Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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NUCLEAR POWER PLANT
BACKGROUND OF THE INVENTION
This invention relates to structures which are
required to be leak-tight or pressure-tight to fluids,
particularly gases. The invention has particular rota-
tionship to nuclear-reactor power plants including struck
lures on which the condition of leak-tightness is imposed.
This invention has unique advantages in maintaining the
structures of nuclear-reactor power plants leak-tight and
is here described with respect to such power plants. It
is to be understood that this invention has general apply-
lability and to the extent that this invention is employed
in other structures than nuclear-reactor power plants,
such use is within the scope of equivalents of this invent
lion or of any patent which may issue on or is a result
thereof.
A nuclear-reactor power plant includes a con-
tenement for the nuclear reactor and a plurality of axle-
Mary buildings and heat-transport-system buildings which
have facilities for monitoring the reactor and for convert-
in the energy generated by the reactor into electrical power. The heat-transport-system buildings and the Audi-
Mary buildings have walls of reinforced concrete. Where
these walls are required to be leak-tight or pressure-
tight, they are lined with a pressure-tight metal, usually
carbon steel. Where the word "wall" is used herein goner-
ally it is intended to comprehend within its meaning, not
only the side walls, but also the ceiling or top wall and
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the floor or bottom wall of a building. On occasions the
ceiling or floor may be referred to specifically.
Typically a nuclear power plant includes in
addition to the containment an auxiliary building and a
heat-transport-system building which carry pipes for
sampling the coolant and are referred to as a pup and
sampling pup. Where the coolant is a highly reactive
liquid such as sodium, the pup and the sampling pipe-
way must be maintained leak-tight to guard against the
lo consequences of a spill of the liquid particularly as the
liquid is radioactive. It is also necessary that nitrogen
at a controlled pressure be maintained within the pup
and the containment. The pup (auxiliary building) is
separated from the sampling pup (heat-transport-system
building) by a seismic gap. There is a passage between
the pup and the sampling pup across this gap whose
boundaries must be maintained leak-tight. The spacing
between the walls of the pup and the walls of the
I` sampling pup is variable.
Typically the spacing between the pup wall
and the wall of the sampling pup at the seismic gap is
between 2 and 3 inches. The expansion and contraction of
the gap between the buildings may vary between 1/4 inch
and 1 inch. It is essential that the joint along the
boundaries of the passage between the pup and the
sampling pup be leak-tight regardless of changes in
the spacing between the walls of these buildings at the
passage.
In accordance with the teaching of the prior art
an attempt was made to maintain this joint leak-tight by
providing along the boundaries of the passage across the
seismic gap a thin steel plate of angular transverse
cross-section. Typically the internal angle of the plate
was about 140 with one leg of the angle welded to the
metal with which the floor, walls and ceiling of the
pup are lined and the other arm welded to the metal
with which the floor, walls and ceiling of the sampling
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pup are lined. It was anticipated that this angle
plate would fold or straighten out without rupturing or
cracking to accommodate the contraction or expansion of
the seismic gap caused by the varying displacement of the
structures defining the gap. This anticipation was not
realized. Under the strain caused by the structural
motion, there were cracks at all four corners of the
boundary of the passage.
It is an object of this invention to overcome
the failure of the prior art and to provide a nuclear
power plant in which structures separated by seismic gaps
shall be leak-tight where leak-tightness is demanded.
It is also an object of this invention to pro-
vise a leak-tight gap liner at the passage across a sots-
mix gap between the heat-transport-system building and an
auxiliary building or between auxiliary buildings of a
nuclear reactor power plant which gap liner shall maintain
the power plant reliably leak-tight. More generally it is
an object of this invention to provide a structure having
compartments which are separated by an expansion gap or a
seismic gap or the like sealed by a joint in which the
joint shall be reliably leak-tight.
SUMMARY Of THE INVENTION
This invention arises from the discovery and
realization that, in the prior art gap liners, the junk-
lions which are usually butt welded at the corners, where
the vertical parts of the angle plates along the vertical
walls and the horizontal parts of the angle plates along
the floor or ceiling intersect, do not function as flex-
bye transition junctions or joints. The strain induced in the angle plates, particularly at the corners, is three
dimensional. Experience with the prior art structure
demonstrated that it was not possible to provide a flex-
bye transition member capable of moving freely in three
dimensions which could be accommodated in the limited
space available for installation.
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In accordance with this invention there is
provided, for structures including a seismic gap, a gap
liner including flexible assemblies in whose operation the
strain resulting from varying displacement of the walls at
the gap, is relieved by the flexible assemblies so that
leakage is precluded. Usually the walls of the passage
between the heat-transport-system building and an axle-
Mary building at the seismic gap define a rectangular
opening or passage between the buildings and the flexible
assemblies are provided at the corners of the boundaries
of the passage and may be described as flexible corner
assemblies. More generally, flexible assemblies are
provided in the regions of the boundary of the passage
between the buildings where the boundary changes direct
lions; e.g. from vertical to horizontal or vice versa.This invention may be adapted to structures in which the
passage at the joint is defined by curved walls. Such
adaptation is within the scope of equivalents of this
invention. In the interest of resorting to a concrete
configuration to aid those skilled in the art to understand
this invention, the following description of this invent
lion will confine itself to a structure in which the walls
at the seismic joint define a rectangular passage and
flexible corner assemblies are provided at the corners.
In the practice of this invention each flexible
corner assembly includes a bent or arcuate center corner
section and two straight transition sections which extend
from the ends of the corner section. The transition
sections act as transitions with respect to strain between
the parts of the gap liner to which they are connected and
the center of the flexible assembly. The corner sections
and the transition sections are formed of angle plates
from whose lateral ends members extend which are of goner-
ally transverse U-cross section and may be described as
box-like members open at the bottom. The straight transit
lion sections are long narrow box-like members. Specific
gaily, there are at each corner four transition sections,
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one each along the surfaces in one plane of the two oppo-
site walls at the seismic gap; e.g., the vertical sun-
faces, and one each along the surfaces of these walls
which are at right angles to the first-mentioned surfaces;
e.g., the horizontal surfaces. The straight transition
sections convert the large deflection of the angle plates
which occurs in prior-art apparatus into deflection at
right angles to this large deflection of the legs of the
box-like members or U-section members. The legs of the
members of the center bent or arcuate section accommodate
a large magnitude of motion of the buildings at the gap
with small strain at the seal-welded joint across the
seismic gap. A brief description of how this is accom-
polished follows.
The leg of the U of each member of a flexible
corner assembly which is towards the interior of the
building along whose wall it extends, herein called the
outer leg, is sealed to the wall; i.e., to the wall liner,
of its associated building. The other leg of the same
U-section member is disconnected from the same wall. The
transition members take up the strain in the angle plate,
when the width of the joint is changed, by converting the
stress, which would tend to deflect the angle plate, into
a stress on the transition member at right angles to the
stress on the angle plates. This stress deflects or
deforms the U-section member without materially affecting
the angle plate. The center bent portion of the assembly
at each corner is a member which is bent so that it
approaches the shape of an arc parallel to the arc tangent
to the walls at the corner. This member connects the
transition sections. This center portion has at its ends
members of generally U transverse section.
In the typical practice of this invention there
are four transition sections at each corner. Less than
four transition sections at each corner may be adequate to
relieve the strain at each. For example there may be
transition sections only along the perpendicular walls
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defining a seismic joint of only one of the two buildings
at each corner. Power plants and more general structures
including less than four transition sections at each
corner are within the scope of equivalents of this invent
lion. Where the passage is curved instead of rectangular the flexible assemblies with the U-section members may
extend along the curved boundaries of the passage as
needed with the outer member of the U sealed to the bound
defy and the inner member disconnected from the boundary.
The gap liner with its flexible assemblies, can
be composed of thin ductile metal; e.g., 1/8" or 3/16"
mild steel, stainless steel, aluminum or the like. This
gap liner has general applicability to structures of all
types which may require a flexible continuous leak-tight
junction. The assembly may serve to replace the circular
metal bellows which are currently used.
BRIEF DESC~IPTION_OF THE DRAWINGS
For a better understanding of this invention,
both as to its organization and as to its method of opera-
lion, together with additional objects and advantages
thereof, reference is made to the following description,
taken in connection with the accompanying drawings, in
which:
Fig. 1 is a fragmentary plan view of a nuclear
power plant in accordance with this invention;
Fig. 2 is a view in side elevation of the pass-
age between the sampling pup and a pup at the
seismic gap, looking towards the pup from the sampling
pup of the plant shown in Fig. l;
Fig. 3 is a fragmental view in side elevation
enlarged of the portion of Fig. 2 in circle III;
Fig. 4 is a view in section taken along the line
IV-IV of Fig. 3;
Fig. 5 is a view in end elevation taken in the
direction V of Fig. 3;
Fig. 6 is a view in section taken along line
VI-VI of Fig. 5;
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Fig. 7 is a fragmental view in isometric
showing a flexible corner assembly which constitutes an
important feature of this invention;
Fig. 8 is a fragmental diagrammatic view showing
the manner in which an assembly, in accordance with the
teachings of the prior art, sealing the passage at a
seismic gap, changes as the width of the gap is increased;
and
Fig. 9 is a similar fragmental diagrammatic view
for a passage at a seismic gap sealed by an assembly in
accordance with this invention.
DETAILED DESCRIPTION OF EMBODIMENT
-
The drawings show a nuclear-reactor power plant
11 (Fig. 1) including a nuclear reactor 13 in a contain-
mint 15 and an auxiliary building 16. Among the other
buildings of the plant 11 is a sampling pup wheat-
transport-system building) 17 which is separated from the
pup in auxiliary building 16 by seismic gap 19. There
is a rectangular passage 22 (Fig. 2) between the sampling
pup 17 and the pup 16. A gap liner 21 spans the
gap 19 at this passage.
Typically the coolant for the reactor is liquid
sodium which is radioactive. The sodium flows through
pipes in the pup 16 and sampling pup 17 and a
break in the pipes would produce a spill of the radio-
active sodium which must be contained. In addition a
controlled atmosphere of nitrogen is maintained in the
pup 16 and in the sampling pup 17. The pup 16
and sampling pup 17 must be leak-tight against outflow
or inflow of fluids such as the nitrogen possibly contain-
in radioactive matter, between the pup and sampling
pup and the outside air. To achieve this purpose the
walls of the sampling pup and pup are provided
throughout with liners 23 and 25 (Figs. 2, 4, 7) of, typic
Sally, carbon steel sheet. The gap liner 21 is sealed
leak-tight to the boundary of the passage 22 and the leak-
tightness must be preserved regardless of changes in the
gap width.
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The gap liner 21 includes angle plates 31 and 33
(Figs. 3, S, 7) extending along the sides of the boundary
of the passage 22. These angle plates are seal-welded to
the liner 25 of the pup 16 and to the liner 23 of the
sampling pup 17. At each corner of the boundary, the
angle plates 31 and 33 are connected to a flexible corner
assembly 35 (Fig. 2, 3, 4, 7). Each corner assembly 35
includes a straight transition section 37 colinear with
plates 31 and a straight transition section 39 colinear
with plate 33 (Fig. 3). The straight sections 37 and 39
are joined by what may be described as a curved section.
This curved section is formed of smaller subsections 41, 43
and 45 at an angle to each other. Typically there are three
such sections, the first 41 at 165 to the straight section
37, the second 43 at 150 to the first 41 and the third 45
at 150 to the second 43 and at 165 to the straight section
39. Within the scope of this invention there may be more
than three sections. The envelope of the intersections
37-41, 41-43, 43-45 and 45-39 is an arc of a circle par-
allot to the arc tangent to the walls defining each corner
of the boundary. The contour of the sides 31, 41, 43, 45,
39 is generally such an arc.
Each flexible corner assembly 35 is of generally
W transverse section (Figs. 7, 9) throughout from the
outer end of straight section 37 to the outer end of
section 39. It includes a central angle portion 51 which
is integral at its ends with members 53 and 55 (Fig. 4) of
generally U-transverse section. The members 53 and 55 may
be described as box-like open at the bottom. Each member
has an outer leg 57 and an inner leg 59 (Figs. 4, 7, 9).
Laterally the corner assembly 21 spans the seismic gap lo
between the buildings 15 and 17. The outer legs 57 are
respectively welded leak-tight to the liner 25 of the pup
and to the liner 23 of the sampling pup. The inner
legs 59 are disconnected from the liners 23 or 25 on each
side (Figs. 4, 7, 9). The plates 31 and 33 are joined to
the angle portion 51 by butt welds 61 and 63 (Fig. 3). The
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subsection 41 is jollied to the section 37 by butt weld 65,
the subsection 43 to subsection 41 by butt weld 67, 43 to
45 by butt weld 69 and 45 to 33 by butt weld 71.
Typically the overall width of a flexible corner
assembly may be 15 inches and the width of the members 53
and 55 may be 1 inch. The assembly is centered over the
gap 19 with the inner leg 59 of each member I inches and
the outer leg 57, I inches from the center line through
the apex of angle plate 51. The end of transition section
39 is typically 2 ft. 1 inch from the remote side of
transition section 37 and the end of transition section 37
is 2 ft. 1 inch from the remote side of transition section
39.
Fig. 8 shows the changes which take place in a
gap-liner plate in accordance with the teachings of the
prior art when the seismic gap 19 is widened. The ends of
angle plate 81 are seal welded to liners 23 and 25 at b
and e. Widening of the gap 19 from ad to cud' displaces
the seal welds from b to b' and e to e' and drops the apex
a to a'. The strain produced causes cracks to develop in
the liner plate 81 at the corners of the passage 22.
Corresponding changes take place where the gap 19 is
shortened.
Fig. 9 shows the changes which take place in the
gap liner 21 when the gap 19 is widened from go to go
In this case the seal weld at f is moved to f' and the seal
weld k to k' but the position of the angle plate 51 no-
mains substantially unchanged. The movement is taken up
by the deformation of members 55 and 57 to 55' and 57'. A
corresponding change occurs when the gap 19 is shortened.
While preferred embodiments of this invention
have been disclosed herein, many modifications thereof are
feasible. This invention is not to be restricted except
insofar as is necessitated by the spirit of the prior art.
