CA1246879A - Nuclear waste disposal site - Google Patents

Abstract

ABSTRACT

A land disposal site for the disposal of nuclear waste is disclosed which generally comprises a trench, a non-rigid, water-shedding cap formed from allumium and silt which overlies this depression, and a solid array of waste-containing modules disposed in the trench for both encapsulating the waste and for supporting the non-rigid cap over the depression. The floor of the trench preferably includes a capillary barrier formed from a layer of gravel so that ground water will not seep up into the modules buried within the disposal site. The top surfaces of the modules are covered with a sloped layer of alluvium, which in turn is covered with another capillary barrier of gravel. This capillary barrier of gravel carries a sloped layer of silt which sheds running surface water and directs it into a pair of drains disposed on either side of the trench. The silt layer is capped with a final barrier of graded rip-rap which protects it from wind and water erosion, and which forms a natural radiation and intrusion barrier.
Finally, the modules disposed within the disposal site are preferably uniformly shaped, hexagonal prisms which are capable of being solidly packed into a structure which is flexibly conformable with any changes in shape of the trench brought about by seismic or other natural disturbances.

Description

~L~46ls7~ 52, 109 Tl TLE OF THE I 1~1 VEN T~ Ol\' NllCLEAR ~ASTE DISPOSAL SITE

BACKGROI~iD OF THE I~lYENTION

Fie]d of the Invention This invention generally relates lo a land disposal site fs r nuclear ~astes having a non-Etructural CAp supported b~ a solidly packed arr! of waste-containing modules unich are arranged to be fle~ibly conformable with changes in the shape of the site brought about b~ seismic events or other natural disturbances.

Description of the Prior Art Buria] systems for burying nuclear whste are known in the prior art. In the earliest of these systems, such astes were merely packed into 55-ga~30n steel drums, dropped into a simple, earthen trench b~ a long-boom crane, and buried. I~nfortunatel~r, such "kick and roll" burial systems proved to be generally unsatisfactory for the land disposal of nuc]ear aste. The ]oose soil which Ihese trenches were filled in w as much more permeable S~
to ~-ater than the densely-packed soil which formed the ~ of the ~rench, or the dense rock strata uhich typically formed the bottom of the trench. Consequently, the relative~y loose and uater permeable soil which surrounded the drums caused these trenches to col]ect large amounts of standing water in what is known as lhe "bathtub effect". This standing water ultimately caused the steel w alls of the drums buried within the trenches to corrode and collapse. The collapsing drums and compactjon of the soil over time resulted in a do~n- ard movement or subsidence of the soil, hich caused a depress;on to form over the top of the trench.
This depression in turn collected surface water and hence worsened the tendency of the trench to collect and maintain a pool of standing water over the drums. The resulting increase in standing water resulted in still more soil subsidence and accelerated the corrosion and col~apse of the drums buried therein.
The corrosion and collapse of the drum containers in such sites ~4687~

resu3ted in some radioactive contamination of the ground water flowing therethrough.
To solve the soil subsidence and water accumulstion problems assDciated with such "kick and roll" disposal sites, a variety of alternative burial systems have been developed. These ~ternatives inc]ude earthen vaults having structurally rigid walls, and container burial sites u~hich the spaces between the waste containers are filled in uith concrete or some other hardenable grout . ~ hile these alternative systems constitute c]ear advances over the trenches used in the simp]e "kick and roll" dîsposal systems, various shortcomings are associated with both. For example, ~here earthen vau]ts are used which incorporate structurally rigid walls, such rigid walls are apt to crack and break in resporlse to a seismic disturbance. Once the integrity of the vault alls is gone, ground ~ater can ~low in and accumulate around the ~.asle packages. If s~?y of these packages has metallic ~;alls, the standing ualer surrounding them can cause the walls to corrode and ]each radioactive waste into the ground uater.
Because such vaults typically hgve only one access opening, the recoverability of a single, ]eahing package would be extremely difficult, if not impossible. While burial sites in which a hardenable substance is poured over a large group of waste containers to form a solid, integral monolith may be more resistant to craching or breakage due to seismic disturbances, this particu]ar type of disposal site would tend to place very high, ]oc&lized stresses on the ~:aste containers ]ocated in the paths of any faults or cracks which develop in the monolith. Morecver, this type of site has ~n even worse prob]em with recoverability when a seismic disturbance does succeed in rupturing only a few or one of the containers encapsulated in the grout. A relocstion of the site mi;~ht be the only solution if such a cracking or breaking of the inaccessible containers occurred.
C]early, a need exists for a disposal site which is structurally stable, yet ~exible conformable to seismic events or other natural 3 5 disturbances, so that no localized 9 container-cracking stresses can occur. Additionally, it would be desirable if the individual containers buried in such a site were easi]y and conveniently recoverable in order to obviate relocating the entire site should a seismic event or other natur~ disturbance break a few or only one of the containers buried therein. Further, the burial site should have means for preventing the accumulation of standing water around the array of containers to insure the longevity of the containers buried therein. Finally, it would be desirable if such a site were easi]y constructed of inexpensive materials.

SUMMARY OF THE INVEI~lTlON
In its broadest sense, the invention is a nuclear - aste disposal site which generally comprises a depression in the earth, a non-rigid, water-shedding cap overlying this' depress;on, and an array of modules disposed in the depression and under the cap for both enc2psulating the waste ~^rom whter and for supporting the l 5 non-rigid cap over the depression . Preferably, the cap includes a ]ayer of natural silt for shedding surface water av~ay from the depression in order to prevent ater from accumulating around the modu]es buried ~ithin the disposal site. Additionall~, a layer of coarse, granular material having a high hydraulic conductivity may be placed between the tops of the modules and the underside of the silt layer fo'r preventing waler from seeping through the si]t layer and onto the nJodules by capillary action. ln the preferred embodiment, the coarse, granular material used in this layer is gravel. Further, & ]ayer of graded rip-rap may be p]aced over

2 5 the top surface of the silt ]ayer in order to prolect the silt from uind and v;ater erosion, and to provide both a radiation barrier and an intrusion barrier for the waste-con1aining modules contained ~ithin the disposa~ site.
The depression of the disposal site may be a flat-bottomed trench in the earth. The iloor of this trench may inc]ude a layer of coarse, granular, water conductive material such as gravel for preventing ground water from seeping up to the modules by way of capi~lary actio~. Additionally, a plurality of Iysimeters may be placed throughout the floor of the trench under the layer of 4L6E~7~
_q_ grsvel in order to col]ect sampies of water which may be later used to monitor the amount of radioactive leakage from the modules.
The modules used in the disposal site of the invention are preferabl~ in the shape of right-~ngled prisms which may be solidly stacked into layers which are mutually slidab]e over one another, as well as co]umnar stacks wherein each column is slidably movable in the vertical direction relative to the other columns. Such a solid~-pscXed arr~ngement affords a subsidence-free structure which is capable of supporting the non-rigid cap of the site, but u~hich is flexibly conformable to changes in the shape of the earth brought about by seismic or other natura] disturbances Finally, the invention a~so encompasses a process ~herein the cap of the site is constructed as the modu]es are solidly stacked within the trench or other depression in order to minirriize the amount of radiation lo hich the human orkers present in the disposal site are e~posed.

BRlEF DESCRlPT~Ol~ OF THE SE~ERAL FIGURES
Figure 1 is a perspective, cuta- ay vie~ of the packaging 2 0 facilit~ used in the system of the invention;
Figure 2 is a perspective, cutaway vie~ of the high-force compactor used in the packaging facility illustrated in Figure 1;
Figure 3 is a perspective, cutaway view of the disposal site of the invention;
2~ Figure 4A i5 a top, plan vie~ of the pac}iaging module of invention;
Figure 4B is a side, partial cross-sectional view of this module;
Figure 4C is a botl m view of the modu]e of the invention;
Figure 5A is a top vieH~ of the cap of the module of the invention;
Figure 5B is a side, partial cross-sectional view of the cap illustrated in Figure 5A;
Figure 6 is a perspective view of a packed and sealed module of the invention, and 37~

~5--Figure 7 is a perspective, cutaway view of a packed module of the invention.

DETAILED DESCRIPT]ON OF THE PREFERRED EMBODIMENT
H'ith reference now to Figure 1, wherein like reference numerals designate like components throughout all of the several figures, the psckaging facility 1 of the system of the invention generally comprises four iso]ation walls 2a, 2b, 2c and ?d which enclose a remoie handled waste packaging section 3 on the ]eft side of the building, a module ]oading and transportation section 60 in the center of the bui]ding, and a cont~ct hand3ed waste section 85 on the right side of the bui]din~. Both the remote and contact hand~ed waste sections 3 and 85 include a drive-through 7 and 87, respectively. At these drive-throughs 7 and 87, trucks 13 and 9 deliver r emote and contacl handled nuclear w aste in relatively lighlueight shipping containers (i.e., liners, 55-gallon drums, and LSA containels~ from remotely located aste generating sites for encapsu]ation into the relatively heavy, solidly packed modules 200. In the preferred embodiment, the fina~ disposal site 150 of the modu]es 200 packed by the packaging facility 1 is located in 2 0 close proximity to the facility 1 in order to minimize the distance ~- hich the packed modules 200 ( w hich may weigh over 30, 000 pounds) must be transported. At the outset, it should be noted that there are at least three major ~d~ antages associated with a facility surrounded by isolation walls which is remotely located frcm ~he w2ste-generating sites, yet is c]ose to a final disposal site 150. First, there is no need to trarlsport the relatively heavy modu]es 20U to the waste generating site. Second, the possibility of lhY waste-generating site from becoming contaminated from a I-~cl;~ging accident is eliminated. Thirdly, the isolation walls 2a, 2b, 2c and 2d minimize the possibility of the disposal site 150 ~ecoming contaminated from any packaging accidents.
Turning now to a more specific description of the remote-hand]ed waste section 3 of tl e facility ï, this section 3 ir3r!~ es F, dri Jeway 9 having an entrance (not shown~ and an exit 11 for r~ceiving a delivery truck 13. Such trucks 13 will normally carry their ]oads of nuclear uaste in a reusuable, shielded shipping cask 15 of the tj ~e approved by the U.S. Department of Transportation or the 11. S . Nuclear Reg ulatory Commission .
Disposed within such shie]ded shipping casks 15 are metallic or p]astic liners (not shown) which actually hold the wastes. Section

3 OI the facility 1 further includes a processing platform 18 which is about the same height as the height of the bed of the truck 13, a shie]d bell l9 having a hook assembly 21, and a remote-c~ntro]]ed traveling crane 23. The hie]d bell 15 is 1 û preferabl~ formed from a steel shell having a ]ead liner which is thick enough to reduce the amount of radiation emanated ~rom the non-contact u aste to an acceptible level. The crane 23 includes a primar~ hoist 25 detachably connectable to the hook assembl~ 21 of the shie]d bell 19 via an e]ectric motor-opersted pulley asserrIbly 2~. The traveling crane 23 further includes a carrisge 29 for mo~dng the pri~ary hoist 25 in the X direction (paralle3 to the dri~/ewa~ 9 of the drive-through 7), as well as 8 trol]ey 33 for moving the primar~ hoist 25 in a Y direction (paral~el to the front face of lhe facility l ) . The vertically adjustable, electric 2 o motor-operaled pul3ey assembly 27, in combination uith the carriage 29 and trolle~ 33, allows the traveling crane 23 to s~ing the shield be31 l9 over the shipping cask 15 of the delivery truck 13, pick up the waste-containing liner out of the cask 15, and p3ace the liner at a desired position onto the processing platform l8. Although a remote-control]ed traveling crane 23 operated via a T . V . monitor is used in the preferred embodiment, any number of other types of existing remote-controlled crane mechmisms may be used to irnp]ement the invention, In addition lo primary hoist 25, a secondary hoist 35 is also connected between the trsveling crane 3 and the shield bell 19. The secondary hoist 35 controls the position of a cable and hook (not shown) inside the shie~d bell 19 which is capable of detachably engag~ng the waste-containing liner disposed ~ithin the shielded shipping cask 15.
The remote-handled waste section 3 of the building 1 further 3, inc3udes a characterization station 3~ having various radistion detectors 39 and ultrasonic detectors 41 for verifying that the ~.~46879 contents of the liner inside the shipping cask 15 conform to the shipping n)anifest. The radiation detectors 39 sre used to measure the intensity of the radiatiGn emanating from the waste contained in the liner and to check the 'Isignature" of the radiation spectrum of this waste to confirm the accuracy of the shipping manifest.
The ultrasonic detectors 41 ~re used to determine whether or not any radioactive liquids are present within the liner. Federsl regulstions strickly prohibit the burial of radioactive ~astes in liquid ~^orm; consequently, the information provided by the ultrasonic detectors 41 is of paramount importance. Both the radiation detectors 39 and u]trasonic detec1Ors 41 are e]ectrically connected to a bank of read-out disls ~5 by means of cables disposed in grooves g3 in the processing platform 18. A]though not specifically shown in any of the several figures, the outputs of the radiation detectors 39 and the ultrasonic delectors 42 are preferabl3T fed into a central computer both ~or record-keeping purposes, and for determining hou much of a particular kind of waste can be ]oaded into a particular module before the surface radiation of the module 200 exceeds a pre-selected limit. The 2 0 central computer can further compute how much grout must be poured into a particular loaded module in order to properly encapsulate the uastes, and has the capacity to actuate an alarm circuit uhen the ultrasonic detectors 91 indicate that an unacceptable percentage of the uastes contained in the liner are in liquid form.
In the preferred embodiment, the height of the processing platform 18 is chosen to correspond approximately with the height of the bed of a trai~er truck 13 so that any human operators who may be present on the platform 18 when the lid is removed from the cask 15 will not be exposed to the radiation beaming out of the 10p of the cask. In operation, the shield bell 19 is lowered into the open cask 15, engages the liner contained therein, and then is swung over the sensors 39 and 41 of the characterization station 37 and quickly lowered to within ~ few inches of these sensors to minimi~e any of the exposure of section 3 to any radiation beaming out from the bottom of the shield bell 19 which re~lects off 46~75~

of the platform 18. In the preferred embodiment, the processing platform 18 is ~rmed from a solid ~lab of concrete both for the structural solidarity of the facility 1 as a who]e, as well as for shielding purposes. This last purpose will become e]earer after S the structure and function of the ]ag storage wells 50 i5 exp]ained hereinafter. While the chhracterization station 37 of the preferred embodiment inc]udes only radiation detectors 39 and u]trasonic detectors 41 and other types of detectors (such as remote T.V.
monitors for visually identifying the uaste) may a~so be included if 1 O desired.
Finally, the remote-handled v:aste section 3 of the facility 1 includes four ~ag storage wells 50, as well as a remedial action room 53 formed from shie~ded wPlls 54 and accessible through shielded doors 55. Each of the ]ag storage wells 50 includes a generally cylindrical well topped by a disk-shaped cover. The lag storage wells 50 provide a safe and convenient storage area for nuclear waste shipments in hich the characterization station 37 has detected the presence of liquids in excessive quantities or other unacceptable conditions. Additionally, the lag storage wells 2 0 may be used to temporarily slore shipments of remote-handled uastes when the grouting station 118 becomes backed up. The materials and thickness of the disk-shaped cap which tops the u~ells 50 are chosen so as to reduce the amount of radiation beamed into the working area of section 3 from the remote handled uastes storab]e therein to within a safe level. The remedial action room provides a separately contained area within the remote handled section 3 of the facility 1 where broken liners (or liners containing liquids) may be properly repaired or treated without any danger of contaminating the main portion of the remote handled section 3, or the facility 1 at large. As will become more evident hereinafter, the provision of a separately contained room 53 to repair the broken walls of a liner is important because the walls of the liner provide one of the three radiation and water barriers within a module 200 when the liner is grouted within one of these modules.
Uhen free liquids are found within the waste liners, the remedial action roc>m 53 provides a contained area where the liquid may be 6137~

mixed with su~table absorbants or other solidi~icstion medi~ so as to bring it into a ~olid form acceptable for burisl within the purview of pre~ent federal regulations. Ilnder normal circumstances, neither the lag storage wells 50 nor the remedial action room 53 is used to process the remote handled wastes.
Instead, after the characterization tests are completed, these wastes are usually remotely hoisted through the labyrinth exit 56 formed by shield walls 57a, 57b which form the back of section 3 and placed into a modu]e 200 on a rail cart 64 en route to the 1 0 grouting station 118.
The module loading and transportation section 60 is centrally located within the facility 1 between the remote hand]ed section 3 and the contact hand]ed section 85. The central location of the modu]e loading and transportation section 60 al]ows it to 1 5 conveniently serve both the contact and remote hand]ed sections 3 and 85 of the facility 1. Generally, the module loading and transportation section 60 includes a conventional traveling crane 62 (uhich includes all the parts and capacities of previously described traveling crane 23) for ]oading modu]es 200 uhich are stacked outside the building 1 onto rail carts 69. These rail carts 69 are freely movable along a pair of parallel loading rail assemblies 66a and 66b. In order to render the rail carts 64 free-moving, the beds 70a and 70b onto which the tracks 68a and 68b are mounted are slightly inclined so that the carts 64 engaged onto the tracks 68a and 68b of the loading rail assemblies 66a and 66b urill freely roll down these tracks by the force of gra~ity. ~hile not shown in any of the several figures, each of the loading rail assemblies 66a and 66b includes a plurality of pneumatically-actuated stopping mechanisms for sSopping the rai] carts 64 at various lo~ding, grouting and cayping positions along the loading rail assemblies 66a and 66b. The snodu]e ]oading and transportation section 60 includes a return rail assembly 74 having a bed 78 which is inclined in the opposite direction frorn the beds 7Da and 70b of the loading rail assemblies 66a and 66b. The opposite inclination of the bed 78 of the return rail assembly 74 allows the rail carts to freely roll on the tracks 76 by the force of gravity back to a 7g loadin g position in section 60 after a grouted and capped module 200 has been removed therefrom. Finally, a shield wall 79 (which is preferably formed from a solid concrete wal] at least 12 inches thick) is p~aced between the rail assembly 66a and the return rail assembly 74 in order to shield the contact section 85 from any exposure from the remote-hand~ed wastes contained within the shield bel] l9 as they are loaded into one of the modules 200 and grouted. This shie]d wall 79 generally serves the dual function of al]o~ng a contact-hand]ed waste section 85 to be enc]osed within the same facility as the remote handled ~ aste section 3, and allowing the use of a common module loading and transportation section 60 for both the remote and the contact handled ~ections 3 and 85 of the facility 1. This last advantage avoids the provision of duplicate loading and transportation systems.
Turning now to the contact-hand3ed waste section 8~, this section of the facility 1 includes many of the same general components present in lhe remote handled section 3. For examp]e, section 85 includes a drive-through 87 including the same sort of driveway 39, entrance 90 and exit (not shown) previously discussed with respect to drive-through 7. Section 85 also includes a processing platform 93 preferab~y formed from a solid s]ab of concrete which rises to approximately the same height as the bed of a truck so as to facilitate the un]oading of the packaged wastes from the delivery truck 9S. Section 85 also inc]udes a pair of characterization stations 107a ar~d 107b,,c~aa ~11 ~ s-t~ ollo 11~. Finally, section 85 inc]udes a remedial action room 112 for repairing broken containers, and converting liquid and other improperly packaged wastes into an flcceptable solid forrn for burial.
However, despite these common components with section 3, section 85 includes some other components which are unique in the building 1. For example, a relative]y light-duty jib crane 99 having a magnetic or vacuum hoist 101 is used in lieu of the relatively heavy traveling crane 23 of section 3. Because the wastes which are processed in section 85 are of a sufficiently low radiation ]evel so that they may be directly contacted by human 6~

workers, there is no need ~or ~ crane capable OI lifting the heavy shie]d bell 19 used in ~ection 3. Ccnsequently, the orane used ~n section 85 need only be capa~le of lifting lightly-packaged nuclear wastes, which typically arrive ~t the building 1 in 55-gallon steel drums 97. A]though some light shadc~w shie]ds may be used on the contactable ~ection 85 of the bui~ding 1, the generally low radiation level of the ~astes processed in this area ob~ates the need for heav~ly shie]ding each oi steel drums 97 containing the wastes.
Therefore, a conveyor systern 103 prefer~bly formed from rollers is l O provided which great]y facilitates the h ndling of the drums 97 in which the wastes are contained. Finally, a high-force compactor 110 is provided which not only compacts the wastes into a smaller volume 9 but squeezes the surrounding drum down lo a point so far sbove the inelastic limit of the steel that the w astes are incapab]e of springing back in volume during the grouting process. This is an important advantage uhich will be elaborated on at a later point in this lext.
The conveyor system 103 includes both a pair of seriall~
arranged compactor conveyor belts 105a and 105b, ~s well as a remedial action conveyor belt 106. Compactor conveyor belt 105a conveys the 55-gallon drums 97 containing the contact-handled uaste f~om the jib crane 99 through a first characterization ststion 107z which includes ultrasonic and radiation detec~ors (not shown), and into lhle loading mechanism 110.1 OI the high-~orce CQmpaCtO.
110. ~he h;gh-force compactor 110 applies a pressure of between 500 And 1,100 tons to the 55-gal~on drum conlainers, thereby reducing them into high-density p~lcks 117 hRving a density of between fiO-70 ]bs. /cu . ft . In the pr eferred embodiment, a oompAction force of 600 tons is typically used. The high-density 3~ ~u~k~ 117 are ejected from the high-force compactor 110, and slide down a ramp 111.2 onto compactor conveyor belt 105b, which in turn facilitates the mo~ement of pucks 117 through a second char~cterization station 107b which is likewise equipped with u]trAconic and radistion detectors (not shown). The conveyor belt ~, 10~.b ~Jlen conveys the high-density puck 117 to the magnetic or v~. uum hoist 116 s)f a jib crane 11~, which swings the puck 117 375~

over into a mGdule 200 en route to the grouting station 118. The remedial action conveyor belt 106 comes into pl~y when the characterization station 107a detect6 that (a) the drum 97 contains a liquid, ~b) the walls of the drum 97 are broken, or (c) the waste contained within the drum 97 is not eompressible. lf any of these three conditions are detected, a human operQtOr ~not shown) merely pushes the drum 97 from the compactor conveyor 105a onto the remedial sction conveyor be]t 106, which in turn conveys the drum 97 to the remedial action room 112 where appropriate ua~l-repairing, liquid solidification, or separate in-drum groutir.,, procedures are undertaken in order to put the drum 97 and its contents in proper condition for encapsulation uithin a module 200.
In the event there is a bac}~-up condition in the remedial action room 112, the drum 97 may be temporarily slored in the lag slorage wells 113 of the contac~ handled section 85.
~ith specific reference now to Figure 2, the high-force compactor 110 of the invention inc]udes a loading mechanism 110.1 ha~dng a drum scoop 110.2 at the end oî an articulated, retractable arm assembly 110.3 as shown. Drums 97 sliding down 2 o the chute flt the end of the compactor conveyor 105a are fed into the drum scoop 110. 2 by a human operator. The articulated, retractable arm assembly 110.3 then loads the drum 97 into a ]oading cradle 110.4. The compactor 110 further inc]udes a ]oading rarn 110.5 which feeds the drum 97 into A retractable compact;on cylinder 1~0.6 which is movable between a position outside the main ram 110 . 8, and the top of the ejectjon ramp 111.2. In Figure 2, lhe compaction cylinder 1~0.6 is illustrated in its extended position away from the main ram 1~0.8, and adjacent the top of the ejection rump 111.2. After the drum 97 is ]oaded into the compaction cylinder 110.6, the cylinder 110.6 is retracted into the m~in ram 110.8, where the drum 97 is crushed between the ram piston 110.9 (not shown), and the bed of the main ram 111.8. As previously mentioned, a compaction force of between 500 and 1,100 tons is applied to the drum 97. There are three 3 5 distinct advantages associated with the use of such a high compaction force. First, the consequent reduction in volume of 87~

the drum 97 and its ccntents allows many more drums to be packed inside one of the modules 200. Specifically, the use of such a high compaction force allows thirty-fi~e to eighty-four drums 97 to be packaged inside one of the modules 200, instead of fourl~en.
Secondly, and ]ess apparent, the use of such a high compaction force deforms the steel in ~he drums 97 as well as the waste contained therein well beyond the inelastic limits of the materials, so that there is no possibility that the resulting, high-density pucks will attempt to 7'spring back" to a larger shape after they are ejected from the ejection rarnp 111.~. The elimination of such "spring bsck" eliminates the possibility of cavities or internal cracks forming ~ithin the hardening grout in the modu]e 200 after the module 200 is loaded ~th pucks 117 and grouted. Far from "springing back7', the resu]ting high-density pucks 117, ~hen covered with grout, form 8 positive, non-compressible reinforcing structure in the inlerior of the module 200 uhich assists the modu]e in performing its a]ternative function as a structural support rnember for the earthen trench cap 164 which is applied over the disposal site 150. Finally, such extreme compac-ion of 2 0 the waste inside the drums 97 ( which is typically rags, paper and contaminated uniforms) renders them resistant to the absoprtion of wa1er. This, of course, malies lhem less prone to leaching out r adioactive mslerial in the remote event that they do become wet.
Such resist~nce to water absoprtion also renders the wastes less prone to bio-degradation which again comp]ements the overall funclion of the module 200 in encapsu]ating the wastes, since such bio-degradation can over time "hollo~ out" the vessel carrying the waste, and result in subsidence problems.
In closing, it shou]d be noted the c:ompactor 110 inc]udes an air filtration system 111.4 having a filter 111.5, a b]ower assembly 111.6, and an exhaust stack 111.7. I'he air filtration system 111.4 draws out any radioactive, airborne particles produced as a result - of the application of the 660-1, lO0 ton force onto the drum 97 carrying the contactable waste.
Turning back to Figure 1, section 85 of the facility 1 includes a grouting station 118 having an extendable trough 120 capable of ~4~

pouring grout into a module 200 on rail carts 64 engaged to either rai] assembly 66a ( adjacent the remote-handled waste section 3) or rail assembly 66b (adjacent the contact-handled waste section 85).
The use of a sing]e grouting station 118 for modu]es 20D loaded from both the non-contact and contact handled sections 3 and 85 again avoids the duplication of expensive components in the overall system. Just beyond the grouting station 118 is a capping station 122 including 8 traveling crane 126 having R hoist 128 for li~ting the lids 220 over the tops of the modu]es 200 incident to the capping process. A more precise description of the cApping process u~ll be given when the structure of the modu]es 20Q is related in detail.
While the modules 200 are normally filled ~ith u aste grouted at the grouting station 118 and capped at the waste packaging facility 1 located near the waste disposa] s-te 150 the~ may a]so be processed at the faciljties of the generator of the waste. Since the surface radiation of the resulting modu]es is generally low enough for contact handling the uastes in the modules 20D rnay be conveniently stored onsite pending the availability of disposal 2 0 space . ~hen disposal space is a~railable the modules 200 may be transported in reusable transporation overpacks (not shown) to the disposal site 150 and stacked directly into the trenches 152. ~hile this method is not preferred it is usually less e~pensive than using the onsite waste storage facilities.
Figure 3 illustrates the disposal site 150 used in conjunction with the packaging facility 1. The disposal site 150 generally comprises a trench 152 (or a plurality of paral~el trenches) having a generally ~lat al]uvia] f]oor 154. Before the trench is ]oaded with cnpped modules 200 in uhich the grout hns hardened a plurality of uater-c:ol]ecting Iysimeters 155 are uniformly placed throughout the iloor 154 in order to monitor the radiation level of u1ater in the trench. The lysimelers 155 are placed in the trench floor 154 by augering a hole in the f~oor and inserting the elongatPd bodies of the ]ysimeters 155 therein. A network of plastic tubes (not shown) enables the operators of the disposal site 150 to periodically draw out any water that has collected in the cup~ of the Iysimeters 155. The rfld;ation level of these water samples is periodically rnonitcired to determine whether or not any radiosctive subst&nces have somehow been leached from the modules 200. After the lysimeters 155 have been properly bu~ied throughout the floor 154, the floor 154 is covered with a gravel layer 156 about two feet thick, which acts as a capillary har~ier.
Even though the disposal site 150 is preferably selected in an area where all ~lou of ground uater would be at least 80 feet below the trench iloor 1~4, the ~ avel capillary barrier 156 is p]aced over the top of the floor 154 to provide added insurance against the seepage of ground ~ater into the s~acked array 160 of modules 200 by capil~ary action from the trench floor 154. ~ e all vf the capillary barriers in the disposal site 150 of lhe invention are preferably formed of gravel, it should be noted that the invention encompas~es the use of any coarse, granu]ar substance having a high hydr~ulic conductivity. The layer of gravel 156 is covered with a choked zone of sand 15~ approximately four inches thick.
This choked zone of sand 158 acts as a road bed for the wheels of the heavy forklifts 185 and trailers 184 ~hich are used to 2 0 transport ~he modules 200 to the trench 152 . Iî the zone 158 were not present, the wheels of these vehicles 184, 185 v.ould tend to sink into the gravel layer 156.
The next compor ent of the disposal site 150 is the solidly packed array 160 of hexagonal modules 200 illustrated ?n ~igure 3.
In the preferred embc~diment, the modu]es 200 are preferably stacked in mutually abutting columns, with each of the hexagon~l faces of each of the modules 200 coplanar wiLh the hexagonal faces of the other two modu]es forming the colurlln. ~ arIangement of the modu]es 200 into such mutll.Llly abuttirlg eolulrlns results in at ~east four distinct fldvantages. First, such solid pac}~ing of the modules 200 provides a support structure for the non-rigid trench cap 164 ~hich may be quickly and conveniently formed from natural, fluent substances such as soil, sand and gravel. Second, such an arrangement is almost completely devoid of any gaps between the modules 200 which could result in the previously discussed soil subsidence problems. Third, such an arrangement 7~a could weather even severe seismic disturbances, since each of the modules 200 is capable of indil~idual, differential movement along eight di~ferent p}anes (i . e., the top, bottom and six side ~urfaces of the hexagonal prisms which form the modules 2~0~. Becsuse none of the modules are rigidly interlocked with any of the adjacenl modules, e,l3ch of then!l is capable of at least some vertical and horizontal sliding movement in ~he event of 8 seismic disturbance. Such an eight-p]ane freedom of movement renders the entire module array 1 6û ~e~ibly conformable with changes in the shape of the trench 152, and eliminates or at least minimi~es the probability of a ]ocal seismic disturbance creating local 6tress points in the array 160 that are powerful enough to rupture or crack the walls of individual containers. Fourthiy, the columnar stacking used in the array 160 makes it easy to recover a particular module 20D in the event that such reco~ery becomes desirable, since any one of the modules 200 may be withdrawn from the trench by digging a sing]e, module-wide hole over the particular co]umn that the desired module is inc]~ded ~ithin. In the preferred embodiment, the most radioactive or "hottest" of the 2 0 modules 200 is p]aced on the bottom layer of the module array 16U
and surrollnded by ]ess radioactive modules so that the surrounding modu]es, and the midd]e and ~op module layers will provide adclitional shie]ding from the radiatjGn emanating from the materials in the "hot" modu]es.
The trench 152 further inciudes side gravel capillary barriers 162a and 162b uhich are positioned between the sides of the solid modu]e array 160, and the walls of lhe trench 152. A~ain, the purpo~e of these barriel s 162a and 162b is to prevent any seepage of waler from being conducted from the sides of the tr ench 152 to 3 o the sides of the solidly packed array 160 of modules 200. In the preferred embodiment, each oi these side capillary barriers 162a and 162b is about two feet thick.
The trench cap 164 is preferab]y a non-rigid cap formed from f]uent, natural substances such as soil, sand and gravelO Such a cap 16~ is more resistant to seismic disturbances than a rigid, syntheti- structure would be. Specifically, the non-rigidity of the 7~

cap 164 makes it at least partially "self`~healing" should any seisrnic dist urbance act to vertically shift the varivus layers of the cap 164 sm~ll distances from one another. Addition~lly, in the event of a severe seismic disturbance which does succeed in causing considerable damage to the cap 164, the cap 169 may be essily repaired wi~h conventional road bui~ding and earth moving equipment. As was previously indicated, the sGlidly packed array of modules 160 provides all of the structural support needed to construct and maintain the various layers of the trench cap 164.
The ~irst layer of the trench cap 164 is preferably a layer of al]u~um 166, which should rcmge from between f~ur feet thick on the sides to seven feet Ihick in the cenler. As is indicated in Figure 3, the alluvium laver 166 ~u~hich is preferably formed from the indigenous soil which v~as removed in creating the trench 152) graduall~ slips a~ay from the center line of the layer at a grade of appr~imately 9.5QO. Such a contour allous the cap 164 to effectively shed the ~ater ~hich penetrates the ouler ~ayers of the cap 164, and to direct this water into side drains 178a and 178b.
Afier the al]uvium layer 166 is applied over the top of the solidly 2 G packed modu]e array 160, the layer 166 is compacted before the r emaining layers are placed over it. Such compaction may be eîfec~ed either through conventiona~ road bed compacting e~liiF,ment, or by rnerely al]owing the alluvium in the layer 166 to complelely settle by natural forces. Of the t~No ~ays in which the alluvium in the layer 166 may be compacted, the use of rosd bed comp~ctiorl equipment is preferred. Even though the natural settling tirne of the a~luvium in the invention is very fast as compared to the settling times of soils used in prior art disposal sites, it is still rarely shorter than three months, and may be as 3; killg as one year, depending upon the characleIistics of the particular soil forming the alluvium. By contrast, if road compaction equipment is used, the settling time may be reduced to a matter of a few days. It should be noted that the alluvium layer 166 is placed over the solidly packed array 160 at approximately L}Je s~ime rate that the array 160 is formed by stacking the individual modules 200. Such contemporaneous placement of the 6~

al]uvium layer 166 over the module array 160 minimizes the amount of radiation which the trench workers are exposed to as the disposal site 150 is formed.
After the alluv~um layer 166 has been appropriately 5compacted, a choXed zone of sand 168 of approximately four inches in lhickness is applied over it. After the sand layer 168 has been completely ~pplied over the aluvium layer 166, another gravel capil]ary barrier 170, appro~imate]y two feet in depth, is placed over the choked sand layer 168. The choked sand layer 168 10serves as an intrusion barrier between the ~elatively coarse gravel forming the gravel capillary barrier 170, and the relative1y finer alluvium in the al~u~dum layer 166. Once the gravel c~pillary barrier 170 has been ]~ud, another choked zone ~>f sand 172, appro~-imate]y four inches in thickness, is applied over the gravel 15~ ary barrier 170. Next, a layer of fine, ater shedding silt is app]ied over the choked zone of sand 172 over~ying the gravel capillary barrier 170. Again, the choked ~one of sand 172 serves as an inlrusion barrier between the silt in the silt lhyer 174, and the gr~vel in the gravel capillary bal rier 170. The silt 20layer 179 is the principal uater-shedding layer of the trench cap 164, and is appro~imately two feet thick, and formed from sized material (preferably obtained ]ocally) ~hich is compacted in place.
The use of a silt ]ayer ~4 in lieu of other waler-shedding natural materials, such as clay, is advantageous in at least two respects.
25First, silt is often more easily obtainable ~ocal~y than clay, and hence is less e~-pensive. Secondly, if the silt layer 174 should becorr~e satursted with v.ater, it will not tend to split or crack w}len it dries out as clay would. The nbsellce of such splits or c~ ~lcks helps n~aintain the overall integrit~ of the trench cap 164.
30The side edges of the silt ~ayer 174 terminate tldjacent to the pair of french drains 178a tmd 178b located on eiLher side of the trench 152. The french drains 178a and 178b inc~ude a trench in which perforated pipes 182a and 182b are ]aid. Water ilowing do~n the sides of the silt layer 174 will loat through the 35pe-forations in the pipes 182a and 182b and flow along the drain trenches 180a and 180b, away from the trench 152. In the event 7~

that the ra~s ar other source of surface water becomes so severe that the silt l~yer 17g becomes completely saturated with water, the gravel capillary barrier 170 will prevent any water from migrating down from the saturated silt layer 1~4 into the module array 160 via capillary action.
The top and final l~yer 176 of the trench cap 164 consists of graded rip-rap which, in more colloquial terrns, is very coarse grave] (which may be as large as boulder sized). The rip-rap layer 176 performs at least three functions. First, it insulates the si~t layer 174 from potential]y erosive winds and running water.
Second, it pro~rides a final radiation barrier against the module array 160 which brings the radiation level o the disposal site 150 do~n to Nell within lhe range of normal background radiation.
Third, it provides an intrusion barrier which discourages wou]d-be human and anima] inlruders from digging up the ground above the moduie array 160. The preferred embodiment of the cap 164 as heretofore described is for arid regjons. ln humid regions, an a]ternative embodiment of the cap 16g would comprise a first uater infiltration barrier of native soil over the solid arra~ 160 of modu]es 200. This layer in turn wou]d be covered by a sand and gravel capillary barrier similar to the previously discussed layers 16~, 170 and 172. These sAnd and gravel capillar~ barriers would in turn be covered by a bio-intrusion layer of cobble, and topped by ~ddit;onal sand cuId gravel layers for supporting a fin~l layer of s( il having a vegelative cover. In such an &lternati~,e embodiment, the vegetative cover serves both to prevent any erosion uhich might occur on the Ipper ]ayer of soil, and also removes uater which infiJtrates the top layer of the cap. The vegetatjon used shou]d have shallow roots in order that the integrity of the cap 164 will not be violated. Additionally, such an alternative embodiment might have a steeper slope of perhaps 10 or more because of the grealer amount of rainfall associated ~ith such regions.
~ith reference now to Figures 4A, 4B, 9C and 51`, 5B, the moduie 200 of the invention generally consists of a container 201 having reinforced concrete u alls and a lid 220 which caps the ~6~

container 2û1 afler it is ~llled with nuclear svastes and properly grollted .
~ith specific reference now to Figures 4A through 4C, the container 201 of the module 200 is a hexagonally-shaped p~sm 202 having a cylindrical interior 216. The corners 20~ where the hexagonal walls abut one another are preferably truncated so thst small gaps wil~ be left between abutting modules 200 when they are stacked in the module array 160 il]ustllated in Figure 3. These small spaces are large enough to receive recovery tools (should the 1 0 recovery of any one of the modules 200 become desirable) but are smal] enou gh so that no significant amoun~ of soil subsidence uill occur hen the modules 200 are arranged in the configuration illustrated in Fi~rure 3. Further, the truncated shape of the corners 209 renders these corners ]ess ~rulnerable to the chipping or cracXing uhich could otherwise occur when the for}ilift 185 pushes the module 200 into the module array 160 incident to the stac~ing process.
Turning nou to the top and bottom portions of the containers 201 of the modu]es 200, the top portion 206 is opened as sho ~n to F-ermit the ~oading of nuc]ear aste ~nd grout. The top portion 206 inc]udes three I-bolt anchors 208a, 208b and 208c hich allow the container 201 to be hand]ed by the grappling hooks ol the cranes in the packaging facility 1 and stacked into the trench 164.
Alternatively, these anchors 208a, 208b and 208c r3110w the modu]es 200 lo be lifted out of the trench 16g if recovery is desired. The shanks of the anchors 208a, 208b and 208c are deeply sunhen into the concrete wa~ls of the container 201 flS i~dicated in order to insure an adequate grip thereto. The L)ottom portion 209 of the cont~ er 201 inc]udes the bottom surface 210 of the interior of the 3 o container 201, and an outer surface 211 ha~ring a pattern of grooves 212. Each of these grooves are slightly deeper and wider than the forks of the shielded forklift 185, so thEIt these grooves 212 greatly facilitate the handl;ng of the module 200 by the for}dift 185. The angular pattern of the grrooves 212 also allows such a 3~ fork]ift to engage a particular module from ~ variety of different angles, which further facilitates lhe handling o~ the ...

7~

modules. P~einforcing the concrete walls nd bottom portion of the container 201 of the module is a "basket" 215 formed from commercially available, steel-reinforcing mesh. The basket 215 greatly increases the tentile strength of the wal~s and bottom portion 209 of the container 201 of the module 200. In the preferred embodiment, the walls of ~he container 201 are at least three inches thick. Additionally, the cylindrical interior 216 of the container 201 is at least seventy-five inches in diameter in order that fourteen drums or seven stacks of high-density pucks 1 0 117 may be stacked ~ithin the cylindrical mterior 216 of the container 201. The lop p~rtion 206 of the container 201 includes a p]urality of grooves 21~a, 214b, 214c, 214d, 214e and 214f for receiving the cap-securing rods 232a, 232b, 232c, 232d, 232e and 232f of the slab-type container lid 220, which will be presently 1 5 discussed in detail .
~ith reference no~ to Figures 5A and 5B, the siab-type container lid 220 generally inchJdes a disk-shaped upper section 222, and an integrally formed, disk-shaped ]ower section 228 ~hich has a slightly smaller diameter. The edge of the upper section 222 ic llat1ened in three sections 223.1, 223.2 and 223.3, ~hich are spaced approximalely 120 from one another. ~hen the container lid 220 is properly pl~ced over the open top portion 2~6 of the container 201, these llattened sections 223.1, 223.2 and 223.3 should be angularly positioned so that they are directly opposite the previously discussed I-bolt anchors 20ga, 208b and 208c, in order to provide c~earance for crane hooks to engage the l-bolt sections of the anchors. The top surface 22q of the upper section 222 of the lid 220 includes a radiation ~arning symbol 226, which is prefersbly mo]ded into the face of the lid 220. An ic3entifying serial number may also be mo]ded into the top surface 229 of the lid 220 (as indicaled in Figure 3) in order that the module 220 may be easily identified if recovery of the module ever becomes necessary or desirab]e.
As may best be seen with reference to Figure 5A, three V shaped transporting lugs 227a, 227c and 227e are placed around the circumference of the upper section 222 of the container lid 220 7~

appro~nmately 120 from one another. These ]ugs 227a, 227c and 227e are preîerably offset from the ila~ened sections 223.1, 223.2 and 223 . 3 along the circumference of the upper section 222 . Such an angular offset between these lid-~ransporting ]ugs 227a, 227c and 227e and the aforementioned flat sections 223.1, 223.2 and 223 3 minimizes the possibil;ty that a crane hoc>k intended for engagement with one of the l-bo~t anchors of the module ccntainer 201 will insdvertently catch one of the lid transporting lugs 227a, 227c or 227e and accidentally tear it off. As previously mentioned, the container lid 220 further includes an integrally forn~ed ]ower section 228 which has 8 slightly smaller diameter than the disk-shaped upper section 222. A layer steel-reinforcing mesh 229 is mo]ded into the concrete forming the cont~iner lid 220 in the position shown in Figure 5B. A~so mo]ded into the lid 220 are 6iX
equidis~antly spaced cap-securing rods 232a, 232b, 232c, 232d, 232e and 232f. These rods are slid into the ~omp~ementary slots 219a, 214b, 214c, 214d, 219e and 214f after the conlainer has been filled with nuc]ear waste and grouted. Both the container lid 220 and the modu]e container are preferab]~ mo]ded from non-porous portland-based concrete having a compressive to]erance on the order of 4000 psi. Such concrete is both strong and resistant to penetration b~ water.
Figures 6 and 7 il]ustrate a module 200 uhich has been filled v~ith high-clensity pucks 117 formed from the h;gh-force compactor 110, and subsequently grouted and capped. In operation, seven stacks of high-density pucks 117 are central]y positioned ~Tithin the container 201 of the module 200 as shown in Figure 7. The compacted containers which cover t]le compacted waste form an additional rudiation and u ater barrieI bet~ecn the waste and the e~terior of the module 200. I~ext, the e~;tendab]e trough 120 of the grouting station 118 of the bui]ding 1 pours grout 218 over the seven stacks of pucks 117 so as to form a solid ]ayer of grout between the pucks 117 arld the inner surface of the walls of the container 201. In the preferred embodiment, the grout used to fill 2~5 the module 200 is a 3, 000 or 4, 000 psi portland-based concrete.
However, gypsum, pozzolan, flyash or other cementitious materials may also be used for grout. The hardened grout 218 forms a thiI d radiation and water barrier between the waste in the pucks 117 and the outer surLace of the container 200, as is evident from the drawing. The grout 218 also serves to anchor the cap-securing rods 232a, 232b, 232c, 232d, 232e and 232f into the body of the modu]e 200, so that the containér 201, the lid 220, the grout 218, and the stacks of pucks 117 become a single, solid structure having a considerab]e compressive and tensile strength.
The comp~eted, hardened modules 200 are carried from the packaging bui]ding 1 by drop-bed trailers 184, ~nd stacked into the solid array 160 il]ustrated in ~igure 3 by means of shielded forklifts lg5.
A]though not shown in any of the several figures, the module 200 ma~ be specially modified to package special, high intensity nuclea~ ~astes such as spent control rods. Specifically, the modu]e 200 may be formed ~ith ver~,7 thick concrete wa~ls so that a re]ative]~ ~mal] cvlindrica~ hollo~ space is left in the center of the modu]e. The control rods may then be transferred directly from a shield transportation cask 15 into the small cylindrical hollo-~ space in lhe pre-grouted module. Such a modified modu]e may be made longer to accommodate several complete control rods. In the allernative, pre-grouted modu]es 200 of norma] height ma3~ be used if the rods are cut up into smal]er ]engths.

Claims (12)

CLAIMS:

1. A disposal site for the disposal of toxic or radioactive waste, comprising:
(a) a trench in the earth having a substantially flat bottom lined with a layer of solid, fluent, coarse, granular material having a high hydraulic conductivity for obstructing any capillary-type flow of ground water to the interior of the trench;
(b) a non-rigid, radiation-blocking cap formed from a first layer of alluvium, a second layer of solid, fluent, coarse, granular material having a high hydraulic conductivity for blocking any capillary-type flow of water between the layer of alluvium and the rest of the cap, a layer of water-shedding silt for directing surface water away from the trench, and a layer of rip-rap over the silt layer for protecting the silt layer from erosion and for providing a radiation barrier;
(c) a solidly-packed array of abutting modules of uniform size and shape disposed in the trench and under the cap for both encapsulating said wastes from water and for structurally supporting said cap, wherein each module in the array is slidably movable in the vertical direction in order to allow the array of modules to flexibly conform to variations in the shape of the flat trench bottom caused by seismic disturbances, and to facilitate the recoverability of the modules;
(d) a layer of solid, fluent, coarse, granular material having a high hydraulic conductivity in the space between the sides of the modules and the walls of the trench for obstructing any capillary-type flow of ground water to the interior of the trench; and (e) a drain, and wherein said layer of silt is sloped to direct surface water flowing over the cap into the drain.

2. A disposal site for the disposal of radioactive waste, comprising:
(a) a trench in the earth having a substantially flat bottom lined with a layer of gravel for obstructing any capillary-type flow of ground water to the interior of the trench;
(b) a non-rigid, radiation-blocking cap formed from a first layer of alluvium, a second layer of gravel for blocking any capillary-type flow of water between the layer of alluvium and the rest of the cap, a layer of water-shedding silt for directing surface water away from the trench, and a layer of rip-rap over the silt layer for protecting the silt layer from erosion and for providing a radiation barrier, and (c) a solidly-packed array of abutting modules of uniform size and shape disposed in the trench and under the cap for both encapsulating said radioactive wastes from water and for structurally supporting said cap, wherein each module in the array is slidably movable in the vertical direction in order to allow the array of modules to flexibly conform to variations in the shape of the flat trench bottom caused by seismic disturbances, and to facilitate the recoverability of the modules.

3. A disposal site of claim 2, wherein each of said modules is shaped like a right-angled prism having a plurality of flat faces of equal size and shape.

4. The disposal site of claim 3, wherein said modules are stacked into a plurality of mutually adjacent columns and wherein the flat faces of each of the modules are arranged mutually coplanar with one another.

5. A disposal site for the disposal of toxic or radioactive waste, comprising:
(a) a trench in the earth having substantially flat bottom lined with a layer of solid, fluent, coarse, granular material having a high hydraulic conductivity for obstructing any capillary-type flow of ground water to the interior of the trench;

(b) a non-rigid, radiation-blocking cap formed from a first layer of alluvium to serve as a water infil-tration barrier, a second layer of solid, fluent, coarse, granular material having a high hydraulic conductivity to block any capillary-type flow of water between the alluvium and the rest of the cap, a bio-intrusion layer of cobble, an additional layer of solid, fluent, coarse, granular material having a high hydraulic conductivity for supporting a layer of soil having a vegetative cover which protects the upper layer of soil from erosion;
(c) a solidly-packed array of abutting modules of uniform size and shape disposed in the trench and under the cap for both encapsulating said wastes from water and for structurally supporting said cap, wherein each module in the array is slidably movable in the vertical direction in order to allow the array of modules to flexibly conform to variations in the shape of the flat trench bottom caused by seismic disturbances, and to facilitate the recoverability of the modules;
(d) a layer of solid, fluent, coarse, granular material having a high hydraulic conductivity in the space between the sides of the modules and the walls of the trench for obstructing any capillary-type flow of ground water to the interior of the trench; and (e) a drain, and said non rigid, radiation-blocking cap is sloped toward said drain in order to direct surface water into said drain.

6. The disposal site of claim 5, wherein each of said modules is shaped like a right-angled prism having a plurality of flat faces of equal size and shape.

7. The disposal site of claim 6, wherein said modules are stacked into a plurality of mutually adjacent columns and wherein the flat faces of each of the modules are arranged mutually coplanar with one another.

8. The disposal site of claim 5, wherein each of said modules is a hexagonal prism.

9. The disposal site of claim 1, wherein said solid, fluent, coarse, granular material having a high hydraulic conductivity is gravel.

10. The disposal site of claim 5, wherein said solid, fluent, coarse, granular material having a high hydraulic conductivity is gravel.

11. A process for burying toxic or radioactive wastes contained within a plurality of uniformly shaped, solidly packed modules comprising the steps of:
(a) digging a substantially flat bottomed trench in the earth;
(b) lining the bottom of said trench with a layer of solid, fluent, coarse, granular material having a high hydraulic conductivity for obstructing any capillary-type flow of ground water to the interior of the trench;
(c) disposing a solidly-packed array of abutting modules of uniform size and shape encapsulating said wastes from water in the trench wherein each module in the array is slidably movable in the vertical direction in order to allow the array of modules to flexibly conform to variations in the shape of the flat trench bottom caused by seismic disturbances and to facilitate the recoverability of the modules;
(d) placing a layer of solid, fluent, coarse, granular material having a high hydraulic conductivity in the space between the sides of the modules and the walls of the trench for obstructing any capillary-type flow of ground water to the interior of the trench;
(e) locating a drain to receive surface water directed by said layer of silt which is sloped to cause said surface water to flow over the cap into the drain; and (f) placing a non-rigid, radiation-blocking cap formed from a first layer of alluvium, a second layer of solid, fluent, coarse, granular material having a high hydraulic conductivity for blocking any capillary-type flow of water between the layer of alluvium and the rest of the cap, a layer of water-shedding silt for directing surface water away from the trench, and a layer of rip-rap over the silt layer for protecting the silt layer from erosion and for providing a radiation barrier, said cap structur-ally supported by said solidly-packed array of abutting modules.

12. A process for burying toxic or radioactive wastes contained within a plurality of uniformly shaped, solidly packed modules comprising the steps of:
(a) digging a substantially flat bottomed trench in the earth;
(b) lining the bottom of said trench with a layer of solid, fluent, coarse, granular material having a high hydraulic conductivity for obstructing any capillary-type flow of ground water to the interior of the trench;
(c) disposing a solidly-packed array of abutting modules of uniform size and shape encapsulating said wastes from water in the trench wherein each module in the array is slidably movable in the vertical direction in order to allow the array of modules to flexibly conform to variations in the shape of the flat trench bottom caused by seismic dis-turbances and to facilitate the recoverability of the modules;
(d) placing a layer of solid, fluent, coarse, granular material having a high hydraulic conductivity in the space between the sides of the modules and the walls of the trench for obstructing any capillary-type flow of ground water to the interior of the trench;
(e) locating a drain to receive surface water directed by said non-rigid, radiation-blocking cap which is sloped toward the drain; and (f) placing a non-rigid, radiation-blocking cap formed from a first layer of alluvium to serve as a water infiltration barrier, a second layer of solid, fluent, coarse, granular material having a high hydraulic conduct-ivity to block any capillary-type flow of water between the alluvium and the rest of the cap, a bio-intrusion layer of cobble, an additional layer of solid, fluent, coarse, granular material having a high hydraulic conductivity for supporting a layer of soil having a vegetative cover which protects the upper layer of soil from erosion, said cap structurally supported by said solidly-packed array of abutting modules.