The method of determining the cladding of a fuel rod during experimental testing in a nuclear reactor and a device for its implementation

 

(57) Abstract:

The invention relates to the nuclear industry, namely, creating and experimental handling of fuel elements of nuclear reactors. Constant thermal power of the nuclear reactor to measure the density of heat generation in the fuel material, record the time of precondensation fuel material, and the temperature of the shell of a fuel rod is determined from the proposed expression. The unit contains a fuel rod, comprising a shell, inside of which is placed with a gap of the fuel material, the calorimeter integral of the heat flux and thermocouple. Inside of a fuel rod concentric with its axis on the end shell of a fuel rod is installed with a gap of thin-walled glass, inside of which is placed a fuel material of a thickness less than the diameter of the glass, thus the value of the gap corresponds to a particular value. Technical result - increase the accuracy of the cladding of a fuel rod. 2 S. and 4 C.p. f-crystals, 4 Il.

The invention relates to nuclear energy, to the creation and ground testing of fuel elements (in particular, thermionic fuel elements in nuclear reactors.

The main challenges when creating reactors associated with the development of safe working of a fuel rod. For those who TVEL by analogy with spent fuel assemblies (FA) conventional reactors called the electricity generating Assembly (EHS) or the electricity generating channel (TFE). Usually EHS consists of series-connected electricity generating element AGA), which actually takes a full cycle of energy conversion.

Performance evaluation and prediction of service life of the fuel rods need to know the temperature of the shell of a fuel rod, because this feature has a decisive impact on the compatibility of the material of the shell of TVEL fuel material (TM), on the strength characteristics of the material of the sheath of the fuel element. In addition, for thermionic fuel element temperature of the emitter membrane of a fuel rod has a decisive impact on the energy characteristics (density electrical power, efficiency) AGE [1]. As a rule, experimental testing of fuel rods held in channels research nuclear reactors [1, 2].

Direct measurement of the cladding of a fuel rod, especially the temperature of the emitter shell thermionic fuel elements in multielement composition EHS associated with extraordinary technological difficulties [3].

Known methods of determining the cladding of a fuel rod during experimental testing in a nuclear reactor, for example, by the method of reference points [3] or determine the temperature of emitte the point, although an experimental method requires the prior rather time-consuming experimental or computational research, reasonable testing series of single EHS. Due to technological difficulties and heavy working conditions are often observed relatively unstable and rapid failure of high-temperature thermocouples installed on the emitter shell thermionic fuel elements [3]. Temperature control the emitter membrane of a fuel rod in its electrical resistance when the loopback test is limited only singleton EHS, working only in the vacuum mode, although the main energy mode of operation, which are all reactor tests of thermionic fuel elements, is arc (bit) mode [5]. In addition, when the loopback test odnostvolnyj EHS in the vacuum mode, the control error of the temperature of the emitter membrane fuel by this method is also low [4].

Closest to the invention to the technical essence is a way to determine the cladding of a fuel rod during experimental testing in a nuclear reactor, including the measurement of the density of heat dissipation in the TM, the temperature evaluation osolpartmenu emitter membrane TVEL (Tabout) can be found from the solution relative to Taboutthe heat balance equation, elementary plot the emitter membrane of a fuel rod

< / BR>
where Taboutthe temperature of the shell of a fuel rod;

qFthe density of heat flow in the emitter shell thermionic fuel elements from TM;

CR(Tabout) - dependent Taboutgiven the coefficient of thermal radiation electrode of the pair of emitter-collector;

- Stefan - Boltzmann constant;

Tcthe temperature of the collector;

Cs- thermal conductivity of the cesium vapor;

L is the interelectrode gap;

j is the current density;

qe- heat flow out of the emitter current equal to 1A.

The main disadvantage of thermal balance is low accuracy of the calculation of the cladding of a fuel rod mainly due to the significant dependence of the results from a large number of controlled parameters (qF,CRTwith,Cs, L, j, qe), who during the experiments are determined or known with great accuracy [6]. As a result, the error in the determination of Tabout(1) is large enough.

The known device for determining the temperature about the market emitter shell thermionic fuel elements for loop tests singleton EHS, operating in the vacuum mode, the electric resistance of the emitter sheath of the fuel element described in [4, 7]. However, the use of such devices is possible only for experimental testing singleton EHS working only in a vacuum mode, and it is impossible for multiple EHS working in arc mode [5]. In addition, when the loopback test odnostvolnyj EHS in the vacuum mode, the control error of the temperature of the emitter membrane fuel by this method is also low [4]. When loopback tests there is also a method of determining the temperature of the emitter shell thermionic fuel elements, which is a staple in most foreign testing single AGE and which was used to determine the cladding of a fuel rod during loopback testing EHS for reactor-Converter TOPAZ, where it is made in the form layout AGE, construction to the maximum extent possible to approximate to the design loop AGE and analyzed in laboratory conditions, described in [8, 9]. However, the method loopback tests EHS, using as models AGE, has high accuracy, primarily because of the impossibility of a complete simulation of petersnet is a device for determining the cladding of a fuel rod when experimental development in the nuclear reactor, containing a fuel rod, comprising a shell, inside of which is placed with a gap of the fuel material, the calorimeter integral of the heat flux and thermocouple shown in [10] as applied to measuring the temperature of the emitter shell thermionic fuel elements. The device includes setting at the end of a fuel rod thermocouple, which directly measures the temperature of the end part of the membrane of a fuel rod. Direct measurement of the cladding of a fuel rod is connected with the extraordinary technological difficulties. Especially difficult is the measurement of the temperature of the fuel cladding applied to multielement EHS, where thermocouple node must have good electrical insulation, high-vacuum density in a couple of cesium and sufficient resource of work at temperatures of 1800-K in the field of ionizing radiation [3].

The technical result that is achievable with the use of the invention is to improve the accuracy of determination of the cladding of a fuel rod.

This technical result is achieved by a method for determining the cladding of a fuel rod during experimental testing in a nuclear reactor, including the measurement of the density of heat generation in the fuel material, estimate the temperature of the shell TV is material, as the temperature of the shell of TVEL (Tabout) is determined from the expression

< / BR>
where Tabout- temperature membrane fuel rod, TO;

tothe time of precondensation fuel material;

the thickness of the fuel material, m;

C = qv2/(2), deg;

D = qvV2/(2(2Rc(Rc+Lc))2), deg;

qvis the density of heat generation in the fuel material, W/m3;

- thermal conductivity of the fuel material, W/(mgrad);

V - volume of the fuel material, m3;

Rcand Lc- inner radius and length of a fuel rod, respectively, m;

A and b are coefficients depending on the type of the fuel material, A (deg) (m deg1/2/c).

This technical result is achieved by a device for determining the temperature of the shell, of a fuel rod during experimental testing in a nuclear reactor containing the fuel elements consisting of a shell, inside of which is placed with a gap of the fuel material, the calorimeter integral of the heat flux and thermocouple on the end shell of a fuel rod concentric with its axis, is installed with a gap of thin-walled glass, inside of which is placed a fuel material with a thickness that is less than the diameter of the glass, while the gap op where0the size of the gap, m;

Rc- the inner radius of the fuel rod, m;

T - heat of the body, deg;

articlethe thickness of the side wall of the thin-walled cups, m;

TM, aboutthe coefficients of linear expansion of the fuel material and the end shell of a fuel rod, respectively, deg-1.

The height of the thin-walled glass of equal thickness of the fuel material. Thin-walled Cup made of refractory metals such as W, Mo, TA, Re, Mb, or alloys based on them, or from the same material as the face shell of the fuel rod. Thin-walled Cup made zuzelo face shell of a fuel rod. The fuel material is performed with a high density of compounds of plutonium, highly enriched in the isotopes239Ri or(and)241Ri and / or uranium enriched in the isotopes233U or(and)235U.

A proposal to install inside of a fuel rod concentric with its axis on the end shell of Fe thin glass allows you to avoid displacement of the fuel material, made in the form of fuel pellets relative to the axis of the fuel rod and thus contact her with a cylindrical shell of a fuel rod. Fuel tablet is fixed on the end part of the casing of thin-walled glass with a dense the new shell fuel. This allows, in the first approximation, to take the temperature at the end of the fuel pellets in contact with the end portion of the sheath of the fuel element, is equal to the temperature of the shell of TVEL (Tabout), which is taken into account when deriving (2).

Offer to perform a thin-walled glass caused by the need to minimise its effect on the temperature field of the fuel pellet, and hence for the entire experiment as a whole.

The proposal to install a thin-walled glass, with fixed therein a fuel tablet, with a gap corresponding to the relation (3) due to potentially significant differences in coefficients of thermal expansion of the materials of the shell of a fuel rod and fuel pellets. This circumstance can lead to contact of the fuel material and the side wall of thin-walled glass cylindrical portion of the shell of a fuel rod that will cause changes of temperature fields and conditions precondensation fuel pellets (boundary conditions) and thus the error in the determination of Taboutaccording to expression (2).

Offer to perform a thin-walled Cup made of refractory metals such as W, Mo, TA, Re, Nb, and alloys based on them, caused, first of all, their high-temperature Seva shell of a fuel rod and to ensure the compatibility of the material of the glass of the fuel material, carry out a glass from the same material as the face shell of the fuel rod. As one of the options for structural performance of a fuel rod, the end part of the membrane of a fuel rod and the thin glass can be executed in one piece.

The proposal to perform the thickness of the fuel pellets , the smaller its diameter d, is caused, primarily, by the necessity of the presence of small amounts of TM in Fe, which allowed us to use simple mathematical expressions to determine the temperature field in the fuel tablet used in the method and, thus, do not make a big error in the proposed method for the determination of Tabout. Otherwise a detailed calculation of the temperature fields in the TM of TVEL involving complex mathematical apparatus [12], which has greatly complicated the methodology and, thus, the implementation of the method of determination of Tabout.

The proposal to perform the height of the thin-walled glass, equal to the thickness of the fuel pellets, due, primarily, to prevent evaporation of the TM with the side surface of the fuel pellets, which would change the value oftoand would thus error in the method definitionabout.

The proposal to perform toplin is 1Pu and / or uranium enriched in the isotopes233U or(and)235U, is determined by a high cross-section of the division of these isotopes [13] and is caused, primarily, by necessity, experimental testing of fuel elements, to model the desired value of thermal capacity of a fuel rod with a small amount of fuel material in the fuel element.

In Fig.1 shows a structural diagram of the device for determining the cladding of a fuel rod when experimental development in the nuclear reactor at the beginning of the experiment (=0). In Fig.2 shows a structural diagram of the device at the time of completion of precondensation fuel material 3 inside the fuel rod 1 ( =to). In Fig.3 and 4 are diagrams explaining the method.

TVEL 1 includes a casing 2 enclosing the fuel material, made in the form of fuel pellets 3. Fuel tablet 3 is made with a high density of compounds of plutonium, highly enriched in the isotopes 239Pu or(and)241Ri and / or uranium enriched in the isotopes 233U or(and)235U. Fuel tablet 3 is fixed in thin-walled glass 4, which is mounted on the end of the shell 5 concentric with the axis of the fuel rod 1. The thickness of the tablet 3 is less than dealerplay metals, for example, W, Mo, TA, Re, Nb, and alloys based on them or from the same material as the end of the shell 5. Alternatively, the thin glass 4 can be performed zuzelo with the front shell 5. The side wall of the Cup 4 forms a gap 6 with a cylindrical shell 7 of the fuel rod 1. For the temperature control method of the control point at the end of the shell 8 is installed thermocouple 9. For thermionic fuel elements 1 thermocouple 9 is installed inside the switching jumpers 10. The control of the density of heat generation in the fuel rod 1 carries out the calorimeter integral of the heat flow 11. To reduce heat losses from thermal emission of a fuel rod 1 through a switch jumper 10 end of the shell 8 is separated from the internal cavity of the fuel rod 1 system heat shields 12, made from refractory metals such as W, Mo, TA, Re, Nb, and alloys based on them.

The method is implemented and the proposed device operates as follows. Selecting the geometry of the fuel element 1, the material end of the shell 5 and type TM, set on the end of the shell 5 thin 4 cups (made of refractory metals such as W, Mo, TA, Re, Nb, and alloys based on them, or of the same material as the shell 5, or zuzelo shell 5), the side wall katalogowanie (3). After fabrication of the device, as part of a special ampoule or the loopback channel is placed in the cell research reactor. In the process of moving the device when it is placed in the reactor, due to thin-walled glass 4, fixed on the end of the shell 5 concentric with the axis of the fuel rod 1, prevents the displacement of the fuel pellets 3 and is provided with a gap 6. In the process of temperature rise is thermal expansion of the fuel pellet 3 and the shell 2 with the magnitude of the initial gap 6 in view of the possible significant differences in the coefficients of linear expansion of the materials of the fuel pellets 3 (TMand shell 2 (about). Moreover, thermal expansion of the fuel pellets 3 in the radial direction will not have a glass of 4 due to tonkostennoy his side. Gap 6 will remain in effect for condition (3), and, thus, will not violate the conditions under which equation (2). During reactor operation, constant heat capacity, fuel tablet 3 with a thickness that is less than the diameter of the Cup 4 and equal to its height, the division of nuclear fuel with heat release and establishment for each point in time is 3 yrs, having the greatest temperature, the evaporation TM. With the overwhelming flow of TM in the volume of the fuel rod 1 will go with its open end surface, by performing the height of thin-walled glass 4, equal to the thickness of the fuel pellets 3, which prevents the evaporation of TM with the side surface of the tablet 3. Evaporated TM distributed (through condensation) on the inner surface of the shell 2, as shown in Fig.2. Thanks to the system heat shields 12 are reduced leakage of heat through the crosspiece 10, which provides the best conditions for the considered horizontally isothermal surface of the shell 2 and, accordingly, a more uniform thickness of the condensate TM 3. The evaporation TM 3 depends primarily on the type TM, density televideniya in TM 3, the thickness of the fuel pellets 3 and its thermal conductivity. Experiment conduct at constant thermal power of the reactor, measured by the calorimeter 11 heat capacity of the fuel rod 1 (Q) and, knowing the amount of fuel pellets 3 (V), find the density of heat generation qv=Q/V. Due to the small number TM 3 in volume of the fuel rod 1 to simulate the required thermal power of the fuel rod 1 Q fuel pellets 3 perform high density of connections, Ri, highly enriched in the isotopes239RTused only as a temperature reference point. Thermocouple installed on the end of the shell 8 of a fuel rod 1, according to the testimony which to obtain the dependence of TRT= f(), as shown in Fig.3. As the evaporation fuel pellets 3 and redistribution of TM on the inner surface of the shell 2 will change the temperature of the end of the shell 8 and, respectively, the readings of thermocouple 9. Obviously, since time = towhen the process of precondensation will end, thermocouple measurements 9 will not change, which is reflected in Fig. 3. What matters is not the accuracy of thermocouple measurements 9, which is measured with great accuracy, and dynamics of probe 9. Thus, we shall fix the time precondensationtothe fuel material 3. Then for a particular TM 3 from the expression (2) determine the temperature of the sheath of the fuel element.

Let us derive the relation (2).

The flow of molecules TM with an open end surface of the fuel pellets define as the ratio of Meyer [14]

= 0,25 nVa, (4)

where n is the equilibrium concentration of molecules TM inside of a fuel rod and is determined from the relation [15]

PTM= n k T; (5)

vathe average speed of the molecules TM and the/BR> k - Boltzmann constant;

T is the temperature on the open end surface of the fuel pellets;

Ro- universal constant;

M - molecular mass.

Given the exponential dependence of the vapor pressure PTMthe temperature T for a wide class TM [16, 17], we can write

PTM= A* exp(-A/T), (7)

where a and b* are coefficients depending on the type TM.

In the evaporation process TM with an open end surface of the fuel pellets its original thickness and decreases depending on time ( varies from 0 to time =tocorresponding to the completion of the process of precondensation TM in Fe) is equal to x(), and, obviously, the rate of change dx()/d will correspond to the expression

dx()/d = -(TM/TM)(), (8)

where x () is the current thickness of the fuel pellets;

TM- mass molecules TM:

TM- the density of the TM.

The temperature T on the open end surface of the fuel pellets (accept it as a plate with heat sources, cooled on one side) according to [18] and, given the tight contact of the tablet with the butt of glass, for each point in time can be determined from the expression

T() = qv
< / BR>
where the coefficient depends on the type TM and is determined by the expression

B = B*/TM(M/(2R0))1/2. (12)

Transform (11) to the form

< / BR>
where C = qv2/(2), grad. (14)

Transform equation (13), using the variable substitution

y=(1-Tabout/T)1/2. (15)

Where from (15) we obtain

dT=2U Tabout/(1-y2)2dy; (16)

exp(A/T)=exp ((12)/Tabout). (17)

Substituting (16) and (17) into (13), we obtain a differential equation with separated variables

-exp(A (1-y2)/Tabout)/(12)2dy=C1/2B/(Taboutd. (18)

Integrate the left part of the differential equation (18) in y from y(=0) to y( =to), and right from =0 to =to.

The lower limit(0) of the integral according to (9) and (14), bearing in mind that x(0)= will be determined by the expression

u(0)=(/(Tabout+C))1/2. (19)

The upper limit of yto) is determined from the following considerations. In the process of precondensation TM inside of a fuel rod is formed gas Central cavity with isothermal surface at the completion of the process of precondensation, i.e. at =to[19] . Moreover, in the first approximation, it is possible scki of TVEL constant [20]. Hence, knowing the area of the inner surface of the shell of a fuel rod S and the amount of fuel pellets V, we can determine x(to) ratio

xto) = V/S = V/(2Rc(Rc+Lc)). (20)

From (9) and (15), using (20) defined by T(to) and y(to)

T(to) = Tabout+qvx2/(2);

yto) = (D/(Tabout+D))1/2, (21)

where D = qvV2/(2(2Rc(Rc+Lc))2). (22)

Integrating the left part of the differential equation (18) in y from y = 0) to y( =to), and right from = 0 to =to, taking into account (19) and (21), we obtain the expression (2)

< / BR>
Expression (3) is obtained as follows.

To provide clearance between the cylindrical shell of a fuel rod and a side wall of the Cup after placing fuel into the reactor and heating it on T degree must comply with the condition

Rc(1+aaboutT)-d(1+aTMT)/2-article>0, (23)

where Rwiththe inner radius of the fuel rod, m;

T - heat of the body, deg;

TM,aboutthe coefficients of linear expansion TM and end of the sheath of a fuel rod, respectively, deg-1;

d - diameter of the fuel pellet, m;

articlethe thickness of the side wall of the thin-walled cups, m

Designating by0viewnow 0= Rc-(d/2+aarticleand expressing d=2(Rwith-0-article) convert the inequality (23) to equation (3)

0>(TM(Rc-article)-aboutRc)T/(1+ATMT).

The value of T in (3) at the first stages of testing shall be taken of the expected prediction of thermal state of the elements that make up the core of the research reactor, which is known [21]. At subsequent stages of the loopback tests the value of T can be refined by taking into account knowledge of Taboutobtained from previous experiments on the proposed method and the device.

As an example, fuel elements, characteristics and materials which are typical for high-temperature thermionic fuel elements [22], experience in the EHS. Consider how to define the cladding of a fuel rod when experimental development in the nuclear reactor and the device for its realization, where the TM will take uranium dioxide (highly enriched in the isotope235U), made in the form of sintered dense (density of not lower than 96% of theoretical) of the fuel pellet thickness =510-3m and mounted in thin-walled glass. The wall thickness of the Cup will takearticle=10-4m and a height of 5 to 10-3m Stack is>6 10-3m and length lc=50 10-3m, as shown in Fig.1.

For TM and the cladding material of the fuel rod will accept the following characteristics:

TM= or 10.60-61/castle [23];about= 6,810-61/castle [24];

TM= 10,9710-3kg/m3[23]; = 2.5 W/(mgrad) [25].

Determine the magnitude of the gap 0between the glass and the cladding of a fuel rod according to equation (3), taking T =K

< / BR>
where0>3,6310-5m

On the basis of the found relation (3), we assume the diameter of the fuel pellets (d=10 11-3m

Find the coefficients a, b*, b, C and D. Convert the equation of equilibrium between the steam and the adsorbed phase stoichiometric uranium dioxide, is given in [26]

lgP[mm RT.article] = -32258/T+12,183,

to the form (7) with regard to the International system of units

P[N/m2]=2,027 1014exp(-74277/T)

where we find the values of coefficients A=74277 hail and*=2,027 1014N/m2. Where from (12) defined IN=1,32 109m deg1/2/s constant thermal power of the reactor according to the testimony of the calorimeter will take heat capacity of a fuel rod Q=237,5 W and, knowing the amount of fuel pellets V=d2/4=4,75 10-7m3find the density of heat generation qv=Q/V=5 103W/m3about
=f(to), as shown in Fig.4. Put that recorded timeto= 3 103when thermocouple measurements do not change, taking advantage of the dependence of TRT= f(), as shown in Fig.3. Using the schedule according to Tabout=f(to) (see Fig.4) and knowingtodefined Tabout=2100K.

As can be seen from the calculation example, the error in measurement proposed in this method and device time precondensation TMto100% gives an error in the definition of Taboutonly ~2%. Such a small sensitivity of the proposed method and devices to significant errors in measurementtodue to the exponential dependence of Taboutfromtoas is evident from (2) and Fig. 4. Especially effective the proposed method and the device in experimental development of high-temperature fuel elements and, in particular, thermal emission, where the high temperature membrane fuel elements and where other methods of determining the cladding of a fuel rod is ineffective. In addition, experimental studies of fuel than necessary, rods, distinguished by the geometry and materials used, to record for each of the i-th TVEL its valueto, qvand, respectively, Tabout.

Thus, the proposed method of determining the cladding of a fuel rod during experimental testing in a nuclear reactor and a device implementing the method, with high precision:

- reduces the number of monitored during the experiment parameters and thermophysical characteristics of TM and Fe;

- applicable for a wide class of fuel cladding and fuel materials.

LITERATURE

1. Century Century Sinyavsky. Methods of determining the characteristics of thermionic fuel elements. - M.: Energoatomizdat, 1990, S. 73.

2. A., Samoilov. Fuel elements of nuclear reactors. - M.: Energoatomizdat, 1985, S. 150.

3. [1], S. 77, 78, 79.

4. [1], S. 80, 81.

5. Sinyavsky Century. Century. and other Design and testing of thermionic fuel elements. - M.: Atomizdat, 1981, S. 7.

6. [1], S. 81, 86.

7. Pyatnitsky A. P. and others volt-ampere characteristics of thermionic converters. - M.: Atomizdat, 1967.

8. [1], S. 79, 80.

9. Holland, J. , Yats M., Kay J. The reactor and out-of-pile endurance testing of thermal emission p.With.Mosevich. - M.: Atomizdat, 1971, S. 119-130.

10. [1], S. 78, 50, 51, 178.

11. Simovski A. S. and other Fuel elements of nuclear reactors. Ed. 2-E. - M.: Atomizdat, 1966, S. 473.

12. Kornilov C. A. and other Modeling heat and mass transfer in the core thermionic fuel elements. - Atomic energy, 1982, T. 53, vol.2, S. 74-76.

13. Handbook of nuclear physics. Ed. by Acad. L. A. Artsimovich. - M.: State publishing house of physical and mathematical literature, 1963, S. 266.

14. C. Desman. Scientific foundations of vacuum technique. - M.: Mir, 1964, S. 23.

15. [14], S. 12, 18.

16. Kotelnikov R. B. and other high-Temperature nuclear fuel. Ed. 2-E. - M.: Atomizdat, 1978, S. 40.

17. Gorban Y. A. and others Research fumes dioxide and carbides of uranium. Nuclear power, 1967, I. 22, vol.6, S. 465-467.

18. Simovski A. S. and other Fuel elements of nuclear reactors. - M.: Atomizdat, 1962, S. 355.

19. Kornilov C. A. and other Method of calculation of the temperature fields of the fuel core thermal emission electricity generating element. - Atomic energy, 1980, T. 49, vol.6, S. 393-394.

20. Legalizes Yu, and other high-temperature Behavior of nuclear fuel during irradiation. - M.: Energoatomizdat, 1987, S. 116.

21. [is CNIC Ed. A. I. Tumanov and K. I. Portnoy. - M.: Mashinostroenie, 1967, S. 109.

25. [16], S. 103.

26. Gorban Y. A. and others Research fumes dioxide and carbides of uranium. Nuclear power, 1967, I. 22, vol.6, S. 465-467.

27. Piskunov N. With. Differential and integral calculus for technical colleges. - M.: Fizmatgiz, 1963, S. 408.

1. The method of determining the cladding of a fuel rod during experimental testing in a nuclear reactor, including the measurement of the density of heat generation in the fuel material, the evaluation of the cladding of a fuel rod, characterized in that the constant thermal power of the nuclear reactor is fixed time precondensation fuel material, and the temperature of the shell of TVEL (Tabout) is determined from the expression

< / BR>
where Tabout- temperature membrane fuel rod, TO;

tothe time of precondensation fuel material;

the thickness of the fuel material, m;

C = qv2/(2), deg;

D = qvV2/(2(2 Rwith(Rc+Lc))2), deg;

qvis the density of heat generation in the fuel material, W/m3;

- thermal conductivity of the fuel material, W/(mgrad);

V - volume of the fuel material, m3;

Rwithand Lcin the t of the type of fuel material.

2. A device for determining the cladding of a fuel rod during experimental testing in a nuclear reactor containing the fuel elements consisting of a shell, inside of which is placed with a gap of the fuel material, the calorimeter integral of the heat flux and thermocouple, characterized in that on the end shell of a fuel rod concentric with its axis set with a gap of thin-walled glass, inside of which is placed a fuel material of a thickness less than the diameter of the glass, thus the value of the gap is determined by the ratio

< / BR>
where0the size of the gap, m;

Rcthe inner radius of the fuel rod, m;

T - heat of the body, deg;

articlethe thickness of the side wall of the thin-walled cups, m;

TM,aboutthe coefficients of linear expansion of the fuel material and the end shell of a fuel rod, respectively, deg-1.

3. The device according to p. 2, characterized in that the height of the thin-walled glass of equal thickness of the fuel material.

4. The device according to p. 2, characterized in that the thin-walled Cup made of refractory metals such as W, Mo, TA, Re, Nb, and alloys based on them, or from the same material as the face shell of the fuel element.

5. The device according to p. 2, otlichayushchayasya fact, what fuel material perform high density of compounds of plutonium, highly enriched in the isotopes239Pu or(and)241Ri and / or uranium enriched in the isotopes233U or(and)235U.

 

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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: power industry.

SUBSTANCE: method for determining error of in-core temperature measurements consists in heating of a sensitive element of a temperature sensor by passing current pulses on two different levels of reactor power. Pulses are supplied in series, at least two pulses with different durations and/or current values. Duration of each pulse exceeds the value of inertia constant. Strength of pulses, temperature of the temperature sensor prior to pulse supply and values of temperature amplitude are recorded immediately after pulses are switched off. Error of temperature measurements is calculated by the formula.

EFFECT: possible determination of a correction for measured temperature on the reactor in operation at any stage of campaign with different fuel loads, and therefore, improvement of accuracy of in-core control of coolant temperature.

3 cl, 1 dwg

FIELD: nuclear power engineering; fuel rods for water-moderated water-cooled reactors.

SUBSTANCE: proposed fuel rod designed for use in water-cooled water-moderated power reactors such as type VVER-1000 reactor has fuel core disposed in cylindrical can. Outer diameter of fuel rod is chosen between 7.00 . 10-3 and 8.79 . 10-3m and fuel core diameter is between 5.82 . 10-3 and 7.32 . 10-3m and mass, between 0.93 and 1.52 kg, fuel core to fuel rod length ratio being between 0.9145 and 0.9483.

EFFECT: reduced linear heat loads and fuel rod depressurization probability, enlarged variation range of reactor power, optimal fuel utilization.

7 cl, 3 dwg

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; manufacture of fuel elements for nuclear reactors.

SUBSTANCE: process line primarily used for manufacturing fuel elements for VVER-1000 and VVER-440 reactors has charged can weighing device built integral with can-and-plug assembly weighing device that determines net weight of charged can by internal components, box holding devices for discharging fuel pellets from rejected fuel element, destructive testing of helium pressure within can, and preparing specimens for metallographic inspection.

EFFECT: enlarged functional capabilities of line, improved quality of fuel elements, enhanced yield.

1 cl, 9 dwg

FIELD: nuclear engineering; manufacture of plate-type fuel elements.

SUBSTANCE: core for three-layer assembly that has sleeve, circular core, and plugs is provided with longitudinal bonds made of sleeve material and three-layer tube obtained upon joint hot extrusion and drawing is cut along bonds; segments obtained in the process are drawn through slit die.

EFFECT: reduced labor consumption due to reduced number of pre-heat rolling operations.

1 cl, 5 dwg

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