12 daniel c. meess - 4955983 - side loading vault system and method for the disposal of radioactive waste

United States Patent £191
Meess et al.
[S4] SIDE LOADING VAULT SYSTEM AND
METHOD FOR THE DISPOSAL OF
RADIOACI'IVE WASTE
[75] Inventors: Damel C. Meea, Murrysville; Bobby
J. Jones, Pleasant Hills; Raymond M.
Mello, Greensburg; ThoiiUIS G.
Weils, Jr.; James B. Wript, both of
Murrysville, all of Pa.
[73] Assignee: Westinghouse Electric Corp.,
Pittsburgh, Pa.
[21] Appl. No.: 331,587
[22] Filed: Mar. 31, 1989
[51] Int. CJ.S ........................... B09B 1/00; G21F 9/12
[52] u.s. Cl. .................................... 405/128; 405/129;
52/169.6
[58] Field of Seucll ................... 405/129, 128, 52, 53;
52/169.6, 21; 252/626, 633, 628
[56] RefereDees Cited
U.S. PATENT DOCUMENTS
2,704,983 3/1955 Van Dronkelaar ........... 52/169.6 X
3,255,896 6/1966 Sldorz .
3,385,012 5/1968 Loregreen .............................. 52/21
3,705,851 12/1972 Brauer .
4,166,709 9/1979 Valiga .
4,336,674 6/1982 Weber ................................ 52/169.6
4,375,930 3/1983 Valiga ................................. 405/128
4,453,857 6/1984 Serra et al........................... 405/128
4,586,849 5/1986 Hastings .
4,624,604 11/1986 Wagner et al...................... 405/128
4,631,872 12/1986 Daroga .......................... 52/169.6 X
4,701,280 10/1987 Canevall .
4,776,982 10/1988 Canevall .
[11] Patent Number:
[45] Date of Patent:
4,955,983
Sep. 11, 1990
4,784,802 11/1988 Mallory et al.................. 405/128 X
4,844,840 7/1989 Feizollahi ....................... 405/129 X
Primary Examiner-Dennis L. Taylor
[57] ABSTRACT
A side loading system and method for the underground
disposal of radioactive waste is disclosed herein. The
vault system is formed from at least one vault cell that
comprises a floor slab disposed within a recess in the
earth, a ceiling slab disposed over the floor slab, an
earth cap disposed over the ceiling slab and an elon-
gated wall assembly disposed around the periphery of
the floor slab for supporting the ceiling slab and earth
cap. The elongated wall assembly is preferably four
times as long as it is wide, and includes a back wall and
a front wall, the front wall having an accessway for the
side loading of radioactive waste. Radioactive waste is
loaded in sequential rows starting from the back wall of
the vault cell. Such a loading technique, in combination
with the elongated shape of the wall assembly, mini-
mizes radiation exposure to the personnel loading the
vault cell as the front-most row of waste helps to shield
the operators from radioactivity emitted by the balance
of the waste contained within the vault cell. Addition-
ally, because the ceiling slab does not depend upon the
waste for support, each vault cell can be completely
constructed and then inspected for structural faults
before radioactive waste is loaded therein. Finally, the
side-loading configuration of the vault cells advanta-
geously shelters radioactive waste from ambient
weather during the loading operation.
28 Claims, 5 Drawing Sheets

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4,955,983
2
SIDE LOADING VAULT SYSTEM AND METHOD
FOR THE DISPOSAL OF RADIOACTIVE WASTE
tunately, cumulative. In addition to radiation hazards,
the craning-in of waste packages into a top-loaded
burial site makes possible the occurrence of a waste-
dropping accident, which could rupture or otherwise
BACKGROUND OF THE INVENTION
This invention generally relates to vault systems for
the below ground disposal of hazardous waste, and is
specifically concerned with a side loading vault system
and method for the disposal of low-level radioactive
5 damage one or more of the waste containers within the
burial site. Finally, because the ceilings of such burial
sites depend upon the waste itselffor structural support,
there is no way that the system operators may reliably
waste. 10
Burial systems for the disposal of radioactive and
other types of hazardous waste are known in the prior
art. In some of these systems, a large hole is excavated
in the earth, and a floor structure formed from a con-
crete slab and a layer of gravel is constructed therein. 15
Radioactive waste that bas been packaged in 55 gallon
steel drums is then stacked over the floor structure of
the burial site. In some of these systems, monitoring
equipment in the form of drain pipes is laid around the
floor structure so that leakages of radioactive wastes 20
through the 55 gallon steel drums may be detected
before the waste bas an opportunity to contaminate
ground water. After the burial site bas been completely
filled with radioactive waste, water impermeable layers
of plastic material and compacted clay are placed over 25
the waste, followed by an earth cap onto which erosion-
resistant vegetation is often planted. In some burial type
systems, a layer of concrete is poured over the waste
prior to overlaying it with compacted clay and an earth
cap. 30
Unfortunately, there are a number of shortcomings
associated with such prior art burial-type systems that
significantly limit their ability to provide safe and inex-
pensive storage for hazardous waste. One major short-
coming of such a system is its inability to provide an 35
inexpensive and convenient means of retrieving leaking
waste containers. Thus, if the monitoring equipment
that is built into these systems should ever indicate the
presence of a serious radioactive leak from the contain-
ers disposed therein, a large portion of the earth cap, 40
compacted clay, water impermeable plastic and con-
crete overlying the waste containers would have to be
removed, and the leaking containers painstakingly lo-
cated by lifting the containers out of the burial cavity
one-by-one. After the leaking container or containers 45
were fmally located, the disassembled portion ofthe site
would, of course, have to be completely reconstructed.
Still another shortcoming associated with such prior art
burial site designs is the fact that the open burial cavity
exposes the waste to rain and other ambient weather 50
conditions during the loading operation. Since ·it may
take as long as four to six months for a utility to com-
pletely fill such a burial site with waste, a considerable
amount ofrain water can accumulate over the floor slab
of such a site. While this rain water can be periodically 55
pumped out, the expense associated with such an effort
is significant. Moreover, the presence of any standing
water in such a site for any length oftime promotes the
occurrence ofcorrosion and leaching through the walls
of the waste containers in contact with such water. Still 60
another shortcoming associated with such prior art
burial sites is the amount of radiation that the system
workers receive when loading such a site. The geome-
try of a top-loaded burial site is such that a worker
standing near the rim is exposed to radiation from most 65
every radiation container. Even when the waste depos-
ited in such burial sites is rated as low-level radioactive
waste, the effects of such radiation exposure are, unfor-
inspect the ceilings of such sites for structural faults
prior to loading of the waste therein.
Vault-type systems for the storage of such radioac-
tive wastes are also known in the prior art. While such
vault-type systems can overcome some ofthe disadvan-
tages associated with burial-type systems such as the
exposure of the waste to ambient weather conditions,
none ofthese systems ofwhich the applicants are aware
affords the system operators a convenient and expedi-
tious way of retrieving a leaking waste container in the
event that the monitoring equipment indicates the exis-
tence of a hazardous leak condition. Moreover, large
unitary vault systems formed from brittle construction
materials such as concrete are susceptible to cracking in
the event of subsidence or a seismic disturbance.
Clearly, there is a need for a vault-type system and
method for the disposal of radioactive waste that af-
fords convenient and expeditious access to the contents
of the vault in the event that the radiation monitoring
system indicates that a dangerous leak condition has
arisen. Ideally, such a vault system should shelter the
waste from the ambient weather during the loading
operation and expose the system operators to only a
minimal amount of radiation. The vault system should
have the capacity to store large volumes of radioactive
waste but yet not be susceptible to cracking in the event
of subsidence or seismic disturbances. Finally, the vault
system should be amenable to inspection prior to the
loading of waste packages therein, and should not set
the stage for the occurrence of dropping accidents
which could rupture or otherwise damage waste con-
tainers during the loading operation.
SUMMARY OF THE INVENTION
The invention is a side loading vault system and
method for the subterranean disposal of radioactive
waste that overcomes the shortcomings associated with
the prior art. The system is formed from at least one
vault cell that comprises a floor slab typically disposed
within a recess in the earth, a ceiling slab disposed over
the floor slab, an earth cap disposed over the ceiling
slab, tlJ1d an elongated wall assembly disposed around
the periphery ofthe floor slab for supporting the ceiling
slab and the earth cap. The wall assembly may include
a back wall and a front wall, the front wall having an
access way for loading radioactive waste within the
vault cell, wherein the elongated shape of the wall as-
sembly reduces the amount of radiation present in the
area of the cell between the waste disposed therein and
the front wall accessway when waste is loaded in se-
quential rows from the back wall to the front wall ofthe
cell. The vault cell preferably includes a removable wall
structure for sealing the accessway in the wall assembly
after the cell has been completely filled with radioactive
waste. The removable wall structure may be con-
structed by assembling a plurality of mutually interfit-
ting wall elements that resemble T-shaped concrete
blocks. The removability ofthis wall structure advanta-
geously affords access to the waste contained within the

3
4,955,983
4
cell in the event ofa leakage condition without the need
for penetrating either the ceiling slab or the integral
walls of the wall assembly. Finally, a monitoring aisle-
way is left between the waste and the inner surface of
the walls of the cell so that monitoring equipment may 5
be moved around the cell perimeter.
The vault system may include two rows of vault cells
that are separated by a loading aisle used both for load-
ing and unloading radioactive waste from the cells.
Preferably, one of the cells is left empty after all of the 10
other cells have been ftlled with radioactive waste. This
empty cell provides a space within the vault system for
temporarily "parking" the contents of a filled vault cell
in which a leakage condition has been detected so that
a maintenance or repair operation may be conveniently 15
conducted in the leaking cell. The loading aisle includes
a floor slab and a ceiling slab substantially coplanar with
the floor slabs and ceiling slabs of the vault cells. The
loading aisle remains empty after all the vault cells have
been loaded to afford a clear accessway to every cell in 20
the event a cell repair becomes necessary. Vault cells in
the same row are mutually separated by means of ex-
pansion joints so as to render individual cells relatively
movable with respect to each other in the event of a
seismic disturbance or ground settling. Such relative 25
movability avoids the generation of wallcracking
stresses which could occur if the cells were rigidly
interconnected. Similarly, expansion joints are placed
between the two rows of vault cells and the floor and
ceiling slabs of the loading aisle assembly to render the 30
loading aisle assembly independently movable with
rC!Ipect to the vault cells.
In the method of the invention, the floor slab of a cell
is first constructed within a below grade recess in the
earth, and an elongated wall assembly is constructed 35
over the floor slab that has a back wall and a front wall
at either end.. In the preferred embodiment, the wall
assembly is formed from a rectangular array of inte-
grally formed, concrete walls wherein the length ofthis
wall assembly is preferably five times as long as its 40
width. An accessway for loading radioactive waste
within the wall assembly is provided in the front wall
preferably at the time that the front wall is fabricated by
the pouring of concrete into a wall-shaped form. A
monolithic ceiling slab is then constructed which is 45
supported by the upper periphery ofthe wall assembly.
An earth cap is then placed over the ceiling slab in
order to complete the construction of an individual
vault cell.
Prior to fllling the vault cell with radioactive waste, 50
the cell is inspected for any structural faults which may
have occurred after the ceiling slab and the earth cap
have applied their respective weights to the wall assem-
bly. Next, the vault cell is loaded with radioactive waste
from its back end to its front end. In the preferred 55
method of the invention, the radioactive waste is pack-
aged into stackable units such as the hexagonally shaped
SUREPAK ® modules developed by the Westing-
house Electric Corporation. These units are stacked
into rows which are parallel to the back wall, the rows 60
being formed sequentially from the back wall toward
the front wall so that the waste in the frontmost row
shields the area in the vault cell between the waste in
the front wall from radiation emitted by the rows of
waste behind it. This stacking procedure, coupled with 65
the elongated shape of the wall assembly, substantially
reduces the amount of radiation absorbed by the per-
sons implementing the waste loading operation.
After a particular vault cell is completely fllled with
radioactive waste, the removable wall structure is as-
sembled over the accessway by stacking up a plurality
of T-shaped, interfitting concrete blocks. A permanent
wall having a frangible portion may then be constructed
over the removable wall structure at some future time
after which access to the disposal cell is no longer re-
quired.
The foregoing system and method effectively keeps
rain water out of the vault system during the loading
operation since each vault is completely enclosed with
its own sealing at the time it is loaded. Additionally, the
side loading afforded by the accessway and the wall
assembly substantially reduces the chance of a waste
container rupturing as the result of an accidental drop-
ping of such a container, since cranes are not used to
lower such containers down within the vault cells.
Man-rem exposure is also substantially lessened due to
the radiation minimizing elongated geometry of each of
the vault cells, and the a shielded forklift to load the
vault cells. The fact that the ceiling slabs are supported
by the wall assemblies instead of the waste itself allows
the vault cells to be thoroughly inspected before being
loaded, thereby giving the system operators ample op-
portunity to correct water-leaking structural faults
which may have occurred during construction. Finally,
the provision of expansion joints between all of the
components of the vault system and the independent
movement of each of these components afforded
thereby substantially reduces the chances of wall frac-
tures from occurring from localized stresses in the event
of a seismic disturbance or ground settling forces.
BRIEF DESCRIPTION OF THE SEVERAL
FIGURES
FIG. 1 is a perspective view of the inspectable vault
system embodying the invention;
FIG. 2 is a plan view ofthe vault system illustrated in
FIG. 1, illustrating the parallel configuration ofthe two
rows of vault cells that form the vault system;
FIG. 3 is an enlarged plan view of the vault system
illustrated in FIG. 2, illustrating some of the layers of
the earth cap that cover the individual vault cells of the
system;
FIG. 4 is a cross-sectional view of the vault system
illustrated in FIG. 3 along the line 4-4;
FIG. SA is an enlarged cross-sectional side view of
the vault system;
FIG. 5B is an enlarged cross-sectional side view of
the loading aisle of the vault system illustrated in FIG.
5B;
FIG. 5C is an enlarged plan view of the vault system
with the earth cap and ceiling slabs removed therefrom;
FIG. 6A is another plan view of the vault system as
shown without either the earth cap, the ceiling slabs, or
the waste modules so that the gridwork of drainage
channels and feeder channels present in the ceiling slabs
of each vault cell may be easily seen;
FIG. 6B is an enlarged cross-sectional side view of
one of the drainage or feeder channels in a ceiling slab
of a vault cell;
FIG. 6C is an enlarged cross-sectional end view of
the access tunnel of the drainage system which allows
the system operators to obtain access to both the pri-
mary and secondary drainage conduits and the manifold
which interconnects them, and
FIG. 7 is a partial cross-sectional side view of the
access tunnel of the drainage system, illustrating the

5
4,955,983
6
liquid collection tank connected to the manifold conduit
of the drainage system.
loading of waste containers therein. The balance of the
front wall 26 is formed from a removable wall structure
32 formed from interfitting concrete blocks 34, and a
permanent wall36 ofpoured concrete which covers theDETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENT S removable wall structure 32 after the cell 5 has been
completely filled with containers of waste. In the pre-
ferred embodiment, both the floor slab 18 and all of the
components of the wall assembly 22 are formed from
With reference now to FIGS. 1 and 2, wherein like
numerals designate like components throughout all of
the several figures, the inspectable vault system 1 of the
invention is generally comprised of two parallel rows
3a,3b ofvault cells S, each ofwhich preferably includes 10
twenty-five cells a piece. The two rows 3a,3b of vault
cells S are separated by a loading aisle 7 that provides
access to the side-opening present in each cell S. One of
the rows 3b of vault cells S includes one cell 8 which
remains empty after all of the remaining vault cells S 15
have been filled. As will be described in more detail
hereinafter, the empty cell 8 provides valuable tempo-
rary "parking" room for the waste container stacked
within one ofthe other vault cells S when it is necessary
to service a leak condition occuring in one ofthe loaded 20
cells S, Both of the rows 3a,3b of cells S are subterra-
nean, being placed within a recess 9 in the earth which
may be either a natural below-grade topological feature
or formed by excavation. The two rows 3a,3b of cells S
are covered by an earth cap 11 formed in part from 25
water-shedding compacted clay and a geomembrane
material. A drainage system 13 for removing water and
other liquids which may collect within the vault system
1 circumscribes the two rows 3a,3b ofvault cells 5. The
drainage system 13 generally includes an ~cess tunnel 30
1S that allows a system operator to access a liquid mani-
fold that communicates with each of the vault cells 5.
Manholes 16 are provided at the ends of the access
tunnel 1S to allow a system operator to climb under-
ground into the tunnel 15. 35
With reference now to FIGS. 3, 4 and SA, each ofthe
vault cells 5 of the system 1 includes a floor slab 18
which is preferably approximately one meter thick. As
is best seen in FIG. 4, the floor slab 18 of each cell 5 is
sloped with respect to the horizontal H to encourage 40
water or other liquids which may collect within the
cells to drain toward the drainage system 13. A rela-
tively small slope ofapproximately one to three percent
should be sufficient for such drainage purposes. Each
floor slab 18 is also sloped in the direction transverse to 45
the "down hill" slope evident in FIG. 4 so that any
liquids collected within the cells S will flow toward a
specific comer of the cell 5. Of course the floor slab 18
should be formed from a substance which is relatively
liquid impermeable, such as hardened concrete. 50
As is best seen with respect to FIGS. SA and SB, the
floor slab 18 of each individual vault cell 5 rests on top
ofa gravel drain layer 19 which in tum overlies a water
impermeable geomembrane 20 that may be formed from
polyvinylchloride or other appropriate hydrophobic 55
material. Geomembrane 20 in tum lies over a com-
pacted layer ofclay 21 which is preferably at least about
one meter thick. The purpose of all of the underlying
floor layers 19, 20 and 21 is, ofcourse, to encourage any
liquids which may seep through the floor slab 18 of a 60
particular cell S to flow into the drainage system 13.
With specific reference now to FIG. SC, each of the
vault cells 5 includes a wall assembly 22 which circum-
scribes the edge of the floor slab 18 and is preferably
integrally formed therewith. The wall assembly 22 in- 65
eludes a back wall 24, a front wall 26 and a pair of side
walls 28a,28b. An accessway 30 subsumes all but the
side edges of the front wall 26 in order to facilitate the
steel reinforced concrete. Additionally, to facilitate
access to the interior ofthe vault cell S after the remov-
able wall structure 32 and the permanent wall 36 have
been installed, the permanent wall 36 includes a frangi-
ble section 38 approximately one meter square and lo-
cated in an upper comer of the permanent wall 36 as
indicated. As will be discussed in more detail hereinaf-
ter, the frangible section 38 allows a comer of the per-
manent wall 36 to be neatly broken out in the event that
the system operators wish to install a movable video
camera within the cell 5.
With specific reference again to FIG. SB, each of the
vault cells 5 is provided with a ceiling slab 40 formed
from a unitary section of reinforced concrete that is
completely supported by the upper edges of the wall
assembly 22. The front edge of the ceiling slab 40 in-
cludes a support ledge 42 for supporting the ceiling slab
of the loading aisle 7 which will be discussed in detail
shortly.
With reference now to FIGS. SA, SB and SC, expan-
sion joints 44 are provided between the side walls
28a,28b of adjacent vault cells 5 so that each individual
vault cell 5 may move in response to subsidence or
seismic disturbances without necessarily applying large
stresses on its neighbor cells. While the dimensions of
the walls and the proportions of the vault cells 5 may
vary considerably and still fall within the purview of
the instant invention, the floor slab 18, back and front
walls 24,26 ofthe wall assembly 22, and the ceiling slab
40 are each preferably one meter thick, while the side
walls 28a,28b of adjoining cells 5 are each approxi-
mately 0.5 meters thick. Side walls 28a.28b which are
not adjacent to the side walls of another cell 5 are pref-
erably one meter thick as may be seen to side wall 28b
in FIG. SC. In the preferred embodiment, the length of
each ofthe cells 5 is preferably about five times the cell
width, for two reasons. First, such proportioning cre-
ates a favorable shield geometry when the system oper-
ator fills the vault cells 5 with radioactive waste by
stacking it from the back wall 24 toward the front wall
26. This is due to the fact that the frontmost row of
waste containers effectively blocks much, if not all, of
the radiation emitted by the other rows of waste con-
tainers stacked behind the frontmost row. Second, such
proportioning minimizes the sag experienced by the
ceiling slab due to the relatively distance between the
side walls 28a,28b which support it. This is an important
advantage, as the ceiling slab 40 must not only support
its own weight, but also the weight of the earth cap 11.
In the preferred embodiment, each cell 5 is approxi-
mately 16X95 meters.
As may best be seen in FIG. SB, the earth cap 11
which covers the ceiling slab 40 includes a water imper-
meable geomembrane cover 46 which overlies the
upper surface of the ceiling slab 40, and a layer 48 of
compacted clay approximately 0.66 meters thick which
in turns overlies the geomembrane cover 46. The princi-
pal purpose of both the cover 46 and the clay layer 48
is, of course, to shed water away from the vault cells 5.
The earth cap 11 further includes a water permeable

7
4,955,983
8
geotextile 50 which covers the upper surface ofthe clay
liner 48, as well as a filtered drainage layer 52 consisting
ofsand and gravel approximately 0.66 meters thick with
overlies the geotextile fabric 50. Another layer ofwater
permeable geotextile 54 covers the upper surface of the 5
filtered drainage layer 52 so that the layer 52 is, in ef-
fect, "sandwiched" between the geotextile layers 50 and
54. A layer 56 ofnative soil overlies the geotextile layer
54 as shown. The purpose of the filtered drainage layer
52 and the two layers 50 and 54 of geotextile is to rap- 10
idly drain any water or other liquid which should per-
meate the native soil layer 56 so that the clay layer 48
and the geomembrane cover 46 may rapidly shed such
water away. The structure of the loading aisle 7 is also
clearly evident in FIG. SB. Like the previously dis- 15
cussed vault cells 5, the loading aisle 7 also includes a
floor slab 60 which overlies the previously discussed
gravel drain layer 19, geomembrane 20, and compacted
clay layer 21. A drain 62 is centrally disposed along the
longitudinal axis of the floor slab 60. This drain 62 may 20
take the form of a shallow trough approximately five
centimeters deep and ten centimeters wide that is
molded within the floor slab 60. Finally, the loading
aisle 7 includes a ceiling slab 64 not unlike the ceiling
slabs 40 of the vault cells 5. These ceiling slabs 64 are 25
supported by the previously discussed ledges 42 which
form an integral part of the front edges of each cell
vault ceiling slab 40. In the preferred embodiment, the
loading aisle 7 is 10-11 meters wide. As may best be
seen in FIGS. 5C and 6A, the interior of each of the 30
vault cells 5 is preferably loaded with a stacked array 67
of modular, interfitting waste containers 69 which, in
the preferred embodiment, are hexagonal SURE-
PAK® modules developed and patented by the Wes-
tinghouse Electric Corporation. The array 67 of waste 35
containers 69 is spaced approximately 0.66 meters away
from the inside surfaces ofthe wall assembly 22 in order
to provide a monitoring aisleway 71 which is suitable
for either a man or a monitoring device to move in.
Moreover, a track 73 is preferably attached around side 40
wall 28a, back wall 24, and side wall 28b as shqwn at a
height which is approximately level with the top of the
array 67. The purpose of the track 73 is to guide a mo-
torized video camera 75 around the monitoring aisle-
way 71 in the event that a monitoring or a maintenance 45
operation is necessitated within the interior of the vault
cell 5. The preferred method of installing such a video
camera 75 onto the track 73 is, ofcourse, to remove one
or more of the interfitting blocks 34 that forms the
removable wall structure 32 before the permanent wall 50
36 is installed, and to remove frangible section 38 and
one or more blocks 34 after wall 36 is installed.
While there are many advantages associated with the
use of SUREPAK ® modules in conjunction with the
vault cells 5, one advantage that should be expressly 55
recognized is the fact that the physical dimensions of
the SUREPAK ® modules allows the provision of the
0.66 meters wide monitoring aisleway 71 without any
danger that a waste container 69 will fall into the aisle-
way 71 from the effect of a seismic disturbance. This 60
arises from the fact that the diameter of the SURE-
PAK@ modules (which is approximately two meters)
is over three times the width ofthe monitoring aisleway
71. Hence there is essentially no chance that any of the
modules 69 will fall into the aisleway 71 and rupture on 65
the floor slab 18 if the containers 69 are stacked in the
mutually-contiguous array 67 shown. If the waste con-
tainers 69 were made to be relatively small relative to
the width ofthe monitoring aisleway 71, it is easy to see
that one or more ofsuch containers 69 could indeed fall
into the monitoring aisleway 71.
Turning now to FIGS. 6A, 6B and 6C, the drainage
system 13 includes, for each vault cellS, a central drain-
age channel 80 disposed along one edge ofthe floor slab
18 of each cell 5 as shown. As has been previously
indicated, the floor slab 18 of each vault cell 5 is sloped
at least one percent with respect to both its length and
its width so that any liquids which collect upon the
floor slab 18 tend to run toward one of the side edges of
the slab 18. The drainage channel 80 is, of course, lo-
cated along this lowest edge of the slab 18. In addition
to the drainage channel 80, the system 13 includes a
grid-like network of feeder channels 82 which ulti-
mately empty into the main drainage channel 80. This
gridwork of feeder channels 82 divides the area of the
floor slab 18 into a plurality of rectangular zones of
which 83a,83b are exemplary. Each ofthese zones are in
turn drained by a separately identifiable feeder channel
84a,84b, respectively. The advantage of such a configu-
ration of feeder channels 82 is that it allows the system
operator to infer which zone or zones a leakage condi-
tion has occurred by merely noting which of the feeder
channels 83a,83b is conveying water or other liquid to
the drainage channel 80. Because the drainage channel
80 and its interconnections with the feeder channels 82
are incorporated within the monitoring aisleway 71, the
system operator may utilize the previously described
motorized video camera 75 to tell him which of the
feeder channels 82 is conveying liquid to the main drain-
age channel 80 since wet concrete is substantially
darker than dry concrete. In the alternative, electronic
moisture sensors that generate remotely receivable sig-
nals maybe placed at the junctions between the feeder
channels 82 and the main drainage channel 80.
With reference now to FIG. 6C and FIG. 7, the
drainage channel 80 of each of the vault cells 5 is con-
nected to a primary cell drainage conduit 86 which in
turn is connected to a manifold conduit 90. Also con-
nected to the manifold conduit 90 is a secondary drain-
age conduit 88 which is disposed beneath the floor slab
18 of each of the vault cells 5. The purpose of each of
the secondary drainage conduits 88 is to drain any water'
or other liquids which may collect within the gravel
layer 19 and geomembrane 20 which exist beneath the
floor slabs 18 of each cell 5. Such liquid might collect
within the gravel layer 19 as the result of a crack in the
floor slab 18, or as the result of a substantial rise in the
subterranean water table.
A moisture detector 94 is disposed in each oftwo pipe
segments which separately interconnect the ends of the
primary and secondary drainage conduits 86 and 88
with the manifold conduit 90. The moisture detector 94
may take a variety of forms. In one embodiment of the
invention, the moisture detector 94 is simply a float
disposed within a transparent elbow. In the alternative,
moisture detector 94 may be any one of a number of
commercially available electronic devices. A sample
collection tap 96 is also provided at the end ofboth the
primary and the secondary drainage conduits 86 and 88.
These taps 96 allow an operator walking within the
access tunnel15 to obtain a sample ofany liquid leaking
out either over or under the. floor slab 18 so that the
composition and radioactivity of the liquid may be
tested. The ends of both the primary and secondary
drainage conduits 86 and 88 also include a clean out

9
4,955,983
10
port 98 so that the sediment or other obstructing mate-
rial may be conveniently removed from these conduits.
With reference now to FIG. 7, the manifold conduit
afforded by the elongated shape of each of the vault
cells 5. Additionally, the waste containers 69 are advan-
tageously sheltered from the ambient weather during
the loading operation (which may take as long as six90 to which the primary and secondary drainage con-
duits 86 and 88 ofeach ofthe vault cells 5 are connected
ultimately drains into a liquid storage tank 100. A cou-
pling 104 interconnects the terminus of the manifold
conduit 90 with the tank 100. The tank 100 is further
provided with a suction conduit 106 so that any liquid
which collects therein may be conveniently and period-
ically removed. Additionally, electronic moisture de-
tectors 108a,108b are provided at the lower portion of
the collection tank 100 and at the terminus of the mani-
fold 90, respectively. Each of these moisture detectors
108a,108b generates an electronic signal when liquid is
detected either at the terminus of the manifold 90, or at
the bottom of the collection tank 100. This signal may
5 months) thereby minimizing the amount of stray rain
water which collects within the cell 5.
After a particular cell 5 has been fully loaded, the
removable wall structure 32 is then constructed by
stacking the plurality of interfltting blocks 34 into the
10 configuration illustrated in FIG. 5B. When all the cells
5 of the system 1 have been completed and loaded, the
permanent wall 36 of each is fabricated out of steel
reinforced concrete, being careful to provide fracture
lines and no reinforcement around the edges of frangi-
15 ble portion 38.
be remotely detected, as by for example a radio receiver
of a data acquisition system, so that the system opera-
tors will know immediately when a leakage condition 20
has occurred in one or more ofthe vault cells 5 without
.the necessity ofmanually inspecting the moisture detec-
tors 94 disposed within the tunnel 15. Finally, a liquid
level sensor 110 is provided within the collection tank
100. This liquid level sensor 110 likewise generates a 25
remotely-receivable signal when the level of the liquid
within the tank 100 rises above a predetermined level,
thus alerting the system operators of the necessity of
emptying the tank 100.
In the preferred method ofthe invention, the inspect- 30
able vault system 1 is constructed by first providing a
recess in the earth, which may be either natural or
formed by an excavation. Next, the compacted clay
layer 21 is deposited over the recess, with the geomem-
brane 20 and gravel drain layer 19 following. The floor 35
slab 18 of at least one vault cell 5 is then constructed.
Thereafter, a wall assembly 22 is erected around the
edges of the floor slab 18. Next. a ceiling slab is con-
structed over the top edges of the wall assembly 22.
Following this, the track 73 is next installed around the 40
interior of the wall assembly 22 in the configuration
illustrated in FIG. SC. After four disposal cells 5 have
been constructed, the various layers of the earth cap 11
are then deposited over the ceiling slab 40 of each.
At this juncture, all of the static loads that the vault 45
cell 5 is expected to bear have been applied to each cell
5. It is therefore appropriate that a close inspection be
made of the interior of each constructed vault cell 5 to
make sure that there are no water conducting cracks or
other structural flaws present therein. This is a rela- 50
tively simple matter, since there is no radioactive waste
within the cells 5 at this point, and since further the
removable wall structure 32 and permanent wall 36 of
the front wall 26 of each have not yet been built.
Concurrently with the construction of the vault cells 55
5, the floor slab 60 of the loading aisle 7 is also built so
a5 the provide a clear and supporting surface for a
shielded forklift to stack the previously described
SUREPAK ® modules within the vault cell 5.
If the vault cells 5 pass inspection after the earth cap 60
11 has been deposited thereover, radioactive waste is
next loaded therein. The waste containers 69 are
stacked in uniform rows from the back wall 24 toward
the front wall 26 of each vault cell 5 until a densely
stacked array 67 such as that illustrated in FIG. 5C is 65
formed. During the waste loading operation, the system
operators receive a minimum amount ofradiation expo-
sure due to the previously described shielding geometry
Both ofthe rows 3a,3b of vault cells 5 are built simul-
taneously in parallel, rather than completing one row 3a
and then the other row 3b. Such parallel construction
provides two opposing ledges 42 onto which the ceiling
slab 64 ofthe loading aisle 7 may be built, which has the
advantage ofproviding a water-shedding ceiling over at
least part of the loading aisle 7.
In the event that one or more of the moisture detec-
tors ofthe drainage system either remotely or manually
indicates that a leakage condition has occurred within
one of the cells 5 before permanent wall 36 has been
fabricated, the system operators may lift out some ofthe
interfltting blocks 34 that form the upper comer of the
removable wall structure 32. A motorized video camera
75 may then be installed onto the track 73 in order to
discover the specific zone 83a,83b where the leakage
occurred. If the system operators decide that it would
be necessary to remove the waste container 69 from a
particular vault cell in order to repair a leakage condi-
tion, the wall34 would be completely removed, and the
contents of the damaged cell 5 would be temporarily
moved into the empty cell 8 until the repair was com-
pleted, wherein upon the containers 69 could be re-
loaded into the repaired cells and the wall structure 32
and the interfltting blocks 34 reconstructed. Of course,
the same procedure could be implemented after perma-
nent wall 36 has been fabricated, albeit with somewhat
more trouble, as the wall 36 of the leaking cell would
have to be removed. Thus the invention provides an
inspectable vault system in which structural flaws may
be detected and corrected before any waste is loaded
into any of the cells S, and in which a drainage system
tells the system operators of the occurrence as well as
the location of a leakage condition. The invention also
provides a system in which the contents of a damaged
cell 5 may be conveniently and temporarily stored
within an empty cell 8 until a repair has been effected.
While the preferred embodiment of the invention is
installed within a recess in the earth, the vault system of
the invention may also be constructed and used above
ground as well.
We claim:
1. A method for the disposal ofhazardous radioactive
waste, comprising by steps of:
a. constructing a floor slab in the earth;
b. constructing an elongated wall assembly over said
floor slab having sidewalls and a front wall and a
back wall at either end said side walls being longer
than said front and back walls;
c. providing an accessway in said front wall;
d. constructing a ceiling slab over said wall assembly
that is supported at least in part by said wall assem-
bly to form a vault cell;

4,955,983
1211
e. inspecting the vault cell for structural defects, and
f. introducing hazardous radioactive waste through
the accessway in said front wall and loading said
cell with said waste from the back wall to the front
wall in rows, each of which is substantially parallel S
to said back wall to minimize radiation exposure to
workers loading the cell, and
g. closing the accessway of the vault cell by con-
structing a removable wall structure within the
accessway.
2. A method as defmed in claim 1, further including
the step of providing an earth cap over said ceiling slab
prior to inspecting the resulting vault cell for structural
faults.
10
3. A method as defined in claim 1, wherein said re- 15
movable wall structure is constructed in said accessway
by assembling a plurality of mutually interfitting wall
elements.
11. A method for disposal of radioactive waste as
defmed in claim 9, wherein said waste is packaged in
discrete units, and wherein said waste is loaded within
the vault cell by stacking said waste units into rows
which are parallel to said back wall, said rows being
formed sequentially from the back wall toward the
front wall so that the waste in the frontmost row shields
the area ofthe cell between the waste and the front wall
from radiation emitted by the rows of waste behind it.
defmed in claim 9, wherein space is left between the
inner walls ofthe vault cell and the waste loaded therein
to form an access aisle for monitoring equipment.
defmed in claim 9, further comprising the steps of con-
structing two parallel rows of vault cells by repeating
steps (a) through (e) for each additional cell, wherein
the space between each ofsaid rows ofsaid cells defmes
a loading aisle.4. A method as defmed in claim 1, further comprising
the step of constructing two parallel rows of vault cells 20
separated by a loading aisle.
defmed in claim 13, further comprising the steps of
. constructing a ceiling slab over said loading aisle, and
providing an earth cap over said loading aisle ceiling
slab.
5. A method as defmed in claim 4, further comprising
the steps ofconstructing a ceiling slab over said loading
aisle, and providing an earth cap over said loading aisle
ceiling slab. 25
6. A method as defined in claim 4, wherein one ofsaid
vault cells is left empty to provide space for depositing
the contents ofanother vault cell ftlled with waste in the
event it becomes desirable to empty said other vault cell
of its contents. 30
7. A method as defmed in claim 1, wherein space is
left between the inner walls of the vault cell and the
waste loaded therein to defme an aisleway for monitor-
ing.
8. A method as defmed in claim 1, wherein said waste 35
is radioactive and is packaged in discrete units, and said
vault cell is loaded by stacking rows of said waste units
parallel to said back wall to minimize radiation exposure
to workers.
9. A method for the disposal of radioactive waste, 40
characterized by the steps of:
a. constructing a floor slab within a recess in the
earth;
floor slab having sidewalls and a front wall and a 45
back wall at either end said sidewalls being longer
than said front and back walls;
c. providing an accessway in said front wall;
d. constructing a ceiling slab over said wall assembly
that is supported at least in part by said wall assem- SO
bly to form a vault cell;
e. providing an earth cap over said ceiling slab;
f. inspecting the vault cell for water conducting struc-
tural defects, and
g. introducing radioactive waste through the access- ss
way and loading said cell with said waste from the
back wall to the front wall in rows, each of which
is substantially parallel to said back wall to mini-
mize radiation exposure to workers.
10. A method for disposal of radioactive waste as 60
defmed in claim 9, wherein said waste is packaged in
discrete units is loaded in rows within the vault cell,
each of which is parallel to the back wall, said rows
being formed sequentially from the back wall toward
the front wall so that the waste in the frontmost row 65
shields the area of the cell between the waste and the
front wall from radiation emitted by the rows of waste
behind it.
def'med in claim 13, wherein one ofsaid vault cells is left
empty to provide space for depositing the contents of
another vault cell filled with waste in the event it be-
comes desirable to empty said other vault cell of its
contents.
defmed in claim 13, further comprising the step ofinter-
connecting the vault cells through expansion joints to
structurally integrate the rows of vault cells while still
allowing some stress relieving movement to occur be-
tween different vault cells.
17. A method for the disposal of radioactive waste
within a vault system formed from individual vault
cells, comprising the steps of:
a. constructing a floor slab in the earth;
floor slab having sidewalls a front wall and a back
wall at either end, the length ofsaid sidewalls being
at least two times as long as its width;
c. constructing a ceiling slab over said wall assembly
that is supported by said wall assembly to form a
vault cell;
d. providing an earth cap over said ceiling slab;
e. inspecting the vault cell for structural defects, and
f. loading radioactive waste into the vault cell
through the accessway in the front wall by stacking
said waste in rows each of which is parallel to the
back wall, said rows being formed sequentially
from the back wall toward the front wall so that
the waste forming the frontmost row shields the
area of the cell between the waste and the front
wall from radiation emitted by the rows of waste
behind it.
18. A method for the disposal of radioactive waste as
defined in claim 17, wherein the waste is packaged into
units which are mutually stackable and mutually inter-
fitting to form a substantially solid array of waste units.
defmed in claim 17, further including the step of closing
the accessway ofthe vault cell by constructing a remov-
able wall structure in said accessway.
defmed in claim 19, wherein said removable wall struc-

13
4,955,983
ture iS constructed in said accessway by assembling
plurality of mutually interfitting wall elements.
21. A vault system for the disposal of radioactive
waste formed from at least one vault cell that comprises:
5
a. a floor slab disposed within a recess in the earth;
b. a ceiling slab disposed over said floor slab, and
c. an elongated wall assembly disposed around the
periphery of said floor slab for supporting said
ceiling slab including sidewalls and a back wall and 10
a front wall, said front wall having an accessway
for loading radioactive waste within the wall as-
sembly, wherein the elongated shape of the wall
assembly reduces the amount of radiation present
15
in the area of the cell between the waste disposed
therein and the front wall accessway when the
· waste is loaded from the back wall to the front wall
of the cell, and
d. an aisleway defmed between the inner side wall 20
assembly and the waste loaded within the vault cell
for accommodating monitoring equipment.
waste as defined in claim 21, wherein said vault system
includes two rows of said vault cells that are separated 25
by a loading aisle for loading and unloading radioactive
waste from said cells.
waste as defmed in claim 22, wherein said loading aisle 30
includes a floor slab and a ceiling slab that are substan-
35
40
45
so
55
60
65
14
tially coplanar with the floor slabs and ceiling slabs of
the vault cells.
waste as defmed in claim 22, wherein adjacent vault
cells are interconnected by means of expansion joints to
allow relative stress relieving movement between said
cells.
.25. A vault system for the disposal of radioactive
waste as defmed in claim 23, wherein said floor and
ceiling slabs of said loading aisle are interconnected to
said rows of vault cells by means of expansion joints to
allow relative stress relieving movement therebetween.
waste as defmed in claim 22, wherein one of said vault
cells is empty to provide a space in said vault system for
depositing the contents of a vault cell filled with waste
in the event it becomes desirable to empty said fl.lled cell
of its contents.
waste as defmed in claim 21, wherein the length of each
vault cell is at least twice as long as its width to reduce
the amount of radiation in the area of the cell between
the waste disposed therein and the front wall access·
way.
waste as defmed in claim 21, wherein the length ofeach
vault ceil is at least five times as long as its width to
reduce the amount of radiation in the area of the cell
between the waste disposed therein and the front wall
accessway.
* * • • •

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