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 toeff(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 Qeffregulated 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 Qeffin the absence YAU fissile material. Further Qeffused, 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 Qefffrom the formula

v(Keff- the rate of the experimental neutron detector in a stationary state YAU.

Measured once this calibration experiment, the value of Qefftaken as a constant parameter used to estimate Keffby the formula (1) according to the measurement results v(Keff) when all changes in the composition and geometry YAU. However, the value of Qeffmay 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 Qeff.

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 Qeffwhen 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 Qeffthe specified method.

The proposed method for the determination of Qeffbased on the equations of the kinetics of the reactor in the following source code:

i=1-6

Initial conditions:

{dn(t)/dt=0, dCi(t)/dt=0} if -<t0 after reset terminals. Let us introduce the notation: S(t)=iCi(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 Qeff:

where t1and t2- 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 Qeffis 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 Qeffthe 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(t1)-v(t2)] in the calculation formula Qeffwith 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 Qeffand the corresponding random error of measurements of Qeff.

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.

 

Same patents:

The invention relates to the field of physics and technology of reactors, and more particularly to methods of control and security subcritical assemblies

Digital realtimer // 2195029
The invention relates to operational control of the reactivity of a nuclear reactor under a wide range of change of neutron flux

The invention relates to nuclear engineering, namely to control the status of the nuclear reactor water coolant and moderator at the start

FIELD: monitoring safety characteristics and variables of nuclear power units at nuclear power stations.

SUBSTANCE: proposed method that can be used, for instance, to adjust reactimeters of nuclear power stations with type RBMK-1000 and incorporates provision for reducing systematic measurement error by two orders of magnitude includes introduction of sets of variables characterizing correlation between fissionable elements of fuel and desired burn-up step in charge-coupled device module of reactimeter; determination of current value of mean fuel burn-up using data of centralized checkup system of reactor unit; and selection of respective mentioned variables by varying position of switch on rear panel of reactimeter. Use is made of sets of variables αi (fractions of i group delayed neutrons in delayed neutron generation responsible for total composition of fissionable isotopes of desired burn-up fuel) and sets of variables λeff (effective constants of i group delayed neutrons). Reactimeter adjustment scale is calibrated in terms of mean fuel burn-up in reactor core.

EFFECT: enhanced measurement accuracy, and nuclear safety, facilitated adjustment to current state of reactor by composition of fissionable elements of fuel.

2 cl 3 tbl

FIELD: analog-digital computing technique, possibly testing devices (reactimeters) for measuring reactivity of nuclear reactors.

SUBSTANCE: apparatus includes digital-to-analog converter, measuring amplifier, set of N connected in series circuits of resistors for forming output electric current and electronic switching circuits, program control unit.

EFFECT: enlarged functional possibilities of apparatus due to simulating reactivity of different types of nuclear reactors with different fuel compositions, lowered time period for preparing reactor to operation at changing operation modes, reduced error of setting far-field reactivity.

6 dwg

FIELD: measuring reactivity of neutron-multiplying medium.

SUBSTANCE: proposed method includes installation of neutron source into neutron-multiplying medium, measurement of total number of neutrons as count rate of neutron counter within multiplying medium upon setting steady state as well as count rate in absence of neutron source, whereupon reactivity of neutron-multiplying medium is found from relevant formula; novelty is use of pulsed neutron source for the purpose where pulse repetition rate of neutrons is over 10 Hz; measurement of average rate of count with pulsed neutron source turned on and rate of count n1 with pulsed neutron source turned off upon connection of pulsed neutron source and setting of steady in average state of neutron multiplying medium; then reactivity is evaluated for each ON-OFF cycle using formula Measurement cycle of and n1 lasts 1 - 11 s. Rate of count is measured with pulsed neutron source turned on and off in steps of 0.1 to 1 s.

EFFECT: reduced error and enlarged reactivity measurement range at reduced time and labor consumption.

4 cl, 3 dwg

FIELD: analog-digital computer engineering; reactivity measurement device verification and on-the-fly check of its operability.

SUBSTANCE: proposed method includes forming of first data array which corresponds to changes of reactor's power parameter for a given reactivity, normalization to a given number of decades of the first data array, saving in the storage device of the second data array which is derived from normalization, with the first K decades of power parameter changes being used when forming the data arrays. By values of the second array control action is formed. Forming is executed one time by values of first K decades and N-K times by values of Kth decade, with simultaneously changing level of controlling voltage and impedance value of current-generating resistor-imitator in the end of decades - first in the end of each of the first K-1 decades and then in the end of Kth decade in the quantity of N-K+1, where K depends on the value of modeled reactivity.

EFFECT: decreased storage capacity in simulator program control unit.

6 dwg, 2 tbl

FIELD: experimental evaluation of nuclear reactor physical characteristics and estimating its effective multiplication factor and reactivity.

SUBSTANCE: proposed method includes displacement of absorption rods or other disturbance source in reactor core, determination of neutron field response to these displacements by means of neutron detector, and gamma-ray intensity measurements. Effectiveness of neutron source intensity is found from equation Qef(t)=kλλd(t), where λd(t), is gamma-ray intensity; kλ is factor found in calibration experiment. This procedure needs no periodic repetition of displacing control rods affording reliable shutdown of reactor. Fission chambers are used as neutron and gamma-ray detectors. Gamma-ray intensity is measured by changing over fission chamber using integral current recording circuit.

EFFECT: enhanced reliability of measurement results, reduced amount of work involving handling of radioactive materials.

3 cl

FIELD: physics.

SUBSTANCE: invention relates to physics of nuclear reactors and namely to provision of nuclear safety at operation of nuclear power plants (NPP) - nuclear reactors and NPP critical assemblies. Method for subcriticality determination of NPP stopped without transfer into emergency condition lies in measurement of counting rate v(t) in time from NPP by neutron detectors before, during and after disturbance introduction into neutron current emitted by NPP and in calculation of NPP subcriticality. Count number (T1ST2) of each neutron detector is measured within range of (T1÷T2), where T1 is end time of disturbance introduction into neutron current and T2 is end time of counting rate measurements. Average counting rates v(0) are measured for each neutron detectors at NPP initial stationary condition and v(T2) NPP final stationary condition. By measured values v(0) and v(T2) for each detector counting rate v(t) and number groups of counts (T1CT2)j are calculated by point kinetics equation in range (T1÷T2) at variation of effective multiplication factor k0j in initial NPP condition in range from 0.99 up to 0.95. Subcriticality is determined through the unknown keff=k0j, at which (T1CT2)j has minimum deviation of T1ST2.

EFFECT: provision of subcriticality evaluation in all modes of stopped NPP, reliability enhancement of subcriticality evaluation and increase of NPP safety.

8 cl, 6 dwg

FIELD: nuclear physics.

SUBSTANCE: invention is related to methods for monitoring of nuclear reactors. Invention makes it possible to define efficient multiplication factor keff in the range from 0.95 to 0.99 without performance of preliminary experiments on measurement of efficient intensity of neutron source, Qeff. For this purpose flow of neutrons n(t) is measured, radiated by water-water powder reactor (VVER) as velocities of neutron detector count v(t) in initial stationary condition and in case of VVER power increase by reduction of boric acid concentration C(t), reduction of C(t) is measured in time with interval of discrecity of Δ = 1 second, number of neutron detector counts St is measured for the time T, efficient multiplication factor is calculated by the following formula: keff(t) = k0j + Δk(C(t)), where: k0j - efficient multiplication factor in initial stationary condition, Δk(C(t)) - dependence of efficient multiplication factor increment from concentration of boric acid. Knowing v(0) and keff(t), equations of point kinetics are used to produce sought for value of efficient multiplication factor in zero moment of time by means of simple calculations.

EFFECT: reduction of labour intensiveness of works in process of reactors operation.

4 cl, 3 dwg

FIELD: engines and pumps.

SUBSTANCE: invention can be used when operating nuclear reactors and critical assemblies (nuclear plant (NP)). There proposed is the method of determining reactivity ρ(t), at which the flow of neutrons n(t) radiated with NP is measured as the count rate of neutron detectors and ρ(t) of NP is calculated. At that, increase of reactivity is performed in cycles as per "step-pause" type. Values of the current time of the cycle pause are measured. By setting a number of values of effective K-factor keff within 0.95 to 0.99, by using point-wise kinetics equations, as per the measurement results there calculated are values of effective intensity of neutron source Qeff. Then ρ(t) functions values are calculated, and the value at which reactivity values classified by time period of each pause have minimum deviation as to absolute value from constant reactivity value ρ during that pause is taken as the desired value of a number of running values. Reactivity increase is performed for example by changing the position of NP control rods.

EFFECT: decreasing labour input of determining NP reactivity in order to ensure nuclear safety.

5 cl, 7 dwg

FIELD: nuclear physics.

SUBSTANCE: invention relates to the physics of nuclear reactors and can be applied for the experimentally estimated determination of the efficiency coefficient (keff) of the fast-fission of the active zones of the nuclear plant (NP); the neutron flux n(t) in the NP as a signal of the neutron detector vi(t) with the discrete interval Δt is measured before, during and after the disturbance introduction in the NP; the dependency of the signal from the time v(t) is also determined; a number of values of the fast-fission efficiency coefficient (keff0)j in the initial condition of the NP is set up within the range of approximate values of 0.9000 - 0.9990 before introduction of the disturbance and using the inversed multiplication formula and the relation of the point-source kinetics or the formula of dependency for the approximation of keff(t), (keff1)j is determined in its final condition and (keff(t))j is correspondently determined during the disturbance of the neutron flux; the estimated dependency of the detector signal vpj(t) is computed and on the basis of comparison of the measured and the estimated dependency v(t) the NP keff is determined, at that the impulse or current detector signal is used and on the basis of the average quadratic deviation criterion Δvj is determined within the time interval (t3, t2) after the introduction of the disturbance of the neutron flux the target value of keff0 as (keff0)j correspondent to the minimal Δvj value.

EFFECT: enhancement of the functional possibilities of the method due to application of the impulsive and current measuring devices channels and enhancement of the accuracy and reliability of the keff determination.

35 cl, 3 dwg

FIELD: physics.

SUBSTANCE: in the method of measuring neutron power of a nuclear reactor in absolute units F=V·γ, where V is the reactor power value in arbitrary units, γ is a coefficient of proportionality, neutron power of the nuclear reactor in arbitrary units is measured as the average count rate of the neutron detector in a stationary critical state using measurement means. The coefficient of proportionality is calculated using an autocorrelation function value. The means of measuring the number of neutrons used is an ionisation chamber for determining fluctuation of the number of neutrons. The method includes separately measuring the average value of current of the ionisation chamber and the fluctuating component of the current of the ionisation chamber continuously over time with a discrete interval, calculating the autocorrelation function of the fluctuating current of the ionisation chamber and then calculating the coefficient of proportionality.

EFFECT: increasing the maximum values of F.

3 cl, 1 dwg, 1 tbl

Up!