A fuel assembly of a nuclear reactor
(57) Abstract:The invention relates to fuel assemblies, mainly in fotografirowac the RBMK-type reactors. A fuel Assembly (FA) of a nuclear reactor contains a pendant with a Central bearing shaft, on which are placed coaxially, through the end sections with vzaimovyazany connected between the two end nodes of the axial coupler attached two removable cassette with rod fuel elements. The end sections of each cartridge is configured to mate simultaneously with any of the end section of the other cassettes with any of the two endpoints of the axial rod, which is attached to the appropriate form. The technical result of the invention allows remounting FA with the change in the relative axial orientation of the cassettes on the opposite, so after re-installation in the reactor in the center of the active zone are parts of the fuel rods with smaller fuel burnup, and on the periphery - with great. In the General Energoservice FA and efficient use of fissile material in the reactor is significantly increased. 2 C. p. F.-ly, 1 Il. The invention relates to fuel assemblies (FA) /P> Known FA water water reactor VVER-type containing more than two hundred fuel elements (cartridges) and many of their shared grid spacers, the top and bottom of which are removable and allow for the possibility of replacing some of the fuel rods at the other, and the length of each fuel rod in the fuel Assembly is approximately the height of the reactor core /1/.To the disadvantage of the described construction should include the fact that although the replacement of defective fuel rods in a separate FA and allows you to extend the lifetime of their operation, such fuel assemblies in the reactor as a whole is relatively small and significantly improve the efficient use of fissile materials, it does not provide. When it comes to comparison with the situation, when in operation are only molded FA.Known fuel assemblies of RBMK-type reactor containing the suspension with a Central bearing shaft, on which are placed coaxially, through the end sections with vzaimovyazany connected between the two end nodes of the axial coupler attached two removable cassettes, each of which is made in the form of a set of core fuel elements, combined spacer bars in the beam around the pipe frame, and the length is 2/.The disadvantage of this fuel assemblies taken for the prototype to the invention, is that the replacement of individual fuel rods in it is impossible, and possible replacement cartridges are defective fuel rods on cassette incomplete generation from healthy fuel rods to save fissile materials so ineffective (due to the much smaller number of fuel rods in fuel assemblies of RBMK compared with the VVER), which is almost never used.The objective of the invention is to provide a fuel Assembly, providing increased economic efficiency in the use of fissile material in the reactor.Technical result achieved when using the invention lies in the substantial increase of energy producing fuel assemblies.This technical result is achieved by the fact that the end sections of each cartridge is configured to mate with any of the end section of the other cassettes with any of the two endpoints of the axial rod, which is attached to the appropriate form. In particular, both the end section of each cartridge can be made in the form of axial protrusions pipe frame beyond the ends of the fuel elements.The essence of this proposal is to ensure after reaching a certain saving is mean and burnout (Energoservice) fissile materials along the length of the fuel rods in the fuel assemblies of the current reactor, is distributed approximately sinusoidal with a maximum in the center area of the active zone and at least in the regions of the periphery (near the upper and lower reflectors). Therefore, the permutation of each cartridge in place of the other without changing the axial orientation relative to, for example, suspension or variation of the axial orientation of each cartridge with regard to the suspension in its original position in height leads to the fact that both cassettes FA are mutually reoriented relative to the junction of cassettes each other and after installation of such fuel assemblies in the reactor fissile material with a relatively lower burnups is placed in the Central region of the active zone, and with a relatively large burn - in upper and lower peripheral regions. As well as the value of the neutrons produced in the Central region of the active zone is higher than that of neutrons, generated in the periphery, the total rate of generation of neutrons that supports a chain reaction of nuclear fission fuel after the specified permutation cartridges, increases and, consequently, the specified level of energy in the fuel assemblies of the proposed design can be maintained for a longer time than it was possible for Twsi, efficient use of fissile materials in them to the reactor as a whole increases.The drawing shows a sketch of the proposed TVs showing: 1 - the lower part of the suspension fuel assemblies with a Central supporting rod 2; 3 - two removable cassettes, each of which represents a set of fuel rods 4, the joint spacer bars 5, 6 in the beam around the pipe 7 of the frame; 8 - end parts cassettes intended for docking tapes as each other, and nodes 9, 10 of their axial rod. Bearing rod 2 is fixed on the suspension rail 1 by means of a threaded connection with the pin 11. Pipe 7 of the frame and the fuel rods 4 each cartridge is connected to the spacer bars 5 rigidly, but with each of the multiple gratings 6 - with the possibility of axial sliding by changing the length of the fuel rods depending on the temperature (energy). Each end section 8 of the cassette is an axial projection (continued) pipe frame beyond the ends of the fuel rods, and profile of the protrusion along generatrix has a stepped shape, providing vzaimoobratima and fixing the relative position of the cassette in any axial orientation. The same form and have turned to the cassette part of the nodes 9, 10 of the axial rod. The composition of the sun as follows. The first installation of the fuel assemblies in the reactor core is carried out in such axial orientation of its tapes, when the spacer grating 5, connected to the pipes 7 of the frame rigidly, located near the nodes 9, 10 ties, i.e., as shown in the drawing, and adopted in the FA prototype. Operation of fuel assemblies with such axial orientation of the cassette lasts up until Energoservice it will not be close to the nominal for FA prototype. Then FA is extracted from the reactor and on a special stand being remounting: pin 13 of the nut node 10 is removed, the nut itself fully with the rod 2 is screwed together with an element of interface node 10 with the lower cassette and both cassettes with rod 2 is withdrawn; further, these tapes again on the rod 2 attached, mutually through the end sections 8 are joined and between nodes 9, 10 are fixed so that the grating 5 has been in the area of the pair of tapes each other. After remounting FA is again installed in the reactor core and is maintained there until until averaged over the height of the rate of nuclear fission fuel will not decrease to the level of the nominal Energoservice FA prototype. This for the reason stated above, the overall Energoservice fuel in the FA asked what you show, the efficient use of fissile material in the reactor as a whole by equalizing the distribution of the energy production along the length of the fuel assemblies of the proposed design can be improved in comparison with the nominal for FA-prototype 5. . . 10%, while replacement cartridges are defective fuel rods in fuel assemblies of known construction could at best only approximate it by a fraction of a percent of nominal.Shown on the design drawings of the target node 10 in FA is not optimal, because a nut 12 with the pin 13, the operation of remote dismantling and re (after reorientation cassettes) installation which can only be done by very sophisticated manipulator. However, if instead of the nut with the pin to use spring loaded along the axis of connection of the bayonet type, the node 10 of the coupler cassettes will be more convenient operation.Task easier remounting cassettes FA can be solved by similar changes in the design and terminal node 9.LITERATURE
1. The Byways Of The Century. N. Improvement of fuel assemblies. - Nuclear technology abroad, 1986, 5, PP 17-22.2. Dollezhal N. A. , Emelianov, I. J. Duct nuclear power reactor. - M. : ATiM bearing rod, on which are placed coaxially, through the end sections with vzaimovyazany connected between the two end nodes of the axial coupler attached two removable cassettes, each of which is made in the form of a set of core fuel elements, combined spacer bars in the beam around the pipe frame, characterized in that the end sections of each cartridge is configured to mate with any of the end section of the other cassettes with any of the two endpoints of the axial rod, which is attached to the appropriate form.2. A fuel Assembly under item 1, characterized in that the end sections of each cartridge is made in the form of axial protrusions pipe frame beyond the ends of the fuel elements.3. A fuel Assembly under item 1 or 2, characterized in that the connection of at least one node of the axial tie with a bearing rod made bayonet.
FIELD: nuclear power engineering.
SUBSTANCE: proposed process of recovering fuel assemblies of water-moderated water-cooled reactors incorporating damaged fuel elements, such as leaking ones, includes removal of detachable top nozzle, detection of leaking fuel element, and installation of new fuel element or displacer. Leaking fuel element is extracted by knocking its lower end cap out of bottom spacer grid applying force of not over 140 kgf followed by its pulling applying force not over 30 kgf. Installation of new fuel element or displacer in different areas of fuel assembly needs maximal forces depending on fuel burn-up. This process makes it possible to reduce probability of leaking fuel element destruction in the course of its extraction and damage to new fuel element or displacer can during its installation.
EFFECT: enhanced fuel burn-up due to increasing yield upon replacing leaking fuel elements by new ones in fuel assembly.
FIELD: nuclear power engineering; water-moderated and water-cooled reactors.
SUBSTANCE: proposed device designed for repairing faulty fuel assemblies where damaged and unsealed fuel elements are detected has gripping means for installing fuel element or displacer incorporating grip operating mechanism. The latter is made in the form of kinematically enclosed cable system whose cable is rigidly fixed with gripping means and sequentially engages upper fixed roller, upper movable roller, frictional hauling drum, intermediate roller, and lower fixed roller. Upper movable roller is secured on one end of rocker arm whose other end is joined with load; intermediate roller is disposed above frictional hauling drum and connected to force transducer. Such design of device makes it possible to reduce damage probability to unsealed fuel elements in the course of their extraction and installation, to reduce damage to cladding outer surfaces of new fuel elements or displacers, and to enhance nuclear fuel burnup.
EFFECT: reduced damage probability, enhanced yield of fuel assemblies upon replacement of unsealed fuel elements.
4 cl, 1 dwg