CN103943158B - A kind of method eliminating self-power neutron detector late effect - Google Patents

A kind of method eliminating self-power neutron detector late effect Download PDF

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CN103943158B
CN103943158B CN201310754307.6A CN201310754307A CN103943158B CN 103943158 B CN103943158 B CN 103943158B CN 201310754307 A CN201310754307 A CN 201310754307A CN 103943158 B CN103943158 B CN 103943158B
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netron
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张清民
许孟轩
贺朝会
严俊
陈宇驰
吕志鹏
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Xian Jiaotong University
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Abstract

A kind of method eliminating self-power neutron detector late effect, writes out each intercalated nucleus prime number amount N in detector unit volumeiT (), about the dynamic differential equation group of netron-flux density φ (t) and probe current I (t) and the expression formula of each intercalated nucleus prime number amount and netron-flux density φ (t), obtains N by equation group and expression formula are convertedi(nTs) and Ni((n-1)Ts) and I ((n-1) Ts) relational expression, obtain φ (nT simultaneouslys) and Ni(nTs) and I (nTs) relational expression;Provide Ni(0), the initial value of I (0);It is sampled by measuring the electric current of neutron detector, obtains the measured value I of current samplem(nTs);Its process is obtained Is(nTs);Show that in next step circulation, in detector unit volume, each intercalated nucleus prime number amount and current slot eliminate the instantaneous value of the netron-flux density of time delay effect and export;Instant invention overcomes the current signal delay issue that half-life restriction brings;Introducing noise filtering makes it be more suitable for the complicated detection environment of reactor core;Without Laplace transformation, transform.

Description

A kind of method eliminating self-power neutron detector late effect
Technical field
The invention belongs to neutron detection technical field, be specifically related to a kind of method eliminating self-power neutron detector late effect.
Background technology
Nuclear energy is the most desired future source of energys of the mankind.In nuclear power reactor, netron-flux density is to embody the physical quantity of reactor capability and reactor state intuitively, and people control reactor by the mode of netron-flux density in control heap simultaneously.Due to the importance that particularity and the nuclear reactor safety of nuclear reactor run so that neutron detection is in vital status in reactor in the detection of various particles and ray.
Reactor core internal detection circumstance complication, it is higher to the requirement of neutron detector, it is desirable to irradiation high temperature resistant, resistance to, simple in construction, miniaturization.Neutron detector conventional at present can be divided into gas detector, semiconductor detector, scintillator detector and self-powered detector by its working mechanism.Although wherein gas detector irradiation high temperature resistant, resistance to, but the detection environment for piling interior High Temperature High Pressure is difficult to be competent at.Semiconductor detector is only applicable to measure the fast neutron spectrum of reactor, and existing thermal reactor using value is little.Scintillator detector is higher to the stability requirement of high voltage power supply, is difficult in reactor core.
And self-powered detector does not need the solidification little, all of applying bias, simple in construction, volume, electronics equipment simple etc. characteristic is so as to be particularly suitable for the detection of reactor core highneutronflux.But in current self-powered detector, mainly103Rh (rhodium) detector,51V (vanadium) detector and59Co (cobalt) detector, as shown in Figure 2, detector is placed in reactor core the detection principle of self-powered detector, and it through several different approaches ejected electrons, will can produce electric current in the loop after absorbing neutron when electronics is collected;This current intensity has relation with netron-flux density in heap, namely passes through to measure this electric current and pass it through certain to process the purpose by reaching to measure neutron flux.
In current self-powered detector,103The application of Rh detector is relatively broad, but due to103Rh and51The isotope that V element is formed after absorbing neutron in neutron field can decay with certain half-life, produces electronics (or gamma ray, gamma ray is by being changed into electronics with matter interaction) and forms the current signal of detector.Clearly as the restriction of half-life, current signal can not reflect the change of neutron flux in time.Such as, self-powered detector being put into suddenly in a constant neutron field, current signal needs a few minutes to can be only achieved stationary value.This does not obviously meet the requirement of monitor in real time of reactor core neutron flux.
Below with103Rh is that example illustrates the generation mechanism of detector current signal in neutron field.As in figure 2 it is shown, in the constituent of detector current, principle should include three parts: 1) Part I from103Rh absorbs the instantaneous generation of neutron (n, γ) reaction, and (gamma-rays that (n, γ) reflection discharges produces electronics with material generation photoelectric effect or Compton effect.This is the transient member of electric current;2) Part II from104mRh de excitation becomes104Electronics produced by gamma-rays and material generation photoelectric effect that Rh releases or Compton effect;3) Part III from104The electronics that Rh β decay produces.Rear two because the restriction of Rh half-life isotopes, belong to delay composition.
Rhodium self-powered detector was had much research by current lot of domestic and international scholar, draw a lot of achievements, simultaneously also have some shortcomings: 1) pertinent literature often contains only first and Part III, have ignored Part II, though Rh is not main component by this part, it is contemplated that revise the effect postponed, its effect can not be ignored;2) effect of noise is not accounted for when revising delay.Actually the current signal of this type of detector is only small, and noise is relatively big on its impact, so noise filtering must take into;3) method mentioned in document involves Laplace transformation, transform, has certain difficulty.
Summary of the invention
In order to solve above-mentioned prior art Problems existing, it is an object of the invention to provide a kind of method eliminating self-power neutron detector late effect, 1) overcome owing to the half-life limits the problem that the current signal brought postpones;2) introducing noise filtering makes it be more suitable for the complicated detection environment of reactor core;3) without Laplace transformation, transform;Fairly simple to a certain extent.
For reaching object above, the present invention adopts the following technical scheme that
A kind of method eliminating self-power neutron detector late effect, comprises the steps:
Step 1: draw its schematic diagram according to material for detector reaction physical process in neutron field;
Step 2: write out each intercalated nucleus prime number amount N in detector unit volume according to the response mechanism schematic diagram that step 1 drawsiT (), about the dynamic differential equation group (1) of netron-flux density φ (t), writes out the expression formula (2) of probe current I (t) and each intercalated nucleus prime number amount and netron-flux density φ (t);And the differential responses in neutron field produce the efficiency parameters of electric current to material species in the sensitivity of the transient member of neutron, detector unit volume and each middle nucleic to obtain the number of material species in detector unit volume, detector according to actual detector calibration data;
dNi(t)/dt=Fi(N1(t),....,Ni(t),....Nm(t),φ(t))(1)
I (t)=F (N1(t),....,Ni(t),....Nm(t),φ(t))(2)
In formula: i represents that i-th is correlated with nucleic;M represents total m relevant nucleic;T express time;
Step 3: the netron-flux density expression formula (2) drawn in step 2 is organized into the form of expression formula (3), probe current and the relation of each intercalated nucleus prime number amount it is expressed as by netron-flux density, owing to electric current deferred in electric current is all that middle nucleic decay produces, then only it is to be understood that deferred electric current can be eliminated the value of the wink generating stream obtaining energy direct reaction netron-flux density by each intercalated nucleus prime number order, expression formula (3) is brought in dynamic differential equation group (1) and obtain each intercalated nucleus prime number amount N in detector unit volumeiT () is about the dynamic differential equation group (4) of probe current I (t);
φ (t)=G (N1(t),....,Ni(t),....Nm(t),I(t))(3)
dNi(t)/dt=Gi(N1(t),....,Ni(t),....Nm(t),I(t))(4)
Step 4: by the dN in the dynamic differential equation group (4) that obtains in step 3iT ()/dt is write in time adjacent segments in detector unit volume as the difference of the quantity of each middle nucleic divided by step-length
(Ni(nTs)-Ni((n-1)Ts))/TsForm, NiT () is write as Ni((n-1)Ts) form, I (t) write as I ((n-1) Ts) form, TsFor the sample interval of detector current, i.e. sampling step length, n is step number;Obtain Ni(nTs) and Ni((n-1)Ts) relational expression (5);
Ni(nTs)=Gi(N1((n-1)Ts),....,Ni((n-1)Ts),....Nm((n-1)Ts),I((n-1)Ts))(5)
Step 5: provide each intercalated nucleus prime number amount N in detector unit volumei(t) and probe current I (t) the initial value N when time t=0iAnd I (0) (0), when putting into detector when shutdown and enable or enable detector suddenly when reactor firm power runs, Ni(0)=0, I (0)=0;When detector enables a period of time, initial value Ni(0) and I (0) take analog value according to different conditions;
Step 6: be sampled by the electric current of measurement neutron detector in reality is measured, obtain the measured value I of current samplem(nTs);
Step 7: the measured value I to current samplem(nTs) use the Adaptive adjusting algorithm of modified model kalman filtering to process, reduce effect of noise and prevent from smoothing sudden change;
The Adaptive adjusting algorithm of described modified model kalman filtering forms with condition adjudgement two parts by filtering;
(1) filtering: the measured value I to current samplem(nTs) carry out kalman Filtering Processing obtain kalman filter after current I (nTs);
(2) condition adjudgement: judge whether reactor system is in mutation status to prevent mutation current from being filtered out by kalman filtering system, its judgment rule is:
Kalman is utilized to filter after current I (nTs), contrast Im(nTs) and I (nTs) the absolute value of difference, see that whether it is more than threshold value;If greater than threshold value, then it represents that relatively larger fluctuation occurs in current signal, then judge that in reactor, neutron flux occurs in that sudden change, now by the measured value I of current samplem(nTs) it is assigned to output electric current Is(nTs) and export;If less than threshold value, then it represents that current signal fluctuation is smaller, then judge that now fluctuation is to be caused by noise, then directly kalman is filtered after current I (nTs) value be assigned to output electric current Is(nTs) and export;
Step 8: the current value I that step 7 is exporteds(nTs) walk each intercalated nucleus prime number amount N in detector unit volume with currenti(nTs) it is brought into N respectivelyi((n+1)Ts)=Hi(N1(nTs),....,Ni(nTs),....Nm(nTs),Is(nTs)) and φ (nTs)=G (N1(nTs),....,Ni(nTs),....Nm(nTs),Is(nTs)) in, draw in next step circulation each intercalated nucleus prime number amount N in detector unit volumei((n+1)Ts) and current slot eliminate time delay effect netron-flux density φ (nTs) instantaneous value;By φ (nTs) output, return step 6 simultaneously.
Threshold value described in step 7 takes three times of noise criteria difference.
Compared with prior art, present invention have the advantage that
Step 2 considers the reaction likely producing electric current, has stopped to cause revising owing to ignoring small area analysis the consequence of the carryover effects bigger error of generation, has made the effect that correction postpones truer.
Step 3-step 5 is simple Mathematical treatment and iterative process, and relative to carrying out Laplace transformation and transform process, process is simple to operation.
Step 6 considers effect of noise can simulate detection environment complicated in heap more realistically
Step 7 has carried out noise filtering, takes modified model kalman filtering algorithm, can realize noise filtering, can prevent mutation status from being caused the generation of signal delay by filtering when sudden change again.
Accompanying drawing explanation
Fig. 1 is schematic flow sheet of the present invention.
Fig. 2 is detector detection neutron correlated response procedure chart.
Fig. 3 is normalization output netron-flux density and normallized current figure.
Fig. 4 is normalization netron-flux density and normallized current figure before and after sudden change.
Detailed description of the invention
Below in conjunction with drawings and the specific embodiments, the present invention is described in further detail.
It is described in detail for rhodium self-power neutron detector below: concrete grammar process is as shown in Figure 1.
Step 1: according to material for detector103Rh reaction physical process in neutron field draws its schematic diagram, as shown in Figure 2.
Step 2: write out in detector unit volume according to Fig. 2104mThe number N of Rh1(t) and104The number N of Rh2T () is about the dynamic differential equation (1-1) of netron-flux density φ (t) and (1-2), and write out probe current I (t) and N1(t)、N2The expression formula (2-1) of (t) and netron-flux density φ (t).
dN 1 ( t ) d t = σ 1 N R h 103 φ ( t ) - λ 1 N 1 ( t ) ... ( 1 - 1 )
dN 2 ( t ) d t = σ 2 N R h 103 φ ( t ) + λ 1 N 1 ( t ) - λ 2 N 2 ( t ) ... ( 1 - 2 )
I ( t ) = ( f 1 σ 1 N R h 103 + f 2 σ 2 N R h 103 ) φ ( t ) + j 1 λ 1 N 1 ( t ) + j 2 λ 2 N 2 ( t ) ... ( 2 - 1 )
Wherein:
For in detector unit volume103The number of Rh nucleic;
N1T () is in detector unit volume104mThe number of Rh;
N2T () is in detector unit volume104The number of Rh;
σ1For103Rh generates with neutron reaction104mThe microreaction cross section of Rh;
σ2For103Rh generates with neutron reaction104The microreaction cross section of Rh;
λ1For104mThe decay constant of Rh;
λ2For104The decay constant of Rh;
f1With f2Respectively produce (n, γ) reaction in detector unit volume to generate104mRh and104Two reaction channels of Rh and photoelectric effect thereof produce the efficiency of transient current;
For the detector sensitivity to the transient member of neutron;
j1For in detector unit volume104mRh de excitation becomes104The gamma-rays of Rh releasing and the current generating efficiency of material generation photoelectric effect or Compton effect;
j2For in detector unit volume104Rh β decay produces the efficiency of electric current;
φ (t) is netron-flux density;
I (t) is probe current;
Step 3: the probe current drawn in step 2 and netron-flux density expression formula (2-1) are organized into φ (t)=G ((N1(t),....,Ni(t),....Nm(t), I (t)) form, probe current and the relation of each intercalated nucleus prime number amount it is expressed as by netron-flux density, owing to electric current deferred in electric current is all that middle nucleic decay produces, then only it is to be understood that deferred electric current can be eliminated the value of the wink generating stream obtaining energy direct reaction netron-flux density by each intercalated nucleus prime number order, such as (3-1);Expression formula (3) is brought into the dynamic differential equation group (1-1) (1-2) that step 2 is obtained obtains each intercalated nucleus prime number amount N in detector unit volumeiT () is about the dynamic differential equation group dN of probe current I (t)i(t)/dt=Gi(N1(t),....,Ni(t),....Nm(t),I(t)),
Such as (4-1), (4-2).
φ ( t ) = 1 f 1 Σ 1 + f 2 Σ 2 [ I ( t ) - j 1 λ 1 N 1 ( t ) - j 2 λ 2 N 2 ( t ) ] ... ( 3 - 1 )
dN 1 ( t ) d t = Σ 1 f 1 Σ 1 + f 2 Σ 2 [ I ( t ) - j 1 λ 1 N 1 ( t ) - j 2 λ 2 N 2 ( t ) ] - λ 1 N 1 ( t ) ... ( 4 - 1 )
dN 2 ( t ) d t = Σ 2 f 1 Σ 1 + f 2 Σ 2 [ I ( t ) - j 1 λ 1 N 1 ( t ) - j 2 λ 2 N 2 ( t ) ] + λ 1 N 1 ( t ) - λ 2 N 2 ( t ) ... ( 4 - 2 )
Wherein:
Generate for producing (n, γ) reaction in detector unit volume104mThe macroscopic cross section of Rh;
Generate for producing (n, γ) reaction in detector unit volume104The macroscopic cross section of Rh;
N1T () is in detector unit volume104mThe number of Rh;
N2T () is in detector unit volume104The number of Rh;
λ1For104mThe decay constant of Rh;
λ2For104The decay constant of Rh;
f1With f2Respectively produce (n, γ) reaction in detector unit volume to generate104mRh and104Two reaction channels of Rh and photoelectric effect thereof produce the efficiency of transient current;
j1For in detector unit volume104mRh de excitation becomes104The gamma-rays of Rh releasing and the current generating efficiency of material generation photoelectric effect or Compton effect;
j2For in detector unit volume104Rh β decay produces the efficiency of electric current;
φ (t) is netron-flux density;
I (t) is probe current;
Step 4: by the dN in the dynamic differential equation group (4-1) obtained in step 3, (4-2)iT ()/dt is write as the current step place time period with the difference of the quantity of each middle nucleic in the time period detector unit volume of previous step place divided by step-length (Ni(nTs)-Ni((n-1)Ts))/TsForm, NiT () is write as Ni((n-1)Ts) form, I (t) write as I ((n-1) Ts) form, TsFor the sample interval of detector current, i.e. sampling step length, n is step number;Obtain Ni(nTs) and Ni((n-1)Ts) relation (5);
Ni(nTs)=Gi(N1((n-1)Ts),....,Ni((n-1)Ts),....Nm((n-1)Ts),I(nTs))(5)
Detailed process is as follows: the differential form of equation in step 3 is expressed as the adjacent value form divided by step-length, such as (3-1-1), (4-1-1), (4-2-1);The relational expression then obtained in step 3 just can represent the coupled relation between the relevant parameter between adjacent step sizes, such as (5-1), (5-2).
φ ( ( n - 1 ) T s ) = 1 f 1 Σ 1 + f 2 Σ 2 [ I ( ( n - 1 ) T s ) - j 1 λ 1 N 1 ( ( n - 1 ) T s ) - j 2 λ 2 N 2 ( ( n - 1 ) T s ) ] - - - ( 3 - 1 - 1 )
N 1 ( nT s ) - N 1 ( ( n - 1 ) T s ) T s = Σ 1 f 1 Σ 1 + f 2 Σ 2 [ I ( ( n - 1 ) T s ) - j 1 λ 1 N 1 ( ( n - 1 ) T s ) - j 2 λ 2 N 2 ( ( n - 1 ) T s ) ] - λ 1 N 1 ( ( n - 1 ) T s ) ... ( 4 - 1 - 1 )
N 1 ( nT s ) - N 1 ( ( n - 1 ) T s ) T s = Σ 2 f 1 Σ 1 + f 2 Σ 2 [ I ( ( n - 1 ) T s ) - j 1 λ 1 N 1 ( ( n - 1 ) T s ) - j 2 λ 2 N 2 ( ( n - 1 ) T s ) ] + λ 1 N 1 ( ( n - 1 ) T s ) - λ 2 N 2 ( ( n - 1 ) T s ) ... ( 4 - 2 - 1 )
Obtain
N 1 ( nT s ) = T s Σ 1 f 1 Σ 1 + f 2 Σ 2 I ( ( n - 1 ) T s ) + [ 1 - T s λ 1 ( 1 + j 1 Σ 1 f 1 Σ 1 + f 2 Σ 2 ) ] N 1 ( ( n - 1 ) T s ) - T s Σ 1 j 2 λ 2 f 1 Σ 1 + f 2 Σ 2 N 2 ( ( n - 1 ) T s ) ... ( 5 - 1 )
N 2 ( nT s ) = T s Σ 2 f 1 Σ 1 + f 2 Σ 2 I ( ( n - 1 ) T s ) + T s λ 1 ( 1 - j 1 Σ 2 f 1 Σ 1 + f 2 Σ 2 ) N 1 ( ( n - 1 ) T s ) - T s λ 2 ( 1 + Σ 2 j 2 f 1 Σ 1 + f 2 Σ 2 ) N 2 ( ( n - 1 ) T s ) ... ( 5 - 2 )
Wherein:
Generate for producing (n, γ) reaction in detector unit volume104mThe macroscopic cross section of Rh;
Generate for producing (n, γ) reaction in detector unit volume104The macroscopic cross section of Rh;
TsFor sampling step length;
N1(nTs) it is in current step place time period detector unit volume104mThe number of Rh;
N2(nTs) it is in current step place time period detector unit volume104The number of Rh;
I(nTs) it is the current probe current walking the place time period;
N1((n-1)Ts) in the time period detector unit volume of previous step place104mThe number of Rh;
N2((n-1)Ts) in the time period detector unit volume of previous step place104The number of Rh;
I((n-1)Ts) for the probe current of previous step place time period;
λ1For104mThe decay constant of Rh;
λ2For104The decay constant of Rh;
f1With f2Respectively produce (n, γ) reaction in detector unit volume to generate104mRh and104Two reaction channels of Rh and photoelectric effect thereof produce the efficiency of transient current;
j1For in detector unit volume104mRh de excitation becomes104The gamma-rays of Rh releasing and the current generating efficiency of material generation photoelectric effect or Compton effect;
j2For in detector unit volume104Rh β decay produces the efficiency of electric current;
φ((n-1)Ts) for the netron-flux density of previous step place time period;
Then only it is to be understood that be currently located the time period104mRh and104Number and the current measured electric current of Rh can draw the next time period104mRh and104The number of Rh.
Step 5: provide each intercalated nucleus prime number amount N in detector unit volumei(t) and probe current I (t) the initial value N when time t=0iAnd I (0) (0), when putting into detector when shutdown and enable or enable detector suddenly when reactor firm power runs, Ni(0)=0, I (0)=0;When detector enables a period of time, initial value Ni(0) and I (0) take analog value according to different conditions.
Detailed process is: make t=0 moment parameter N1(t)、N2T the value of () is 0, put into detector and enable or enable suddenly the situation of detector when reactor firm power runs during simulation shutdown.
Step 6: be sampled by the electric current of measurement neutron detector in reality is measured, obtain the measured value I of current samplem(nTs)。
Detailed process: sampling step length alternate constant;Simultaneously in order to simulate truth better, then adding the white Gaussian noise measured value as actual samples on the basis of the theoretical current value got, white Gaussian noise is the noise of the distribution Gaussian distributed formed of being superimposed by the noise of all frequencies.
Step 7: the measured value I to current samplem(nTs) use the Adaptive adjusting algorithm of modified model kalman filtering to process, reduce effect of noise and prevent from smoothing sudden change;
The Adaptive adjusting algorithm of described modified model kalman filtering forms with condition adjudgement two parts by filtering.
(1) filtering: the measured value I to current samplem(nTs) carry out kalman Filtering Processing obtain kalman filter after current I (nTs)。
The concrete processing mode of kalman filtering is:
A () utilizes previous step filtered electric current I ((n-1) Ts) predict current step electric current Iy(nTs);Because the effect of kalman system herein is filtering, so order current step predicted current is equal to the filtered electric current of previous step.
I.e. Iy(nTs)=I ((n-1) Ts)……………………………………………(6-1)
Wherein: Iy(nTs) for currently walking predicted current;I ((n-1) Ts) for the filtered electric current of previous step.
B () utilizes covariance P ((n-1) T of previous step filtering after currents) predict the current covariance P walking predicted currenty(nTs).Owing to there is procedures system noise, so the covariance currently walking predicted current also needs to add the covariance Q of systematic procedure noise.
I.e. Py(nTs)=P ((n-1) Ts)+Q…………………………………………(6-2)
Wherein: Py(nTs) it is the current covariance walking predicted current;P ((n-1) Ts) for previous step filter after current covariance;Q is the covariance of procedures system noise.
C () has been obtained for the I that predicts the outcome of current statey(nTs), also there is the measured value I that current flow is sampledm(nTs);Current value I (the nT after kalman filtering can be obtaineds)
I(nTs)=Iy(nTs)+Kg(nTs)×(Im(nTs)-Iy(nTs))………………………(6-3)
Wherein Im(nTs) for the measured value of current sample;Iy(nTs) for currently walking predicted current;I (nTs) for kalman filter after current value;Kg (nTs) it is the current kalman gain walked;
And Kg (nTs)=Py(nTs)/(Py(nTs)+R)…………………………………(6-4)
Wherein Py(nTs) it is the current covariance walking predicted current;R is owing to measurement system exists the covariance of the measurement system noise that noise introduces.
D () to make kalman filtering continue to run with at next step, in addition it is also necessary to update the covariance P (nT filtering after current under current states)。
P(nTs)=(1-Kg (nTs))×Py(nTs)………………………………………(6-5)
Wherein Py(nTs) it is the current covariance walking predicted current;Kg (nTs) it is the current kalman gain walked;
P(nTs) for filtering the covariance of after current under current state.
(2) condition adjudgement: judge whether reactor system is in mutation status to prevent mutation current from being filtered out by kalman filtering system, its judgment rule is:
Electric current I (the nT obtained after utilizing kalman filterings), contrast Im(nTs) and I (nTs) the absolute value of difference, see that whether it is more than threshold value, wherein threshold value generally takes three times of noise criteria difference, according to practical situation many relatively some steps suitably forward, to prevent erroneous judgement, and the method can be made to have higher reliability simultaneously;If greater than threshold value, then it represents that relatively larger fluctuation occurs in current signal, then judge that in heap, neutron flux occurs in that sudden change, now by the measured value I of current samplem(nTs) it is assigned to output electric current IsAnd export (nTs);If less than threshold value, then it represents that current signal fluctuation is smaller, then judge that now fluctuation is to be caused by noise, then the value that kalman directly filters after current I (nTs) is assigned to output electric current IsAnd export (nTs).
Step 8: the current value I that step 7 is exporteds(nTs) each intercalated nucleus prime number amount N in detector unit volume and is currently walkedi(nTs) it is brought into Ni((n+1)Ts)=Hi(N1(nTs),....,Ni(nTs),....Nm(nTs),Is(nTs)) in draw next step circulation in detector unit volume in each intercalated nucleus prime number amount Ni((n+1)Ts);It is brought into φ (nT agains)=G (N1(nTs),....,Ni(nTs),....Nm(nTs),Is(nTs)) in obtain current slot eliminate time delay effect netron-flux density φ (nTs) instantaneous value.
Concrete substitution formula is as follows:
N 1 ( ( n + 1 ) T s ) = T s Σ 1 f 1 Σ 1 + f 2 Σ 2 I s ( nT s ) + [ 1 - T s λ 1 ( 1 + j 1 Σ 1 f 1 Σ 1 + f 2 Σ 2 ) ] N 1 ( nT s ) - T s Σ 1 j 2 λ 2 f 1 Σ 1 + f 2 Σ 2 N 2 ( nT s ) ... ( 5 - 1 - 1 )
N 2 ( ( n + 1 ) T s ) = T s Σ 2 f 1 Σ 1 + f 2 Σ 2 I s ( nT s ) + T s λ 1 ( 1 - j 1 Σ 2 f 1 Σ 1 + f 2 Σ 2 ) N 1 ( nT s ) - T s λ 2 ( 1 + Σ 2 j 2 f 1 Σ 1 + f 2 Σ 2 ) N 2 ( nT s ) - - - ( 5 - 1 - 2 )
φ ( nT s ) = 1 f 1 Σ 1 + f 2 Σ 2 [ I s ( nT s ) - j 1 λ 1 N 1 ( nT s ) - j 2 λ 2 N 2 ( nT s ) ] ... ( 3 - 1 - 1 - 1 )
Wherein:
Generate for producing (n, γ) reaction in detector unit volume104mThe macroscopic cross section of Rh;
Generate for producing (n, γ) reaction in detector unit volume104The macroscopic cross section of Rh;
TsFor sampling step length;
N1(nTs) it is in current step place time period detector unit volume104mThe number of Rh;
N2(nTs) it is in current step place time period detector unit volume104The number of Rh;
Is(nTs) it is the current output electric current walking the place time period;
N1((n+1)Ts) in next step place time period detector unit volume104mThe number of Rh;
N2((n+1)Ts) in next step place time period detector unit volume104The number of Rh;
λ1For104mThe decay constant of Rh;
λ2For104The decay constant of Rh;
f1With f2Respectively produce (n, γ) reaction in detector unit volume to generate104mRh and104Two reaction channels of Rh and photoelectric effect thereof produce the efficiency of transient current;
j1For in detector unit volume104mRh de excitation becomes104The gamma-rays of Rh releasing and the current generating efficiency of material generation photoelectric effect or Compton effect;
j2For in detector unit volume104Rh β decay produces the efficiency of electric current;
φ(nTs) it is the current netron-flux density walking the place time period;
Value illustrates:
104mThe half-life of Rh is 258.0 seconds, then104mThe decay constant of Rh
104The half-life of Rh is 42.4 seconds;Then104The decay constant of Rh
103Rh generates with neutron reaction104mThe microreaction cross section σ of Rh1=1.1 × 10-23cm2
103Rh generates with neutron reaction104The microreaction cross section σ of Rh2=1.35 × 10-22cm2
Owing to the time span investigated is much smaller than the life length of detector, it is assumed that investigating in the time period in detector unit volume103The number of Rh nucleic remains unchanged, namelyFor constant;Owing to the density of rhodium is 12.7g/cm3, then unit volume is contained within103The number of RhHere ρ=12.7g/cm3Density for rhodium;M=103g/mol is the molal weight of rhodium, NA=6.02 × 1023mol-1For Avogadro's number.Then produce (n, γ) reaction in detector unit volume to generate104mRh and104The macroscopic cross section of Rh is respectively Σ 1 = σ 1 N R h 103 = 0.8165 cm - 1 , Σ 2 = σ 2 N R h 103 = 10.0207 cm - 1 .
The sensitivity representative value of the neutron of rhodium self-power neutron detector is 3.6 × 10-20A/ (cm*s), wherein transient member accounting is about 5%~15%, takes 10%, namely herein j1With j2Value will be tuned determining according to detector scale value in actual application;Here take j for the time being1=2.9897 × 10-22A/(cm3*s),j2=2.9897 × 10-21A/(cm3* s);Sampling step length TsCan be optimized as the case may be, be taken as temporarily here 0.1 second.
In kalman filtering system the value of Q and R because of system different and different, for P (0) if value be 0 mean that kalman system is optimum; algorithm could be made not restrain, and the increase along with n is converged on 0 by P (n) gradually, then can take P (0) is a random positive integer, here take Q=0.0001, R=0.0004, I (0)=0, P (0)=10.
Application example:
In order to highlight the effect eliminating time delay, rhodium detector is put into suddenly the process of a stable neutron field by examination, it is generally recognized that time delay be reach steady-state value 95% needed for time.Heap process is opened, netron-flux density φ=0 (cm in mock-up reactor for reactor2·s)-1When the t=100 second to suddenly becoming φ=5 × 1013(cm2·s)-1Process;The whole 100 seconds netron-flux density φ=0 (cm in Cheng Qian excessively2·s)-1, when the 100th second, netron-flux density sported φ=5 × 1013(cm2·s)-1, and maintain always.In this simulation process, each relevant parameter carries out value, current sampling time step T with reference to situation described in detailed description of the invention and value declarativess=0.1 second, simultaneously in order to simulate truth better, so add on the basis of the theoretical current value got average be 0, standard deviation sigma=1 × 10-8The impact of the white Gaussian noise that A (accounts for the 1% of steady-state current) is as actual surveyed electric current;Judge that noise states or the threshold value of mutation status are 3 σ.
Eliminate the result of late effect as shown in Figures 3 and 4, including the time dependent curve of normalization netron-flux density and normallized current.Normalization netron-flux density be the netron-flux density that draws with elimination delay algorithm with sudden change after the ratio of netron-flux density (normalization denominator takes 5 × 1013(cm2·s)-1);Normallized current is the ratio of the stationary value that value and the electric current of the electric current of the existence noise recorded is finally reached;Can be seen that electric current needs the time of more than 300 seconds can be only achieved in figure 3 stable, namely will there is very big delay iff the words showing netron-flux density according to current data, if adopting in this way, the monitoring of Reactor Neutron Flux Density is lost meaning;In contrast, the netron-flux density that elimination delay algorithm draws is adopted to coincide very good with actual netron-flux density, the process of the front and back that suddenly change in Fig. 3 is intercepted out as Fig. 4 simultaneously, can be seen that in the diagram delay within being controlled in short 0.1 second (even if for higher reliability, consider that a few step of many forward prediction is to judge that noise still suddenlys change, it also is able to well control within 1 second), the monitor in real time of Reactor Neutron Flux Density can be achieved, be more conducive to reactor safety control.
Although with reference to exemplary embodiment describing the present invention, it is to be understood that term used is to illustrate and exemplary and nonrestrictive term.The spirit without deviating from invention and essence can be embodied as in a variety of forms due to the present invention, it is to be understood that, above-described embodiment is not limited to any aforesaid details, and should explain widely in the spirit and scope that appended claims limit, therefore fall into the whole changes in claim or its equivalent scope and remodeling all should be appended claims and covered.

Claims (2)

1. the method eliminating self-power neutron detector late effect, it is characterised in that: comprise the steps:
Step 1: draw its schematic diagram according to material for detector reaction physical process in neutron field;
Step 2: write out each intercalated nucleus prime number amount N in detector unit volume according to the response mechanism schematic diagram that step 1 drawsiT (), about the dynamic differential equation group (1) of netron-flux density φ (t), writes out the expression formula (2) of probe current I (t) and each intercalated nucleus prime number amount and netron-flux density φ (t);And the differential responses in neutron field produce the efficiency parameters of electric current to material species in the sensitivity of the transient member of neutron, detector unit volume and each middle nucleic to obtain the number of material species in detector unit volume, detector according to actual detector calibration data;
dNi(t)/dt=Fi(N1(t),....,Ni(t),....Nm(t),φ(t))(1)
I (t)=F (N1(t),....,Ni(t),....Nm(t),φ(t))(2)
In formula: i represents that i-th is correlated with nucleic;M represents total m relevant nucleic;T express time;
Step 3: the netron-flux density expression formula (2) drawn in step 2 is organized into the form of expression formula (3), probe current and the relation of each intercalated nucleus prime number amount it is expressed as by netron-flux density, owing to electric current deferred in electric current is all that middle nucleic decay produces, then only it is to be understood that deferred electric current can be eliminated the value of the wink generating stream obtaining energy direct reaction netron-flux density by each intercalated nucleus prime number order, expression formula (3) is brought in dynamic differential equation group (1) and obtain each intercalated nucleus prime number amount N in detector unit volumeiT () is about the dynamic differential equation group (4) of probe current I (t);
φ (t)=G (N1(t),....,Ni(t),....Nm(t),I(t))(3)
dNi(t)/dt=Gi(N1(t),....,Ni(t),....Nm(t),I(t))(4)
Step 4: by the dN in the dynamic differential equation group (4) that obtains in step 3iT ()/dt is write in the neighbouring sample point time period in detector unit volume as the difference of the quantity of each middle nucleic divided by step-length (Ni(nTs)-Ni((n-1)Ts))/TsForm, NiT () is write as Ni((n-1)Ts) form, I (t) write as I ((n-1) Ts) form, TsFor the sample interval of detector current, i.e. sampling step length, n is step number;Obtain Ni(nTs) and Ni((n-1)Ts) relational expression (5);
Ni(nTs)=Gi(N1((n-1)Ts),....,Ni((n-1)Ts),....Nm((n-1)Ts),I((n-1)Ts))(5)
Step 5: provide each intercalated nucleus prime number amount N in detector unit volumei(t) and probe current I (t) the initial value N when time t=0iAnd I (0) (0), when putting into detector when shutdown and enable or enable detector suddenly when reactor firm power runs, Ni(0)=0, I (0)=0;When detector enables a period of time, initial value Ni(0) and I (0) take analog value according to different conditions;
Step 6: be sampled by the electric current of measurement neutron detector in reality is measured, obtain the measured value I of current samplem(nTs);
Step 7: the measured value I to current samplem(nTs) use the Adaptive adjusting algorithm of modified model kalman filtering to process, reduce effect of noise and prevent from smoothing sudden change;
The Adaptive adjusting algorithm of described modified model kalman filtering forms with condition adjudgement two parts by filtering;
(1) filtering: the measured value I to current samplem(nTs) carry out kalman Filtering Processing obtain kalman filter after current I (nTs);
(2) condition adjudgement: judge whether reactor system is in mutation status to prevent mutation current from being filtered out by kalman filtering system, its judgment rule is:
Kalman is utilized to filter after current I (nTs), contrast Im(nTs) and I (nTs) the absolute value of difference, see that whether it is more than threshold value;If greater than threshold value, then it represents that relatively larger fluctuation occurs in current signal, then judge that in reactor, neutron flux occurs in that sudden change, now by the measured value I of current samplem(nTs) it is assigned to output electric current Is(nTs) and export;If less than threshold value, then it represents that current signal fluctuation is smaller, then judge that now fluctuation is to be caused by noise, then directly kalman is filtered after current I (nTs) value be assigned to output electric current Is(nTs) and export;
Step 8: the current value I that step 7 is exporteds(nTs) walk each intercalated nucleus prime number amount N in detector unit volume with currenti(nTs) it is brought into N respectivelyi((n+1)Ts)=Hi(N1(nTs),....,Ni(nTs),....Nm(nTs),Is(nTs)) and φ (nTs)=G (N1(nTs),....,Ni(nTs),....Nm(nTs),Is(nTs)) in, draw in next step circulation each intercalated nucleus prime number amount N in detector unit volumei((n+1)Ts) and current slot eliminate time delay effect netron-flux density φ (nTs) instantaneous value;By φ (nTs) output, return step 6 simultaneously.
2. method according to claim 1, it is characterised in that: the threshold value described in step 7 takes three times of noise criteria difference.
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