阅读说明：本技术 利用源量程探测器信号作为信号源的次临界刻棒方法 (Subcritical rod carving method using source range detector signal as signal source ) 是由 卢迪 彭星杰 廖鸿宽 李向阳 于颖锐 王丹 蒋朱敏 肖鹏 刘同先 关仲华 于 2020-04-07 设计创作，主要内容包括：本发明公开了利用源量程探测器信号作为信号源的次临界刻棒方法,是一种能够在反应堆处于较深次临界时进行控制棒价值测量的方法,记录某一控制棒组提出或插入堆芯后堆芯处于待测状态时源量程探测器中子计数率信号,调取次临界修正因子,经次临界修正因子修正源量程探测器中子计数率信号,再采用修正后的信号进行与基准状态源量程探测器计数率及反应性作对比,最终获得各待测状态下的堆芯反应性,完成刻棒,在保障测量精度的同时,可有效降低经济成本。(The invention discloses a subcritical rod-carving method by using a source range detector signal as a signal source, which is a method capable of measuring the value of a control rod when a reactor is in a deeper subcritical state.)

1. The subcritical rod carving method using the source range detector signal as the signal source is characterized by comprising the following steps of:

s1, establishing a subcritical correction factor library: the subcritical correction factor library comprises subcritical correction factors at specified rod positions of each control rod group in a state to be detected;

s2, obtaining value measurement measured values of each control rod group:

s2-1, collecting the counting rate of the source range detector in the reference state, adjusting the ground rod position of the control rod X rod group to the rod position specified in the reference state, and obtaining the counting rate of the neutrons in the source range detector in the reference stateWherein X represents the number of the bar group to be detected;

s2-2, collecting the counting rate of the source range detector in the state to be detected, lifting the rod position of the control rod X rod group to the top of the reactor core or inserting the control rod X rod group into the bottom of the reactor core, and obtaining the neutron counting rate signals of the source range detector when the X rod group to be detected in the state to be detected is lifted or inserted into the reactor core behind the reactor core, wherein the signals are respectively the neutron counting rate signals of the source range detector

S2-3, when the X-bar group is in the proposed state, calling the corresponding subcritical correction factor C in the subcritical correction factor library according to the control bar position signal_target-Out(X), calculating the reactor core subcritical degree when the X rod group to be measured in the state to be measured is lifted to the top of the reactor core according to the formula (1)

S2-4, when the X-bar group is in the inserting state, calling subcritical correction according to the control bar position signalCorresponding subcritical correction factor C in factor library_target-In(X), calculating the reactor core subcritical degree when the X rod group to be measured is inserted into the reactor core bottom in the state to be measured according to the formula (2)

S2-5, obtaining the control rod integral value of the X rod group to be measured according to the formula (3)

Wherein the content of the first and second substances,representing the neutron count rate of the source range detector in a reference state,representing the reactor core baseline state reactivity; the reactor core reference state reactivity and the subcritical correction factor of each control rod group at the specified rod position under the state to be measured are obtained through modeling calculation.

2. The subcritical scribe bar method using source-wide range probe signals as signal sources of claim 1 wherein said reference state reactivity is obtained by: calculating the finite multiplication coefficient k of the reactor core in the reference state by simulating the reference state of the reactor core_effAnd (3) calculating the reactivity of the reactor core in the reference state by adopting a formula (4):

3. the subcritical scribe bar method using source range detector signals as signal sources of claim 1 wherein the subcritical correction factor is obtained by:

s1-1, aiming at a reactor to be developed with a subcritical rod carving, establishing a corresponding shielding calculation model, and utilizing neutron shielding calculation software to perform corresponding calculation on a source range detector, so as to obtain the response relation of each source range detector to a fission neutron source in the reactor and obtain the response factor of each position in the three-dimensional space of the reactor core;

s1-2, establishing a reactor physical calculation model according to a specific nuclear fuel loading scheme of the reactor;

s2-3, on the basis of the step S1-2, according to the reference state involved in the subcritical rod engraving test, considering the influence of an external source on the neutron flux distribution of the reactor core in the subcritical state, and calculating to obtain the neutron flux distribution, the fundamental wave flux distribution and the fundamental wave conjugate flux distribution of the reactor corresponding to the reference state;

s2-4, on the basis of the step S1-2, according to each state to be tested involved in the subcritical rod carving test, considering the influence of an external source on the neutron flux distribution of the reactor core in the subcritical state, and calculating to obtain the neutron flux distribution, the fundamental wave flux distribution and the fundamental wave conjugate flux distribution of the reactor corresponding to each state to be tested;

s2-5, processing the response factor, the reactor neutron flux distribution, the fundamental wave flux distribution and the fundamental wave conjugate flux distribution aiming at each state to be tested on the basis of the steps S1-1, S1-2 and S1-3, and calculating the subcritical correction factor of each control rod group at the specified rod position in the state to be tested.

4. The subcritical rod engraving method using source range detector signals as signal sources according to claim 3, wherein in S1-1, the response relationship of each source range detector to a fission neutron source in a reactor is the response relationship of point to point in a three-dimensional space, which can be expressed as a three-dimensional function, and the division of energy groups is performed according to the requirement of establishing a reactor physical calculation model in S1-2, so as to give response factors of each position in a three-dimensional space of a core under each energy group.

5. The subcritical rod engraving method using source range detector signals as signal sources according to claim 3, wherein in S2-3 and S2-2, reactor neutron flux distribution, fundamental wave flux distribution and fundamental wave conjugate flux distribution corresponding to a reference state are obtained through calculation of pressurized water reactor steady-state core calculation software; the pressurized water reactor steady state core calculation software includes MEACOR software.

Technical Field

The invention relates to the technical field of physical test methods of nuclear reactors, in particular to a subcritical rod carving method using a source range detector signal as a signal source.

Background

At present, a mainstream pressurized water reactor nuclear power plant adopts a batch refueling mode to replace reactor fuel, when the refueling period (generally every other year or half and a year) reaches the end of the service life, the nuclear fuel with deeper internal combustion consumption in the reactor is discharged out of a reactor core, and meanwhile, a corresponding number of new fuel assemblies are loaded into the reactor core, so that the reactor core has enough reactivity again to maintain the critical and energy output of the reactor core. Due to the large difference in the physical properties of the new and old fuels, the reactor must re-design the fuel loading scheme and perform the related thermal safety analysis, so the nuclear power plant usually needs to entrust the design unit with the related qualification to design the new fuel loading scheme before each fuel replacement.

After the nuclear power plant completes the loading and unloading operation according to the fuel loading scheme provided by the design unit, in order to verify the correctness of the loading scheme provided by the design unit based on the design software, a reactor starting physical test is required before the nuclear power plant generates power again. Because the physical starting test is carried out in a state that the power of the reactor is almost zero, the nuclear power plant can not output electric energy outwards in the whole test stage, and economic benefit is not generated. From the perspective of safe operation of a nuclear power plant, a physical starting test is indispensable, but from the perspective of improving economy, the nuclear power plant needs to be continuously created and improved to shorten the time occupied by the physical starting test. Among all the starting physical test items, the time taken for the notch test, i.e., the control rod value measurement test, is long. Therefore, the research on the rapid control rod value measuring method has very important significance for improving the economy of the nuclear power plant. Common rod value measuring methods include a boron dilution/boronization measurement + rod engraving method, a dynamic rod engraving test method and a subcritical rod engraving method, and specific descriptions are provided below.

1. Method for' boron dilution/boronization measurement + rod engraving

In a rod engraving test of a nuclear power plant, a method of 'boron dilution/boronization measurement + rod engraving' is adopted in the traditional rod value measurement. Firstly, a boron dilution/boronization measurement method is adopted to measure the differential/integral value of the control rod group with the maximum integral reactivity value, and then a rod engraving method is adopted to measure the differential/integral value of other rod groups, and the traditional rod value measurement method has the following defects: on one hand, because instruments adopted for measuring the reactivity are all established on the basis of the theoretical assumption of a point reactor model, in order to ensure the applicability of the theoretical assumption of a test process, the reactivity required to be introduced once in the test process cannot be too high, so that the measurement efficiency of the control rod value in the test is limited to a great extent, and the measurement test is very time-consuming; on the other hand, the adoption of the boron dilution/boronization measurement method is time-consuming and can generate a large amount of boron wastewater, further influencing the economy of the nuclear power plant.

2. Dynamic rod carving test method

A dynamic rod-carving test method is a test method for quickly measuring the value of a control rod, which is originally developed by American West House electric company, and the method quantitatively calculates the degree of deviation from a point stack model in the whole test process by high-precision computer numerical simulation of the test process before the test and introduces correction factors to solve the measurement deviation caused by the deviation from the point stack model in the test. The method is not limited by a point reactor model in the traditional method in the actual measurement process, so that the value of the control rod can be rapidly measured, and the value measurement time of the control rod of the nuclear power plant is shortened. However, the dynamic rod-carving test method must be carried out when the reactor is in a near-critical state, and still occupies a critical path for starting the nuclear power plant, so that the benefit brought by shortening the starting time of the nuclear power plant is limited.

3. Subcritical rod-carving method

The subcritical rod-etching method is a method capable of performing control rod value measurement when the reactor is at a deeper subcritical state. The method is one of the source multiplication correction methods, and the method is a reactor subcritical degree calculation method based on fundamental wave extraction, which is originally proposed by the university of hokkaido, Japan, and defines 3 correction factors including fundamental wave correction factors by high-precision computer numerical simulation of a test process and by using reactor fundamental wave distribution, flux distribution and conjugate flux distribution obtained by simulation. In an actual test, when the reactor core is in a deep subcritical state, the measurement deviation caused by the point reactor assumption is not considered, the neutron counting rate signal of the source range detector is corrected by using a correction factor which is calculated in advance according to the neutron counting rate signal of the source range detector obtained by measurement, and then the corrected signal is used for performing reactivity calculation similar to that of the traditional source multiplication method, so that the accurate measurement of the reactor core reactivity in the subcritical state is realized, and the measurement of the control rod value can be finally realized.

FIG. 1 shows a calculation flow of the fundamental wave extraction source multiplication correction method applied to reactor subcritical degree measurement, which is proposed by the university of Hokkaido, Japan. In the method, the core state to be measured is named as the state to be measured, and the subcritical degree calculation method of the state to be measured is shown as a formula (5):

wherein:

the reactor core subcritical degree (reactivity) under a state to be measured;

the sub-critical degree (reactivity) of the core in a reference state;

extracting a correction factor for the fundamental wave;

is a neutron importance correction factor;

a spatial distribution correction factor;

the neutron counting rate of the reactor core source range detector in a reference state is taken as the neutron counting rate;

the neutron counting rate of the reactor core source range detector under the state to be measured.

In order to obtain an accurate 'measured value' of the subcritical degree of the state to be measured, corresponding correction factors are respectively extracted from a correction factor table calculated in advance according to the current reference state and the control rod position of the state to be measured, the source range counting rate is corrected, and finally the subcritical degree of the state to be measured is calculated by the method of the formula (5).

It can be seen from the formula (5) that, in order to obtain accurate reactor core subcritical degree in the state to be measured, not only the accurate correction factor and the reading of the source range detector are required, but also accurate reactor core subcritical degree in the reference state must be obtained. The method for acquiring the subcritical degree of the reactor core in the reference state proposed by the university of Hokkaido, Japan, comprises the following steps: the reference state is set near the critical point of the core, and the reactivity of the state is measured by a reactivity meter as the sub-critical degree of the core in the reference state. This method has obvious drawbacks:

(1) firstly, when a reactor starting physical test is carried out after the charging of a nuclear power plant is finished, the reactor is gradually close to a critical state from a reactor stopping state (the subcritical degree of the reactor is deep at the moment) through a rod lifting action and boron dilution, and finally the reactor core is critical. According to the method, the reactor core subcritical degree in the reference state is set to be close to the critical point, according to the test flow of the method, the reactor is required to be firstly lifted to the critical state to obtain the reactor core subcritical degree in the reference state, and then the reactor core subcritical degree is returned to the subcritical state to measure the reactor core subcritical degree in the state to be measured.

(2) Secondly, the reason why the university of hokkaido in japan selects the state near the critical point as the core reference state is that the reactivity meter has high measurement accuracy in this state and can obtain accurate core subcritical degree in the reference state, but on the other hand, in the nuclear power plant, since the reactor is in a state close to the critical state, the density of the neutron flux is extremely high and exceeds the measurement range of the source range detector, the neutron counting rate of the source range detector has a large measurement error, the accurate counting rate of the core source range detector in the reference state cannot be obtained, and finally, a large deviation will exist in the "measurement value" of the core subcritical degree in the state to be measured.

(3) In addition, the correction factors proposed by the university of hokkaido, japan include a fundamental wave extraction correction factor, a neutron importance correction factor, and a spatial distribution correction factor, which means that for each state to be measured, to realize the "measurement" of the core subcritical degree, data of three sets of correction factors must be prepared in advance, and the preparation time and the storage space of the correction factor library are objectively increased.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the conventional subcritical rod carving method is complex in test process, high in economic cost in the implementation process and poor in practicability, and the subcritical rod carving method which utilizes the source range detector signal as the signal source and solves the problems is provided by the invention.

The invention is realized by the following technical scheme:

a subcritical rod-carving method using a source range detector signal as a signal source comprises the following steps:

s1, establishing a subcritical correction factor library: the subcritical correction factor library comprises subcritical correction factors at specified rod positions of each control rod group in a state to be detected;

s2, obtaining value measurement measured values of each control rod group:

s2-1, collecting the counting rate of the source range detector in the reference state, adjusting the ground rod position of the control rod X rod group to the rod position specified in the reference state, and obtaining the counting rate of the neutrons in the source range detector in the reference stateWherein X represents the number of the bar group to be detected;

s2-2, collecting the counting rate of the source range detector in the state to be detected, lifting the rod position of the control rod X rod group to the top of the reactor core or inserting the control rod X rod group into the bottom of the reactor core, and obtaining the neutron counting rate signals of the source range detector when the X rod group to be detected in the state to be detected is lifted or inserted into the reactor core behind the reactor core, wherein the signals are respectively the neutron counting rate signals of the source range detector

S2-3, when the X-bar group is in the proposed state, calling the corresponding subcritical correction factor C in the subcritical correction factor library according to the control bar position signal_target-Out(X), calculating the reactor core subcritical degree when the X rod group to be measured in the state to be measured is lifted to the top of the reactor core according to the formula (1)

S2-4, in the inserted state for the X-bar groupThen, according to the control rod position signal, calling the corresponding subcritical correction factor C in the subcritical correction factor library_target-In(X), calculating the reactor core subcritical degree when the X rod group to be measured is inserted into the reactor core bottom in the state to be measured according to the formula (2)

S2-5, obtaining the control rod integral value of the X rod group to be measured according to the formula (3)

Wherein the content of the first and second substances,representing the neutron count rate of the source range detector in a reference state,representing the reactor core baseline state reactivity; the reactor core reference state reactivity and the subcritical correction factor of each control rod group at the specified rod position under the state to be measured are obtained through modeling calculation.

The invention adopts the signal of the source range detector as the signal source of the test; in the subcritical rod carving test performing stage, acquiring neutron counting rates of the source range detector in a reference state and each state to be tested through the source range detector, calling corresponding subcritical correction factors, and finally calculating the subcritical degree of each state to be tested by combining the subcritical degree of the reference state; the above steps are repeated, the reactivity of the reactor when each rod group is inserted into the bottom of the reactor core and lifted to the top of the reactor core can be finally obtained, the influence of the control rods on the reactivity of the reactor when the control rods are positioned at different positions of the reactor core, namely the value of the control rods is directly represented, and finally the 'measured value' of the integral value of all the control rod groups can be obtained through the test.

The method adopts a well-developed source range detector signal which is necessary for the current starting test of the nuclear power plant as a signal source, and utilizes the reference state reactivity obtained by accurate numerical calculation as a subcritical rod-carving method of reference; no hardware modification is needed; in the whole test process, the reactor is always in a state with deep subcritical degree, does not occupy any starting critical path, and is beneficial to reducing economic cost.

Further, the reference state reactivity is obtained by: calculating the finite multiplication coefficient k of the reactor core in the reference state by simulating the reference state of the reactor core_effAnd (3) calculating the reactivity of the reactor core in the reference state by adopting a formula (4):

further, the subcritical correction factor is obtained by the following method:

s1-1, aiming at a reactor to be developed with a subcritical rod carving, establishing a corresponding shielding calculation model, and utilizing neutron shielding calculation software to perform corresponding calculation on a source range detector, so as to obtain the response relation of each source range detector to a fission neutron source in the reactor and obtain the response factor of each position in the three-dimensional space of the reactor core;

s1-2, establishing a reactor physical calculation model according to a specific nuclear fuel loading scheme of the reactor;

s2-3, on the basis of the step S1-2, according to the reference state involved in the subcritical rod engraving test, considering the influence of an external source on the neutron flux distribution of the reactor core in the subcritical state, and calculating to obtain the neutron flux distribution, the fundamental wave flux distribution and the fundamental wave conjugate flux distribution of the reactor corresponding to the reference state;

s2-4, on the basis of the step S1-2, according to each state to be tested involved in the subcritical rod carving test, considering the influence of an external source on the neutron flux distribution of the reactor core in the subcritical state, and calculating to obtain the neutron flux distribution, the fundamental wave flux distribution and the fundamental wave conjugate flux distribution of the reactor corresponding to each state to be tested;

s2-5, processing the response factor, the reactor neutron flux distribution, the fundamental wave flux distribution and the fundamental wave conjugate flux distribution aiming at each state to be tested on the basis of the steps S1-1, S1-2 and S1-3, and calculating the subcritical correction factor of each control rod group at the specified rod position in the state to be tested.

Further, in the step S1-1, the response relationship of each source range detector to the fission neutron source in the reactor is a point-to-point response relationship in a three-dimensional space, which can be expressed as a three-dimensional function, and the energy clusters are divided according to the requirement of the reactor physical calculation model established in the step S1-2, and response factors of each position in the three-dimensional space of the reactor core under each energy cluster are given.

Further, in the S2-3 and S2-2, reactor neutron flux distribution, fundamental wave flux distribution and fundamental wave conjugate flux distribution corresponding to the reference state are obtained through calculation of the pressurized water reactor steady-state core calculation software; the pressurized water reactor steady state core calculation software includes MEACOR software.

The invention has the following advantages and beneficial effects:

the method is characterized in that signals of a source range detector which is necessary for the current starting test of the nuclear power plant and is mature are used as a signal source of the test, and the test process is only carried out when the reactor is in a deep subcritical state without occupying a starting critical path of the nuclear power plant. Specifically, the invention can achieve the following technical effects:

1. for some active nuclear power plants, the technical scheme of the invention means that only a source range detector which is necessary for starting the nuclear power plant is used as a signal source, no physical transformation is needed on the site, and additional test equipment purchasing is not needed, so that the hardware condition for implementing the subcritical rod-carving test can be realized. The method can save considerable technical transformation cost for the nuclear power plant, and is also beneficial to accelerating the popularization and application of a new technology of subcritical etching rods.

2. The whole subcritical rod-carving test can be carried out when the reactor is in a deeper subcritical state, so that the problem that the rod-carving test occupies a starting critical path is avoided, and considerable reactor starting test time can be saved for a power plant; on the other hand, the risk that the reactor is in emergency shutdown possibly caused by misoperation in the existing carving rod test including the dynamic carving rod can be avoided, and the method has the characteristic of inherent safety of the test.

3. The invention adopts high-precision reactor core calculation software to solve the limited core multiplication coefficient, obtains the reactivity of the reference state, and solves the defect that the reference state must be close to the critical state in the source multiplication correction method proposed by the university of Hokkaido, Japan.

4. For any state to be tested in the subcritical rod carving test, only one subcritical correction factor needs to be prepared for the state, and therefore the workload of preparing the correction factor is reduced.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:

FIG. 1 is a block diagram of the technical flow of the subcritical rod engraving method proposed by the university of Hokkaido, Japan;

FIG. 2 is a schematic diagram of the position of the out-of-reactor source range detector relative to the reactor in example 1; the neutron count rate required for the subcritical rod engraving test stage is obtained from a source range detector marked as 2;

FIG. 3 is a technical flow diagram of the present invention.

Reference numbers and corresponding part names in the drawings: 1-reactor, 2-source range detection.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.