Waste Form Initiative Close Out Report Draft

Transcription

1 INEEL/EXT February 1998 Waste Form Initiative Close Out Report Draft

2 INEEL/EXT Waste Form Initiative Close Out Report Draft Published February 1998 Idaho National Engineering and Environmental Laboratory Mixed Waste Focus Area Lockheed Martin Idaho Technologies Company Idaho Falls, Idaho Prepared for the U.S. Department of Energy Office of Science and Technology Under DOE Idaho Operations Office Contract DE-AC07-94ID13223

3 ABSTRACT The U.S. Department of Energy (DOE) owns approximately 130,000 m 3 of mixed waste. Mixed waste is defined as waste that contains both hazardous and radioactive contaminants. The hazardous constituents are regulated under the Resource Conservation and Recovery Act (RCRA). The radioactive constituents are governed under Atomic Energy Act (AEA). The DOE mixed waste inventory must be treated and disposed in accordance with both RCRA and AEA requirements. RCRA is very prescriptive in regard to the treatment processes and standards that must be met to render a waste acceptable for shallow land burial, or, in other words, disposable. However, the treatment processes mandated by RCRA can significantly volume reduce the waste, resulting in a concentration of radionuclides that exceeds the waste acceptance criteria of the disposal facilities. The Mixed Waste Focus Area initiated a study to analyze the treatment processes planned for the mixed waste inventory and evaluate the projected final waste forms for disposability, based on resulting radionuclide concentrations. The primary purpose of this effort, named the Waste Form Initiative (WFI), was to identify problematic waste streams, define why they cannot be disposed, determine how to best address the problems, and establish technology development projects to resolve the deficiencies. The results of the WFI studies indicate that the majority of the DOE mixed waste can be disposed, after treatment, and no further technology development efforts are warranted at this time. iii

4 iv

5 EXECUTIVE SUMMARY The Waste Form Initiative (WFI) was implemented by the U.S. Department of Energy (DOE) Mixed Waste Focus Area (MWFA) in August 1996 to address the waste form performance deficiency identified in the first technical baseline report of the MWFA. The deficiency noted that the Environmental Protection Agency promulgated specific regulations dealing with the performance of hazardous waste forms and that no such requirements have been established for low-level radioactive waste. After consulting with its EM-30 site customers, the MWFA initiated an analysis of mixed low-level waste (MLLW) streams considered potentially problematic in terms of having sum-of-fraction values that may exceed 1 by an order of magnitude or more based on radiological limits of site-specific waste acceptance criteria (WAC). These potentially problematic waste streams were identified in a residuals analysis project conducted by Sandia National Laboratories (SNL) for the DOE Disposal Workgroup. SNL conducted the refined residuals analysis for the MWFA by comparing radionuclide concentrations in the potentially problematic waste streams with the radiological limits in the WAC for the disposal sites at the Hanford Reservation and Envirocare of Utah. The results of these analyses indicated that Hanford could likely accept almost all of the potentially problematic waste streams and may be able to accept all wastes with additional analysis. Envirocare could likely accept approximately one third of the potentially problematic wastes. This study dealt only with wastes that had sufficient characterization to allow comparisons with WACs to be made. There are approximately 8700 m 3 of waste that are insufficiently characterized to permit selection of a treatment process; another 27,000 m 3 did not have radiological characterization. Additionally, the study did not deal with issues associated with compatibility between the wastes and waste forms. Based on these results, the MWFA concluded that the WFI had fulfilled its mission and prepared a recommendation to close out the initiative. This recommendation and the draft report by SNL were reviewed by the Site Technology Coordination Groups, an American Society of Mechanical Engineers review panel, and the National Research Council s Subcommittee for Mixed Waste, a subcommittee of the Committee for Environmental Management Technology. With few exceptions, these reviewers agreed with the conclusions of the report and the recommendation to close out the initiative. The exceptions are reviewed and discussed in this report. Based on results of analyses and the feedback from reviewers, the current thrust of the WFI is complete. The primary responsibility for solving the remaining technical issues for specific waste streams remains with the sites owning the wastes. v

6 vi

7 CONTENTS ABSTRACT... EXECUTIVE SUMMARY... ACRONYMS... iii v ix 1. INTRODUCTION BACKGROUND FY1996 Technical Baseline FY1997 Technical Baseline WFI Strategy Initial Strategy Cost Model SUMMARY OF THE WFI RESIDUALS ANALYSIS PROJECT Conclusions of the SNL Report Recommendations of the SNL Report REVIEW, COMMENTS, AND CONCURRENCE Internal DOE Review External to DOE Reviews CONCLUSIONS REFERENCES FIGURES 1. Disposition of waste volumes for treated MLLW Classification of potentially problematic waste streams based on categories in the Hanford WAC Classification of potentially problematic waste streams based on the Envirocare WAC vii

8 viii

9 ACRONYMS ASME CEMT DOE DOE/SR EM EPA FFCAct INEEL LANL LDR LLW MLLW MPC MWFA MWIR NRCC NTS OST PA PE R&D RA RCRA SNL American Society of Mechanical Engineers Committee on Environmental Management Technologies Department of Energy Department of Energy/Savannah River environmental management Environmental Protection Agency Federal Facilities Compliance Act Idaho national Engineering and Environmental Laboratory Los Alamos National Laboratory land disposal restrictions low-level waste mixed low-level waste Matrix parameter categories Mixed Waste focus Area Mixed Waste Inventory Report Nuclear Regulatory Commission Nevada Test Site Office of Science and Technology performance assessment performance evaluation Research and Development residuals analysis Resource Conservation and Recovery Act Sandia National laboratories ix

10 SOF SRS STCG TCLP WAC WFI WSRC sum-of-fractions Savannah River Site Site Technology Coordination Group toxicity characteristic leaching procedure waste acceptance criteria Waste Form Initiative Westinghouse Savannah River Company x

11 Waste Form Initiative Close Out Report 1. INTRODUCTION The U.S. Department of Energy (DOE) Mixed Waste Focus Area (MWFA) was requested in March 1996 by the DOE Office of Science and Technology (OST) to develop and lead a program that would address and resolve issues associated with final waste form performance, as related to treatment and disposal of the DOE mixed waste inventory. This program, named Waste Form Initiative (WFI), had the primary goal of ensuring that the mixed waste treatment technologies being developed, currently used, or planned for use by DOE produce final waste forms that would satisfy the waste acceptance criteria (WAC) of the existing and/or planned mixed waste disposal facilities. The U.S. Nuclear Regulatory Commission (NRC) and the U.S. Environmental Protection Agency (EPA) have published proposed guidance in 57 FR 10508, Proposed Guidance Document on the Testing of Mixed Radioactive and Hazardous Waste 1, related to management of mixed waste. The EPA guidance stipulates that all mixed wastes under their jurisdiction (i.e., waste with low-level radioactive and hazardous constituents) are subject to both radioactive and hazardous material regulations, which entail treatment, storage, and disposal. The hazardous components in DOE mixed wastes are regulated by federal EPA or a state agency with delegated authority under the Resource Conservation and Recovery Act (RCRA). A waste is considered hazardous, and thus regulated by RCRA, if it contains any contaminant listed in 40 CFR 261, Identification and Listing of Hazardous Wastes 2, or exhibits the characteristics of reactivity, corrosivity, ignitability, or toxicity, as defined by RCRA 40 CFR 261 Subpart C and is not specifically excluded. In general, RCRA-regulated hazardous wastes must be treated in compliance with the applicable treatment standards defined in 40 CFR 268, Land Disposal Restrictions 3 (LDRs) prior to shallow land burial. The RCRA regulations define technology-based, concentration-based, and universal treatment standards for LDR compliance. In addition, hazardous waste management facilities must meet the technical standards required in 40 CFR 264, Standards for Owners and Operators of Hazardous Waste Treatment, Storage, and Disposal Facilities 4. The radioactive components of DOE MLLW are regulated under DOE Order A, Low-Level Radioactive Waste Management and Disposal 5, currently being revised. DOE sites with low-level waste (LLW) or MLLW disposal facilities must comply with the performance objectives defined in Order A by conducting site-specific performance assessments (PAs) for those disposal facilities to ensure that disposed inventories will not exceed certain dose-based performance objectives. Additionally, WACs must be defined for each disposal facility to ensure compliance with these performance objectives and to establish performance standards for final waste forms. DOE Order A also allows disposal of LLW at commercial facilities, on a case-by-case basis, through an established exemption process. Facilities for disposal of MLLW must also meet the state or federal requirements for hazardous waste disposal. The WACs for commercial LLW disposal facilities are defined through compliance with NRC requirements delineated in 10 CFR 61, Licensing Requirements for Land Disposal of Radioactive Waste 6 ; and through the applicable State licensing process. 1

12 2. BACKGROUND The Assistant Secretary for the Office of Environmental Management (EM) at the U.S. DOE established focus areas as a new approach to environmental research and technology development. The MWFA was formed to develop and facilitate implementation of technologies required to meet the Department s commitments for characterization, treatment, and disposal of mixed low-level waste (MLLW) and mixed transuranic wastes (MTRU). The mission of the MWFA is to provide acceptable processing systems that are capable of treating DOE s existing and projected mixed waste inventory, in accordance with RCRA LDRs, so that the final waste form can be disposed. To accomplish this mission, the MWFA developed and maintains a technical baseline that identifies and prioritizes the technology deficiencies associated with management and disposition of the DOE mixed waste inventory. A deficiency represents some roadblock related to a technical aspect of characterization, treatment, handling, or disposal of mixed waste, as identified by EM customers throughout the DOE complex. 2.1 FY1996 Technical Baseline The MWFA established the first technical baseline in fiscal year 1996 (FY1996). This baseline was accomplished by working with DOE site representatives and other technical experts to evaluate the waste management strategies, capabilities of existing and planned facilities, and the existing and projected inventory characteristics. The deficiencies identified were prioritized based on such factors as affected waste volume, number of customers, number of affected waste streams, risk associated with the stored waste, related compliance commitments, etc. The FY1996 MWFA technical baseline included 30 prioritized deficiencies. The fourteenth ranked deficiency was titled Waste Form Performance. This deficiency was defined as follows: The performance criteria for regulated hazardous constituents are generally established in State and Environmental Protection Agency (EPA) regulations, such as Toxicity Characteristic Leaching Procedure (TCLP) requirements. No such requirements have been finalized for radionuclides, so the increased durability of vitrified, slagged, or encapsulated waste forms has not been incorporated into disposal facility permitting or performance assessments. An objective, technically defensible evaluation of the long-term performance of advanced waste forms must be conducted. The evaluation must satisfy regulator and stakeholder concerns to allow flexibility in siting and operating low level waste disposal facilities to best exploit the more durable, higher waste-loading forms. The MWFA implemented WFI to address this deficiency. As noted above, the EPA regulations define the performance criteria for final waste forms relative to hazardous constituents. In fact, these requirements often dictate a final waste form, through technology-based treatment standards, for which very little radionuclide leaching data is available. In addition, DOE has been developing and testing certain advanced waste forms (i.e., glass, ceramics, polymers, etc.) that are expected to provide long-term stabilization of radionuclides. Long-term performance data for these waste forms are also very limited. Primarily due to this lack of long-term performance data, the PAs that have been developed for DOE LLW disposal sites give only short-term credit to waste form performance in the algorithms used to determine the disposability of a specific waste form. The original goal of the WFI was to develop the data and analytical tools needed to (a) help determine the most appropriate final waste form and (b) provide technical justification for incorporating long-term waste form performance into PAs. If this goal 2

13 could be accomplished to the satisfaction of regulators and stakeholders, the conservatism built into the existing methodologies used to determine the disposability of a final waste form would be greatly reduced while the cost-effectiveness of the DOE mixed waste treatment systems would be increased. 2.2 FY1997 Technical Baseline The MWFA technical baseline development process was repeated in FY1997 using similar techniques and criteria to identify and prioritize the deficiencies. The waste form performance deficiency ranking and definition were modified in the FY1997 technical baseline. The primary reason for these changes was due to the preliminary results from the Residuals Analysis (RA) project 8 being conducted by Sandia National Laboratories (SNL). Although the PAs do not consider long-term waste form performance in determining the disposability of a final waste form, these initial RA analyses indicated that relatively few waste streams actually pose a disposability problem in their planned final waste form. (The results of the RA are discussed in detail in Section 4 of this report.) Consequently, the emphasis of the MWFA WFI was revised to provide an objective, technical justification for determining when the use of an advanced waste form is appropriate. For the FY1997 MWFA technical baseline, the waste form performance deficiency was ranked fourth, primarily due to the near-term closure of what had originally been identified as a deficiency with potentially significant impact to the DOE mixed waste inventory. Based on the revised focus of the WFI, the deficiency definition provided in the FY1997 MWFA technical baseline is as follows: The performance criteria for regulated hazardous constituents are generally established in State and EPA regulations, such as TCLP requirements. No such requirements have been finalized for radionuclides, so the increased durability of vitrified, slagged, or encapsulated waste forms has not been incorporated into disposal facility permitting or performance assessments. An objective, technically defensible evaluation of the value of advanced waste forms in disposal site performance assessments is being conducted. Data needs identified in the evaluation will be addressed as required. This close out report documents the activities performed as part of the WFI and their results. 3

14 3. WFI Strategy The strategy for WFI activities evolved over the course of the project. The initial strategy was based on a set of ideas and assumptions that, although they were generally accepted as accurate by cognizant DOE technical personnel, had not been analyzed and demonstrated to be true. The WFI effort focused solely on MLLW; MTRU and any evaluation of disposal at the Waste Isolation Pilot Project (WIPP) were not considered. The following are the assumptions that formed the initial basis for the WFI effort: MLLW would be required to be treated to meet RCRA-defined criteria prior to disposal. RCRA-required treatment of MLLW would result in a disposable final waste form. PA methodologies were adequate for establishing permissible exposure based on release of radionuclides from the disposal site. Radionuclide limits established through PA modeling were conservative due to the fact that they did not take into account long-term waste form performance. Radionuclide limits established through PA modeling would restrict a significant volume of MLLW from disposal due to conservative assumptions associated with waste form performance. Existing performance data specific to waste form and radionuclide species were not sufficient to effectively evaluate the disposal options available for a significant fraction of the DOE MLLW inventory. An evaluation of DOE-wide disposal options had not been performed. These assumptions were based on interactions with staff at Hanford, Idaho National Engineering and Environmental Laboratory (INEEL), Los Alamos National Laboratory (LANL), Savannah River Site (SRS), and SNL who were knowledgeable of the issues associated with the PA and the disposal of MLLW. The basic premise of the WFI from the start of the project was that determining acceptable disposal pathways for MLLW depended on site- and waste-specific attributes. A generic or global evaluation of the disposal issues would not result in the identification of research and development activities at the level of detail necessary to affect site operations. 3.1 Initial Strategy The initial strategy was proposed in August The main objective was to clearly establish the impact of including some measure of waste form performance in the PA methodology for estimating radionuclide release and thus exposure. The activities identified in the strategy were intended to be a direct comparison of radionuclide releases assuming that (a) no credit was taken for long-term waste form performance and (b) long-term and advanced waste form performance was included in the PA model. The strategy revolved around the evaluation of two specific sites: a humid site where the exposure pathway from groundwater is significant and an arid site where exposure from this pathway is minimal. The selection of sites was limited to those that had a well-developed PA for LLW. Hanford was selected as a representative arid disposal site, and SRS was selected as a representative humid site for evaluation. Initially, the disposal site at the Nevada Test Site (NTS) was selected as the representative arid site for 4

15 evaluation. This selection was later modified based on the recommendation of SNL and the recognition that NTS does not include a groundwater pathway in their exposure calculations due to the specific hydrological characteristics of the site (primarily low precipitation, high evapotranspiration, and great depth to groundwater in the region of the disposal site). The strategy identified the following activities: Identify existing waste form performance data for grout, glass, and polyethylene, and document specific radionuclides and performance conditions evaluated. Work directly with the organizations responsible for the PAs at Hanford and SRS to identify and incorporate modifications to established models necessary to account for long-term and advanced waste form performance. Use existing waste form performance data in the modified PA to determine the impact of long-term and advanced waste form performance on radionuclide release limits and maximum radionuclide concentrations. Review the MLLW inventory, and compare proposed waste form/radionuclide data with existing waste form performance data. Identify data gaps (e.g., waste form/radionuclide combinations for which no waste form performance data exists). Issue a Call for Proposals to generate data to fill identified gaps. Use data generated from the Call for Proposals to update and expand the evaluation of impacts of modifying PAs to include waste form performance. Document the results and methodology employed. The intent of the activities identified in the initial strategy was to establish the extent to which accounting for long-term and advanced waste form performance in estimating radionuclide release affected the disposal limits for a specific site. It was also intended to serve as an example of how longterm and advanced waste form performance could be included in PA models. Incorporation of this methodology would then be based on site-specific considerations and could be applied at any number of disposal sites with the appropriate modifications. A second component of the initial strategy was to construct a tool for use by site waste management operations to determine the acceptability of waste forms for disposal prior to treatment. These activities were based on the original assumption that a significant volume of MLLW would be restricted from disposal based on limits established by conservative PAs and on the implicit assumption that the modification of PA models to include long-term and advanced waste form performance would significantly expand the radionuclide limits for a given disposal unit. The tasks identified were to be performed by SNL based on previous work sponsored by the Disposal Workgroup 7. A methodology for evaluating disposal sites had previously been established by SNL and was based on maximum allowable radionuclide inventories using a simplified PA model called the Performance Evaluation (PE). The concept was to construct disposal unit-specific PEs for Hanford and SRS that included short-term waste form performance considerations and then to evaluate potentially problematic waste streams identified in the SNL RA report 8 (see Section 4). These waste streams had been identified as exceeding the disposal criteria for selected sites based on a conservative estimate of radionuclide concentration, final waste form, and disposal limits used in the RA project 8. The modified PE models would serve as a proof-of-concept 5

16 for evaluating the impacts of long-term waste form performance and allow sites to modify the selection of waste form and/or waste loading to establish disposal options. Potentially problematic wastes were targeted based on the results of the RA, which showed that these wastes exceeded disposal limits and that selection of alternative waste forms may affect the disposability of the waste. The initial strategy outlined in this section was documented in an Integrated Project Plan and the FY 1997 Project Execution Guidance (PEG) for the WFI. The strategy was presented at a meeting of the EM-30 DOE-Headquarters/Field Office representatives in Las Vegas, Nevada, to get feedback on the direction of the WFI and concurrence that the activities proposed would address EM-30 needs. The general consensus of the group was that the disposal of MLLW was not an issue that required MWFA attention. The contention put forward by this group was that the limits established for both Hanford and NTS would allow disposal of a majority of MLLW without waste form performance modifications to the PA. The group also recommended that DOE limit the development of MLLW disposal units as a costsaving measure. They suggested that DOE use Hanford as the primary DOE facility, use NTS as a backup option for the wastes that Hanford could not accept, and continue to pursue the commercial disposal option as necessary. The WFI strategy was modified as a result of the feedback received at the Las Vegas meeting. The emphasis and activities shifted to determining and documenting the acceptability of the treated DOE MLLW inventory at Hanford and Envirocare under the existing WAC. This focus was adopted to directly establish whether the initial assumption (that radionuclide limits established through PA modeling would restrict a significant volume of MLLW from disposal due to conservative assumptions associated with waste form performance) was in fact the case. Activities were initiated to refine the RA approach and to compare the estimated radionuclide concentrations in the final waste form against the WAC for Hanford and Envirocare. The MWFA position was that the path forward for the WFI was dependent on defining the problem: activities associated with waste form performance and modification of PA models would be pursued only if there was a significant volume of MLLW that exceeded established disposal limits, and all activities would be directed at specific problems (i.e., those waste streams/waste forms for which disposal was a problem). Development of a PE waste form tool for EM-30 operations was suspended pending the outcome of the problem definition. Activities funded in FY 1997 are described in the modified PEG included in Appendix A. A discussion of the refined RA approach and results and the problem definition activities is presented in Section Cost Model Another major product envisioned for the MWFA WFI was an analytical tool that would allow end-users to evaluate the cost-effectiveness of specific waste forms. For example, using Portland cement to stabilize a certain waste stream may be an acceptable treatment process that could result in a final waste form that meets the RCRA LDRs for shallow land burial. However, due to the specific contaminants, the allowable waste loading may be very low (e.g., 15 wt%). The proposed model would allow site operations to evaluate the cost-effectiveness of more expensive processes (e.g., chemicallybonded phosphate ceramics, vitrification, etc.) and determine the economics associated with improved waste loadings. Higher waste loadings generally result in lower packaging, transportation, and disposal costs. The system would allow simultaneous evaluation of these factors, as well as other process limitations that must be addressed relative to the specific waste stream. For instance, the analysis must consider the maximum waste loading that would allow the final waste form to satisfy the WAC of the disposal facility for radionuclide concentration. This maximum waste loading would directly impact the actual cost-effectiveness of the treatment process. 6

17 The effort to develop this tool was coordinated with the Waste Form Cost Study (WFCS), directed out of DOE-HQ. The MWFA WFI representatives met with those implementing the WFCS to define the appropriate capabilities of this cost/benefit analysis tool. Significant diversity of opinions regarding the complexity and utility of the tool existed among the technical experts involved in this evaluation. As a result, a decision was made to get direct input from the targeted end-users throughout the DOE complex to determine the true needs of such an analytical model. All the major DOE sites were contacted and given a description of the proposed analytical tool. 10 The sites were asked to submit comments to the MWFA regarding the features they would prefer in such a model and their perceived usefulness of such a tool. Response was weak, but those sites that did contact the MWFA generally indicated that they did not support development of such a tool. This was primarily based on the opinion that each waste stream was too unique to generalize in a model. Consequently, the sites felt that development of a tool that could be flexible enough to provide decision-making data was doubtful. Accordingly, the MWFA discontinued efforts to develop such an analytical model, and the WFCS resumed its original scope. The results of the WFCS effort is documented in the draft WFCS report 11. 7

18 4. SUMMARY OF THE WFI RESIDUALS ANALYSIS PROJECT In August 1996, the MWFA requested that SNL evaluate the disposability of certain potentially problematic MLLW streams that they had recently identified based on the PE scoping analyses. These scoping analyses on disposal issues 7 have been conducted by SNL for the FFCAct Disposal Workgroup. The disposal capabilities of fifteen sites selected through this process were quantified and qualified in the scoping-level PE project completed in early An additional scoping-level RA project 8 provided estimates of volumes and radionuclide concentrations for treated MLLW that were based on DOE s current and five-year projected inventory of approximately 130,000 m 3 and approximately 1700 waste streams (Figure 1). After treatment, approximately 89,000 m 3 of the remaining waste would be required to be disposed of as MLLW. Of this amount, all but 105 waste streams (approximately 6000 m 3 ) were shown to be disposable at one or more potential DOE sites. These remaining 105 waste streams were dubbed potentially problematic, indicating that more refined analyses may demonstrate that they are also acceptable for disposal. The 105 waste streams each had a sum of fractions (SOF) that was at least an order of magnitude greater than 1 based on the concentration limits derived from the PE project for the Hanford Reservation. In the analysis that forms the basis for this close out report 9, the radionuclide concentrations of these 105 waste streams were compared with the WAC for the LLW disposal facility at Hanford (the WAC for a MLLW facility at Hanford are not yet complete) and with the WAC for Envirocare s commercial disposal facility for MLLW in Utah. At Hanford, the WAC are based on the LLW PA recently completed for its currently operating shallow land burial site. The WAC provide limiting activity concentrations for Category 1 and Category 3 wastes, which correspond to the PA results of the homesteader and post-drilling intruder scenarios, respectively. Envirocare of Utah is a licensed commercial MLLW disposal site. Although details about the development of their WAC are not available, the WAC are based on NRC and State of Utah requirements. The results of the analysis are shown in the bottom two boxes of Figure 1. The details of the methodology, results, and conclusions of the analysis that forms the basis for this close out report are contained in the report by Waters et al. 9 (referred to hereafter as the SNL report) and summarized here. The waste characterization data used in the analysis were obtained from the 1995 Mixed Waste Inventory Report (MWIR) database and augmented and modified during site reviews. While more detailed waste characterization data are expected to be available at the sites, the level of data contained in the MWIR database was expected to be sufficient for the analysis that forms the basis for this close out report. The characterization data contained in the MWIR database are based on untreated waste. Prior to disposal, these waste streams must be treated to remove or stabilize the hazardous constituents contained in the waste. This treatment and stabilization will change the concentrations of radionuclides remaining in the residual wastes. These post-treatment radionuclide concentrations are the ones that must be considered for waste disposal; therefore, estimates of the changes in concentrations due to treatment were made. The concentration in each waste stream after treatment for each radionuclide i, C Fi, was estimated using the following equation: C Fi 1 ρb = CIi AMR ρ final b initial 8

19 130,000 m 3 Results from RA 8 89,000 m 3 treated MLLW 9000 m 3 no treatment process 32,000 m 3 volume reduction & recategorization to LLW or MTRU 62,000 m 3 evaluated in RA 27,000 m 3 no radiological charaterization 6000 m 3 exceed PE limits 7 at Hanford 56,000 m 3 acceptable for disposal Results from SNL report m 3 exceed Hanford WAC 5900 m 3 meet Hanford WAC Figure 1. Disposition of waste volumes for treated MLLW. where C Ii is the initial concentration of radionuclide i (µci/m 3 ); AMR is the activity-per-unit-mass ratio (the ratio of the activity per unit mass before treatment to the activity per unit mass after treatment) (dimensionless); ρ b-initial is the initial bulk density of the waste (g/cm 3 ); and ρ b-final is the final bulk density of the treated waste (g/cm 3 ). 9

20 The preliminary estimates for ρ b-initial for the waste streams were based on the matrix parameter categories (MPC) associated with each waste stream in the MWIR database 12. The values for the AMR were based on work done at SRS 13. The sites reviewed and updated the estimates for all parameter values for each waste stream. Radionuclides with half-lives less than 5 years were not included in the analysis due to their limited effect on the long-term risks from disposal. The values that were assumed for C Ii were the mean concentration values for a particular waste stream given in the MWIR database or were based on a given range. The comparisons of radionuclide concentrations in the potentially problematic waste streams to the WAC at Hanford and Envirocare were made using the sum-of-fractions (SOF) method described in 10 CFR Part : SOF = i C i waste C i where C i-waste is the concentration of radionuclide i in the treated waste (µci/m 3 ); and C i is the concentration limit for radionuclide i in waste from the WAC (µci/m 3 ). Waste streams with SOF less than one were considered acceptable for disposal. Results of these calculations are presented in Figure 2 for Hanford and Figure 3 for Envirocare. At Hanford, all but 97 m 3 of waste were acceptable for disposal, most based on Category 3 disposal criteria. Of the 97 m 3, 79 m 3 are associated with one waste stream with a SOF of 2. With more refined analysis, this waste stream may be shown to be acceptable for disposal at Hanford. The remaining 18 m 3 of waste with SOF greater than 1 based on the Category 3 limits at Hanford represent a small inventory of waste streams and, when aggregated with other waste streams, may also be shown to be disposable at Hanford with more refined analysis. In addition to the Category 1 and 3 limits for disposal at Hanford, a separate set of trigger limits is contained in the WAC for mobile radionuclides in waste. These trigger limits are set so that Hanford personnel can review the waste streams more carefully in terms of total radionuclide inventory (i.e., radionuclide concentration times waste volume) the tracking method used for mobile radionuclides. Wastes with radionuclide concentrations exceeding these trigger limits were reviewed by Marc Wood (responsible PA engineer) at Hanford to provide an indication of their disposability. Due to the limited available data, a firm declaration of disposability could not be made. However, based on the available data and the small associated volume of waste, there appear to be no inventory limitation issues associated with disposal of these wastes at Hanford. Approximately 4600 m 3 of the 6400 m 3 of waste were not acceptable for disposal based on the WAC limits at Envirocare, illustrating that this site has relatively restrictive radionuclide limits. More refined analyses may indicate that some of these wastes streams would be acceptable for disposal at this site. 10

21 Volume of waste, m SOF < 1 based on Category 1 SOF < 1 based on Category 3 SOF > 1 based on Category 3 Figure 2. Classification of potentially problematic waste streams based on categories in the Hanford WAC Volume of waste, m ENV/Accept ENV/Not Accept Figure 3. Classification of potentially problematic waste streams based on the Envirocare WAC. A summary of the models typically used to estimate waste form performance and the available data used to calculate performance is contained in the SNL report Conclusions of the SNL Report Based on the results of the analyses summarized here and discussed more fully in the SNL report, the following conclusions and recommendations can be made: 11

22 Of the approximately 6400 m 3 of treated MLLW that were identified in the RA as potentially problematic for disposal at Hanford, all but 97 m 3 have a SOF of 1 or less based on WAC concentration limits for either Category 1 or Category 3 wastes at Hanford. Additional documented justification for disposal of the 97 m 3 may allow its disposal at Hanford, with possible additional measures. Disposal of this waste in concrete boxes (as is the current practice for waste that has a SOF of 1 or less based on Category 3 concentration limits) may be sufficient, thus removing the need for additional measures. The majority of the MLLW acceptable for disposal at Hanford has a SOF of 1 or less based on Category 3 concentration limits, indicating that additional intruder barriers will be required to dispose of this waste compared to Category 1 disposal. However, DOE Order A is currently being evaluated, and potential changes related to assessment of disposal facility performance may affect these results. Of the approximately 6400 m 3 of treated MLLW that were identified in the RA as potentially problematic for disposal at Hanford, approximately 4600 m 3 has a SOF of 1 or less based on the WAC for disposal at the Envirocare of Utah facility. This result illustrates that the WAC for the Envirocare facility are relatively restrictive compared to the radionuclide concentrations in DOE MLLW. The evaluation described in the SNL report analyzed only a portion of the MLLW for disposal. Approximately 8700 m 3 of MLLW were insufficiently characterized to allow the sites to determine a treatment process for these waste streams. Some of this volume are associated with MLLW streams that have not been generated. Other insufficiently characterized waste streams may require advanced treatment processes or special waste forms to be acceptable for disposal. In addition, approximately 27,000 m 3 of MLLW currently has insufficient radionuclide characterization and was not analyzed for disposability. The MLLW in both of these categories must be analyzed before a complete evaluation of MLLW disposability can be made. Compatibility of wastes and waste forms was not evaluated because this issue is a site responsibility. 4.2 Recommendations of the SNL Report The evaluation indicated that Hanford could dispose of much of the problematic MLLW as Category 3 wastes. However, the cost for disposal of Category 3 wastes is approximately three times higher than for Category 1 wastes at Hanford. A cost/benefit analysis may be warranted to determine if the use of different or additional treatment processes or different waste forms will result in Category 3 MLLW that can be disposed of as Category 1 wastes. An analysis of MLLW streams that do not currently have an assigned treatment process or radionuclide characterization data would be beneficial. 12

23 5. REVIEW, COMMENTS, AND CONCURRENCE 5.1 Internal DOE Review The analysis that forms the basis for this close out report showed that a majority of MLLW met the WAC for Hanford and/or Envirocare 9. This conclusion was reached without the performance of the waste form being taken into account. One of the original assumptions for the WFI was that a significant volume of MLLW would not meet the disposal limits of existing or planned facilities. The analysis for this close out report was conducted to narrow the focus of the WFI to those waste streams that exceeded the disposal limits of these facilities. Subsequent activities outlined in the WFI strategy were to be directed at these specific waste streams. However, the results clearly indicate that the conservative nature of the PA does not restrict a large volume of MLLW from disposal and that accounting for waste form performance is not necessary, based on the current and projected inventory. The conclusion drawn by the MWFA was to discontinue the WFI based on the results of the analysis associated with this close out report. Prior to close out, concurrence with this conclusion was solicited from the Site Technology Coordination Groups (STCGs) from 12 sites. A letter was prepared and site-specific data packages were compiled for STCG review and comment. The STCG letter and resulting comments are included in Appendix B. This review was conducted in July The STCGs were asked to review the analysis and provide comments on the following issues: (original letter with distribution attached) Based on your site knowledge and on the information contained in Attachments 1 and 2, indicate whether you concur with our conclusion that disposal of treated MLLW from your site is not a technical problem and the development of new waste forms is not required for your site. Some waste streams have not been evaluated for disposability because necessary data were lacking for them at the time of our analysis. These waste streams are listed in Attachment 3. If your site is listed in Attachment 3, indicate if data for any of the waste streams are now available and if you would like us to evaluate the disposability of these waste streams. For the waste streams that you would like us to analyze, please provide with your response the necessary data as listed in the column headings in Attachment 2. Attachment 4 is a list of waste streams that appear to have characteristics that may cause them to be incompatible with the selected waste forms. This determination was made by comparing the waste stream data in the mixed waste inventory report with the compatibility information contained in the MWIP (Mayberry et al. 14 ) report. Please review these waste streams and indicate if there are waste form compatibility issues that we can help you address. Based on this letter to the STCG requesting review, eleven of twelve sites responded with comments, questions, and new data. All relevant comments are addressed, and the new data are included in the final SNL report 9. While most comments indicated concurrence with the conclusions of the report, two sites (SRS and the DOE Chicago Operations Office) indicated partial disagreement with either the content of the report or the conclusions derived from it. However, review of the statements in the responses indicate that the wording of the STCG letter led to some misunderstanding of the report conclusions. To clarify these misunderstandings, both the comments and the responses to comments are summarized below. 13

24 Savannah River Site Two sets of responses were received from the SRS. One response was from the DOE Operations Office (DOE/SR) Solid Waste Division and the other was from Westinghouse Savannah River Company (WSRC) Solid Waste Division/R&D. Both sets of comments were consistent, and the latter comments provide more specific details of waste stream data. The most significant comments from the DOE Operations Office are addressed here. General Comment... SR does not concur with the conclusion that disposal of treated mixed low-level waste from SRS is not a technical problem. Response to General Comment The general comment was directed at a statement contained in the transmittal letter rather than any statement or conclusion contained in the SNL report. The comment is accurate in that there are technical problems associated with disposal of MLLW. The statement in the transmittal letter was broader than intended. However, the more specific statement that there appear to be no outstanding technical issues associated with the performance of existing waste forms is believed to be accurate. As stated in the SNL report, implicit in this assumption is that the wastes can be successfully processed into the waste form. (The issue of treatment and compatibility that all comments, including those from SR, have indicated does not appear to be a problem.) As discussed below in the response to comments from DOE Chicago, the primary limitation for radionuclide concentrations in disposed waste is derived from analysis of doses to inadvertent intruders. Waste forms generally play a small role in these hypothetical scenarios. Comment 1 Attachment 1, Page 3-1, section 3.1, Second paragraph SR does not understand the conclusion that most of the problematic waste streams (105) are acceptable for disposal based on the Hanford Category 3 limits when 83 waste streams contain mobile radionuclides whose concentrations exceed the reporting limits at Hanford. The report contradictorily states that more information regarding the performance of their waste forms would be required prior to determining the acceptability for disposal at that site. Comment 2 The Attachment 1 report concludes that most of the currently identified problematic waste streams can be disposed at Hanford. Has a check of the total radioactivity for the composite waste streams been compared against the Hanford acceptance limits? Response to Comments 1 and 2 The values listed for mobile radionuclides in the Hanford WAC are trigger limits rather than absolute limits. These limits are used to identify waste streams that require further scrutiny with regard to total inventory of mobile radionuclides. The waste streams exceeding these trigger limits were reviewed by Marc Wood at Hanford, who determined that they would likely be acceptable for disposal at Hanford. One of the conditions for acceptability for wastes that contain radionuclides that exceed the trigger limits is an evaluation to determine if a stabilized waste form would be required to reduce the mobility of the radionuclides (the trigger limits assume unstabilized LLW). Because the MLLW evaluated in this study 14

25 will be stabilized for the hazardous constituents, these wastes streams will likely be acceptable at Hanford with little additional analysis. In response to Comment 2,the mobile radionuclides are actually limited for disposal in terms of inventory, not concentration. The trigger limits are used to identify wastes that may have significant inventories of mobile radionuclides. The check of the mobile radionuclides provided by Marc Wood was an inventory check. Comment 5 These issues are clarified in the final SNL report. Of SRS s 49 MLLW streams only 19 have been evaluated resulting in the identification of 12 potentially problematic streams. Of these 12, the SNL report indicates only 3 as potential problems (>Category 3 at Hanford). However, SRS anticipates a total of 13 problematic mixed waste streams. Of these 13, 7 have yet to be evaluated and the remaining 6 are not consistent with the results of the national reports. Therefore, SRS does not concur with the conclusion that disposal of treated MLLW residuals do not present a technical problem. SRS will continue to evaluate disposal options of these waste forms. WSRC Comments 1 and 3 Waste streams SR-W004, SR-W005, SR-W029, SR-W037, SR-W038, and SR-W039 have been combined into one waste stream, SR-W040. This waste stream is acceptable for disposal at Envirocare. The following wastes streams have been identified by WSRC as potentially problematic : SR-W001, SR-W020, SR-W023, SR-W024, SR-W025*, SR-W033*, SR-W036, SR-W045, SR- W063, and SR-W072* (* indicates insufficient characterization). Response to DOE/SR Comment 5 and WSRC Comments 1 and 3 Some discrepancy in number of waste streams is noted in the comments from DOE/SR and WSRC. Because more detail was provided in the WSRC comments, these comments will be addressed. Based on this new information from WSRC, the six waste streams identified by WSRC as being aggregated into waste stream SR-W040 will be removed from the analysis in the SNL report. Waste streams considered potentially problematic by SRS are those that are problematic in terms of treatment and/or disposal. In the SNL report, the term potentially problematic indicates only potential problems in disposing of MLLW at Hanford. Waste stream SR-W001 was evaluated in the SNL report in Appendix B (waste streams with sum-of-fractions between 1 and 10 at Hanford) and shown to be acceptable for disposal at Hanford. This original ranking was accepted by Maurice Ades (author of the WSRC comments) during review of the RA report 8. Waste streams SR-W024, SR-W025, SR-W033, SR- W036, SR-W045, SR-W063, and SR-W072 were reported by SRS to contain only RCRA D-code (characteristic) hazardous waste. During review of the RA report, Maurice Ades of WSRC agreed that when treated, these wastes would be managed as LLW (the hazardous characteristic is removed). Therefore, they were not considered potentially problematic for disposal as MLLW although they may be problematic in terms of treatment or disposal of LLW. Additionally, comments provided by Maurice Ades during the review of the RA report indicated that streams SR-W020, SR-W023, SR-W024, SR- W063, SR-W072 currently had no assigned treatment process and should be removed from the analysis. 15

26 Because SRS indicates that waste forms are not an issue with any of their wastes, the ten waste streams identified as potentially problematic by WSRC have been noted but not analyzed in the SNL report. Comment 6 SRS has two waste streams (SR-W036 and SR-W045) for which identified treatment and final waste forms present a particular challenge. SR-W036 is tritiated oil with mercury. This waste stream contains extremely high activities of tritium which currently prohibits analysis of actual mercury content and organic destruction of the oil. In lack of other technologies, SRS has selected a preferred treatment option of radionuclide decay for 60 years followed by combustion and appropriate mercury treatment. This option is not particularly attractive given the long management time frame and unknowns associated with future treatment requirements and options. This option does not meet 10 year cleanup goals. An alternative treatment is needed that is applicable to tritium confinement and disposal requirements. Additionally, SR-W045 is liquid solvent waste (tri-butyl-phosphate and n-pariffin) characteristically hazardous for heavy metals and contaminated with tranuranic and other radionuclides. Organic destruction is required for this waste (benzene & trichloroethylene) but the selected incineration technology due to volume decrease potentially increases the residual radioactivity to levels presenting waste disposal problems. This results in a 30 year treatment rate for this waste stream. Again, this does not meet ten year cleanup goals and raises concerns associated with availability of current treatment capacity and future treatment and disposal requirements. An alternative treatment technology with a disposable final waste form appears to be needed. Response to Comment 6 These two waste streams are part of the ten potentially problematic waste streams identified by WSRC in the preceding comment. The problems associated with these two waste streams appear to be related to analysis and treatment, not waste forms. This is an area of concern recognized by the WFI but beyond its defined scope. From the brief description of the problems, there appear to be no waste formspecific solutions for these waste streams. The information provided by SR will be forwarded to others within the MWFA to help identify paths forward for these two problematic waste streams. DOE Chicago Operations Office General Comment The analysis of waste forms performance in the report is too incomplete to support the conclusion that additional waste form development is not required based on performance considerations. Current models of long-term performance require additional testing to determine rate-limiting factors, based on waste forms composition, radionuclide loading, and ambient conditions. The analysis in Chapter 4 utilizes an oversimplification of waste form by not differentiating factors that affect radionuclide release rates. Not all glasses or grouts will perform the same in a given environment. Factors that require further definition include waste loading, metal type and concentration, alteration products, colloid formation, retardation, and radiolytic effects. These factors can only be specified through additional long-term testing and refinement of performance models. Alternative waste form development should continue in order to provide better performing alternatives or waste forms that perform as well as those currently baselined. 16