Jeremy M. Boak
Environmental Management Office
Los Alamos National Laboratory

Stanley T. Kosiewicz and Inés Triay
Chemical Science and Technology Division
Los Alamos National Laboratory

Kathleen Gruetzmacher and Andrew Montoya
Nuclear Materials Technology Division
Los Alamos National Laboratory

At present, >35% of the volume of newly-generated transuranic (TRU) waste at Los Alamos National Laboratory (Los Alamos) is not certifiable for transport to the Waste Isolation Pilot Plant (WIPP). Non-certifiable waste would constitute 900-1,000 m³ of the 2,600 m³ of waste projected during the period of the Environmental Management (EM) Accelerated Cleanup: Focus on 2006 plan [1]. Volume expansion of this waste to meet thermal load limits would increase the shipped volume to ~5,400 m³. This paper describes non-certifiable TRU waste streams at Los Alamos, and discusses prioritization of site-specific options to reduce generation of non-certifiable waste.

A team of Los Alamos TRU waste generators and waste managers reviewed historic generation rates and thermal loads and current practices. The team then projected the volume and thermal load of TRU waste streams for Fiscal Years 1999-2006, as well as the volume expansion required to meet the permissable thermal loads for all waste. These data defined four major problem TRU waste streams, including:

• 238Pu -contaminated combustible waste from production of Radioactive Thermoelectric Generators (RTGs) with ²³⁸Pu activity which exceeds thermal load limits by 10-100X.
• 241Am-contaminated cement waste from plutonium recovery processes (nitric and hydrochloric acid recovery) are estimated to exceed thermal load limits by ~3X.
• 239Pu-contaminated combustible waste, mainly organic waste materials contaminated with ²³⁹Pu and ²⁴¹Am, is estimated to exceed thermal load limits by a factor of ~2X.
• Oversized metal waste objects, (especially gloveboxes) cannot be shipped as is to WIPP because they will not fit in a standard waste box or drum.

The team evaluation defined ~30 projects which could reduce the total volume of certifiable waste through regulatory relief on the thermal limits, treatment of wastes to reduce volume and hydrogen content, and improved recovery of actinides from the process materials. Smaller teams developed:

1. five qualitative criteria (non-TRU waste generation, on-site health and safety, off-site environmental impact, regulatory acceptability, and technical feasibility)
2. three quantitative criteria (certifiable volume reduction, startup cost, and operating cost)
3. a simple linear scoring scheme and weights for the criteria
4. scores for the qualitative criteria
5. data to define scores for the quantitative criteria.

Review of results identified some problems with scoring structure and criterion weights, but the process was useful in identifying preliminary options for each major waste stream. A balance was struck between lower cost options for regulatory relief without waste avoidance, and higher cost options which meet Department of Energy missions for pollution prevention. The prioritization process produced defensible options that, if implemented, ensure generation of certifiable waste at rates which do not exceed available Los Alamos storage capacity during workoff of legacy TRU waste.

At present, >35% of the volume of newly-generated transuranic (TRU) waste at Los Alamos National Laboratory (Los Alamos) is not certifiable for transport to the Waste Isolation Pilot Plant (WIPP). Most of this non-certifiable TRU waste exceeds thermal load limits imposed by the TRUPACT II Safety Analysis Report Package (SARP) [2] as incorporated in the WIPP Waste Acceptance Criteria (WAC) [3]. The thermal limits are intended to reduce risks due to radiolytic generation of hydrogen gas during transportation. Thermal limits (in watts per drum) are set for various waste types, depending on the estimated gas generated during a very conservative transit time to WIPP. Non-certifiable drums of TRU waste could be repackaged to meet the thermal limits by putting less waste in each drum, increasing the total volume of TRU waste generated.

Non-certifiable waste would constitute 900-1,000 m³ of the 2,600 m³ of waste projected during the period of the Environmental Management (EM) Accelerated Cleanup: Focus on 2006 plan (EM Accelerated Cleanup Plan – formerly the Ten Year Plan - [1]). Volume expansion of projected Los Alamos TRU waste waste to meet thermal limits would increase the shipped volume to ~5,400 m³. This paper presents the results of efforts to define which TRU waste streams are non-certifiable at Los Alamos, and to prioritize site-specific options to reduce the volume of certifiable waste over the period of the EM Accelerated Cleanup Plan.

A systematic evaluation was conducted involving Los Alamos TRU waste generators and waste management organizations. The team reviewed historic generation rates and thermal loads and current practices to estimate the projected volume and thermal load of newly-generated TRU waste streams for Fiscal Years 1999-2006. These data defined four major problem TRU waste streams. Estimates were also made of the volume expansion that would be required to meet the permissable wattages for all waste. The four waste streams defined were:

238Pu-contaminated Combustible Waste – Production of Radioisotope Thermoelectric Generators (RTGs, the power sources for space applications and nuclear weapons, generates combustible waste with high ²³⁸Pu activity (10–100X over the WIPP WAC limits). Combustible materials, some of which have been reduced to ash through a thermal oxidation process, constitute the dominant waste stream from this process. Existing and expected quantities of this material would require packaging or repackaging to >1,300 m³ to be certifiable. This number was based on a review of existing residues stored at Technical Area (TA)–55, and projections assuming processing of five kilograms of ²³⁸Pu per year throughout the period of the EM Accelerated CleanupPlan.

241Am-contaminated Cement Waste – The processing of residues at TA–55 generates two ²³⁹Pu- and ²⁴¹Am-contaminated waste streams which are ultimately cemented at TA–55 or at TA–50. Nitric acid dissolution of a wide variety of plutonium-bearing residues and scraps results in nitrate-rich evaporator bottoms which are cemented at TA–55. Hydrochloric acid dissolution, mainly of processing salts from electrorefining processes, results in a high activity waste stream which is neutralized at TA–55 to produce hydroxide cake wastes and a slightly caustic waste stream. This stream is transferred to TA–50, Room 60, where it is neutralized with the lower activity overhead (condensate) stream from evaporation of the nitric acid process at TA–55. The neutralized waste stream is cemented. The caustic waste stream is presently responsible for only 0.3% of the volume, but ~80% of the radioactive content (in Curies) processed at TA–50. Current hydrogenous cements commonly exceed the allowable thermal limits by ~3X. Repackaging existing cement would be very expensive, time-consuming, and would result in increased worker doses. The estimated volume of waste to be generated over the period from FY 1999-2006 is ~284 m³. Expansion of this volume by three times would produce a final volume of ~850 m³.

Oversized Metal Waste Objects – Gloveboxes and other large metal objects will not fit in a standard waste box or drum. Size reduction and repackaging of these large objects requires availability of facilities which are closed (Waste Characterization, Reduction, and Repackaging Facility – WCRRF). Conservative estimates are that approximately 660 m³ of the 5,400 m³ of waste repackaged as certifiable containers will consist of such large metal objects and other metal wastes. These estimates are considered low, given the substantial reconfiguration of facilities at TA–3 (including the Chemical and Metallurgical Research Facility - CMR) and at TA–55.

239Pu-contaminated Combustible Waste – Combustible wastes constitute the largest volume of TRU waste generated at Los Alamos. Approximately 35% of the ~2,600 m³ of TRU waste projected to be generated by 2006 consists of such combustible materials. In addition to the large volume of this waste type, a significant fraction of the waste exceeds the thermal load limits, which are very restrictive for this waste type. Thus, large volumes of organic and other waste materials contaminated with ²³⁹Pu and ²⁴¹Am exceed thermal load requirements by a factor of ~2X.

The anticipated volumes from various major operations expected to continue throughout the period until the end of FY 2006 are shown schematically in the flow diagram of Figure 1. The thickness of the lines connecting various operations is proportional to the waste volume which would be generated if these wastes were packaged to meet thermal limits (note that residue volumes are not to scale).

Three main options have been identified for TRU-waste generating operations at Los Alamos. One relies upon changes in the regulatory structure driven from outside Los Alamos, whereas the other two involve procedural and technical changes in the operations of TRU-waste generating facilities at Los Alamos.

Option 1: Continue generating non-certifiable wastes – It is possible that currently non-certifiable waste could be certified for shipment to WIPP, through either an exception to, or changes in, the current regulatory requirements for certification of TRU waste. This option would require that Los Alamos be granted such an exception or change as a result of DOE interaction with the Nuclear Regulatory Commission, which defines the transportation requirements for radioactive materials for the Department of Transportation. Such an interaction would probably be accompanied by active intervention of the state or states affected by the changes in transportation requirements. A similar strategy may be pursued by the Rocky Flats site with respect to certification of certain residues for shipment to WIPP. However, an adverse regulatory finding would force a large scale, expensive repackaging program in the future.

Option 2: Stop generating non-certifiable TRU waste by reducing the amount of waste disposed per drum. – TRU waste generating organizations could be directed to generate only wastes which are certifiable for WIPP. This change in operations would:

1. more than double the volume of newly generated TRU waste during FY 1999-2006,
2. delay operations at TA–55 when waste handling operations became bottlenecks for Pu processing.
3. increase the cost of handling, treatment, and storage by ~$140 million, and

The additional cost of pursuing option 2 would be approximately $140,000,000. This estimate is based upon costs for TRU waste characterization, treatment, storage and transportation, which currently amount to approximately $10,000 per drum, or ~50,000 per m³ [5].

Option 3: Stop generating non-certifiable TRU waste through technological and scientific solutions - Using available and developmental technology, Los Alamos can ensure certifiable waste generation, in volumes less than or equal to those in the EM Accelerated Cleanup Plan, at a cost of ~$34 million over the same period. The projects proposed to reduce the volumes of non-certifiable TRU waste are summarized in the review of results. The process used to identify and assign priority to these projects is discussed in the next section.

Definition of certifiable waste problems and options: A Los Alamos TRU Waste Management Team evaluation defined ~30 projects which could reduce the volume of certifiable waste through regulatory relief on the thermal limits, treatment of wastes to reduce volume and hydrogen content, and improved recovery of actinides from the process materials. The projects evaluated are listed in Table I.

Development of scoring criteria and scoring of options: Subsequently, a smaller team developed a set of five qualitative criteria (non-TRU waste generation, on-site health and safety, off-site environmental impact, regulatory acceptability, and technical feasibility) and three quantitative criteria (certifiable volume reduction, startup cost, and operating cost). Example criteria and scoring schemes are shown in Table II. Note that, for the startup cost criterion, the criterion weight is negative, to ensure that cost-effective projects were favored. The team established a simple linear scoring scheme and weights for the criteria, and scored the projects against the qualitative criteria. A subgroup of this group assembled the data for the quantitative criteria. In this process, some projects were combined. The scores for individual projects are shown in Table I. In addition, the scores and standard deviations are shown in Table II.

Some problems arose with the scoring structure and criterion weights, but the process was useful in identifying preliminary options for each major waste stream. For example, the variability in scoring on most of the subjective criteria was significant. There was little time to discuss the rationale of various team members for their scores, which might have resolved uncertainties and perspective differences. Ideally, such a discussion would have been followed by a second round of scoring of options. The limited discussion that did take place suggested that, although most team members had some familiarity with the scope and purpose of all the proposed options, a better definition of each would have enhanced the consistency of scoring, and given a truer measure of the costs and benefits of each project.

These problems could readily be resolved in a second scoring of further options for reduction of TRU waste volume. Given the scale (cost, and volume of waste) of the problem, dedication of resources to a more refined evaluation would be warranted. Such an effort should include some training in decision analytic techniques. Preparation of more detailed process flow sheets like the high-level one in Figure 1 to demonstrate the effect of each option on TRU waste generation would enable consistent evaluation by a dedicated team of experts.

The final scores for approximately eighteen consolidated options led to the selection of five projects to be carried forward. To avoid multiple projects addressing the same waste stream, some high scoring options were eliminated. That is, once a primary project had been identified for a given waste stream, the benefit of other projects to address this waste stream was considered to be substantially less. Also, some additional criteria were considered in the final decision to select the options to pursue. These criteria had not been included in the original scoring. For example, the selection of Molten Salt Oxidation and Aqueous Recovery for ²³⁸Pu-contaminated combustible waste was driven in part by the additional requirement for recovery of as much of the ²³⁸Pu as possible to meet the mission needs of the group responsible for heat-source production. Although it would have been preferable to revise the criteria, and rescore the options, time was not available for this effort.

One project was identified which addressed all waste types, and incorporated three options listed in Table I. These were the G-values, ANSI Standards, and Hydrogen getters projects. These all address improvements in the technical basis for thermal loading waste acceptance criteria. Together, they have the potential to alleviate most or all of the problem of TRU waste which exceeds the current thermal load limits. Other projects were identified for each major non-certifiable waste type because of residual uncertainty about when and whether these modifications to the requirements structure would take effect.

As mentioned above, some projects, if completed, would change the volume reductions available to other projects. This lack of independence constituted a flaw in the approach which had to be overcome by subjective estimation of its significance. Ideally, the evaluation would have taken the form employed by the WIPP program in the Systems Prioritization Method analysis [5]. In that evaluation, combinations of activities were evaluated as "activity sets" and the cost and probability of demonstrating compliance were calculated for combinations. The time and resources allocated to the present evaluation were insufficient to do such an analysis of these options.

A balance was struck between lower cost options for regulatory relief without waste avoidance, and higher cost options which meet Department of Energy missions for genuine pollution prevention. The prioritization process produced defensible options that, if implemented, ensure generation of certifiable waste at rates which do not exceed available storage capacity during workoff of legacy TRU waste.

The results are strongly dependent upon assumptions in the waste volume projections made for the next ten years. Routine TRU waste generation at TA–55 is dependent upon program activity at the Plutonium Facility. This dependence is illustrated in Figure 3, which shows the correlation of annual routine TRU and mixed TRU waste volume with plutonium-handling transactions as recorded in the Materials Accountability and Surveillance System. Thus, the cost savings and volume reduction potential of all projects would be substantially reduced if activity declined.

It is important to note that the intercept in this plot is not at zero TRU waste volume. The zero-activity waste volume appears to reflect the waste generated if the facility were placed in "hot stand-by," with TRU wastes being generated by mandated cleanouts of glovebox lines, and similar activities. It is not clear that the actual zero activity waste volume would be this high, as the apparent linearity of the trend might break down at such low activity levels. However, many activities have such base levels, not only for waste, but for cost. Thus, projects designed to a certain capacity could be expected to have higher base levels. It is unlikely that this effect would be uniform on all projects, so that significant changes might occur in the relative rankings of projects to reduce certifiable TRU volume. Uncertainties in the projected waste volume can make the difference between economic viability and failure for many such waste minimization projects. Thus, refinements in models for waste volume projection constitute an important aspect of waste minimization efforts.

Based on the scoring completed by the team, and the considerations listed above, the following projects were recommended for rapid implementation to address these issues:

Molten Salt Oxidation and Aqueous Recovery – The molten salt oxidation process was developed by Rockwell, Inc. The system uses a molten sodium carbonate bath to oxidize the organic material in the waste stream, removing hydrogen, and reducing the volume by a factor of ~10. Aqueous recovery of plutonium from the carbonate salt further reduces the waste volume by approximately another factor of ten, and enables reuse of a material worth approximately $2,000/gram. The cost is approximately $3.0 million for startup, with $5.0 million operating costs (over the period from startup to 2006) to eliminate ~1300 m³ of 5,400 m³ certifiable waste volume and to recycle the plutonium.

Vitrification – Vitrification was identified as a primary option for reduction in the volume of non-certifiable homogeneous (cemented) TRU waste in FY 1997. Defense Programs money was transferred to Idaho National Engineering and Environmental Laboratory (INEEL) to design and construct a vitrification unit to replace cementation of the nitric acid process evaporator bottoms at TA-55 at Los Alamos. Site preparation is currently under way, and the unit is expected to be installed during Fiscal Year (FY) 1999. Vitrification will reduce the volume, and the hydrogen content of this waste stream, thus allowing higher density of waste material. The system will cost $3.0 million through startup, and an additional $5.0 million to operate (from FY 1999-2006), and will avoid ~500 m³ of 5,000 m³. The system may ultimately be expanded to deal with combustible wastes, although vitrification was not an effective stand-alone option for the combustible waste streams.

Electrochemical Ion Exchange – AEA (Great Britain) is currently testing electrochemical regeneration of ion exchange resins as a means to separate much of the Pu and Am from the caustic waste stream. This system would be implemented first at TA-50, with the recovered actinide material returned to TA-55. If the system is successful in reducing the activity, 15-150 m³ of homogeneous (cemented) waste could be avoided by 2006. The system will cost ~$500,000 to design and install, and will result in operational savings at TA-50. Additionally, results of operations at TA-50 may provide support for implementation at TA–55, eliminating the hydroxide precipitation step in the hydrochloric acid process line. The resultant savings would be of the order of 3-15 m³/year.

Decontamination and Compaction/Recycle of Metal Waste – Los Alamos is currently teaming up with Rocky Flats Environmental Technology Site to deploy systems to decontaminate large metal objects (mostly gloveboxes) as part of the Technology Deployment Initiative. This project will involve construction of a portable decontamination system for gloveboxes which can be safely removed for decontamination. The system will also compact the resulting decontaminated metal to fit standard drums, and recycle any cleaning solutions. In addition, the project will deploy a LosAlamos-designed in-situ electrolytic deconamination system which has even enabled reuse of gloveboxes. The project requires startup funding of $1.0 million, and $1.5 million per year to avoid a minimum of 600 m³ of metal waste. The ultimate potential for TRU waste avoidance is >3,000 m³.

In-line Assay and Bagless Drumout – Streamlining of waste packaging at TA-55 will allow monitoring of waste within the glovebox line, thus avoiding bagout waste volume, which consists of unneeded plastic and entrapped air. The full project permits additional sorting and segregation to minimize hydrogen generation, and decrease the volume of ²³⁹Pu-contaminated combustible waste. The project requires $3.6 million in facility modifications and equipment purchase, and ultimately will streamline TRU waste processing operations (no additional cost, probable savings). In addition, the project will avoid ~800 m³ of 5,400 m³ of certifiable TRU waste.

Improved Technical Basis for Waste Acceptance Criteria – This project consolidates efforts, some already in progress, to:

• test the gas generation potential of various materials,
• test the potential of hydrogen getters and recombiners to alleviate the needs for limits to the radiolytic generation of hydrogen during transportation, and
• develop an ANSI standard for gas generation testing and thermal limit calculation under appropriate quality assurance procedures.

The $1.0 million project completes efforts to increase the accuracy of thermal limits and the technical basis for use of hydrogen getters to increase allowable loading.

The Los Alamos TRU waste team has identified a number of currently generated TRU waste types which are not certifiable for transport to WIPP. These include ²³⁸Pu-contaminated combustible wastes from RTG production, ²⁴¹Am-contaminated homogeneous (cemented) waste, oversized metal objects, and some ²³⁹Pu-contaminated combustible waste. The team examined a wide range of options to address this issue of noncertifiability.

The five projects described in the previous section would solve most of the problems with non-certifiable wastes at Los Alamos, and would also support similar efforts at other DOE sites. In addition, several of these options will actually reduce the amount of waste generated (in kilograms or curies) by current and future missions of the weapons program. Some portion of the large volume of legacy wastes also is not currently certifiable for transportation to WIPP, and these projects are applicable to those wastes as well.

The evaluation process used to identify these problems is readily adaptible to broader concerns of the National TRU Waste Program, and is similar in approach to other efforts to prioritize the Program’s activities (for example, the System Prioritization Method [5]). With further refinement, and the development and operation of a dedicated team, the process could be used to address the full range of technology development and deployment issues facing the Program.

1. DOE (1997) Accelerating Cleanup: Focus on 2006, DOE Environmental Management Report DOE/EM-0327, Washington, DC, 98p.
2. DEPARTMENT OF ENERGY [DOE], TRUPACT II Safety Analysis Report for the TRUPACT II Shipping Package (SARP), Nuclear Regulatory Commission Docket No. 9218, Washington DC (1994)
3. DOE, Waste Acceptance Criteria for the Waste Isolation Pilot Plant, Revision 5, WIPP-DOE-069. DOE Carlsbad Area Office, Carlsbad, NM (1996)
4. K. HSU, M. BURNS, S. PRIEBE, P. ROBINSON, Avoidable Waste Management Costs, Idaho National Engineering Laboratory (INEL) Report INEL-94/0205, Idaho Falls, ID, 233 p. (1995)
5. PRINDLE, N. H., MENDENHALL, F. T., BOAK, D. M., BEYELER, W., RUDEEN, D., LINCOLN, R. C., TRAUTH, K., ANDERSON, D. R., MARIETTA, M. G., AND HELTON, J. C., The Second Iteration of the Systems Prioritization Method: A Systematic Prioritization and Decision-Aiding Tool for the Waste Isolation Pilot Plant, Volume 1: Synopsis of Methods and Results. Sandia National Laboratory Report SAND95-2017/1. Albuquerque, NM, 180p. (1996)

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