GB1604443A - Nuclear-reactor calandria assembly - Google Patents
Nuclear-reactor calandria assembly Download PDFInfo
- Publication number
- GB1604443A GB1604443A GB40716/77A GB4071677A GB1604443A GB 1604443 A GB1604443 A GB 1604443A GB 40716/77 A GB40716/77 A GB 40716/77A GB 4071677 A GB4071677 A GB 4071677A GB 1604443 A GB1604443 A GB 1604443A
- Authority
- GB
- United Kingdom
- Prior art keywords
- tube
- tubes
- regions
- wall thickness
- calandria assembly
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000000463 material Substances 0.000 claims description 20
- 230000002093 peripheral effect Effects 0.000 claims description 9
- 230000009172 bursting Effects 0.000 claims description 8
- 238000003754 machining Methods 0.000 claims description 8
- 230000000694 effects Effects 0.000 claims description 7
- 238000000034 method Methods 0.000 claims description 7
- 230000004323 axial length Effects 0.000 claims description 6
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 5
- 239000007788 liquid Substances 0.000 claims description 5
- 239000012779 reinforcing material Substances 0.000 claims description 5
- 229910052726 zirconium Inorganic materials 0.000 claims description 5
- 230000001186 cumulative effect Effects 0.000 claims description 4
- 239000003758 nuclear fuel Substances 0.000 claims description 4
- 230000034373 developmental growth involved in morphogenesis Effects 0.000 claims description 3
- 238000010521 absorption reaction Methods 0.000 claims description 2
- 230000008859 change Effects 0.000 claims description 2
- 238000001816 cooling Methods 0.000 claims description 2
- 230000008569 process Effects 0.000 claims description 2
- 230000009467 reduction Effects 0.000 claims description 2
- 230000002441 reversible effect Effects 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims description 2
- XLYOFNOQVPJJNP-ZSJDYOACSA-N Heavy water Chemical compound [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 description 4
- 230000008901 benefit Effects 0.000 description 2
- 239000002826 coolant Substances 0.000 description 2
- 230000012010 growth Effects 0.000 description 2
- 230000013011 mating Effects 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 230000003466 anti-cipated effect Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 230000004044 response Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C1/00—Reactor types
- G21C1/04—Thermal reactors ; Epithermal reactors
- G21C1/06—Heterogeneous reactors, i.e. in which fuel and moderator are separated
- G21C1/14—Heterogeneous reactors, i.e. in which fuel and moderator are separated moderator being substantially not pressurised, e.g. swimming-pool reactor
- G21C1/16—Heterogeneous reactors, i.e. in which fuel and moderator are separated moderator being substantially not pressurised, e.g. swimming-pool reactor moderator and coolant being different or separated, e.g. sodium-graphite reactor, sodium-heavy water reactor or organic coolant-heavy water reactor
- G21C1/18—Heterogeneous reactors, i.e. in which fuel and moderator are separated moderator being substantially not pressurised, e.g. swimming-pool reactor moderator and coolant being different or separated, e.g. sodium-graphite reactor, sodium-heavy water reactor or organic coolant-heavy water reactor coolant being pressurised
- G21C1/20—Heterogeneous reactors, i.e. in which fuel and moderator are separated moderator being substantially not pressurised, e.g. swimming-pool reactor moderator and coolant being different or separated, e.g. sodium-graphite reactor, sodium-heavy water reactor or organic coolant-heavy water reactor coolant being pressurised moderator being liquid, e.g. pressure-tube reactor
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Monitoring And Testing Of Nuclear Reactors (AREA)
- Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
Description
(54) NUCLEAR-REACTOR CALANDRIA ASSEMBLY
(71) We, NUCLEAR POWER COMPANY
LIMITED, of 1 Stanhope Gate, London WlA 1EH, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a calandria assembly of the kind provided in certain nuclear reactors for containing heavy water or other liquid moderator material of the reactor, such an assembly comprising a plurality of tubes which extend in generally parallel relationship between two tube plates which, with a peripheral wall which is secured to them, enclose a space through which the tubes extend, each tube mating with a respective aperture of each tube plate and being there secured to the respective tube plate.
In such a calandria assembly, actual or potential unequal changes of length of tubes and of the peripheral wall, such as unequal irradiation growth due to non-uniform irradiation by fast neutrons, or even only differential thermal expansion due to non-uniform temperature distribution over the tubes, produces axially directed forces both in the tubes and in the tube plates and peripheral wall unless allowance is made for the effect. It has been common practice, to that end, to provide a non-rigid union between each tube and at least one of the tube plates between which it extends, but that prevents advantage being taken of the full structural strength which rigid unions could confer on the assembly of tubes and tube plates and peripheral wall,
It is an object of the invention to provide a nuclear-reactor liquid-moderator calandria assembly in which each of the tubes is rigidly united with both of the tube plates and the tubes are such as to absorb in themselves at least a major part of such potential differen- tial changes in tube length as are to be expected and thereby reduce the magnitudes of axial forces generated in the tubes.
This object of the invention is achieved by providing that the tube walls are of nonuniform wall thickness, comprising regions of lesser wall thickness, which absorb potential differential changes in tube length with the generation of only relatively small axial forces, and regions of greater wall thickness which confer adequate structural strength on the tubes.
Accordingly, the invention provides a nuclear-reactor liquid-moderator calandria assembly comprising two tube plates, spaced apart from each other and each formed with a plurality of tube-receiving apertures, a plurality of tubes extending in generally mutually parallel relationship between the two tube plates, and a peripheral wall secured to the tube plates and enclosing therewith a space through which the said tubes extend between the tube plates, wherein each tube mates with a respective aperture of each tube plate and is there rigidly secured to the respective tube plate, and the tubes have walls which are of nonuniform wall thickness and comprise regions of greater wall thickness separated from one another in the axial direction by regions of lesser wall thickness.
In cases in which the designed conditions of use of the calandria assembly, which are such as to generate potential changes in tube length, are such as also to encourage creep of the tube material when under stress, advantage may be taken of that fact when designing a calandria assembly according to the invention.
In certain preferred embodiments of the invention, the tubes of the assembly may be formed with axially alternating cylindrical regions of greater and lesser wall thickness. It is also within the scope of the invention to form a tube with one or more helical grooves, of suitable pitch and width, at which the tube wall thickness is accordingly reduced.
The invention is disclosed in more detailed fashion below, with reference to the accompanying drawings, in which: Figure 1 is a fragmentary and diagrammatic sectional view through a nuclear-reactor calandria assembly, showing a peripheral wall and tubes and tube plates thereof;
Figure 2 is a fragmentary sectional view of a wall of a tube, formed with integral stiffening rings, of a calandria assembly as shown in Figure I and constituting a first embodiment of the invention; and
Figure 3 is a fragmentary sectional view of a wall of a tube, provided with non-integral stiffening rings, of a calandria assembly as shown in Figure 1 and constituting a second embodiment of the invention.
The calandria assembly shown in Figure I comprises open-ended tubes 11 which extend parallel with one another between two tube plates 12 and 13, the two ends of each tube 11 mating with and being rigidly secured each in a respective aperture 14 of one of the tube plates in sealing relationship therewith. The tube plates are also secured at their edges to a peripheral wall 15 of the assembly, in sealing relationship with the wall so as to enclose therewith a space 16 through which the tubes 11 extend and which in use of the calandria may be filled with a reactor moderator liquid which then surrounds the tubes.
In one preferred construction of a calandria assembly embodying the invention and generally as shown in Figure 1, the tubes 11 are formed as shown in Figure 2; that is, each tube 11 has a smoothly cylindrical external surface 17 but internally is formed with axially-spaced integral stiffening rings 18, so that the tube 11 has axially alternating cylindrical regions 19 and 20 of, respectively, greater and lesser wall thicknesses x and y extending over axial lengths a and b, respectively, of the tube. The wall-thickness pattern thus repeats with a pitch c where c = a + b.
In use of the calandria shown in Figure 1, with tubes as shown in Figure 2, in a nuclear reactor, its space 16 will be filled with a liquid moderator such as heavy water and its tubes 11 will constitute passages through the moderator to accommodate pressure tubes (not shown) of the reactor, these pressure tubes containing nuclear fuel and a flow of coolant therefor. The moderator in the space 16, whose function is to promote the nuclear reaction by moderating to thermal velocities the neutrons emitted by the fuel, may be under a pressure of some 9 bars, and the tubes 11 must be of adequate strength to withstand that pressure (which is an external pressure so far as the tubes 11 are concerned). Also, the coolant flowing within the reactor pressure tubes will normally be under pressure, and any failure of the pressure tubes to contain that pressure will result in that pressure being applied to the tubes 11 as an internal pressure so far as the tubes 11 are concerned. In addition, the tubes 11 (which may be of zirconium) will be subjected to neutron irradiation from the above-mentioned nuclear fuel which will engender irradiation growth of the material of the tubes and, in particular, potential differential growth in the lengths of the tubes inasmuch as the irradiation and the response of the tube material to it may both be non-uniform as between tubes.
The potential differential tube-length changes will give rise to axial forces in the tubes I 1, acting on the tube plates 12 and 13.
However, to the extent that potential differential changes in tube length can be absorbed in the tubes themselves, the axial forces which they engender will be correspondingly reduced; and the relatively thinwalled tube regions 20 enable potential differential changes of tube-length to be absorbed to a large extent in the tubes themselves, with the generation of only relatively small axial forces, while the relatively thick-walled regions 19 confer on each tube as a whole the necessary structural strength to withstand anticipated pressures and stresses.
Various factors have a bearing on the selected thicknesses x and y, and on the dimensions a, b and c and their interrelation with one another, as will be apparent from the following illustrative details. It can be shown that, in a typical nuclear-reactor calandria as illustrated in Figure 1 and having its tubes 11 of zirconium but of uniform wall thickness (i.e. not in accordance with the present invention) a minimum wall thickness of 3.4mm is required if the tubes, of internal diameter 180mum, are to have the necessary resistance against collapse under an external pressure of 9 bars (g) in the space 16. Such uniform-thickness tubes may, in accordance with the invention, be replaced by zirconium tubes with the profile shown in
Figure 2, i.e. with a basic wall thickness x reduced in regions 20 to y, with x=4.2mm and y=2.75mm. It may be shown that, to provide the same resistance against collapse as in the tubes with uniform wall thickness of 3.4mm, the length b of each thin-walled region 20 should not be greater than 20mm when the length a of each thick-walled region 19 is l0mm, i.e. the ratio b/a should not be greater than 2 when the pitch c(= a + b) = 30mm. As the pitch c is increased, the required value of the ratio b/a falls rapidly at first (with the required value of b/a equal to unity when c is about 65mm) and then slowly towards an ultimate value of about 0.6. The maximum practical pitch c is about 800mm, at which the required ratio is 0.6, i.e. a = 500rnm and b = 300mm. It is also necessary to ensure adequate resistance against bursting due to internal pressure. If the axial lengths b of the regions 20 of reduced wall-thickness y are large enough, the bursting resistance will be governed essentially by the thickness y almost independently of the length a and thickness x of the regions 19 and of the ratio b/a. At small values of the pitch c, where considerations of only the resistance to collapse due to external pressure would indicate relatively large values of the ratio b/a as being permissible, it may be that only smaller values of the ratio b/a are consistent with an adequate resistance against bursting due to internal pressure. At the same time, it has to be remembered that the object of the invention is that the thin-walled regions 20 should accommodate potential differential changes in the lengths of the tubes 11, and from that point of view it is desirable that the ratio b/a should not be too small, i.e. that the proportion of the tube which is thin-walled should be sufficiently large that the potential differential change in length of the whole tube is a reasonably small percentage of the total axial length of its thin-walled regions. To the extent that potential differential changes in the tube lengths are due to, say, non-uniform thermal expansion, they are reversible and non-cumulative; but in the case of potential differential growth due to neutron irradiation, this effect and the accompanying differential irradiation creep experienced at the temperatures encountered are cumulative, and the ratio b/a must be adequate to ensure that the thin-walled regions will be able to accommodate these accumulating effects over the whole life of the calandria. In that connection, it may be noted as a fortunate circumstance that irradiation creep does not lead to a form of creep embrittlement such as is sometimes observed in cases of thermal creep. The reason is that irradiation creep occurs as a random process effective through the whole of the material, and not preferentially at localised sites as can occur in thermal creep.
Apart from providing adequate resistance to bursting and inward collapse, and a suitable value of the ratio b/a to maintain within an acceptable limit the strain occurring in the thin-walled regions 20, other factors, possibly conflicting, may also enter into consideration. For ecample it may be desirable to minimise the amount of material in the tubes, either because of material cost or because of the effects (for example, absorption of neutrons) which the material by its presence will have during use, such that reduction of the amount of material results in a reduced requirement of nuclear fuel to achieve a given useful output.
Tubes for a calandria assembly according to the invention may be manufactured in a variety of ways. For example, the tube 11 shown in Figure 2 can be made from an initially uniform-thickness tube (of wall thickness x) simply by machining material away from the inside surface at the regions 20. Procedures for machining a pyrophoric material such as zirconium require care, but the principles and practice are well established. Instead of machining separate spaced cylindrical regions 20, it may be more convenient to machine a single continuous spiral region of reduced wall thickness, particularly where the pitch c is to be relatively small. Instead of machining material away, either in distinct rings or in a continuous spiral, it may be practical to use the method of "chemical contouring", which is widely used in the aircraft industry for making components of complex shape. Then again, suitable tubes might be fabricated, as illustrated in Figure 3, by providing a uniform-thickness tube 21 with an additional layer of reinforcing material at, and forming, the regions of greater wall thickness, such additional layer being provided in the form of close-fitting stiffening rings 22 of axial length a spaced apart from one another by distance b to give a pitch c( = a + b). Such a tube would have less resistance to bursting than the equivalent tube constructed as in
Figure 2, but would actually show a lower axial strain accummulation since strain would be distributed over the whole length of the tube 21 instead of only over the regions 20 of the tube 17. As an alternative to spaced separate rings, the additional layer may be provided as a continuous spiral of reinforcing material.
Both the tubes shown in Figures 2 and 3 are smooth externally, because in a calandria assembly as shown in Figure 1 it is the external surface which is contacted by the moderator liquid (which flows to provide cooling so as to remove the heat received, unavoidably, by heat transfer from the pressure tubes accommodated in the tubes 11 as well as, directly, by neutron irradiation); but equally, within the scope of the invention, an integral or fabricated tube corresponding to those shown in Figures 2 and 3 respectively may have its internal surface smooth and its integral or separately provided stiffening rings or spiral provided on its outer surface.
WHAT WE CLAIM IS:
1. A nuclear-reactor liquid-moderator calandria assembly comprising two tube plates, spaced apart from each other and each formed with a plurality of tube-receiving apertures, a plurality of tubes extending in generally mutually parallel relationship between the two tube plates, and a peripheral wall secured to the tube plates and enclosing therewith a space through which the said tubes extend between the tube plates, wherein each tube mates with a respective aperture of each tube plate and is there rigidly secured to the respective tube plate, and the tubes have walls which are of nonuniform wall thickness and comprise regions of greater wall thickness separated from one another in the axial direction by regions of lesser wall thickness.
2. A calandria assembly as claimed in claim 1, wherein the tubes are formed with
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (6)
1. A nuclear-reactor liquid-moderator calandria assembly comprising two tube plates, spaced apart from each other and each formed with a plurality of tube-receiving apertures, a plurality of tubes extending in generally mutually parallel relationship between the two tube plates, and a peripheral wall secured to the tube plates and enclosing therewith a space through which the said tubes extend between the tube plates, wherein each tube mates with a respective aperture of each tube plate and is there rigidly secured to the respective tube plate, and the tubes have walls which are of nonuniform wall thickness and comprise regions of greater wall thickness separated from one another in the axial direction by regions of lesser wall thickness.
2. A calandria assembly as claimed in claim 1, wherein the tubes are formed with
axially alternating cylindrical regions of greater and lesser wall thickness.
3. A calandria assembly as claimed in claim 1, wherein the tubes are formed with helical grooves constituting tube-wall regions of lesser wall thickness compared with regions of the tube walls, between turns of the grooves, which are of greater wall thickness.
4. A calandria assembly as claimed in any of claims I to 3, wherein each tube has its regions of greater and lesser wall thickness formed as a single integral structure.
5. A calandria assembly as claimed in any of claims I to 3, wherein the said tubes are formed by providing tubes of uniform wall thickness with an additional layer of reinforcing material at, and forming, the said regions of greater wall thickness.
6. A nuclear-reactor liquid-moderator calandria assembly substantially as described herein with reference to, and as illustrated in, the accompanying drawings.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB40716/77A GB1604443A (en) | 1977-09-30 | 1977-09-30 | Nuclear-reactor calandria assembly |
| CA312,400A CA1098845A (en) | 1977-09-30 | 1978-09-29 | Tube assemblies |
| JP11992578A JPS5460683A (en) | 1977-09-30 | 1978-09-30 | Pipe assembly |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB40716/77A GB1604443A (en) | 1977-09-30 | 1977-09-30 | Nuclear-reactor calandria assembly |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1604443A true GB1604443A (en) | 1981-12-09 |
Family
ID=10416272
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB40716/77A Expired GB1604443A (en) | 1977-09-30 | 1977-09-30 | Nuclear-reactor calandria assembly |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS5460683A (en) |
| CA (1) | CA1098845A (en) |
| GB (1) | GB1604443A (en) |
-
1977
- 1977-09-30 GB GB40716/77A patent/GB1604443A/en not_active Expired
-
1978
- 1978-09-29 CA CA312,400A patent/CA1098845A/en not_active Expired
- 1978-09-30 JP JP11992578A patent/JPS5460683A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5460683A (en) | 1979-05-16 |
| CA1098845A (en) | 1981-04-07 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed [section 19, patents act 1949] | ||
| PCNP | Patent ceased through non-payment of renewal fee |