance 4 surrounding gamma-ray scintillation detectors 3, and an amplitude analyzer 5 with a time window 9 for measuring gamma-rays of radiation capture of neutrons and a time window 10 for measuring gamma rays isotope ¹⁶ N. scintillation gamma detectors 3 and pulsed deuterium-deuterium neutron generator 2 is connected to the amplitude analyzer 5. At the seabed facility 7 is 6 issl inquiry that may contain explosive, poisonous or fissile material. The device is placed on a submarine 1. Submarine 1 and object 6 of the study are separated by a layer of sea water 8.

The device operates as follows.

Submarine 1 with the device located on it approaches the object 6. Using gamma-ray scintillation detectors 3, gamma radiation is measured from object 6 in order to detect fissile substances before the neutron generator 2 is switched on (passive method). After completing the measurement by the passive method, the active method is measured using a pulsed neutron deuterium-deuterium generator 2. A pulsed neutron deuterium-deuterium generator 2 emits 2.5 fast MeV neutrons in the direction of the object 6 of the study. At the time of the start of the emission of a neutron pulse from a pulsed neutron deuterium-deuterium generator 2, a synchronization signal is supplied to the amplitude analyzer 5, which serves to form a time window 9 for measuring gamma rays of neutron capture and a time window 10 for measuring gamma rays of the ¹⁶ N isotope. Passing through sea water 8, neutrons are slowed down to thermal energies, and object 6 of the study is irradiated with thermal neutrons. An explosive substance is characterized by an increased concentration of nitrogen nuclei, a toxic substance is characterized by an increased concentration of sulfur nuclei. Gamma rays with an energy of 10.83 MeV are emitted during the radiation capture of thermal neutrons by nitrogen nuclei; gamma rays with an energy of 5.42 MeV and 3.22 MeV are emitted during radiation capture of thermal neutrons by sulfur nuclei.

A part of the emitted gamma-rays passes through the thickness of sea water 8 to the submarine 1 and enters the scintillation gamma-detectors 3. The signals from the scintillation gamma-detectors 3 are fed to an amplitude analyzer 5, which registers them in a time window 9 for measuring gamma-quanta of radiation capture neutrons, the beginning and end of which corresponds to the maximum signal-to-noise ratio for the measured gamma quanta (tentatively, the beginning is 20 μs after the pulse, the end is 200 μs after the neutron pulse). The amplitude analyzer 5 measures the spectrum of gamma rays, from which it is possible to calculate the count rate of gamma rays with energies of 10.83, 5.42 MeV and 3.22 MeV, on the basis of which it is possible to determine the presence in the object 6 of the study lying on the seabed 7 , explosive or toxic substances.

If fissionable substances are present in object 6 of the study, then neutrons are captured by their forced fission and instantaneous fission neutrons are emitted. A part of the instantaneous neutrons passes through the water column to a fluorine-containing substance 4 surrounding the gamma-ray scintillation detectors 3. When fission neutrons with an energy greater than 4.2 MeV interact with fluorine-containing substance 4, a short-lived (7) reaction is produced as a result of the ¹⁹ F (n, α) ¹⁶ N reaction , 14 c) ¹⁶ N isotope emitting high-energy gamma rays with an energy of 6.13 MeV.

To achieve the maximum probability of detecting fissile substances, the registration of gamma rays with an energy of 6.13 MeV emitted by the ¹⁶ N isotope is necessary in the absence of background radiation. At a great depth (> 10 m), where object 6 of the study is located, there is practically no gamma background due to cosmic radiation. The energy of gamma radiation of isotopes generated by irradiating substances with probing neutrons is less than 3 MeV, so they can be discriminated against from gamma rays with an energy of 6.13 MeV. The source of the background when registering gamma quanta with an energy of 6.13 MeV can be gamma quanta emitted during the radiation capture of thermal neutrons by the nuclei of certain elements (for example, the ³⁵ Cl nucleus contained in seawater 8 emits a gamma quantum with energy of 6.11 MeV). Therefore, the registration of gamma rays with an energy of 6.13 MeV should be performed in the absence of a neutron flux after a certain delay after switching off the pulsed neutron deuterium-deuterium generator 2 (Fig. 2). The duration of the delay is selected so that the probability of detecting the background is significantly less than the probability of detecting ¹⁶ N decay products in the presence of fissile substances in the object 6 of the study. The lifetime of a thermal neutron in pure water is about 0.2 ms (in salt water it is even shorter due to the additional absorption of neutrons by chlorine nuclei). With a delay time of 3 ms, the number of thermal neutrons will decrease by 3.5 • 10 ⁶ times, and with a delay time of 4 ms - by 5 • 10 ⁸ times. The necessary delay is determined by the number of neutrons emitted per 1 pulse of a pulsed neutron deuterium-deuterium generator 2. For example, with a pulse repetition period of 20 ms and an intensity of 2 • 10 ⁸ 1 / s of a pulsed neutron deuterium-deuterium generator 2, 4 • 10 ⁶ neutrons are emitted per pulse . 3 ms after the neutron pulse, almost all neutrons are thermalized and absorbed by chlorine nuclei, and there will be no gamma background. The end of the time window 10 for measuring gamma rays of the ¹⁶ N isotope should occur before the next pulse of the pulsed neutron deuterium-deuterium generator 2.

The timing diagram of the operation of the device during operation of a pulsed neutron deuterium-deuterium generator 2 in a pulsed mode is shown in FIG. 2. The duration of neutron emission τ _{i is} less than the lifetime of a thermal neutron. Gamma rays of radiation capture of neutrons are recorded in time window 9 for measuring gamma rays of radiation capture of neutrons, the beginning of which is τ _d1 , and the end is τ _m1 after the neutron momentum. The ¹⁶ N decay gamma quanta are recorded in a time window 10 for measuring the ¹⁶ N isotope gamma quanta, the beginning of which is τ _d2 , and the end of τm2 must be less than the pulse repetition period of the pulsed neutron deuterium-deuterium generator 2. The values of τ _d1 , τ _m1 and τ _{d2 are} determined by the maximum signal-to-noise ratio for the measured gamma rays. For a pulse repetition period of 20 ms and an intensity of 2 • 10 ⁸ 1 / s of a pulsed neutron deuterium-deuterium generator 2, the approximate values of τ _d1 , τ _m1 , τ _d2 and τ _m2 after the neutron pulse are equal to: τ _d1 = 20 μs, τ _m1 = 200 μs, τ _d2 = 3 ms, τ _m2 = 19.5 ms.

From the analysis of the equation for cyclic activation analysis [Tustansky V.T. Assessment of the accuracy and sensitivity of activation analysis. - M .: Atomizdat, 1976. - 192 С.] it follows that, since the neutron pulse duration τi is much shorter than the pulse repetition period T _i (τ _i << T _i ), delay τ _d2 << T _i , detection time T ₀ >> T _i , we can assume that the number N _{N of} registered gamma rays with an energy of 6.13 MeV from the ¹⁶ N isotope is

(3)

(3)

where ε is the probability of detecting 6.13 MeV gamma quanta leaving the fluorine-containing substance 4 by scintillation gamma-detectors 3, Q _N is the rate of production of the ¹⁶ N isotope in the fluorine-containing substance 4. Calculations of the dependence of ε and the number of registered gamma-quanta with an energy of 6.13 MeV from the volume of scintillation gamma-detectors 3, located at the same distance from the neutron generator and each other, are shown in the Table.

For detection with 99% reliability, it is necessary that

(4)

(4)

where B is the number of background samples. Since the background radiation that can generate a signal in scintillation detectors 3 interfering with the signal from gamma rays with an energy of 6.13 MeV is absent (B = 0), therefore, condition (4) can be written as

(5)

(5)

Thus, it follows from expressions (3) and (5) that the volume and location of the fluorine-containing substance, as well as the volume and location of scintillation gamma detectors, must be such that the product of the rate of production of the ¹⁶ N isotope in the fluorine-containing substance by fission neutrons Q _N and the probability The detection of gamma quanta with an energy of 6.13 MeV coming out of fluorine-containing material 4 by scintillation gamma-detectors 3 was not less than 6.25 / T ₀ , where T ₀ is the detection time.

In FIG. 3 presents a sketch of a model for implementing the inventive device. Pulsed neutron deuterium-deuterium generator type 2 ING-031 manufactured by All-Russian Research Institute of Automation named after N.L. Dukhov provides a neutron flux of 2 • 108 1 / s, pulse duration τ _i = 1 μs, pulse repetition period T _i = 20 ms, irradiation time T ₀ = 400 s. Scintillation gamma detectors 3 are based on BGO crystals with a diameter of 76 mm and a height of 76 mm. Each scintillation gamma-detector 3 is located in a fluorine-containing substance 4 (fluoroplastic) with a volume of 2.1 • 10 ³ cm ³ in the form of a hollow cylinder located coaxially relative to the scintillation gamma-detector 3 and having the same height with it. The end surfaces of the scintillation gamma-ray detector 3, fluorine-containing substance 4 and the pulsed neutron deuterium-deuterium generator 2 are located in the same plane.

Other sizes of scintillation gamma detectors 3, volume of fluorine-containing substance 4 and its geometry relative to scintillation gamma-detectors 3 can be used, for example, fluorine-containing substance 4 can surround the side surfaces and / or end surfaces of scintillation gamma-detectors 3. It can also be another arrangement of the neutron generator 2 relative to the scintillation gamma detectors 3 shown in FIG. In this case, it is necessary that condition (5) is fulfilled - the product of the rate of production of the ¹⁶ N isotope in a fluorine-containing substance by fission neutrons Q _N and the probability of detecting gamma rays with an energy of 6.13 MeV coming out of the fluorine-containing substance 4, scintillation gamma detectors 3 should be not less than 6.25 / T ₀ , where T ₀ is the detection time.

After each neutron pulse of a pulsed neutron deuterium-deuterium generator 2, an amplitude analyzer 5 measures the gamma-ray spectrum in time window 9 to measure gamma-rays of radiation neutron capture, the beginning of which is τ _d1 = 20 μs and the end is τ _m1 = 200 μs after the neutron pulse , and determines the count rate of gamma rays with energies of 10.83, 5.42 MeV and 3.22 MeV for searching explosives or poisons in object 6.

The ¹⁶ N decay gamma quanta are recorded in a time window 10 for measuring the ¹⁶ N isotope gamma quanta, the beginning of which is τ _d2 = 3 ms, and the end of τ _m2 = 20 ms (before the next clock pulse arrives). The object of the study 6, lying on the seabed 7, is a nuclear warhead based on weapons-grade uranium weighing 12 kg with a tungsten piston [Fetter S., Frolov AV, Miller M. Detecting Nuclear Warheads // Science and Global security, Vol. 1, 1990, pp. 225-302]. A model of this nuclear warhead is shown in FIG. 4. The distance between the pulsed neutron generator 2 and the object 6 of the study is 30 cm. Since the range of neutrons in beryllium, uranium, tungsten, trinitrotoluene and aluminum is much greater than the thickness of the spheres of these materials, we can assume that the attenuation of neutrons in these materials does not occur, but object 6 of the study can be represented as a sphere with an outer diameter of 7 cm and an inner diameter of 5.77 cm (Fig. 4).

Using the GEANT program, we carried out a numerical simulation of the processes of transporting neutrons emitted by a pulsed neutron deuterium-deuterium generator 2 to object 6 of the study, forced fission of the uranium sphere in object 6 of the study under the influence of neutrons, the passage of fission neutrons to a fluorine-containing substance 4, and the production of isotopes ¹⁶ N, the output of gamma rays of the ¹⁶ N isotope and their registration with scintillation gamma detectors 3.

With the volume of scintillation gamma detectors 3 equal to 1400 cm ³ , N _N = 6.7, and condition (5) is satisfied. In the case of using scintillation gamma detectors 3 based on BGO crystals with a diameter of 76 mm and a height of 76 mm, four gamma detectors are required for this. Therefore, the proposed device, in comparison with the prototype, has a higher probability of detecting a nuclear warhead in object 6 of the study containing 12 kg of weapons-grade uranium in a tungsten piston, and thus, the claimed result is achieved — increasing the likelihood of detecting highly shielded weapons-grade uranium in the object of study located on the seabed.

Sources of information

1. Sudac D., Matika D. and Valcovic V. Detection of Explosives in Objects on the Bottom of the Sea // Application of Accelerators in Research and Industry, AIP Conf. Proceedings, Vol. 1099, 2009, pp. 574-577.

2. Aleksakhin V.Yu., Bystritsky V.M., Zamyatin N.I. et al. Application of the tagged neutron method for the detection of hazardous substances under water // Collection of reports of the international scientific and technical conference “Portable neutron generators and technologies based on them”. - M.: VNIIIA, 2012. - S. 555-567.

3. Laikin A.I., Grishin D.S., Kyzyurov V.S. et al. Experience in the development of a submersible complex for the identification of explosive, poisonous and radioactive substances in underwater potentially hazardous objects - “Varyag-ChS” // Collection of reports of the international scientific and technical conference “Portable neutron generators and technologies based on them”. - M .: VNIIA, 2012. - S. 525–534.

4. Fetter S., Frolov A.V., Miller M. Detecting Nuclear Warheads // Science and Global security, Vol. 1, 1990, pp. 225-302.

5. Sapozhnikov Yu.A., Aliev R.A., Kalmykov S.N. Radioactivity of the environment. - M .: BINOM, 2006 .-- 286 p.

6. Gusev N.G., Mashkovich V.P., Suvorov A.P. The physical basis of radiation protection. - M .: Atomizdat, 1980 .-- 461 S.

7. Tustansky V.T. Assessment of the accuracy and sensitivity of activation analysis. - M .: Atomizdat, 1976. - 192 S.

Claims (1)

A device for detecting explosive, poisonous and fissile materials on the seabed, containing a pulsed neutron deuterium-deuterium generator, scintillation gamma detectors and an amplitude analyzer with a time window for measuring gamma rays of neutron radiation capture, scintillation gamma detectors and pulsed neutron deuterium-deuterium the generator is connected to an amplitude analyzer, characterized in that the gamma-ray scintillation detectors are placed in a fluorine-containing substance surrounding the scintillation ion gamma detectors, the amplitude analyzer has a time window for measuring gamma quanta of the ¹⁶ N isotope generated by the interaction of fission neutrons emitted during neutron irradiation of a test object containing fissile material with a fluorine-containing substance, the volume and location of the fluorine-containing substance, as well as the volume and the location of the scintillation gamma detectors must be such that the product of rate of use of the isotope ¹⁶ N in the fluorine-containing material and fission neutron detection probability and gamma-rays with an energy of 6.13 MeV, emerging from the fluorine-containing substance, gamma scintillation detector was not less than 6.25 / T _0, where T ₀ - time detection.

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