The method of obtaining carbon products
The invention relates to the field of production of carbon-graphite materials and, in particular, can be used in the manufacture of nuclear fuel and powder metallurgy. The inventive method of obtaining carbon products is that preparing a mixture of a graphite powder, a binder and MICROTEL. The resulting mixture is subjected to a preliminary pressing, then carry out a heat treatment, during which periodically reduce the temperature of products in the areas of phase transitions 10-15C, and the temperature interval between the depressions temperature chosen in the range of 20-30C. advantages of the invention lie in the decline of marriage in the products by preventing crack formation. 1 table, 2 Il.The invention relates to the field of production of carbon-graphite materials and can be used in the technology of nuclear fuel and powder metallurgy.Currently, carbon-graphite materials have found application in high temperature gas cooled reactors (HTGR), in which fuel elements (cartridges) made in the form of carbon-graphite matrix containing microtia is arbid silicon.After pre-mixing MT, graphite powder and a binder (coal tar pitch, phenol resin, etc.) billet rods pressed and then subjected to heat treatment, in which the polymerization of the binder, the carbonization of the binder due to pyrolysis emitting solid coke residue and gaseous pyrolysis products (phenol, carbon monoxide, hydrogen, and others). The last stage of thermal treatment is heating up to 1800With the final removal of gaseous products.In the process of obtaining fuel, the yield decreases, mainly due to the appearance of cracks in the products. Cracks caused by internal pressure of the gaseous products, which in the conditions of pyrolysis tar grows to a significant size. So, when the heat source blend containing 18 wt.% phenol-formaldehyde resin in the sample volume of 10 cm3and a mass of 10 g is allocated 1 normal liter of gaseous products. If we consider that the porosity of the billet after extrusion is 40%, then when the pyrolysis temperature of the workpiece develops a pressure of 300 ATM.Prevention of crack formation provide dopolnitvah powder (application No. 6-36052 from 12.12.88,, Japan, ΜM G 21 3/62). The disadvantage of this method lies in the complexity of additional technological operations.Another way to prevent cracking is to carry out heat treatment under pressure in the mold (application No. 19837989 from 21.08.98, Germany, MKI G 21 21/00). The disadvantage of this method lies in the complexity of instrumentation, which leads to the impossibility of application of the method for mass production of fuel elements.The closest in technical essence to the problem at hand is a method of heat treatment of carbon products (rods and absorbing elements of HTGR) (patent No. 3435863 Germany, MKI G 21 3/22, 21/04, Appl. 29.04.84,, publ. 03.04.86,) consists in preparing a mixture of graphitized grains of coke and phenol-formaldehyde resin, mixing microtubule binding, preliminary compressing the mixture, napressovannye for the provision of a fuel rod casings of grains of coke followed by heat treatment up to 2000C. the Disadvantage of this method is similar to the lack of first presents unique and lies in the complexity of additional technological operations and cracks.The present invention is the task of reducing defects in the products due predoc, pressed and thermoablative, when this heat treatment is conducted periodically reducing the temperature of products in the field of phase transitions 10-15C, and the temperature interval between the depressions temperature chosen in the range of 20-30C.The proposed method differs from the known mode of heat treatment of carbon products.The authors of the invention on the basis of the research found that the emission in the areas of phase transitions can be stopped by reducing the temperature of the product. In Fig.1 presents derivatograph phase changes in the workpiece cylindrical fuel rod with a diameter of 12.9 mm, height 53 mm (1 - curve of temperature rise; 2 - the mass of the sample; 3, 4 - differential temperature and sample mass, temperature, pending on the y axis refers to curve 1, all other curves are given without scale), the initial mixture consisted of 73 wt.% graphite, 9 wt.% MT-0.7-0.8 mm and 18 wt.% phenol-formaldehyde resin. The curves on the curve 2 in the temperature range of 70-130To meet stage polymerization resin in the temperature range 240-400C - stage pyrolysis (with sequential allocation of phenol, water, carbon monoxide, wadati changes in sample mass. At the same time eye-catching coke residue begins to impede diffusion of the products of pyrolysis of the sample. The meaning of the invention is to stutter passing regions of phase transitions for a large part of the gaseous products was prediffusion from the sample before the coke residue will close the pores of the sample.In Fig.2 shows thermograms of carbonization processes billet rods on the prototype method (1) and proposed method (2). It is seen that the interval 240-400With corresponding phase transitions during carbonization, passed with a ninefold decrease in the temperature every 20C. we Can assume that if complete blockage of pores at 380-400From inside the sample remains 1/9 of the total number of released gases and vapors, which dramatically reduces the likelihood of cracking. Heat treatment is not brought up to 1800-2000(The prototype), because cracks occur at the stage of carbonization at 200-800C.The amplitude reduction temperature is selected based on the sensitivity of thermocouples (5-10C). The time interval of the temperature reduction is dictated inertsionnosti temperature reduction (10-15C) occurs after 10-20 minutes the Temperature interval between the peaks of the temperature reduction (20-30C) choose from considerations reduce the gas pressure in 6-9 times in the range 240-400With nine peaks in the interval 20With six peaks in the interval 30C).The proposed method of producing carbon products in addition to the main task of eliminating cracks has the following additional advantages compared with the known:1. Has a wide scope for the products in the form of cylinders, spheres, prisms and products more complex geometry.2. Has a universal character, since this mode of treatment does not depend on the type of graphite, resin type, size of the graphite particles and the MT, the ratio of components in the product.The proposed method is as follows. The graphite powder with a particle size of 30-100 μm is mixed with a solution of phenol-formaldehyde resin in alcohol and MT diameter of 0.8 mm, the Composition of the mixture (excluding alcohol): graphite 73 wt.%, resin 18 wt.%, MT 9 wt.%. After preliminary pressing portions 10-11 g of a mixture in the matrix by bilateral compression samples are loaded into a quartz furnace for heat treatment, which is the province of the imps and the proposed method are presented in the table. In the experiments used two types of graphite: PGM-KS (Russia) and CL (France).Examples of implementation are presented for two-phase composite material, rather than for graphite, because it is the composites have high hardness, low ductility, so the voltage in such materials relax by fracturing (Mechanics of composite materials. Ed.J. Sendecki. M., Mir, 1978, S. 32).These tables show that when the modes presented in the claims, provided the yield (no cracks) 100%. When carrying out the heat treatment according to the method of the prior art (examples 1, 2) yield is 50-75%.
ClaimsThe method of obtaining carbon products, including mixing graphite powder, microtalon and a binder, pre-compressing the mixture and heat treatment, wherein the heat treatment is carried out periodically reducing the temperature of products in the areas of phase transitions 10-15C, and the temperature interval between the depressions temperature chosen in the range of 20-30C.
FIELD: atomic power engineering.
SUBSTANCE: device has welding chambers having apertures for inputting covers for pressurization, which concurrently are output apertures of heat-conductive elements, welding chambers electrodes, power source, transporting module for transverse product feed, common control system with blocks for parallel and serial connection, device for forming a break in secondary contour. Welding chambers are placed in parallel to each other at distance from each other, determined from formula S=t(m k+1), where S - distance between chambers axes, t - step of transport module, k - number of chambers in device equal to number of steps of transporting module in each singular step thereof, m - any integer starting from one, and control systems connected through parallel connection block to working tools of device of same names, and through block for serial connection to welding force drive and to device for forming break in secondary contour of power source, as well as to power source connected in parallel to welding chambers electrodes.
EFFECT: higher efficiency.
4 cl, 1 dwg
FIELD: nuclear power engineering; manufacture of fuel elements and their claddings.
SUBSTANCE: each weld of cladding and its plug are tested in facility equipped with units for clamping and revolving the claddings, scanning with carriage using weld inspection piezoelectric transducer and piezoelectric transducer for measuring wall thickness in measurement region, immersion bath, ultrasonic pulse generator, ultrasonic pulse receiver, microprocessor, analog-to-digital converter switch, and random-access memory.
EFFECT: enhanced quality of fuel elements and their operating reliability in reactor core.
1 cl, 1 dwg
FIELD: power engineering, namely nuclear power reactors, particularly sealing of fuel elements by means of contact butt welding with use of plugs.
SUBSTANCE: apparatus includes sealed welding chamber with housing non-detachable at operation and having through duct for feeding parts to welding zone; mechanisms for sealing welding chamber; device for feeding parts to welding zone; additional clamp of tube; mechanisms for gripping and fixing welded parts; drive device for supplying welding pressure; autonomous drive units. Mechanisms for gripping and fixing welded parts are in the form of collet chucks with respective drives. Welding pressure supply drive device is connected with electrode holder of plug. Welding chamber is restricted by non-detachable housing and flange-current supply lead that is fluid -tightly connected with housing and fixed relative to housing at operation. One collet chuck has annular detachable current supply lead in the form of sectors and it rests by its end at side of large base of petal cone upon said flange-current supply lead. Collet chuck of tube grip and electrode-holder of plug have coaxial electrically insulated one relative to other tie rods arranged in through duct of chamber and joined with autonomous drive units.
EFFECT: enhanced stability of process, improved quality of welded joint due to lowered misalignment of tube and plug.
FIELD: nuclear power engineering; manufacture of fuel elements for fuel assemblies of nuclear power reactors.
SUBSTANCE: proposed process line has mechanism for press-fitting bottom plug in calibrated end of can provided with cutoff gear for piece-by-piece feeding of bottom plugs of different types that incorporates bottom plug passage duct accommodating C-shaped member with reciprocating horizontal-motion actuator whose top flap has slot engageable with upper cylindrical part of bottom plug; bottom flap is longer than top one and is provided with bottom plug passage hole shifted toward edge of bottom flap; flaps are spaced apart through distance slightly longer than maximal length of thick end of bottom plug; rod designed for press-fitting bottom plug in calibrated end of can has bed with seat to receive bottom plug, maximal-size portion of seat following shape of bottom plug.
EFFECT: enlarged functional capabilities of process line for manufacturing fuel-element cans of different sizes.
1 cl 7 dwg
FIELD: mechanical engineering.
SUBSTANCE: proposed method is intended for manufacturing fuel elements using resistance-butt welding primarily for their joining to zirconium alloy cans. Welding is effected at equipment electrical resistance not over 30-fold resistance of can section forming welded joint having or not point discontinuities in the form of separate spots or chain of such spots forming no continuous line and measuring maximum ten thicknesses of weld in cross-sectional area of welded joint under check disposed at distance equal to two or three thicknesses of can wall from butt-end of plug located inside fuel element, welded joint being checked by uniformity of external fin. Length of poor fin formation section does not exceed 10% of joint perimeter.
EFFECT: enhanced quality of welds and reliability of fuel element sealing.
FIELD: nuclear power engineering; tubular dispersed-core three-layer fuel elements.
SUBSTANCE: proposed method includes production of powder mixture, powder mixing in plasticizer environment, cold molding in core billet with plasticizer, thermal sintering, hot molding-calibration of fuel core, core placing in can made in the form of sleeve with annular slot, calibration, hot molding through die, and drawing; inner surface of external can of sleeve is provided with longitudinal bulges and outer surface bears bulge location marks; fuel core is provided with longitudinal flats and placed in sleeve taking care to align bulges of the latter with core flats; in the course of drawing marks are aligned on arbor ribs.
EFFECT: enhanced stability of active layer and can thickness in shaping polyhedral fuel elements.
1 cl, 4 dwg
FIELD: nuclear power engineering.
SUBSTANCE: proposed fuel assembly primarily designed for use in nuclear power reactors VVER-1000 and VVER-440 has composite bottom spacer grid built of at least two parts identical with respect to disposition of holes and total thickness of component parts equal to height of circular collar on bottom plug of fuel element, and tubular channel hole diameter for bottom plugs equal to diameters of lower ends of bottom plugs; the latter are secured in holes of aligned parts of bottom spacer grid by shifting component parts of bottom spacer grid relative to each other, by locking bottom plugs on circular collar of bottom plugs between annular projections of upper and lower parts of bottom spacer grid, and by aligning flow holes of bottom spacer grid component parts. Component parts of bottom spacer grid are rigidly fixed upon their shifting to bottom nozzle of fuel assembly in case of nonseparable type of assembly and loosely attached upon their shifting to bottom nozzle in case of separable type of assembly.
EFFECT: enhanced reliability of fixing fuel element plugs in bottom grid holes of separable and nonseparable fuel assemblies, reduced labor consumption for manufacture and assembly.
1 cl, 3 dwg
FIELD: nuclear power engineering; manufacture of fuel elements for fuel assemblies of power reactors.
SUBSTANCE: proposed process line has mechanism for weighing can charged with fuel pellets installed past retainer press-fitting mechanism; can is coupled through computer with mentioned weighing mechanism for outputting data on pure mass of pellets in can; γ-quanta detecting units and pellet enrichment automatic control installations are mounted on charged can guiding facility in the form of rolling train between its rollers throughout length of charged pellet stack; detecting units are disposed around pellet stack charged in can with collimation channels shifted throughout length of charged pellet stack; detecting units are provided with photoelectronic multipliers, spectrometers, and data acquisition, processing and outputting computer. Each detecting unit is provided with through hole passing can-displacement tungsten tube; shifted collimation channels are provided in top and bottom parts of tungsten tube; photoelectronic multipliers are disposed on butt-ends of detecting unit.
EFFECT: enhanced quality of fuel element manufacture.
3 cl, 3 dwg
FIELD: nuclear power engineering, possibly automatic line for producing fuel elements of fuel assemblies of power nuclear reactors.
SUBSTANCE: aggregate is provided with detachable device for measuring electric resistance of fitting. Said device is arranged between collet chucks being in open position and it is made of two dielectric members spring-loaded one relative to other. End of one of said members has shape corresponding to contour of annular turning formed coaxially on end of collet chuck for plug. End of second member has shape corresponding to contour of annular turning formed coaxially on end of fitting in collet chuck for fuel element envelope. Said device has spring-loaded contacts for measuring electric resistance between fitting inside collet chuck and collet chuck itself. Caprolactam is used as dielectric material.
EFFECT: enhanced efficiency and quality of contact butt welding at sealing fuel element.
2 cl, 3 dwg
FIELD: nuclear power engineering.
SUBSTANCE: members used for fastening fuel element in hole of bottom end spacer grid are made in the form of shortened plug that has coaxial blind hole on its butt-end formed by annular walls expanded (burnished) in hole of larger diameter within bottom end spacer grid.
EFFECT: enhanced reliability of fuel assembly, reduced manufacturing cost and structural material input.
1 cl, 3 dwg