Creation of a working standard of thermal neutron flux density based on the F-1 reactor

Garapov, E.F.; Inikhov, A. G.; Kucheryavenko, E. P.; Lomakin, S. S.; Panfilov, G. G.; Petrov, V. I.; Khmyzov, V. V.; Yaritsyna, I. A.

doi:10.1007/bf01118854

At Energy

1977

DOI: 10.1007/bf01118854

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Creation of a working standard of thermal neutron flux density based on the F-1 reactor

E.F. Garapov¹,

A. G. Inikhov²,

E. P. Kucheryavenko³

et al.

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Cited by 6 publications

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“…The fuel elements contained an erbium absorber in 0.41 mass% UO 2 (the density of Er 2 O 3 is 8.6 g/ cm 3 ). The 235 U entrichment was 2.6 mass%, and the uranium dioxide density in the pellets of the fuel elements was 10.4-10.5 g/cm 3 .…”

mentioning

confidence: 99%

“…As a rule, such detectors are calibrated according to the sensitivity to neutrons, which is insufficient for solving certain scientific-technical problems [2][3][4]. Specifically, to determine the power release in a reactor core it is necessary to calibrate in-reactor detectors, for example, direct-charge detectors [5], according to the sensitivity not only to neutrons but also to the fission rate of 235 U per 1 g U [6].…”

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Research-reactor neutron fields for calibrating in-reactor detectors in nuclear power plants

et al. 2006

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The neutron spectra of research and power reactors are compared. The spectra were measured by the neutron-activation method and calculated using the KASKAD computer code. The a priori spectrum in the calculation was constructed as a superposition of physically validated spectra. A method of calibrating in-reactor detectors in nuclear power plants on the basis of the sensitivity to the 235 U fission rate in 1 g of uranium using the neutron fields of research reactors is proposed.The use of the neutron fields of research reactors for calibrating the detectors in the standard apparatus of high-power nuclear reactors has been described in [1]. As a rule, such detectors are calibrated according to the sensitivity to neutrons, which is insufficient for solving certain scientific-technical problems [2][3][4]. Specifically, to determine the power release in a reactor core it is necessary to calibrate in-reactor detectors, for example, direct-charge detectors [5], according to the sensitivity not only to neutrons but also to the fission rate of 235 U per 1 g U [6].The objective of the present work is to compare the 235 U fission rate in the neutron fields of research reactors and the RBMK-1000 power reactor and to investigate the dependence of this rate on the ratio of the thermal and epithermal neutrons in the spectra of the reactors studied. For this, the spectra of neutrons in the cores of seven research reactors and two RBMK-1000 channel reactors in the No. 2 unit of the Leningrad nuclear power plant were investigated.Neutron Field of the Kvant Critical Stand [2]. The 1410 mm in diameter and 500 mm high core in this stand consists of 175 fuel assemblies, placed in a water moderator. Ninety four compensation and absorbing rods are placed along the perimeter; a vertical IK-6 experimental channel with inner diameter 85 mm and wall thickness 3 mm is placed near the steel vessel of the stand. The neutron spectrum in the IK-6 channel was measured at the level of the center of the core of the critical stand at power 1 kW.Neutron Field of the F-1 Reactor [1, 3]. The spherical core of the F-1 graphite reator is 6 m in diameter and is surrounded by a 1 m thick graphite reflector. It is assembled from graphite blocks into which are inserted 35 mm in diameter and 100 mm high metal cylindrical blocks of natural uranium. The total uranium mass in the reactor is 48 tons and the graphite mass is 430 tons. The neutron spectrum was measured at core center in the horizontal central experimental channel at reactor power 24 kW.

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Research-reactor neutron fields for calibrating in-reactor detectors in nuclear power plants

et al. 2006

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“…However, it is impossible to determine the neutron sensitivity of the ionization chambers in the primary standard. Together with the primary standard, in accordance with the state calibration scheme [2] a secondary standard of the unit of measurement of thermal-neutron flux density was developed on the basis of the F-1 reactor [3]. The thermal-neutron flux density Φ th with energy below the cadmium limit and temperature T n at different locations of the reactor are presented in Table 1.…”

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Standard neutron source based on the F-1 reactor and standard calibration facility – effective tool for determining the sensitivity of gas-filled ionization chambers

Chuklyaev¹,

Vorontsov

Dikarev

et al. 2009

At Energy

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The F-1 reactor is a controlled uranium-graphite assembly equipped with horizontal and vertical channels, a thermal column, and a "cold assembly." The diameter of the open vertical channel is 89 mm. The channel passes along the central axis of the graphite insert in a well with dimensions 600 × 600 mm, set into the core at a depth of 1 m. The flux density of the thermal neutrons in the reactor channels lies in the interval 1·10 9 -6·10 13 sec -1 ·m -2 .It is shown for the first time on the basis of a standard source that the dose rate of the accompanying photon radiation in the reactor channel is described by a linear function of the reactor power or the neutron flux density.Standard Source of Thermal Neutrons. A state primary standard of thermal-neutron flux was created in the 1980s at the Mendeleev All-Union Research Institute for Metrology [1]. However, it is impossible to determine the neutron sensitivity of the ionization chambers in the primary standard. Together with the primary standard, in accordance with the state calibration scheme [2] a secondary standard of the unit of measurement of thermal-neutron flux density was developed on the basis of the F-1 reactor [3]. The thermal-neutron flux density Φ th with energy below the cadmium limit and temperature T n at different locations of the reactor are presented in Table 1. The error in determining the neutron flux density does not exceed 2% with confidence probability 0.99. The spectral density of the intermediate neutrons at the center of the core of the F-1 reactor is described by the function E -(0.965±0.01) , where E is the energy of the neutrons. The fraction of the intermediate neutrons in the full flux is 0.066. In the vertical channel, the spectral density of the intermediate neutrons varies as E -(0.995±0.01) , the fraction of the intermediate neutrons is 0.036. The error in determining the fraction is 0.003 arb. units.The spatial distribution of the flux density of the thermal neutrons over the height of the irradiation cavity of the vertical channel, shown in Fig. 1, is normalized to the neutron flux at a point 20 cm from the bottom of the channel. The yearly certification over a period of 25 yr attests to the high stability of the neutron source based on the F-1 reactor.Standard Calibration Facility. Together with the standard source of neutrons in the F-1 reactor, a radiometric facility, containing a set of certified gas-filled KNT and KNK ionization chambers, a power supply, and an electric current meter, was developed. The chambers were calibrated in the air cavity of the vertical channel at fixed reactor power. The error in determining the sensitivity to thermal neutrons K n is 3.5% with confidence probability 0.95 (Table 2). The unit of neutron flux is transferred by the substitution method. The flux of thermal neutrons in the channel is proportional to the reactor power and the indications of the fission chamber.

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“…The OI-T thermal neutron master sources based on the VVR-M reactor at the Institute of Nuclear Research of the Ukrainian Academy of Sciences [19], the F-1 reactor at the Kurchatov institute Russian Scientific Center [20], and the BIR-2 reactor are used to obtain isotopes, neutron activation analysis of the composition of materials, calibration of primary neutron flux converters and measuring apparatus. The OI-T sources of the BIR-2 reactor [11] contain two identical graphite cubes with 1.4 m edges equipped with cavities to take detectors and investigated samples.…”

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Metrological support of neutron measurements in Russia

Sevast'yanov¹,

Chuklyaev²

1995

At Energy

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The solution of scientific and technical problems in nuclear physics, biology, solid-state physics, and nuclear technology depends on the accuracy of measuring neutron fluxes and the energy spectrum of radiation.A description is now given of a metrological scheme for the reproducibility of units and it is shown that it is preferable to use master (reference) neutron sources based on nuclear reactors and neutron generators when measuring flux densities of fast neutrons in the range 1 The primary State standard with its checking scheme is mainly used for the purposes of dosimetry and radiation safety. The inventory of service measuring instruments includes a wide spectrum of radionuclide sources and radiometers with different sensitivities, in a broad interval of neutron energies. The main load falls on the master measuring instruments, and this makes it necessary when performing successive transfer to maintain high-quality metrological characteristics of the primary and working standards. A high accuracy of the primary standard makes it possible to certify working measuring instruments with an accuracy of 12-30%.The special State standard is mainly directed at metrological support of neutron measurements in steady-state, quasisteady-state, and pulsed radiation fields of nuclear reactors, accelerators, and other nuclear physics devices which are sources of neutrons. The radiation fields of nuclear physics devices are characterized by a neutron flux density in the range from 105 to 2 • 1019 s -1 "cm -2, a spectral variety in the range from thermal energies to 20 MeV, and the presence of background radiation.Working measurements made on nuclear physics devices include determining the flux (fluence), flux density, and spectral characteristics of the neutron radiation field at the investigated points. A feature of the measurements is that the solution of many scientific and technical problems requires an accuracy close to the maximum attainable with the present-day state of development of science in measurement technique. There is almost no accuracy margin between the standard and working measuring instruments. This approach makes it impossible to implement metrological support based on the principle of the successive transfer of unit sizes. Metrological support of neutron measurements in the radiation fields of nuclear physics devices is therefore based on the principle of directly creating working standards and master

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Creation of a working standard of thermal neutron flux density based on the F-1 reactor

Cited by 6 publications

References 0 publications

Research-reactor neutron fields for calibrating in-reactor detectors in nuclear power plants

Research-reactor neutron fields for calibrating in-reactor detectors in nuclear power plants

Standard neutron source based on the F-1 reactor and standard calibration facility – effective tool for determining the sensitivity of gas-filled ionization chambers

Metrological support of neutron measurements in Russia

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