# The method of calculating the effective intensity of the neutron source nuclear installations

(57) Abstract:

The method for determining the intensity of the neutron source nuclear installation is intended for use in the field of nuclear energy. The method involves measuring the count rate. Last conducted in the presence of a nuclear facility of fissile material. The count rate measured at discrete intervals for at least 1 second before, during and after insertion of the control rods in the installation. The introduction of the rods does not exceed 5 seconds. The total efficiency of the input terminals is greater than 1%. When the total time of measurement of the counting rate of not less than 300 seconds measuring time count rate prior to the introduction of the rods is selected in the range of 10-20 seconds. Improved the safety of nuclear installations. 1 C.p. f-crystals. The invention relates to nuclear reactors physics, namely to ensure the nuclear safety of nuclear reactors and critical assemblies, hereinafter referred to as YAU (nuclear installations), and can be used later in evaluating the main parameters of the subcritical reactor as the effective multiplication factor, reactivity. Under the provision of nuclear safety at work related experimental evaluation values to_{eff}(effective multiplication factor) YAU at each stage of the nuclear-hazardous work, including repairs to shut down the nuclear reactors.Determination of the effective intensity of the neutron source nuclear installation Q

_{eff}regulated by different norms: General provisions for ensuring safety of nuclear stations OPB-88/97, Rules of nuclear safety critical stands NSR-KS-98, rules of the nuclear safety research reactor NSR-IR-98. They involve the definition of Q

_{eff}in the absence YAU fissile material. Further Q

_{eff}used, for example, to determine the reactivity of the reactor (patent RF №2088983, IPC G 21 C 17/00, 1997).There is a method of calculating the effective intensity of the neutron source YAU (Rules of nuclear safety critical stands NSR-CS-98 - prototype), which consists in measuring the count rate of the neutron detector in a stationary state in the absence of in YAU fissile substances and the determination of the effective intensity of the neutron source Q

_{eff}from the formulav(K

_{eff}- the rate of the experimental neutron detector in a stationary state YAU.Measured once this calibration experiment, the value of Q

_{eff}taken as a constant parameter used to estimate K

_{eff}by the formula (1) according to the measurement results v(K

_{eff}) when all changes in the composition and geometry YAU. However, the value of Q

_{eff}may vary by several orders of magnitude due to changes in the composition and YAU geometry, which reduces the reliability of the assessment, and therefore, security YAU.The task of the invention is to improve safety YAU by improving the reliability of measurement values of Q

_{eff}.For this purpose, a method for calculating the effective intensity of the neutron source nuclear installations, namely, that measure the count rate from YAU the neutron detector and calculate the value of the effective intensity of the neutron source nuclear installation Q

_{eff}when this measurement is carried out at present in YAU fissile material with discrete intervals in time at least 1 second before, during and after insertion of control rods in a nuclear facility, the time of the input terminals does not exceed 5 seconds, and the total efficiency of the input terminals is greater than 1%.We will show the possibility of defining Q

_{eff}the specified method.The proposed method for the determination of Q

_{eff}based on the equations of the kinetics of the reactor in the following source code:i=1-6Initial conditions:{dn(t)/dt=0, dC

_{i}(t)/dt=0} if -<t0 after reset terminals. Let us introduce the notation: S(t)=

_{i}C

_{i}(t). Measuring values of the function n(t)/l before, during and after a reset of the control rods, from equations (2-8) with the initial conditions, you can determine the values of the function S(t). If in equation (2) substitute the values of the functions n(t) and S(t) for 2 times after a reset of the control rods, the resulting transformation will result in the following calculation formula Q

_{eff}:where t

_{1}and t

_{2}- any two points in time after reset terminals.The method is as follows.In YAU with fissile substance install a neutron detector for measuring the count rate that corresponds to the dimension of the function n(t)/l in relative units.The neutron sources YAU is the spontaneous fission of fissile substances in the volume YAU; in a stopped reactor sources Nate the intensity of these neutron sources are insufficient, for measuring the count rate of the neutron detector with acceptable error inside YAU or its surface it is necessary to install an additional source of neutrons. The proposed method is measured effective total intensity sources, emitting neutrons in the volume YAU.Key element technical support of measurements Q

_{eff}is the PC associated with the electronic equipment. PC used for configuration, commissioning and calibration of the experimental apparatus for collecting time processing and display of experimental data. In real conditions to ensure the necessary accuracy, it is desirable to use multiple neutron detectors, operating in the pulse mode, which determines and other electronic equipment: amplifiers, discriminatory, registers the piece of the pulse from the output of the amplifiers. The composition of the electronic equipment and the requirements for its characteristics similar to the composition and requirements for equipment used to implement the measurement of Q

_{eff}the method of the prototype.After preparing all the equipment to work, start PC for measurement v(t) electronic equipment for the measurement values of the function n(t)/l be measured at the maximum possible count rate of neutron detectors, and also to use in the experiment system from multiple detectors. Time measurements before the start of the reset terminals of at least 10 seconds, determined by the need to measure the values of the functions n(t)/l with an acceptable error in the steady state YAU. Then hold the reset control rods with a total efficiency of more than 1%, the time reset terminals must not exceed 5 seconds in the initial steady state to the reset terminals effective multiplication factor must be in the following range: 1>

_{eff}>0,95. These practical recommendations related to requirements of the measurement of the difference [v(t

_{1})-v(t

_{2})] in the calculation formula Q

_{eff}with acceptable error.The total measurement time should be not less than 300 seconds, which is determined by the output time YAU on the stationary mode.After that, the above algorithm is the calculation of the Q

_{eff}and the corresponding random error of measurements of Q

_{eff}.Thus, this method allows to determine the effective intensity of the neutron source nuclear installation in the presence of a nuclear substance, which in turn will give the opportunity for each state, YAU know such Osnovnye method prototype. 1. The method for determining the intensity of the neutron source nuclear installations, namely, that measure the rate of nuclear installation of the neutron detector and calculate the effective intensity of the neutron source, characterized in that the measurement of the counting rate are in the presence of a nuclear facility of fissile material, and the count rate measured at discrete intervals of not less than 1 s before, during and after insertion of the control rods in the installation, at the same time, the introduction of the rods does not exceed 5, the total efficiency of the input terminals is greater than 1%.2. The method according to p. 1, characterized in that the total time of the measurement of the counting rate of not less than 300, and the time measurement count rate prior to the introduction of the rods is selected in the range of 10-20 C.

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