Classifications

• • 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
  • 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
• • 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
  • G21C7/107—Control elements adapted for pebble-bed reactors
• • 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

Definitions

• the present invention relates to a method and control system for regulating and selectively shutting down the power of a nuclear reactor, to a nuclear reactor including such a system, and to a neutron absorption body for such regulating and selectively shutting down the power of a nuclear reactor.
• Today's nuclear fission reactors include a reactor core that contains the nuclear fuel elements.
• the nuclear fuel elements include the nuclear fuel (uranium, thorium and / or plutonium isotopes) and a moderator.
• Nuclear fission releases fast neutrons which are slowed down by the moderator in order to achieve an energy level that is suitable for causing another fuel core to fission. This in turn leads to the release of fast neutrons and heat, which is used to generate energy.
• At least two independent shutdown systems for nuclear reactors. They serve to end the nuclear chain reaction. At least one of these systems can also be used to regulate the operation, ie the power and the power profile of the reactor.
• the shutdown systems traditionally work by bring neutron absorbing materials into the core or its surroundings (e.g. the surrounding reflector). The amount of such absorbers to be introduced must be sufficient to ensure a sufficiently rapid control and, if necessary, a sufficient switch-off effect, for example in all operating and fault situations in the event of a temperature change and / or after a decay of Xe 135 .
• a shutdown system is also used for control purposes, these absorbers are not moved completely out of their effective positions during normal operation, so that the reactivity can be increased when extended further, i.e. the splitting rate can be increased.
• a switch-off function is achieved by moving additional absorbers into effective positions, which stops the chain reaction.
• HTR high-temperature reactor
• AVR working group experimental reactor located in Julich, Germany, which had a thermal output of 46 MW, was designed for a helium outlet temperature of 850 ° C, but was experimentally driven up to 1000 ° C
• THTR Thorium high-temperature reactor; heat output 750 MW located in Uentrop, Germany
• MODUL-HTR a developed in Germany modular globular reactor concept with a thermal output of 200 MW
• a characteristic of the pebble bed reactor is that new spherical fuel elements are introduced into its core during operation and, if necessary, old ones can be withdrawn from it.
• Rods are usually used in the shutdown and control systems in which the absorbent material is enclosed in metallic tubes. If the ball cluster core is designed accordingly, it is sufficient to insert such a rod into the rod openings provided for this purpose in the side reflectors. In addition, it is only possible for shutdown purposes to enclose the absorber in small balls instead of rods, as was the case with the second shutdown system of the MODUL-HTR concept. Such balls have become known as "small absorber balls" (KLAKs). These KLAKs consist of graphite balls that contain boron or boron carbide. The KLAKs are introduced into vertical so-called KLAK openings or bores.
• KLAKs are less sensitive to temperature than metallic rods. 2.although rods can be introduced from below as well as from above and, in the case of a short rod, m different positions can be introduced, KLAKs collect by gravitation at the lower end of each KLAK channel and have to be filled in by gravitation to reach higher levels or from there subtracted below to reduce absorption levels.
• absorber materials have so far been used primarily in the form of the aforementioned rod in order to influence the performance profile and in particular the heat output profile in the desired manner in a controlled manner, usually in order to smooth such a profile.
• the concentration of spent fuel increases downwards. Accordingly, the maximum power is usually in the upper half of the core. The course of this maximum power m in the upper half and thus also the resulting profile or the production of fast neutrons can be smoothed if the part of the absorber body of the control system that is used for power control under normal operating conditions near this position has maximum effect the top half.
• the conventional control rods were each in the form of a rod, around which annular control bodies made of neutron-absorbing material such as boron carbide, hafnium carbide or the like were arranged.
• annular control bodies made of neutron-absorbing material such as boron carbide, hafnium carbide or the like were arranged.
• boron carbide is stable at temperatures up to at least 1600 ° C
• the metal of the inner rod loses its required tensile strength at temperatures above 650 ° C. This causes problems because, for very good reasons, it was customary to arrange this metal rod in a hanging manner in order to be able to lower it by gravitation in the core area and thus to slow down the chain reaction by increasing the neutron absorption and optionally to stop it entirely.
• the neutron flow is highest in the upper areas of the reactor core because fresh fuel balls are conventionally introduced into the reactor from above, while all or part of the spent or spent fuel balls are withdrawn from the lower area. Accordingly, the level of the neutron flux in the reactor core decreases from top to bottom. Hence it is suggests that a control system is advantageous that primarily reaches the core area from above.
• temperatures of around 900 ° C have become the norm during normal operation, and in the event of malfunctions, the temperatures of the absorber bodies can rise to over 1200 ° C, which far exceeds the tolerance limits of the metal rod.
• the present invention provides a nuclear reactor which includes a system or systems of regulators for power and cut-off control based on neutron absorption with the aid of movable neutron absorber bodies, the regulator system (s) being a duct system with a duct or an arrangement of bores, which are loaded or can be loaded with a sequence of gravity-absorbing absorber bodies to adjustable levels, the absorber bodies having cross-sectional dimensions which essentially correspond to the cross-sectional dimensions of the bores in sliding relation with sufficient play for easy sliding, and the absorber bodies downwards a be supported by at least one level-determining support.
• the regulator system being a duct system with a duct or an arrangement of bores, which are loaded or can be loaded with a sequence of gravity-absorbing absorber bodies to adjustable levels
• the absorber bodies having cross-sectional dimensions which essentially correspond to the cross-sectional dimensions of the bores in sliding relation with sufficient play for easy sliding, and the absorber bodies downwards a be supported by at least one level-determining support.
• each channel preferably contains a multiplicity of said flowers.
• the bladder bodies can absorb different neutrons, more precisely in such a way that they can
• one or more of the bodies may have neutron reflecting properties, for example by enclosing or facing a neutron reflecting material.
• a plundering member serves as a support that determines the level.
• the plunger member includes a piston or is piston-shaped.
• the distance that the blmd cores travel between the neutron absorber bodies and the plunger member or another level-determining support is preferably such that the piston is in all of its operating positions below the lowest level of the reactor core, ie in an area where the radiation, especially the neutron flux, is minimal or non-existent.
• the piston is preferably loaded by suitable operating means outside the pressure vessel of the reactor. does (ie raised or lowered).
• Such operating means can be mechanical, pneumatic, hydraulic or electromagnetic or a combination of two or more of these options.
• the piston or plunger member can be made of a suitable material such as graphite, ceramic, e.g. Aluminum oxide or beryllium oxide, or a suitable metal such as furnace steel.
• the fact that the absorber bodies move under the force of gravity until they are stopped by the plunger member or other level-determining support can be used to protect the absorber bodies in the event of a malfunction of the reactor due to, for example, a power failure by automatically releasing the normally on the plunger member or another holding force applied to the level-determining support automatically to its switch-off positions (ie where maximum neutron flux is present). This can be done in a conventional manner by automatically releasing a level-retaining force in its raised position, for example by releasing an electromagnetic clutch or holding device.
• the dummy bodies can be made of a non-absorbing or weakly neutron absorbing material with mechanical, thermal or other properties suitable for the purpose.
• the materials used could be the same or similar to those described above for the piston or plunger, but are preferably not metallic. Both the absorber body and the dummy body are to be shaped and dimensioned so that they slide freely without getting stuck in the holes.
• the shape of the absorber bodies and dummy bodies can vary from spherical to ellipsoidal or barrel-shaped to cylindrical with chamfered or rounded edges.
• elongated bodies of the latter shapes are preferably introduced lengthways into their respective bores.
• the radii of curvature of any bends or curvatures in the bores limit the axial length of the body, which in practice can vary, for example, from 1 to 5 times, preferably from 1 to 3 times, better still from one to two times the channel diameter.
• Such deviations from the straightness of a channel can advantageously be used to determine the proximity of the neutron absorber body to the reactor core and thereby the Vary the neutron absorbing effect of the neutron absorber bodies on different core levels.
• An arrangement of holes can be used, whereby different holes can have different curvatures in relation to the core.
• Some bores can also be straight, that is to say a constant distance from the reactor core, while some other bores can be curved in order to increasingly guide the absorber bodies at different levels of the reactor core to or from it. This principle is similar to that of our copending application 98/0128.
• the holes can have a uniform round cross-section over their entire length.
• such a channel with an elongated cross section can receive a gradual axial twist up to one area with normally reduced core activity, the direction of the cross-sectional elongation points radially to the core axis.
• the invention it is possible to use the invention to maximize the neutron flux exposure of the absorber and / or body in areas of high core activity by using holes for these bodies in these areas, some of which are to the core area hm are open.
• partially open we mean the presence of open areas in the form of a slot or a series of slots or openings which are aligned parallel to the reactor core axis and are dimensioned in such a way that the absorber and / or bubble bodies are held in the channel, and in particular also dimensioned so that the fuel balls cannot get into the channel in the case of a pebble bed reactor.
• the operating or drive means for the plunger member is preferably outside the pressure vessel of the reactor. Accordingly, maintenance work on this agent can be done without difficulty be performed.
• the operating or drive means can be connected to the plunger member via a connecting rod or the like, only a small passage through the wall of the pressure vessel including suitable sealing means being necessary. It is obvious not to exclude operating or drive means within the pressure vessel from the scope of the invention.
• the invention is preferably applied to reactors of the high temperature reactor (HTR) type and in particular to reactors which are designed by introducing fresh nuclear fuel with or without recirculated partially burned fuel at one end and withdrawing spent fuel with or without partially burned fuel to be operated at an opposite end, and in which the absorber bodies are held in an arrangement which is suitable for effecting maximum neutron absorption in a region immediately at or near a part of the reactor core where the fuel passing through the reactor maximum or achieves nearly maximum performance, and cause decreasing or zero neutron absorption in areas immediately at or near parts of the reactor core where fuel activity is already reduced.
• a preferred embodiment is the spherical fuel bulk or spherical pile type.
• the level (m relation to the reactor core) at which a change from the maximum absorption effect to a less absorbing or zero absorption effect should take place depends on depending on how fuel is supplied to the reactor.
• the arrangement is intended to provide maximum or near maximum absorption in an area immediately at or near the top half of the reactor core and reduced or zero absorption in an area where the performance of the non-poisoned core is approximately one-half to one-third of that Area with maximum power. More specifically, the area with reduced or zero absorption effect begins at a level not less than 1/10 of the total core height above the bottom reflector area of the reactor.
• the range of maximum core performance is usually between 50% and 70% of the total core height, and the portion of the assembly with maximum absorption effect does not extend down to a level 30% of the total core height above the bottom reflector area of the reactor.
• the range of maximum power of the core is at a level between 66% and 75% of the total core height
• the range of arrangement with maximum absorption effect not down to a level 40% of the total core height extends over the bottom reflector area of the reactor. More specifically, the area of the arrangement with the maximum absorption effect extends down to a level not below 50% of the total reactor height above the bottom reflector area of the reactor.
• the invention is of particular use when the energy output is used directly for the operation of helium turbines or turbines with other gaseous media, in which high starting temperatures are required.
• a method for regulating the power of a nuclear reactor by absorbing neutrons with the aid of neutron-absorbing bodies which includes the following steps:
• Bores comprise, with a consequence of gravity, neutron absorber bodies located in a slant with cross-sectional dimensions corresponding to the cross-section of the channel (s) of such a channel system with sufficient play for free
• the invention further extends to a reflector for a nuclear reactor, wherein a channel system with a Channel or an arrangement of holes for receiving a column of stacked neutron absorber bodies is formed and the cross section of the channel (s) (holes) essentially the cross section of the body intended for receiving in this channel with enough play for free sliding movement of the Corresponds to the body in the channel (s).
• Reactor according to the invention are suitable. That's how she looks
• Body cross sections that are essentially the
• Cross sections correspond to the holes that they take up during use, with enough play for free sliding movement in the holes.
• These absorber bodies preferably differ significantly in their size from KLAKs, which are state of the art.
• Their lengths measured in the axial longitudinal direction of the bores are preferably in the range of 40 mm to 400 mm, better still 50 mm to 220 mm, especially
• the cross-sectional dimensions of the absorber and bubble bodies depend on whether the bores are cylindrical or elongated or have a different shape. If the bodies are spherical, the areas described above apply to the diameters, with diameters near the lower limits being preferred. If the bores are cylindrical, the bodies have a cross section corresponding to the cross section of the channel with one play.
• the shape of the body in the axial direction can be spherical, ellipsoidal or barrel-shaped to cylindrical with rounded or chamfered ends. If, for example, the specific surface areas of the body are to be enlarged for increased absorbency, suitable surface-enlarging surface configurations can be applied to the basic form described above, e.g. Wave pattern with alternating raised and lowered areas.
• the shorter dimension can be in the range from, for example, 20 mm to 100 mm, preferably 30 mm to 80 mm, for example 60 mm, and the longer dimension can be in the range from 100 to 300 mm, preferably 150 to 280 mm, e.g. 260 mm.
• the short sides can have a rounded, for example semi-cylindrical shape.
• the absorber bodies can have a non-absorbent or weakly absorbent core e.g. made of graphite or a refractory ceramic material which (at least m areas which face the reactor core in use) is coated or clad with a strongly neutron absorbing material such as boron carbide or hafnium carbide.
• a non-absorbent or weakly absorbent core e.g. made of graphite or a refractory ceramic material which (at least m areas which face the reactor core in use) is coated or clad with a strongly neutron absorbing material such as boron carbide or hafnium carbide.
• the dummy bodies as described above are also considered part of the invention and preferably have the same dimensions (or at least the same cross-sectional dimensions) as the neutron absorber bodies.
• the body can be coated or covered with a neutron reflecting material such as a special quality graphite.
• graphite stones or blocks are provided which are assembled to form a reactor reflector and in which the bores for the neutron absorber bodies with the new characteristic features as stated above can be formed, in particular bores which, as described above, are open to the reactor core are.
• the graphite stones or blocks are therefore shaped, dimensioned and designed so that they can be assembled into a reflector as described above.
• the dosage of fast neutrons hitting the inner periphery of the reflector can increase to values above 1.5 x 10 22 cm -2 (EDN).
• a side wall reflector with a continuous smooth surface can also fail before it has reached the designed life expectancy of around 30 years. This is caused by the radiation-related volume changes of the graphite, which take place in two phases. In the first phase, neutron radiation leads to an unproblematic volume contraction. During the second phase, the volume increases again, possibly exceeding the original dimensions and leading to stress loads that damage the reflector.
• the inward-facing surface of the reflector and the corresponding surfaces of the graphite stones or blocks according to the invention are preferably grooved in a manner which is known to naturally compensate for such dimensional changes that the graphite becomes more intensive after a long period of time Experience neutron radiation.
• FIGS. 2 and 3 schematically show vertical sections through parts of bores to be used in a nuclear reactor according to the invention, which can be charged with a sequence of absorber bodies falling through gravity, the sections running in the radial direction to the reactor core axis;
• Figure 4 schematically shows a three-dimensional rear sectional view of part of a reflector of a nuclear reactor according to the invention with three straight cylindrical bores vertically in the reflector behind its interface to the core;
• FIG. 5 schematically shows a three-dimensional sectional view of a part of a reflector of a nuclear reactor according to the invention, in which three twisting bores with a generally elongated cross section are aligned vertically in the reflector behind its interface to the reactor core;
• Figure 6 schematically shows a part of a reflector of a nuclear reactor according to the invention, in which three vertical bores are formed, the developments of Figure 4 are shown, each channel to the core region of the reactor h being partially open
• Figure 7 schematically shows an enlarged partial view of part of one of the holes shown in Figure 6;
• Figures 8, 9, 10 and 12 show schematic side views of neutron absorber bodies with a round cross section for use in bores with roughly corresponding round cross sections;
• Figures 11 and 13 show a section at XI - XI in Figure 10 and an end view of the body in Figure 12 at XII - XII;
• Figures 14, 15, 16 and 18 show schematic side views of neutron absorber bodies with a generally elongated cross section for use in bores with an approximately corresponding elongated cross section;
• Figures 17 and 19 show a section at XVII - XVII in Figure 16 and an end view of the body in Figure 18 at XIX - XIX;
• Figure 20 schematically shows a cross section of a dummy body with a core and a reflective graphite coating
• FIG. 21 schematically shows a transverse cross section of part of a reflector for a core reactor, the section also running through an absorber body which is accommodated in a channel formed in the reflector and through a fuel element in the reactor core;
• Figure 22 schematically shows a vertical section through a lower part (identified as XXII) of the reactor shown in Figure 1;
• Figures 23 and 24 schematically show a vertical partial section through a section of a channel with blmd bodies and absorber bodies, two separate configurations which are determined by two separate operating positions of a plunger member which acts on the body from the lower end of the channel.
• reference numeral 30 generally designates a MODUL-HTR type pebble (spherical fuel) HTR reactor modified and developed for use in accordance with the present invention.
• the reactor 30 closes a reactor core 32 em filled with poured fuel up to a conical upper level 34.
• the reference number 36 denotes a reflector made of high-purity graphite in the area of its inner surface and made of graphite of lower quality in its outer area.
• the core 32 and the reflector 36 are enclosed by a reactor vessel or pressure vessel 38 m in connection with a connecting pipe 40 for supplying cooling gas such as helium to the core 32.
• Reference numeral 42 generally designates a fuel outlet and reference numeral 44 a fuel outlet controlled by an outlet regulator 46.
• a lower region of the reflector is designated by the reference number 48.
• the reactor 30 closes a control system for regulating or switching off the reactor power, the system in turn comprising a system of bores 50.
• the bores are accommodated in different positions in the entire body of the reflector 36 and form an arrangement of bores.
• the holes are loaded to adjustable levels with a sequence of gravitationally incident neutron absorber bodies 52, 54 (and possibly blind bodies 56) whose cross-sectional dimensions correspond to those of the holes 50 and which are in sliding relationship with the holes and have enough play for easy sliding .
• the bodies 52, 54, 56 are held in the downward direction by level-determining supports in the form of plunger members 58, each of which has a piston 59 which presses into the body.
• the degree of neutron absorption achieved by the holes when charging with neutron absorber cores depends on the near or distant distance of the channel to the core at a certain level and on the width of the aspect that the channel has on the core certain level. As generally described above, there are a number of core levels that in turn delimit levels of the channel at which certain levels of control functions must be performed under certain operating conditions. The levels vary with the type of reactor operation.
• the holes are designed for maximum absorption effect, whereas near the areas of the core where there is reduced or no neutron flow, the holes are configured for reduced absorption effect.
• the arrangement of holes is intended to produce a maximum or near maximum absorption effect in an area immediately at or near the upper half (designated by reference number 60) of the reactor core. The absorption effect decreases or becomes zero at a corresponding level in the lower part of the reactor core below the area designated by reference number 60.
• the reference number 62 designates a region of the reactor core between 50% and 70% of the total core height, in which the maximum neutron flux is present and therefore maximum absorption effects are required.
• the reference numeral 64 denotes a level of 30% of the core height above the bottom reflector area 48. The area with maximum absorption effect usually extends to a level not below 30% of the core height level 6. If the reactor is operated with one-way charging (OTTO), the maximum power range of the Kernes usually from a level between 66% and 75% of the total core height (denoted by reference number 66) to a lower level somewhere above 40% (denoted by reference number 68) of the core height.
• OTTO one-way charging
• the reactor is repeatedly reloaded with fuel
• the fuel bodies e.g. fuel balls or fuel elements
• their degree of consumption is determined. In this way, they can be recycled up to twenty times before they are replaced by new fuel bodies.
• the range of maximum power of the core is generally between a level in the range of 2/3 of the reactor core height (lower end of region 66) and half the reactor height (lower end of region 60).
• Reference numeral 70 denotes a level at 1/10 of the
• the bores of the invention can have various configurations along their length.
• FIG. 3 With reference to FIG. 3, one can see a configuration of a channel 50 in which an increase in the absorption tion effect in the downward direction is brought about by a beveling of the channel downwards against the core 32.
• the channel 50 then returns to a vertical orientation.
• the curvatures 72 along the length of the oblique channel are rounded in order to facilitate the sliding of absorber and dummy bodies in the channel, and the radii of curvature of the curvatures are designed so that the bodies with respect to a long distance of the absorber and dummy bodies likely to be used in the channel can freely overcome the curvatures.
• the bores 50 shown in FIGS. 2, 3 and 4 have a round cross section for the use of absorber and dummy cores 52, 56 with a corresponding round cross section.
• bores 50 with a generally elongated cross section are formed in the body of the reflector 36. When in use, these bores receive corresponding absorber bodies 54 and dummy bodies with an elongated cross section as a rule. The bodies are slidably accommodated in the channel in the longitudinal direction in succession and abutting each other.
• the bores 50 have a gradual axial twist ranging from a configuration with the direction of cross-section elongation of the channel perpendicular to the core axis (top of the figure) to a configuration with the direction of cross-section elongation radial to the core axis (bottom of the Figure) is sufficient.
• This axial rotation has a corresponding effect on the absorption capacity achieved by the channel and its associated absorber bodies.
• the absorption capacity is higher where the elongation direction is perpendicular to the core axis (tangential to the core).
• Such a configuration is useful near parts of the core where maximum neutron flux occurs during normal operation.
• the channel has an aspect of reduced area to the core where the elongation direction of the channel is radial to the core axis.
• Such a configuration is expedient in a region of the nucleus with normally reduced neutron flux activity.
• deviations from the straightness of the channel can be superimposed on the axial twist in order to increase or change the absorption properties of the channel.
• a single longitudinal slot 74 is formed along part of the length of each channel 50.
• the slot is aligned parallel to the reactor core axis and extends rearward from the core area through the channel 50, as can be seen in particular from FIG. 7.
• Two opposite graphite stones or blocks 76 are shaped and dimensioned such that they form part of the slot 74 and the channel 50 between them.
• the slot 74 is shaped and dimensioned in such a way that absorber and / or blind bodies 52 are held in the channel, and in particular in such a way that fuel balls 78 (in the case of a pebble bed reactor) cannot get into the channel.
• the stones or blocks 76 shown in FIGS. 6, 7 and 21 form a slot which runs over the entire vertical length of the stones or blocks.
• graphite stones or blocks forming the reflector can each have a discrete slot, so that a vertical stack of the stones or blocks form a series of discrete, successively arranged slots with an opening to a specific channel 50.
• the surfaces 77 of the stones or blocks 76 facing the core are grooved in order to compensate for the dimensional changes of the graphite after prolonged intensive neutron irradiation.
• Figures 8 to 13 a spectrum of shapes of neutron absorber bodies 52 with a round cross section is shown.
• the shapes are part of a continuum of shapes ranging from spherical (Figure 8) to barrel-shaped ( Figure 9) and ellipsoidal ( Figures 10 and 11) to cylindrical with fastened or rounded edges ( Figures 12 and 13).
• the diameters of the absorber bodies 52 are selected such that they correspond to the diameters of the bores in which they are to be accommodated enough play for free sliding of the body in the holes under the influence of gravity.
• the absorber bodies 52 have a non-absorbent or weakly absorbent core, typically made of graphite or a refractory ceramic material, which is coated or clad with a shell made of highly neutron-absorbing substances such as boron carbide or hafnium carbide. In some embodiments of absorber bodies, only the parts of the bodies which face the reactor core in use are coated with such a shell.
• absorber bodies 54 with generally elongate cross sections are now shown.
• the shorter cross-sectional dimension varies from 20 mm to 100 mm, preferably 30 mm to 80 mm (eg 60 mm) and the longer dimension can range from 100 to 300 mm, preferably 150 mm to 280 mm (eg 260 mm).
• the short sides of the cross section have a rounded configuration, so that in particular in the absorber body shown in FIG. 18 axially running edges of the body correspond to the short sides of the cross section with a semi-cylindrical configuration.
• the absorber bodies 54 have a composite structure similar to that of the body 52 and comprise a weakly absorbent core and a shell made of highly neutron absorbing substances.
• neutron absorber bodies for increased absorption capacity, surface configurations increasing the surface area (eg wave patterns with alternately raised and deepened areas) are applied to the basic shapes of the body.
• the lengths of the bodies 52, 54 measured in the axial longitudinal direction (x in FIG. 12) of the bores are preferably in the range from 40 to 400 mm, better still 50 to 220 mm and most preferably from 60 to 150 mm.
• the axial length of the body in various embodiments varies from 1 to 5 times, typically 1 to 3 times and preferably 1 to 2 times the bore diameter.
• reference numeral 56 generally designates a dummy body.
• the body shown in Figure 20 has a round cross section.
• dummy bodies can be provided in any of the forms of the neutron absorber bodies 52, 54 (e.g. as shown in Figures 8 to 19).
• the dummy bodies have the same cross-sectional dimensions as the neutron absorber bodies with which they are to be used, but can differ in length from the absorber bodies.
• Each dummy body 56 comprises an inner core 80 which is covered or clad with a shell 82 made of neutron reflecting material such as high-quality special graphite.
• the body 56 has different neutrons capable of absorption and is arranged in the bores 50 such that the neutron absorption capacity of the blind bodies decreases in the downward direction.
• Figures 22 to 24 in which the operation of the plunger 58 (including the piston 59) is shown.
• the plunger member 58 acts as a level-determining support on which the neutron absorber bodies 52 and dummy bodies 56 rest.
• the distance occupied by the dummy cores 56 between the piston 59 and the neutron absorber body 52 is selected such that the plunger member 58 and the piston 59 are always below a minimum level 84 of the core reactor core, ie in an area in which the radiation, in particular the neutron flux is minimal or non-existent.
• the piston is actuated (ie raised or lowered) by a hydraulic operating means 86.
• the operating means can be mechanical, pneumatic, electromagnetic or a combination of two or more of these options.
• the operating means 86 is located outside the pressure vessel 38 of the reactor for easier maintenance.
• the operating means 86 is connected to the plunger member 58 via a connecting rod 88 (FIG. 22), the connecting rod being guided through a small opening 90 in the wall of the pressure vessel 38, which is sealed with a suitable sealant 92.
• the operating or drive means for the plunger member is located within the pressure vessel 38 of the reactor.
• the neutron absorbing bodies 52 and the dummy bodies 56 move under the force of gravity unless they are retained by the plunger member 58.
• the reactor is switched off by automatically lowering the absorber bodies 52 into their switch-off positions (for maximum absorption capacity, where maximum neutron flux prevails).
• the automatic lowering of the absorber body can take place by automatically releasing a holding force which is normally applied to the plunger member 58.
• this holding force is provided by an electromagnetic clutch or holding device 94, which is released in the event of a power failure.
• Figure 24 shows the neutron absorber bodies 52 in their switch-off positions, with the piston 59 at the lower end of the channel 50.
• the neutron absorber bodies 52 are in a control position which can be changed vertically for control purposes by raising or lowering the piston 59.
• an arrangement of bores 50 can be used in which different bores are different in relation to the core 32.
• Some holes can also be designed for operation with a batch of KLAKs or similar free-flowing absorber bodies, such as absorber balls with diameters, preferably not more than 1/6 of the smallest duct diameter.
• bores that contain both the neutron absorber bodies 52, 54 and blind bodies 56 and separate rate drilling with KLAKs are combined into a single control system for one reactor.

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• 1999
  • 1999-03-23 ZA ZA9902247A patent/ZA992247B/xx unknown
• 2000
  • 2000-03-21 CN CNB008079692A patent/CN1213438C/zh not_active Expired - Fee Related
  • 2000-03-21 EP EP00925053A patent/EP1171886A2/de not_active Withdrawn
  • 2000-03-21 WO PCT/DE2000/000899 patent/WO2000057426A2/de not_active Application Discontinuation

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