US3636674A

US3636674A - Insulation module with superposed deformed core sheets

Info

Publication number: US3636674A
Application number: US388548A
Authority: US
Inventors: George D Cremer
Original assignee: US Atomic Energy Commission (AEC)
Current assignee: US Atomic Energy Commission (AEC)
Priority date: 1964-08-10
Filing date: 1964-08-10
Publication date: 1972-01-25
Anticipated expiration: 1989-01-25

Abstract

Insulation modules having a core of relatively movable, flat and corrugated metal sheets assembled between opposed faceplates and having deformable, seal-forming portions projecting beyond the faceplates. Methods of fabricating such modules and of forming them into modular insulation assemblies.

Description

finite Seams ateni firemen [4 1 Jan. 25, 1972 54] HNSULATION MODULE WITH 3,054,524 9/1962 Casten ..220/|5 SUPERPOSED DEFORMED CORE 3,151,712 10/1964 Jackson SHEETS 3,190,412 9/1965 Putter et a1. 3,212,861 10/1965 Whitesides ..52/410 [72] Inventor: George D. Cremer, Lemon Grove, Calif. FORE'GN PATENTS OR APPLICATIONS [73] Assignee: The United States of America as represented by the United States Atomic 66886O 8/963 Canada Energy Commision 891,353 3/1962 Great Britain 609,625 9/1960 Italy [22] Filed: Aug. 10, 1964 Primary Examiner-Frank L. Abbott [2H Appl' 388548 Assistant Examiner-Alfred C. Perham A!l0rneyRo1and A. Anderson [52] US. Cl ..52/509, 52/249, 52/573,

52/618, 52/40'4, 176/87 [57] ABSTRACT [221;] ..E04b 2/44, 1304b 1/78 Insu'ation modules having a core of relatively movable flat I l 0 5 f and corrugated metal sheets assembled between opposed ,6 5 9 Q 3 f faceplates and having deformable, seal-forming portions pro- IS D 1 5 220/9 9 A jecting beyond the faceplates. Methods of fabricating such th d 1 1 t' [56] References Cited Ehoiules and of forming em into mo u ar msu a 1011 assem UNITED STATES PATENTS 11 Claims, 10 Drawing Figures 2,482,618 9/1949 Hosbein ..52/573 X STEAM INVENTOR GEORGE DORLA/VD CREME BY M7$MQM ATTORNEYS PATENTEU JANZS 19. 2

SHEET & 0F 6 INVENTOR GEO/75E DORLAND CREME ATTORNEYS PATENTED M25 1972 3.836374 SHEET 5 [IF 6 I NVENT OR GEORGE DORLAND CREMEH BY /M 9M ATTORNEY.)

PATENTED mes 1972 SHEET 6 UF 6 GEORGE DORLAND CREME R ATTORNEYS INSULATION MODULE WITH SUPERPOSED DEF ORMED CORE SHEETS STRUCTURE AND METHOD This invention relates generally to thermal insulation, more particularly to metal insulation, and, specifically, to sandwichtype insulation modules and assemblies thereof.

The novel insulation modules and modular assemblies provided in accordance with the principles of the present invention are particularly useful for providing internal thermal insulation for gas-cooled nuclear reactors and associated plumbing. However, the novel insulation modules and modular assemblies provided by the present invention are by no means useful only in this particular application, but may be advantageously utilized wherever thermal insulation is required. Therefore, although the advantages and principles of the present invention will be developed by reference to this particular application, it is to be understood that the ensuing description is not intended to limit the scope of the present invention.

Nuclear reactors offer a good but as yet unrealized potential for the efficient and economical production of electrical power from fissionable materials; One reason that reactors have not yet proved economical is the expense of constructing the reactor. The reactor must be capable of withstanding the high temperatures generated in the fission reaction and must be resistant to radiation damage; and, to provide a reactor with these capabilities, it has heretofore been necessary to fabricate it from expensive alloys, adding materially to its initial cost. The present invention solves this problem by providing novel insulation modules and modular assemblies for insulating the reactor from the radiation and heat given off in the fission process. As a result, the reactor may be fabricated from economical materials such as mild steel at a cost much lower than has heretofore been possible.

The novel modules of the present invention consist of a core of juxtaposed corrugated metal sheets held in an assembled relationship which permits relative movement of the core sheets, making the module capable of withstanding stresses imposed by nonuniform heating.

A number of advantages are obtained by the novel module construction just described. For example, insulation modules constructed in accord with the principles of the present invention will withstand years of exposure to intense radiation at levels as high as 10 to 10 neutrons and gamma rays per square centimeter per second. Also, such modules are not effected by mechanical vibration, rapid variations in the pressure in the reactor, chemical corrosion, high temperatures, or thermal expansion. In addition, the modules of the present invention may be easily fabricated for and readily installed in or on reactors or other structures having a variety of flat, curved, cylindrical, and other configurations.

From the foregoing, it will be apparent that one major object of the present invention is the provision of thermal insulation which is particularly useful in gas cooled nuclear reactors.

Another important object of the present invention is the provision of thermal insulation structure which is sufficiently radiation-damage resistant to withstand years of exposure at radiation levels on the order of 10 to neutrons and gamma rays per square centimeter per second.

Yet another primary object of this invention is the provision of an insulation structure which will not deteriorate from mechanical vibration, pressure variation, chemical corrosion, or exposure to nuclear radiation.

Another important object of the present invention is the provision of an insulation structure capable of withstanding rapid gas pressure changes.

Still another object of this invention is the provision of insulation in accordance with the preceding object which will not contaminate the reactor gas or other atmosphere in which it is located.

Yet another object of this invention is the provision of insulation structure with a low thermal conduction factor which is capable of retaining its thermal properties over long periods of time in high-temperature environments.

Another object of the present invention is the provision of all-metal insulation in modular form which may be rapidly and easily assembled into or on structures having flat, curved, cylindrical, and other configurations.

A further specific object of this invention is the provision of insulation modules having strength and structural integrity and accommodating relative movement of core laminations and faceplates relative to each other to compensate for nonuniform thermal effects.

A related object is the provision of modules in which, upon assembly, the abutting edges of core laminations may be deformed to obtain a snug fit to maintain efficient insulating value in the seam area without transmitting shear loads between adjacent modules.

Another object of the present invention is the provision of novel methods for fabricating insulation modules in accord with the preceding objects.

Additional objects and further novel features of the present invention will become fully apparent from the appended claims and as the ensuing detailed description and discussion proceeds in conjunction with the accompanying drawing, in which:

FIG. 1 is a diagrammatic view of a plant employing a nuclear reactor of the type with which the novel insulation modules and modular assemblies of the present invention are particularly useful;

FIG. 2 is a vertical section through the reactor;

FIG. 3 is a perspective view of the interior of the upper portion of the reactor with a number of the insulation modules in place;

FIG. 4 is a perspective view of a portion of one form of novel insulation module provided by the present invention;

FIG. 5 is a fragmentary view of one form of core sheet which may be employed in insulation modules constructed in accord with the principles of the present invention;

Flg. 6 is a perspective view of a jig for assembling the insulation modules of the present invention;

FIG. 7 is an elevation, to an enlarged scale, of a number of modules and the fasteners by which they are retained in position;

FIG. 8 is a perspective view of a hemispherical insulation module for the upper end of the reactor;

FIG. 9 is a perspective view, to a reduced scale, of an alternate form of hemispherical insulation module; and

FIG. 10 is a cylindrical insulation module constructed in accord with the principles of the present invention.

As indicated above, the novel insulation of the present invention is particularly useful for insulating gas-cooled nuclear reactors and the associated plumbing. As shown diagrammatically in FIG. 1, the atomic pile 22 (see FIG. 2) is housed in the reactor 20. A gas, commonly helium, is circulated through the reactor, where it is heated, and then through a heat exchanger 24, where the hot gas converts water to steam. The steam is employed to drive a turbine 26 and is then condensed and recirculated through heat exchanger 24.

Reactor 20, shown in more detail in FIG. 2, is normally fabricated from a cylindrical center section 28 and lower and upper

hemispherical end sections

30 and 32 and is typically 35 feet in diameter and 45-50 feet long. Heretofore, the center section 28 and lower end section 30 have been designed of 3- inch thick stainless steel and the upper end section (or hot dome) 32 of 5-inch thick stainless steel.

Domes

30 and 32 are provided with a gas inlet 34, a gas outlet 36, and access ports 38 for instrumentation, control rods, fuel cells and the like for pile 22 which is suspended in the center of reactor 20.

Reactor 20 is shielded by a 1-inch thick stainless steel liner or thermal barrier 40 which, as shown in FIG. 3, rests on an annular ledge 41 at the lower end of the reactors center section 28. Liner 40 is parallel to and spaced from center section 28 and hot dome 32 of reactor 20 and, as shown in FIG. 2, defines an annular channel for the flow of cooling gas.

In accord with the present invention, the interior of liner 40 is lined with a wall 42 constructed of insulation modules 44 of novel construction to thermally isolate reactor from atomic pile 22. Additional insulation modules are employed to insulate hot gas outlet 36 and other plumbing of the reactor. Employing insulation as just described makes it possible to fabricate reactor 20 from relatively inexpensive mild steel instead of stainless steel as was heretofore necessary, which is extremely important since it materially reduces the cost of the reactor.

Turning next to FIG. 3, the portion of insulation shell 42 attached to the cylindrical lower portion of liner 40 consists of generally rectangular insulation modules 44 which are typically 2 feet square and 3 inches thick although these dimensions are not critical and may be varied as the design requires.

Insulation modules 44, as shown in FIG. 4, each consist ofa pair of parallel, spaced apart

face plates

46 and 48 between which a core 50 composed of a stack of superposed, embossed core sheets 52 is sandwiched. Tie rods 54, extending through core 50 and fixed at their opposite ends to

face plates

46 and 48, maintain configural integrity ofmodule 44.

Faceplates

46 and 48 might typically be 0.050-inch thick stainless steel. and core sheets 52 are preferably made from stainless steel foil having a thickness ranging from 0.001 to 0.01 inch.

Any suitable pattern may be embossed on the metal foil from which core sheets 52 are formed. The only important requirements are that the pattern selected: (I provide as little metal-to-metal contact as possible between adjacent sheets; (2) divide the space between adjacent sheets into small pockets of relatively stagnant gas; and (3) provide a small degree of communication between the pockets. Minimum metal-to-metal contact is desirable to minimize conductivity through the module and thereby maximize its insulating properties. The division of the spaces between adjacent sheets into pockets in which the helium or other gas in the reactor is stagnant materially enhances the insulation properties of the module as the stagnant gas transfers heat very slowly between adjacent core sheets.

Some degree of connection between the pockets is necessary to prevent rapid pressure changes in the reactor from destroying the insulation. For example, pressurized reactors of the type described above may suddenly he depressurized. In such circumstances, he communication between the gas pockets in an insulation module facilitates gas flow and equilization of the pressure within the module and between the module and the reactor, preventing the imposition of unequal pressures on and destruction ofthe module.

Referring now to FIG. 5, one type of core sheet 52 which may be used in insulation modules of the type illustrated in FIG. 4 has a sawtoothlike appearance, providing parallel, spaced-apart ridges 56 alternately visible from opposite sides of the sheet. Ridges 56 are designed to provide minimum contacting area when abutted against an adjacent sheet. It is not critical, however, that this particular form of core sheet be employed as any core sheet having the characteristics described above may be used.

The insulation module 44 just described may be assembled in any convenient manner such as in the simple jig 70 illustrated in FIG. 6. This jig may be fabricated of any suitable material and includes spaced-apart bottom bars 71 for supporting the module, side members 72 arranged in a rectangle having the same dimensions as the module, and vertically extending L-shaped guides 74 at the four corners of the jig. Bottom faceplate 48 is placed in jig 70 and a predetermined number ofcore sheets 52 are stacked on the bottom plate. The second faceplate 46 is then placed on the core 50 comprised of the stacked core sheets 52 and holes for tie rods 54 are pierced through

faceplates

46 and 48 and core 50. Piercing of the tie rod apertures is an important feature in the assembly of modules 44 since this precludes contamination of core 50 and the helium gas which it will later contact with metal chips, oil, or other foreign material as would be the case if the tie rod holes were drilled or similarly formed.

Following the piercing operation, tie rods 54 are inserted into the tie rod holes and the ends of the rods are upset and welded to faceplates 46 and 48.

An important feature of the assembly process just described is that the piercing operation is designed to develop a hole having a diameter slightly larger than that of the associated tie rod 54 to minimize contact between the tie rod and the core sheet 52. This permits slight movement of core sheets 52 relative to each other and to

faceplates

46 and 48, eliminating shear forces which would otherwise be exerted on the module by nonuniform heating. Consequently, the novel insulation modules of the present invention are not adversely affected by nonuniform heating.

Referring back to FIG. 4, core 50 of the insulation module 44 just described is slightly larger than

faceplates

46 and 48 so that core sheets 52 protrude beyond the faceplates. This feature is important in the assembly of modules 44 to form the insulation shell or assembly 42 shown in FIG. 2. Specifically, the insulation modules are dimensioned so that, when fastened to liner 40 as shown in FIG. 3, there will be a slight interference fit between adjacent modules. Therefore, when the modules are assembled, the edges of the core sheets 52 of adjacent modules deform against each other providing thermal and radiation sealing along the joints between adjacent modules. At the same time, the sealing arrangement prevents the transmission of shear loads between adjacent modules which is an important feature of the present invention since it prevents destruction of the shell by nonuniform heating, mechanical vibration, pressure changes, and the like.

Instead of employing the tie rods described above to assemble the core sheets and faceplates into self-sustaining modules and then fastening the modules to liner 40, the fastening arrangement shown in FIG. 7 may be employed. Referring now to this figure, studs 76 may be welded or otherwise fixed to the inner surface of and oriented to extend inwardly from liner 40. The modules, in the form of an unconnected assemblage of core sheets and faceplates, are then positioned against studs 76 and retained in place by washers 78 and nuts 80 threaded on studs 76. As in the previously described arrangement, adjacent modules are designed to have a slight interference fit when assembled to provide thermal and radiation sealing around studs 76 and along the joints between adjacent modules without transmitting shear loads between adjacent modules.

The upper end of insulation shell 42 is generally hemispherical insulation module 82 as shown in FIG. 8. This module may advantageously be formed of the cross corrugated type of core sheet material illustrated in FIG. 5 and discussed above because the latter is readily deformable and has excellent drapability characteristics so that it can be readily molded into hemispherical or other three-dimensional contours.

Module 82 is constructed by building a core 84 on a generally hemispherical faceplate 86 (which may be of the same type of material as

faceplates

46 and 48 discussed above) from strips of foil which are cut and arranged in layers until the desired thickness of the core 84 is obtained.

A second faceplate 88 is arranged on top of core 84 and the two faceplates interconnected with tie rods (not shown) in the manner described above in conjunction with modules 44. The necessary ports or openings are formed in insulation module 82 at any time during construction of the module, as by punching or cutting holes in each sheet; and the assembled modules are attached to stainless steel liner 40.

If the dome or other contoured vessel portion to be insulated is small and relatively few ports are required, an alternate method of fabricating the insulation module may be employed. Specifically, the outer faceplate is employed as a mold and a core is built up in the manner just described. However, as each layer of core sheet material is added, the individual strips may be attached to those of the subjacent layer as by poke welds. When the core has been built to the desired thickness, the outer face plate is removed, leaving a selfsustaining module consisting of superposed layers of cross corrugated core sheet material.

The hot gas outlet 36 from reactor 20 and other plumbing may advantageously be insulated with a cylindrical module 90 of the type illustrated in FIG. 10. Referring now to the latter figure, module 90 consists of concentric inner and outer sleeves 92 and 94 (preferably of the same material as faceplates 46 and 48) between which a core 96 is sandwiched. Core 96 consists mainly of corrugated core sheets 98 which, as shown in FIG. 10, may have a simple sine wave cross-sectional configuration.

Adjacent corrugated sheets 98 are separated by flat, unembossed core sheets 100 to prevent internesting of adjacent corrugated core sheets 98. Tie rods as described above may be employed to fasten together the inner and

outer sleeves

92 and 94, if necessary or desired. However, it may not be necessary in many cases to employ tie rods as the friction between the core sheets and the faceplates and adjacent core sheets will maintain the structural integrity of the module.

Modules 90 can be fastened to the structure being insulated in the same manner as the

modules

44 and 82 described above, or, if the module surrounds and is supported by a pipe or the like, connections between it and the insulated structure may be unnecessary.

Although the illustrated cylindrical module 90 employs core sheets with a sine wave corrugation, it is not necessary that this particular type of core sheet be employed; and, for some applications, it may be advantageous to employ the type of core sheet illustrated in FIG. 5 and described above or core sheets having still other forms of configurations and the characteristics described above. Such. modifications are, therefore, to be understood as being within the scope of the present invention as is the use of insulation produced in accord with the principles of the present invention to insulate other than nuclear reactors. I

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent l. A self-supporting insulation module, comprising:

a. a stack of superposed embossed core sheets having protuberances separating said sheets with a minimum of contact between adjacent sheets and dividing the spaces between said sheets into small substantially mutually isolated areas;

b. faceplates of sufficient thickness to be substantially rigid on opposite sides of said stack of core sheets;

c. means for holding said core sheets and said faceplates in assembled relationship, said holding means permitting relative movement between said plates and said core sheets in planes parallel to said sheets and preventing movement therebetween in a direction perpendicular to said planes and said faceplates; said core sheets being fabricated of adeformable material and, on at least one edge of the module, said core sheets protruding beyond the faceplates;

e. whereby the protruding portions of said core sheets can be deformed against a component adjacent said one edge of said module to provide a seal between said module and said component and to at least minimize the transmission of shear loads between said module and said component.

2. A module as defined in claim 1, wherein said core sheets are of metal foil.

3. A module as defined in claim 2, wherein said metal is stainless steel and said foil has a thickness in the range of 0.001 to 0.010 inch.

4. A module as defined in claim 1, wherein said holding means comprises tie members extending through said stack of core sheets, the ends of said tie rods bein fixed to said faceplate and said tie members extending t rough aligned apertures in said core sheets of larger area than said tie member to permit movement of said core sheets relative to each other and to said faceplates.

5. A module as defined in claim 1, wherein the faceplates are stainless steel.

6. A module as defined in claim 1, wherein said faceplates are on the order of 0.050 inches thick.

7. A module as defined in claim 1, wherein the stack of superposed core sheets includes corrugated core sheets and flat core sheets distinct from and separating said corrugated sheets and cooperating with the corrugations thereon to divide the spaces between adjacent sheets into small, substantially mutually isolated spaces.

8. Insulation for nuclear reactors and other structures, comprising:

a. plural insulation modules lining the portion of the structure to be insulated, said modules each comprising a pair of faceplates and a stack of superposed core sheets sandwiched therebetween with the core sheets protruding beyond those edges of said plates which face adjacent modules and terminating in edges spaced from said plate edges;

b. means for retaining said modules in position on said structure portion; and

c. adjacent modules being disposed with their terminal edges in compressive abutting relationship establishing an interfering fit between said terminal edges and thereby ef fectively sealing the seams between adjacent modules while minimizing the transmission of shear loads between the modules.

9. Insulation as defined in claim 8, said modules being selfsupporting and including means for holding said core sheets and said faceplates in assembled relationship, said holding means permitting relative movement between said plates and said core sheets in planes parallel to said sheets and preventing movement therebetween in a direction perpendicular to said planes and said faceplates.

10. Insulation as defined in claim 8, wherein said core sheets are of metal foil.

11. Insulation as defined in claim 8, wherein the stack of core sheets includes corrugated core sheets and flat core sheets separating said corrugated core sheets and cooperating with the corrugations therein to divide the spaces between adjacent sheets into small, substantially mutually isolated spaces.

Claims

1. A self-supporting insulation module, comprising: a. a stack of superposed embossed core sheets having protuberances separating said sheets with a minimum of contact between adjacent sheets and dividing the spaces between said sheets into small substantially mutually isolated areas; b. faceplates of sufficient thickness to be substantially rigid on opposite sides of said stack of core sheets; c. means for holding said core sheets and said faceplates in assembled relationship, said holding means permitting relative movement between said plates and said core sheets in planes parallel to said sheets and preventing movement therebetween in a direction perpendicular to said planes and said faceplates; d. said core sheets being fabricated of a deformable material and, on at least one edge of the module, said core sheets protruding beyond the faceplates; e. whereby the protruding portions of said core sheets can be deformed against a component adjacent said one edge of said module to provide a seal between said module and said component and to at least minimize the transmission of shear loads between said module and said component.

2. A module as defined in claim 1, wherein said core sheets are of metal foil.

4. A module as defined in claim 1, wherein said holding means comprises tie members extending through said stack of core sheets, the ends of said tie rods being fixed to said faceplates and said tie members extending through aligned apertures in said core sheets of larger area than said tie member to permit movement of said core sheets relative to each other and to said faceplates.

5. A module as defined in claim 1, wherein the faceplates are stainless steel.

8. Insulation for nuclear reactors and other structures, comprising: a. plural insulation modules lining the portion of the structure to be insulated, said modules each comprising a pair of faceplates and a stack of superposed core sheets sandwiched therebetween with the core sheets protruding beyond those edges of said plates which face adjacent modules and terminating in edges spaced from said plate edges; b. means for retaining said modules in position on said structure portion; and c. adjacent modules being disposed with their terminal edges in compressive abutting relationship establishing an interfering fit between said terminal edges and thereby effectively sealing the seams between adjacent modules while minimizing the transmission of shear loads between the modules.

9. Insulation as defined in claim 8, said modules being self-supporting and including means for holding said core sheets and said faceplates in assembled relationship, said holding means permitting relative movement between said plates and said core sheets in planes parallel to said sheets and preventing movement therebetween in a direction perpendicular to said planes and said faceplates.