• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
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    • 专利摘要:
    1454618 Fuel elements ATOMENERGI AB 30 Jan 1974 [2 Feb 1973] 04389/74 Heading G6C A fuel element for use in a nuclear power reactor comprises a plurality of ceramic fuel pellets 3 housed within a cylindrical cladding tube 1 provided on its inner surface with at least eight longitudinal ribs 5, a cold assembly gap of at least the radial extent of a rib existing between the pellets 3 and the inner surface. The fuel pellets are for example of UO 2 enriched to about 2À5% and sintered to approx. 95% theoretical density using a sintering atmosphere of H 2 at about 1700‹ C., and the cladding tube 1 may be of Zircaloy or stainless steel with an oxide film coating on its inner surface serving as a protection from chemical attack by fission gases. The radial height of the ribs 5 is at most about 0À1 mm., preferably at most about 0À05 mm., and at least 0À005 mm. The annular gap between the fuel pellets 3 and the cladding tube 1 (excluding the ribs 5) in the cold is in the range from about the radial height of the elements 5 to about 0À15 mm. There are at least eight ribs 5 evenly distributed over the inside surface of the cladding tube 1, with a particularly useful number of ribs being in the range from 16 to 32. The ribs may have in cross-section a trapezoidal shape. Alternatively they may have the shape of a circle segment formed between the circular periphery of the cladding tube bore and a chord thereof (Fig. 4, not shown) or a generally triangular shape with a rounded peak (Fig. 5, not shown). Preferably the ribs 5 are made integral with the cladding tube 1 as part of the ordinary tube manufacture, for instance in pilger step rolling or drawing operations, using a mandrel machined to conform with the shape of the desired tube bore cross-section. Cracks such as may occur in a fuel pellet 3 due to temperature differences are shown in Fig. 2, which cracks are widened at a power increase. With the ribs 5, however, the crack widening cannot result in local stress peaks and deformation in the opposite regions of the cladding tube 1 and the movement is merely transmitted by the friction forces at the separate ribs 5 as a general stretching of the whole tube section. Between the end surfaces of the fuel pellets 3, sharp discontinuities or protruding small platforms 9 are formed in the spacing elements 5 and each pellet therefore remains fixed in axial position and is prevented from moving axially relative to the cladding tube 1.
    公开号:SU841066A1
    申请号:SU742005269
    申请日:1974-02-01
    公开日:1981-06-23
    发明作者:Хилдинг Могард Йохан
    申请人:Актиеболагет Атомэнерги (Фирма)；
    IPC主号:
    专利说明:

    This invention relates to Kerg heat generating elements (TVEL) of briquette, the type that is currently used in power engineering (nuclear reactors. Constructive design of a fuel cell of a nuclear reactor is known, including a casing, plugs and pellets located inside the casing (briquettes) with fuel | l1. The disadvantage of this solution is the need to fulfill: the gap between the casing and the fuel briquettes, which significantly worsens the heat transfer from the fuel briquette column, and therefore worsens The efficiency of such an element. Also known is the design of a heat generating element of a nuclear power reactor containing an elongated tubular casing and cylindrical solids made of sintered oxide and forming a column of fuel briquettes in contact with supporting elements inside the casing. The known heat generating element is designed for reactors with the reproduction of fuel and the construction of supporting elements inside the casing is determined by the fraction of maintaining the necessary physical conditions inside the heat generating element and in the active zone as a whole, and is associated with the need to create a reproduction zone of 2 J. The disadvantage of this design is the reduction of safety due to the possible mechanical interaction between the fuel briquette column and the casing during operation. There is a radial clearance of about 0.3 mm between the casing and a plurality of cylindrical bodies, which is completely unacceptable given the heat transfer from the fuel to the casing. In addition, a gap of about 0.3 mm inevitably causes a rise in temperature in kergsch fuel to a large value and the resulting heating leads to the melting of a nuclear fuel with a resulting serious risk of radioactive contamination. Damage to TVELs that have the appearance of small TpeitoHs occur. protective casing caused by a strong mechanical interaction between the fuel briquettes and the casing. It is also necessary to take into account another type of damage, which appears as a local separation (along the axis) of the inner long column (stack) of fuel briquettes, as a result of which this column is divided into two parts. And the gap with these parts can reach several centimeters. The purpose of the invention is to increase reliability by reducing the mechanical interaction between a column of fuel briquettes and housing 4 during operation. This aim is achieved in that the energy element teplovadel khtsom nuclear reactor comprising an elongated tubular casing, coaxially polozhonnye races in the housing cylindrical solid body made of a sintered oxide and image otsie post fuel briketrv, soprikasayuschiys to the support elements inside the tubular kozhuh.imeet by mei & nearer, three uniformly distributed supporting elements, made in the form of profiled longitudinal ribs with a height of not more than 0.05 mm, arranged along the inner cylindrical surface The surface of the casing, with the edges in transverse section, is made in the form of a circular segment formed by the inner circumference of the casing and the chord, either in the form of a trapezium or in the form of a triangle with a rounded protrusion. ; FIG. Figure 1 shows the fuel element design for a nuclear water reactor, a longitudinal section; in FIG. 2, the same cross section (enlarged Ma-scale), fig. 3, 4 and 5 - details of various applications of the tubular protective casing for fuel cells; in fig. 6 and 7 on an enlarged scale, the conditions operating around the interface of the two fuel briquettes in the fuel cell structure. The tubular protective casing 1 is made of zirconium alloy (in most cases, of circulating metal), and both end plugs 2 and 3 are made of the same alloy tube. The end plugs are provided with longitudinally protrusions with pins 4 and 5, respectively. These pins 4 and 5 serve to hold the FATL inside the reactor in a fixed position. A column of briquettes b is installed inside casing 1 with a certain annular “(radial) gap, the value of which lies within 0.07–0.15 km with a typical tolerance of 0.05 mm (dimensions related to the annular gap between the casing and fuel cells). briquettes are given for the cold state of the fuel elements and without taking into account the size of the support lugs on the inner surface of the casing). Such thin and precisely maintained dimensions of the gap are required in order to minimize the drop in temperature during the operation of the fuel element and at the same time to avoid meaning. mechanical interaction between the housing and the briquettes, which in a fuel element of a conventional design is a potential source of deterioration of technical characteristics. During the operation of the fuel element, the gap decreases to some extent, depending on the actual heat transfer and the degree of fuel burn-up. On the surface of the casing, annular hillocks occur, located in the junction of neighboring briquettes, the occurrence of these hillocks is due to the mechanical interaction between the casing and briquette and shape distortion of the latter (they take the form of sand clocks) :. To improve the heat transfer in the annular gap, helium gas is introduced into the internal volume of the fuel element. TVELs designed for pressurized water reactors use pressurized helium in order to prevent plastic deformation of the protective casing during the operation of the fuel elements. As can be seen from FIG. 1, a free volume 7 is left inside the fuel element in which, due to the release of gaseous decomposition products and, due to the excess amount introduced into the fuel element, the gels create an increased pressure. A coil spring 8 is disposed in this free space and acts on the column of fuel briquettes. OcHOBHbovi purpose of the coil spring 8 is to hold the fuel briquettes in place during transportation and transportation of the fuel element, but it should be noted that this spring is not able to prevent the mutual displacement of the briquettes along the longitudinal axis of the fuel element during its operation. The protruding parts of the supporting elements located on the inner surface of the tubular protective casing (it is preferable to make them at the same time as the casing is convenient to give the shape of mutually parallel edges 9 running in axial direction, as shown for - the design (Fig. 2). , made in the form of such axial (longitudinal) ribs, run along the fuel element along the entire length of the protective casing, at least along that part of the central opening of the casing, which is occupied by a column of fuel briquettes. The invention also encompasses other forms of supporting elements, for example supporting elements, imitating the form of a large number of growths protruding into the fuel element, suitably arranged one against the other. The actual shape of the inner surface of the protective cover in each individual case can be adapted to several possible fuel elements in This time in production.
    The height of the supporting elements (calculated along the TVEL radius) should be no more than a normal annular gap (in a cold state), for example, no more than 0.1 mm, and preferably no more than 0.05 mm, in order to obtain an acceptable temperature drop in the annular the gap remaining when the TVEL operates at full capacity. Practically, the lower limit of the height of the supporting element is approximately 0.005 mm. The presence of supporting elements makes it possible to substantially reduce the size of the usual annular gap in cold fuel elements, for example, twice and even less. Thus, due to the introduction of the supporting elements, some improvement in heat transfer inside the fuel element can be achieved. Further, from the point of view of heat transfer and distribution of mechanical forces between parts of the fuel elements, the shape of the supporting elements is important. The shape of each longitudinal support element in the cross section may be different, as can be seen from FIG. 2-5. So in FIG. 2 shows longitudinal support elements 9 having a trapezoidal shape in cross section. FIG. 5 shows in more detail, on an enlarged scale, the supporting elements of FIG. 2, where each support element 9 is rounded near its base and flat-cut at the top (closer to the middle of the cross-section of the fuel element).
    FIG. 4 shows, on an enlarged scale, a detail of the tubular protective casing 1. | In the proposed design, the longitudinal support elements 9 have a cross-sectional shape corresponding to a circular segment formed by the circular inner surface of the tubular 1 and chord C, which is drawn inside a circle corresponding to the drilling of the tubular casing. This design is of particular interest due to the fact that it allows to realize small tolerances on the height of the ribs 9 (along the TVEL radius), since the latter is in a certain geometrical relation with the width of the edge around the circumference and this width is much greater than the height of the edge, and therefore in manufacturing tubular casing it can be held out with great precision. This means that the cross-sectional shape of the ribs 9 shown in FIG. 4, is especially useful for small (less than 0.02 mm) values of rib heights.
    FIG. 5 shows a structure in which the support elements 9 located on the same tubular casing have different forgings of cross section. Each third support element 9 has a relatively small width and a large height, as it is weakly resistant to deformation, and therefore. provides the best grip
    fuel briquette according to p1; single axis. Intermediate support elements 9 have a relatively large width and small height, so that they better resist deformation and provide increased ne from heat briquettes of nuclear fuel to the protective cover.
    As seen from the black hedgehogs | representing the cross-sections, the supporting elements have Vrel bases protrusions corresponding to about half the thickness of the wall of the casing, but here to-. Rustyma and other sizes. The contact of the ribs with the adjacent fuel briquettes is carried out along lines of different length, depending on the shape of the rib and on the degree of its deformation during the operation of the fuel element. -.
    The number of supporting elements, imekhtsihs on the inner surface of the protective casing, vary within fairly wide limits. However, for the longitudinal ribs shown in FIG. 2-6, practically the lower limit of their number is three, since this is the minimum number of ribs that ensures good centering of the fuel briquettes inside the protective casing. For this minimum number, a uniform distribution of the ribs around the inner surface of the protective casing is implied. Depending on the method of obtaining the ribs, their height, cross-section, the number of edges may be different.
    Between the briquettes b, the formation of unevenness 10 in the space 11 in the area of the notches 12 in the briquettes is possible ..
    To optimize heat transfer between nuclear fuel and protective hood. It is advisable not only to work with the smallest possible annular gap, but also to provide some contact area between the supporting ribs and fuel briquettes. In this connection, it was found that the width (around the circumference J of the contact surface between each edge and briquette ... should be at least about O, 1mm. It should be noted that this is only the desired minimum requirement for the value of the contact surface between the edge and briquette, and During the operation of the fuel elements, this number may be much larger.
    权利要求:
    Claims (2)
    [1]
    The supporting elements during the operation of the fuel element on the mechanical interaction between the fuel briquettes and the internal shell in such a way that damage to the fuel elements is prevented in several directions. Especially important are the advantages of supporting elements (edges oriented parallel to the longitudinal axis of TVEL, so that TVEL designs with such bearing elements are preferable. Further, constructions of this type are considered to be subtle. Therefore, the effect of onopHEdx elements on the performance characteristics of TVEL, due to The occurrence of mechanical contact between fuel briquettes and a protective casing & a process of increasing thermal power introduced by a fuel element. With such a gap, The cycle now appears at a lower power level than this smolders a place for a fuel element with a protective casing without internal support elements {gaskets; the greater the height of the support elements, the lower the thermal power at which contact occurs. In this case, the height of the reference elements elements are selected "in such a way that mechanical contact (taking into account some plastic deformation of the supporting elements, occurs at the rated operating power. In this connection, it is necessary to emphasize that the usual fuel elements for water reactors are designed in such a way that between fuel briquettes and a small mechanical action takes place. As can be seen from FIG. 6, the support element 9 is subjected in the cross-section to some limited amount of plastic deformation due to the fact that the pressure acting on the support element is initially. surpasses compressive strength inherent in its material. As the support element is increasingly compressed in its cross section, its compressive strength increases rapidly, so that further compression is difficult. From FIG. 7, an illustration of a longitudinal section of the tubular protective casing 1 at the points of contact between adjacent briquettes shows how the longitudinal support element 9 is deformed under the influence of each fuel briquette, resulting in an unevenness 10 in the space 11 between the briquettes 64 the ends as shown in FIG. 7, in order to obtain such a shape of the ends or irregularities 10, so as to prevent the relative displacement of the briquette and the protective casing along the longitudinal axis. Squeezing the support element 9 in the forward direction receives a certain reflection in the form of briquettes 6, externally input with an hourglass outline. Thus, the supporting elements prevent local direct contact between the inner surface of the protective casing and the sharp edges of the briquettes at their ends. Now let us consider the influence of the supporting elements in such a situation, when the mechanical interaction that occurs when a crack in a strong ceramic broom-plate appears in the event of a sudden increase in the output power leads to the destruction of the protective casing. During operation of the reactor, the fuel briquettes 6 within the HDTV are subject to some cracking due to the influence of temperature differences within the briquette. A typical picture may be the formation of radial cracks of the overall cross section of briquette 6, shown in FIG. 2 In the longitudinal section of the same briquette, transverse cracks are observed, but in a smaller number. During the operation of the reactor, all these cracks are somewhat widened towards the outside of the cross section of the fuel element. As the emitted power increases, these existing cracks in the briquette widen further and new cracks may form. Under such conditions, and in the absence of supporting elements, disturbances occur in the structure of the protective casing material in those voltage-prone areas that are opposite to the cracks opened in the briquette in the zone of its mechanical contact with the casing. The presence of support elements drastically changes the mechanism of formation of damage in the protective casing associated with radial cracks that affect the surface of the X-shaped casing. It should be noted that the main part of the cracks in the briquette is formed in the areas between the widely spaced supporting elements 9, where there is no contact between the briquette and the casing or this contact is negligible (see Fig. 2j. Therefore, the expansion of the cracks does not cause local overvoltages and deformation of the underlying opposite to these cracks of sections of the protective casing, and due to the frictional forces acting on the individual supporting elements 9, the entire cross section of the protective casing lying between these supporting elements is stretched. of this type of material is absorbed by the material, the greater the distance at which the stretch acts in relation to the width of the crack, i.e. the further the support elements are separated from each other 9. Next, the cracks in the briquette material located between the support elements , it is much easier to undergo further firing than single cracks, KOTOF ": i.e. located in the contact zone with supporting elements. To expand the latter, it is necessary not only to overcome the deformation resistance of the casing material, but also resistance due to rennego a friction material preform. Turning now to the consideration of the pattern of transverse cracks in ceramic fuel briquettes, it can be noted that these cracks, in the absence of supporting elements, usually do not cause damage to the protective casing material as the output increases. The reason for this, in all likelihood, is the fact that the expansion of the cracks in the briquette is at the same time caused by the changed modified form of the briquette, which leads to the fact that it takes the form of an hourglass. Therefore, in this case, it observes with a strong resistance to destructive forces, which are usually transmitted to limited areas of the protective casing, as a result of similar local relative displacements, accompanied by mechanical interaction between the briquette and the casing, and therefore, when using a design with support elements, the damage to the casing will be small or not at all. This means that other phenomena of a similar nature, related to mechanical interactions of this type, such as fatigue and corrosion due to overvoltages, are similarly affected. With regard to other types of damage caused by relative periodic movements of the briquette and protective casing along the longitudinal axis during reactor operation, namely the formation of longitudinal cracks in briquettes and an abnormal increase in the length of the briquette column due to swelling, the useful function of the support elements appears the easiest way. During the first increase in the power output to such a level at which mechanical contact between briquettes and supporting elements is achieved, the latter are to some extent compressed in height, and especially at points along the briquettes themselves (this has already been noted above. At the same time, intermediate the areas of the supporting elements at the points of contact between the briquettes remain almost intact or even slightly increase in height. Thus, the interfacing surfaces of the briquettes on the supporting elements form areas There are large unevenness (Fig. 7) or protruding small planes. Therefore, each individual briquette remains fixed in the direction of its direction and its displacement relative to the protective casing is excluded. Thus, fuel briquettes do not contribute to the appearance of defects of the type that previously It was rtnesened due to self-consolidation or spontaneous growth of the briquette material, while at the same time the swelling of the briquette material was excluded. With briquettes fixed along the longitudinal axis by the method described above, an increase in power output leads to the fact that from each individual briquette there is an extension of the casing in the axial direction of the mechanism mentioned earlier by non-flat ones by their flat platforms on the supporting elements, and the extension is evenly distributed along the entire length of the protective casing. All the foregoing contributes to the safety of operation of the heat gap of an element. 1. Heat-generating element of an energy-generating nuclear reactor, comprising an elongated tubular casing, cylindrical solid bodies coaxially arranged in a goat dry, made of sintered oxide and forming a column of fuel briquettes, in contact with supporting elements inside the casing, with a pattern increase reliability by reducing the mechanical interaction between the fuel briquette column and the casing during operation, the tubular casing has at least three evenly distributed Single supporting elements, made in the form of profiled longitudinal ribs with a height of not more than 0.05 mm, located along the inner cylindrical surface of the casing. 2. The element according to claim 1, characterized in that the ribs in the cross section are made in the form of a circular segment formed by the inner circumference of the protective casing and the chord. 3. An element according to claim 1, characterized in that the ribs in the cross section are made in the form of a trapezium. . 4. The element according to claim 1, characterized by the fact that the ribs in the cross section are made in the form of a triangle with a rounded protrusion. Sources of information taken into account in the examination 1.Kramerov A.Ya. Nuclear reactor design issues. M., Atomizdat, 1971, p. 137, fig. 7.1.
    [2]
    2. The patent of England 1233689, cl. G b C publish. 1970.
    Ut.f
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    同族专利:
    公开号 | 公开日
    GB1454618A|1976-11-03|
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    FR2216649A1|1974-08-30|
    BE894900Q|1983-03-01|
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    DE2404085C3|1980-03-06|
    JPS5542357B2|1980-10-30|
    DE2404085A1|1974-08-08|
    SE383223B|1976-03-01|
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    RU2615961C1|2015-11-26|2017-04-11|Российская Федерация, от имени которой выступает Государственная корпорация по атомной энергии "Росатом"|Assembly of welded joint of fuel element jacket with plug made of high-chromium steel |
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    SE7301524A|SE383223B|1973-02-02|1973-02-02|NUCLEAR FUEL ELEMENT FOR POWER REACTORS.|
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