CN107068213B - Passive triggering safety device for nuclear reactors during abnormal coolant reduction - Google Patents

Passive triggering safety device for nuclear reactors during abnormal coolant reduction Download PDF

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Publication number
CN107068213B
CN107068213B CN201611047649.4A CN201611047649A CN107068213B CN 107068213 B CN107068213 B CN 107068213B CN 201611047649 A CN201611047649 A CN 201611047649A CN 107068213 B CN107068213 B CN 107068213B
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section
mobile unit
neutron
coolant
support section
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CN107068213A (en
Inventor
丹尼斯·洛伦佐
伊莎贝尔·格纳特-狄来海
泽维尔·詹宁格罗斯
伯纳德·瓦伦丁
吉勒斯·阿瓦基安
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C9/00—Emergency protection arrangements structurally associated with the reactor, e.g. safety valves provided with pressure equalisation devices
    • G21C9/02—Means for effecting very rapid reduction of the reactivity factor under fault conditions, e.g. reactor fuse; Control elements having arrangements activated in an emergency
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C9/00—Emergency protection arrangements structurally associated with the reactor, e.g. safety valves provided with pressure equalisation devices
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C1/00—Reactor types
    • G21C1/02—Fast fission reactors, i.e. reactors not using a moderator ; Metal cooled reactors; Fast breeders
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C15/00—Cooling arrangements within the pressure vessel containing the core; Selection of specific coolants
    • G21C15/28—Selection of specific coolants ; Additions to the reactor coolants, e.g. against moderator corrosion
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C17/00—Monitoring; Testing ; Maintaining
    • G21C17/02—Devices or arrangements for monitoring coolant or moderator
    • G21C17/022—Devices or arrangements for monitoring coolant or moderator for monitoring liquid coolants or moderators
    • G21C17/025—Devices or arrangements for monitoring coolant or moderator for monitoring liquid coolants or moderators for monitoring liquid metal coolants
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C7/00—Control of nuclear reaction
    • G21C7/06—Control of nuclear reaction by application of neutron-absorbing material, i.e. material with absorption cross-section very much in excess of reflection cross-section
    • G21C7/08—Control of nuclear reaction by application of neutron-absorbing material, i.e. material with absorption cross-section very much in excess of reflection cross-section by displacement of solid control elements, e.g. control rods
    • G21C7/10—Construction of control elements
    • G21C7/103—Control assemblies containing one or more absorbants as well as other elements, e.g. fuel or moderator elements
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C9/00—Emergency protection arrangements structurally associated with the reactor, e.g. safety valves provided with pressure equalisation devices
    • G21C9/02—Means for effecting very rapid reduction of the reactivity factor under fault conditions, e.g. reactor fuse; Control elements having arrangements activated in an emergency
    • G21C9/027—Means for effecting very rapid reduction of the reactivity factor under fault conditions, e.g. reactor fuse; Control elements having arrangements activated in an emergency by fast movement of a solid, e.g. pebbles
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21D—NUCLEAR POWER PLANT
    • G21D3/00—Control of nuclear power plant
    • G21D3/04—Safety arrangements
    • G21D3/06—Safety arrangements responsive to faults within the plant
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Monitoring And Testing Of Nuclear Reactors (AREA)
  • Structure Of Emergency Protection For Nuclear Reactors (AREA)
  • Particle Accelerators (AREA)

Abstract

The invention relates to a passive triggering safety device for nuclear reactors, consisting of an assembly comprising: a protective sheath (200) having a coolant passing longitudinally therethrough; a mobile unit (100) rising in translation in the longitudinal direction (3) into the protective sheath (200) and comprising at least a neutron-absorbing section; the mobile unit (100) includes a first support section (110) longitudinally offset from the neutron-absorption section, and the protective sheath (200) includes a second support section (210). The first and second support sections (110, 210) are formed as described above, and a coolant flow Q flows longitudinally through the protective sleeve (200) when the first and second support sections (110, 210) are positioned toward one anotherfGreater than trigger flow QTriggeringWhen the movable unit (100) is in the supporting force configuration condition, the coolant applies a force to the movable unit (100) enough to support the movable unit (100) in the protective sleeve (200) and maintain the movable unit (100).

Description

Passive triggering safety device for nuclear reactors during abnormal coolant reduction
Technical Field
The present invention relates to the technical field of nuclear reactors. And more particularly to a passive, triggered safety device for interrupting neutron activity in a nuclear reactor when the flow of reactor primary coolant (a.k.a. heat carrier) is abnormally reduced.
The invention is particularly applicable, but not limited, to the field of fast neutron reactors, and in particular fast neutron reactors using liquid metallic sodium as a primary coolant.
Background
In reactors in which the core is cooled by a coolant, such as the liquid metal sodium cooled fast neutron reactor (RNR-Na), the control of reactivity is generally achieved by a number of safety devices that can stop the neutron reaction. The redundancy and technical differences of the safety devices provided in the same reactor should be able to minimize the possibility of the above-mentioned stoppage function malfunctioning.
The operating principle of these safety devices is generally to drop or insert an absorber rod (also known as a neutron absorber rod) into the core to effect shutdown. Typically, these absorber rods are translated up into a protective sheath in the reactor. An assembly of an absorber rod and a protective sleeve is disposed around the assembly containing the fissile material. These absorbent rods serve to protect the inner absorbent needle bundle.
These needles must be cooled. In fact, the irradiation will raise the temperature of the absorption pin. In particular, if neutrons are absorbed by the boron-10 isotope (10B), thermal power is generated in the boron carbide material (B4C) constituting the absorption pin. However, in order to ensure various functions and/or mechanical strength of the absorbing needle member, the temperature of these components must be limited. This is why the absorption pin has to be cooled.
The insertion of the rods into the core has hitherto been triggered by an external electrical control device or by the absence of an electrical signal, in the sense that the main safety devices of the sodium cooled fast reactor (RNR-Na) are active devices. For the next generation of sodium cooled fast reactors (RNR-Na), passive auxiliary safety devices are being developed for use in case of failure of the primary safety device (active safety device). These passive auxiliary safety devices must be able to drop the absorber rods into the core without detection devices or without operators. Conversely, in the event of physical phenomena sensitive to the triggering device (such as an abnormal reduction in the flow rate or an increase in the temperature of the primary coolant), it is necessary to be able to trigger directly the action of dropping the absorber rod.
The present invention relates to the latter type of safety device.
In order to ensure that the drop action of the absorber rods can be triggered passively when the flow of the primary coolant is abnormally reduced, a number of solutions have been proposed.
It should be noted that by primary is meant a circuit whose coolant directly carries the heat released in the core out of the stack. The circuit is in direct contact with the assembly containing the fissile material.
The first solution is referred to in FR 1362783. In the solution, it is proposed to achieve the rising of the absorber rods by means of a fluid generated by the coolant circulation and a guide pipe; in this case, the coolant will be subjected to viscous drag. By reducing the coolant flow, the absorber rods can be dropped into the guide tubes; until there is no coolant flow, the absorber rods are placed in their shutdown position.
It has been proved in practice that in the above-mentioned "float-sink" solution, we cannot control the vertical position of the absorber rods precisely, nor prevent undue movement of the absorber rods and the associated changes in reactivity.
The solution described therefore does not ensure that the action of dropping the absorber rod is not accidentally triggered in any case.
Please refer to the comparison document RU 2069019. In the technical proposal, an absorption rod supporting area is arranged above the reactor core through the matching between the outer surface of the neutron absorption section of the absorption rod and the inner surface of the protective sleeve.
It has been found in practice that, in the above-described solution, the suction needle cannot be sufficiently cooled by the coolant flowing through the assembly. As previously mentioned, insufficient cooling of the absorption needle may adversely affect various functions and/or mechanical strengths of its components.
Furthermore, the stability of the above-mentioned solution has proved to be relatively poor.
Therefore, there is a need to propose a solution that does not present, or at least limits, the drawbacks of the known solutions described above.
Disclosure of Invention
The invention relates to a passive triggering safety device for a nuclear reactor with an active area heat brought out of the reactor by a coolant, comprising an assembly comprising:
a protective sheath extending approximately vertically along a longitudinal direction with a coolant flowing longitudinally therethrough;
a mobile unit that ascends in translation along a longitudinal direction into the protective sheath and includes at least a neutron-absorbing section including at least a neutron-absorbing material that extends mainly along the longitudinal direction and is configured to be flowed longitudinally by the coolant;
furthermore, the mobile unit comprises a first support section longitudinally offset with respect to the neutron-absorption section;
and, the protective sleeve further comprises a second support section; the first support section and the second support section are formed as described above, and if the first support section and the second support section are disposed in an opposing manner in a lateral direction perpendicular to the longitudinal direction, the first and second support sections will collectively define a coolant flow-through space, assuming that the space is the S1 section (or the space j 1):
coolant flow Q when flowing longitudinally through the protective sheathfThe coolant flow rate Q is less than that of the action of triggering the absorption rod to fall to the coreTriggeringWhen the coolant applies force to the movable unit, the force is enough to support the movable unit in the protective sleeve and keep the movable unit in a vertical state under the action of the supporting force;
when flow rate Qf<QTriggeringWhen the force applied by the coolant to the movable unit is not enough to support the movable unit in the protective sleeve and not enough to maintain the vertical state of the movable unit under the supporting force, the movable unit will descend along the protective sleeve under the action of gravity to the end position, namely the falling state of the absorption rod;
if the first and second support sections are not disposed in an opposing manner along the transverse direction, the first support section and the inner surface of the protective sheath facing the first support section will collectively define a coolant flow space, i.e., the section S2, such as the section S2>S1 paragraph, even if the flow rate Qf>QTriggeringThe force applied by the coolant to the mobile unit is also insufficient to cause the mobile unit to translate back up into the protective sheath.
The present invention therefore provides a simple and effective solution to passively trigger the fall of neutron absorbing material (usually absorbing pins) into the core active area of a nuclear reactor.
Once coolant flow rate Qf<QTriggeringThe movable unit automatically falls down when the coolant flow is insufficient to support the movable unit. The neutron absorbing material contained in the active unit then falls down into the core active area of the reactor, stopping the neutron reaction.
The above-described triggering mode can be realized only if the coolant flow is reduced. Such a security device is therefore completely passive. Unlike the primary safety device, which is automatically activated by a control device or manually activated by an operator, the passive trigger type safety device does not rely on an electrically controlled trigger, thereby improving safety.
For example, when the control device fails, it may not be possible to trigger the action of dropping the absorber rods in the main safety device of the active type, and these absorber rods cannot then drop into the core. Conversely, according to the invention, once the coolant flow has decreased below the trigger threshold QTriggeringThe movable unit falls.
Furthermore, according to the present invention, the system of the passive type safety device can accurately control the vertical position of the movable unit even under the influence of the flow rate variation.
However, in the solution proposed in the aforesaid document FR13622783, it is not possible to control the position of the mobile unit and to prevent inappropriate movements and associated reactivity variations of the mobile unit, for example in the handling condition (non-zero primary circuit coolant flow) and in the power condition (raising of the absorber rods due to sudden drops and rises in coolant flow). In fact, the coolant flow section between the absorber rods and the protective sheath is the same regardless of the vertical position of the absorber rods. For example, if the mobile unit has fallen due to a decrease in coolant flow, then the coolant flow increases until it is above the triggering threshold, the mobile unit will be released, re-rising above the core, thus stopping the effect of the safety device on neutron activity.
Within the scope of the invention, the first support section is intended to be placed in the event of the mobile unit falling due to an abnormal reduction in the coolant flowIs no longer disposed opposite the second bearing section and the mobile unit is no longer raised back, even if the coolant flow subsequently increases above the trigger threshold QTriggeringBecause the flow-through space between the protective sheath and the first support section is so large that the force exerted by the coolant is not sufficient to lift the mobile unit back.
In addition, when Qf>QTriggeringThe invention has many advantages on the basis that the first support section is vertically offset relative to the neutron absorption section and the second support section faces the neutron absorption section but is not perpendicular to the neutron absorption section when the support function is ensured. In fact, the support function and the cooling function of the neutron-absorption section are complementary. In fact, in ensuring the bearing function, according to an embodiment, the coolant first passes through the flow space defined by the two oppositely disposed bearing sections and then through the flow space defined by the neutron-absorbing section, or in the reverse order.
The support of the mobile unit is therefore ensured by all the coolant passing through the protective sheath.
Further, cooling of the neutron-absorbing material may be ensured by all or at least a majority of the coolant passing through the protective sheath and then through the neutron-absorbing section. Thus, even if the coolant flow is limited, the cooling of the neutron absorbing material (typically the absorber pin) can be very efficient. Typically, to cool a bundle of needles consisting of about 19 needles, the coolant flow must reach 2.5-3kg liquid sodium per second. When the rated flow rate of the coolant, i.e. 6kg liquid sodium per second, is reached, the invention makes it possible to perform a large amount of cooling and to support the mobile unit.
However, in the solution proposed in the aforementioned reference RU2069019, the coolant flow must be shared to ensure the support function and the cooling function of the neutron-absorption rods. It follows that, with the same reactor configuration, we have to develop higher component flows, and this approach has two significant drawbacks: reducing the cooling efficiency of the reactor (the total flow of the core is not optimal); if the assemblies are sub-cooled (the temperature difference is large compared to the surrounding fuel assemblies), the risk of hot cracking of the structure above the core is increased.
Furthermore, according to the invention, the support function is ensured by a separate section containing neutron absorbing material, and also by a section whose design and dimensions can be precisely controlled, in order to increase the accuracy and reliability of the support function. In contrast, in the solution proposed in the reference RU2069019, the neutron-absorption section provides a hydraulic fit to generate the support function, and the dimensional control of the support section is very complex, since the neutron-absorption section itself is also very complex in structure, involving a plurality of component parts. However, inaccuracies in the spacing between the first and second support sections (tenths of a millimeter) can either prevent the mobile unit from rising to affect its fall (which can have an effect on the availability of the reactor) or can be triggered with a delay during the transient flow (failure of the safety function of the device).
In addition, the present invention may have at least any one of the following features:
the first support section is supported by an outer surface of the mobile unit.
-the second support section is arranged on the outer surface of the protective sleeve;
the protective sheath comprises at least one sleeve inside the duct and the second bearing section is formed by this sleeve;
the second bearing section (usually the sleeve) is integrally machined. In this way, the second bearing section can be produced very precisely by means of machining.
-the first support section is integrally machined. In this way, the first support section can be manufactured very precisely by means of machining.
The longitudinal direction is vertical.
The second bearing section extends longitudinally over only a portion of the longitudinal dimension of the protective sheath. For example, the ratio of the length of the second support section to the length of the protective sleeve (above the base) is 1/12.
Thus, only the relatively precisely positioned mobile units within the protective sheath can achieve support.
The neutron absorbing section comprises a small tube containing a plurality of absorbing pins extending longitudinally and containing neutron absorbing material.
The mobile unit comprises a thrust wall, so that the coolant passing through the protective sheath exerts a thrust force on the thrust wall, a component of which counteracts the weight of the mobile unit.
The configuration of the apparatus is as described above, then: when the coolant flow rate cannot ensure the support of the movable unit in the protective sheath, the movable unit descends by gravity until the end point is reached, thus ensuring the falling state of the absorber rod.
The configuration of the apparatus is as described above, then: in the falling state of the absorber rod, the neutron-absorbing section is arranged in the lateral direction and faces an area of the protective sheath, namely the core area facing the reactor core active area.
The first support section is located vertically below the neutron-absorption section.
In the support configuration, the first support section is located vertically below the core region. In other words, the first support section is located upstream of the neutron-absorption section, relative to the flow of coolant in the protective sheath.
The second support section is located vertically below the core of the protective sheath, which faces the core of the reactor.
Thus, the first support section is not in the neutron stream. Therefore, the irradiation dose to which the first support section is subjected is limited. However, the micro-damage caused by irradiating metallic materials under neutron flux is macroscopically manifested as dimensional change, particularly as dimensional expansion with increasing irradiation dose. Thus, compared to the solution where the first support section is arranged in the neutron flow, the invention ensures its functionality and does not affect the geometry of the first support section, which makes the safety device more reliable.
The first support section is arranged in the longitudinal direction with a separation section between it and the neutron-absorption section. The longitudinal length of the partition is at least equal to the longitudinal travel of the mobile unit between the support condition and the fall condition.
The mobile unit comprises a positioning pin supporting the first support section.
The locating pin is part of the foot of the absorber rod. In the longitudinal direction, the positioning pin corresponds to the bearing section; in the transverse direction, the positioning pin corresponds to a thrust wall.
The positioning pin is located at the bottom of the mobile unit.
The lower end of the dowel pin contributes to forming a coolant thrust wall to ensure the support of the mobile unit.
The first support section comprises a support zone on a support wall supported by the dowel pin.
The support wall is cylindrical.
The pin is a one-piece component, typically made of one of the following materials or an alloy thereof: EM10 ferritic-martensitic stainless steel. Of course, other steels or metals (e.g., refractory metals) are contemplated depending on the operating conditions of the reactor.
The pin is hollow and defines a closed internal volume.
The second bearing section is a sleeve supported or formed by the inner surface of the protective sheath;
the inner surface of the sleeve is cylindrical;
the distance between the sleeve inner surface and the dowel bearing wall defines the S1 segment and the j1 spacing.
According to a first embodiment of the invention, the passive triggering safety device may have at least any one of the following optional features, alone or in combination:
the separation section comprises at least one tie rod to ensure a mechanical connection between the neutron-absorption section and the first support section.
The partition comprises at least two reinforcements (preferably three). These stiffeners are usually tie rods, which extend radially from the center of the mobile unit to the inner wall of the mobile unit; and extends longitudinally from the neutron absorbing section to the first support section.
According to a cross-sectional view, the tie rods and the reinforcement occupy less than 20%, preferably less than 10%, and most preferably less than 5% of the cross-sectional area of the neutron absorbing section.
Thus, the absorber pin foot configuration facilitates coolant circulation within the safety device.
The absorbent club foot structure is provided with a pull rod and reinforcing members (preferably, three reinforcing members) arranged in 120 ° and has the following advantages: mechanical guidance over the entire stroke is provided; better mechanical rigidity; the hydraulic robustness for disabling the support area is strong; light weight, which is important for support; and low load loss.
The separation section includes at least one perforated tube to ensure mechanical connection between the neutron-absorption section and the first support section.
Preferably, the perforated tube comprises a plurality of openings extending mainly in the longitudinal direction.
These openings are distributed over the surface of the perforated tube.
These openings are distributed over the longitudinal dimension of the partition.
Thus, the absorber pin foot configuration facilitates coolant circulation within the safety device.
The outer cross-sectional dimension of the entire perforated tube is substantially equal to the outer cross-sectional dimension of the first support section. Thus, the outer cross section of the mobile unit comprises at least from the neutron absorbing section to the first support section.
The first support section is located vertically above the neutron-absorption section.
In the supported condition, the first support section is vertically above the core region of the protective casing.
In this embodiment, if the first support section is located on the foot of the absorbent rod, i.e. vertically below the core region of the protective sheath in supported condition, the first support section is still far from the neutron flux. It follows that the amount of radiation received by the first support section is limited to avoid radiation induced expansion.
Depending on the distance between the core and the top of the assembly, the choice is made whether the support structure is positioned on the absorber rod foot or on the tie rod.
The first support section extends longitudinally between the top portion constituting the upper end of the mobile unit and the neutron-absorption section.
According to an embodiment of the invention, the first support section is constituted by a raised structure located between the top of the tie rod and the neutron absorbing section, and is supported by the mobile unit. The convex structure increases the cross section of the movable unit.
The mobile unit comprises a tie rod extending at least from the upper end of the mobile unit to the neutron absorbing section. And the first supporting section is a convex structure supported by the pull rod between the upper end of the movable unit and the neutron absorption section.
The projection arrangement is arranged between two tie rod segments.
The lower end of the raised structure contributes to forming a coolant thrust wall to ensure support of the mobile unit.
-said raised structure is hollow, provided with a plurality of coolant discharge holes.
The raised structure is a longitudinally extending cylindrical wall and the second bearing section is a sleeve supported or formed by the inner surface of the protective sheath. The space j1 between the outer surface of the cylindrical wall of the boss structure and the inner surface of the sleeve is referred to as segment S1.
According to an embodiment of the present invention, the passive triggering safety device may have at least one of the following optional features, alone or in combination:
the safety device includes a movable unit damper for a falling process of the movable unit. The damper includes:
-a first damping member supported by the mobile unit and arranged in contact with the coolant;
-a second damping member supported by the protective sheath and arranged to be in contact with the coolant.
The first damping member and the second damping member are formed as described above, so that the first damping member enters the second damping member before the movable unit falls and reaches the stroke end position in the falling state, and then the first and second damping members cooperate with each other to form a viscous damper.
According to an embodiment of the invention, the first support section and the first damping member or the second support section and the second damping member are supported by the same member.
Therefore, the member supported by the protective cover or the movable unit ensures the viscous damping function and the bearing function.
With this structure, the present invention has an important advantage in terms of installation restriction. Further, this structure is particularly advantageous in solving the problem of the size limitation inside one element. The invention thus makes it possible to reduce the number of critical components, for example components which have to be machined particularly precisely.
The number of key components is reduced, and the reliability of the passive trigger type safety device is improved.
And the manufacturing cost of the device can be reduced.
According to an exemplary embodiment of the invention, the longitudinal height of (at least a part of) the first support section and the first damping member or the second support section and the second damping member is the same.
In addition, the present embodiment equipped with the damper may have at least any of the following features:
the longitudinal heights of (at least a portion of) the first support section and the first damping member or the second support section and the second damping member are the same.
According to an embodiment equipped with a damper, the passive triggering safety device may have at least any one of the following optional features, alone or in combination:
the second bearing section and the second damper are supported by the same component. The protective sheath comprises at least a sleeve from which the support member within the protective sheath is formed.
In this embodiment, a damping system is designed to be placed on the same fixed part to facilitate support. Such an embodiment has the following advantages:
for the known damping elements, there is no need to modify the length and the stroke of the mobile unit when operating at a height that is higher than the height required for the damping function, and therefore no effect on the assembly height;
furthermore, there is no need to design a damping zone, since the function of the damping zone actually reduces the effective damping, which corresponds to a guide zone. Therefore, in this embodiment, there is no need to create a new guide area, which will facilitate the plug-in reliability of the movable unit in the damper (and thus the speed of the fall) when facing the risk of jamming, chattering, etc. These risks of jamming, chatter, etc. are generally caused by structural deformations of the device under irradiation, such as deflections/deflections. According to this embodiment, the solution improves the reliability of the insertion of the damper movable part into the sleeve part, such insertion being performed in the guide zone constituted by the sleeve.
In this embodiment, the damping function and the bearing function (at least partly) are ensured by the sleeve. The embodiments may have other advantages.
The jacket comprises a chamber filled with a coolant, said chamber forming the above-mentioned second damping member. The first damping member forms an insert for inserting into the chamber and driving the coolant before the movable unit reaches its end-of-travel position.
The sleeve is arranged longitudinally between the bottom of the active unit and the neutron absorbing section, preferably between the bottom of the active unit and the top of the active unit.
The shape of the first damping member facilitates its entry into the chamber of the sleeve. The chamber is circular with a transverse annular opening. Through the opening, the first damping member will be inserted into the chamber before the movable unit reaches the stroke end position in its falling state. The first damping member forms a small tube whose free end is shaped to facilitate its passage into the chamber through the opening.
The second bearing section is formed by the inner surface of the sleeve.
-said chamber is formed inside the sleeve, having a bottom. The second support section is formed by the inner surface of the sleeve, at least partially facing the chamber, in a longitudinal arrangement.
According to one embodiment:
the second damping member defines a concave portion and has at least one chamber filled with a coolant, and the first damping member defines an insert for inserting into the at least one chamber and extruding the coolant before the movable unit reaches its end-of-travel position.
The second damping member forms a stopper portion for the movable unit.
The first damper is located longitudinally between the lower end of the mobile unit and the top end of the mobile unit, and preferably, the first damper is located longitudinally between the lower end of the mobile unit and the neutron absorbing section.
The first damping member defines an insert and the second damping member defines a chamber for facilitating entry of the insert into the chamber. Preferably, the cavity has a cross-section in the shape of a ring centered on the translation axis of the mobile unit and extends longitudinally from an opening at the upper end of the chamber to a position at the bottom of the chamber.
The chamber is circular with a transverse annular opening. Through the opening, the first damping member will be inserted into the chamber before the movable unit reaches the stroke end position in the falling state. Preferably, the first damping member forms a small tube, the free end of which is shaped to facilitate its passage into the chamber through the opening.
The insert part of the first damping member enters the chamber, preferably with one end freely insertable into the chamber and the other end connected to the remaining part of the mobile unit. Preferably, the first damping member is attached directly below the neutron-absorption section.
The second damping member is formed by a ferrule carried by the inner surface of the sleeve and the second support section is formed by the inner surface of the sleeve.
The chamber of the second damping member has a bottom and a thickness, and the second support section is formed by an inner surface of the sleeve.
The second support section and the second damper are disposed opposite to each other and at least a part of them are the same in height in the longitudinal direction.
According to the damping device of another embodiment, the passive trigger safety device may have at least any one of the following optional features, alone or in combination.
In the damping device provided in the embodiment:
the first support section and the first damping member of the device are supported by the same member which forms the positioning pin on the mobile unit.
The outer surface of the locating pin of the device defines a first support section and a first damping member.
The protective sleeve comprises at least one guide part for guiding the movable unit to translate;
the guide section comprises three cushion blocks which are radially and regularly distributed around the translation shaft of the movable unit;
the guide section comprises a cushion block support ring arranged on the protective sleeve;
the guide section is longitudinally positioned in the protective sheath to facilitate movement of the mobile unit, preferably, the guide member is located at a lower end of the neutron absorbing section when the mobile unit is in a falling state; when the movable unit is unsupported, the guide member is located at an upper end of the neutron absorption region.
The cooperation between the outer surface of the neutron absorbing section and the pad thus ensures that the mobile unit is guided accurately in the sleeve throughout operation.
Another aspect of the invention relates to a passive reaction termination device comprising a passive triggered safety device according to the invention and a gripping device for the positioning and gripping of the mobile unit. The grasping means can move the safety device to move it into a specific position or to return it from a specific position to the home position.
Another aspect of the invention relates to a nuclear reactor comprising a fissionable zone and a coolant circulating in a circuit thereof, and comprising at least one device provided according to the invention.
The nuclear reactor is preferably a fast neutron type reactor.
Drawings
The figures are given as examples and do not limit the invention. They represent only one embodiment of the present invention.
Figure 1 is a longitudinal section of a passive switching safety device in a lifting structure according to an embodiment of the invention. I.e. a longitudinal section of the passive switching safety device when the mobile unit is under the effect of a lift force generated by a heat exchange fluid flowing longitudinally through the protective sheath.
Fig. 2 shows the safety device in the falling state, i.e. the mobile unit is not supported but falls under gravity into the protective sheath in the end position.
Fig. 3 comprises fig. 3a and 3 b. Fig. 3a shows the safety device in a state in which the mobile unit is descending under gravity and has not reached the end position in the protective sheath. Fig. 3b is a cross-sectional view of the safety device between the protective sheath guide section and the neutron absorbing section of the mobile unit.
Fig. 4 includes fig. 4a to 4 c. Fig. 4a shows fig. 1. Figure 4b is a cross-sectional view of the safety device shown in figure 1, the cross-section being between the spacer and the support arrangement. Figure 4c is a cross-sectional view of the safety device shown in figure 1, the cross-section being between the first support section and the payout arrangement.
Fig. 5 includes fig. 5a to 5 c. Fig. 5a shows fig. 1. Figure 5b is a cross-sectional view of the safety device shown in figure 1, the cross-section being between the spacer and the support arrangement. Figure 5c is a perspective view of the end point of the movable unit of the security device of figure 1.
Fig. 6 includes fig. 6a to 6 c. Fig. 6a shows fig. 2. Figure 6b is an enlarged cross-sectional view of the safety device shown in figure 6a between the damping device and a fall configuration. Figure 6c is an enlarged perspective view and cross-sectional view of the safety device shown in figure 6a, the cross-section being between the damping device and the fall configuration.
Figure 7 shows a number of operating steps of the invention.
Fig. 8 comprises fig. 8a and 8 b. Fig. 8a is a longitudinal sectional view of a safety device according to an example of the present invention. Figure 8b shows the safety arrangement of figure 8a in a lowered configuration.
Fig. 9 includes fig. 9a to 9 c. Fig. 9a shows fig. 8 b. Figure 9b is an enlarged view of the safety device shown in figure 8 a. Fig. 9c is a cross-sectional view of the safety device shown in fig. 8a, the cross-section being between the sleeve and the perforated tube.
Fig. 10 includes fig. 10a to 10 c. Fig. 10a is a longitudinal sectional view of a safety device according to an example of the present invention. Wherein the first support section is located above said neutron absorber, and fig. 10b is an enlarged view of fig. 10a, the cross-section being located between the first and second support sections. Fig. 10c is a perspective view of fig. 10 b.
FIG. 11 is an enlarged view of the mating of the first and second bearing segments in an embodiment of the invention.
The figures are schematic representations, not necessarily to scale, for the understanding of the invention. In particular, the spacing between the first support section and the inner surface of the protective casing or the inner surface of the sleeve need not be present in practice.
Detailed Description
In a nuclear reactor, heat from the fission region is transferred to at least one coolant. Typically, the device includes several components. Some assemblies include fissionable material and others include control rods for controlling neutron activity. The remaining components are used to form a passive triggered safety device to prevent or slow neutron activity in the event of an abnormal reactor operation.
A passive trigger-type safety device provided by an embodiment of the present invention will now be described in detail with reference to fig. 1 to 6.
The apparatus essentially comprises a protective sheath 200 for insertion into the core of the reactor. A portion of the protective sheath 200 serves as a core zone 240 that faces in a transverse direction that is perpendicular to the longitudinal direction 3 of the fission zone 10 of the reactor. Because the protective sleeve 200 is secured during operation of the reactor, the core zone 240 is always located below the fission zone 10.
The protective sheath 200 extends in the longitudinal direction 3. During operation, the longitudinal direction is inclined in the horizontal direction. Typically, the longitudinal direction 3 is vertical, as shown in the figures.
The protective sheath 200 extends from an upper end 202 that allows the handling assembly to be grasped and a module bottom 204 that serves to locate the assembly at the bottom of the reactor and to ensure the supply of coolant, such as liquid sodium.
The protective sheath 200 is used to allow coolant to flow laterally through the sheath 200 from an inlet 205 at the bottom 204 of the assembly to an outlet 203 at the upper end 202 and illuminated by a supply light 205.
Preferably, the protective sheath 200 comprises an outer sheath formed of a partial hexagonal tube 201. The longitudinal walls of the sleeve 200 are sealed.
The passive trigger-type safety device further comprises a movable unit 100 which is disposed within the protective sheath 200 and moves in the longitudinal direction 3 of the protective sheath. In the nuclear industry, the mobile unit is also referred to as a rod. The movable unit 100 mainly extends along the longitudinal direction 3 and therefore, as shown in the figure, performs an operation in a vertical direction. The mobile unit 100 extends from a top 101 to a bottom 103. The active unit includes a neutron absorbing section 130, including neutron absorbing material, located between the top 101 and bottom 103.
For fast neutron nuclear reactors cooled by liquid metal, the neutron-absorbing material may be boron carbide (B)4C) It is a little rich10B. Optionally, the neutron absorbing material may also be a hafnium-based material. Because the material has high density, the reduction time is shortened, the release of gas under irradiation is avoided, and the expansion is avoided, and the strain resistance of the material is not obviously reduced. Alternatively, the neutron absorbing material may be a refractory boride absorbing material, such as HFB2And TiB2The melting point is about 3300 ℃. Europium hexaboride EuB may also be used6Or Eu2O3They do not release gas under irradiation and the absorption capacity of these materials is strong.
In pressure water cooled reactors, the absorbing material may be, for example, a hafnium compound, Dy11B6、Gd11B6、Sm11B6、Er11B4Natural HfB2Or natural TiB2。
The neutron-absorption section 130 generally includes an absorbent pin bundle 131 enclosed within the body 104. The needle bundle 131 extends mainly in the longitudinal direction 3. The coolant flows laterally through the neutron-absorption section 130 from the assembly bottom 204 to the outlet 203 to cool the neutron-absorption section. As can be clearly seen in fig. 3b, the mechanical connection 132 of the neutron-absorption section 130 is located between the absorption needle bundles 131. The connectors 132 define channels 133 for cooling the coolant flowing through the neutron-absorption section 130 by flowing the coolant transversely through the channels.
In fig. 7, the top 101 of the mobile unit 100 is mated with a grapple type gripping device 300 for holding the mobile unit 100 in place within the protective sheath 200 during operation.
The mobile unit 100 further comprises a first support section 110 for triggering a falling action of the mobile unit 100 when the flow rate of the coolant is below a predetermined threshold. This function will be described in detail later.
The mobile unit 100 further comprises a first damping member 140 cooperating with a second damping member 220 provided on the protective cover 200 for providing damping to the mobile unit 100 during a fall. The first and second damping members 140 and 220 are described in detail below.
The passive triggering mechanism of the active unit 100 is explained below. By this mechanism, when the flow rate of the coolant abnormally decreases and falls below the stroke trigger threshold QTriggeringAt this time, the movable unit 100 descends by gravity. Thus, the mobile unit 100 may reach the end position of the fall process, with the neutron-absorption section 130 being transverse with respect to the fission zone 10 of the reactor and the core zone 240 of the protective sheath 200.
The first support section 110 of the mobile unit 100 has an outer wall opposite to the inner wall of the protective sheath 200. The inner wall of the protective sheath 200 narrows in cross-section and forms a second support section 210. In the longitudinal direction, narrowing of the cross-section of the protective sheath 200 is limited. Generally, the second support section 210 extends longitudinally less than 1/5, preferably less than 1/10, and more preferably less than 1/15 of the length of the protective sheath 200. Specifically, the ratio between the length of the second support section 210 and the length of the protective sheath 200 above the bottom of the reactor is about 1/12.
The space defined by the first support section 110 and the inner surface of the protective sheath 200 enables coolant to flow in the protective sheath 200. This space is reduced when the first support section 110 is disposed laterally relative to the second support section 210.
Preferably, the first support section 110 is longitudinally displaced relative to the neutron-absorption section 130. In the embodiment illustrated in fig. 1-9 and 11, the first support section 110 is located below the neutron-absorption section 130. The advantages of this embodiment will be described later. According to another embodiment, as shown in FIG. 10, the first support section 110 is located on the neutron-absorption section 130. In all of the above embodiments, the first support section 110 is not disposed on the neutron-absorption section 130, and is spaced from the neutron-absorption section in the longitudinal direction 3.
The first support section 110 and the second support section 210 are arranged as follows: the first support section 110 and the second support section 210 are arranged facing each other in a transverse direction perpendicular to the longitudinal direction 3 to form a fall. The first support section 110 and the second support section 210 together define a space through which a coolant flows. The space has a segment S1, and if the space j1 on the periphery of the entire active cell 100 is regular, the interval may define the space.
By arranging the first support section 110 and the second support section 210, or facing each other, under the supporting action, the section S1 (or the space j 1) is arranged as follows:
coolant flow Q when flowing longitudinally through protective sheath 200fGreater than a predetermined flow rate QTriggeringAt this time, the coolant applies a force to the movable unit 100 sufficient to offset the gravity of the movable unit 100 in the protective sheath 200, so that the movable unit is in a vertical state under the supporting force.
In particular, the mobile unit 100 also comprises at least one push wall 117, the surface area of which, based on its projection perpendicular to the direction of flow of the coolant (i.e. determined according to a transverse projection), is greater than zero. The force exerted by the coolant against the thrust wall 117 is opposite to the mass of the mobile unit 100.
When flow rate Qf<QTriggeringAt this time, the coolant applies insufficient force to the movable unit 100 to support the movable unit 100 in the protective sheath 200, and also does not sufficiently maintain the movable unit 100 in a vertical state under the support force. Therefore, the mobile unit 100 will descend along the protective sheath under the effect of gravity until reaching the end-of-travel position. In this position, the neutron absorbing section 130 faces the core 10 to stop or slow neutron activity.
The first support section 110 and the second support section 210 or the facing surfaces thereof are arranged as follows: when the first support section 110 and the second support section 210 are not laterally opposed to each other, the first support section 110 and the inner wall facing the first support section 110 together define a space for the coolant to flow through, and the space hasHaving a segment S2, and S2>S1 (or space j 1)>j1) In that respect The segment S2 or the segment S1 is defined by: if the flow rate Q of the coolantfAbove the trip value (which is, according to regulations, 110% of the flow value at rated power), the force exerted by the coolant on the mobile unit 100 is not sufficient to support the mobile unit 100 in the protective sheath 200, and therefore, when descending at normal rate, the rod cannot be released from the fissile region 10, being separated from it only by means of the gripping means 300.
Thus, according to the above embodiment, the present invention proposes a solution to form a hydraulic support zone located under the core by the cooperation of the first support section 110 and the second support section 210. When the mobile unit 100 is unsupported, the hydraulic support area is not activated.
The safety device provided by the invention is firm, efficient and practical. In fact, it has the following advantages:
the partial hydraulic zone formed by the first support section 110 is located below the neutron absorption section 130, and the hydraulic (support) and thermal fluid (beam cooling) functional zones are not coupled, but are in series. This allows a good control of the cooling of the needle bundle 131 and the lifting of the movable unit 100;
the flow rate distributed by the assembly can be used to actually lift and cool. Thus, when the radial gap is equal to the area of the support region, theoretically, the load-bearing zone of the absorber rod foot requires less coolant than the lift zone located in the neutron absorption section, i.e., the absorber rod itself can support a heavier (or equivalent) material;
the cooling of the needle bundle 131 is the same at the insertion stage, regardless of the position of the needle bundle in the longitudinal direction.
Flexibility in manufacturing tolerances of the elevated area components: in the lifting zone, if the first support section 110 and the second support section 210 are formed of countless small segments, a radial clearance of a few millimeters (1/10 for manufacturing tolerance) must be easily observed;
the design of the needle bundle 131 has a certain freedom: the change in the size of the needle bundle 131 does not affect the size of the first support section 110 and the second support section 210. This is not only beneficial for practical development (the work of the project), but also beneficial for extending the life of the reactor;
providing convenience for computing; and
the failure caused by mechanical problems is easily controlled during the falling or floating state of the mobile unit.
The present invention is not limited to the cylindrical wall defining the space through which the coolant flows, i.e., the section S1. It may be of any shape as long as it can ensure the support function and trigger the fall.
Preferably, the protective sheath 200 comprises a sleeve 211 disposed inside the hexagonal tube 201, the sleeve 211 forming the second support section 210. By applying force to the sleeve 211, the hexagonal pipe 201 can be applied with force. Compared with the prior art in which force is directly applied to the hexagonal tube 201, the method reduces manufacturing complexity and cost. For example, the size of the protective sleeve can be well controlled by the sleeve 211.
Preferably, according to the embodiment shown in fig. 1 to 9 and 11, the first support section 110 is defined by the positioning pins 112 of the mobile unit 100. The positioning pin 112 is provided on the bottom portion 103. The locating pin 112 and the base 103 form at least a portion of a thrust wall 117. In the illustrated embodiment, the pressing wall 117 is formed of a bottom 103 formed in a flat surface and a slope extending along the bottom 103 toward the positioning pin 112.
As described above, by the thrust wall 117, a component of the thrust force applied to the movable unit 100 by the heat-generating fluid flowing through the protective sheath 200 is used to cancel the gravity of the movable unit 100. This thrust acts on a plane located on the transverse projection of the thrust wall and serves to balance the pressure difference between the upper and lower ends of the first support section 110.
The positioning pins 112 serve to define a portion of the space between the movable unit 100 and the protective cover 200. In the illustrated embodiment, the first support section 110 is cylindrical. The locating pin is a unitary member, typically made of the following materials or alloys thereof: such as EM10 ferritic-martensitic stainless steel. Other steel materials or metals, such as refractory metals, etc., may be used in practice, and the choice of material is determined by the actual operating conditions of the actual reactor.
Preferably, the locating pin 112 is mass-produced to more precisely control the size of the locating pin, and this production method is also advantageous for the definition of the section S1.
In one embodiment, the locating pin is a solid piece.
According to a further advantageous embodiment, the positioning pin is hollow and thus lighter in weight. The locating pin may be manufactured by machining or other methods. In order to avoid the generation of a recess on the edge of the top of the positioning pin, a plug is additionally arranged at the bottom of the positioning pin.
Preferably, in the embodiment shown in fig. 1-9 and 11, the first support section 110 is positioned vertically below the neutron-absorption section 130. Thus, in the supported state, the positioning pin 112 is located below the core. The first support section 110 is located at an upper portion of the neutron-absorption section 130 when the coolant 5 flows within the protective sheath 200.
In an alternative embodiment, the first support section 110 is positioned vertically above the neutron-absorption section 130. The description of which refers specifically to fig. 10.
Embodiments in which the first support section 110 is vertically below the neutron-absorption section 130 have several advantages.
Because the first support section 110 is not in the neutron flux, the exposure of the first support section 110 is limited. However, the macroscopic appearance of the micro-damage caused by irradiation of metallic materials under neutron flow is represented by dimensional changes, in particular, dimensional expansion with increasing irradiation dose. Thus, compared to the solution where the first support section is arranged in the neutron flow, this solution does not affect the geometry of the first support section and ensures its functionality, which makes the security device more reliable.
Referring to FIG. 11, a scheme for achieving lift by determining the force generated by the coolant is detailed herein.
Fig. 11 shows a second support section 210 formed by a sleeve 211, the positioning pins 112 delimiting the first support section 110 of the mobile unit 100 with its longitudinal wall facing the longitudinal wall of the sleeve 211 and its thrust wall 117 subjected to the lifting force generated by the coolant. In this figure, the diameter D112 of the locating pin and the diameter D211 of the internal passage formed by the bushing are shown, and the gap j1 between these two diameters is also shown. The flow direction of the coolant 5 and the pressure P1 at the upper end and the pressure P2 at the lower end of the jacket 211 are also shown in the figure. During lifting, L211 represents the longitudinal length. In this direction, the first support section 110, which is defined by the sleeve 211, faces the second support section 210.
The lift force resulting from the pressure drop between the hydraulic cooperation area and the portion of the dowel pin having a diameter D112 is based on the following parameters: length L112-211Diameter D211Radial gap j1= D211-D112. In addition, in fact, when the positioning mechanism of the movable unit 100 is separated from the grasping apparatus 300, the movable unit 100 moves by a distance L in the process112-211. This facilitates the lifting of the movable unit, makes the reaction better and makes the device reliable and stable.
After separation, the load bearing zone inevitably supports the fall of the mobile unit, even at flow rate QfIs still higher than the trigger value QTriggering. The presence of separation is caused by instability of the system, caused by geometric/mechanical (misalignment of the movable unit within the protective sheath), hydraulic (e.g. hydraulic disturbances, vibrations) or other causes (e.g. presence of impurities in the gap between pin and sleeve).
According to rated flow QNAnd a trigger threshold QTriggeringDuring the falling of the movable unit 100, those skilled in the art know that the dimensions of the first and second support sections 110 and 210, particularly their cross-sections and lengths, remain unchanged.
In particular, F acting on the mobile unitThrust forceCan make the unit active at QfGreater than QTriggeringIs lifted and the first support section 110 and the second support section 210 face each other. The thrust is as follows:
Fthrust force = FPressure of+ FFrictional force
Wherein:
-F frictional force Representing the viscous drag of the hydraulic cooperating area. In the embodiment shown in FIG. 11, the friction force is primarily takenDepending on the length L211The viscosity of the cooling liquid and the interval j1, wherein j1= D211-D112.
-F Pressure of Representing the pressure exerted by the cooling liquid on the projection surface (generally from the positioning pins 112 of the thrust wall 117) and the pressure P exerted by the cooling liquid on the projection surface1. In the embodiment shown in FIG. 11, the amount of pressure exerted on the projection surface depends primarily on the diameter D112And pressure P1。
Thus, FThrust forceAt least the mass of the absorber rod is cancelled, i.e. the buoyancy is subtracted from the thrust.
According to one embodiment, the first support section 110 is located longitudinally below the neutron-absorption section 130 and at a distance from the neutron-absorption section to form the separation section 120. The length of the isolation section is equal to the stroke of the movable unit during lifting and falling. This ensures that the first support section 110 is not located in the core. Wherever the first support section 110 is located, there are advantages as described above. Furthermore, when the first support section 110 is in the neutron flux, the radiation exposure of the first support section 110 can be reduced.
The separation section 120 may be implemented according to various embodiments. As shown in the embodiments of fig. 1-9 and 11, the separation section includes a tie rod 122 and a reinforcement member 121 to ensure mechanical connection between the neutron-absorption section 130 and the first support section 110. Preferably, as shown in fig. 4b, the separating section 120 includes three reinforcing members 121, the reinforcing members 121 extending radially from the center of the movable unit 100 and longitudinally from the middle absorbent section 130 to the first support section 110. The structure has the following advantages: mechanical guidance in the whole stroke is realized; the mechanical strength is improved; the weight is reduced, which is very important for the support; the pressure loss is small; there is no complex hydraulic design.
Fig. 8 and 9 illustrate an embodiment of the divider segment 120. The separation section 120 includes a perforated tube 123. Perforated tube 123 has longitudinally extending openings 124. These openings 124 are distributed throughout the profile of the perforated tube 123 and the longitudinal dimension of the separator section 120, and thus, a coolant can pass through these openings 124 to reduce the energy consumption of the neutron-absorption section 130 and cool it.
According to an embodiment, the perforated pipe 123 has the same advantages as the tie rod and its reinforcement. However, perforated pipes require more advanced hydraulic and mechanical techniques.
The grasping of the movable unit 100 in the operating position becomes simple and feasible by the absorption bar mechanism including the grasping means 300. The gripping means are intended to grip the head 101 of the mobile unit. In the following, in order to ensure that the process of falling the mobile unit 100 is achieved by passive triggering, the mechanism is only used for gripping.
The operation of the passive trigger type safety device according to the present invention will now be described with reference to fig. 7.
In the lowered position shown in fig. 7a, the hydraulic cooperation zone between the mobile unit 100 and the protective sheath 200, more specifically between the respective support sections 110, 210, is not activated.
Before the reaction occurs, the movable unit 100 is prepared for falling by the absorption bar mechanism including the grasping means 300. That is, when the reactor is activated, the movable unit 100 is ready for a fall. The absorption section 130 of the active unit 100 is located in the core. The gripping means grips the top 101 of the mobile unit (as shown in figure 7 b) to lift the mobile unit 100 upright. The lifting process is shown in fig. 7 c.
In the above step, the coolant flow rate QfIn line with the reactor treat rate values and below the release rates mentioned below.
Subsequently, the coolant flow rate Q is set by the suction rod mechanism when the movable unit is suspendedfIncrease, (as shown in fig. 7 d).
QfIs at least equal to QTriggering≤QReleasingPreferably, when QTriggering<QReleasingIt is safer when the grasping means 300 is opened and the sucker mechanism releases the movable unit 100 as shown in fig. 7E, in which QReleasing<QN。
Preferably, the mobile unit 100 has a first support section 110 and a second support section 110 located inside the protective sheath 200 when it is pulled by the gripping device 300A support section 210. QReleasingThe generated force is used to lift the movable unit 100.
Provided that Q isTriggering<Qf，QfMay continue to increase to its nominal value to ensure the fall of the mobile unit 100, as shown in fig. 7E.
However, if Qf <QTriggering，QfThe resulting force cannot lift the mobile unit 100 and the mobile unit falls under gravity (as shown in fig. 7 f) to its end of travel position, as shown in fig. 7 g.
Thus, when the value of the unprotected transient flow in the primary circuit suddenly decreases below the flow allocated to the component, the hydraulic cooperation is stopped, so that the active units 100 and the absorbent material 130, which descend in a passive triggered manner, are inserted into the core 10 under the action of gravity.
Referring to fig. 10a, 10b, 10c, in an alternative embodiment, the first support section 110 is positioned vertically above the neutron-absorption section 130. Thus, the first support section 110 is vertically above the core region 240 of the protective sheath 200, and thus above the reactor core 10. Specifically, the first support section 110 is located between the top 101 and the middle absorbent section 130 of the mobile unit 100.
According to one embodiment, the first support section 110 is formed by a protrusion 115 on the tie rod 102. The protrusion 115 extends between the top 101 and the neutron absorbing section 130 of the activity unit 100. Thus, the projection 115 is located between the ends of the pull rod 102. As shown in fig. 10a, the projections 115 of the first support section 110 are held at a distance from the neutron-absorption section 130 by the separation section 120. The protrusion 115 has a lower end to form a thrust wall 117 for the coolant, enabling the lifting of the movable unit 100.
Preferably, the boss 115 is hollow and provided with a plurality of coolant discharge holes 116, 118. Of these holes, an upper coolant discharge hole 118 is located at the upper end of the boss 115, and at least one lower coolant discharge hole 116 is located at the lower end of the boss 115. The projection 115 has a cylindrical wall that is longitudinally extending, while the second support section 210 is a sleeve 211 formed by the protective sheath 200; the space between the outer surface of the cylindrical wall of the projection 115 and the inner surface of the sleeve 211 is referred to as a section S1 for the coolant to flow through.
Preferably, the safety device includes a damper of the movable unit 100 for a falling process of the movable unit.
The damper includes a first damping member 140 supported by the movable unit 100 and disposed to be in contact with the coolant, and a second damping member 220 supported by the protective sheath 200 and disposed to be in contact with the coolant.
The first and second damping members 140 and 220 are formed such that the first damping member 140 enters the second damping member 220 before the movable unit 100 falls and reaches the stroke end position in the falling arrangement state, and then the first and second damping members 140 and 220 cooperate with each other to form a viscous damper.
Preferably, the second damping member 220 forms a movable unit 100 limiting member. Therefore, the movable unit 100 is prevented from colliding with the bottom wall 206 at the lower end of the protective sheath 200.
According to the embodiment shown in fig. 1-6, 8-9, the first damping member 140 of the apparatus is disposed longitudinally between the bottom 103 of the mobile unit 100 and the neutron-absorption section 130, specifically at the lower end of the neutron-absorption section 130. In another embodiment, the second damping member 220 forms a concave portion and has at least one chamber 225, the chamber 225 having a cross-section in the shape of a ring centered on the axis of translation of the mobile unit and extending longitudinally from an opening 226 at the upper end of the chamber 225 to the bottom 227 of the chamber 225.
The first damping member 140 forms an insert for insertion into the chamber 225 before the mobile unit 100 reaches its end-of-travel position.
The first damping member 140 forms a small tube with a free end 141 shaped to facilitate its entry into the chamber. The other end of the tube is mechanically connected to the mobile unit 100, as shown in fig. 6b and 6 c. Preferably, the end is adjacent to the lower end of the neutron-absorption section 130.
The cavity 225 is disposed substantially on a central axis of the mobile unit 100, and the insertion dimension corresponds to the dimension of the cavity 225, so that during insertion, the coolant within the cavity 225 is expelled, creating a viscous force for resisting insertion of the insert. In particular, the chamber 225 and the dimensioning of the insert are established to ensure that a sufficient viscous damping force can be generated, preventing the mobile unit 100 from falling before its end-of-travel position.
Preferably, the chamber 225 is formed within the thickness of the sleeve 211. Preferably, the second support section 210 is also formed by a sleeve 211.
Thus, the sleeve 211 has two walls, each providing a very specific function:
when the flow is sufficient, the sleeve 211 cooperates in one of its walls with the mobile unit to achieve its supply;
when the flow rate is abnormally reduced, the other wall of the sleeve 211 ensures a damping force, preventing the drop of the mobile unit 100 before its end-of-travel position.
Preferably, the second damping member 220 is used for providing viscous damping, the second support section 210 has a lifting function, and the second damping member and the second support section are at least partially disposed opposite to each other in the longitudinal direction, i.e., in a horizontal position, they are at the same height. Such an arrangement is highly advantageous for achieving dimensional control. As can be seen from fig. 4c and 5b, the lifting action of the movable unit 100 is completed between the chamber 225 and the space j 1. In this embodiment, the number of critical parts that need to be finely machined is reduced. Furthermore, space is saved significantly.
In this embodiment, the damping and lifting function provided by the sleeve 211 has the following advantages:
for existing damping elements, there is no need to modify the length and stroke of the mobile unit when operating at a height that is higher than the height required for the damping function, and therefore, there is no effect on the assembly height;
furthermore, there is no need to design a damping zone, since the function of the damping zone actually reduces the effective damping, which corresponds to a guide zone. Therefore, in this embodiment, there is no need to create a new guide area, which will facilitate the plug-in reliability of the movable unit in the damper (and thus the speed of the fall) when facing the risk of jamming, chattering, etc. These risks of jamming, chatter, etc. are generally caused by structural deformations of the device under irradiation, such as deflections/deflections. According to the present embodiment, this solution improves the reliability of the insertion of the damper movable portion into the sleeve portion, such insertion being performed in the guide area constituted by the sleeve 211.
According to an embodiment not shown, the damping function may also be provided by the cooperation between pin 112 and protective sleeve 200, preferably by bottom wall 206.
Thus, the first support section 110 and the first damping member 140 are defined by the outer surface 113 of the pin 112 of the mobile unit 100. Thus, in this embodiment, the lifting and damping functions are provided by the same component carried by the mobile unit 100, which may be the locating pin 112. Bottom wall 206 is preferably secured to the interior of the sleeve, such as to bottom 204.
As shown in the preferred embodiments of fig. 1 to 6 and 8 to 10, the safety device includes: at least one guiding section for guiding the displacement of the mobile unit 100 in the protective sheath 200. As shown in fig. 3b, the guide section includes at least one guide section consisting of at least two, preferably three, spacers 231, the spacers 231 being symmetrically distributed about the movement axis of the movable unit 100. The spacers 231 in fig. 3b are arranged at intervals of 120 ° from each other, respectively. Preferably, the guide section is formed by a pad bearing ring defining a pad 231 on its inner side.
The guide section is longitudinally arranged in the protective sheath 200 so as to reach the neutron-absorption section 130 when the movable unit 100 is in the lifted state. Thus, the cooperation between the outer side of the neutron absorbing section 130 and the pad 231 ensures accurate and reliable displacement guidance of the mobile unit 100 in the protective sheath 200.
However, the above embodiments are not limitative.
In view of the above description, it is evident that the present invention provides a particularly reliable and safe solution, allowing the absorber rods to fall completely in a passive manner when the coolant flow is abnormally reduced.
The invention is not limited to the embodiments described above but extends to all embodiments encompassed by the claims.
Reference numerals
1. Device 3, longitudinal direction 5, coolant 10, core
100. Movable unit 101, top 102, pull rod 103, bottom
104. Absorption rod 110, first supporting section 112, positioning pin
113. Outer surface 115, raised structure 116, drain hole
117. Thrust wall 118, head space 120, partition
121. Reinforcing member 122, pull rod 123, perforated pipe
124. Opening 130 neutron absorbing section 131 absorbing needle
132. Connecting member 133, coolant passage 140, first damping member
141. 200-end protective sleeve 201 hexagonal pipe
202. Top 203, outlet 204, mounting feet
205. Power indicator 206, wall 210, second support section
211. Sleeve 212, inner wall 220, second damping member
225. Chamber 226, opening 227, chamber bottom
231. Spacer 240 core area 300 fastener

Claims (38)

1. A passive triggered safety device (1) for a nuclear reactor comprising a core inside of which at least part of the heat is carried out of the core by a coolant, the device comprising an assembly comprising:
a protective sheath (200) extending approximately perpendicularly along a longitudinal direction (3) for longitudinal passage of a coolant;
-an active unit (100) capable of translating in a longitudinal direction (3) rising into the protective sheath (200) and comprising at least a neutron-absorption section (130) comprising at least a neutron-absorption material, said neutron-absorption section extending in the longitudinal direction (3) and being configured to be longitudinally passable by a coolant;
characterized in that said mobile unit (100) comprises a first support section (110) and said protective sheath (200) comprises a second support section (210); the first and second support sections (110, 210) are formed such that:
if the first and second support sections (110, 210) are arranged in an opposing manner and in a transverse direction perpendicular to the longitudinal direction (3), the first and second support sections (110, 210) together define a coolant flow space, the space being given the S1 section:
-coolant flow Q when flowing longitudinally through the protective sheath (200)fThe coolant flow rate Q is less than that of the action of triggering the absorption rod to fall to the coreTriggeringWhen the coolant applies a force to the movable unit (100) sufficient to support the movable unit (100) in the protective sheath (200) and maintain the movable unit (100) in a vertical state in the force configuration condition;
when flow rate Qf<QTriggeringWhen the force applied by the coolant to the movable unit (100) is not enough to support the movable unit (100) in the protective sleeve (200) and not enough to maintain the vertical state of the movable unit (100) under the force configuration condition, the movable unit (100) will descend along the gravity of the protective sleeve until the stroke end position, namely the absorbing rod falling configuration state, is reached;
if the first and second support sections (110, 210) are not disposed in the lateral direction, the first support section (110) and an inner surface (212) of the protective casing (200) facing the first support section (110) together define a coolant flow space, segment S2, segment S2>At stage S1, i.e. flow rate Qf>QTriggeringThe force exerted by the coolant on the mobile unit (100) is also insufficient to cause the mobile unit (100) to translate back into the protective sheath (200).
2. The device (1) according to claim 1, wherein the first support section (110) is supported by an outer surface of the mobile unit (100).
3. Device (1) according to claim 1, wherein the protective sheath (200) comprises at least a sleeve (211), while the second support section (210) is formed by the sleeve (211).
4. The apparatus (1) of claim 1, wherein the first support section (110) is located vertically below the neutron-absorption section (130).
5. The device (1) according to claim 1, wherein the second support section (210) is located vertically below a core region (240) of the protective sheath (200) which faces the core (10) active zone of the reactor.
6. The device (1) according to any one of claims 4 to 5, wherein the first support section (110) is arranged longitudinally with a separation section (120) between it and the neutron absorption section (130); the longitudinal length of the partition is at least equal to the longitudinal travel of the mobile unit between the supporting configuration and the falling configuration.
7. Device (1) according to any one of claims 4 to 5, wherein the mobile unit comprises a positioning pin (112) supporting the first support section (110).
8. The device (1) according to claim 7, wherein said positioning pin (112) is located at the bottom (103) of said mobile unit (100) and the lower end of said positioning pin (112) contributes to form a coolant thrust wall (117) to ensure the support of said mobile unit (100).
9. The device (1) according to claim 7, wherein said positioning pin (112) is a cylindrical monolithic member, generally made of one of the following materials or alloys thereof: ferritic-martensitic stainless steel, EM10 ferritic-martensitic stainless steel, refractory metals.
10. Device (1) according to claim 7, wherein said second bearing section (210) is a sleeve (211) supported or formed by the inner surface of said protective sheath (200); the distance between the inner surface of the sleeve (211) and the supporting wall of the positioning pin (112) is defined as segment S1.
11. The device (1) according to claim 7, wherein said positioning pin (112) is hollow and defines a closed internal volume.
12. The device (1) according to claim 1, wherein said first support section (110) is arranged longitudinally with a separation section (120) between it and said neutron-absorption section (130), said separation section (120) comprising at least a tie rod (122) and a reinforcement (121) to ensure a mechanical connection between said neutron-absorption section (130) and said first support section (110).
13. The device (1) according to claim 12, wherein said separating section (120) comprises at least three stiffeners (121), these stiffeners (121) extending radially starting from the center of said mobile unit (100); and extends longitudinally from the neutron-absorption section (130) to the first support section (110).
14. The apparatus (1) of claim 1, wherein the first support section (110) is longitudinally disposed with a separation section (120) therebetween from the neutron-absorption section (130); the separation section (120) comprises at least a perforated tube (123) to ensure a mechanical connection between the neutron-absorption section (130) and the first support section (110).
15. Device (1) according to claim 14, wherein the perforated tube comprises a plurality of longitudinally extending openings (124), the openings (124) being distributed over the entire outer shape of the perforated tube (123) and over the entire longitudinal dimension of the separating section (120).
16. The apparatus (1) of claim 1, wherein the first support section (110) is located vertically above the neutron-absorption section (130).
17. The device (1) according to claim 1, wherein in the support configuration the first support section (110) is vertically above a core area (240) of the protective casing (200).
18. The device (1) according to any one of claims 16-17, wherein the first support section (110) extends longitudinally between a top (101) constituting an upper end of the mobile unit (100) and the neutron-absorption section (130).
19. The device (1) according to any one of claims 16-17, wherein the mobile unit comprises a tie rod (102) extending at least from an upper end of the mobile unit (100) to the neutron-absorption section (130), the first support section (110) being a protruding structure (115) supported by the tie rod (102) between the upper end of the mobile unit (100) and the neutron-absorption section (130).
20. Device (1) according to claim 19, wherein the lower end of said protruding structure (115) contributes to form a coolant thrust wall (117) to ensure the support of said mobile unit (100).
21. Device (1) according to claim 19, wherein said protruding structure (115) is hollow, provided with a plurality of coolant discharge holes (116, 118).
22. The device (1) according to claim 19, wherein the raised structure (115) is a longitudinally extending cylindrical wall and the second bearing section (210) is a sleeve (211) supported or formed by an inner surface of the protective sheath (200); the space j1 between the outer surface of the cylindrical wall of the boss structure (115) and the inner surface of the sleeve (211) is defined as segment S1.
23. The device (1) according to claim 1, further comprising a damper of the mobile unit (100) for the falling process of said mobile unit; the damper includes:
-a first damping member (140) supported by the mobile unit (100) and arranged in contact with the coolant;
-a second damping member (220) supported by the protective sheath (200) and arranged in contact with the coolant;
the first and second damping members are configured such that the first damping member (140) enters the second damping member (220) before the movable unit (100) falls and before it reaches an end-of-travel position in a falling configuration state, and then the first and second damping members (140, 220) cooperate with each other to form a viscous damper.
24. The device (1) according to claim 23, wherein the first support section (110) and the first damping member (140) or the second support section (210) and the second damping member (220) are supported by the same member (112, 211).
25. Device (1) according to claim 24, wherein the second support section (210) and the second damping member (220) are at least partially positioned longitudinally at the same height.
26. Device (1) according to claim 23, wherein said second bearing section (210) and said second damper (220) are supported by the same member (112, 211); the protective sheath (200) comprises at least a sleeve (211), the components inside the protective sheath (200) being formed by the sleeve (211).
27. Device (1) according to claim 26, said sleeve (211) comprising a chamber (225) filled with a coolant, said chamber (225) forming said second damping member (220); the first damper (140) forms an insert to insert the chamber (225) and drive the coolant before the movable unit (100) reaches its end-of-travel position.
28. The apparatus (1) according to claim 27, wherein the first damping member (140) is longitudinally disposed between the active unit (100) bottom (103) and the neutron absorbing section (130).
29. Device (1) according to claim 27, wherein said first damping member (140) is longitudinally arranged between said mobile unit (100) bottom (103) and said mobile unit top (101).
30. A device (1) according to claim 28 or 29, wherein the second damping member (220) forms a sleeve portion comprising a chamber (225); said first damping member (140) forming an insert (145) accessible to said chamber (225); said chamber (225) is circular, having transverse annular openings (226) through which said inserts (145) are to be inserted into said chamber (225) before the mobile unit (100) reaches the end-of-travel position in its lowered configuration; the insert (145) forms a small tube, the free end of which is formed to facilitate its passage into the chamber (225) through the opening (226).
31. Device (1) according to claim 28 or 29, wherein said second damping member (220) is formed by a sleeve (211) supported by the inner surface of said protective sheath (200); the second support section (210) is formed by an inner surface (212) of the sleeve (211).
32. The device (1) according to claim 31, wherein said chamber (225) is formed within the thickness of said sleeve (211), said chamber having a bottom (227); the second support section (210) is formed by an inner surface of the sleeve (211), at least partially arranged longitudinally, facing the chamber (225).
33. Device (1) according to claim 1, wherein said protective sheath (200) comprises at least a guiding segment guiding the translation of said mobile unit.
34. Device (1) according to claim 33, wherein said guiding section comprises a plurality of pads (231) radially and regularly distributed around the axis of translation of said mobile unit (100).
35. The device (1) according to claim 34, wherein said guiding section comprises three pads (231).
36. Passive shutdown system for a nuclear reactor, comprising a passive trigger-type safety device (1) according to any one of claims 1 to 35 and a mounting mechanism comprising a gripping device (300) for a mobile unit (100).
37. Nuclear reactor comprising a core (10) and a primary circuit, said nuclear reactor comprising at least a passive triggering safety device according to any one of claims 1 to 35.
38. The nuclear reactor of claim 37 which is a fast neutron reactor.
CN201611047649.4A 2015-11-23 2016-11-23 Passive triggering safety device for nuclear reactors during abnormal coolant reduction Active CN107068213B (en)

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FR1561275A FR3044155B1 (en) 2015-11-23 2015-11-23 PASSIVE TRIP SECURITY DEVICE FOR NUCLEAR REACTOR ON ABNORMAL PRIMARY RATE DROP

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JP6948781B2 (en) 2021-10-13
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