An End State Methodology for Identifying Technology Needs for Environmental Management, with an Example from the Hanford Site Tanks (1999) / Chapter Skim
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3 Example of an End State Based Analysis of Technology Development Needs for the Hanford Tanks
3 Example of an End State Based Analysis of Technology Development Needs for the Hanford Tanks
Pages 29-52
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From page 29... ...
One, an in situ disposal scenario is defined to suggest a remediation approach that stabilizes tanks without waste retrieval. This scenario reflects the possibility that some of the tanks and their contents represent a relatively low risk and their contents might not require retrieval, or that budgets may alter the cost-risk-benefit balance to allow for retrieval of waste from only the higher-risk tanks.
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From page 30... ...
Large amounts of uranium metal were processed to recover plutonium to make nuclear weapons, and the chemical separations processes resulted in large volumes of radioactive wastes that were ultimately stored in tanks. From 1943 to 1989, the Hanford Site processed approximately 100,000 metric tons (~10,000 short tons)
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From page 31... ...
There are now four distinct types of material- liquid, saltcake, sludge, and slurry in most of the Hanford tanks (U.S. Department of Energy and Washington State Department of Ecology, 1996~.
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From page 32... ...
The volumes of the various waste types for single-shell and double-shell tanks are summarized in Table 2. The estimated amount of non-radioactive chemical components of the tank wastes and the estimated amount of radioactive constituents are found in the Hanford TWRS Final Environmental Impact Statement (U.S.
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From page 33... ...
END STATE ANALYSIS This chapter has, so far, provided the scope of the Hanford tanks example and background on the initial state of the waste. The next step in the end state based approach is to define possible end states for the waste products.
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From page 34... ...
Although many aspects of this might be viewed as incomplete and interim, the committee believes that sufficient information on the end states is available to plan and conduct a prudently contingent technology development program for the Hanford baseline flowsheet. For other site applications of the end state based process, it may be necessary for a group organized by the technology development program to specify the plausible range of end state characteristics without a substantial base of information such as that available on the Hanford tanks and the potential disposal and storage environment.
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From page 35... ...
The heterogeneous nature of the Hanford tank wastes could pose significant challenges to producing a waste form such as glass that consistently meets repository licensing requirements concerning composition and homogeneity. There are two interrelated primary documents containing criteria that have significant technology development implications, Title 40 of the Code of Federal Regulations (CFR)
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From page 36... ...
Tank Farm Closure After tank waste retrieval is completed, the committee assumed that the tanks and associated external contamination will not be physically removed. Consequently, it will be necessary to take actions to leave the tanic farms in a suitable Tong-term disposal condition.
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From page 37... ...
, end state criteria for tank closure could include the requirement of no further significant vadose zone contamination. Cross-Cutting Factors There are a number of factors, termed cross-cutting factors by the committee, that can affect all end states of Hanford tank waste remediation and most other remediation programs.
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From page 38... ...
. DEVELOPMENT OF FUNCTIONAL FLOWSlIEETS It is conceivable and likely desirable that not all the Hanford tanks and tank waste will be remediated using a single scenario.
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From page 39... ...
In the following section, the committee's reference and two alternative scenarios are identified and associated with the end states specified, based on the impacts of a range of plausible future events. In the case of the Hanford tanks a useful perspective and basis for specifying the committee's reference scenario and plausible alternative scenarios is the wide spectrum of tank waste remediation alternatives in the recent TWRS environmental impact statement (U.S.
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From page 40... ...
and in Table 3 as the ex situ intermediate separations alternative. It is one of the more costly alternatives evaluated in the environmental impact statement and it entails a moderate level of operational impacts, but it results in one of the lowest levels of long-term impacts.
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From page 41... ...
Example of an End State Based Analysis of Technology Development Needs _ OF _ ~ ~ a ~ E ~ .m ~ o ~ so in :m ~ (n IL o in ~ cn == 1 ~ ~ o ~ N (d · (n 8 U)
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From page 42... ...
The liquid stream proceeds to cesium separation and water recovery operations, and the solids to enhanced sludge washing. The liquids do not have to be totally separated from the solids at this step because subsequent solids processing (i.e., enhanced sludge washing)
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From page 43... ...
Some of the Hanford tanks contain chemical complexants that solubilize these ordinarily insoluble compounds to the extent that the resulting LAW will not meet the end state concentration goals shown in Table 4. This is particularly the case for the transuranics in at least three Hanford tanks containing organic chemicals such as ethylene diamine tetraacetic acid (EDTA)
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From page 44... ...
For the purposes of the committee's reference scenario, an appropriate basis for planning and conducting a technology development program is to assume that the JAW disposal site will require a means to fill any void spaces in the waste emplacement horizon, a multicomponent cap designed to last for centuries, barriers to intruder access, monitoring wells, and occasional surveillance to detect and limit any intrusion. Enhanced Sludge Washing.
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From page 45... ...
In this operation the solids are separated from most of the liquid used for enhanced sludge washing operations. The techniques and considerations involved in this are essentially the same as those described above for solid-liquid separation following the Initial solids washing operation, and they are not repeated here.
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From page 46... ...
Tank Farm Closure. This operation is essentially the sane as the closure of the on-site, near-surface LAW disposal site discussed above, although additional characterization of the tank contents and adjacent contaminated soil before and after stabilization is likely to be required.
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From page 47... ...
In Situ Disposal Scenario It is the view of the committee that in situ disposal (i.e., tank waste left in place) constitutes another plausible scenario for planning and conducting a technology development program.
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From page 48... ...
The tank farm is then capped as discussed earlier in this chapter under "Tank Farm Closure." At present it is not clear that permanent barriers can be established that will not require some long-term institutional control and maintenance over some of the more highly contaminated areas, including residual waste in remediated tanks and tank farms. Extensive Separations Scenario It is the opinion of the committee that an extensive separations scenario is another plausible alternative scenario for planning and conducting a technology development program for Hanford Site tandc remediation.
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From page 49... ...
that significantly increase glass volume. In either case, there would be a need for more information on the contents of the tank wastes that will be treated using the extensive separations scenario, which has implications for characterization technology development requirements.
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From page 50... ...
<0.8 <0.04 <0.3 < 1 14c 90Sr 99Tc 137cs 1291 Transuranic elements < 0.008 < 10 nCi/g ~SOURCE: Based on Class A low-level waste radionuclide concentrations as found in U.S.Nuclear Regulatory Commission (1982a) ; 10 CFR 61.55, Table 1; and 10 CFR 61.55(a)
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From page 51... ...
Specifically, by being able to immobilize tank waste in situ, install subsurface barriers, perform enhanced cesium recovery, dissolve residual sludge, and separate strontium, technetium, and transuranic elements In addition to the committee's reference scenario functions, it would be possible to remediate tanks and tank waste under a wide range of end state requirements. This provides a contingency in case less extensive technologies can or must be used, as well as more extensive separations technologies in case of HEW disposal cost considerations.
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From page 52... ...
Finally, the committee notes that, in some cases, critical TWRS program policy or requirements specification documents, which might provide the basis for the end state based approach, remain under review or in draft form for long periods of time. In many instances the Hanford program direction has changed before an applicable report could be completed, implying that major decisions and changes in program direction are sometimes undertaken by decision makers without the benefit of all pertinent information.
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