KR101118553B1 - Method and system for testing in-core flux detectors - Google Patents

Abstract

The present invention relates to a system and method for testing an in-core flux detector that determines an effective prompt fraction for an in-core flux detector based on the detector's dynamic response to an output change event in the reactor. The ion chamber detector can provide a reference signal, which can be compared with this reference signal. In-core flux detector response is analyzed over a time interval following the output change event, which may be shorter than the time constant for the shortest delay component of the detector response. The data acquisition system may include a number of subsystems that are separated from each other through separation barriers. In particular, clock signals from one subsystem to another may be passed through a separation barrier.

Description

METHOD AND SYSTEM FOR TESTING IN-CORE FLUX DETECTORS

1 shows a block diagram of a data acquisition system for testing an in-core flux detector.

FIG. 2 shows a block diagram of a data capture subsystem in the data capture system of FIG.

3 is a flow chart illustrating a method for testing in-core flux.

DESCRIPTION OF THE REFERENCE SYMBOLS

10: data acquisition system 12a to 12f: safety system channel

14a to 14f: Data capture subsystem 16: Instrument panel

18a to 18f: Isolation Amplifier

20a to 20f: Computer 22a to 22f: Signal adjusting unit

24 separation barrier 30 instrument signal

32: Separated device signal 34: Adjusted signal

36: clock signal 40: filter

42: amplifier 44: DC-offset regulator

46: A / D converter 48: Microprocessor

50: clock 52: display

54: memory 56: control signal

The present invention relates to flux detectors for nuclear reactors, and more particularly to testing in-core flux detectors.

Permanently mounted in-core flux detectors (ICFDs) are used in many reactor facilities to prevent local over-power in the reactor core. ICFD is part of one or more safety stop systems in a reactor. ICFD is designed to detect sudden increases in flux caused by accidents. Therefore, ICFDs must respond quickly to flux increases within specified time intervals to meet safety requirements. ICFDs are called neutron-over-power (NOP) or regional over-power (ROP) detectors.

The ICFD is a self-powered flux detector that produces a measurable current in the ㎂ range. ICFD is sensitive to both neutron and gamma fields. Under steady state conditions, the generated current is proportional to the local thermal neutron flux. In the case of neutron flux transitions, the current signal of the detector may be delayed rather than the flux change, since the current generation process of the ICFD involves a component of a slow response, causing a signal delay. The dynamic transfer function of the flux-current conversion of the ICDF has a positive or negative amplitude and a large instantaneous, under-prompt or over-prompt with ICFD. It contains the response component and a series of fewer components that are exponentially delayed.

The dynamic response of the ICFD can change with time for changes in material (combustion) and as a result of defects. In order to ensure that the ICFD can respond quickly enough to meet safety requirements, it is necessary to ensure that the immediate response component is greater than the minimum acceptable limit. Therefore, it is desirable to start a regular product with a computer readable medium that explicitly implements computer executable instructions for testing in-core flux detectors (ICFDs) in reactors, which reactors include measuring instruments including ICFDs. This measuring instrument then generates a response signal as a result of the step change of the reactor output. Such computer executable instructions may be used to determine an effective prompt fraction for an ICFD based on a computer executable instruction for receiving and recording a response signal from a measuring instrument comprising the ICFD and the recorded response signal. Contains computer executable instructions.

Other aspects and features of the invention will become apparent to those skilled in the art from the following description of specific embodiments of the invention in conjunction with the accompanying drawings.

Reference is made to the accompanying drawings showing embodiments of the invention by way of example.

Like reference numerals are used to designate like elements in different drawings.

The present invention provides a method for determining the effective immediate fraction for an ICFD based on the measured response of the ICFD to a step change in reactor output.

The immediate fraction for ICFD is the ICFD response rate for the reactor flux change divided by the baseline instantaneous response to the same reactor flux change. The actual response signal generated by the ICFD contains a constant delay component in situ. Some of these delay components may be due to detectors, and some may be due to delayed gamma fields in the reactor. The measurement of the signal generated by the ICFD as the gradual change in the reactor output will reflect the driving force of the delay response, which is driven by external factors including detector characteristics and physical considerations such as the delay gamma field and the position of the detector. It can be attributed to both characteristics. All of these delay sources adversely affect the effective immediate fraction determined based on the measurement response.

The reactor output change used to test the immediateness of the ICFD is to model an accident situation where there is a sudden increase in local neutron flux. Ideally, the test would involve the introduction of a stepwise change in reactor output, but this is not possible for safety reasons. Thus, in most embodiments, the reactor output change is a stepwise decrease in reactor output. In some embodiments, the output change includes a trip of the reactor output. In many cases, shutdowns of these outputs are regularly scheduled for maintenance and testing and are scheduled to occur every two years.

The use of a decrease in output instead of an increase in output to test the improvisation of the ICFD means that the kinetics of the detector response to stepwise changes in the reactor output, ie the resulting change in neutron and gamma field flux, is approximately linear and symmetric in both directions. Requires the assumption that The constant delay component of the neutron or gamma field, such as the delayed gamma field resulting from accumulated cleavage products, may have a dynamic that depends on whether the reactor output change is positive or negative. In order to rely on the symmetry of the detector signal spontaneous, another assumption is made that the cleavage products accumulated according to the same kinetics after setup change in thermal neutron flux because the reactor collapses after the trip.

)의 신속한 처리를 통해 검출기의 물질과 상호작용하는 원자로의 감마 필드에 의해 유도되지만, 감마 필드의 1/3은 중성자 플럭스의 변화에 대해 지연되어, 검출기 전류에서 13%의

관련 지연 성분을 초래한다. 검출기에서 발생하는 상호작용(

) 이 신속하다 할지라도, 지연은 여전히 검출기에 기인한다. 지연된 감마 필드의 소스는 긴 기간의 최대 출력의 동작 이후 축적되는 분열 산물이다. 검출기가 트립될 때, 중성자와 감마 필드는 곧 바로 0으로 떨어지지만, 연료 내에서 저장된 분열 산물의 느린 붕괴와 다른 노심 성분은 여전히 상당한 감마 필드를 생성한다. 분열 산물의 다양한 베타 및 감마 붕괴의 케스케이드(cascade)는 일정한 동력학을 갖는데, 이러한 동력학은 부분적으로 원자로 트립에 응답하는 ICFD 신호의 지연된 전류를 결정한다.By way of example, platinum-clad inconel ICFDs have mixed neutron and gamma sensitivity. 40% of that current is (

Is induced by the gamma field of the reactor interacting with the material of the detector through rapid processing, but one third of the gamma field is delayed for changes in neutron flux, resulting in 13% of the detector current.

Resulting in relevant delay components. Interactions that occur at the detector (

Although is fast, the delay is still due to the detector. The source of the delayed gamma field is the cleavage product that accumulates after the operation of the long maximum output. When the detector trips, the neutrons and gamma fields immediately drop to zero, but the slow decay of cleavage products stored in the fuel and other core components still produce significant gamma fields. The cascades of various beta and gamma decay products of the cleavage product have constant kinetics, which determine in part the delayed current of the ICFD signal in response to reactor trips.

The inclusion of delay components that cannot be attributed to the detector in the effective immediate fraction estimate can be justified in the sense that these non-detector delays can still be applied to the effective immediate fraction for the detector signal in real accident scenarios. In other words, the spontaneity of the detector signal is still influenced by the position of the detector in the core (as opposed to the detector itself), the length of the lead cable and the output history of the reactor core.

The effective immediate fraction of the ICFD signal includes the ratio between the immediate change in the ICFD signal following the reactor change and the immediate change in the 100% rapid reference detection signal measured during the same reactor change. In one embodiment, the reactor change is a reactor trip and a 100% rapid reference detector signal is obtained from one or more ex-core ion chambers. The ion chamber responds to rapid changes in neutron flux and is not affected by delayed gamma flux. In one embodiment, the effective immediate fraction is calculated as the post-trip drop of the normalized ICFD signal averaged over a constant time interval after the trip divided by the average signal drop of the normalized reference ion chamber signal.

After the start of the trip, there is a short delay of about 0.4 seconds before the flux signal starts to respond. This initial latency may be due, in part, to the delay of the trip mechanism to reach that area of the core. For example, if the trip mechanism involves dropping a shutoff rod to stop the nuclear reaction in the core, it takes a limited time before the rod falls into calandria and begins to affect the reaction. Another type of trip mechanism is the insertion of a liquid poison (gadolinium) to stop the reaction in the core. It also takes a limited time for the poison to be inserted into the Callandira and affect the reaction in the local region of the detector. The degree of this delay depends in part on the position of the detector within the core.

Once the flux signal begins to respond, the neutron flux signal drops to low levels over a constant time interval of about 0.3 seconds to 0.8 seconds. The time constant of the shortest delay component is about 3.9 seconds, which means that there is sufficient separation to assess the immediate fraction according to the invention.

In one embodiment, the effective immediate fraction of the ICFD is from the normalized drop in the ICFD signal measured 3 seconds after the start of the flux drop, with respect to the normalized drop in the reference ion chamber measured 3 seconds after the start of the flux drop. Is calculated. This signal is normalized between the pre-trip value and the voltage output ("zero-floor") which is the rated zero-output of the amplifier. These nominal floor values vary from station to station. The actual "zero floor" value may be different from the design value due to the device zero-offset bias of the NOP amplifier (station hardware) and recording channel (data acquisition system).

Determination of the effective immediate fraction according to the invention may comprise two steps. The first is to determine the uncompensated effective immediate fraction from the measured data obtained during the reactor trip. The second is to apply a correction term to the uncompensated effective instant fraction to obtain an effective instant fraction. In some embodiments, these two steps are not performed in a distinct and continuous manner.

The correction term applied to the uncompensated effective immediate fraction based on the measurement includes a correction based on modeling, which changes the uncompensated effective immediate fraction by a few percent. The relatively appropriate effect of the correction term allows the use of nominal ICFD parameters instead of the actual specific ICFD parameters and the use of a simplified time function of flux variation.

The correction term may be used to eliminate the effects of output change prior to trip, such as output ramp, where reactor output continues to ramp down by 60% from the maximum output before the maximum reactor trip is initiated. The correction term is also already active and affects the shortest delay component due to the ICFD trip response after 3 seconds, the effect of zero-offset bias of the data capture recording channel, and the long term after trip released by the cleavage product upon delayed beta-decay. Can be used to eliminate the effects of delayed gamma fields.

A. Data Acquisition System

As noted above, typical reactors use a large number of ICFDs distributed over several redundant safety system channels. Each safety channel includes an ion chamber to monitor a set of ICFDs and other devices. These devices are distributed through the reactor zone in and out of the core. In order to meet safety requirements, the safety channels need to be kept separate from each other. If the safety channels are to be interconnected, there is a risk that a fault in one channel will affect the other, which damages the entire safety system.

 Reference is now made to FIG. 1, which shows a block diagram of a data acquisition system 10 for testing an in-core flux detector. The data acquisition system 10 is distributed through six safety system channels, shown as 12a, 12b, ..., 12f. The six channels correspond to two safety systems with three channels each. The data acquisition system 10 includes a number of subsystems, designated 14a, 14b, ..., 14f, corresponding to six safety system channels 12a, 12b, ..., 12f. Each data acquisition subsystem 14a-14f is connected to a device panel 16 that receives signals from multiple devices, in one embodiment up to 24 devices. Data acquisition subsystems 14a-14f include isolation amplifiers 18a-18f for receiving device signals 30 in parallel from device panels 16a-16f. Isolation amplifiers 18a through 18f prevent feedback from data acquisition system 10 to instrument panels 16a through 16f, and output a separate instrument signal 32. In one embodiment, the separation amplifiers 18a to 18f are 1: 1 amplifiers without filtering.

Data acquisition subsystems 14a-14f also include signal conditioning units 22a-22f. The signal adjustment units 22a to 22f receive the separated device signal and output the adjusted signal 34. Signal conditioning units 22a through 22f may perform a number of tasks including analog amplification, DC offset adjustment, and analog low pass filtering.

Data acquisition subsystems 14a-14f further include computers 20a-20f for receiving the adjusted signals 34, digitizing them, and storing them locally.

The data recorded by the computers 20a-20f during the trip event is then used to determine the effective fraction of immediates for one or more ICFDs included in the reactor equipment. To perform this analysis, the data for the ICFD of interest can be compared with data corresponding to an ion chamber, another ICFD, or another device. In order to make a useful comparison, the data needs to have a common reference time. Computers 20a to 20f in data acquisition system 10 typically each have their own clock since they operate independently of other data acquisition subsystems 14a to 14f. Thus, the difficulty that arises is to synchronize the computers 20a to 20f without compromising safety system disconnection requirements.

To solve this difficulty, one of the computers 20a to 20f, for example the computer 20a, is designated as a "master" computer, and the remaining computers 20b, 20c, ..., 20f are designated as "slaves", but they are However, the master does not have a master-slave relationship typically found in operations with a certain level of controlling the slave. The master computer 20a outputs the clock signal 36 supplied to the other computers 20b, 20c, ..., 20f. The clock signal 36 passes through a separation barrier 24 between each computer 20a-20f to ensure that the computers 20a-20f remain separated from each other. Each of the slave computers 20b, 20c, ..., 20f receives this clock signal 36, adds a timestamp to any data record, or otherwise masters the data record of the adjusted signal 34. The reference clock signal 36 is connected from 20a. Thus, the data stored locally at each computer 20a to 20f may later be collected and combined for analysis using a common time reference.

In one embodiment, the separation barrier 24 is a light separator. Separation barrier 24 may include other mechanisms for separating signals, including galvanic electrical separators and other separators. Separation barrier 24 should be chosen to provide adequate signal to noise ratio and temperature sensitivity. Separation barrier 24 may provide for double separation.

In one embodiment, clock signal 36 includes a clock signal and a time confirmation signal. The time confirmation signal can be recorded for later analysis and any error correction in the clock signal. In one embodiment, the time confirmation signal is a triangular wave signal.

Conventional CANDU reactors include a communication system for communicating between spaces within the reactor via a headset. In some embodiments, such existing communication systems may be used to provide interconnection of components for the data acquisition system 10 shown in FIG. In particular, existing communication systems may provide a mechanism for connecting the various data acquisition subsystems 14a-14f to distribute the clock signal 36 with the isolation barrier 24.

Reference is now made to FIG. 2, which shows a block diagram of one of the data acquisition subsystems 14a-14f. The signal adjustment unit 22 comprises a filter 40, an amplifier 42 and a DC-offset regulator 44 for each of the separate instrument signals 32. Filter 40 may include an anti-aliasing low pass filter. The computer 20 includes an analog-to-digital (A / D) converter 46 that digitizes the adjusted signal 34. The digitized signal generated by the A / D converter 46 is provided to the microprocessor 48, which stores the digital data in the memory 54. The microprocessor 48 includes the data acquisition subordinates, including the transmission of the control signal 56 to the signal adjustment unit 22 to control the filter 40, the amplifier 42 and the DC-offset regulator 44. Coordinate and manage system 14.

The computer 20 further includes a clock 50, which in some embodiments is part of the microprocessor 48, and generates a clock signal 36.

The computer 20 also includes a display 52 and other outputs, and an input device (not shown) that allows a user to interact with the computer 20.

Those skilled in the art will appreciate that the computer 20 may be a personal computer or other workstation. The computer 20 may also be a microcontroller or other programmable processing device for use in managing the data capture process.

In one embodiment, data acquisition subsystem 14 receives, digitizes, and records data for 24 devices. The data collected has sufficient resolution to provide accurate information taking into account the immediateness of the ICFD. In one embodiment, data acquisition subsystem 14 samples a 500 Hz instrument signal with an amplitude resolution of 0.1 mV (ie, A / D converter 46 samples the adjusted signal 34). In order to provide sufficient resolution, sampling should be done at one or more sampling rates every 10 ms.

In order to determine the immediateness of the equipment under test, it is necessary to know when the output change (ie reactor trip) actually occurs within the recorded data. Thus, one of the instruments measured by the data acquisition system 10 is a trip mechanism. The trip mechanism can be a pushbutton or other trigger that initiates a trip event. Pushbuttons cause the release of neutron-absorbing rods or the injection of neutron-absorbing poisons, thereby promoting reactor shutdown events. Therefore, a set of recorded data will indicate the exact occurrence of the trip initiation. The trip mechanism then develops and begins to affect the neutron response in the core and takes a limited time to propagate to the individual detector.

Computer 20 is suitably programmed to control various hardware components and perform data sampling and storage functions. Programming of the computer 20 to perform these functions is understood by those skilled in the computer software arts. Software developed to control the operation of the computer 20 provides a user interface that allows a user to set certain parameters including the sampling rate.

B. Determination of Effective Immediate Fraction

The effective instant fraction that can be determined from the measurements obtained using the test system described above relates to the actual instant fraction. Using mathematical models of ICFD kinetics and trip events, the relationship between the actual instantaneous fraction and the effective instantaneous fraction can be determined.

}와 검출기 임펄스 응답 함수{h(t)}의 컨벌루션(convolution)에 관한 출력 전압 신호(V_D(t))를 생성한다. 검출기 임펄스 응답 함수는 실제 즉발 분율(p)과, 시상수(τ_n)와 상대 진폭(k_n)을 각각 갖는 N 개의 지연 요소를 포함하는데, 여기에서 n=1,...,N이다. 이러한 관계는 다음의 수학식으로 표시된다.ICFD is a time-dependent flux {

} And the output voltage signal V _D (t) relating to the convolution of the detector impulse response function {h (t)}. The detector impulse response function includes N delay components each having an actual instantaneous fraction p, a time constant τ _n and a relative amplitude k _n , where n = 1, ..., N. This relationship is represented by the following equation.

는 Dirac-delta 함수를 포함하고,

이다.From here

Contains the Dirac-delta function,

to be.

), 전류-전압 변환 인자(

), 및 전압 증폭기 이득 인자(

)를 포함한다. 제 1 파라미터는 ICFD의 감도 또는 전류 수율이고, 이는 ICFD의 수명을 통해 변화할 수 있다. 전류-전압 변환 인자와 전압 증폭기 이득 인자는 신호 기기의 변환기/증폭기에서 설정되고, 검출기 감도의 변화를 보상하기 위하여 조정될 수 있다. 변환 인자(C_D)를 사용하여, 검출기 전압은 다음의 수학식을 사용하여 모델링된다.The detector voltage is modeled as a function of the flux-to-voltage conversion factor C _D of the detector, which is itself a flux-current conversion factor (

), Current-voltage conversion factor (

), And the voltage amplifier gain factor (

). The first parameter is the sensitivity or current yield of the ICFD, which can change over the lifetime of the ICFD. The current-voltage conversion factor and the voltage amplifier gain factor are set in the converter / amplifier of the signal device and can be adjusted to compensate for the change in detector sensitivity. Using the conversion factor C _D , the detector voltage is modeled using the following equation.

Where V _B is a constant voltage offset measured at zero output. The actual zero-output offset voltage V _B may vary from signal to signal due to possible biases within the station device and the data acquisition recording channel. The difference between the zero-output offsets of the other signals is typically in the range of ± 10 mV or 0.2% of the monitored voltage range. This uncertainty results in a ± 0.5% bias at the estimated fraction fraction.

Equations 1 and 2 combine to derive the following equation of detector output voltage V _D as a function of time dependent flux.

The parameter values k _n and τ _n of the N delay components are not necessarily related to the actual physical processor, but rather are the optimum exponential fit for the measured detector response. By measuring the detector response signal and applying an exponential curve to the measured signal, a design or nominal value for the parameter values k _n and τ _n can be obtained. The delay parameter is related to the instantaneous fraction through the following normalized equation.

)로부터 시간 간격(

)이후 나중의 일정한 플럭스(

)로 선형적인 플럭스 변화로서 모델링될 수 있다. 시간 t의 함수로서 플럭스는 다음과 같이 표현된다. After obtaining the modeling equation, equation 3 for the detector voltage (V _D ), the reactor trip is subjected to an initial stop flux at time t = 0 (

Time interval from

Constant flux afterwards

Can be modeled as a linear flux change. The flux as a function of time t is expressed as

을 사용한다면, 즉발 분율(p)은 측정된 검출기 신호(V_D)의 함수로서 다음과 같이 표현될 수 있다.In order to access the delay current component of the nominal ICFD, the above equation of linear flux change is a good approximation of the actual flux drop during the reactor trip. The advantage of this simplified function is that it provides an analysis of the trip response of the ICFD voltage signal, which is necessary to perform parametric investigation. The linear gradient descent expression in equation (5) is inserted into equation (3) for time (t> Δt), and the equation before the trip

If is used, the instantaneous fraction p can be expressed as follows as a function of the measured detector signal V _D.

는 원자로 트립 이후 검출기 전압에서 상대적인 하강을 나타내고, 반면

는 노심 검출기의 위치에서 상대적인 플럭스 하강을 나타낸다. 수학식 6에서 첫번째 항은 "유효 즉발 분율"을 나타내는데, 이는 다음의 수학식 7을 사용하여, 측정된 시간 열 신호로부터 직접 계산될 수 있다.From here

Represents the relative drop in detector voltage after the reactor trip,

Denotes the relative flux drop at the position of the core detector. The first term in Equation 6 represents the " effective immediate fraction ", which can be calculated directly from the measured time train signal using Equation 7 below.

Therefore, Equation 6 can be rewritten as follows.

Since the detector voltage signal V _D (t) is sampled continuously and frequently during the reactor trip test, the time t is selected such that Δt <t <τ _n to minimize the effect of the latter part of Equation 8. With this approach, Equation 8 can be approximated as follows.

If the time point t is chosen to be close to Δt for the shortest time constant min {τ _n }, the expression on the right approaches zero. In this case, the instantaneous fraction p is approximately equal to the effective instantaneous fraction P _eff (t).

)이 이온 챔버 신호의 상대적인 신호 하강에 의해 근사될 수 있는 점이다. 실제로, 트립 이후의 플럭스 형태가 트립 이전의 정지 플럭스 형태와 다르기 때문에, 상대 플럭스 하강은 검출기의 위치에 의존한다. 만약 검출기 위치에서 트립 이전의 정지 플럭스의 ±15%의 변동과, 트립 이후 단일 플럭스 형태가 가정된다면, 상대 플럭스 하강 가정의 적용은 유효 즉발 분율에서 ±1.5%의 변동을 초래한다.Another approximation that can be used to simplify modeling is the relative flux drop from

) Can be approximated by the relative signal drop of the ion chamber signal. In practice, the relative flux drop depends on the position of the detector since the flux shape after the trip is different from the stationary flux shape before the trip. If a fluctuation of ± 15% of the static flux before the trip at the detector position, and a single flux form after the trip is assumed, the application of the relative flux falling hypothesis results in a variation of ± 1.5% in the effective immediate fraction.

Thus, the effective immediate fraction of the ICFD in the reactor uses the time-recorded signal data measured from the instrument, and the time t satisfying the condition Δt <t <min {τ _n } and the following equation: Can be evaluated.

는 이온 챔버 신호의 상대적인 신호 하강이다.From here,

Is the relative signal drop of the ion chamber signal.

In another embodiment, the post-trip signal in Equation 10 is normalized over a time interval t ₁ , t ₂ that satisfies the condition Δt <t ₁ <t ₂ <min {τ _n }. In one embodiment, t ₁ is 2.5 seconds and t ₂ is 3.5 seconds.

In another embodiment, reactor trips can occur as a result of power variations, typically ramp-down of output from a maximum output to a fraction of maximum output, such as 60%. After power-slope reduction, the reactor remains at a steady state output for several hours before the trip is initiated.

로부터

로의 선형적인 플럭스 감소일 수 있다. 그후 출력은 출력 트립이 발생하는 시간(t_T)까지 일정하게 유지된다. 출력 트립 도중에, 플럭스는 시간 간격(Δt) 동안

로부터

로 감소한다. 두 가지 경사가 다음과 같이 표현될 수 있다.In this case, the power reduction starts at time t _R and during the time interval Δt.

from

Linear flux reduction in the furnace. The output then remains constant until the time t _{T at} which the output trip occurs. During the output trip, the flux will remain for the time interval (Δt)

from

Decreases. Two slopes can be expressed as follows.

For example, Δt may be 4 to 10 minutes. The output stop between the output ramp down and the trip event is typically between 30 minutes and 8 hours, but can be longer or shorter.

Using the same definition for the effective instant fractions that resulted in Equation 7, the effective instant fractions in this case can be defined as follows.

The detector voltage from equation (3) is combined with the equation for flux to derive the equation for the detector voltage for a time (t> t _T + Δt) that includes two exponential signal transitions corresponding to two linear output slopes. .

For the time t> t _T + Δt, the detector signal in equation (14) shows the overlap effect of two independent power reductions. It will be appreciated that in other embodiments with multiple output slopes the equation may be modified to include additional terms.

The detector signal before the trip is given by the following equation.

Equations 14, 15 and 13 can be obtained for the effective instant fractions for time t > t _T + Δt.

로 설정됨으로써 선행 출력 경사 감소가 없는 안정 상태 조건 하에서의 트립의 경우를 포함하는 것을 이해할 것이다. 이 경우, 수학식 16은 수학식 8과 동일하게 된다.It will be appreciated that the effective immediate fraction given in (16) is not equal to the actual fraction p, but if the correct time interval is selected, the difference can be minimized. Equation 16

It will be appreciated that this includes the case of tripping under steady state conditions without prior output slope reduction. In this case, Equation 16 becomes the same as Equation 8.

C. Correction of Effective Immediate Fraction

As understood from the equations above, the correction term may be incorporated into a decision based on the measurement of the effective immediate fraction. One possible correction occurs when the shortest delay component is close to the measurement interval and its relative contribution is large. Another possible correction occurs when there is one or more output changes that occur before the measurement interval, such as a decrease in output slope. In this case, the ICFD current signal is still unbalanced and therefore slightly biased. Another possible correction occurs when the trip involves a long maximum output operation, which accumulates a cleavage product that produces a long decay gamma field, resulting in a residual ICFD current. Other cases lead to other corrections that can be applied to estimate effective immediate fraction based on the measurement.

In the first case, the effective instant fraction may overestimate the true instant fraction of the detector as a result of the bias that may result from the trip response of the shortest delay component. In one embodiment, this component has a time constant of approximately 3.9 seconds with a relative contribution of 1.6%. Three seconds after the start of the flux drop, the trip response of the shortest delay component contributes to the immediate response of the ICFD.

 In order to eliminate the influence of this delay component, trip response determination is made on a known detector parameter. The lookup table of values based on modeling provides a mechanism to correct the effective immediate fraction based on the measurement. Therefore, the influence of the delay component can be calculated using the right term of Equation 8 or Equation 9.

In the case of an output slope, a lookup table can also be used to provide a correction term. This lookup table is generated through modeling. The appropriate correction term may be calculated as described above with reference to Equations 14-16.

For the third case, the long term decay gamma field produces residual ICFD current, which provides a constant "background" detector signal for the "zero output voltage floor". This effect makes the ICFD less immediate because the relative drop of the signal is less than the relative decrease of the reference signal.

The magnitude of the decay gamma effect on individual ICFDs cannot be easily assessed by reactor theory, but the measurement itself provides a solution for long term. After a sufficiently long time after the trip, the measured signal contains the following components.

1. The design value of the "zero-floor" of a NOP amplifier,

2.zero-offset bias of the NOP amplifier (presumed to be ± 10 mV),

3. zero-offset bias of the recording channel (measured before signal connection),

4. Residual ICFD signal generated by long term decay gamma field.

Thus, the time average of the ICFD signal is taken after a significant time after the trip. In one embodiment, the measurement is made approximately one day after the trip. These averages can be used as the zero output voltage floor to eliminate the effects of gamma field residual voltage and unknown device bias. By setting the cutoff time of the ICFD response signal, the delay component considered as part of the detector response is separated from the long-term gamma residual component. These averages are used in normalizing the ICFD signal.

Reference is now made to FIG. 3, which shows in flowchart form a method 100 for testing ICFD in a reactor. The method 100 begins at step 102 initiating data collection using the data capture system 10 (FIG. 1). The data acquisition system 10 begins to collect data about the device, including the ICFD, the ion chamber, and the trip mechanism. The data before this trip can be used later to normalize the reads.

In step 104, a reactor trip is initiated. During the output change, the data capture system 10 continues to accumulate data from the equipment in the reactor. The data is stored locally, and if one or more local data storage devices have to be created, as shown in six separate channels in FIG. 1, the data is compiled together in step 106. As discussed above, data collection may continue for several hours after a trip event to collect data for gamma field residual voltage and zero-output device bias for use in correcting the effective immediate fraction estimate through normalization. . Normalization of the reads takes into account the average value before the trip and the average value after the trip.

In step 108, the measured data is used to determine the relative signal change during the immediate period. The immediate period is the time period following the onset of the trip event, which is shorter than the time constant of the shortest delay component. As described above, the instantaneous period in one embodiment is set to 3 seconds. As described above, in one embodiment, the average signal between 2.5 and 3.5 seconds is used to determine the relative signal drop relative to the start signal level at the start of the output trip.

In step 110, the measured data is used to determine the relative flux drop over the same instantaneous period. The dynamic response of the 100% instantaneous instrument is used as a substitute for determining the relative flux drop. In one embodiment, such a device includes an ion chamber. The relative change in the output signal from the ion chamber is taken to represent the relative flux drop.

As mentioned above, the previous decision may be based on an average over a predetermined sample period, such as 1 second. The initiation signal value used to determine the relative signal change may be the average value of the steady state prior to the trip event. All signal values can be normalized with respect to measurements before and / or after trip to eliminate voltage-offset bias and other effects.

Once the relative signal change for ICFD is determined and the relative flux change is determined during the instantaneous period, these amounts can be used in step 112 to determine the effective instantaneous fraction. The effective immediate fraction is determined based on the ratio of the relative ICFD signal change to the relative flux change, in one embodiment the relative flux change is a relative ion chamber signal change. Determination of the effective immediate fraction may be made according to Equation 10. If the trip event involves an output slope, the effective immediate fraction may be determined according to equation (13).

In step 114, various corrections may be incorporated to refine the effective immediate fraction according to the environment. For example, the time average of the ICFD signal after a long time after the trip event can be used to establish a zero-output offset bias. Once determined, this bias is removed from the determination of the effective immediate fraction. Various other corrections or refinements can be incorporated into the determination of the effective immediate fraction as described above with reference to the equation.

Although the method 100 described above describes a correction applied after the calculation of the effective immediate fraction, those skilled in the art will, in some cases, configure any correction term within the determination of the relative signal change or the determination of the effective immediate fraction. Will be more appropriate according to the For example, the calculation of the zero-output voltage floor can be integrated into the calculation of the relative signal drop of the ICFD.

The invention can be embodied in other specific forms without departing from the spirit or essence of the invention. Certain applications and modifications of the invention will be apparent to those skilled in the art. Therefore, the foregoing embodiments are to be considered in all respects only as illustrative and not restrictive, and the scope of the present invention is shown by the appended claims rather than the foregoing description, and therefore falls within the meaning and range of equivalency of the claims. All changes are included.

Claims (39)

As a method of testing an in-core flux detector (ICFD) in a reactor, (a) initiating a step change in reactor output, (b) receiving a response signal from a measuring device comprising the ICFD; (c) digitizing and recording the response signal; (d) determining an effective porompt fraction for ICFD based on the recorded response signal. The method of claim 1, wherein the determining step includes determining a dynamic response of ICFD and a ratio of flux change in the reactor. The ICFD test of claim 2, wherein the response signal comprises an ICFD response signal for the ICFD and the dynamic response comprises a relative change in the ICFD response signal over a predetermined interval following the initiating step. Way. 4. The ICFD response signal of claim 3, wherein the ICFD response signal comprises a delay component, each component having a time constant, the predetermined interval being shorter than the shortest of the time constants, followed by a time period following the onset of the step change. Including, ICFD test method. The method of claim 4, wherein the time period is less than about 3.9 seconds. 4. The method of claim 3, wherein the response signal comprises an ion chamber response signal and the ratio determining step includes determining the flux change based on a relative change in the ion chamber response signal over the predetermined interval. ICFD test method. 4. The method of claim 3, further comprising normalizing the ICFD response signal over the predetermined interval with respect to long-term pre and post step changes of the ICFD response signal. 4. The ICFD of claim 3, wherein determining the ratio comprises calculating an average ICFD response signal over a time interval following the predetermined interval and using the average ICFD to determine the relative change. Test Methods. 3. The method of claim 2, wherein the determining step includes determining an effective immediate fraction based on the measurement, further comprising incorporating a correction term based on modeling to change the effective immediate fraction based on the measurement, ICFD test method. 10. The method of claim 9, wherein the correction term includes a term for removing the effect of accumulated cleavage products. 2. The method of claim 1 wherein the step change comprises a reactor output trip. 2. The data acquisition system of claim 1, wherein the data acquisition system includes a plurality of subsystems, each receiving a subset of the response signal from the measurement device, wherein the receiving and recording comprises: receiving a clock signal from one of the subsystems; Providing to another of the subsystems. 13. The method of claim 12, wherein providing a clock signal comprises delivering the clock signal through a separation barrier. 13. The method of claim 12, wherein providing the clock signal further comprises providing a time confirmation signal. A system for testing an in-core flux detector (ICFD) in a reactor, the reactor having a mechanism to initiate a step change in reactor output. (a) a data acquisition system for receiving and recording a response signal from a measuring instrument comprising an ICFD; (b) an analysis module for determining an effective immediate fraction for the ICFD based on the recorded response signal Including ICFD test system. The ICFD test system of claim 15, wherein the effective immediate fraction comprises a ratio of the dynamic response of the ICFD and the flux change in the reactor. The ICFD test of claim 16, wherein the response signal comprises an ICFD response signal for the ICFD and the dynamic response comprises a relative change in the ICFD response signal over a predetermined interval following the step change. system. 18. The time according to claim 17, wherein the ICFD response signal comprises a delay component, each component having a time constant, and the predetermined interval is shorter than the shortest constant of the time constants. ICFD test system, including the term. The ICFD test system of claim 18, wherein the time period is less than about 3.9 seconds. 18. The ICFD test system of claim 17, wherein the response signal comprises an ion chamber response signal and the flux change comprises a relative change in the ion chamber response signal over the predetermined interval. 18. The ICFD test of claim 17, wherein the analysis module comprises a normalization module for normalizing the ICFD response signal over the predetermined interval to long term pre and post step changes of the ICFD response signal. system. 18. The apparatus of claim 17, wherein the analysis module comprises an average module for averaging the ICFD response signal over a time interval following the predetermined interval, wherein the analysis module comprises the average ICFD response signal to determine the relative change. Using, ICFD test system. 17. The ICFD test system of claim 16, wherein the analysis module determines an effective immediate fraction based on the measurement, and wherein the analysis module incorporates a correction term based on modeling to change the effective immediate fraction based on the measurement. 24. The ICFD test system of claim 23, wherein the correction term includes a term for removing the effect of accumulated long-term cleavage products. 16. The apparatus of claim 15, wherein the data acquisition system comprises: a separation amplifier for receiving the response signal and providing a separated signal; an adjustment module for adjusting the separated signal to output a adjusted signal; And a computer having an input for receiving a signal, the computer including a digitizer for digitizing the adjusted signal and a memory for storing the digitized signal. The system of claim 15, wherein the data acquisition system comprises one or more subsystems, each subsystem corresponding to one safety system channel, the reactor including one or more safety systems, and one of the subsystems Output a clock signal, and the other subsystem receives the clock signal. 27. The ICFD test system of claim 26, wherein the data acquisition system further comprises at least one isolation barrier in the path of the clock signal between the subsystems to separate the subsystems. 27. The ICFD test system of claim 26 wherein the separation barrier comprises an optical separator. 27. The ICFD test system of claim 26, wherein one of the subsystems outputs a time confirmation signal and the other subsystem receives the time confirmation signal. A computer readable recording medium having recorded thereon a computer program for tangibly embodying computer executable instructions for testing an in-core flux detector (ICFD) in a nuclear reactor, the reactor comprising a measuring device comprising the ICFD; Generates a response signal as a result of the step change in reactor output, wherein the computer executable command is  (a) computer-executable instructions for receiving and recording a response signal from the measuring instrument comprising an ICFD; (b) computer-executable instructions for determining an effective immediate fraction for the ICFD based on the recorded response signal, Computer-readable recording medium. 31. The computer program of claim 30, wherein the computer executable instructions for determining comprise computer executable instructions for determining a ratio of a dynamic response of the ICFD and a change in flux in the reactor. The computer of claim 31, wherein the response signal comprises an ICFD response signal for the ICFD, and wherein the dynamic response comprises a relative change in the ICFD response signal over a predetermined interval following the initiating step. Readable record carrier. 33. The time period following the onset of the step change of claim 32, wherein the ICFD response signal comprises a delay component, each component having a time constant, and wherein the predetermined interval is shorter than the shortest constant of the time constants. Computer-readable recording medium comprising a. 34. The computer program product of claim 33, wherein the time period is less than about 3.9 seconds. 33. The method of claim 32, wherein the response signal comprises an ion chamber response signal and the computer executable instructions for determining the ratio are based on the relative change in the ion chamber response signal over the predetermined interval. A computer readable recording medium comprising computer executable instructions for determining a change. 33. The computer program product of claim 32, further comprising computer executable instructions for normalizing the ICFD response signal over the predetermined interval to a long term post step change of the ICFD response signal. 33. The computer program product of claim 32, wherein the computer executable instructions for determining a ratio calculate an average ICFD response signal over a time interval following the predetermined interval and use the average ICFD to determine the relative change. And computer executable instructions for the computer readable recording medium. 32. The computer-implemented instruction of claim 31, wherein the computer executable instructions for determining comprise computer executable instructions for determining an effective immediate fraction based on the measurement, and modifying a correction term based on modeling to change the effective immediate fraction based on the measurement. And computer-executable instructions for integrating. 39. The computer program product of claim 38, wherein the correction term includes a term for removing the effect of accumulated long term delayed cleavage product.

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