APPENDIX C
ALTERNATIVES CONSIDERED BUT REJECTED FROM FURTHER EVALUATION
ACRONYMS AND ABBREVIATIONS
| DOE
Ecology EIS HLW LAW PUREX TRU TWRS |
U.S. Department of Energy
Washington State Department of Ecology Environmental Impact Statement high-level waste low-activity waste Plutonium-Uranium Extraction transuranic Tank Waste Remediation System |
| NAMES AND SYMBOLS FOR UNITS OF MEASURE, RADIOACTIVITY, AND ELECTRICITY/ENERGY | |||||
| Length | Area | Volume | |||
| cm | centimeter | ac | acre | cm3 | cubic centimeter |
| ft | foot | ft2 | square foot | ft3 | cubic foot |
| in | inch | ha | hectare | gal | gallon |
| km | kilometer | km2 | square kilometer | L | liter |
| m | meter | mi2 | square mile | m3 | cubic meter |
| mi | mile | ppb | parts per billion | ||
| ppm | parts per million | ||||
| yd3 | cubic yard | ||||
| Mass | Radioactivity | Electricity/Energy | |||
| g | gram | Ci | curie | A | ampere |
| kg | kilogram | MCi | megacurie (1.0E+06 Ci) | J | joule |
| lb | pound | mCi | millicurie (1.0E-03 Ci) | kV | kilovolt |
| mg | milligram | Ci | microcurie (1.0E-06 Ci) | kW | kilowatt |
| mt | metric ton | nCi | nanocurie (1.0E-09 Ci) | MeV | million electron volts |
| pCi | picocurie (1.0E-12 Ci) | MW | megawatt | ||
| V | volt | ||||
| W | watt | ||||
| Temperature | |||||
| C | degrees Centigrade | ||||
| F | degrees Fahrenheit | ||||
C.1.0 INTRODUCTION
This appendix describes the alternatives that were considered but rejected as inappropriate for detailed evaluation in the Tank Waste Remediation System (TWRS) Environmental Impact Statement (EIS). Discussion of additional alternatives, which were suggested by the public during the Draft EIS comment period, is contained in Volume Six, Appendix L. The initial range of technology options potentially applicable for remediating the tank waste and cesium (Cs) and strontium (Sr) capsules was developed by the U.S. Department of Energy (DOE) and the Washington State Department of Ecology (Ecology). The full range of alternatives was evaluated by DOE and Ecology and options that were not appropriate for detailed evaluation in the EIS were rejected. In addition, a number of potential alternatives were suggested by the public during the EIS scoping meetings. These alternatives were also evaluated by DOE and Ecology. The alternatives that were determined to be viable were included as alternatives in the EIS and those alternatives determined to be inappropriate for detailed evaluations were rejected from further consideration. The following criteria were used to determine the appropriateness of an alternative.
- Is the alternative relevant to the purpose and need for agency action in this EIS? If not, then the alternative recommended involves a topic or subject that is not part of this EIS and is not relevant or appropriate for inclusion in this EIS.
- Is the alternative technically viable and practicable?
- Can the alternative be designed to be protective of human health and the environment with practicable mitigative measures?
- Is the technology sufficiently mature to allow detailed evaluation? This criteria refers to technologies that are purely theoretical in their potential application to the TWRS project, and the costs and the time required to develop the technology would be exorbitant.
- Is the technology appreciably different than an alternative already included in the EIS or does it offer potential advantages in terms of effectiveness, costs, or impacts to human health and the environment?
If the answer to any of these questions was no, the alternative was rejected from further consideration in the EIS.
The rejected alternatives are divided into two main categories. The categories are 1) alternatives or technologies identified as potential technology options by DOE and Ecology that did not meet one of the criteria identified previously; and 2) alternatives or technologies proposed by members of the public that did not meet one or more of the criteria identified previously. The following sections discuss the content of the rejected alternative or technology and the reason for rejecting it.
C.2.0 ALTERNATIVES AND OPTIONS DEVELOPED BY DOE AND ECOLOGY
The following alternatives were initially identified by DOE and Ecology as being potentially applicable for remediating the tank waste and capsules; however, they did not meet one or more of the criteria identified in Section C.1.0.
C.2.1 RETRIEVAL AND TRANSFER
Open Tank Mining
This retrieval method pertains to an array of potential technologies that rely on mobile surface- or subsurface-based equipment to penetrate the tank, retrieve the waste, and remove the tank. Because this method of waste retrieval would need to be adapted to a radioactive environment, the extensive redesign of existing equipment and further development would result in exceedingly complex and potentially impractical systems. Consequently, the complexity would defeat the perceived benefits. This alternative was rejected from further consideration because it was not technically viable and practicable.
Drift Tunneling
The drift tunneling concept would insert mining equipment into tunnels bored in the side or bottom of the tank. The waste would be loaded into cars that would transport the waste to the treatment facility (DOE 1995a). This concept had the following disadvantages: 1) it would require a hole in the tank below the surface of the waste; 2) it would not be likely that mining equipment could operate across the full distance of a tank; 3) a tunnel would be dug in contaminated soil; 4) the concept is more complex than a mechanical system; 5) it would be difficult to provide confinement for contaminated soil and waste; and 6) loading, transporting, and decontaminating the cars would be impractical. This alternative was rejected from further consideration because it could not be designed to be protective of human health and the environment with reasonable mitigation measures and was not technically viable or practical.
Drag Arm
The drag arm concept would consist of a chopper pump, with a cutter head used to chop up the waste, operating on a blanket of water above the waste (DOE 1995a). This concept had the following disadvantages: 1) it would require a blanket of water over waste, which would increase the potential of large leaks from the tanks; 2) it would not remove waste that has hardened on the sides and bottoms of the tanks; 3) it would not operate in tanks where equipment was disposed; 4) it would not operate in a tank with numerous risers or in-tank debris; 5) it would not remove waste around stiffening angles at sides of tank; and 6) it would be difficult to operate. This alternative was rejected from further consideration because it was not technically viable and practicable.
Mechanical Dredge
The mechanical dredge concept would consist of a floating dredge device used to scoop up the waste as it was pulled along a positioning arm by a drag cable. The device would operate on a blanket of water positioned over the waste (DOE 1995a). This concept had the following disadvantages: 1) it would not operate in tanks with numerous risers or in-tank debris; 2) it would not remove waste near debris; 3) it would require a blanket of water over the waste, which would increase the potential of large leaks from the tanks; 4) it would not remove waste that has hardened on the sides and bottoms of the tanks; 5) it would not remove waste from around stiffening angles at the sides of tanks; and 6) it would be difficult to operate. This alternative was rejected from further consideration because it was not technically viable and practicable.
Load, Haul, Dump, Elevate
The load, haul, dump, elevate concept would use a self-propelled front loader-type device to scoop up the waste and transport it to a bucket or belt conveyor that would transport it out of the tank (DOE 1995a). This concept had the following disadvantages: 1) it would not operate on an uneven waste surface; 2) it would sink below the surface on soft waste; 3) the use of buckets and belt conveyors would not be suited for remote operation; and 4) it would have difficulty operating around tank risers and other debris. This alternative was rejected from further consideration because it was not technically viable and practicable.
Continuous Miner and Elevator
The continuous miner and elevator concept would use a self-propelled mining system introduced into the tank through a large opening in the top of the tank. The miner mechanism would propel itself around the inside of the tank, mechanically chewing and cutting up the waste then transporting the waste out of the tank with a bucket or belt conveyor (DOE 1995a). This concept had the following disadvantages: 1) a self-propelled vehicle would not work well on an uneven surface of tank waste; 2) a miner would sink below the surface of soft waste; 3) mechanical conveyors would not work remotely; and 4) a continuous miner would have difficulty operating around tank risers. This alternative was rejected from further consideration because it was not technically viable and practicable.
C.2.2 SEPARATIONS (Boomer et al. 1993)
Radio-Frequency Plasma Torch and Plasma Centrifuge
This method of processing would involve separating an ionized plasma stream into heavy and light fractions. The system would consist of a radio-frequency induced plasma torch dissociator and an electromagnetic plasma centrifuge. The torch would use ionized inert gas to create a plasma dissociation zone where compounds in the feed stream would ionize into their constituent elements. Heavy mass particles would be separated from lighter mass particles in the plasma centrifuge. This alternative was rejected from further consideration because the technology was not sufficiently mature to allow detailed evaluation.
Selective Leaching Processes
This process represents an intermediate position between simple water washing and dissolution of the sludge and would involve the selective removal of chemical components or groups of components. Because testing is still in the laboratory phase, this alternative was rejected from further consideration because the technology was not sufficiently mature to allow detailed evaluation.
Sodium Nitrate Crystallization
This technique would involve partitioning acidified waste solutions into a small volume of sludge and a much larger volume of sodium nitrate. If used, this technology would be applied to aqueous solutions of saltcake. The solution would be adjusted to a pH level of 1 to 2, and the solution would be thermally concentrated to exceed the solubility of sodium nitrate, which is removed by filtration. One perceived technical disadvantage would be the creation of additional sodium nitrate when the solution pH is adjusted. Because laboratory-scale development is currently underway, this alternative was rejected from further consideration because it was not sufficiently mature to allow detailed evaluation.
Precipitation Removal of Transuranic Elements, Strontium-90, and Technetium-99 from Alkaline Solution
This process would involve removing transuranic (TRU) elements, strontium-90 (Sr-90), and technetium-99 (Tc-99) from the alkaline waste by such techniques as hydroxide adjustment, sulfide precipitation, or formation of insoluble phosphates. Because initial laboratory scouting tests are just underway, this alternative was rejected from further consideration because it was not sufficiently mature to allow detailed evaluation.
Nickel Ferrocyanide Precipitation of Cesium-137
This process would co-precipitate cesium-137 (Cs-137) with the addition of nickel salts and ferrocyanide. In the 1950's, Cs-137 was removed on a large scale from alkaline bismuth phosphate waste. The process was later adapted to precipitate Cs-137 from the Plutonium-Uranium Extraction (PUREX) Plant high-level waste (HLW). This alternative was rejected from further consideration because it did not appear to offer a substantial processing advantage over conventional ion exchange techniques.
Sodium Titanate Precipitation from Alkaline Solutions
This process would consist of removing Sr-90 and TRU elements by co-precipitation with sodium titanate in alkaline solutions. This process has been demonstrated on a laboratory scale at the Savannah River Site. The disadvantage of this alternative was that initial test work indicated complexed species are not co-precipitated, meaning that Sr-90 and TRU elements would remain in solution unless the complexing agents were previously destroyed. As a result, this alternative was rejected from further consideration because it was not technically viable and practicable.
Bismuth Phosphate Precipitation of Transuranic Elements
Bismuth phosphate was one of the first processes used in acidic solutions to co-precipitate plutonium and neptunium. The disadvantage of this alternative was that the process would not function properly in alkaline media and would not remove trivalent americium (Am+3) even from acidic solutions. This alternative was rejected from further consideration because it was not technically viable and practicable.
Zirconium Phosphate Sorption
This process would use zirconium phosphate in a manner similar to an ion exchange resin. Zirconium phosphate would form a gelatinous amorphous solid of variable composition, which would adsorb cations because of an electrostatic charge formed at the surface. At present, there is only laboratory experience on this process; however, it is known that zirconium phosphate is unstable in the alkaline solutions such as the tank waste. This alternative was rejected from further consideration because it was not technically viable and practicable.
Molecular Recognition Removal of Transuranic Elements, Technetium, Strontium, and Cesium
This process would consist of extracting TRU elements, Tc, Sr, and Cs by a crown ether fixed on a solid substrate similar to an ion exchange media. This process would be a theoretical adaptation from using crown ethers in liquid-liquid extraction systems. This alternative was rejected from further consideration because it was not sufficiently mature to allow detailed evaluation.
Zeolites
This concept is based on using inorganic ion exchangers to remove Cs-137 from solution. The zeolite would be employed in columns similar to that of conventional ion exchange resins. Because the zeolite could not be eluted by nitric acid, which would destroy the loading capacity, it would be used once and then added to the feed to HLW vitrification. Because of the large increase in volume of HLW glass that would be produced, this alternative was rejected from further consideration because it was not considered technically viable and practicable.
Removal of Cesium-137 and Technetium-99 by Solvent Extraction
Various solvent extraction processes have been demonstrated on a bench scale and in some cases on a pilot scale for removing Cs-137 and Tc-99 from highly basic solutions. This concept had the following disadvantages: 1) the tendency to form aqueous-organic emulsions in alkaline media would lead to incomplete phase separation; 2) the polar solvents required to give acceptable phase separation are often toxic and possibly carcinogenic; and 3) large amounts of nitric acid would possibly be needed for elution. This technology was rejected because it is not considered technically viable and practicable.
Steam Reforming of Volatile Organic Compounds
This process would use the reaction of methane and steam with volatile organics at high temperatures and pressures to produce gaseous products such as carbon monoxide and hydrogen. The organics would be volatilized in fluid bed reactors. This concept had the following disadvantages: 1) many of the complexing agents in the waste would not be volatile and would remain in solution; and 2) high temperatures and flow problems with the waste would possibly cause problems in fluid bed reactors. This alternative was rejected from further consideration because it was not technically viable and practicable.
Oxalate Precipitation
The oxalate ion could be used to precipitate trivalent and quadravalent actinides and trivalent lanthanides from dilute nitric acid solution. The precipitated oxalates would be removed by mechanical means such as filtration. This technology was rejected from further consideration because it was not appreciably different and better than methods addressed in the EIS.
Lanthanum Fluoride Precipitation
This process would be used to precipitate TRU elements and lanthanides by adding hydrofluoric acid to acidified tank waste. The precipitate would subsequently dissolve in a mixture of nitric acid and aluminum nitrate. This alternative was rejected from further consideration because it was not appreciably better than the methods addressed in the EIS.
Antimonic Acid Sorption of Strontium-90
In this process, crystalline antimonic acid would selectively sorb Sr-90 from highly acidic nuclear waste solutions. This concept has not been developed further because laboratory testing has shown that no suitable eluting reagent has been identified. In addition, only small quantities of antimonic acid have been produced. This alternative was rejected from further consideration because it was not technically viable and practicable.
Phosphotungstic Acid Precipitation of Cesium-137
Phosphotungstic acid would precipitate Cs-137 in nitric acid solutions. Plant-scale recovery of Cs-137 from PUREX Plant waste has been routinely performed. The precipitated product has been recovered and subsequently purified. Because this method of precipitation would only remove 95 percent of the Cs-137, leaving 5 percent to be recovered by routine ion exchange methods, this alternative was rejected from further consideration because it was not technically viable and practicable.
Actinide Extraction Using Diamides
This process would consist of solvent extraction methods using diamides, which are bifunctional organic molecules that will extract +3, +4, and +6 actinides from strong nitric acid solutions. This concept is still in the laboratory experimentation phase. Other extractants are expected to provide superior performance. This alternative was rejected from further consideration because the technology was not sufficiently mature to allow detailed evaluation.
Actinide Extraction Using Carbamoylmethyl Phosphonate
The carbamoylmethyl phosphonate reagent would extract the same elements as the diamides (i.e., +3, +4, and +6 actinides). However, a more preferred extractant would be carbamoylmethyl phosphine oxide. Carbamoylmethyl phosphine oxide would be a stronger extractant and has been used successfully in bench-scale experimentation. This alternative was rejected from further consideration because it was not technically viable and practicable.
Americium Trivalent Extraction Using Dibutylbutylphosphonate
Dibutylbutylphosphonate is a phosphorus compound that has been proven to be a powerful extractant of Am+3 from acid solutions. However, the process development had many difficulties in controlling solution pH during extraction. The diluent employed was carbon tetrachloride, which is highly carcinogenic. This alternative was rejected from further consideration because it was not technically viable and practicable.
Cesium and Strontium Extraction Using Cobalt Dicarbolide
This solvent-extraction process would extract Cs and Sr from nitric acid solutions. Stripping would be accomplished by using strong nitric acid. Russian and Czech processes have been tested using toxic nitrobenzene as the diluent, although essentially no experimental work with dicarbolide extractants has been performed in the United States. This alternative was rejected because it was not technically mature enough for evaluation and was not better than methods addressed in the EIS.
Magnetic Separation and Flotation of Sludge Components
Magnetic separation and flotation of sludge components are physical separation processes that would potentially be applied to sludges to preferentially remove and separate components based on their magnetic characteristics and surface chemistries. The processes are commonly used in the mineral processing industries to separate the components of mined ores. These processes have not been tested for removing selected components from the tank waste sludges. Even in favorable circumstances, a certain percentage of the target material will commonly not be recovered. This alternative was rejected from further consideration because it was not technically viable and practicable.
C.2.3 WASTE TREATMENT FOR ONSITE DISPOSAL OF LOW-ACTIVITY WASTE (Boomer et al. 1993)
Electrolytic Denitration of Alkaline Nitrate Solutions
This process, which would use direct current to reduce nitrate in solution, has been the subject of limited investigation. This process was not evaluated because chromium inhibits denitration and toxic bismuth salts must be added to block the inhibiting effect. This alternative was rejected from further consideration because it was not technically viable and practicable.
Direct Calcination of the Low-Activity Waste
In this process the low-activity waste (LAW), without reducing agents such as sugar, would be fed directly into a calciner that would heat the material sufficiently to decompose carbonates, hydrates, and other compounds. This process was not selected for detailed evaluation because of the nature of the LAW feed to the calciner. This feed was composed of a major proportion of sodium hydroxide and sodium nitrate. The sodium salts would decompose in the calciner and form sodium oxide. Before the sodium nitrate and sodium hydroxide could heat sufficiently to calcine, they would melt and the molten salts would create a mush with the other solids in the calciner. This alternative was rejected from further consideration because it was not technically viable and practicable.
Inorganic Binders Used Directly on Dried Low-Activity Waste
In this process the dried LAW would be mixed with an inorganic binder that would immobilize the dried waste. However, no suitable binder material was identified. Both sulfur and lead had been mentioned as candidate binders. Both of these potential binders presented problems in their application. Sulfur binders may react with sodium nitrate in the waste, which is a powerful oxidizing agent. Lead binders would be expected to be unsatisfactory because the dried salts would float on the lead. In addition, the toxicity of lead would also lead to its rejection as a processing option. This alternative was rejected from further consideration because it could not be designed to be protective of human health and the environment with reasonable mitigative measures.
Bitumen Binders Used on the Dried Low-Level Waste
For this potential process the LAW would be mixed with a bitumen binder to immobilize the dried waste. This process had the following disadvantages: 1) fire hazard; 2) softening temperature; 3) radiation resistance; and 4) potential reactions of the bitumen with the nitrate in the salts. This alternative was rejected from further consideration because it could not be designed to be protective of human health and the environment with reasonable mitigative measures.
Hot Pressing, Hot Isostatic Pressing, Cold Pressing and Sintering, and Pellitization and Sintering
These compaction processes have been commonly used in industry to agglomerate powders of various kinds such as metals or ceramics. In the hot processing process, the powder first would be compacted with enough force to hold its shape; the compacted shape, then would be heated (in a protective atmosphere if required) until the particles fused at their surfaces and formed a durable shape that would withstand further handling and storage. These processes have only been applied on a laboratory scale. While hot pressing has been used in a demonstration program in Australia, none of these processes have the testing and demonstrated full-scale operation of vitrification. This alternative was rejected from further consideration because the technology was not sufficiently mature to allow detailed evaluation.
C.2.4 WASTE TREATMENT FOR OFFSITE DISPOSAL OF HIGH-LEVEL WASTE
Concrete Formed Under Elevated Temperature and Pressure
The ingredients for this process would generally be portland cement, fly ash, sand, clays, and waste (Boomer et al. 1993). This process would use accelerated curing at high temperature and pressure to produce solids that are strong and relatively impermeable. Initial tests on a high sodium nitrate waste produced a waste form that exuded liquid and cracked easily. This process might give more favorable results when the concentration of sodium salts is decreased, but no further test results were available. This alternative was rejected from further consideration because the technology was not sufficiently mature to allow detailed evaluation. This waste form would not meet the current waste acceptance systems requirements for the potential geologic repository (DOE 1995q).
Supergrout and Sludge in Concrete
In the supergrout and sludge in concrete processes, additives would be used in the grout to decrease the leachability of radionuclides and improve the properties of the final concrete. Supergrout would be a grout mixture of waste, special additives, and cement. Sludge in concrete would be HLW directly mixed with grout-forming materials at ambient temperatures and pressures. Waste oxide loadings for these forms have been generally less than those for vitrified products while leaching rates have been greater. These alternatives were rejected from further consideration because they were not technically viable and practicable. This waste form would not meet the current waste acceptance systems requirements for the potential geologic repository (DOE 1995q).
Aqueous Silicates
This waste form would incorporate an alkaline radioactive waste and a clay to form stable aluminosilicate minerals. This process had the following disadvantages: 1) the leaching rate of this waste form exceeded that of other waste forms; 2) immersion in water caused the waste form to crack and swell; and 3) waste loading for these salt forms was less than that for vitrified products. This alternative was rejected from further consideration because it was not technically viable and practicable. This waste form would not meet the current waste acceptance systems requirements for the potential geologic repository (DOE 1995q).
Multiphase High-Level Waste Forms, Including Cement Matrix, Coated Ceramic, Metal Matrix, and Sulfur Matrix
This process would result in a waste form consisting of two parts. The first part would typically be glass or ceramic in the form of marbles or cullet. The second form would be a matrix that covered the glass or ceramic and filled the interstices between the marbles or cullet. No advantage would be gained by using these forms for HLW because the glass or ceramic would be less reactive than the matrix material. The multiphase forms would occupy a higher volume than the glass or ceramic. This waste form would not meet the current waste acceptance systems requirements for the potential geologic repository (DOE 1995q). These alternatives were rejected from further consideration because they could not be designed to be protective of human health and the environment with reasonable mitigative measures.
C.2.5 IN SITU DISPOSAL (Boomer et al. 1991)
Heated Air Drying of Salts
This process would dry the saltcake by inserting a network of piping into the saltcake and forcing large volumes of heated air through the voids in the saltcake. However, excessive pressure would be required to force air through deep layers of the saltcake and could force solution to leak from the tanks. This alternative was rejected from further consideration because the technology was not sufficiently mature to allow detailed evaluation.
Resistance Heating and Induction Heating of Salts
During this process resistance heaters or induction coils would be inserted in the saltcake for drying the salts. This process had the following potential disadvantages: 1) poor heat transfer characteristics of the salts would result in excessive heating and possible melting adjacent to the heating elements or induction coils; 2) excessively high power consumptions and current densities would be expected; and 3) induction heating of very large volumes of salts has not been attempted. This alternative was rejected from further consideration because the technology was not sufficiently mature to allow detailed evaluation and is not technically viable and practical.
Electroosmotic Water Removal from the Saltcake
During this process fluids would diffuse through a semipermeable membrane under the influence of an electric field. This process has not been analyzed further because of the low mobility of water through salt at low moisture concentrations, and the difficulty in maintaining an effective electric field over large salt volumes. This alternative was rejected from further consideration because the technology was not sufficiently mature to allow detailed evaluation.
C.2.6 SPECIALIZED ALTERNATIVES
Seabed Disposal, Space Disposal, Deep Hole Disposal, Ice Sheet Disposal, and Island Disposal
These alternatives would consist of removing the tank waste and capsules from their present locations, packaging them in suitable containers, and transporting them to remote locations for indefinite disposal. These options have been previously investigated for disposal of radioactive waste and have been rejected for further consideration (WHC 1995a). National disposal policy is not within the scope of this EIS.
Geologic Disposal of Tank Contents, Tanks, Equipment, and Contaminated Soil
This alternative would involve removing the tank contents, tanks, ancillary equipment (e.g., pumps, piping), and contaminated soil from their present locations, packaging them in an appropriate manner, and placing them in a suitable potential geologic repository (DOE 1987). Removing the tanks and associated debris is not within the scope of this EIS, but will be evaluated in a future EIS. Therefore, this alternative was rejected from further consideration.
Rock Melting
This alternative would involve pumping HLW into conventionally mined cavities at depths of 1,500 to 1,800 meters (m) (5,000 to 6,000 feet [ft]) (WHC 1995a). The high levels of heat produced by the waste would melt the surrounding rock over time. In time, this melt would resolidify as a low soluble matrix. Using this alternative would require waste that generates extremely high heat. However, the TWRS tank waste (considered as a class) cannot generate the heat required. This alternative was rejected from further consideration because it was not technically viable and practicable, and reevaluating the national HLW disposal policy is not within the scope of this EIS.
Transmutation
This alternative would involve reprocessing the waste by converting it into a form that could be bombarded by radiation, which would convert the long-lived radionuclides into stable or short-lived radioisotopes (WHC 1995a). This alternative had the following potential disadvantages: 1) is anticipated that only 5 to 7 percent of the recycled elements would be transmuted during each reprocessing cycle; 2) it would be expected that it would take up to several decades to develop the advanced technologies that would be required; and 3) it is likely that the fission products would be hazardous and the need for other waste disposal technologies would be necessary. This alternative was rejected from further consideration because the technology was not sufficiently mature to allow detailed evaluation.
C.3.0 ALTERNATIVES IDENTIFIED DURING THE EIS SCOPING PROCESS (DOE 1995b)
The following alternatives were identified by the public during the EIS scoping process as potentially applicable for remediating the tank waste and capsules; however, they did not meet one or more of the criteria identified in Section C.1.0. Section 7.0 identifies issues raised by the public that have been included in this EIS.
C.3.1 WASTE STORAGE AND DISPOSAL
Grout the Retired Canyon Facilities with Hot Grout
This alternative would involve grouting the retired canyon facilities. In this alternative, grout would be the primary tank waste disposal method. Existing grout facilities would be used and the grouted waste would be placed in the retired canyon facilities to harden. This option would leave the HLW onsite in a form that could not be transported to a potential geologic repository. Furthermore, the canyon facilities were designed as chemical processing facilities, not as disposal facilities. Certain areas of the canyons were designed to shield radiation but other areas such as hallways were not. In addition, the canyon facilities were not structurally designed to be filled with grout and the facilities would fail over time. This alternative was rejected from further consideration because it was not technically viable and practicable.
Launch to Sun, Seabed Subduction, and Deep Hole Disposal
The first alternative recommended research to develop technology to launch tank waste to the sun or out of the solar system. The second alternative recommended that canisters of waste be inserted into the sea floor at points of subduction so that the material would eventually be drawn deep into the earth's interior. The third alternative suggested storing the materials several thousand feet down in a stable portion of the continent's thick crust. This could be accomplished by drilling standard oil well holes approximately 3,000 m (10,000 ft) down and then stacking stainless steel canisters on top of each other until they reach a depth of about 1,500 m (5,000 ft). The remaining depth of the holes would be filled with inert material (i.e., cement or clean fill). These alternatives have previously been evaluated for the disposal of commercial nuclear waste and have been rejected (WHC 1995a). Furthermore, national HLW disposal policy is not within the scope of this EIS.
Glass Logs in Grout Vaults, Solids in Tanks to Decay
This alternative would use a furnace to turn the liquid waste from the tanks into glass logs. The logs would be stored in grout vaults so that the Cs-137 could decay to innocuous levels. The tank solids would be left in the tanks to decay. This alternative was composed of two parts, each of which is bounded by the alternatives described in Appendix B. The first part addresses the vitrification of the HLW sludges from the tanks and the storage of the resulting glass product in existing grout vaults. The second portion of the alternative pertains to the decay of radionuclides in the tanks over a period of several hundred years. While this proposed alternative contains elements of the alternatives presented in Appendix B of this EIS, it was not accepted for detailed analysis. The vitrification of the sludge separations from the liquid is addressed in this EIS by the Ex Situ Intermediate Separations and Ex Situ Extensive Separations alternatives. However, storing the resultant HLW glass in the grout vaults would not be acceptable. The HLW glass would receive temporary onsite storage, but would eventually be shipped to the potential geologic repository. The short half-life of Cs-137 would cause it to decay faster than most of the radionuclides in the tank waste. This alternative was rejected from further consideration because it could not be designed to be protective of human health and the environment with reasonable mitigative measures.
Railcar Storage of Tank Waste
This alternative proposed using mobile railcars for transporting and storing tank waste. The alternative would use existing sidings plus new sidings with berms and liners or concrete aprons under the cars. These methods would allow adding early extra storage capacity, storing waste of diverse compositions without mixing, and transporting waste without new pipelines. Railcar storage was not a viable method for consideration in this EIS because 1) storing the tank waste in mobile tank cars would not comply with Federal and State regulations; and 2) using mobile railcars could not conform to the constraints of DOE Order 6430.1a with regard to seismic, safety, and shielding considerations. This alternative was rejected from further consideration because it could not be designed to be protective of human health and the environment with reasonable mitigative measures. Transporting waste by railcar is addressed in the Safe Interim Storage of Hanford Tank Waste EIS (DOE 1995i).
C.3.2 VITRIFICATION
Lead or Stainless-Steel Containers for High-Level Waste
This process would immobilize and dilute the radioactive materials in a glassification process, as appropriate. Following glassification, the treated waste would be encased in lead or stainless-steel containers suitable for long-term storage. Because of its ability to attenuate radiation, lead would seem to be a logical material for consideration in enclosing or surrounding HLW. However, lead is a toxic material with low mechanical strength whose use as a container would be inappropriate if a nontoxic alternate material was available. Stainless steel is such an alternate material and has been used in other countries as a container for HLW glass; it is also the container material proposed for the ex situ alternatives. Lead was rejected for consideration as a container material in the EIS because the technology is not appreciably different or better than those addressed in the EIS in terms of effectiveness, costs, or impacts to human health and the environment.
Unenclosed Furnace in Excavation
This alternative proposed building a 50 ton/day furnace using sodium nitrate from the tank waste liquid phase and making the remainder of the tank waste into a glass. The furnace could be built in an excavation in the ground in the 200 Areas. The commentor suggested that tanks would be necessary but no building would be necessary. This alternative would place the vitrification units belowgrade to alleviate the need for concrete shielding. While placing the treatment facilities belowgrade whenever possible might be considered good design practice, the absence of a roof is not protective of human health and the environment. The roof must be present to shield against radiation leakage and scatter. In addition, the roof serves a vital structural function in protecting against seismic events and preventing outside materials from being blown into the building. This alternative was rejected from further consideration because it could not be designed to be protective of human health and the environment with reasonable mitigative measures.
Placing Marbles or Clinkers Into Casks of Currently Contaminated Steel and Concrete
This alternative would store the vitrified waste product as marbles or clinkers in containers made from materials that have been contaminated in previous operations (i.e., contaminated steel or concrete). While recycling materials is becoming more prevalent in the United States, this particular option has not been accepted for further study in the EIS because the contaminated casks could not be shipped offsite safely without overpacking them, which defeats the purpose of the alternative. The casks made from contaminated material would need to be placed in casks made from noncontaminated material for shipment. This option would also involve constructing an additional shielded processing facility that would become contaminated during use. This alternative was rejected from further consideration because it could not be designed to be protective of human health and the environment with reasonable mitigative measures and was not technically viable or practicable.
Interstitial Space Around Clinkers or Marbles Filled with Lead or Graphite from Material Onsite
This option would use lead or graphite as the matrix material surrounding the clinkers or marbles of the vitrified product. Lead is considered to be a toxic material. In addition, the high density of lead would cause the glass to float, which would reduce its effectiveness in filling the interstices in the glass. At present, no experimental work has been done using graphite as a filler material. This alternative was rejected from further consideration because the technology was not sufficiently mature to allow detailed evaluation and was not technically viable or practicable.
C.3.3 WASTE TREATMENT
Burn Waste in a Breeder Reactor or Washington Public Power Supply System Reactor
This alternative suggested burning the waste in a breeder reactor or a Washington Public Power Supply System reactor with a result of 30 years of extra power. Under this concept, selected portions of the TWRS waste would be separated and incorporated into the fuel elements to be used in a breeder or power producing reactor. While certain isotopes in the waste would undergo nuclear decay in such an alternative, the vast majority of the waste would still require some sort of chemical separations and subsequent immobilization. This alternative was rejected from further consideration because the technology was not sufficiently mature to allow detailed evaluation and it is not technically viable and practicable.
Separation of Tritium
This option would segregate the tritiated waste from the tank waste and store it until the tritium decayed. As no practicable method has yet been discovered to separate tritium from water, the tritiated waste would not be concentrated. This alternative was rejected from further consideration because it was not technically viable and practicable.
C.3.4 HEALTH RISK, SAFETY, AND MITIGATION
Placing Berms Around Tanks
This alternative proposed placing berms around tanks to avoid the potential for an explosion when waste that contained a mixture of chemicals and nitrogen compounds was vitrified in situ. Another alternative proposed placing berms around tanks to avoid an explosion in a tank that would cause explosions in other tanks. This alternative would place berms around tanks to avoid explosions in nearby tanks should one of the tanks explode. However, the tanks are situated underground with approximately 6 m (20 ft) of soil fill between them. Should an explosion occur within a tank, the shock wave would have to penetrate the concrete liner of the tank and pass through the soil to affect the other tanks. The presence of a berm on the surface over the tanks would have little effect on this situation. Consequently, this alternative was rejected from further evaluation because it was not technically viable and practicable.
C.3.5 EMISSIONS, EFFLUENTS, AND MONITORING
Use Activated Carbon Filters and Encase Them in Lead or Stainless-Steel Containers
This alternative proposed trapping radioactive gases in activated carbon filters and encasing them in lead and stainless-steel containers that would be suitable for long-term storage. This recommendation was correct in that it anticipates the use of specialized filters to clean the contaminants from the gas streams from the treatment facilities. Activated carbon could be used to remove organic vapors (hydrocarbons) from gas streams. While small concentrations of hydrocarbons could be in the effluent streams from the treatment facilities, a greater concern would be removing radionuclide particles. This is done most efficiently by using high-efficiency particulate air filters as the last element of the gas treatment process. The used high-efficiency particulate air filters would be placed in LAW disposal vaults rather than encasing them in metal, particularly lead, which is a toxic material. Little experimental work has been done using activated carbon on gas streams generated by vitrification. This alternative was rejected from further consideration because the technology was not sufficiently mature to allow detailed evaluation and it was not technically viable and practical.
REFERENCES
Boomer et al. 1993. Boomer, K.D., S.K. Baker, A.L. Boldt, J.D. Galbraith, J.S. Garfield, C.E. Golberg, B.A. Higley, L.J. Johnson, M.J. Kupfer, R.M. Marusich, R.J. Parazin, A.N. Praga, G.W. Reddick, E.J. Slaathaug, T.L. Waldo, and C.E. Worcester. Tank Waste Technical Options Report. WHC-EP-0616, Rev. 0. Westinghouse Hanford Company. Richland, Washington. March 1993.
Boomer et al. 1991. Boomer, K.D., S.K. Baker, A.L. Boldt, M.D. Britton, J.D. Galbraith, J.S. Garfield, K.A. Giese, C.E. Golberg, B.A. Higley, K.L. Hull, L.J. Johnson, R.P. Knight, J.S. Layman, R.S. Marusich, R.J. Parazin, M.G. Piepho, E.J. Slaathaug, T.L. Waldo, and C.E. Worcester. Systems Engineering Study for the Closure of Single-Shell Tanks. WHC-EP-0405-1, Draft. Westinghouse Hanford Company. Richland, Washington. June 1991.
DOE 1995a. Tank Waste Remediation System Integrated Technology Plan. DOE/RL-92-61, Rev. 2. U.S. Department of Energy. Richland, Washington. February 1995.
DOE 1995b. Final Implementation Plan for the Tank Waste Remediation System Environmental Impact Statement. U.S. Department of Energy. Richland, Washington. 1995.
DOE 1995i. Safe Interim Storage of Hanford's Tank Waste Final Environmental Impact Statement. DOE/EIS-0212. U.S. Department of Energy. Richland, Washington. 1995.
DOE 1995q. Waste Acceptance System Requirements Document. DOE/RW-0351, Rev. 1. U.S. Department of Energy. Richland, Washington. May 1995
DOE 1987. Final Environmental Impact Statement, Disposal of Hanford Defense High-level, Transuranic and Tank Wastes Hanford Site Richland, Washington. Vol. 1 of 5. DOE/EIS-0113. U.S. Department of Energy. Washington, D.C. December 1987.
WHC 1995a. Other Options Data Package for the Tank Waste Remediation System Environmental Impact Statement. WHC-SD-EV-106, Rev. 0. Westinghouse Hanford Company. Richland, Washington. July 1995.
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