KR20140097452A - Assembly for a nuclear reactor, comprising nuclear fuel and a system for triggering and inserting at least one neutron absorber and/or mitigator element - Google Patents

Abstract

A carrier assembly for a nuclear reactor comprising: a box (40), a fission zone disposed within a lower portion of the box (40), a free volume disposed within an upper portion of the box (40) (52) in the fission zone, a cover (54) bordering the free space (52), and a trigger and insertion system (SI) starting from the end and extending across the height of the fission zone Wherein the triggering and insertion system comprises a capsule 10 having a longitudinal axis, an absorber 2 and / or a mitigator assembly suspended within the capsule, and an assembly in which the assembly is in an accident state Wherein the capsule (10) is inserted into the lid (54), the triggering and insertion system being removably mounted within the carrier assembly, the trigger and insertion system (DI) carrier Ripche.

Description

TECHNICAL FIELD [0001] The present invention relates to an assembly for a nuclear reactor comprising a system and a fuel for triggering and inserting at least one element that absorbs and / or mitigates neutrons, including a nuclear fuel assembly and a system for triggering and inserting at least one neutron absorber and / or mitigator element}

The present invention relates to a mixing assembly for a nuclear reactor, wherein said mixing assembly is a neutron absorbing material and / or comprises at least one element to be inserted and a nuclear fuel, which may be a mitigator in the case of general core melting . The mitigating material is a material capable of forming a low melting point eutectic with the material forming the cladding of the fuel rods in the assembly and the formation of a plug that will inhibit the evacuation of the molten core or core melt formation of plugs.

The assembly is intended specifically for sodium cooled fast reactors and the sodium cooled fast reactors are hereinafter referred to as SFRs.

Elements composed of neutron absorbing materials are intended to be inserted into a nuclear reactor to control the core activity of the reactor or to limit the consequences of nuclear malfunction. During normal operation, these elements may be in the form of assembly rods suspended above the core. When the need to reduce the reactivity of the reactor is detected, the absorbent elements are inserted into the fission zone.

For example, in the case of sodium-cooled reactors, a plug that prevents the circulation of liquid sodium may form, and reactor failure may be a problem in the reactor cooling system, for example, a problem in the main coolant system. It may be a loss of heat sink, that is, the heat drawn through the reactor coolant system may no longer be discharged properly.

If there is no negative reactivity inserted, this dysfunction can lead to an increase in the reactor core temperature that can lead to melting of one or several assemblies, or even to the loss of the core melt May result.

The purpose of inserting the absorbent elements into the core is to inhibit the neutron response and stabilize the reactor core to a selected temperature to meet accepted accepted standards of functional failure.

In addition, a number of redundant, diverse, and independent shutdown systems are provided to maintain maximum safety in reactor control and to offset common mode defects.

The downtime systems used in SFC reactors (which may be qualitatively conventional) can be used in active devices, in that the insertion of the absorbing elements is triggered by external electrical control or by the loss of electrical signals Based. The downtime systems used so far have a mechanical interface with the vessel head plug.

For the next generation SFC reactors, a new downtime system is planned in case of failure of conventional downtime systems; Therefore, devices in this "emergency" downtime system should not be triggered prior to conventional downtime systems. In view of the fact that the insertion of the absorbing elements is triggered directly by the physical phenomenon rather than by the electrical control, in order to eliminate the risk of failure of the electrical machinery, control and logic systems, it is envisaged to use passive devices. For example, imagine a trigger means sensitive to variations in flow or temperature. These manual devices have been studied in detail, but there is no one yet to be used in the reactor.

FR application FR 2230984 discloses a fuel assembly comprising a fuel rod and a box including an emergency shutdown device. If there is no downtime, the downtime will be occupied by the space occupied by the fuel rods. The apparatus includes a sealed casing secured to the assembly box. The downtime includes argon and boron carbide in the form of long elements suspended along the wire. The wire is suspended from the sealed casing by a temperature sensitive fuse. When the temperature exceeds the threshold value, the fuse is melted to release boron carbide, and the boron carbide falls from the height of the core to the bottom of the capsule. The casing is fixed to the assembly so that it is not mechanically isolated from it and therefore the mechanical load applied at the lattice pitch causes arcing and / or crushing ). ≪ / RTI > The insertion of boron carbide into the core of the assembly may then be impeded.

Therefore, the reliability in inserting this assembly can be improved as disclosed.

In addition, checking that the emergency shutdown device is operating properly is not possible for two reasons; First, this type of system can only operate once, and it is impossible to rearm the fuse system. Secondly, since the emergency stop device is fixed to the assembly, It is impossible to assume that it will be implemented.

Moreover, since the casing is fixed to the transport fuel assembly, it is impossible to separate the lifetime of the absorption apparatus from the lifetime of the transport fuel assembly. Moreover, it is difficult to handle absorbent materials in fuel assembly production lines and during dismantling operations.

French application FR 2251079 discloses a safety device for a nuclear reactor with absorption elements in the form of cylindrical links. However, the cylindrical shape of the links is not optimal for insertion reliability, for temperature aspects, or for neutron efficiency.

French application FR 2683667 discloses a fuel system with an integrated manual safety device. The manual safety device includes absorption elements in the form of balls cast into a meltable matrix. First, the stack of balls can cause mechanical blockage due to the arching effect, which can reduce tripping and insertion reliability. Secondly, the distribution of the balls in the fissile bundle is not controlled, and the irradiation of the bundles can be significantly deformed due to irradiation creep and swelling under irradiation, ) At the end of. There is also the risk of partial or total closure of the fuel rod bundles by the balls and the risk of closure of the gratings located upstream and downstream from the bundle, which is a major concern for additional safeguards designed to cover very unlikely accidents The design rule, that is, the prevention level provided by the standard design, should not be degraded. However, despite the fact that instantaneous total blockage (BTI) of the fuel assembly is one of the scenarios considered in the SFR as a fuel meltdown initiator, the residual risk Area.

US Patent 5,051,229 discloses a temperature sensitive triggering device which makes it possible to insert a neutron absorber into a reactor; The device is disposed within the fuel assembly. The responsiveness and accuracy of this system for temperature excursions is very limited. In addition, the device has a serious effect on the neutron performance of the core during normal operation. In order to minimize the effect of the downtime system on the neutron performance of the core during nominal operation, the volume ratio of neutron functional components (absorber and fuel) per assembly is maximized to minimize the loss of the fuel volume ratio within the core . For assemblies dedicated to the control system, this typically means minimizing the volume of the absorber per assembly to minimize the number of positions in the core. For mixed assembly designs where attempts have been made to minimize the triggering response, this should result in minimizing the reduction in fuel volume ratio compared to power assemblies. U.S. Patent No. 5,051,229 makes none possible because it provides a significantly lower maximum fuel volume ratio (one absorber capsule and a combination of five fuel capsules) than is possible with standard fuel assemblies, Because it provides a significantly lower maximum absorbent volume ratio (a combination of one fuel capsule and five absorbent capsules).

As a result, it is an object of the present invention to provide an apparatus and a method which are free from manual contact, i.e., mechanical contact with the container head plug, have high accuracy and good triggering reliability and excellent insertion reliability, The system comprising an emergency downtime system in which operation can be tested.

The above-mentioned object is achieved by a nuclear assembly comprising a box in which fuel rods are disposed inside the box and a emergency shutdown system disposed in the box and occupying some of the space of the fuel rods as a box, The emergency downtime system includes a capsule extending along a center-line of the box, the capsule being removably insertable within a lid that bounds the housing within the fuel rods, wherein the neutron The assembly to be inserted, which may be an absorbent material and / or a mitigating agent, is suspended.

The assembly includes an emergency downtime system that is mechanically decoupled from the assembly and the system can then be placed in position and checked to see if it is working properly, , Or removed from the assembly box to replace the assembly to be inserted if the degree of negative reactivity is excessively reduced.

The accuracy of the insertion and the triggering reliability are optimized because almost all of the circulating coolant flow in the box passes through the device and is practically identical to the flow in the standard fuel assembly. The insertion is triggered more quickly and more accurately than with an assembly exclusively dedicated to the absorbent material because the power and coolant feed flow of the exclusive fuel or mixing assemblies is significantly greater than the power and coolant feed flow of the exclusive absorbent assemblies Because it is higher.

The release of the assembly to be inserted may be triggered by any physical characteristic that represents an accident condition of the assembly.

The flow or neutron flux can be used as a triggering physical phenomenon depending on the type of accident condition to be encountered, namely reactor coolant flow and reactivity transient.

Preferably, the temperature can be used as a triggering physical phenomenon. The downtime system trigger device may be of a magnetic type, and the assembly to be inserted is released when the Curie temperature is reached. Preferably, it can be triggered by a differential expansion phenomenon, wherein an increase in the coolant temperature causes the release of the assembly to be inserted, and the release device is directly in the coolant flow.

Advantageously, the emergency shutdown device also includes means for preventing the unwanted drop of the assembly to be inserted by preventing the assembly to be inserted from being released, if the coolant temperature does not exceed a given threshold.

Most advantageously, the assembly to be inserted is formed of several spherical elements that are mounted on a cable forming a string, reducing the risk that the elements will not be inserted.

If so, the subject matter of the present invention is a carrier assembly for a nuclear reactor, comprising: a box having a longitudinal axis that is approximately oriented along a vertical axis; a fission zone disposed within a lower end portion of the box; a free space in the fission zone, starting from an end of the fission zone disposed on the side of the upper portion along the longitudinal axis and extending over at least a portion of the fission zone along the longitudinal axis, ) Cover, and a triggering and insertion system, wherein the triggering and insertion system comprises a capsule having a longitudinal axis, an assembly to be inserted suspended within the capsule, and an assembly to be inserted if the assembly is in an accident state Wherein the capsule is partially inserted into the lid, the capsule is inserted into the lid, A foot and insertion system is removably mounted within the carrier assembly, the capsule including a gripping head from which the triggering and insertion system is suspended over the cover.

The triggering and insertion device is advantageously arranged in the upper part of the upper section of the box.

Preferably, the free space is disposed in a central portion of the fission zone such that the longitudinal axis of the triggering and insertion system is coaxial with the longitudinal axis of the assembly.

The assembly to be inserted may be a neutron absorber and / or a relaxant type.

The longitudinal dimension of the assembly to be inserted may be selected to be, for example, equal to one-half of the total length dimension of the capsule.

Preferably the capsule includes means for damping the drop of the assembly to be inserted at the end of movement of the assembly to be inserted.

According to another feature, the capsule includes coolant supply orifices at the end of the portion of the capsule disposed within the lid.

The carrier assembly may include guiding means for positioning the triggering and insertion system within the fissure zone of the assembly, wherein the guiding means comprises an end portion of the lid disposed on the same side as the free volume of the carrier assembly .

The box preferably has a hexagonal cross-section, which preferably has a hexagonal outer cross-section and a hexagonal or circular inner cross-section, the capsule preferably having a circular outer cross-section.

Advantageously, the assembly to be inserted comprises a plurality of elements hingedly mounted to one another, and one end element forms an attachment head cooperating with the means for holding the triggering and insertion device. The elements are advantageously slid onto the cable. For example, the cable may be made of braided metal fibers or braided ceramic fibers.

Particularly advantageously, each element is spherical in shape.

The carrier assembly may include damping means between at least a pair of elements.

For example, the elements are formed of a plurality of absorbent materials. The absorbent elements may include at least some elements in the first absorbent element, and second elements in the second absorbent element.

According to one advantageous characteristic, the elements are hollow or comprise a peripheral core consisting of a central core and two different materials.

The triggering and insertion system is advantageously sensitive to temperature variations. More advantageously, the triggering and insertion system is of a different expansion type.

For example, the triggering and insertion system includes locking means to prevent insertion of the assembly to be inserted at a temperature below the reactor operating temperature.

The carrier assembly preferably includes means for detecting insertion of the assembly to be inserted by ultrasound telemetry. For example, the triggering and inserting device includes a longitudinally moving portion and a longitudinally secured portion formed from the capsule, the capsule including means for holding the inserted assembly in a suspended position above the fission zone, The assembly to be inserted can be released under the action of the moving part, the moving part comprising locking means formed by at least one first surface, called the stop surface, means for holding the assembly to be inserted in the suspended position, Means for releasing said assembly to be inserted from said retaining means, said releasing means being formed by at least one second surface, called the release surface, and means for displacing said stop surface and said release surface along said longitudinal axis, The displacement means is configured to move the capillary against the capsule under the effect of the temperature rise of the coolant Wherein the stop surface and the release surface move axially away from the retaining means when the coolant temperature is raised, wherein the stop surface and the release surface are formed by a shell capable of differentially expanding in longitudinal direction The stop surface moves away from the holding means such that the releasing surface moves axially towards the holding means and the holding means is unlocked when the coolant is at the normal reactor operating temperature, , The releasing surface is arranged to apply a thrust force on the holding means so that the assembly to be inserted is released.

The detecting means may comprise at least one ultrasonic transducer disposed on the head of the capsule, and a reflector mounted on the head of the capsule facing the transducer, wherein the longitudinal position of the reflector Is controlled by whether the assembly to be inserted is held in place by the retaining means and the reflector is connected to the assembly to be inserted by an elongated element, Is configured to slide freely in a longitudinal reaming through the capsule head and to hold the reflector by a bearing on the assembly to be inserted in a non-inserted state.

The carrier assembly may include elastic means wherein the resilient means is compressed in the presence of the assembly to be inserted and tensioned to cause the elongate element to expand to move the reflector if the element to be inserted is not present do.

Preferably, a radial clearance is provided between the shell and the capsule for delimiting the coolant circulation channel between the shell and the capsule, the shell having orifices for circulation of the coolant in the channel ).

For example, the retaining means may comprise at least two and preferably three fins distributed about the longitudinal axis, the fins being arranged on the longitudinal axis to hold the assembly to be inserted between the fins And is rotationally hingedly mounted on the capsule for movement to a position close to and away from the longitudinal axis from which the assembly to be inserted is released.

The stop surface may, for example, prevent the pins from moving away from the longitudinal axis as a radially arranged surface outside of the pins, the release surface may be a surface perpendicular to the longitudinal axis, And a cam surface cooperating with the releasing surface to pivot the pins in a direction away from the longitudinal axis.

For example, if the shell is made of an austenitic steel and the capsule is made of a tungsten-based alloy, or the shell is made of work-hardened Z10 CNDT 15.15 B steel, Is made of W-5Re.

The carrier assembly is advantageously used for liquid metal cooling, especially sodium-cooled, high-speed reactors, wherein the material (s) of the neutron absorber is B ₄ C, a hafnium metal having a variable richness of ¹⁰ B, Materials of the refractory boron type, such as HfB ₂ and TiB ₂ , are selected from europium hexafluoride. The material (s) used as the neutron absorber for the water cooled thermal neutron nuclear reactor are hafnium, Dy ¹¹ B ₆ , Gd ¹¹ B ₆ , Sm ¹¹ B ₆ and Er ¹¹ B ₄ , natural HfB ₂ and natural TiB ₂ < / RTI >

Another object of the present invention is a nuclear reactor comprising carrier assemblies and nuclear fuel assemblies according to the present invention.

The invention will be better understood after reading the following description and the accompanying drawings.
1 is an overall view of an exemplary embodiment of a carrier assembly according to the present invention, wherein the carrier assembly comprises a triggering and insertion system, a set of pendant absorbing elements;
2 is a view of the assembly of FIG. 1, wherein the set of absorbing elements is inserted;
3 is a cross-sectional view of the assembly of FIG. 2, taken in a fracture zone taken through the absorbent element,
Figure 4 is a front view of a particularly advantageous embodiment at the handling temperature of the trigger and insertion system that may be used in a carrier assembly according to the present invention;
5A is a longitudinal cross-sectional view at the handling temperature of the triggering and insertion device of FIG. 4,
Figure 5b is a longitudinal cross-sectional view at the operating temperature of the triggering and inserting device of Figure 4;
Figure 5c is a longitudinal cross-sectional view at the triggering temperature of the triggering and inserting device of Figure 4 immediately before the insertion of the absorbing material into the core,
Figure 5d is a longitudinal cross-sectional view at the triggering temperature of the triggering and insertion device of Figure 4 during insertion of the shock absorber into the core;
- Figure 6 is a plan view of the system of Figure 4,
7 is a cross-sectional view of the system of FIG. 4 taken along the plane AA shown in FIG. 5C. FIG.
In the following description, the terms "upper" and "lower" are used to refer to parts of the elements disposed at the upper and lower ends of the figures, corresponding to the arrangement of elements in the reactor. The terms "upstream" and "downstream" refer to the direction of circulation of the coolant within the assembly, i.

Throughout this description, the term "carrier assembly" refers to an assembly according to the present invention including both nuclear fuel and absorbing elements, while a "standard assembly" refers to an assembly comprising only nuclear fuel.

In addition, "normal operation" indicates the operation of the reactor under normal conditions and "accident condition" indicates the state of the reactor where insertion of the absorbers is required to slow down or even stop the reaction. For example, this condition results in an increase in the reactor temperature that causes a rise in coolant temperature above a given temperature threshold.

Furthermore, although the assembly to be inserted in the following description is described as being a set of elements made of a neutron absorbing material, the present invention can also be applied to the insertion of a set of absorbing and / or mitigating elements.

Generally, a nuclear reactor includes a containment in which a plurality of fuel assemblies disposed adjacent to each other are located inside. The assemblies form a reactor core. The coolant circulates within the assemblies between the assemblies to extract heat generated by the fuel forming the primary system. The assemblies include, for example, the fuel that is distributed within the fuel rods. The portion of the assemblies, including the fuel, is called the fission zone.

The carrier assembly A according to the invention, shown in Figures 1 and 2, comprises a cylindrical box 40 in the form of a hexagonal cross section, the box 40 having a longitudinal axis X1. Generally, for SFRs, the assemblies have a hexagonal outer cross-section. For other types of reactors, the assemblies have other types of external cross-sections, such as, for example, a circular cross-section or a rectangular cross-section.

The carrier assembly according to the present invention replaces the standard nuclear fuel assembly. The reactor may comprise various carrier assemblies according to the present invention.

The box 40 includes a central portion 42 called the fission zone within which fuel rods 41 fit. The box 40 includes a lower portion called an assembly stand 44 for holding the assembly within the reactor and the assembly stand 44 is supported within a support called an end truck . The box 40 also includes an open upper portion 48.

The assembly stand also includes coolant supply orifices 46 through which coolant may be supplied to allow coolant to pass through the assembly.

The carrier assembly A carries the coolant circulated by the pumps from the bottom to the top, as shown by arrow F, and the coolant draws heat generated by the fuel rods. The coolant is also circulated in the so-called inter-assembly zones between the standard assemblies and the carrier assemblies outside the carrier assembly.

The carrier assembly also includes a housing 52 having a longitudinal axis extending across the entire height of the fuel rods 41. The housing 52 is bounded by a lid 54, and the outer cross section of the housing is similar to the cross section of the box. The lid 54 keeps the trigger and insertion system SI, which will be described later, in the bundle of fuel rods and makes the design of the bundle of fuel rods consistent. Thus, in the case of an SFR, the cover 54 has a hexagonal outer cross-section like the box. In the example shown in Fig. 4, the inner cross-section of the cover 54 is circular. Alternatively, the inner cross-section of the lid 54 may be hexagonal.

In the example shown and advantageous, as will be seen later, the axis of the housing 52 is in line with the axis of the assembly. For example, the cover 54 replaces fuel rods of two rings.

The lower end of the lid 54 includes one or more coolant supply orifices.

The carrier assembly according to the present invention also includes a neutron absorber triggering and insertion system (SI), which forms an emergency shutdown device in case of an accident operation. The triggering and insertion system comprises a triggering and insertion device (DI) and an absorber assembly (2), the set of shock absorbers being held suspended by the triggering and inserting device (DI) during normal operation, do.

The triggering and insertion system (SI) is removably mounted by the cover (54). No fixing means is provided between the triggering and insertion system (SI) and the assembly.

As can be seen in FIG. 4, the triggering and insertion system SI comprises a capsule 10 formed from a tubular body having a circular cross-section and having a longitudinal axis X in the example shown. In the given example, the internal cross-section of the cover 54 is circular and the internal cross-section of the capsule 10 is circular, as noted above.

The capsule 10 comprises an upper zone ZI and, as can be seen in figure 1, when the system is installed in an assembly, the absorber 2 in the upper zone is arranged near the fuel rods And is suspended from the triggering and inserting device DI. The capsule 10 also includes a lower zone ZII which is located in the lid 54, and thus in the fission zones, in the fuel rods. The lower section ZII houses the assembly 2 when the assembly is released (Fig. 2). The diameter of the lower section ZII of the capsule 10 is slightly smaller than the inner diameter of the lid 54 so that it can be inserted.

Apart from the fact that the lid 54 bounds the housing for the capsule 10, it also improves the mechanical isolation between the triggering and insertion system SI and the assembly, And the insertion system (SI) prevent rod swelling under irradiation. Thus it generally contributes to the mechanical isolation of the lattice pitch.

The capsule 10 also includes a gripping head 13 which will be used to handle the capsule 10 and more generally the triggering and insertion system SI. In Fig. 4, the gripping head 13 includes means for gripping the system with an external handling device (not shown). The head of the capsule 10 is held in the carrier assembly. A coolant, such as liquid sodium, is circulated in the assembly from the bottom to the top along the longitudinal axis (X).

The lower portion of the capsule 10 is provided with the supply orifices used to fill the capsule 10 with coolant and the lower supply orifices are provided with porous vents having a very high pressure loss. Thus, this allows filling without any significant flow, regardless of the dimensions of the upper output orifices. Preferably, the assembly 2 has a small mass, sodium has a significant viscosity, and consequently the coolant flow in the capsule does not slow down the fall of the neutron absorbing material to increase the drop time, It is as low as possible.

In the illustrated and advantageous example, an annular portion 61 is provided at the top of the lid 54 to centrally center the triggering and insertion system during installation of the triggering and insertion system; This part also performs a secondary thermohydrodynamic function to mix the flow outlet from the lid with the flow outflow from the bundle of fuel rods, thereby resulting in a uniform temperature of the coolant surrounding the expansion shell Lt; RTI ID = 0.0 > a < / RTI > The head of the capsule 10 is suspended, and the capsule is not supported at its lower end or in the shell. Fig. 3 is a cross-sectional view of the assembly of Fig. 1, taken in the fissure zone taken through the absorber assembly 2. Fig. The relative layout of the fuel rods 41, the cover 54, the capsule 10 and the absorbent element 4 of the absorbent assembly 2 can be understood.

The triggering and insertion device DI is used to insert the neutron absorber in the event of an accident. Depending on the type of situation, this accident behavior can be detected, for example, by variations in the coolant flow or variations in the neutron flux. Advantageously, it can be detected by an increase in the coolant temperature above a given threshold in the assembly, so that the heat generated by the main accident conditions, the loss of reactor coolant flow, the secondary system and the reactivity transient A loss of the sync can be detected. While these three accident conditions can lead to an increase in the coolant temperature, for example, the use of flow fluctuations can only detect a single accident situation.

Detailed description of Figures 2 and 4, Figures 5a-5d and 6 show particularly advantageous exemplary embodiments of a trigger and insertion device with differential swelling for a carrier assembly according to the present invention.

The triggering and inserting device DI is designed to hold the absorber assembly 2 above the fissure zone during normal operation and will release the absorber assembly 2 in an accident condition.

In the illustrated and highly advantageous embodiment, the absorber assembly 2 comprises a plurality of spherical or substantially spherically shaped elements 4, which are arranged on a cable 6 (shown in phantom) It is made of slidable neutron absorbing material to form a string. The set of these absorbing elements is described in detail in the remainder of the description.

The top element 2.1 is distinguished from other elements in that it is designed to cooperate with the triggering and inserting device. The end element 2.1 forming the attachment head is tapered in shape and formed from spherically shaped elements and a large base oriented towards the side.

The form of the element (4) is by no means limiting, and the use of long elements such as cylinders of revolution may be suitable. However, this form is less optimal than the spherical form for the insertion reliability of the elements.

The hinged structure in the form of a string is by no means limiting, and a structure formed from one or more rods made of absorbing material, such as control rods, is suitable. However, with regard to the reliability of the insertion of the absorber assembly, it is not as excellent as having this structure with a string of hinge elements.

The coolant, for example liquid sodium, circulates in the assembly from the bottom to the top along the longitudinal axis X.

The triggering and insertion device DI is arranged around the upper end zone ZI of the capsule. The device DI includes means 11 for holding the assembly 2, means for locking the holding means 11, and manual activation means for releasing the assembly 2 in an abnormal situation.

The triggering and inserting device DI has a rotatable form with a longitudinal axis X.

The triggering and inserting device DI comprises a shell 19 fixed on the capsule 10 via its upstream end in the lower part of the device taking into account the direction of coolant circulation from the lower end to the upper end, And a control head 18 extending in the upper portion of the device and axially fixed to the shell.

The control head 18 is installed to freely slide around the capsule 10. A radial clearance is provided between the outer diameter of the capsule and the inner diameter of the control head (18).

The holding means 11 also includes pins 20 hingedly mounted on the upper portion of the body of the capsule 10.

The control head 18 and the fins 20 are advantageously disposed within the upper portion of the capsule 10 within a zone remote from the fission core, with minimal neutron flux.

Preferably, there are three fins 20 disposed about 120 degrees from each other to provide uniform support for the assembly. However, it is possible to provide only two pins or three or more pins. In the holding position, the pins 20 are inclined toward the longitudinal axis X.

Each pin 20 has a first longitudinal end 20.1 hinged in rotation on the body of the capsule 10 about a Y axis orthogonal to the longitudinal axis X, And a second longitudinal end 20.2 forming a support surface in contact with the head 2.1. The capsules 10 include longitudinal slots and the fins 20 are installed inside the slots so that the second end 20.2 of the fins 20 is located inside the capsule 10.

Advantageously, said second end 20.2 of each pin includes a notch 22 bounded by two surfaces 22.1, 22.2, particularly shown in Figure 5c. The work surface 22.1 will contact and bear with the large base of the attachment head 2.1 and the other surface 22.2 will contact and support the side, As can be understood.

The control head 18 supports means for locking the fins 20 at a holding position in the assembly 2, i.e. at a position inclined towards the longitudinal axis X. [

The locking means includes stops (24) arranged radially outwardly of the pins (20) to prevent the pins from moving away from their holding position. In the illustrated example, each of the pins includes a nose on their edge 20.3 facing their stop surface 24. The radial clearance is advantageously provided between the nose and the stop surface 24 to avoid the risk of friction and seizing.

In the illustrated example, the stop surfaces 24 are supported by a single annular surface having an axis X, which is formed inside the control head 18. In the illustrated example, the surface is downstream from the pin rotation axes of the capsule 10. [

In addition, the control head 18 supports a manual means for activating the release of the assembly 2 in an abnormal situation. The manual activation means is formed, for example, by thrust surfaces 26 oriented along a transverse plane perpendicular to the longitudinal axis, the manual activation means being in contact with the pins 20 and bearing thereon Apply thrust so that they will pivot about their axis of rotation.

The thrust surfaces 26 will come into contact with the cam surfaces 28 of the fins 20, which are disposed radially inward from the rotational axis of the fins 20.

In the illustrated example, the thrust surfaces 26 are disposed upstream from the rotational axes of the fins 20 on the capsule 10.

In the illustrated example, the control head 18 includes cavities 30 in the periphery of the internal periphery, and the fins 20 fit within the cavities.

The outer surface of the tubular body of the capsule 10 includes three radially projecting tabs 32 that support the rotational hinges of the fins 20.

The manual activation means is formed by the shell (19) and the control head (18). The shell 19 and the control head 18 are made from a material having a coefficient of expansion that is higher and preferably much higher than the coefficient of expansion of the material making up the capsule 10.

4 to 5D, the inner diameter of the shell 18 is such that it forms a channel between the shell and the outside face of the capsule 10 to enable the flow of coolant, Is selected. Openings (36) are made in the upstream and downstream portions for the supply and removal of the coolant in the shell (19).

For example, the radial distance between the shell and the capsule is in the order of one to several centimeters, meaning that a significant portion of the coolant flow is present between the outer surface of the shell 19 and the outer surface of the capsule 10 between the inner surface and the inner surface. If so, the temperature of the system is close to the temperature of the coolant, so the system triggers with high accuracy.

Advantageously, the axial dimension of the shell 19 is chosen to be very large, and therefore has a very large heat exchange area with the coolant, so that local temperature non-uniformities that can occur can be handled, Can be improved.

Means are provided for attenuating the fall of the neutron absorbing material at the end of the movement in the lower zone (ZII) of the capsule. For example, this attenuation is obtained by reducing the diametric gap between the absorber assembly and the capsule at the bottom of the capsule.

We will now describe the operation of the triggering and insertion device DI according to an exemplary but non-limiting exemplary embodiment.

In operation of the triggering and inserting device according to the invention, a distinction is made between the four main states as a function of the temperature applied thereto:

- Installation state (of the system SI in the carrier assembly): ambient temperature, for example 20 ° C, referred to as "installation temperature";

- a handling state (of the carrier assembly in which the system (SI) fits in the reactor core): a temperature of 180 ° C to 250 ° C, referred to as the "handling temperature";

Operating state: operating temperature of the order of 550 ° C when the assembly is in the operating core;

- Triggered state: a threshold temperature, for example, of the order of 660 ° C, in which the absorbent material is required to be inserted into the fission core.

The installation state is not shown, but is very similar to the state shown in Fig. 5A. In the installed state, the various elements of the triggering and insertion system are not deformed by thermal expansion. The fins (20) support the assembly (2). The stop surfaces 24 face the noses 20.3 of the fins 20 and the thrust surfaces 26 are spaced from the cam surfaces 28. So that the pins 20 are locked and the assembly 2 can not be released. The system can be completely and safely handled without any risk of unwanted insertion into the fuel rod bundle.

In the handling state, the triggering and insertion system is inserted into a position within the carrier assembly, wherein the carrier assembly is located within the reactor. Due to the difference in the coefficient of expansion of the material of the capsule 10 and of the material of the shell 19 and of the control head 18 and of the temperature in the reactor it is possible that the shell 19 and the control head 18 A differential expansion occurs between the constructed assembly and the capsule 10. There is therefore a differential deformation between the capsule 10 and the assembly consisting of the shell 19 and the control head 18 and the stop surfaces 24 supported by the control head 18 And relative displacements of the thrust surfaces 26 relative to the fins 20.

Thus, in the handling state shown in FIG. 5A, the elements of the triggering and insertion system have begun to expand a little. This deformation mainly occurs along the vertical axis.

However, due to the differential expansion between the installed state and the handling state, even though the stop faces 24 have moved relative to the fins 20, the stop faces are still in partial contact with the noses of the fins 20 And still locks the pins in the holding position of the assembly 2. [ The pins (20) thus support the assembly (2). The assembly can not be released. The system can therefore be handled completely safely without any risk of unwanted insertion into the fuel rod bundle.

This operating state is shown in Fig. 5B. The different elements of the triggering and insertion system are immersed in the coolant at operating temperatures. The shell 19 is surrounded by a coolant through a channel formed between the shell 19 and the capsule 10 and is therefore sensitive to the operating state of the assembly.

An increase in the temperature of the coolant between the handling state and the operating state means that the thermal expansion causes a continual increase in the deformation of the elements of the triggering and insertion system. Due to the differential expansion between the shell 19 and the capsule 10 at the operating temperature, the stop faces 24 no longer face the noses of the fins 20, 20 are released. The thrust surfaces 26 are in direct contact with the cam surfaces 28 so that the pins 20 are inclined from the holding position of the assembly 2 toward the longitudinal axis.

As the coolant temperature rises, the expansion of the elements continues between the operating temperature and the trigger temperature. The thrust surfaces 26 exert a longitudinal upward thrust on the cam surfaces 28 of the fins 20 which causes the fins 20 to tip outwardly. A rotation about their Y axis of the fins 20 causes an upward axial displacement of the assembly 2. Due to this actuating movement of the triggering and insertion device, for example between the attachment part of the assembly 2 and the body of the capsule 10, any connections formed between the moving parts and the fixed parts Also fail simultaneously due to agglomeration and oxidation of impurities.

The triggered state, i.e., the state in which the assembly 2 is released (immediately before release) when the temperature threshold is reached is shown in Figure 5c and (during insertion) is shown in Figure 5d. In Fig. 5c, the fins 20 are in the final rotation phase, and the assembly 2 is virtually released. In Fig. 5D, the pins have finished tipping, and the assembly 2 is released and drops toward the fission core.

The insertion of the absorption elements stifle the neutron chain reaction in the short term to prevent core melting.

The stifling temperature, which is compatible with maintaining the integrity of the core support structures, is guaranteed for a sufficiently long period of time to take corrective actions.

As mentioned above, the shell 19 and the control head 18 of the triggering and inserting device are made from a material having a high coefficient of expansion and are made of, for example, steel, more specifically, for example, a work hardened Z10 CNDT 15.15 B (15/15 Ti) Steel is made from austenitic steels, just as it is used for fuel rod cladding. A W-5Re alloy, which is a tungsten-based alloy, for example a tungsten alloy with 5% rhenium, is made from a material having a coefficient of expansion that is significantly lower than the coefficient of expansion of the material used for the shell 19 and the control head 18 Can be selected for the capsule 10. Alloys such as W-ODS can also be assumed. Apart from its low coefficient of expansion, tungsten has the advantage of very little swelling under irradiation at temperatures considered due to its heat-resistant nature. Advantageously, the W-5Re alloy also has acceptable ductility under the design rules considered. Alternatively, the Z10 CNDT15.15 B alloy can be selected for the capsule and the W-5Re alloy can be selected for the shell, thereby clearly defining that the trigger is accordingly adapted .

In the illustrated example, the stop surfaces 24 form a radial surface, and the thrust surface 26 forms a surface perpendicular to the longitudinal axis. However, this configuration is by no means exhaustive.

Means are provided advantageously for detecting the condition of the triggering and inserting device to test whether an unwanted insertion of the assembly 2 has occurred. The first technique is indirectly controlled by " core temperature treatment "(TRTC), which is made by neutron detectors, or by using thermocouples disposed at the top of the assemblies to measure the coolant outlet temperature, And detecting the insertion of the figure. If the absorbent material falls, the power of the carrier assembly falls and the outlet temperature of the coolant from the support assembly drops. As a result, insertion of the side reaction is detected when a drop in the coolant temperature is detected.

Another technique consists in detecting the (suspended or not) state of a set of absorbing elements.

The detection device DT to which this technique is applied is shown in Figs. 5A to 5D. An ultrasonic telemetry device is designed to measure the distance between the reflector and one or more transducers (67) disposed on the assembly heads, and its position relative to the transducer (s) Lt; / RTI > is inserted or not.

The device DT comprises a gauge 64 which is freely slidable in a longitudinal reaming 65 formed in the gripping head 13 of the capsule 10. The length of the gauge 64 is such that its lower end is in contact with and is in contact with the attachment head of the set of absorbing elements 2 and an upper end protrudes from the upper end of the gripping head .

The upper end of the gauge 64 includes a reflector 66. Since the lower end of the gauge is in contact with and only in contact with the attachment head of the absorber assembly, the gauge will not prevent insertion of the string if the string is not blocked because the gauge and string are not secured together to be. Since the small section of the gauge is insufficient to form the reflector, the shape of the upper end of the gauge is such that its cross section is larger than the cross section of the rod in the reaming. For example, it is in the form of a cone with a taper facing upwards, and the base of the cone forms the reflector 66. When the gauge drops, the cone comes into contact with the upper portion of the reaming and stops. However, it is also possible to drop a few centimeters, which is sufficient for ultrasonic detection. For example, a distance of 13 mm may be selected.

The reflector 66 supported by the gage and passing through the gripping head 13 is positioned as close as possible to the assembly head (schematically shown in FIGS. 5a to 5d), which is an ultrasound solid reflection angle, and limits the echo on the structures surrounding the gripping head.

Transducers 67 (shown schematically) are disposed above the assembly head. The axial displacement of the reflectors during insertion of the assembly 2 enables detection and positioning of the assembly. For example, transducers are fixed on core cover plug gratings.

Advantageously, a spring 68 is provided installed in a compressed state between the bottom end of the gauge and the lower end of the reaming. The spring is compressed during normal operation, i.e. when the absorber assembly 2 is in the non-inserted position, and the attachment head is held in place by the pins 20. The spring 68 expands and causes a downward displacement of the gauge 64 as the absorber assembly 2 drops with the attachment head therewith. This spring 66 advantageously does not prevent the gauge 64 from falling. Since the mass of the gauge 64 is small, the adherence due to the corrosion phenomenon or the presence of, for example, impurities can prevent it from falling. Such closure is achieved by the force exerted by the spring 68 as the spring 68 expands and the gage 64 falls and the device DT detects that the string 2 has fallen do. The force exerted by the spring is not relieved by the irradiation creep, which is due to the fact that the spring is at a distance from the fission core. Thus, the spring 68 improves the detection reliability of the telemetry device.

As a variant, the transducers are not in a straight line perpendicular to the reflector. The fixed reflectors are positioned on the inner surface of the assembly head for directing an ultrasound beam toward the reflector 66. The reflector 66, which is otherwise supported by the gauge 64, has several facets that form a three-plane mirror, for example to improve guidance of the bundle You can have one surface. This variant advantageously makes it possible to use one transducer for several assemblies.

We will now briefly describe the operation of this detection device DT.

In the case of Figures 5a to 5c, when the assembly 2 is suspended, the gauge 64 is held in contact with the attachment head of the absorber assembly 2 and the spring 68 is compressed, 66 are spaced apart from the transducer (s), which corresponds to a state in which the absorber assembly is not inserted.

5D), the gauge 64 is no longer supported on the attachment head, and the expansion and gravity of the spring 68 The gauge 64 is slid downward in the reaming to move the reflector 66 together with it to a second position supporting it on the gripping head 13. The transducer 67 measures the increase in the distance between the transducer 67 and the reflector 66 and thus detects the insertion of the assembly 2.

This detector is particularly reliable. As the gauge 64 has a small cross section, consequently it is flexible in bending and a large mechanical clearance is formed in the reaming; All the risks of mechanical closure can be avoided and even if the gripping head 13 is significantly deformed due to shaft distortion and / or fracturing of the reaming.

This detection device ensures the detection (and positioning within the core) of the dropped absorption elements under all conditions without any reduction in the triggering and insertion reliability of the string.

This detection device may be used additionally or alternatively to TRTC and / or fissile chambers to diversify the means for detecting inserted side reactivity.

According to the present invention, the triggering and insertion system (SI) is added into the assembly and is thus completely independent of the carrier assembly, and thus can be managed independently of the fuel assembly.

It is therefore possible to carry out operational tests, e.g. ex-situ triggering and drop tests of the assembly 2, i.e. only for the capsule 10 outside the reactor. These operational tests may be performed systematically before initial integration into the assembly A.

The triggering and inserting device can be checked or replaced if necessary or the triggering and inserting device can be refitted independently of other fuel assembly elements if the system is in a functional failure. This replacement or re-assembly can be done without rejecting the entire assembly. This possibility has the advantage of managing the life of the insertion systems independent of the lifetime of the fuel assemblies, which reduces the fabrication costs or reduces the amount of activated waste in the post cycle It may be useful if it is required to minimize.

The triggering and insertion device DI according to the invention is particularly suitable for removable triggering and insertion systems. All the risk of unlocking the pins at the time of handling is avoided by means of the triggering and insertion device, more particularly the stop 24, which guarantees locking up to the handling temperature, and, for example, The set of absorbing elements can not fall during the installation of the capsule in the carrier assembly in the event of an impact that the attachment head or cable will break. This is also advantageous during integration of the assembly (described above in the handling state) into the core.

The integration of the fuel assembly structure according to the invention and the triggering and insertion system according to the invention results in a slight reduction in the fuel ratio by volume and consequently a slight reduction in the neutron performance of the core. The volume of the central space reduces the volume ratio of fuel in the conveying fuel assembly by about 7% and about 0.6% in the core.

In addition, due to the design of the carrier assembly, it is possible to apply the fuel cycle of assemblies according to the state of the art, with minimal modifications, thus minimizing costs It is possible.

In addition, the structure of the assembly according to the present invention has little effect on the pressure loss of the fuel assembly and thus has little effect on the optimization of the thermohydraulics of the core.

The assembly according to the present invention in association with the triggering and inserting device according to the present invention achieves optimum utilization of the fuel assembly flow, which ensures maximum trigger speed and accuracy. Due to the center position of the shell in the assembly and its structure, the flow of the shell is very similar to the flow in the standard fuel assembly, so that its expansion represents the coolant temperature and thus the state of the assembly.

The present invention optimizes the reliability of the insertion of the side reaction. The capsule is mechanically isolated from the deformations of the fuel rod bundle because it is protected from the deformations by a lid with significant stiffness and there will be a large radial gap therein after it is inserted . The presence of the bundle of fuel rods between the lid and the hexagonal tube also has some ability to accommodate deformation of the hexagonal tube (the spacing between the fuel rods and the wire supports ≪ / RTI > is present), the capsule can be mechanically isolated from deformations affecting the lattice pitch.

We will now describe the details of the absorber assembly 2, the use of the absorber assembly further optimizes insertion reliability, and a set of absorber elements to be described can be easily inserted into the deformed capsule. The assembly (2) comprises spherically shaped absorbing elements (4) which slide on a flexible cable (6). This assembly is very flexible, which facilitates insertion into the capsule.

The distribution along the strings prevents sintering type phenomena and / or closure due to the arching effect which may occur in the case of solid stacks.

The spherical shape of the absorbing elements 2 has the advantage that it provides good insertion reliability of the absorbing elements into the capsule because the spherical shape is more easily inserted into the deformed structure and / Because it can be inserted. In addition, considering the thermal and thermomechanical aspects associated with the absorbing element itself, the spherical shape provides optimal cooling conditions for minimizing the core temperature. For example, the temperature gradient between the core and the outer surface is one-third lower than when the cylindrical shape is according to the state of the art.

The temperature stresses are also low because the temperature gradient between the core and the outer surface of the absorbing element is low. Thus reducing the risk of cracking.

The volume of the absorbing material for insertion of side reactions is optimally utilized, where the spherical shape minimizes the effect of neutron self-shielding per unit volume.

Said spherical elements can be solid and can be made from a single absorbent material. As a variant, the elements could be made of two different materials to optimize the properties of the elements. For example, a metal core having lower neutron absorption capacity (such as B ₄ C) than a ceramic material, but with a better thermal conductivity, may be made that reduces the core temperature and increases the margin to melting , The ceramic material may be retained for the peripheral wall. The two materials are selected such that there is a differential expansion between the two materials to ensure the mechanical integrity of the element. Such elements are made, for example, from metal spheres surrounded by two hollow hemispheres made of a ceramic material.

In another variant embodiment, the spherical elements are hollow. This structure is advantageous from a thermal point of view because it can reduce the maximum temperature experienced by the absorbent material, especially in the case of unwanted insertions. It also reduces the magnitude of the secondary stresses within the elements due to temperature, since there is no further differential expansion between the core and the periphery. From the neutron point of view, the material of the core is significantly less efficient than the material of the periphery due to its magnetic-shielding effect. As a result, the lack of core material in the hollow spheres is not particularly important.

The hollow spherical elements can be made as an assembly of two hollow hemispheres, or by making reaming in a solid sphere. In this latter case, metal inserts may be provided to reduce the spacing between the mechanical cables on each side of the reaming and the string cables.

The cable 6 can be made of braided metal fiber or dry ceramic fiber braid.

The assembly includes an attachment head as described above in one of the ends of the assembly cooperating with the fins 20.

Advantageously, the assembly includes at least one or preferably several (e.g., three) metal elements at the end of the assembly opposite to the end of the assembly that fits with the attachment head, Replace elements made of absorbent material. First, these elements form a stop for the absorbing elements. Secondly, they form partial neutron shielding from the fission core for the absorbing elements, because neutron flux can degrade the properties of the absorbing elements. For example, in the case of B ₄ C its thermal conductivity is reduced under irradiation, leading to an increase in the core temperature of the elements. The B ₄ C elements are partially protected by the insertion of metal elements forming the neutron shield.

Finally, they can form a ballast when the density of the material of the absorbing element is low. The presence of ballast can reduce the drop time of the assembly and reduce the risk of closure. In addition, these metal elements can absorb shock at the bottom of the capsule, which is particularly useful in the case of B ₄ C with low shock resistance.

Advantageously, mechanical damping means can be inserted between the absorbing elements. For example, Belleville washers may be used. These means need not be located between each pair of elements.

The cable is longer than the height of the stacks of the spheres, which determines the flexibility of the string, and the mechanical spacing can be adjusted by varying the strain of the components under irradiation, such as the expansion, swelling, The size is sized.

In addition, a radial clearance is provided between the reamings passing through the spheres and the cable.

In the event of a risk of such absorbent material, such as B ₄ C fragmentation, due to differential strain (swelling and swelling) in the reactor, the absorbing elements may be provided with a sleeve to form a metal cladding And the absorbing material is located inside the metal cladding.

The absorbing elements can be made of any neutron absorbing material. For example, it may be boron carbide (B ₄ C) in which ¹⁰ B is more or less concentrated.

Hafnium-based materials may be used. These materials have a high density which can reduce the drop time, they do not release gas under irradiation with radiation, and therefore do not cause swelling, and their side reaction capability is not significantly reduced under irradiation. Therefore, neutron efficiency and detectability levels are stable. It has neutron efficiency per unit volume much lower than B ₄ C, but has the advantage of having a thermal conductivity significantly higher than B ₄ C, and stable hafnium metal can be used under irradiation. Hafnium hydride, which has a high thermal conductivity under non-irradiated conditions and is stable under irradiation, can be used with hafnium metal.

It would also be possible to use heat resistant boride type absorbing materials, for example HfB ₂ and TiB ₂ , having a melting temperature of the order of 3300 ° C. It is also possible to use europium hexafluoride (EuB6). It is also possible to use Eu ₂ O ₃ . It does not generate gaseous products under irradiation. It also has high absorption capacity.

As a variant, it would be possible to envisage absorption elements made from different absorbing materials depending on the location of the absorbing materials throughout the string. For example, hafnium-based elements may be located at the bottom of the string and B ₄ C-based elements may be located at the top of the string. This distribution provides an essential part of the side-reaction required by the B ₄ C elements when in a non-inserted condition, while the bottom of the string places the hafnium elements at the top of the string Forms a neutron shield for the B ₄ C elements; At the same time they provide a significant complement to the side reactions at the beginning of the insertion and contribute to the total additional side reaction at the end of the insertion. In addition, hafnium elements do not introduce any risk of melting under the above insertion conditions, because their thermal conductivity under irradiation is not reduced in the suspended position.

Hafnium may also be used as a mitigating agent in the case of general core melting.

In the case of a pressurized water reactor, the materials used for the absorption elements are, for example, hafnium, Dy ¹¹ B ₆ , Gd ¹¹ B ₆ , Sm ¹¹ B ₆ , Er ¹¹ B ₄ , natural HfB ₂ and natural TiB ₂ < / RTI >

The coolant may be composed of any suitable liquid metal, for example sodium. Lead and lead-bismuth are other liquid metals that can be used in high-speed reactors. Sodium will also be used preferentially, because it provides excellent heat conduction. In addition, in the case of borated absorbents, the liquid metal medium avoids potential problems in the strong pressurisation of the enclosures (rods, capsules or otherwise) due to helium originating from ¹⁰ B . Finally, the high viscosity of the metal medium also allows marked progressive deceleration at the end of the drop distance, which severely limits the risk of fragmentation of the absorbent ceramic.

As an illustrative example, we will provide an illustration of the sizing of an assembly in accordance with the present invention.

The set of spherically shaped absorption elements may be 800 mm high. The size and mass of the absorbing elements depend on the material from which they are made:

In the case of B ₄ C in which ¹⁰ B is 48% enriched, the diameter is 35 mm and the mass is 1.8 kg,

In the case of HfB ₂ in which ¹⁰ B is 71% enriched, the diameter is 35 mm and the mass is 10.8 kg,

In the case of hafnium, the diameter is 67 mm and the mass is 46.9 kg,

In the case of Eu ₂ O ₃ , the diameter is 52 mm and the mass is 17.6 kg.

The integration of the triggering and insertion system based on 35 mm diameter spherical absorbent elements in the assembly corresponds to the removal of the two ring fuel rods, which has a 7% effect on the volume fraction of fuel in the transport fuel assembly, The effect of 0.6% on the volume fraction of the fuel within the combustion chamber.

Assuming a shell made of Z10 CNDT 15.15 B and a capsule made of W-5 Re, with the selected component dimensions, for a trigger temperature assumed to be equal to 660 ° C and a shell height of about 800 mm, The axial differential displacement of the shell relative to the capsule can be calculated as:

- between ambient and operating temperature: 5.65 mm,

- between operating temperature and trigger temperature: 1.44 mm.

The displacement of the attachment head due to the displacement of the fins 2 between the operating temperature and the triggering temperature can be calculated: the linear displacement of the pin is 5.4 mm and the angular displacement is 7.2 deg.

If so, the axial displacement of the attachment head of the assembly 2 between the operating temperature and the triggering temperature is 3.5 mm.

The set of absorbing elements in the form of a carrier assembly and a string of spherical elements according to the present invention are particularly suited for use in sodium cooled fast neutron reactors. They may also be applied to other types of nuclear reactors, such as high-speed reactors with other liquid metals such as lead or lead-bismuth, gas-cooled fast reactors, pressurized or boiling water reactors.

Claims (31)

A carrier assembly for a nuclear reactor comprising a box having a longitudinal axis X1 to be approximately oriented along a vertical axis, a fissile zone disposed in a lower end portion of the box, A free volume disposed within the upper portion of the fissile zone, starting from an end of a fission zone disposed on the side of the upper portion along the longitudinal axis X1 and extending across at least a portion of the fission zone along the longitudinal axis X1 And a triggering and insertion system (SI) extending in the fission zone, a free space in the fission zone, a lid (54) bordering the free space (52), and a trigger and insertion system Includes a capsule 10 having a longitudinal axis X, an assembly 2 to be inserted into the capsule, and a trigger to release the assembly to be inserted if the assembly is in an accident state, (DI), wherein the capsule (1) 0) is partially inserted into the lid 54, the triggering and insertion system being removably installed in the carrier assembly, the capsule including a gripping head, the triggering and insertion system (SI Is suspended above the lid (54). 2. The carrier assembly of claim 1, wherein the triggering and insertion device is disposed within an upper portion of the upper region of the box. 3. The method of claim 1 or 2, wherein the free space (52) is positioned within a central portion of the fission zone such that the longitudinal axis (X) of the triggering and insertion system is coaxial with the longitudinal axis (X1) ≪ / RTI > 4. The carrier assembly of any one of claims 1 to 3, wherein the assembly to be inserted is a neutron absorber and / or mitigating material type. 5. A carrier assembly according to any one of claims 1 to 4, wherein the longitudinal dimension of the assembly (2) to be inserted does not exceed half the total length dimension of the capsule (10). 6. The carrier assembly of any one of claims 1 to 5, wherein the capsule includes means for damping a drop of the assembly to be inserted at the end of movement of the assembly to be inserted. 7. The carrier assembly of any one of claims 1 to 6, wherein the capsule (10) comprises coolant supply orifices at an end of the portion of the capsule disposed within the lid. 8. Device according to any one of the preceding claims, characterized in that the carrier assembly comprises guiding means for the positioning of the triggering and insertion system (SI) in the fissure zone of the assembly, And is disposed at an end of the lid disposed on the same side as the free volume of the assembly. 9. A container according to any one of claims 1 to 8, wherein the box has a hexagonal cross-section, the lid (54) has a hexagonal outer cross section and a hexagonal or circular inner cross section, the capsule having a circular outer cross- Assembly. 10. Device according to any one of the preceding claims, characterized in that the assembly (2) to be inserted comprises a plurality of elements (4) hinged together with one another, one of the end elements Forms an attachment head (2.1) cooperating with the means (11) for holding the insertion device (DI). 11. A carrier assembly according to claim 10, wherein the elements (4) slide on a cable (6). 12. The carrier assembly of claim 11, wherein the cable is made of braided metal fibers or braided ceramic fibers. 13. A carrier assembly according to any one of claims 10,11 and 12, wherein each element (4) is spherical in shape. 14. A carrier assembly according to any one of claims 10 to 13, comprising a damping means between at least a pair of elements. 15. A carrier assembly according to any one of claims 10 to 14, wherein the elements (4) are formed from a plurality of absorbent materials. 16. A carrier assembly according to any one of claims 10 to 15, wherein said elements (4) comprise at least some elements in a first absorbent element and second elements in a second absorbent element. 17. A carrier assembly according to any one of claims 10 to 16, wherein the elements are hollow or comprise a peripheral core comprising a central core and two different materials. 18. The carrier assembly of any one of claims 1 to 17, wherein the triggering and insertion system is sensitive to temperature variations. 19. The carrier assembly of claim 18, wherein the triggering and insertion system is of a different expansion type. 20. The carrier assembly of claim 19, wherein the triggering and insertion system comprises locking means to prevent insertion of the assembly to be inserted at a temperature below the reactor operating temperature. 21. The carrier assembly of any one of claims 1 to 20, comprising means for detecting insertion of the assembly to be inserted by ultrasound telemetry. 21. The device of claim 20, wherein the triggering and inserting device comprises a longitudinally moving portion and a longitudinally secured portion formed from the capsule (10), wherein the capsule is located at a position where the inserted assembly (2) (11), the assembly to be inserted being releasable under the action of the moving part, the moving part comprising a locking means (12) formed by at least one first surface (24) Means for releasing the assembly to be inserted from the retaining means, releasing means formed by at least one second surface (26) called the release surface, and means for releasing the stop And means (19) for displacing the plane (24) and said release surface (26) along said longitudinal axis, said displacement means Wherein the stop surface (24) and the release surface (26) are formed by a shell (19) that is capable of expanding differently in the longitudinal direction relative to the capsule (10) The stop surface 24 moves axially away from the holding means 11 and the release surface 26 moves axially towards the holding means 11 and the coolant is moved to the normal reactor operating temperature , The stop surface (24) is moved away from the retaining means so that the retaining means is unlocked, and the release surface (26) is moved so that when the temperature of the coolant exceeds the threshold temperature, Wherein the carrier assembly is arranged to apply a thrust force on the holding means. 23. A device according to claim 22, coupled to claim 21, wherein said detecting means comprises at least one ultrasonic transducer disposed on the head of the capsule, a reflector mounted on the head of the capsule facing the transducer, Wherein the longitudinal position of the reflector 66 is controlled by whether the assembly to be inserted is held in place by the holding means 11 and the reflector 66 Is connected to the assembly to be inserted by an elongated element 64 which is installed to be freely slidable in a longitudinal reaming through the capsule head and in a non-inserted state Wherein the reflector (66) is held by a bearing on the assembly to be inserted. 24. The apparatus of claim 23, wherein the carrier assembly comprises an elastomeric means (68) that compresses in the presence of the assembly to be inserted, and if the element to be inserted is not present, expands the reflector (66) To apply tension to the elongate element (64) to move. 25. A capsule according to any one of claims 23 to 24, wherein a radial gap is provided between the shell (19) and the capsule (10) to delimit the coolant circulation channel between the shell and the capsule , And the shell (19) comprises orifices for circulation of the coolant in the channel. 26. Device according to any one of claims 22 to 25, characterized in that the holding means (11) comprises at least two pins (20) distributed around the longitudinal axis (X) and preferably three pins And wherein the pins are adapted to move between a position adjacent the longitudinal axis (X) for holding the assembly (2) to be inserted between the pins (20) X to move to a position spaced from said capsule (10). 27. The apparatus of claim 26, wherein the stop surface (24) is a radially disposed surface outside the fins (20) to prevent the fins (20) from moving away from the longitudinal axis (X) 26 is a surface perpendicular to the longitudinal axis X and the fins 20 have a cam surface 28 cooperating together to pivot the fins in a direction away from the longitudinal axis, ≪ / RTI > 28. A method according to any one of claims 22 to 27, wherein the shell (19) is made of an austenitic steel and the capsule (10) is made of a tungsten-based alloy, 19) is made of a work-hardened Z10 CNDT 15.15 B steel and the capsule is made of W-5Re. 29. A method according to any one of the preceding claims, wherein the material (s) of the neutron absorber is B ₄ C with a variable enrichment of ¹⁰ B, a hafnium metal such as HfB ₂ and TiB ₂ and the material of such heat-resistant boride type, yukbung digestion europium (EuB6), or Eu ₂ O _3, a metal cooling liquid, preferably a carrier assembly for a fast reactor of cooling is selected from sodium. 32. A method according to any one of the preceding claims, wherein the material (s) used for the neutron absorber is selected from the group consisting of hafnium, Dy ¹¹ B ₆ , Gd ¹¹ B ₆ , Sm ¹¹ B ₆ and Er ¹¹ B ₄ , a natural HfB _2, and a natural TiB ₂ . 32. A nuclear reactor comprising the carrier assembly and nuclear fuel assemblies of any one of claims 1-30.

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