HYDROCERAMIC WASTE FORMS: PROCEDURES AND PROPERTIES

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1 HYDROCERAMIC WASTE FORMS: PROCEDURES AND PROPERTIES Yun Bao 1), Michael W. Grutzeck 2) 1) Graduate Assistant, Materials Research Institute, The Pennsylvania State University, U.S.A. 2) Professor of Materials, Materials Research Institute, The Pennsylvania State University, U.S.A. ABSTRACT A hydroceramic waste form is designed specifically to solidify and isolate sodium bearing waste (SBW) in storage at various U.S. Department of Energy (DOE) sites. The acidic waste produced during reprocessing of fuel rods was over-neutralized with sodium hydroxide (NaOH) and stored in underground tanks at DOE s Hanford and Savannah River sites. Concentrations of NaOH in the SBW can range from 4 to 12 M. Additionally,some of the SBW is nearly pure NaOH whereas others can contain large amounts of sodium salts. A hydroceramic is a monolithic solid consisting of tectosilicates (zeolites, feldspathoids) that can be made from metakaolin and concentrated NaOH. The starting materials are mixed together forming a thick paste, precured at room temperature, and then cured at C under saturated steam pressure for a day or so. As a rule of thumb: if the SBW has a molar NO 3 +NO 2 /Na ratio 0.25, it can be mixed with metakaolin and solidified directly. If the ratio is greater than 0.25 the SBW must be pretreated to reduce the ratio so that, in effect, direct solidification can be carried out. Waste can be pretreated by thermal means (calcination, steam reforming) or by chemical means using metals such as Al and Si to reduce the NOx. Procedures and properties of three hydroceramic waste forms are described: one made by direct solidification of a low NOx SBW, one made from a calcined SBW, and one made from a chemically pretreated SBW. All hydroceramics have leachabilities that are equal to or better than DOE s reference E-glass. 1. INTRODUCTION A monolithic hydroceramic is a new nuclear waste form that has been developed to solidify liquid waste commonly called low activity or sodium bearing waste (SBW). 1-4 This waste is currently stored in underground tanks at the Department of Energy s (DOE s) Savannah River and Hanford sites. The DOE has been mandated to clean up this legacy waste. In order to do this they are required to produce a solid from the waste that is measurably strong and insoluble enough to qualify as a waste form suitable for storage either on site or off site at a national repository. Generally the DOE favors making a glass from the more easily vitrified insoluble precipitates (sludge) at the bottom of the tanks. 5 The remaining soluble fraction is what we call SBW consisting mainly of NaOH, NaNO 3 and NaNO 2 with much smaller

2 amounts of soluble carbonates, sulfates and a host of organic compounds. The difficulty of making a glass from a SBW is that many sodium silicates are soluble, which is not an entirely desirable property of a waste form. The problem can be resolved however by diluting the sodium content of the glass by adding a large amount of glass making (silicate) frit and produce, as an example, a borosilicate glass like Pyrex that contains 2.8 wt% Na. The concern here is that the cost of a glass log (the name of the solidified waste in a 10 foot high stainless steel canister) is approximately one million dollars. Waste loading will be minimal and the cost enormous. Therefore, alternates are always under consideration. Portland cement grout in one of many forms has been used and continues to be used to dispose of SBW. 6 Oak Ridge National Lab was among the first to promote Portland cement based waste forms that contained Indian River clay, some blast furnace slag and fly ash residue (from burning coal) to form zeolite-like phases. Savannah River has an ongoing program in which properly pretreated SBW (i.e. waste that has had its cesium and strontium removed) is solidified using a compositionally related Portland cement grout that they call Saltstone. The major problem with any Portland cement waste form, even ones proposed to be used to fill empty tanks at Savannah River or Hanford is the fact that they are calcium silicate based. The hydrates that form during setting are calcium silicate hydrates and smaller amounts of zeolitic phases. Zeolites are able to host sodium ions and cancrinite can host nitrate and possibly nitrite, but calcium silicate hydrate itself can host neither. 2 For this reason the majority of the salts in the waste are not hosted by one of the hydrates that form and thus remain part of the interstitial fluid that is highly leachable. Let us focus for a moment on zeolites. Zeolites are presently forming in the World s oceans, in saline lakes and other alkaline environments that have accumulated volcanic ash or fine silty clays (smectites). Natural zeolites are good scavengers for nuclear waste species. 7 Over the years we have developed this concept into one in which we are now able to use the SBW itself as one of the ingredients to make a zeolite-containing monolith without using any Portland cement at all. Taking a recipe for Saltstone and making it without Portland cement is a starting point for thinking about what we are doing. However, one must also remove all calcium containing ingredients such as blast furnace slag as well. This leaves the SBW and clay. We have found that the SBW can be reacted with a thermally treated clay (much more reactive) and, if the SBW is limited and the paste that forms is a very thick and extrudable the mixture will harden at ambient in a month (faster at 90 C) to form a strong low leachable solid. 4 We have been calling this solid a hydroceramic, because it is tan in color, vitreous in appearance and rings like a ceramic when hit with a steel rod. The phases that form in a hydroceramic during curing, mimic those that form in nature. They consist of tectosilicates, namely zeolites and feldspathoids. In both cases these phases are able to host sodium and a variety of anions in their structures. The zeolites we have formed generally are Zeolite A, Na- P1 and hydroxysodalite. The feldspathoids are generally cancrinite-like. Although Na is exchangeable, ions such as Cs and Sr are held preferentially. It has been demonstrated that the leachability of hydroceramics approach those of DOE s best glass waste forms at considerably lower cost. We are proposing that hydroceramics be used to solidify DOE s remaining SBW. One of the advantages of doing so vis à vis Saltstone for example is the ability of a hydroceramic to host 2

3 Cs and Sr. Because they are encapsulated in a zeolite they are not easy to leach. 7 This fact could help Savannah River and Hanford convince stakeholders that it is safe to dispose of their slightly higher activity wastes on site rather than shipping them offsite as high level waste. Finally, filling empty tanks with a pumpable hydroceramic (in this case a mixture of Class F fly ash and concentrated NaOH) will harden and form zeolites. The hydroceramic will support the overburden for millennia and as an added benefit the zeolites that form will (it is so presumed) interact favorable with in tank residuals. These residuals are possibly silica rich phases and traces of hardened sludge that could slowly dissolve and leak from the tank in the far future. If the zeolites were able to adsorb these ions and contain them and release sodium instead this would provide another protective mechanism not provided by Portland cement based tank fill. One can make hydroceramics in a number of ways more or less dictated by the composition of the SBW. The proposed reaction works best if the SBW consists entirely of concentrated NaOH solution (let us say 4-15 molar). The caustic dissolves some of the aluminum silicate (metakaolinite) and once in solution the anions begin to rearrange themselves around the solvated sodium ions. The structures that form have very short range order and are therefore not detectable by X-ray diffraction, but they are nevertheless tectosilicate precursors (NMR tells us so). Silicon and aluminum ions change their coordination from 3 and 6 to 4 and the newly formed tetrahedra link together. If one waits for a few weeks or a month the samples will begin to develop long range order and one will begin to see crystalline zeolites and feldspathoid peaks develop as long range order becomes more widely established. As man is loath to wait, the rate of reaction can be increased by raising the temperature to as high as 180 C (e.g. in a steam heated autoclave). For this work we have focused on 90 C because one could achieve this environment in a well insulated room with conventional by modified heating ventilation air conditioning (HVAC) systems. Furthermore mixing can be carried out using pug mills and the like which is available off the shelf because these same mixers are used to prepare clay based ceramics. Which brings us back one again the SBW composition. We have found that if the waste contains a small amount of NaNO 3 and NaNO 2 salts the process will work as well as if the waste were pure NaOH. The only difference being the fact that cancrinite phases form. This is important because cancrinite is able to host nitrate and possibly nitrite in its crystal structure. If however the waste contains an excess of these salts some will remain unreacted and the waste form will have a very large and unacceptable leach rate. We have found that the upper limit of salts in the waste is 25 mol% NO x calculated as the ratio of total moles [(NO - x /total moles Na + ) x 100]. SBW falling below this value can be solidified directly, in one step. 3 Generally speaking, much of the SBW in storage at Savanna River is of this type. It is suspected that the majority of this SBW is a by product of sludge washing operations and that some of this waste has been blended with higher salt containing waste or stored separately. SBW that has a higher salt content (typically the SBW stored at Hanford) must first be pretreated in some way to lower its NOx content into an acceptable range after which it can be incorporated into a monolithic hydroceramic. We can pretreat the waste in a number of ways. Thermally driven calcination with a reducing agent and calcination aid as well as a chemically driven pretreatment have been explored. 3

4 The paper describes procedures used to make and the properties of: 1) a hydroceramic made by direct solidification, 2) a hydroceramic made from a calcined SBW, and 3) a hydroceramic made from a chemically pretreated SBW. It is assumed that the organic component of the SBW, which can be significant in some cases, can be accommodated by the hydroceramic, but at this point in time we do not know the magnitude of or the potential loss of such organics from a given hydroceramic. Therefore, at this point in our research only thermal calcination can be guaranteed to treat all types of waste. Because it is a high temperature process organics are burnt off and thus become a non issue. Given this caveat, all hydroceramics described below have leachabilities that are equal to or better than DOE s reference E-glass and thus qualify as acceptable from a leaching standpoint. 2. EXPERIMENTAL 2.1.Materials Kaolin, (an impure kaolinite [Al 2 Si 2 O 5 (OH) 4 ] containing small amounts of quartz and mica from the Helmar-Bovil clay deposit mined in Helmer Idaho by Wentz Pottery a.k.a. Troy clay) 2 was purchased from Columbus Clay in Columbus OH. The as received clay mined by Wentz is preground to 50 mesh and is packaged in 50 pound bags. FTE Minerals in Bethlehem, PA processed one ton of the clay into metakaolin in a 0.9m OD x 9m long rotary kiln utilizing a materials residence time of 2 hours and a maximum temperature of C. During the process, periodic LOI measurements were taken to ensure the proper material was being made. The resultant product was milled in a micronizing mill to a size characterized as 95% passing 325 mesh. X-ray diffraction and SEM examination of the raw Troy clay suggest that the clay consists predominantly of kaolinite but contains traces of muscovite, quartz and perhaps halloysite. Metakaolin was selected to serve both as an aluminosilicate calcination aid (i.e. a sodium getter for the nacent Na ions that form during calcination thus preventing the formation of major amounts of Na 2 CO 3 ) and as a binder phase for granular calcines to be mixed with suitable NaOH solutions to produce a monolithic hydroceramic. Three nuclear waste simulants were used in the experiments: a Savannah River Tank 44 simulant (SRS) 3, a full Hanford Tank AN-107 simulant, and a simplified Hanford Tank AN-107 simulant 4,8. The compositions of the simulants are given in Tables 1 to 3, respectively. All were prepared from reagent grade chemicals. Table 1. The composition of Savannah River Simulant* Compound Concentration (g/l) CsNO KNO NaNO NaAlO NaOH * The total concentration of nitrate and nitrite anions is 1.0 mol/l. The total concentration of Na is 5.1 mol/l. The concentration of Cs is 0.5 mol/l. The NO x - /Na molar ratio is ~0.2. This waste needs no pretreatment. 4

5 Table 2. The composition of Hanford simulated SBW ** Compound Concentration (g/l) Compound Concentration (g/l) Al(NO 3 ) 3 9H 2 O PbO Ca(NO 3 ) 2 4H 2 O NaCl Na 2 Cr 2 O 7 2H 2 O NaF CsNO Na 2 HPO Fe(NO 3 ) 3 9H 2 O Na 2 SO KOH NaNO La 2 O NaNO NaOH Na 2 CO NiO ** The total concentration of nitrate and nitrite anions is 3.93 mol/l. The total concentration of Na is 8.2 mol/l. Molar ratio of NO - x /Na is 0.48 requiring pretreatment. The simulation does not contain organics because a previous calcination had shown that all organics were burnt off during calcination. Table 3. The composition of simplified Hanford SBW simulant*** Compounds Concentration (mol/l) Molecular Weight (g/mol) Concentration (g/l) NaNO NaNO NaOH *** The total concentration of nitrate and nitrite anions is 3.93 mol/l. The total concentration of Na is 8.2 mol/l. Molar ratio of NO - x /Na is 0.48 requiring pretreatment. 2.2 Procedures Direct solidification Varying amounts of the SRS simulant described in Table 1 were mixed with Troy metakaolin until they had a paste-like consistency. Then they were placed in small cube molds, precured at 40 C overnight, demolded and then cured in Parr vessels at 90 and 190 C for an additional 24 hours to form hydroceramics Thermal calcination followed by solidification with a hydroceramic binder Making a hydroceramic from a high NO x - SBW typical of that found at Hanford requires that the SBW first be pretreated in some fashion in order to reduce its nitrate/nitrite content. Thermal calcination and steam reforming are conventional methods of carrying this out. The procedure described here has two parts including pretreatment to form a calcine and then subsequent solidification to form a hydroceramic. Three liters of simulated Hanford SBW was prepared based on the recipe given in Table 2. A reducing agent (~334 g sucrose) was added to the 3L of Hanford simulant at a ratio of 38g sugar/mol NO x. Metakaolin calcination aid ( g) was added to the liquid at a mole ratio 5

6 of metakaolin/na in liquid waste = 0.7:1. The slurry that formed was dried at 90 C. The dried sample was calcined at 525 C for 10 hours forming a granular calcine. The calcine was then solidified using additional metakaolin and 4M NaOH solution. Hanford calcine was blended with additional metakaolin (480g and 320g, respectively) and then mixed with 720 ml of 4 M NaOH. This produced a thick but pourable slurry that was poured into a 10.2 cm (4 inch) cube mold. The sample was precured in the mold at 40 C in a 100% humidity chamber overnight. After demolding, the sample was cured at 90 C for 24 hrs in a sealed steel can to from a 4-inch hydroceramic waste form. The sample was evaluated by taking sub-samples from various surfaces, edges and interior. The sample was cut into 27 pieces. After sanding, each block essentially became a ~2.54 cm (~1 inch) cube. The 27 samples consisted of 1 middle piece, 8 corner pieces, 6 side middle pieces and 12 side pieces. The subsamples were labeled using a combination of 3 symbols: 123, abc and TML, as shown in Figure 1. Each cube was tested and the data were used to comment on the homogeneity of the larger sample. a b c T M L Fig. 1. The definition of the labeling scheme used to identify subsamples in the 4-inch cube sample Chemical calcination followed by solidification with a hydroceramic binder In as much as a thermally driven reduction is inherently dirty other ways of carrying out the denitration/denitration process were studied. One rather well established method is through the addition of aluminum powder to the solution. The reaction takes place at room temperature, but does in fact produce ammonia. This is an off gas that would have to be collected. Another disadvantage is the fact that one produces a large amount of soluble NaAlO 2 which complicates the hydroceramic making process. Rather than only adding metakaolin one would also have to add silica in order to meet typical Na/Al/Si stoichiometries of most zeolites. Therefore it was decided to add silicon metal along with the Al and produce a zeolite in solution during the reduction process. This had two additional advantages: Si tended to slow the reaction rate and also reduced the amount of NH 3 exiting the sample. Presumably more N 2 was being formed. The reduction reaction was performed by adding small amounts of Al and Si in four continuous steps. Totally, g Al and g Si were added to 50 ml of the simplified Hanford waste simulant (Table 3) resulting in a mole ratio of Al/NO 3 of 1.5, Si/NO 3 of 1.5, (Al+Si)/NO x of A cloudy solution containing a white precipitate was obtained after the addition. The solution and precipitate were shaken and then divided into several portions, which were mixed with different amounts of metakaolin resulting in pastes having total mole ratios of Na/Al/Si of 0.5:1:1, 1:0.8:0.8, 1:1:1, 1:1.2:1.2, 1:1.5:1.5. These were often too thick and when needed the samples were liquefied somewhat 6

7 by using just enough water to form a thick but pourable paste. The pastes were cured at 90 C in Parr bombs for 24 hrs to produce hydroceramics Characterization X-ray diffraction patterns were obtained on a Scintag Pad V X-ray diffractometer using Cu K α radiation. The scanning electron microscopy images were taken on a Hitachi S-3500N SEM. The compressive strength of the hydroceramics was tested on Tinius Φ Olsen Universal Testing Machine. A modified Product Consistency Test (PCT) leaching test was used to investigate the performance of the hydroceramic waste forms. The samples were ground to a powder in an agate mortar and sieved using piggy-backed sieves having 100 mesh (top) and 200 mesh (bottom) (openings micron sizes). One gram of unwashed sample was placed in 10 ml water in a sealed Teflon container (Parr bomb) held at 90 C for 1 and 7 days. The solutions were filtered (leachate) and their electrical conductivity was determined using a Quickcheck Model 118 conductivity meter (Orion), and their ph with a Ross combination ph electrode (Orion). 3. RESULTS AND DISSCUSSION 3.1 Direct solidification Mix proportions, crystalline phases observed in the hydroceramic, Na leachability as calculated using a 1 day unwashed sample PCT test, and a calculated value for the % Na leached versus total Na content of the hydroceramic formed from direct solidification are given in Tables 4 (90 C cured) and Table 5 (190 C cured). The experimental results shows that direct solidification performs well enough for SBW with NO x /Na < 25 mol%. Leach values are lower for the higher temperature cured samples but overall all leachabilities are equivalent to those expected for DOE s E Glass reference material. 9 Note that conductivity was used as a rapid screening test of PCT solutions. It was found and documented that Na was the dominant ion in solution and that its conductivity was related to an equivalent amount of NaOH dissolved in water 4 (i.e. similar to what is listed in standard conductivity versus concentration tables available in CRC s Handbook of Chemistry and Physics.) Table 4. Metakaolin mixed with different amounts of simulated SBW and cured at 90 C for 24 hrs. Sample Number #1 #2 #3 #4 #5 #6 Metakaolin 1 g 1 g 1 g 1 g 1 g 1 g SBW Simulant 0.5 ml 1.0 ml 1.5 ml 2.0 ml 3.0 ml 3.5 ml Conductivity (ms/cm) % total Na leached Mk: Metakaolin, A: Zeolite A, HS: Hydroxysodalite, -- not analyzed. The % total Na leached is a measure of how much of the Na in the sample actually leached out of the sample. 7

8 Table 5. Metakaolin mixed with different amounts of simulated SBW and cured at 190 C for 24 hrs. Sample Number #1 #2 #3 #4 #5 Metakaolin 1 g 1 g 1 g 1 g 1 g SBW Simulant 0.5 ml 1.0 ml 1.5 ml 2.0 ml 3.0 ml Conductivity (ms/cm) % total Na leached Mk: Metakaolin, Q:Quartz, HS:Hydroxysodalite, A:Zeolite A, -- not analyzed 3.2 Thermal calcination and monolithification The 10.2 cm cube (4-inch square) sample was prepared from a calcined Hanford-like simulant (Table 2), i.e. from a thermally treated SBW. The density of the prepared hydroceramic was 1.03 g/cm 3, which is close to that of the hydroceramic samples prepared in previous papers. 2-4 The cube sample was cut into 27 small sub-samples whose location is defined as a combination of 123, abc and TML to mark the locations. The compressive strength and 1-day PCT of the sub-samples were characterized and several samples were tested by 7-day PCT. The resulting data are listed in Table 6. The average compressive strength for the subsamples is 3.16 MPa, which is close to that of the monoliths prepared before 2-4 and thus hard enough for easy transportation. The average leachate conductivity for 1 day PCT is 2.61 (ms/cm). The conductivities from 7-day leach tests are slightly higher than those obtained from 1-day leach tests. The results show that the formed hydroceramic waste forms have very low leachability and high compressive strength. The scale-up experiment from gram sized bench sized samples to a 4-inch cube suggests that homogeneity is preserved in the larger sample and thus it seems that scale-up may be straight forward and relatively easy to do. In addition, the big sample is just cured in a sealed steel paint can, which further suggests that a much larger sized sample should be easy to prepare in a well insulated warm-room. It is also very easy in reality to realize this kind of experimental condition if one decides to use 55 gallons drums as a container. The method of the formation of the hydroceramic waste form is an easy and potentially safer and less costly way to dispose of SBW. 3.3 Chemical calcination and monolithification The denitrated waste appeared cloudy after the fourth addition of Al and Si metal to the Table 3 Hanford simulant. Concentrations of nitrate and nitrite were monitored throughout the metals addition process. It was observed that the nitrite was decomposed most easily, less so for the nitrate. Nevertheless, as of the final addition of the metals the NOx level was below 20% needed for direct solidification. The cloudiness was due to the in situ formation of large amounts of precipitate of NaAlSiO4 (zeolite-d) as the nitrate and nitrite compounds were reduced. The cloudy solution was then mixed with additional and different amounts of metakaolin and just enough water to make paste-like samples that were cured to form monoliths having total moles of Na/Al/Si as 1:0.5:0.5, 1:0.8:0.8, 1:1:1, 1:1.2:1.2 and 1:1.5:1.5. The monoliths were autoclaved at 90 C in Parr bombs for 24 hrs to form hydroceramic waste forms. A PCT 7 day leaching experiment was performed on these five solids and the results are listed in Table 7. The leaching data show that the hydroceramics made in this fashion 8

9 have low leachability, which means that the formation of hydroceramics is a good crystalline host for the different anions and cations remaining in the liquid waste. The hydroceramic has the lowest leaching value when Na/Al/Si=1:1:1. Table 6. The compressive strength and PCT conductivity of the small blocks 1aT 2aT 3aT 1aM 2aM 3aM 1aL 2aL 3aL Strength (MPa) PCT-1(mS/cm) PCT-7(mS/cm) bT 2bT 3bT 1bM 2bM 3bM 1bL 2bL 3bL Strength (MPa) PCT-1(mS/cm) PCT-7(mS/cm) cT 2cT 3cT 1cM 2cM 3cM 1cL 2cL 3cL Strength (MPa) PCT-1(mS/cm) PCT-7(mS/cm) Table 7. Hydroceramics prepared with different amounts of metakaolin* Sample ID #1 #2 #3 #4 #5 Mole metallical/no Mole metallic Si/NO Total mole Na/Al 1:0.5 1:0.8 1:1 1:1.2 1:1.5 PCT-7 (ms/cm) ph *Total mole ratio of Na/Al/Si is calculated after the addition of metakaolin. The formula for metakaolinite (Al 2 O 3.2SiO 2, MW=222.14) was used in the calculation. 4. CONCLUSIONS The given examples of a hydroceramic made by direct solidification, a hydroceramic made from a calcined SBW and a hydroceramic made from a chemically pretreated waste show that a hydroceramic waste form could well qualify as a successful candidate for the entire range of NO x containing SBW now in storage at DOE sites. Direct solidification and metallic denitration/denitrition pretreatment to form hydroceramics have the beauty of simplicity and high waste loading. However, the fate of the organics in SBW has not been investigated. The existence of organics in the hydroceramic could be a potential problem for direct solidification and metallic denitration/denitrtion to form hydroceramics. Some constituents cold leach out, but at this point in time the magnitude of the problem is unknown. It is noted that calcination pretreatment burns off all the organics, which is an important advantage of this method. Therefore, it is concluded that calcination or steaming reforming (a similar 9

10 process as calcination and now being studied by DOE) are the most efficient ways of denitrating/denitriting all SBWs. Both processes produce an insoluble, organic free tectosilicate containing granular powder that can be solidified with additional metakaolin and NaOH. It is also concluded that the existing calcines at INEEL could most likely also be solidified using a metakaolin and NaOH binder. Hydroceramics have rather interesting properties that are directly related to their zeolite content. Their ability to cation exchange and/or sequester guest cations in their structures is well known. This is the property we are exploiting when making a waste form (radioactive or otherwise). However adsorption and catalysis are zeolite s other properties that could be exploited for non radioactive waste purposes. One such application is the fabrication of multitasking building materials-smart building materials. Hydroceramic paneling would be able to adsorb/desorb water vapor as well as harmful air born pollutants and even viruses (if zeolites were Cu or Ag exchanged they could deactivate viruses). Hydroceramic filters could be used for aquaculture and possibly tertiary waste water treatment. Hydroceramics could well become a multifaceted green building material and aid in promoting health and reducing CO 2 emissions to the air from traditional Portland cement manufacturing. 5. REFERENCES 1. Siemer, D. D., Grutzeck, M. W. and Scheetz, B. E., Comparison of Materials for Making Hydroceramic Waste Forms, in Environmental Issue and Waste Management Technologies in the Ceramic and Nuclear Industries V, Edited by G.T. Chandler and X. Feng, American Ceramic Society, Westerville, 2000, Bao, Y., Kwan, S., Siemer, D. D. and Grutzeck, M. W., Binders for Radioactive Waste Forms made from Pretreated Calcined Sodium Bearing Waste, Journal of Materials Science, Vol. 39, 2004, pp Bao, Y. and Grutzeck, M. W., Solidification of Sodium Bearing Waste Using Hydroceramic and Portland Cement Binders, in Environmental Issue and Waste Management Technologies in the Ceramic and Nuclear Industries X, American Ceramic Society, Indianapolis, 2004, Bao, Y. and Grutzeck, M. W., Performance of Hydroceramic Waste Forms Made With Simulated Handford AN-107 Sodium Bearing Waste, Journal of the American Ceramic Society, (accepted). 5. Lutze, W., Ewing, R.C., Radioactive Waste Forms for the Future, Elsevier Science Publishing Company, New York, Roy, D.M., Gouda, G.R., High-Level Radioactive Waste Incorporation into Special Cements, Nuclear Technology, Vol. 40, 1978, A. Dyer, Applications of Natural Zeolites in the Treatment of Nuclear Wastes and Fall-out, in Environmental Mineralogy: Microbial interactions, anthropogenic influences, contaminated land and waste management, Edited by J.D. Cotter- Howells, L.S. Campbell, E. Valsami-Jones, M. Batchelder, London, 2000, C.M. Jantzen, Engineering Study of the Hanford Low Activity Waste (LAW) Steam Reforming Process (U), WSRC-TR , and SRT-RPP , July 12,

11 9. Krishnamurthy, N. Zeolitic hydroceramics for sodium bearing waste. Master of Science, The Pennsylvania State University,