Nuclear reactor with in-vessel out-of-core neutron detector and corresponding control method
阅读说明:本技术 具有容器内堆芯外中子检测器的核反应堆和相应控制方法 (Nuclear reactor with in-vessel out-of-core neutron detector and corresponding control method ) 是由 米歇尔·布龙 桑德里娜·斯派斯克瑞拉 于 2018-07-12 设计创作,主要内容包括:核反应堆(1)包括:-容器(3),具有中心轴线(X);-堆芯(5),设置在容器(3)中,堆芯(5)包括多个核燃料组件,一次水层(7)将堆芯(5)与容器(3)从中心轴线(X)径向隔开并围绕堆芯(5);-以及用于控制并保护核反应堆的系统(9),控制和保护系统(9)包括用于连续地测量由堆芯(5)发出的中子通量的装置(11)。测量装置(11)包括设置在将堆芯(5)与容器(3)隔开的一次水层(7)中的至少一个中子检测器(12)。(A nuclear reactor (1) comprises: -a container (3) having a central axis (X); -a core (5) arranged in the vessel (3), the core (5) comprising a plurality of nuclear fuel assemblies, a primary water layer (7) radially separating the core (5) from the vessel (3) from the central axis (X) and surrounding the core (5); -and a system (9) for controlling and protecting the nuclear reactor, the control and protection system (9) comprising means (11) for continuously measuring the neutron flux emitted by the core (5). The measuring device (11) comprises at least one neutron detector (12) arranged in a primary water layer (7) separating the core (5) from the vessel (3).)
1. A nuclear reactor (1) comprising:
-a container (3) having a central axis (X);
-a core (5) located in the vessel (3), the core (5) comprising a plurality of nuclear fuel assemblies, a primary water layer (7) radially separating the core (5) from the vessel (3) from the central axis (X) and surrounding the core (5);
-the instrumentation and control system (9) of the nuclear reactor is configured for providing instrumentation and control of the reactor in a predetermined power range, remaining power at normal standstill and rated power, the instrumentation and control system (9) comprising means (11) for continuously measuring the neutron flux emitted by the core (5);
characterized in that said measuring device (11) comprises at least one neutron detector (12) that continuously measures said neutron flux, said neutron detector (12) being located in a primary water layer (7) radially between said core (5) and said vessel (3), said neutron detector (12) being placed in one or several radial positions selected to obtain, due to the attenuation of said water layer, one or several count rates suitable for the instrumentation and control systems of said nuclear reactor (9) for the whole predetermined power range.
2. The reactor of claim 1, wherein the or each neutron detector (12) is directly immersed in the primary water without the insertion of glove fingers.
3. The reactor according to claim 1 or 2, wherein at least one of the neutron detectors (12) is a fixed detector, located at a fixed radial distance from the core (5).
4. The reactor of claim 3, wherein the radial distance is selected so as to:
-the neutron flux at the fixed detector (12) corresponds to a count between 1cp/s and 100cp/s when the nuclear reactor (1) is stopped;
-when the nuclear reactor (1) is operating at full power, the neutron flux at the fixed detector (12) corresponds to a measurement value that remains within a measurement range in the current mode of the fixed detector (12).
5. The reactor according to claim 3 or 4, wherein all the neutron detectors (12) are fixed and located at the radial distance from the core (5).
6. The reactor according to claim 3 or 4, wherein all the neutron detectors (12) are fixed, at least two of the neutron detectors (12) being located at respective radial distances from the core (5) different from each other, suitable for different power ranges of the nuclear reactor.
7. The reactor according to any of the preceding claims, wherein at least one of the neutron detectors (12) is a mobile detector, radially movable in the primary water layer (7) with respect to the core (5).
8. The reactor according to claim 7, wherein the measuring device (11) comprises a movement mechanism (29) of the movement detector (12) configured for radially moving the movement detector (12) at least between an inner position relatively closer to the core (5) and an outer position relatively further from the core (5).
9. The reactor of claim 8 wherein:
-selecting said inner position so that the neutron flux at said moving detector (12) corresponds to a count between 1cp/s and 100cp/s when said nuclear reactor (1) is stopped;
-selecting the outboard position such that the neutron flux at the moving detector (12) corresponds to a measurement value that remains within a measurement range in the current mode of the moving detector (12) when the nuclear reactor (1) is operating at full power.
10. The reactor according to any one of claims 7 to 9 in combination with claim 3 or 4, wherein the measuring means (11) comprise at least one fixed detector (12) and at least one moving detector (12).
11. A method for controlling a nuclear reactor (1) according to claim 10, comprising the steps of:
-measuring the neutron flux emitted by the core (5) with the or each movement detector (12) placed in the inner position when the nuclear reactor (1) is stopped or operating at a power lower than a first limit value;
-measuring the neutron flux emitted by the core (5) with the or each fixed detector (12) when the nuclear reactor (1) is operating at a power higher than the first limit value.
12. A control method according to claim 11, wherein the or each movement detector (12) is moved to the outboard position when the nuclear reactor (1) changes from a power below a second limit to a power above the second limit.
[ technical field ] A method for producing a semiconductor device
The present invention generally relates to systems for operating and protecting nuclear reactors, commonly referred to as Instrumentation and Control (I & C) systems.
More specifically, according to a first aspect, the invention relates to a nuclear reactor equipped with such a meter and control system.
[ background of the invention ]
The instrumentation and control systems generally comprise means for continuously measuring the neutron flux emitted by the core. The apparatus continuously takes power measurements of neutron flux at startup of the reactor and during its normal operation.
The instrumentation and control system protects the reactor, in particular on the basis of information provided by the means for measuring the neutron flux. The system must measure in real time over the entire reactor power range from source level to full power.
It is therefore very important for the latter to provide neutron measurements with short time constants ranging from tens of seconds to fractions of a second, compatible with the required performance for the protection function.
The neutron detector of the apparatus for continuously measuring neutron flux is typically located outside the reactor vessel.
The count rate of these detectors depends on:
sensitivity of the detector, limited to from about 0.1 to 40 cp/(n/cm) for applicable techniques2S) numerical value;
the extra-vessel residual flux, which then depends on the one hand on the residual activity of the core when stopped and on the other hand on the geometry of the reactor.
The count rate directly affects the response time constants of the instrument and control system.
On nuclear reactors with small cores, such as SMRs (small and modular reactors), the count rate may be too low to ensure a sufficiently fast response time with respect to events that may occur once the reactor is started.
It is first possible to perform technical development that makes it possible to improve the sensitivity of the neutron detector. This sensitivity can be increased by associating a large number of single detector cells in parallel. However, this solution faces technical limitations, in particular shadow effects between different cells. Further, it leads to a significant increase in the cost of the detector.
Another solution would be to provide neutron paths with low attenuation. This scheme is described, for example, in WO 2015/099855. This solution has the drawback of producing a discontinuity locally in the radiation protection of the container and of the apparatus.
Further, the so-called "in-core" neutron chain, whose role is to form a periodic profile of the in-core neutron flux, cannot be used to perform the neutron measurements required by the instrumentation and control systems of the nuclear reactor. So-called incore chains do not cover the entire range and/or are not measured in real time. Further, the detectors of the incore chain are not continuously positioned in the core and must be removed in order not to be used up too quickly by the core power flow.
[ summary of the invention ]
In this context, the invention aims to propose a nuclear reactor whose device for continuously measuring the neutron flux does not have the above drawbacks.
To this end, the invention relates to a nuclear reactor comprising:
-a container having a central axis;
-a core located in the vessel, the core comprising a plurality of nuclear fuel assemblies, a primary water layer radially separating the core from the vessel from a central axis and surrounding the core;
-the instrumentation and control system of the nuclear reactor, configured for providing instrumentation and control of the reactor in a predetermined power range, typically the residual power at standstill and the rated power, comprises means for continuously measuring the neutron flux emitted by the core;
characterized in that the measuring means comprise at least one neutron detector for continuously measuring said neutron flux, the neutron detector being located in a primary water layer radially between the core and the vessel, the neutron detector being placed in one or several radial positions selected to obtain, due to the attenuation of the water layer, one or several count rates suitable for instrumentation and control systems of the nuclear reactor for the whole predetermined power range.
The or each neutron detector is arranged in the water layer so that it can optimise the response of the detector for the entire measurement range. Which is close enough to the core to allow proper response time of the reactor's instrumentation and control systems in the event of a reactor anomaly once the reactor has sufficient count rate at startup.
When the reactor is operating at full power, on the one hand the water layer ensures sufficient flux decay so that the detector remains within its measurement range, and on the other hand the water layer provides sufficient protection so that the lifetime of the neutron detector is satisfactory.
These results are obtained without having to create discontinuities in the radiation protection, since the water layer located between the core and the environment, including the vessel, remains intact.
The reactor may further have one or more of the following features, considered alone or according to any technically possible combination:
the or each nuclear detector is immersed directly in primary water, without the interposition of glove fingers;
at least one of the neutron detectors is a fixed detector, located at a fixed radial distance from the core;
-selecting the radial distance so as to:
-the neutron flux at the fixed detector corresponds to a count between 1cp/s and 100cp/s when the nuclear reactor is stopped;
-when the nuclear reactor is operating at full power, the neutron flux at the fixed detector corresponds to a measurement value that remains within a measurement range in the current mode of the fixed detector;
-all neutron detectors are fixed and located at said radial distance from the core;
-all neutron detectors are fixed, at least two neutron detectors being located at respective radial distances from the core different from each other, suitable for different power ranges of the nuclear reactor;
at least one of the neutron detectors is a mobile detector, radially movable with respect to the core in the primary water layer;
the measuring device comprises a movement mechanism of the movement detector configured for moving the movement detector radially at least between an inner position relatively closer to the core and an outer position relatively further from the core;
-selecting the inner position so that the neutron flux at the moving detector corresponds to a count between 1cp/s and 100cp/s when the nuclear reactor is stopped;
-selecting the outboard position such that the neutron flux at the moving detector corresponds to a measurement value that remains within a measurement range in the current mode of the moving detector when the nuclear reactor is operating at full power;
the measuring device comprises at least one fixed detector and at least one moving detector.
Preferably, the nuclear reactor comprises at least one neutron-absorption member, and a movement device capable of inserting the or each neutron-absorption member into the core, comprising instrumentation and a control system configured to control the controller of the movement device by using the measurements carried out by the or each neutron detector.
According to a second aspect, the invention relates to a method for controlling a nuclear reactor having the above features:
-measuring the neutron flux emitted by the core with the or each mobile detector placed in an inner position when the nuclear reactor is stopped or operating at a power lower than a first limit value;
-measuring the neutron flux emitted by the core with the or each fixed detector when the nuclear reactor is operating at a power higher than the first limit value.
Further, the control method may be such that the or each moving detector is moved to the outboard position when the nuclear reactor changes from a power below the second limit to a power above the second limit.
[ description of the drawings ]
Other characteristics and advantages of the present invention will emerge from the detailed description given below, given by way of illustration and not of limitation, with reference to the accompanying drawings, comprising:
fig. 1 is a simplified schematic diagram of a nuclear reactor according to a first embodiment, considered in a sectional view in a plane perpendicular to the central axis of the vessel;
FIG. 2 is a simplified schematic diagram of the nuclear reactor of FIG. 1, considered in cross-section in a radial plane relative to the central axis of the vessel;
FIG. 3 is a schematic diagram of the neutron detector of FIG. 1;
FIG. 4 is a view similar to FIG. 1 for a nuclear reactor according to a second embodiment of the present invention;
FIG. 5 is a simplified schematic diagram of the movement mechanism of one of the movement detectors of FIG. 4; and
FIG. 6 is a view similar to FIG. 1 for a nuclear reactor according to a third embodiment of the invention.
[ detailed description ] embodiments
The
The
The
The
The
The
The
It has a thickness radially between 100mm and 800 mm.
Thus, the
The
The
The means 11 for continuously measuring the neutron flux comprise a plurality of
The
The gauge and
The
The
The measuring
According to the invention, the or each
The or each
The or each
In other words, each
The or each
The measuring
The or each
The measuring
The
The
According to the first embodiment shown in fig. 1, the or each
This embodiment is typically implemented when the meter and
The radial distance between the or each
When the
When the
In the case of a
Advantageously, the measuring
All
The number of
Each
Preferably, the measuring device comprises a
A second embodiment of the present invention will now be described with reference to fig. 4. Only the differences between the second embodiment and the first embodiment will be described in detail below.
Equivalent elements performing the same function will be denoted with the same reference numerals as those of the first embodiment.
This second embodiment is particularly suitable for situations where the instrumentation and control systems of the reactor require measurements over one hundred years. This is particularly the case with a newly core reloaded power generation reactor.
In the second embodiment, the
Typically, the measuring
The fixed detector and the moving detector are of the type described above with reference to the first embodiment and typically have all the same detection performance.
The
The or each
In this case, the measuring means 11 comprise, for the or each
The or each fixed
The or
The radial movement amplitude of each
Thus, the movement detector is located in the immediate vicinity of the core at its inboard location, for example at a radial distance of the order of 200mm from the core.
The distance is taken with respect to the nuclear fuel assembly located closest to the neutron detector.
The inside position is chosen so that the neutron flux at the moving
In principle, there is no restriction on the inboard position of the movement detector, which can be very close to the core in order to reach a minimum count, even with very low residual activity of the core when stopped.
The outboard position is selected so that the neutron flux at the moving
Typically, the normal measurement range in current mode of a detector with a CFUC07 type measurement means is 2mA at the top of the range.
The fixed detector typically enables it to cover a power range ranging from 0.1% to 100% of the rated power.
The motion detector is used when stopped and typically covers a power range up to 1% of the rated power.
Thus, the positioning of the moving detector relative to the stationary detector enables an overlap between the power range covered by the moving detector in the inner position and the power range covered by the stationary detector and the moving detector in the outer position.
When the moving detector is in the outboard position, the measurement of reactor protection is done by the stationary detector. The use of a motion detector to detect any azimuthal distortion of the neutron flux enables it to detect, for example, premature dropping of the neutron absorbing member.
The displacement mechanism 29 is designed to ensure a displacement of the
According to an advantageous variant, the movement mechanism is of the electromechanical type (fig. 5).
The moving mechanism 29 includes a support surface 31, a slide surface 33 on which the
The support surface 31 is for example a radially extending track, or any other suitable support. In this case, the sliding support 33 slides in the rail.
The drive means 35 is for example a motorized screw, as shown in fig. 5. The device comprises a stepper motor 37 with or without reduction gears, and a screw 39 rotated by the motor 37. The screw 39 cooperates with a nut forming member provided in the sliding support 33. The screw 39 extends radially. Which is selectively rotated in a clockwise direction or in a counterclockwise direction by the motor 37. The motor 37 is controlled by a control member 41 belonging to the measuring
Thus, the direction of rotation of the motor 37 of the
According to a variant not shown, the motor 37 rotates the screw 39 by means of a kinematic chain not shown, comprising an angular transmission, so that the motor 37 is located in a zone of the
A drive mechanism of the screw/nut type can be obtained directly, for example, by the control provided by a group control mechanism of the type described in french application publication No. FR 3,039,695.
The radial position of the
The position of the
According to a variant not shown, the movement mechanism of the
For example, the moving mechanism includes a radial track along which the moving detector freely slides. It also includes a baffle communicating with the primary stream toward the moving detector, arranged so that the primary stream urges the moving detector radially outward of the vessel. The passive return mechanism is for example a spring. In a variant, the passive return mechanism is gravity, the track being, for example, inclined so that the
In one exemplary embodiment, the
The two
Three fixed
Advantageously, the measuring
The control means 41 of the measuring
measuring the neutron flux emitted by the
measuring the neutron flux emitted by the
The first limit is for example equal to 1% of the nominal operating power of the reactor.
Advantageously, the or each
Conversely, when the
The second limit is equal to a few percent, for example 3%, of the rated power of the reactor.
Other logic may be used to program the control means 41 as long as they comply with the previously defined chain coverage principle.
According to another variant, the movement of the or each
A method for controlling the
The method comprises the following steps:
measuring the neutron flux emitted by the
measuring the neutron flux emitted by the
Typically, the method further comprises the steps of:
moving the or each moving
The first and second limits are those described above.
The control method preferably includes the steps of:
-returning the moving detector to the inner position when the
This step is preferably automated and is triggered autonomously by each motion detector according to its own measurements.
The control means 41 of the measuring
According to an embodiment variant applicable to the second embodiment, each movement detector is not movable between two positions, i.e. an inner position and an outer position, but is movable at a plurality of radial positions distributed between the inner and outer positions.
This makes it possible to optimize the overlap between the fixed detector and the moving detector.
A third embodiment of the present invention will now be described with reference to fig. 6. Only the differences between the third embodiment and the first embodiment will be described in detail below.
Equivalent elements performing the same function will be denoted with the same reference numerals as those of the first embodiment.
In a third embodiment, all the
Preferably, the
In the example shown in FIG. 6, two
Two
Two
This third embodiment makes it possible to gradually switch the measurement from the innermost detector towards the outermost detector while benefiting from an optimal position within the measurement range.
According to an embodiment variant, the
According to a fourth embodiment, the measuring device comprises only a mobile neutron detector. For example, the three fixed neutron detectors of the second embodiment are replaced by a moving detector. These additional movement detectors are of the same type as the movement detectors described with reference to the second embodiment.
The
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