Improved reactor core power distribution measuring method based on instantaneous gamma response correction
阅读说明：本技术 一种基于瞬时伽马响应修正的改进堆芯功率分布的测量方法 (Improved reactor core power distribution measuring method based on instantaneous gamma response correction ) 是由 毕光文 汤春桃 杨波 施建锋 费敬然 张宏博 彭良辉 杨伟焱 秦玉龙 杜炳 于 2018-11-02 设计创作，主要内容包括：一种基于瞬时伽马响应修正的改进堆芯功率分布的测量方法,包括步骤：监测反应堆从稳定功率运行状态依靠控制棒快速插入堆芯停堆过程中堆内自给能中子探测器的响应信号,记录堆芯中所有自给能中子探测器响应信号随时间的变化；根据快速停堆前后记录的探测器响应电流,确定自给能探测器的瞬时伽马响应份额；通过堆芯在线监测系统,利用瞬时伽马响应份额修正测量过程中自给能中子探测器的测量电流或者预测过程中自给能中子探测器的预测电流,重构堆芯功率分布；有效改进堆内自给能中子探测器的测量电流-预测电流偏差,改进堆芯在线监测系统的堆芯功率分布测量精度,提高最大线功率密度、核焓升热管因子和最小偏离泡核沸腾比等安全参数的监测精度。(A method for measuring improved core power distribution based on transient gamma response correction comprises the following steps: monitoring response signals of the in-reactor self-powered neutron detectors in the process that the reactor is quickly inserted into the reactor core from a stable power operation state and is stopped by means of control rods, and recording the changes of the response signals of all the self-powered neutron detectors in the reactor core along with time; determining the transient gamma response portion of the self-powered detector according to the recorded detector response currents before and after the fast shutdown; correcting the measurement current of the self-powered neutron detector in the measurement process or the prediction current of the self-powered neutron detector in the prediction process by using the transient gamma response share through the reactor core online monitoring system, and reconstructing the power distribution of the reactor core; the method has the advantages that the measurement current-prediction current deviation of the in-reactor self-powered neutron detector is effectively improved, the reactor core power distribution measurement precision of the reactor core on-line monitoring system is improved, and the monitoring precision of safety parameters such as the maximum linear power density, the nuclear enthalpy heat-rising tube factor and the minimum deviation nucleate boiling ratio is improved.)
1. A method for measuring improved core power distribution based on transient gamma response correction is characterized by comprising the following steps:
(1) monitoring response signals of the in-reactor self-powered neutron detectors in the process that the reactor is rapidly inserted into the reactor core from a stable power operation state and is stopped by means of control rods, recording the change of the response signals of all the self-powered neutron detectors in the reactor core along with time, wherein the signal recording time interval is less than or equal to 2 s;
(2) according to the recorded response currents of the detectors before and after the fast shutdown, the transient gamma response fraction gamma of each self-powered neutron detector is determined according to the following formula＝(It-In)/ItWherein, ItFor the total response current of each self-powered detector, InIs the net neutron response current;
(3) and correcting the measurement current of the self-powered neutron detector in the measurement process or the prediction current of the self-powered neutron detector in the prediction process by using the instantaneous gamma response share through the reactor core on-line monitoring system, and reconstructing the reactor core power distribution.
2. The method for measuring the power distribution of the reactor core based on the correction of the instantaneous gamma response as claimed in claim 1, wherein the method is applied to a reactor provided with at least 1 control rod or 1 bundle of control rod assemblies, and all the control rods are inserted into the reactor core to enable the reactor core to enter a subcritical state, namely the effective multiplication coefficient keffLess than 1.0; the measurement method is applicable to a reactor core in which at least more than 2 in-core self-powered neutron detector elements are arranged.
3. The method for improving the core power distribution based on the transient gamma response correction as claimed in claim 1, wherein the incore self-powered neutron detectors arranged in the reactor comprise one or more of vanadium, rhodium, silver and other self-powered neutron detectors mainly based on (n, beta) reaction (reaction of a detector emitter which generates capture reaction with neutrons and then releases electrons through beta decay).
4. The method of claim 1 wherein the initial steady state reactor power level is above 15% power level before shutdown.
5. The method of claim 1 wherein the total response current I of each self-powered detector is determined from the recorded detector response currents before and after scram by determining the total response current I of each self-powered detectortWith net neutron response current In(ii) a StopThe response current of the reactor core self-powered neutron detector element in the stable power level state of the reactor before the reactor is It(ii) a Determining I according to the relative change rate (S) of current of the self-powered neutron detector before and after shutdownnAnd S is defined as: s ═ 2 x [ I (T)k)-I(Tk+1)]/[I(Tk)+I(Tk+1)]/[Tk-Tk+1]Wherein I is the detector current value, TkTime of kth recording point, Tk+1Time of the k +1 th recording point;
for the case that the transient gamma response fraction is a negative value (namely gamma is less than 0), the relative change rate S of the response current is a positive value along with the time and then is changed into a negative value, and the response current of the detector corresponding to the time when S is 0 in the process is marked as In(ii) a For the case that the transient gamma response fraction is positive (i.e. gamma > 0), the relative rate of change S of the response current is first a large negative value and then a small negative value close to 0, and the time corresponding to the first negative value close to 0 is recorded as In。
6. The method for improving core power distribution measurement based on transient gamma response correction of claim 1 wherein the method for measuring utilizes transient gamma response fraction corrected detector current to correct the self-powered neutron detector current I obtained by correcting the measurement process as an input to the in-core on-line monitoring systemmc＝(1-γ)*ImWherein, ImMeasuring current for a self-powered neutron detector; reactor core on-line monitoring system measures current I by using corrected neutron self-powered detectormcAnd predicting current I from the neutron detectorpAnd reconstructing the power distribution of the reactor core.
7. The method for measuring the modified core power distribution based on the transient gamma response correction as claimed in claim 1, wherein the method for measuring utilizes the transient gamma response fraction to correct the detector current to obtain the predicted current I of the self-powered neutron detector by correcting the prediction process of the on-line core monitoring systempc＝IpV. (1-. gamma.) wherein, IpIs fromPredicting current of the energized neutron detector; reactor core on-line monitoring system predicts current I by using corrected self-powered neutron detectorpcAnd measuring the current I from a self-powered neutron detectormAnd reconstructing the power distribution of the reactor core.
Technical Field
The invention relates to a measurement method, in particular to a measurement method for improving reactor core power distribution based on transient gamma response correction.
Background
The reactor core power distribution is an important parameter for monitoring or supervising the reactor core operation, so as to ensure that parameters such as the maximum linear power density, the nuclear enthalpy heat-rising pipe factor, the minimum deviation nucleate boiling ratio and the like meet the safety limit value and ensure the integrity of the fuel rod barrier. The reactor core power distribution measurement is used for verifying the reasonability of reactor core design parameters, the conservation of accident analysis parameters, calibrating the out-of-core detector and the like in the reactor core starting stage, and is used for detecting power distribution abnormity, monitoring fuel consumption distribution, verifying and calibrating the out-of-core detector in the reactor core operating stage. The commercial pressurized water reactor is widely based on actually measured in-reactor neutron detector signals and theoretically calculated neutron parameters, and reactor core power distribution is obtained in an off-line or on-line mode. But the means provided by different nuclear steam suppliers differ. The traditional second-generation pressurized water reactor monitors macroscopic reactor core power distribution such as axial flux deviation and quadrant power tilt ratio based on an out-of-reactor detector, and measures the reactor core power distribution, supervises power distribution limit parameters and calibrates the out-of-reactor detector in a periodic (such as 30-day) off-line mode through a movable micro fission chamber. With the development of the technology, the in-reactor fixed detector and the reactor core on-line monitoring system based on the in-reactor fixed detector are widely applied to the third generation of pressurized water reactors.
The in-pile fixed detector is widely used as a self-powered neutron detector of vanadium, rhodium, silver and the like. The response performance of the self-powered neutron detector is closely related to materials, geometry and irradiation environment and is influenced by the processing technology. The self-powered neutron detector reacts not only with neutrons and secondary gamma rays generated during neutron reaction, but also with external gamma rays. The current power distribution measurement method based on self-powered neutron detectors adopted by commercial pressurized water reactors does not consider the influence of the transient gamma effect. The simplified processing mode enables the deviation of the predicted current and the measured current of a part of the neutron detectors to be larger in some cases, and further causes the measurement deviation of the core power distribution to be larger. In fact, the transient gamma response of the self-powered neutron detector is closely related to the photon energy spectrum and the photon flux, and the transient gamma response fractions of the self-powered neutron detector are different at different positions due to the difference between the transient gamma energy spectrum and the photon energy spectrum at various places in the reactor. In view of the problem, a method is expected, which can accurately consider the transient gamma response share of each self-powered neutron detector in the reactor core and improve the measurement accuracy of the reactor core power distribution; it is also desirable that such a method not involve any modification of the existing commercial nuclear power plant pressurized water reactor equipment or operational operations.
Therefore, there is a particular need for an improved core power distribution measurement method based on transient gamma response correction to solve the above-mentioned existing problems.
Disclosure of Invention
The invention aims to provide an improved reactor core power distribution measuring method based on instantaneous gamma response correction, aiming at the defects of the prior art, the method monitors the response signal of an in-reactor self-powered neutron detector in the reactor fast shutdown transient process, determines the instantaneous gamma response share of the self-powered neutron detector, corrects the response signal of the in-reactor self-powered neutron detector by utilizing the instantaneous gamma response share, and improves the reactor core power distribution measuring precision.
The technical problem solved by the invention can be realized by adopting the following technical scheme:
a method for measuring improved core power distribution based on transient gamma response correction is characterized by comprising the following steps:
(1) monitoring response signals of the in-reactor self-powered neutron detectors in the process that the reactor is rapidly inserted into the reactor core from a stable power operation state and is stopped by means of control rods, recording the change of the response signals of all the self-powered neutron detectors in the reactor core along with time, wherein the signal recording time interval is less than or equal to 2 s;
(2) according to the recorded response currents of the detector before and after the fast shutdown, the transient gamma response portion gamma of each self-powered neutron detector is determined according to the following formula (I)t-In)/ItWherein, ItFor the total response current of each self-powered detector, InIs the net neutron response current;
(3) and correcting the measurement current of the self-powered neutron detector in the measurement process or the prediction current of the self-powered neutron detector in the prediction process by using the instantaneous gamma response share through the reactor core on-line monitoring system, and reconstructing the reactor core power distribution.
In one embodiment of the invention, the measurement method is applied to a reactor provided with at least 1 control rod or 1 bundle of control rod assemblies, and all the control rods are inserted into the reactor core to enable the reactor core to enter a subcritical state, namely an effective multiplication coefficient keffLess than 1.0; the measurement method is applicable to a reactor core in which at least more than 2 in-core self-powered neutron detector elements are arranged.
In one embodiment of the invention, the reactor core self-powered neutron detectors provided in the reactor comprise one or a combination of vanadium, rhodium, silver and other self-powered neutron detectors based on (n, beta) reaction (reaction in which the detector emitter releases electrons by beta decay after capture reaction with neutrons).
In one embodiment of the invention, the reactor initial steady-state power level is above the 15% power level prior to shutdown.
In one embodiment of the invention, the total response current I of each self-powered detector is determined from the recorded detector response currents before and after the scram in the following mannertWith net neutron response current In(ii) a The response current of the reactor core self-powered neutron detector element in the stable power level state of the reactor before shutdown is It(ii) a Determining I according to the relative change rate (S) of current of the self-powered neutron detector before and after shutdownnAnd S is defined as: s ═ 2 x [ I (T)k)-I(Tk+1)]/[I(Tk)+I(Tk+1)]/[Tk-Tk+1]Wherein I is the detector current value, TkTime of kth recording point, Tk+1Time of the k +1 th recording point;
for the case that the transient gamma response fraction is a negative value (namely gamma is less than 0), the relative change rate S of the response current is a positive value along with the time and then is changed into a negative value, and the response current of the detector corresponding to the time when S is 0 in the process is marked as In(ii) a For the case that the transient gamma response fraction is positive (i.e. gamma > 0), the relative rate of change S of the response current is first a large negative value and then a small negative value close to 0, and the time corresponding to the first negative value close to 0 is recorded as In。
In one embodiment of the invention, the measurement method utilizes the transient gamma response fraction to correct the detector current by correcting the self-powered neutron detector current I obtained by the measurement process as input to the in-core on-line monitoring systemmc＝(1-γ)*ImWherein, ImMeasuring current for a self-powered neutron detector; reactor core on-line monitoring system measures current I by using corrected neutron self-powered detectormcAnd predicting current I from the neutron detectorpAnd reconstructing the power distribution of the reactor core.
In one embodiment of the invention, the measurement method utilizes the transient gamma response fraction to correct the detector current and corrects the predicted current I of the self-powered neutron detector obtained by the prediction process of the on-line core monitoring systempc＝IpV. (1-. gamma.) wherein, IpPredicting current for a self-powered neutron detector; reactor core on-line monitoring system predicts current I by using corrected self-powered neutron detectorpcAnd measuring the current I from a self-powered neutron detectormAnd reconstructing the power distribution of the reactor core.
Compared with the prior art, the method for measuring the improved reactor core power distribution based on the instantaneous gamma response correction can effectively improve the measurement current-prediction current deviation of the in-reactor self-powered neutron detector, improve the reactor core power distribution measurement precision of the reactor core on-line monitoring system, improve the monitoring precision of safety parameters such as the maximum linear power density, the nuclear enthalpy heat-raising pipe factor, the minimum deviation nucleate boiling ratio and the like, and achieve the purpose of the invention.
The features of the present invention will be apparent from the accompanying drawings and from the detailed description of the preferred embodiments which follows.
Drawings
FIG. 1 is a schematic diagram of the improved core power distribution measuring device based on the transient gamma response correction according to the present invention;
FIG. 2 is a schematic diagram of the construction of the control rod and in-stack self-powered neutron detector arrangement of the present invention;
FIG. 3 is a schematic of the relative rate of change of current of the self-powered neutron detector of the present invention over time before and after a shutdown.
Detailed Description
In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further explained below by combining the specific drawings.
The invention discloses a method for measuring improved reactor core power distribution based on transient gamma response correction, which comprises the following steps:
(1) monitoring response signals of the in-reactor self-powered neutron detectors in the process that the reactor is rapidly inserted into the reactor core from a stable power operation state and is stopped by means of control rods, recording the change of the response signals of all the self-powered neutron detectors in the reactor core along with time, wherein the signal recording time interval is less than or equal to 2 s;
(2) according to the recorded response currents of the detector before and after the fast shutdown, the transient gamma response portion gamma of each self-powered neutron detector is determined according to the following formula (I)t-In)/ItWherein, ItFor the total response current of each self-powered detector, InIs the net neutron response current;
(3) and correcting the measurement current of the self-powered neutron detector in the measurement process or the prediction current of the self-powered neutron detector in the prediction process by using the instantaneous gamma response share through the reactor core on-line monitoring system, and reconstructing the reactor core power distribution.
The reactor applicable to the measuring method is provided with at least 1 control rod or 1 bundle of control rod assemblies, and the reactor core enters a subcritical state after all the control rods are inserted into the reactor core, namely the effective multiplication coefficient keffLess than 1.0; the measurement method is applicable to a reactor core in which at least more than 2 in-core self-powered neutron detector elements are arranged.
The reactor core self-powered neutron detector arranged in the reactor comprises one or a combination of more of vanadium, rhodium, silver and self-powered neutron detectors which mainly take (n, beta) reaction (reaction that a detector emitter and neutrons release electrons through beta decay after capture reaction).
The reactor initial steady power level is above the 15% power level before shutdown.
The total response current I of each self-powered detector is determined according to the response currents recorded before and after the fast shutdowntWith net neutron response current In(ii) a The response current of the reactor core self-powered neutron detector element in the stable power level state of the reactor before shutdown is It(ii) a Determining I according to the relative change rate (S) of current of the self-powered neutron detector before and after shutdownnAnd S is defined as: s ═ 2 x [ I (T)k)-I(Tk+1)]/[I(Tk)+I(Tk+1)]/[Tk-Tk+1]Wherein I is the detector current value, TkTime of kth recording point, Tk+1Time of the k +1 th recording point;
for the case that the transient gamma response fraction is a negative value (namely gamma is less than 0), the relative change rate S of the response current is a positive value along with the time and then is changed into a negative value, and the response current of the detector corresponding to the time when S is 0 in the process is marked as In(ii) a For the case where the transient gamma response fraction is positive (i.e., gamma > 0), the relative rate of change S of the response current is first a large negative value over time and then turns toThe response current of the detector corresponding to the time when the first negative value close to 0 is marked as In。
The measuring method utilizes the transient gamma response fraction to correct the current of the detector and corrects the current I of the self-powered neutron detector obtained by the measuring process input by the reactor core on-line monitoring systemmc＝(1-γ)*ImWherein, ImMeasuring current for a self-powered neutron detector; reactor core on-line monitoring system measures current I by using corrected neutron self-powered detectormcAnd predicting current I from the neutron detectorpAnd reconstructing the power distribution of the reactor core.
The measuring method utilizes the transient gamma response fraction to correct the current of the detector and corrects the predicted current I of the self-powered neutron detector obtained in the prediction process of the reactor core on-line monitoring systempc＝IpV. (1-. gamma.) wherein, IpPredicting current for a self-powered neutron detector; reactor core on-line monitoring system predicts current I by using corrected self-powered neutron detectorpcAnd measuring the current I from a self-powered neutron detectormAnd reconstructing the power distribution of the reactor core.
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