In 1978, the Department of Energy, Nevada Operations Office (DOE/NV), established a managed LLW disposal project at the Nevada Test Site (NTS). Two, sites which were already accepting limited amounts of on-site generated waste for disposal and off-site generated Transuranic Waste for interim storage, were selected to house the disposal facilities. In those early days, these sites, located about 15 miles apart, afforded the DOE/NV the opportunity to use at least two technologies to manage its waste cost effectively. The Area 5 Radioactive Waste Management Site (RWMS) uses engineered shallow-land burial cells to dispose packaged waste while the Area 3 RWMS uses subsidence craters formed from underground testing of nuclear weapons for the disposal of packaged and unpackaged bulk waste. The paper describes the technical attributes of both Area 5 and Area 3 facilities, the acceptance process, the disposal processes, and present and future capacities of both sites

Becker, B. D.

Clayton, W. A.

Crowe, B. M.

Gertz, C. P.

UNT Digital Library

f c LOW-LEVEL RADIOACTIVE WASTE (LLW) MANAGEMENT AT THE NEVADA TEST SITE (NTS) DOE/NV--520 Prin+,c Author: Bruce D. Becker, Low-level Waste Project Manager, Bechtel Nevada, Contributing Authors: Carl P. Gertz, Assistant Manager Environmental Management, US. Department of Energy, Nevada Operations Office Wendy A. Clayton, Waste Operations Team Leader, U.S. Department of Energy, Nevada Operations Office Bruce M. Crowe, Los Alamos National Laboratory, Science Advisor to the Office of Assistant Manager Environmental Management, U.S. Department of Energy, Nevada Operations Office Introduction In 1978, the Department of Energy, Nevada Operations Office (DOEN) ,  established a managed LLW disposal project at the Nevada Test Site (NTS). Two, sites which were already accepting limited amounts of on-site generated waste for disposal and off-site generated Transuranic Waste for interim storage, were selected to house the disposal facilities. In those early days, these sites, located about 15 miles apart, afforded the D O E N  the opportunity to use at least two technologies to manage its waste cost effectively. The Area 5 Radioactive Waste Management Site (RWMS) uses engineered shallow-land burial cells to dispose packaged waste while the Area 3 RWMS uses subsidence craters formed from underground testing of nuclear weapons for the disposal of packaged and unpackaged bulk waste. Technical Attributes The NTS is a federally owned facility located on the southern end of the Great Basin in south central Nevada. It consists of 1,350 square miles and is surrounded by Nellis Air Force Base (NAFB) range'and areas controlled by the Bureau of Land Management (BLM). Access to the NTS is controlled by manned guard gates. The two disposal facilities are inside the boundaries of the NTS and are located 16 miles (Area 5 )  and 30 miles (Area 3) north of the main access gate. Remoteness to populated areas is a key feature which enhances the site characteristics. The closest populated area to either disposal facility is the small town of Indian Springs, NV located 34 miles to the southeast. The major population center of Las Vegas is over 60 miles southeast. The Area 5 RWMS is located in the southeastern section of the NTS in Frenchman Flat, within a topographically closed basin where all surface water drains into a playa lake. The facility is sited on a coalesced alluvial fan, south of the Massachusetts Mountains. The water table is 800 feet beneath the facility. Site characterization studies show that there is no aerially distributed recharge to the aquifer in the vicinity of the RWMS. In fact, hydrogeologic testing in boreholes show that in the upper 150 feet of the vadose zone, the water vapor is actually in upward movement (negative water potentials). The Area 3 RWMS is located approximately 15 miles north of the Area 5 RWMS in the Yucca Flat basin, another closed basin where all surface drainage terminates in a playa lake at the south end of the basin. The water table is 1,600 feet beneath this facility. Both facilities receive on average 4-6 inches of precipitation annually. Measurements at meteorological DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makcs any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or use- fulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any spe- cific commercial product, process, or service by trade name, trademark, manufac- turer, or otherwise does not necessarily constitute or imply its endorsement, ream- mendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not neccssarily state or reflect those of the United States Government or any agency thereof. ... DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. stations show that annual potential evaporation exceeds precipitation by greater than a factor of 14, and maintains a moisture deficient. The Nevada Test Site Waste Acceptance Criteria (NTSWAC) limits the amount of fiee liquids the waste can contain to one percent of the volume of the waste in a container. This equates to a approximately one half gallon in a fifty-five gallon drum or one gallon in a 4'x4'x7' box. The adequacy of these limits were verified in the Area 5 KWMS Performance Assessment (PA). In the PA, no credit was given for the packaging of the waste. All waste and radionuclide inventories were assumed to $e available to the transport process immediately upon final closure of each cell. A bounding scenario in the PA model assumed uniform closure cap subsidence to a depth of six feet below grade, three successive hundred year flood events which filled the six foot subsidence depression and then infiltrated the ponded water into the waste. Even under these extreme conditions, the disposal site did not exceed the regulated performance objectives. Acceptance Process The Nevada Test Site Waste Acceptance Criteria (NTSWAC) establishes the standard and requirements that generator sites must meet in order to receive approval to ship radioactive waste to the NTS. The NTSWAC covers the generator waste certification program, characterization of the waste, traceability, waste forms, and packaging and transfer of the material. The NTSWAC is maintained by the Radioactive Waste Acceptance Program (KWAP) personnel. The RWAP personnel review the generator's program and documentation to verify the generator sites capability to develop and maintain a NTSWAC compliant program. Waste profiles are reviewed, triennial program audits, annual assessments and periodic surveillances are conducted to verify and validate the Generators' Waste Management Programs. RWAP personnel can recommend the suspension of a generator program andor waste stream that was found to be noncompliant or falls below standards described in the NTSWAC. In addition to the reviews by RWAP staff, the actual waste shipment and containers are inspected upon arrival at the KWMS facilities to veri@ items such as placards, manifests, marking and labeling, and container integrity. Disposal Process Both RWMS's are shallow-land disposal facilities, but there are differences between the sites. Area 5 has 732 total acres available for disposal LLW. Of that, only 92 acres are fenced and in current operation. Here, engineered disposal cells are used for disposition of waste. These cells are planned, designed and constructed to fit within the existing fenced area. At Area 5,  LLW, on-site generated mixed waste (MW), radioactively contaminated regulated asbestos, and classified LLW are disposed. Higher specific activity LLW was disposed in Greater Confinement Disposal (GCD) boreholes, however this disposal option is not currently being used. Additionally, there are facilities for the storage, characterization, and certification of Transuranic Waste. Due to the fact that disposal cells at Area 5 are excavated, and consequently are more expensive to develop than the subsidence craters used at Area 3, this disposal space has historically been reserved for conventionally packaged waste. This includes steel drums and 4'x4'x7' or 2'x4'x7' wooden and steel boxes. On occasion, other sizes are accepted on a case-by-case basis, such as the regulated asbestos cell which accept S'xS'x20' cargo containers. All packages accepted for disposal at Area 5 are required to meet the rigid Department of Transportation performance based packaging requirements. With the exception of cargo containers and drums, the NTSWAC requires all boxes to meet a 3,300 pound compressive strength test. This provides a factor of safety for the workers. The waste packages are stacked one upon the other in a stair step configuration, until the stack is four feet below the top of the cell walls. Because these packages can weigh as much as 2 . 9,000 pounds each, there is the potential for the bottom box in the stack having to support in excess of 60,000 pounds of loading. Thus, strength criteria in conjunction with the stacking configuration ensures a secure work platform for the waste handling crew. Process safety is taken seriously, as the disposal operations has worked virtually accident free for more than 3 years. The Area 3 RWMS covers 120 acres. Area 3 disposes waste in underground nuclear weapons test subsidence craters instead of conventional engineered cells. The criteria used for choosing these craters was that the emplacement of the nuclear device had to have been above the water table. This criteria was chosen to ensure that no preferential pathway would be available to the aquifer. These disposal cells are considerably less expensive to develop than the Area 5 cells because the waste is disposed in existing subsidence craters. The disposal process also differs significantly here. Small packages such as boxes and drums are replaced with larger bulk sized packages such as the previously mentioned cargo containers, large pieces of equipment, super sacks or soils in lined dump trailers, referred to as “burrito wraps.” Instead of stacking the waste in a single monolith configuration, waste is disposed in a layer-cake geometry with each layer of waste covered by a layer of compacted soil ranging from 1-3 foot in depth. Present and Future Capacities The current Area 5 RWMS inventory of disposal cells is 22, not including the GCD boreholes. These range in size from 83 to 1133 feet long, 30 to 336 feet wide, and 12 to 48 feet deep. The total disposed volume of waste in these cells is over 9 million cubic feet. Available open capacity in the fenced 92 acre compound at Area 5 ,  in existing cells, is approximately 5 million cubic feet. No master plan currently exists for the layout of future cells across the total 732 acres. However simple calculations based upon existing inventory for the 92 acres show that the current capacity averages 152,000 cubic feet of waste per acre of available ground. Extrapolation of this calculation for the total 732 acres, taking no credit for future technology such as deeper cells, shows the total capacity of Area 5 RWMS is about 11 1 million cubic feet. The Area 3 RWMS has a total of 7 craters, representing 5 cells, designated for disposal operations. The current inventory of disposed waste at the Area 3 RWMS is approximately 10 million cubic feet. Open capacity available in the two developed cells is estimated to be between 10 and 12 million cubic feet. The two remaining craters, which at the present time are assumed to be individual cells, represent an estimated combined available future capacity of 8 million cubic feet. Conservative calculations of total disposal capacity at the NTS is about 140 million cubic feet. This does not consider expansion into undesignated land surrounding the Area 5 RWMS or the addition of subsidence craters adjacent to the Area 3 RWMS. In the five year period covering fiscal years 1993 through 1997, the NTS has received on average 709 shipments of LLW representing 7 18,000 cubic feet of waste annually from as many as 15 waste generators. This volume of waste has been transported, received, and disposed safely with no risk to the general public, the workers at the disposal facility or the environment. 3 

Low-Level Radioactive Waste (LLW) Management at the Nevada Test Site (NTS)

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Low-Level Radioactive Waste (LLW) Management at the Nevada Test Site (NTS)

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