RU92969U1 - NEUTRON DETECTOR FOR REGISTRATION OF REACTOR NEUTRON RADIATION - Google Patents

Abstract

 A neutron detector for detecting reactor neutron radiation, comprising a housing with a layer of fissile material deposited on its inner surface, filled with a luminescent gas medium, the luminescent radiation power of which depends linearly on the neutron flux density, one of the ends of the optical fiber is inserted through the end of the body, the other end of the fiber connected by means of a photodetector equipped with a filter with a recording system for measuring the power of luminescent radiation, characterized we note that an additional channel is organized up to the photodetector by means of a fiber optic splitter for recording the scintillation count rate in a gaseous medium, which is formed by a branch of the optical fiber connected via an additional photodetector to its own filter with a recording system, which allows scintillations in the gas to be counted from fission fragments obtained by the interaction of individual neutrons with a layer of fissile material.

Description

The utility model relates to the detection of neutron radiation and can be used in nuclear physics, nuclear energy, in particular, in systems for monitoring and ensuring the safety of nuclear power reactors.

Due to the need to work in a reactor, the detector must satisfy one of the basic requirements — operation directly from the neutron flux density [1. Ionaitis P.P. Unconventional controls for nuclear reactors. - M.: Publishing House of MSTU. N.E.Bauman, 1992.]. In this case, the neutron detector must have low sensitivity to the level of gamma-ray background and high electronic stability.

Known nuclear optical transducer (NOP), which is a neutron radiation detector, the principle of which is to directly convert the kinetic energy of nuclear particles (for example, uranium fission fragments) into luminescent radiation recorded using photoelectron multipliers (PMTs) [2. Baldin S.A., Matveev V.V. Gas scintillation counters. PTE, No. 4, 1963, pp. 5-18]. The detector is made in the form of a casing filled with a gas luminescent medium with a sample of fissile material, and is equipped with two PMTs installed at both ends of the casing.

The disadvantage of such detectors is that they are sensitive to the gamma radiation of the reactor and their placement in the reactor is associated with the need to use high voltage supplied to the PMT.

Known neutron detector (certificate for utility model No. 30008, publ. 10.06.2003), including a housing filled with a luminescent gas medium, the luminescent radiation power of which depends linearly on the neutron flux density. A layer of fissile material is deposited on the inner side surface of the housing. One of the ends of the fiber is inserted through the end of the housing, while the other end of the fiber is connected via a photodetector to a filter with a recording system for measuring the power of luminescent radiation.

The disadvantage of the detector is that it can be used to record neutron flux densities only in the range 10 ⁶ -10 ^l7 cm ^-2 s ^-l , limited by the capabilities of the recording equipment.

The last technical solution as the closest in physical and technical nature is selected as a prototype.

The task to be solved is to control the magnitude of the neutron flux density, along with the operating and emergency modes, and in the starting mode of the reactor.

The technical result achieved by the implementation of the utility model is to expand the detection range of reactor neutron radiation by providing the possibility of detecting the neutron flux density up to 10 ⁶ cm ^-2 · s ^-1 , which allows the detector to be used not only in operating and emergency conditions corresponding to flux densities neutrons in the range of 10 ⁶ -10 ¹⁷ cm ^-2 · s ^-1 , but also in the starting mode.

The technical result is achieved by the fact that, in contrast to the known neutron detector for detecting reactor neutron radiation, including a housing with a layer of fissile material deposited on its inner surface, filled with a luminescent gas medium, the luminescent radiation power of which linearly depends on the neutron flux density, through the end face one of the ends of the fiber is introduced, the second end of the fiber is connected by means of a photodetector equipped with a filter with a recording system For measuring the luminescent radiation power, an additional channel is organized in the proposed detector to the photodetector by means of a fiber optic splitter for recording the scintillation count rate in a gaseous medium. gas from fission fragments obtained by the interaction of individual neutrons with a layer of fissile Container material.

The use of fissile material in the form of a thin layer deposited on the inner surface of the casing and the transmission of an optical signal by means of an noise-protected fiber-optic channel for transmitting information from the irradiation zone for the biological protection of the reactor, where the background of the nuclear radiation corresponds to the natural one, eliminates the influence of negative factors associated with operation directly in the reactor zone, namely: the effect of gamma background and electrical interference on the detector output signal. At the same time, the ability of the neutron detector to control, in addition to the neutron flux density in the range 10 ⁶ -10 ¹⁷ cm ^-2 · s ^-1 , the neutron flux density in the range up to 10 ⁶ cm ^-2 · s ^-1 , is ensured by the organization of another recording channel with an additional 4yutonriemnikom with proper filter selection and the recording apparatus which provides the possibility scintillation counting gas from fission fragments obtained by reacting the individual neutron flux level pa 1-10 ⁶ cm ^-2 · s ^-1 with a thin layer of fissile material on the inner s surface of the detector housing.

In FIG. schematically presents the claimed utility model, where

1 - detector housing; 2 - a layer of fissile material (source of fission fragments); 3 - luminescent gas medium; 4, 6 - fiber optic fiber; 5 - fiber optic splitter; 7, 10 - filters, respectively, of the first and second (additional) registration channels; 8, 11 - photodetectors of the first and second recording channels; 9 - a wide-range recording system for measuring the power of luminescent radiation; 12 is a recording system that provides the ability to count scintillations.

The proposed neutron detector is made in the form of a housing 1 filled with a luminescent gas medium 3, on the inner side surface of which a layer of fissile material is deposited 2. A fiber optic cable 4 is inserted through one end into the end face of the detector housing 1 and connected to the fiber optic splitter 5 with the other end. which divides the fiber into two branches - optical fibers 6 and 6 ', leading light radiation to the two registration channels. One of the optical fibers 6 is connected to a recording system 9 for measuring the luminescent radiation power through a photodetector 8 with a filter 7 (first recording channel), and the second optical fiber 6 'is connected via an additional photodetector 11 with its own filter 10 with a recording system 12 for measuring the count rate scintillation in a gaseous medium (additional recording channel). As a luminescent gas medium, for example, a binary mixture of noble gases He-Kr is used.

The neutron detector operates as follows. Under the influence of the neutron flux of the reactor, fissile material 2, deposited in a layer on the inner surface of the housing 1 of the neutron detector, emits fission fragments that excite the gaseous medium 3, which leads to its luminescence. Luminescent radiation enters the input end of the fiber 4 and is transported to a fiber optic splitter 5, where it is divided into two channels 6 and 6 ', but one of which 6 receives radiation from a photodetector 8 with a filter 7, the signal from which is processed by the recording system 9 for measurement power of the luminescent radiation, and according to the second 6 ', the radiation enters the photodetector 11 with a filter 10, the signal from which is processed by the recording system 12 to measure the count rate of scintillations in a gaseous medium.

When the neutron flux density is from 1 to 10 ⁶ cm ^-2 · s ^-1, registration is carried out by a recording system 12 for measuring the count rate of scintillations in a gaseous medium. At higher neutron flux densities, registration is carried out by a recording system 9 for measuring the power of luminescent radiation.

The tests of the claimed utility model have confirmed the possibility of its use for neutron registration in a wide range of neutron flux densities from 1 cm ^-2 · s ^-1 to 10 ¹⁷ cm ^-2 · s ^-1

The results obtained give reason to believe that there is a real possibility for the formation of reactor control signals in all modes of its operation. Due to this, the proposed neutron detector will be widely used in monitoring systems and ensuring the safety of nuclear power reactors.

Claims (1)

A neutron detector for detecting reactor neutron radiation, comprising a housing with a layer of fissile material deposited on its inner surface, filled with a luminescent gas medium, the luminescent radiation power of which depends linearly on the neutron flux density, one of the ends of the optical fiber is inserted through the end of the body, the other end of the fiber connected by means of a photodetector equipped with a filter with a recording system for measuring the power of luminescent radiation, characterized we note that an additional channel is organized up to the photodetector by means of a fiber optic splitter for recording the scintillation count rate in a gaseous medium, which is formed by a branch of the optical fiber connected via an additional photodetector to its own filter with a recording system, which allows scintillations in the gas to be counted from fission fragments obtained by the interaction of individual neutrons with a layer of fissile material.