tel I OF L ORNL P 1479 EEEEEEEE 125 LA LE ------- - - MICROCOPY RESOLUTION TEST CHART NATIONAL MUME AU OF STANOARDS - 1963 N + . 1 CIL LLL . A ... - - - .. LEGAL NOTICE This report was prepared as an account of Government sponsored work. Neither the United States, nor the Commission, nor any person acting on behalf of the Commission: A. Makes any warranty or representa- tion, expressed or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, appa- ratus, method, or process disclosed in this report may not infringe privately owned rights; or B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any information, apparatus, method, or process disclosed in this report. As used in the above, "person acting on behalf of the Commission” includes any em- ployee or contractor of the Commission, or employee of such contractor, to the extent that such employee or contractor of the Commission, or employee of such contractor prepares, disseminates, or provides access to, any information pursuant to his employ- ment or contract with the Commission, or his employment with such contractor. .. ..... ... ... ... ... ... . . .. .. procur. --... ......... ... . 13 - -- - - - - . . - Rehem* ..ORNI-P_1479 AVF-650539-1 MASTER AUG PROJECT SALT VAULT: RADIOACTIVE WASTE DISPOSAL IN A SALT MINE* W. J. Boesly, Jr., R. L. Bradshaw, 5. M. Empsonº, w. C. McClasa F. L. Parker, and w. F. Schalter, Jr.c 2 1990 Introduction Chemical reprocessing of power reactor fuel produces a chemically complex and hazardous effluent which cannot be handled by conventional waste-disposal methods. Special methods of disposal are required to safely contain these radioactive wastes for centuries, with adequate safeguards to prevent the escape of the fil8slon products to the environment. At the present time, the most promising method for the disposal of high-level, heat-generating, power reactor wastes is the conversion of liquid wastes to solids, followed by the ultimate disposal of the solids in salt formations. In September 1955, at the request of the Atomic Energy Commission, a ..... meeting of geologists and engineers was organized by the Earth Sciences Division . . of the National Academy of Sciences - National Research Council to discuss the .... . possibility of permanently disposing of radioactive wastes in geologic formations. In the committee report, salt was recommended as the most practical inmediate solution because of its impermeability, geographic distribution, thermal conductivity, strength, and abundance." As a result of these recommendations, studies on the disposal of high- level liguid and solid wastes were initiated at ORNL. Basic problem areas ... studied were the heat transfer from the waste to the salt, the effects of heat Research sponsored by the U. 8. Atomic Energy Commission under contract with the Union Carbide Corporation. Ostaff Member, Health Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee. "start Member, Chemical Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee. APPROVED FOR PUBLIC RELEASE and radiation on rock salt, and the economics of an actual disposal facility in a salt mine. The major conclusions drawn from these studios are: 1. The in situ heat-transfer properties of rock salt are sufficiently close to the values determined in the laboratory on single crystals that con- fidence can be placed on theoretical heat-transfer calculations. i t han inw .. mere ... . 2. Elevated temperatures will cause accelerated creer, but the exact effect on structural stability of the mine cannot yet be predicted with suf- ficient accuracy to allow the design of a disposal facility making the optimum use of mine space. .......... . . .. .. . 3. Most bedded-salt deposits contain trapped moisture which is released by a sbattering of the salt at temperatures above 250°c. By limiting the maxi- mum salt temperature in a disposal operation to 200°C, this problem can be avoided. 4. Rock salt 18 approximately equal to concrete for gamma-radiation shielding. . 5. A radiation exposure dose of 5 x 10° R produces some changes in the structural properties of rock salt (for example, about a 10% reduction in com- pressive strength); however, because of the shielding characteristics of salt, the effect produced will be limited to the salt near the radiation source. 6. Gamma radiation may produce some free chlorine within the salt structure; however, the amount released 18 expected to be negligible. 7. The relative stab.llity at ambient temperature of a salt mine used for waste disposal can be predicted from observed conditions in existing mines. 8. The economics of a salt mine facility for disposal of future high- level power reactor wastes indicate that costs will be on the order of 0.01 to 0.02 m1118/kwh of electricity generated. Project Sialt Vault Based on the studies summarized above, it was decided that a field spori- ment skild be designed and operated to demonstrate that it 18 feasible and safe to dispose of radioactive solid wastes in a salt mine. This demonstration, called Project Salt Vault, has also been designed to Lllustrate the equipment and operations necessary for an actual disposal fac!lity. Slace packaged solids are not currently in production, and pilot plant quantities will not be avall. able for some time, it has been decided to operate Project Salt Vault using irradiated fuel 288emblies as the heat and radiation sources, A study ot available fuel assemblies has shown that it is possible to simulate solidified wastes using 90-day-cooled Engineering Test Reactor (MR) fuel assemblies." The other main difference between Project Salt Vault and an actual disposal operation is that the fuel assemblies will be removed from the nine at the completion of the demonstration. The inactive salt nine of The Carey Salt Company at Lyons, Kansas, has been selected as the site of the demonstration, which is scheduled to begin in July 1965. The engineering and scientific objectives of the demonstrction are: (1) the demonstration of the waste-handling equipment and techniques ; (2) determination of possible gross effects of radiation (up to 20rad) on hole closure, floor uplift, salt-shattering temperature, etc., in an area where salt temperatures are in the range of 100 to 200°C; (3) deternination of possible release of radiolytically produced chlorine; and (4) collection of Information on creep and plastic flow of salt at elevated temperatures which can be used later in the design of an actual disposal facility. Since in a normal mining operation only the layers of purest salt are mined, the less desirebie (that 18, shule-containing, lower purity) salt 18 left as the mine floor and roof. It an abandoned mine 1s to be considered . as a disposal site, the vaste will not be stored in pure salt, but rather in salt laterbedded with shale. These shales may contain water, increasing the corrosion problems and possibly presenting other problems. In order to study these problems, the fuel canisters will first be stored in a specially pre- pared area in which the canisters are located in the purer salt and then trans- ferred to an array in the existing mine floor. The experiment will be carried out using 14 irradiated Engineering Test Reactor (ETR) fuel assemblies contained in seven canisters. These canisters will be placed in a circular array of holes in the floor of an area, wined especially for the purpose, 14 ft above the floor of the areas mined previously. To increase the radiation dose received by the salt, the canned fuel assemblies will be exchanged for freshly irradiated assemblies at 6-month intervals over the course of 2 years. All fuel assemblies will be returned to the Idaho Chemical Processing Plant (ICPP) after removal from the mine. A second array, consisting only of electrical heaters, will be operated as a control to determine effects due solely to heat. The final portion of the demonstration 18 a pillar heating experiment where a large mass of salt underlying a mine pillar is heated to obtain information on salt flowage and wine stability as & result of increased salt temperature. Engineering Description of Project Salt Vault A schematic cross section of Project Salt Vault 18 shown in Fig. 1. As presently conceived, the fuel assemblies, after canning in Idaho, will be shipped on a specially designed truck trailer in an ORNL carrier which has been modified for this purpose. At Lyons, the carrier will be removed from the trailer and placed vertically over a steel-cased charging shaft which extends to the mine working area, approximately 1000 ft below. The fuel canisters will be lowered one at a time down the 19.1-1n.-ID vaste-charging . -- -+ :- c V . 7 . - - - -- . . . . - - .. = 1 shaft into a shielded cask, mounted on an underground fuel assembly trans- porter. The transporter will then move to the experimeatal area, and the Puel canister will be lowered into a suitably lined and shielded 12-11. -diam, 13-ft-deep hole. The shaft at the Lyons mine was excavated in 1890 and mining was con- tinued by a number of companies until 1949, when mining operations were sus- pended. The main shaft 18 timber lined and consists of two hoisting compart- ments and one airway. The production headframe and plant were removed in 1955, and a small temporary heudframe was erected. This headfrane had a capacity of about 3000 2b. The temporary headframe and the hoist building are shown in Fig. 2. The Stearns-Roger Corporation was employed to survey the salt mine facili- ties and recommend and design new facilities and equipment to increase the hoisting capacity from 3000 10 to 7 tons. It was determined that a new head- frame, shaft collar, and cages would be required to supply the necessary capa- city. Construction of the new facilities was completed in 1964, and these new • -- « « facilities are shown also in Fig. 2. - - - Stearns-Roger also recommended a general renovation of the hoist, bolst drive, electrical services, safety systems, and the hoist house. The hoist house renovations are complete, and they include a new concrete floor to re- place the old wood floor, a new electrical system, including the main mine switchgear, and a complete checkout of the hoist and electric drive. During the checking of the hoist, it was found that the main 9-1n.diam boist sbart . deflected under load. The hoist was originally a single drum boist which was later converted to a double drum hoist. An ultrasonic check of the integrity of the hoist shaft showed that the shaft had no defects. A detailed analysis of the stress la the shaft led to a decision to Install a center bearing. The Installation of this bearing bes reduced the shaft deflection and bending . - till . t j ORNL-DWG 63-3918R2 FEAD FRAME- SHIPPING TRAILER FUEL ASSEMBLY SHIPPING CASK-- FUEL ASSEMBLY CHARGING SHAFT- 1000 ft -- FUEL ASSEMBLY TRANSPORTER DOUBLE CONTAINMENT Lai ENTRY 5 1481 I w . SHIELD 44- - ENCAPSULATED FUEL ASSEMBLY - 100% GRADE -HOLE LINERS T - Fig. 1. Schematic Cross Section of Demonstration (W. J. Boegly, Jr., et al.). stresses in the shaft during the lovering and raising of large loads. As soon as access to the main shaft was attained, a completo check and repair of the hoist guides and shaft tiubering in both hoisting compartments was carried out. Following this, a new main power cable and signal cable were installed in the north shaft compartment. The original power cable was left in place to serve as a standby. After completion of the beadframe and grading around the shaft area and boist house, a security fence was installed to prevent unauthorized access to the shaft and hoist. In order to transfer the highly radioactive fuel assembly canisters into the mine, a waste-charging shaft has been drilled from the surface into the mine. The design of tra waste shaft 16 as follows: (1) A 42-19. corrugated Fig. 1. Schematic Cross Section of Demonstration (W. J. Boegly, Jr., et al.). culvert was lastalled and cemented in place to a depth or 12 ft to act as a conductor pipe; (2) a 26-in.-OD surface pipe was installed and cemented in place to a depth of 300 ft to soal off surface water; and (3) a 19.1-in.-OD casing was installed and cemented in place from the surface to a total depth of 1047 ft. The shaft was drilled into the salt adjacent to the experimental area and an access tunnel driven to connect with the shaft. The final devia- tion of the bottom of the hole (1047 st) from a true vertical was 2.56 ft. The waste-charging shaft, in addition to being used to insert and remove the canisters from the mine, will be used as a part of the ventilation system for the experiment and can be used as an emergency escape shaft if necessary. Underground, the Lyons mine shows considerable evidence of carth pressure. produced floor heaves and ceiling sage. A major portion of the underground work was the clearing of approximately 2000 ft ojº une passages to provide safe access to the experimental area. Since the main portion of the experia ment is located above the mine floor, in the perimeter of the nine, It was necessary to construct a ramp to reach the higher elevation. The grade of page 8 PHOTo 68265 | | - ... ... .. .. سمعة .. فن س. .. حد . . به مهد مه نیمسن سیمنس نمیتونه تمدید... مه مه ........... - .. .. .. .. .. .. .. .. .. ..... . .. .. ... .. .. . .. . ........... . . . .. . . TEMPORARY FACILITIES .. .. . . . . . . ... . 2 . . . . . م- - احسنتمممنلتلفصلنضمن شغضنععنقف ضد شعبنشیسمستفتیم. بعض د انه منه ....... ... .سه ... مسم ..منمة مهمه ممسمهند مسميا.... ممسنیم - . ... ...... مصمم. . ... ... منه مسهه تسامه .. ... .. مته فخمه نشم. اي .. ... - دن .. .: .: ک ننده . .. .. .. .همه مدونه ندونه ..ههههه . . . ..... . مه ...... مه. ........... .مدمر ع .. .. .. .. مه • • .. . . .. .. . مان . . ، مهمة مستمسه التسمية mingly, Jr., et al.). Lyons, Kangas (3. Topside I 7:", 2. this ramp was set at 10%, and the new floor 1s about 14 st above the existing floor. In order to provide the area required for the tests, a modified roon-and- pillar mining pattern was chosen in which there would be four rooms and three pillars. This configuration provides the symmetry necessary to compare the results of the array tests. The layout of the newly mined area 18 shown in Fig. 3. Also shown in Fig. 3 18 the location of the array in the existing mine ricor. Mining of the experimental area to a height of approximately 14 ft required the excavation of about 19,000 tons of salt. The radioactive and electrically heated control arrays are located in the two end rooms which are 30 ft wide by 60 ft long and separated from the other rooms by 30-ft-wide pillars. The center pillar, which 18 to be heated to provide the plastic-flow data, will be 20 ft wide and will be bordered by 40-ft-wide rooms. The stainless steel canisters (4 3/4 ini in diameter by 7 1/2 ft long and shielded at the upper end by a depleted uranium plus, 5 5/8 in. in diameter), containing the radioactive fuel assemblies, will be lovered from the surface carrier to the underground mobile transporter (Fig. 4). The transporter 18 "basically a conventional diesel-powered, two-wheel tractor and a special trailer, containing a movable 19-ton lead cask. Doors at the top and bottom of the cask are operated remotely to ir und unload the carrier, and they contain the canis- ter during transport below ground. The transporter will move the canister from the waste shaft to the experimental area where the cask will be positioned and lowered over the designated hole in the mine floor. The cask is capable of movement in three directions to facilitate alignment of the canisters and the . holes. A simplified cross section of the floor hole with the canister in place 18 shown in Fig. 5. The upper part of the storage bole consists of a 16-11. ORNL-DWG 63-774A ULL C o FEET 50 100 DO 150 . 1 1 . 1102 ELECTRICAL ARRAY 2 O . VO . 10 404+ 60 ++ . A U1 C *** 323 HEATED PILLAR C 1 O 00 DO Du MAIN RADIOACTIVE ARRAY U1U 1 . . UI 1 50 WASTE CHARGING SHAFT FROM SURFACE SPECIALLY MINED AREA 14-6+ ABOVE EXISTING FLOOR LEVEL 11 . 30 ** RAMP UP UIT . . EXISTING MINE WORKINGS SHOWN APPROXIMATE FLOOR RADIOACTIVE 1 ARRAY 1 O VU Tag. 3. Layout of Experimental Area (W. J. Boegly, Jr., et al.). . - * -. EPS . . . . en generasi me.. ., .. .. co.i d ':.*. :-Haltestellen We w hen you . .. • •* 1.-.- ? m . na .. . ao...... Intan' d 650G ... - . mantasanoma noorte o ; *;...! Fig. 4. Waste Disposal Transporter (W. J. Boegly, Jr., et al.). ORNL-OWO 44-452 FLOOR OF MINE V . CEMENT GROUT -16.in. ORILL HOLE SALT SALT . -- STEEL SHOT 17 SHOT RETAINER - 5ft 3 in. - -UPPER (FIXED) HOLE WNER - SALT DEPLETED URANIUM SHIELD PLUG REMOVABLE LOWER LINER Fig. 5. Simplified Cross Section Through Demonstration Hole (w. J. Boegly, Jr., et al.). -CANISTER 지워 ​-FUEL ASSEMBLY -12-in. DRILL HOLE – Tin – 7ft SALT hole drilled to a depth of 5 ft 3 in., followed by a 12-in. bole drilled to a total depth of 12 ft 10 10. Into this hole 16 inserted the metal lloer used to provide containment and to insure that the canisters can be removed at the conclusion of the experiment. The liner 16 xade in two sections: The upper liber 18 carbon steel and 16 grouted into the mult, and the lower liner section 18 bolted to the fixed upper section and 16 removable. for maximum corrosion resistance, the lower liner section is made of 304L stainless steel. Not shown on 718. 5 are the thermocouples and heaters Installed as a part of the lower liner section. These heaters will be used to supplement the fission product heat from the fuel assemblies. The uraniuw plug on the top of the canister, the steel shot in the upper portion of the liner, and the 6 It of salt above the fuel assemblies will insure that the background radiation 16 low enough to allow unlimited access to the experimental area. Temperature Rises and Radiation Dose to the salt Figure 6 shows the temperature rise profiles in the vertical plane through the center of one of the seven-can arrays after about 18 months of operation. An approximately spherical volume of salt, about 15 ft in diameter, will experience temperature rises in excess of 80°C. Temperatures within the array itself are not shown, but the peak temperature of the salt in the center will reach about 200°c. Power to the auxiliary heaters in the radioactive arrays will be adjusted to provide temperature rises comparable with those measured in the fixed-power electrical control array. The temperature pattern which will be produced be- neath and in the electrically heated center pillar 16' not showa, but most of the area beneath this pillar will be heated to temperatures between 70 and 100°c. Due to temperature limitations on the canning and shipment of the IR fuel assemblies, they will be 90 days decayed before they are placed in the mine. In order to achieve a maximum gamma dose to the mult approaching 10% . rads in the main array and in order to gain additional experience with the operation of the handling equipment, it has been decided to use four sets of assemblies during the course of the 2-year test. At the end of each 6-month period a new set of assoublies will be placed in the win array and the older assemblies will be transferred to the array in the existing floor. The maxi. mum dose to the salt in the floor army should approach 10° rado. Experimental Measurements 11 Approximately 450 thermocouples will be installed around the three arrays and the heated pillar to determine temperature rise protlles during the demon- stration. Two 144-point data loggers will routinely record temperatures in the salt surrounding the canisters, and critical temperatures (such as those in the fuel assemblies) will be printed on 24-point recorders. Some of the thermocouples in the salt will not be connected to recording equipment, but will be read periodically with a portable instrument. Gas will be sampled from the annulus between the salt and the hole liner in some of the radioactive array holes to check for the release of radiolytically produced chlorine. The field test will provide an opportunity to check for chlorine release from a much larger quantity of salt over a much longer period of time than has been possible in the laboratory. . Thermal expansion of the floor in and near the arrays will be measured by means of leveling points related to a benchmark outside the zone of influence of the test. Since both the radioactive and control arraya are to be operated with the same total power output, significant differences in thermal expansion should be indications of radiation effects. Differencas in the amount of closure of the holes will be measured also. ORNL-DWG 63–779R . . 2 . SALT PILLAR ROOM ROOM L. . 0100 010 DO . . C 11 0 . . VO 0 . DISTANCE FROM FLOOR LEVEL (ft) . . LIT . 60 30 400O 20 TEMPERATURE RISE (°C) 0 10 20 30 40 50 60 DISTANCE FROM CENTER OF ARRAY (ft) 70 . Fig. 6. Temperature Rise Isotherms in Vertical Cross Section Through Main Array (W. J, Boegły, Jr., et al.). ......... . 16 An birportant aspect of the demonstration is to determine the effect of heat and radiation on the plastic flow of salt and the resulting effect on the stability of the nine. To obtain background informatiou on room closure in the Lyons mine and also to obtain pro-excavation flow rates, a number of plastic- Ilow measuring stations have been installed around the shaft bottom, along the access corridors, and around the experimentual aru. The location of these gaging stations is shown on T18. 7. Not shown on 718. 7 are the gages which are being installed inside the experimental area. Two basic types of sages are used for the straia noasurements in this study. The first type is used to measure the convergence between the floor and the coiling, or between columns. (see Fig. 8.) The ends of the gage are located a sufficient distance into the salt to eliminate erroneous errors due to surface spalling and separation. Readings are taken by inserting a developed and furnished to ORNL by Professor I. L. J. Potts of the University of Newcastle-Upon Tyne England, and allows a number of strain measurements to be made in a single bore-hole. This type of gage is used to make strain measurements in the salt at depths up to 120 ft. Basically, the gage consists of wires or tapes connected to anchors set at various distances into the salt and to a metal reference plate fastened to the surface of the salt.° To measure the strain, a special reading device is fastened to the plate, and each tape or wire 18 loaded to a previously set tension and the flowage determined. • At various locations 1n the nine, stress changes produced by excavation and heating will be monitored by "stressmeters" developed by Professor Potts.º Th18 Information, plus the strain measurements, and the results of laboratory studies using pillar models, should provide sufficient information to describe what is happening in the mine before the experiment is started, and what effect the hosting bas on the stability of the mine. ๆ !? ORNL-DWG 64-6012R MINE SHAFT JUULA 20 oooo oooooooo JOYOpoor JOOOU VOUDA _ _ SITE 2 - - - --- - - - - - 1 2 SITEIT no puedo OO 000000 ttSITE 3 - WASTE SHAFT SITE. 1 _ __ _ ... Gooŏ 00000000 mararnir sonnonnnnnnn 1000 100 200 • VERTICAL CONVERGENCE - HORIZONTAL CONVERGENCE - INTERNAL STRAIN O INTERNAL STRAIN, FLOOR AND ROOF PLUS VERTICAL CONVERGENCE O STRESS-CHANGE METER SITES 1, 2, 3 - THREE TYPES OF STRESS - CHANGE METER FEET . Fig. 7. Partial Plan of Lyons Mine Showing Locations of Stress and Strain Gages Outside the Experimental Area (W. J. Boegly, Jr., et al.). der ORNL-DWG 64-922R - ANCHOR C 1 → ANCHORS WIRES DIAL GAGE . - ANCHOR REMOVABLE READING UNIT [A] FLOOR-TO-CEILING CONVERGENCE GAGE [B] INTERNAL STRAIN GAGE Fig. 8. Types of Strain Measuring Gages Used in Lyons Mine (W. J. Boegly, Jr., et al.). 19 Conclusions Project salt Vault 15 a part of a development program designed to deter- mine the requirements for safe and economical disposal of radioactive wastes in rock salt formations. The waste-handling experience and the ult-flow data obtained in this experiment, when combined with the results of laboratory and theoretical studies on the structural stability of rock mult at elevated temperatures and pressurss, should allow the establishment of a basis for the design of an actual disposal facility for optimum use of salt nino space. - .- - References 1. Committee on Waste Disposal, Division of Earth Sciences, Disposal of Radioactive Wastes on Land, National Academy of Sciences, National Research Council Publication 519, April 1957, p. 6. 2. R. L. Bradshaw, Y. M. Ampson, W. J. Boogly, Jr., 8. Kubota, F. L. Parker, and E. G. Struxness, "Properties of salt Important in Radio- . active Waste Disposal," Proceedings of the International Conference on Saline Deposits, Houston, Texas, November 12- 1 1962 (in pross). VIUS . 3. S, R. L. Bradsbaw, W. J. Boogly, Jr., I. M. Empson, H. Kubota, F. L. Parker, J. J. Perona, and E. Q. Struxness, "ultimate Storage of High- Lovel Waste Solids and Liquids in Salt Formations," Treatment and Storage of High-level Radioactive Wastes, International Atomic Energy Agency, Vienna, 1965, pp. 155-175. K. 2. Morgan et al., Health Physics Div' alon Annual Report for Period Ending July 31, 1964, ORNL-3697, pp. 19-31. 5. R. L. Bradshaw, J. J. Porona, J. 0. Blomoko, Demonstration Disposal of High-Level Radioactive Solids in Lyons, Kansas, Salt Mine: Back- ground and Proliminary Design of Experimento, ORNL-1-734 (Jan. 10, 1964), p. 7 E. L. J. Potts, "The 'In Situ' Measurement of Rock Stress Based on Deformation Measurements," In in the Earth's Crust, June 13-14, 1983, pp. 396-107. International Conferenco on State 01 Stross M + li .. A .. um 2A . . END F 2 DATE FILMED 9/22/65 is.