RU1003659C - Detector of current density of directed neutron radiation - Google Patents

Description

The proposed invention relates to the field of registration of the neutron radiation flux density, and more specifically to the field of registration of high neutron radiation flux densities. The invention can be most effectively used to measure the time dependence of the neutron flux density of nuclear reactors (NR).

And: a detector of direct charge of SCF is known), the principle of which is based on the charging of ft particles, resulting from the decay of radiator material activated by neutrons fMiep, to the signal electrode.

Significant disadvantages of the SCR are the low temporal resolution, about 10% of the constant decay of the activated substance of the radiator, and the high y-radiation signal in the NR radiation field with a dose ratio of H1 radiation and neutron flux of 2.5 10 p cm n

It is also known a device for detecting neutrons, containing an aluminum collector and a hydrogen-containing radiator with a conductive shielding coating of a substance with a low atomic number, separated by a vacuum gap.

The device operates on the principle of transfer of charge of protons of recoil, arising in the field of radiation of neutrons in the matter of the radiator, to the collector.

A disadvantage of the known construction is that, when learning, a hydrogen-containing substance decomposes, it gasses a vacuum gap. As a result, the device must be constantly vacuumed.

The closest in technical essence to the present invention is a detector of the flux density of directional neutron radiation, containing a metal collector enclosed in a metal case, which is separated from the case by two dielectric layers, one of which is made of hydrogen-containing material and the other is made of material that does not contain hydrogen atoms. .

The detector consists of a housing and a collector made in the form of metal plates separated by two layers of dielectric, the housing and the collector made of low-metal (for example, aluminum), one dielectric layer is made of hydrogen-containing material (for example, polyethylene), and the other - from a material that does not contain hydrogen atoms (for example, fluoroplastic) with an effective atomic number not exceeding the atomic number of the material of the hull and collector.

The detector works on the principle of transfer of charge proton recoil in hydrogen-generating dielectric, /

A significant disadvantage of the DDA design is the accumulation of bulk / charge in a hydrogen-containing dielectric.

near the interface with a non-hydrogen-containing substance, resulting from the transfer of recoil protons, and in the entire volume of the dielectric due to the weakening of the neutron flux in the material of the scatterer.

The volume charge distributed inside the hydrogen-containing dielectric creates an electric field, which, along with the high radiation conductivity of the dielectric, leads to resorption of the volume charge, i.e. to the occurrence of the conduction current of the dielectric. The conduction current, combined with the current of the recoil protons, leads to an error in measuring the current of the recoil protons and the circuit

collector.

The purpose of the present invention is to improve the accuracy of measurements of the flux density of directional radiation of neutrons using DDA.

The goal is achieved by the fact that in a device for detecting the flux of directional neutron radiation, which contains a collector enclosed in a metal case, which is separated from the case by two dielectric layers, one of which is made of hydrogen-containing material and the other is non-hydrogen-containing material, hydrogen-containing dielectric is made in the form of two

plates separated by a conductive shielding film of a material with a low atomic number, with a thickness much less than the average weighted projection of the path length of the return ducts in the material of the screen film to the direction of propagation of neutrons, moreover, the thickness of the hydrogen-containing dielectric located between the screen film and the projection path length recoil on the direction of neutron propagation in a given dielectric.

Such a constructive implementation of the detector flux directional

neutron radiation provides an expansion of the range and accuracy of measurements of the time dependence of the neutron flux density while maintaining a simple detector assembly technology due to the screening effect of a significant part of the volume charge arising in a hydrogen-containing dielectric near the interface with a non-hydrogen-containing substance during the transfer of recoil protons in a hydrogen-containing dielectric, the value of conduction current in the collector circuit. The volume charge arising in the water-containing scatterer located between the cathode and the shielding film, near the interface with the non-hydrogen containing substance of the shielding film, when transferring recoil protons towards the collector, is largely compensated by the charge of recoil protons transferred from the distal dielectric located between the distal body and the distance between the reflector and the reflector. and the housing, through the shielding film into the hydrogen-containing dielectric. located between the collector and the shielding film.

The drawing shows an example of the KOHKpet implementation of the device, its general view.

The detector of the flux of directional radiation of neutrons consists of a collector t and a conductive screening film 2 made of a low-atomic metal (for example, aluminum) and separated from each other and a metal case 3 by three layers of dielectric, with dielectric 4 being located between the screening film 2 and the case 3, and the dielectric 5. located between the shielding Ilenka 2 and the collector 1. are made of hydrogen-containing material (for example, polyethylene). and dielectric 6. separating collector 1 and housing 3. - from a material that does not contain atomic hydrogen, with an effective atomic number not exceeding the atomic number of the material of the housing, collector and shielding film (for example; fluoroplastic).

The device works as follows. Upon neutron irradiation from the side of the hydrogen-containing dielectric 4, the charge transfer of the recoil protons to the collector 8 of hydrogen-containing dielectrics 4.5 occurs. The transfer of charge between the housing 3 and the shielding film 2 in the hydrogen-containing dielectric 4. As well as the variable volume charge of the dielectric 4 is not

create electric current in the collector 1 circuit, the current in the collector circuit is due to directional movement of the ducts that occur in the hydrogen content of the dielectric 5. and protons produced in the dielectric 4 and transferred through the shielding film 2 to the dielectric 5. In this connection, the total shielding film 2 must be less than the weighted average projection

These are the free paths of recoil protons in the material of the film, for example, for the distribution of neutrons over the energies of the NR and the aluminum film. Its thickness should be less than 10 mm. The thickness of the hydrogen5 containing dielectric 41a irai is less than the weighted average projection of the protons running on the direction of neutron propagation (for polyethylene and the distribution of neutrons by energy 0 m at YAR this value is 0.1-0.4 mm).

The thickness of the dielectric 5 is selected for considerations of the electrical capacitance of the detector, sensitivity to y-quanta, etc. The volume charge that occurs in a hydrogen-containing dielectric 5 near the interface with the shielding film 2 due to the transfer of protons to the collector is largely compensated (the degree of compensation depends on the thickness

0 of the shielding film 2) by the transfer of recoil protons from the dielectric 4 through the shielding film 2.

The proposed device for recording the flux of the directional radiation of neutron radiation in comparison with the best samples of similar equipment allows, while maintaining the relatively simple technology of detector production, to increase the measurement accuracy of the variable dependence of the neutron flux density by a factor of 3-5.

Performing a device for detecting the flux of directional radiation of neutrons in the manner described above.

5 provides a satisfactory accuracy of the detector readings near the YAR core in the time interval corresponding to 95% of the neutron function.

0 (S6) Abramov A.I. Fundamentals of experimental methods of nuclear physics. M. Atomizdat, 1977, p. 507.

. USSR author's certificate Kfe 713293. cl. G 01 T 3/00. 1979,

Formula and 3 turns

DETECTOR OF DENSITY OF THE FLOW OF DIRECTED RADIATION OF NEUTRONS, holding a metal collector enclosed in a metal case, separated from the case by two layers of dielectric, one of which you are POLY0Nm of hydrogen-containing material and the other is made of matter that does not contain hydrogen atoms, differs from 11S11-nl. the purpose of increasing the accuracy of measurements of the flux density of the directional radiation of neutrons, the water | dielectric containing dielectric was made

in the form of two plates separated by a conductive shielding film of a material with a low atomic number, thickness,

5 much lower than the average weighted projection of the mean free path of the recoil protons in the material of the shielding film to the direction of neutron propagation, moreover, the thickness of the hydrogen-containing electrik; located between the shielding film and the body, not less than the weighted average length of the projection of the recoil protons on the direction of neutron propagation in this daolectrics.