Fuel element test method
SUBSTANCE: method involves determination of helium pressure under cover (9) of a fuel element after its sealing, at which fuel element (1) is kept in a measurement position during the whole test period; local pulse heating of the fuel element is performed in area (4) of compensation volume; time dependence of temperature of cover sections at heating point (10) and in section (12) of the cover, which is remote from the heating point, is recorded during the whole test period. Then, helium pressure and state of the fuel element is evaluated based on it. Prior to local heating throughout the perimeter of the cover part in the compensation volume area a provision is made for elimination of heat transfer. The remote section is chosen on the other side of the compensation volume area; after that, the fuel element is exposed till its temperature is equalised with ambient temperature. Then, ambient temperature below 0°C is created; prior to local heating, the fuel element is kept till its temperature is equalised with new ambient temperature; a heating and measurement cycle is repeated with exclusion of heat transfer along the cover body from the heating point to the remote section.
EFFECT: possible testing of a fuel element on one side of a cover.
The technical field to which the invention relates
The invention relates to nuclear power engineering, in particular to the inspection of fuel elements (Fuel rods), and can be used, for example, during their manufacture.
In the process of manufacture of a fuel Rod of his shell filled with tablets of uranium dioxide and filled with helium under pressure, performing the role of a coolant, install the plug and seal flash-butt welding.
One measure of the reliability of a fuel Rod is stable helium pressure under the shell, which is ensured thanks to its tightness. The pressure drop of helium as a rule, characterizes the fuel rod is not as tight. Also critical is the presence of residual air in the Fuel element.
In this regard, verification of the helium pressure and the presence of air is very important to ensure the quality of Fuel rods.
The level of technology
Common test is the technological control of the helium pressure supplied to the fuel rod prior to final sealing. However, the possible leakage of helium from leaking of Fuel or crashing fill Fuel rod helium require control of helium in the finally assembled the Fuel rods. In addition, technological controls will not provide detection of leakage of the shell, "pollution" helium air, negative�tive affect the performance of the Fuel element.
Known destructive inspection method in which from a certain party take away the fuel and the pressure of helium in it is measured through a puncture in the shell. The disadvantage of spot checks is some unreliability and costs associated with the destruction of the finished Fuel element. In addition, like the previous method, it does not identify the "contamination" helium air (both ways, see "the Development, production and operation of fuel cell power reactors", book 2, ed. by F. G. Reshetnikov. - M.: Energoatomizdat, 1995, pp. 286-288).
The most used non-destructive ultrasonic and thermal methods of pressure testing helium under the fuel Rod cladding.
Known invention "Method of detecting leaking Fuel elements, an application for a patent of the Russian Federation No. 94037398 from 29.09.1994 G., publ. 27.10.1996 G. the Method involves ultrasound scanning of Fuel rods in the test volume, filled with water, registration of ultrasonic signals reflected from dry and wet borders of the inner surface of the cladding. Before scanning increase the pressure in the test volume to a value not exceeding the maximum pressure in the reactor. In addition, scanning is carried out before and after increasing the pressure and the difference of the detected signals to determine the leakage of the Fuel element.
Ability� allows the use to increase the efficiency of detection of defective Fuel rods, to reduce the duration of the verification process, but does not provide identification of the "pollution" of helium with air.
The closest is a set of attributes and the results obtained to the claimed invention is a method presented in the invention titled "Method of control and grading of fuel elements and device for its implementation". For invention issued by the patent RF №2261498, IPC G21C 17/06, G21C 17/02, published 27.09.2005 (application No. 2003132030/06 from 31.10.2003).
This method is chosen as the prototype of the claimed invention.
Prototype method includes controlling the pressure of helium supplied into the fuel element prior to final sealing, and the definition of thermal method of the helium pressure under concentric tube after sealing. For this fuel element at the position of measurement is fixed by the sensor, the signal of which it is clamped and held during the entire monitoring time. Next, perform a local pulsed heating of the fuel element in the area of compensation volume, record the temperature change sections of the fuel element sheath at heating section and on the opposite side, turning 180° (on the remote site), at the beginning and end of time intervals after heating and rotation (recorded in�presents recent temperature dependence). The transfer of thermal energy through the helium inside the fuel element causes a temperature difference on the areas of the shell fuel element is proportional to the helium pressure in the fuel element.
Prototype method provides improving the quality of manufacturing of Fuel elements due to the timely detection and isolation with the leaking Fuel rod cladding and the reliability of their operation in a nuclear reactor, but does not allow to identify the "contamination" helium air, adversely affecting the operational characteristics of the Fuel elements. In addition, it is quite complicated to implement because of the need to ensure access to opposite surfaces of the shell.
The aim of the invention is to provide a method of verification, simplified in implementation and to detect the presence of air under the fuel cladding.
Disclosure of the invention
The invention consists in that in the method of fuel elements, including the definition of the helium pressure under the fuel cladding after its sealing, which hold the fuel element in position measurement during the whole time of the inspection, carry out a local pulsed heating of the fuel element in the area of compensation volume�, record the time dependence of the temperature plots of the shell in the place of heating and remote from the heating area of the shell during the whole time of verification, it is judged on the helium pressure in the fuel element. According to the invention before local heating around the perimeter portion of the sheath in the area of compensation volume provide an exception heat transfer directly through the body of the shell along its length in the opposite direction from the place of heating, choose a remote area on the other side of the field compensation volume, the fuel element is maintained until the equalization of the temperature with the ambient temperature, and after the completion of control create the ambient temperature is below 0°C, before the local heating of the fuel element can withstand up to align its temperature with the new ambient temperature, repeat the heating cycle measurements with the exception of heat transfer on the shell body from the place of heating to a remote site and comparing the obtained time dependences of the surface temperature of space heating and remote area at different ambient temperatures with calibration dependences for different helium pressures and different levels of air content in it.
The technical result, which provides a solution postavljen�th problem, is as follows. Helium filling the fuel element, if it contains air, becomes, depending on its quantity is less thermally conductive. Identifying lower thermal conductivity of the gaseous medium in the fuel Rod through the registration of temperature in different places of the membranes under different conditions of heating allows to judge about what is in intrathecal environment contains air. The possibility to determine the reduction of thermal conductivity intrathecal cooling medium temperature measurement along the fuel Rod makes it possible to do this on one side of the casing, which simplifies the implementation process.
In addition, the invention expands the Arsenal of tools for such appointment.
The presence of signs "before the local heating around the perimeter portion of the sheath in the area of compensation volume provide an exception heat transfer directly through the body of the shell along its length in the opposite direction from the place of heating, choose a remote area on the other side of the field compensation volume, the fuel element is maintained until the equalization of the temperature with the ambient temperature, and after the completion of the create control the temperature of the surrounding environment below 0°C, before the local heating of the fuel element can withstand up to align its temperature with a new ambient �Reda, repeat the heating cycle measurements with the exception of heat transfer on the shell body from the place of heating to a remote site and comparing the obtained time dependences of the surface temperature of space heating and remote area at different ambient temperatures with calibration dependences for different helium pressures and different levels of air in it" suggests that the claimed invention meets the condition of patentability "novelty".
In the prior art did not reveal known means, supplemented by features that distinguish the claimed invention from the prototype, and allows you to retrieve the specified technical result. Thus, according to the applicant, the invention meets the condition of patentability "inventive step".
Brief description of the drawings
The drawing shows a diagram of a device for checking fuel element.
The implementation of the invention
Installation to check the Fuel element 1 comprises a chamber 2 with the cradle 3, suitable to contain the area of compensation volume 4 of the Fuel element 1.
Before performing the test outside in the middle of the field compensation volume 4 is installed an annular container 5 filled with a liquid coolant 6, such as antifreeze. The annular container 5 is provided with inlet and outlet fittings (�and the drawing is not shown) connected respectively with the pump and receiving vessel (not shown).
To test the fuel rod 1 is placed in the chamber 2 on the cradle 3. Stand the rod 1 within the time required for equalization of the temperature with the ambient temperature 7 in the chamber 2. Include the pump in ring capacity 5 circulation 6 with the ambient temperature around 7 to part 8 of the shell 9 and the dissipation. Thanks in part 8 below ring size of 5 to create a plot of thermal stability that prevents heat transfer directly through the body of the shell 9 from the heat 10 (the location of the heater 11, for example, an annular induction) directly on the shell body 9 along its length remote from the place of heating of 10 section 12.
Next, perform localized heating space 10 of the shell 9 of a fuel Rod 1 within a specified time (up to tens of seconds) heater 11. During heating and cooling of the Fuel elements simultaneously measured with the device 13 (e.g., pyrometer) temperature space heating 10 of the shell 9 and with the help of the device 14, the temperature of the remote site 12.
Next, the ambient temperature is reduced to 7 is negative, for example to minus 50°C. As in the first stage of control, the fuel rod 1 is maintained until the equalization of the temperature with the ambient temperature 7, in addition, the liquid coolant is fed into the annular container 5 with the ambient temperature 7, and is carried out for a specified time, local heating space 10 of the shell 9 of a fuel Rod 1 by the heater 11. During heating and cooling of the Fuel elements simultaneously measured with the device 13 (e.g., pyrometer) temperature space heating 10 of the shell 9 and with the help of the device 14, the temperature of the remote site 12.
Compare the time dependence of the temperatures of sections 10 and 12, obtained at different temperatures of the environment 7, with the previously obtained calibration dependences for different helium pressures inside the Fuel elements and different levels of air in it, determine the pressure of helium and air in it.
Thus, the presented data confirm that the implementation of the following set of conditions:
- method of control of fuel elements, which laid the basis for the claimed invention, allows the detection of the presence of air under the fuel Rod cladding and determining the gas pressure in the Fuel element;
- for the claimed invention in the form in which it was characterized in the claims, confirmed the possibility of its implementation using the technical solutions described in the application and become known before the invention was made.
Therefore, the claimed invention meets the condition of "industrial applicability".
A method of testing fuel elements, incl�the following definition of the helium pressure under concentric tube after sealing, in which hold the fuel element in position measurement during the entire time monitoring, local pulsed heating of the fuel element in the area of compensation volume, record the time dependence of the temperature plots of the shell in the place of heating and remote from the heating area of the shell during the whole time monitoring, it is judged on the helium pressure and the condition of the fuel element, characterized in that the local heating around the perimeter portion of the sheath in the area of compensation volume provide an exception heat transfer directly through the body of the shell along its length to the other side of the heating section, in this case choose a remote area on the other side of the field compensation volume, the fuel element is maintained until the equalization of the temperature with the ambient temperature, and after the completion of control create the ambient temperature is below 0°C, before the local heating of the fuel element can withstand up to align its temperature with the new ambient temperature, repeat the heating cycle measurements with the exception of heat transfer on the shell body from the place of heating to a remote site and comparing the obtained time dependences of the surface temperature of space heating and remot� plot at different ambient temperatures with calibration dependences for different helium pressures and different levels of air content in it.
FIELD: power industry.
SUBSTANCE: invention relates to control devices of heat-producing elements (fuel elements). The method includes determination of helium pressure under the shell (11) of the heat-producing element after its sealing at which the heat-producing element (1) is sustained at the measurement position, the local pulse heating of the heat-producing element is performed in the field of the compensation volume (8), the time dependence of temperature of shell sections in the place of heating (10) is registered and on the opposite side of the shell, it is used for estimation of helium pressure and the state of the heat-producing element.. Before local heating the heat-producing element is held until equalization of its temperature with ambient temperature, and after completion of monitoring the ambient temperature below 0°C is formed, before the local heating the heat-producing element is held until equalization of its temperature with new ambient temperature, then the cycle heating-measurement is repeated and the obtained time dependences of pressure at different temperatures are compared with calibration dependences for different helium pressure and different levels of the content of air in it.
EFFECT: providing additional possibility of non-destructive control of heat-producing elements.
FIELD: testing equipment.
SUBSTANCE: in the method in process of exposure of samples of zirconium alloys in the steam and water medium in the temperature range of the light water reactor core they develop a gas discharge plasma in water vapours, afterwards they radiate samples by positively charged hydrogen ions by means of applying of negative electric potential to them relative to the plasma.
EFFECT: approximation of testing conditions of samples of zirconium alloys in steam and water medium to conditions of light water reactor core, which makes it possible to increase validity of predicted picture of behaviour of investigated zirconium alloys in light water reactor core in process of its operation made on the basis of results of these tests.
3 cl, 1 dwg
FIELD: physics, atomic power.
SUBSTANCE: invention relates to means of inspecting nuclear fuel in the form of cylindrical tablets. The apparatus for automated inspection of surface and volume defects of ceramic nuclear fuel comprises an optical image transformer, optical and thermal image recording channels, illumination sources, a system for inputting pulsed thermal flux into the inspected article and a selector which provides synchronous recording of both optical and thermal images.
EFFECT: obtaining reliable results on presence or absence of defects in inspected articles and, as a result, reliable selection of defective and non-defective articles.
7 cl, 6 dwg
FIELD: power engineering.
SUBSTANCE: device comprises shell with sealing end covers to house at least one capsule with analysed specimens fitted in unsealed thin-wall shell of refractory material. Said capsule is connected with gas lines intended for streaming ventilation of capsule working space. Outlet of every line is plugged for capsule sealing, plugs being composed of sleeves with axial holes filled with fusible material. One of the lines houses thermometer transducers. Note here that sensor of every transducer is fitted inside capsule working space.
EFFECT: measurement of temperatures of emissions at nuclear disintegration during experiments, simplified design of capsule seals.
4 cl, 1 dwg
SUBSTANCE: fuel element simulator has a shell in which there is a column of natural fuel tablets with a centre hole, and an electric heater placed with clearance in the holes of the tablets. The heater is in form of pipe made of heat-resistant material on the outer surface of which is formed a microrelief which varies on the length of the heater and which provides optically variable properties on the length of the surface, which correspond to the simulated temperature profile. A shielding pipe made of heat-resistant material is also placed with clearance on the outside coaxial to the shell, the inner and outer surfaces of said pipe also having a varying microrelief which provides optically variable properties on the length of the heater.
EFFECT: high accuracy of simulating the thermal state of fuel elements under investigation by obtaining temperature levels, thermal flux and temperature profiles similar to those in full-scale conditions.
7 cl, 2 dwg
FIELD: power engineering.
SUBSTANCE: device arranged on a stand (4), comprises a place (31) with a horizontal axis (X) for placement of the above fuel rod; a facility (20) for measurement of deviation from parallelism and a facility (22) for correction of the above deviation. The device comprises a facility (14) of device positioning relative to the fuel rod comprising two parallel supports arranged at the distance from each other, at the same time each of them supports the end of the above fuel rod. The supports are made in the form of two horseshoe-shaped parts (16.1. 16.2), the inner ends of which are designed for resting against the fuel rod, and are distanced from each other at the specified distance to ensure the coverage of the stand support, at which the end rests with the upper plug of the fuel rod, and which has thickness that is substantially equal to the distance between two horseshoe-shaped parts (16.1, 16.2). Also the device comprises a facility (32) to retain a fuel rod made as capable of providing for rotation of the fuel rod around its longitudinal axis, which is arranged between the facility (14) of positioning and facilities of measurement and correction. The facility (32) comprises a lower grip (34) and an upper grip (36), to hold the fuel rod, at the same time the lower grip (34) forms a base for measurement of deviation from parallelism.
EFFECT: provision of measurement of deviation from parallelism during correction of the above deviation.
12 cl, 15 dwg
FIELD: power industry.
SUBSTANCE: specimen is made of two coaxially combined tubular elements; one of which is fully or partially located inside the other one; gas pressure is created in a cavity between elements, sealed, arranged in a nuclear reactor and irradiated.
EFFECT: increasing informativity and reliability of results of change of properties of reactor materials at irradiation in the reactor at various types of stress-and-strain state.
3 cl, 1 dwg
FIELD: power engineering.
SUBSTANCE: time-series data by reactivity is produced from time-series data by a neutron bundle by the method of reverse dynamic characteristic in respect to a single-point kinetic equation of the reactor. Time-series data by fuel temperature exposed to previously determined averaging is produced using time-series data by power output of the reactor and pre-determined dynamic model. The component of contribution to feedback by reactivity is determined using time-series data by reactivity and introduced reactivity. The Doppler coefficient of reactivity is determined using the received time-series data by average temperature of a moderator in the reactor, time-series data by fuel temperature exposed to previously determined averaging, isothermic temperature coefficient of reactivity and component of contribution to feedback by reactivity.
EFFECT: increased accuracy and simplicity of measurements of the Doppler coefficient and possibility of its usage in case of use of discrete data.
8 cl, 7 dwg
FIELD: power industry.
SUBSTANCE: nuclear fuel pellet density monitoring plant includes measuring unit including gamma radiation source and detection unit, transfer mechanism for movement of pellets and hold-down device, as well as measuring result control and processing unit intended to control the operation of transfer mechanism for processing of measuring results and rejection of pellets. Transfer mechanism includes the first transfer assembly for movement of column of pellets through measuring assembly with reference to outlet pallet, the second transfer assembly for movement of reference and outlet pallet for columns of pellets in transverse direction, and hold-down device has the possibility of pressing the pellets during movement of column of pellets through the measuring unit.
EFFECT: invention allows increasing the monitoring efficiency due to supply to monitoring zone of nuclear fuel pellets in the form of columns and performance of measurement during movement of columns through the monitoring zone.
2 cl, 1 dwg
FIELD: power engineering.
SUBSTANCE: method of creep-rupture test of tubular samples in a non-instrumentation channel of a nuclear reactor includes the following operations. At least one reference tubular sample loaded with inert gas pressure is placed into a heating furnace, maintained at the preset temperature in the heating furnace until destroyed, and time is measured to the moment of its destruction. Two tubular sample accordingly loaded and non-loaded with inert gas pressure are simultaneously placed into an ampoule. The tight ampoule with both types of tubular samples is radiated in a nuclear reactor channel. The radiated tubular samples are placed into a heating furnace and tested until destroyed under pressures and temperatures similar to the ones in the reactor. The time is measured to the moment of destruction of tubular samples of the first and second types in the heating furnace. The time to the moment of tubular sample destruction under conditions of reactor radiation at the preset pressure and temperature is determined using the ratio that takes into account time values measured in process of method realisation.
EFFECT: invention makes it possible to increase accuracy of detection of strength characteristics of materials.
FIELD: operating uranium-graphite reactors.
SUBSTANCE: proposed method for serviceability check of process-channel gas gap in graphite stacking of RBMK-1000 reactor core includes measurement of diameters of inner holes in graphite ring block and process-channel tube, exposure of zirconium tube joined with graphite rings to electromagnetic radiation, reception of differential response signal from each graphite ring and from zirconium tube, integration of signal obtained, generation of electromagnetic field components from channel and from graphite rings, separation of useful signal, and evaluation of gap by difference in amplitudes of signals arriving from internal and external graphite rings, radiation amplitude being 3 - 5 V at frequency of 2 - 7 kHz. Device implementing this method has calibrated zirconium tube installed on process channel tube and provided with axially disposed vertically moving differential vector-difference electromagnetic radiation sensor incorporating its moving mechanism, as well as electronic signal-processing unit commutated with sensor and computer; sensor has two measuring and one field coils wound on U-shaped ferrite magnetic circuit; measuring coils of sensor are differentially connected and compensated on surface of homogeneous conducting medium such as air.
EFFECT: ability of metering gas gap in any fuel cell of reactor without removing process channel.
2 cl, 9 dwg
FIELD: nuclear power engineering.
SUBSTANCE: proposed invention may be found useful for optimizing manufacturing process of dispersion-type fuel elements using granules of uranium, its alloys and compositions as nuclear fuel and also for hydraulic and other tests of models or simulators of dispersion-type fuel elements of any configuration and shape. Simulators of nuclear fuel granules of uranium and its alloys are made of quick-cutting steel alloys of following composition, mass percent: carbon, 0.73 to 1.12; manganese and silicon, maximum 0.50; chromium, 3.80 to 4.40; tungsten, 2.50 to 18.50; vanadium, 1.00 to 3.00; cobalt, maximum 0.50; molybdenum, 0 to 5.30; nickel, maximum 0.40; sulfur, maximum 0.025-0.035; phosphor, maximum 0.030; iron, the rest.
EFFECT: enhanced productivity, economic efficiency, and safety of fuel element process analyses and optimization dispensing with special shielding means.
1 cl, 3 dwg
FIELD: identifying o spent fuel assemblies with no or lost identifying characteristics for their next storage and recovery.
SUBSTANCE: identifying element is made in the form of circular clip made of metal snap ring or of two metal semi-rings of which one bears identification code in the form of intervals between longitudinal through slits. Clip is put on fuel assembly directly under bracing bushing and clip-constituting semi-rings are locked in position relative to the latter without protruding beyond its outline. For the purpose use is made of mechanical device of robot-manipulator type. Identification code is read out by means of mechanical feeler gage and sensor that responds to feeler gage displacement as it engages slits. Identifying elements are installed under each bracing bushing.
EFFECT: ability of identifying fragments of spent fuel assembly broken into separate parts before recovery.
10 cl, 4 dwg
FIELD: analyzing metals for oxygen, nitrogen, and hydrogen content including analyses of uranium dioxide for total hydrogen content.
SUBSTANCE: proposed analyzer depending for its operation on high-temperature heating of analyzed specimens has high-temperature furnace for heating uranium dioxide pellets and molybdenum evaporator; molybdenum evaporator is provided with water-cooled lead-in wire, and molybdenum deflecting screen is inserted between molybdenum evaporator and furnace housing.
EFFECT: simplified design of electrode furnace, reduced power requirement.
1 cl, 1 dwg
FIELD: the invention refers to analytical chemistry particular to determination of general hydrogen in uranium dioxide pellets.
SUBSTANCE: the installation has an electrode furnace with feeding assembly , an afterburner, a reaction tube with calcium carbide, an absorption vessel with Ilovay's reagent for absorption of acetylene, a supply unit. The afterburner of hydrogen oxidizes hydrogen to water which together with the water exuding from pellets starts reaction with carbide calcium. In result of this equivalent amount of acetylene is produced. The acetylene passing through the absorption vessel generates with Ilovay's reagent copper acietilenid which gives red color to absorption solution. According to intensity of color of absorption solution the contents of general hydrogen are determined.
EFFECT: simplifies construction of the installation, increases sensitivity and precision of determination of the contents of hydrogen in uranium dioxide pellets.
2 cl, 1 dwg
FIELD: analog computer engineering; verifying nuclear reactor reactivity meters (reactimeters).
SUBSTANCE: proposed simulator has m threshold devices, m threshold selector switches, m series-connected decade amplifiers, m electronic commutators, n - m - 1 series-connected decade frequency dividers, first group of m parallel-connected frequency selector switches, second group of n - m frequency selector switches, and group of n - m parallel-connected mode selector switches. Integrated inputs of threshold selector switches are connected to output of high-voltage amplifier and output of each threshold selector switch, to input of respective threshold device; output of each threshold device is connected to control input of respective electronic commutator; inputs of electronic commutators are connected to outputs of decade amplifiers and outputs are integrated with output of group of mode selector switches and with input of voltage-to-frequency converter; output of inverting amplifier is connected to input of first decade amplifier and to that of group of mode selector switches; input of first group of frequency selector switches is connected to output of voltage-to-frequency converter and to input of first decade frequency divider and output, to integrated outputs of first group of frequency selector switches and to input of division-chamber pulse shaper input; each of inputs of second group of frequency selector switches is connected to input of respective decade frequency divider except for last one of this group of switches whose input is connected to output of last decade frequency divider; threshold selector switches and frequency selector switches of first group, as well as m current selector switches have common operating mechanism; mode selector and frequency selector switches of second group have common operating mechanism with remaining n - m current selector switches. Such design makes it possible to realize Coulomb law relationship at all current ranges of simulator for current and frequency channels.
EFFECT: ability of verifying pulse-current input reactimeters by input signals adequate to signals coming from actual neutron detector.
2 cl, 1 dwg
FIELD: atomic industry.
SUBSTANCE: proposed line is provided with computer-aided system for contactless control of flaw depth and profile on surface of fuel element can and on end parts including sorting-out device that functions to reject faulty fuel elements. This line is characterized in high capacity and reduced labor consumption.
EFFECT: enlarged functional capabilities, improved quality of fuel elements.
1 cl, 2 dwg
FIELD: nuclear fuel technology.
SUBSTANCE: invention relates to production of pelleted fuel and consists in controlling nuclear fuel for thermal resistance involving preparation for selecting pellets from nuclear fuel lot for measuring diameter, which preparation consists in dedusting. Selected pellets are placed in temperature-stabilized box together with measuring instrument. Diameter of each pellet is them measured and measurement data are entered into computer. Thereafter, pellets are charged into heat treatment vessel, wherein pellets are heated in vacuum at residual pressure not exceeding 7·10-2 Pa at heating velocity not higher than 10°C/min to 100-160°C and held at this temperature at most 2 h, whereupon heating is continued under the same conditions to 1470-1530°C and this temperature is maintained for a period of time not exceeding 4 h, after which hydrogen is fed with flow rate 2-6 L/min. Humidity of gas mix is measured in the heat treatment outlet. If humidity of gas mixture in the heat treatment outlet exceeds 800 ppm, hydrogen feeding is stopped and material is subjected to additional vacuum degassing at residual pressure below 7·10-2 Pa and held at 1470-1530°C in vacuum for further 4 h. Hydrogen feeding is the repeated at 2-6 L/min. If humidity of gas mixture in the heat treatment outlet is below 800 ppm, preceding temperature is maintained not longer than 2 h and raised to 1625-1675°C at velocity 40-60°C/h and then to 1700-1750°C at velocity 15-45°C/h. When outlet humidity of mixture is 500-750 ppm, hydrogen feeding is lowered to 1 L/min. Temperature 1700-1750°C is maintained during 24±2 h, after which pellets are cooled to 1470-1530ºC at velocity not higher than 10°C/min. Hydrogen is replaced with argon and cooling is continued to temperature not higher than 40°C, which temperature is further maintained. Outside diameter of each pellet from the selection is measured to find average diameter of pellets before and after heat treatment in order to calculate residual sintering ability. When this parameter equals 0.0-0.4%, total lot of pellets is used in fuel elements and in case of exceeding or negative residual sintering ability the total lot of pellets is rejected.
EFFECT: improved pellet quality control.
FIELD: power engineering; evaluating burnout margin in nuclear power units.
SUBSTANCE: proposed method intended for use in VVER or RBMK, or other similar reactor units includes setting of desired operating parameters at inlet of fuel assembly, power supply to fuel assembly, variation of fuel assembly power, measurement of wall temperature of fuel element (or simulator thereof), detection of burnout moment by comparing wall temperatures at different power values of fuel assembly, evaluation of burnout margin by comparing critical heat flux and heat fluxes at rated parameters of fuel assembly, burnout being recognized by first wall temperature increase disproportional relative to power variation. Power is supplied to separate groups of fuel elements and/or separate fuel elements (or simulators thereof); this power supplied to separate groups of fuel elements and/or to separate fuel elements is varied to ensure conditions at fuel element outlet equal to those preset , where G is water flow through fuel element, kg/s; iout, iin is coolant enthalpy at fuel element outlet and inlet, respectively, kJ/kg; Nδi is power released at balanced fuel elements (or simulators thereof) where burnout is not detected, kW; n is number of balanced fuel elements; Nbrn.i is power released at fuel elements (or element) where burnout is detected; m is number of fuel elements where burnout is detected, m ≥ 1; d is fuel element diameter, mm.
EFFECT: enhanced precision of evaluating burnout margin for nuclear power plant channels.
1 cl, 2 dwg
FIELD: analytical methods in nuclear engineering.
SUBSTANCE: invention relates to analysis of fissile materials by radiation techniques and intended for on-line control of uranium hexafluoride concentration in gas streams of isotope-separation uranium processes. Control method comprises measuring, within selected time interval, intensity of gamma-emission of uranium-235, temperature, and uranium hexafluoride gas phase pressure in measuring chamber. Averaged data are processed to create uranium hexafluoride canal in measuring chamber. Thereafter, measurements are performed within a time interval composed of a series of time gaps and average values are then computed for above-indicated parameters for each time gap and measurement data for the total time interval are computed as averaged values of average values in time gaps. Intensity of gamma-emission of uranium-235, temperature, and pressure, when computing current value of mass fraction of uranium-235 isotope, are determined from averaged measurement data obtained in identical time intervals at variation in current time by a value equal to value of time gap of the time interval. Computed value of mass fraction of uranium-235 isotope is attached to current time within the time interval of measurement. Method is implemented with the aid of measuring system, which contains: measuring chamber provided with inlet and outlet connecting pipes, detection unit, and temperature and pressure sensors, connected to uranium hexafluoride gas collector over inlet connecting pipe; controller with electric pulse counters and gamma specter analyzer; signal adapters; internal information bus; and information collection, management, and processing unit. Controller is supplemented by at least three discriminators and one timer, discriminator being connected to gamma-emission detector output whereas output of each discriminator is connected to input of individual electric pulse counter, whose second input is coupled with timer output. Adapter timer output is connected to internal information bus over information exchange line. Information collection, management, and processing unit is bound to local controlling computer network over external interface network.
EFFECT: enabled quick response in case of emergency deviations of uranium hexafluoride stream concentration, reduced plant configuration rearrangement at variation in concentration of starting and commercial uranium hexafluoride, and eliminated production of substandard product.
24 cl, 5 dwg