Connie A. Cicero, Robert A. Pierce and Dennis F. Bickford
Westinghouse Savannah River Company
Aiken, SC 29808

Available for a processing fee to U.S. Department of Energy and its contractors, in paper, from:
U.S. Department of Energy, Office of Scientific and Technical Information, P.O. Box 62, Oak Ridge, TN 37831-0062,  
phone: (865 ) 576-8401,  
fax: (865) 576-5728,  
email:  reports@adonis.osti.gov

Keywords: Organics, Low Level Mixed Wastes, Vitrification, Resin

Numerous Department of Energy (DOE) facilities, as well as commercial facilities, use ion exchange resins for aqueous purification. Although these resins efficiently remove unwanted materials, they unfortunately create another waste stream that can be both very high in both organic and radioactive constituents. Disposal of the spent resins is often an economic problem because of the large volumes of resin produced and the instability of the resin.

In the past, several attempts were made to vitrify untreated ion exchange resin, but only limited success was obtained from a waste loading and volume reduction standpoint. Alternative glass formulations were used in this study to vitrify the untreated resin, but once again only limited loadings were possible without adverse chemical shifts (redox reduction reactions).

To try to increase the waste loading and volume reduction obtainable, a nitric-phosphoric acid oxidation process was used to pre-treat the ion exchange resin. Vitrification of the resulting solution from the oxidation pre-treatment was possible and greatly increased the waste loadings attainable. In these experiments, it was determined that a homogeneous glass could be made containing 57 wt% of the oxidation solution or ~74 grams of solution/100 grams of glass produced when melted at 1150°C. This waste loading was obtainable with both clean and spent ion exchange resin, where 120 ml of resin were dissolved in 100 ml of solution. The overall volume reduction of the two-stage process was two fold. The additives used were 25 wt% Fe₂O₃, 15 wt% Na₂HPO₄•7H₂O, and 3 wt% BaCl₂•2H₂O. Practical limitations will result from the resins' content of non-radioactive inorganic species and from the radiation field generated from the radioactive content.

The demonstrated two-stage stabilization process minimizes volatility and maximizes the waste loading possible in low temperature/low volatility compact melters.

The DOE has chartered the Mixed Waste Focus Area (MWFA) to investigate waste forms for Low-Level Mixed Wastes (LLMW). As part of the MWFA's attempt to develop alternative treatment methods for LLMW, the Savannah River Technology Center (SRTC) was funded to study vitrification of high organic wastes. Vitrification is a feasible treatment method for organics because organics are destroyed either by pyrolysis or combustion at typical vitrification temperatures with some of the heavier organic compounds being pyrolyzed within the melt. The majority of the combustion usually occurs above the melt in the plenum or in a secondary combustion chamber.

SRTC uses bench-scale (crucible-scale) vitrification studies on surrogate wastes to determine optimum processing parameters and glass additives. These results can then be used to study bench-scale treatment of the actual wastes or to perform pilot-scale studies with either surrogate or actual LLMW.

The Savannah River Site (SRS) has been operating since the early 1950's. During this operation, extremely large quantities of High-Level Waste (HLW), LLMW, Low-Level Waste (LLW), Trans-Uranic Waste (TRU), and hazardous wastes have been accumulated. Some, if not all, of these waste categories contain some amount of organic material. Spent ion exchange resin from aqueous treatment operations is an example of a stream that can be common to all categories because it is used in many different applications and is usually organic. Ion exchange resins are used in several processes at the SRS to remove both hazardous and radioactive constituents from solutions or sludges. Due to the large volume of spent resin that exists within the DOE complex and in the private industry, SRTC decided to pursue vitrification of spent ion exchange resin.

A large user of these resins is the Reactor facilities. In the Reactor facilities, ion exchange resins are used for purification of water in the reactor basins where fuel rods are stored. The Receiving Basin for Offsite Fuel (RBOF) at SRS also uses resins to purify the water in its storage basins. This particular type of treatment using resin is also found in the private sector for operation of nuclear power plants, since they have basins where fuel rods are stored.

For these studies, resins typical of those used in the reactor basins at SRS were obtained, as well as a sample of spent resin from the basin deionizer. These resins were used to determine the viability of using vitrification to stabilize the wastes.

The clean resins obtained for this study included a sample of both the cation and anion resins used in the Reactor facilities. When used in the deionizers, they are mixed in a ratio of one part cation resin to one and a half parts anion resin. The cation resin is a sulfonated divinylbenzene/styrene copolymer in the hydrogen form (Amberlite IR-120), while the anion resin is a quaternary amine divinylbenzene/styrene copolymer in the hydroxide ion form (Amberlite IRA-400). Both were originally purchased from Rohm and Haas. A partial characterization of the resins was performed to determine the species present, as well as the total organic content. The results of the characterization are shown in Table 1, where "N/A" is non-applicable and "ND" is none detected.

Table 1 - Clean Resin Characterization

Species	Cation	Anion
Inorganic Carbon	<50 µg/g	604 µg/g
Organic Carbon	249000 µg/g	274000 µg/g
Aluminum	0.010 wt%	N/A
Boron	0.008 wt%	N/A
Calcium	0.061 wt%	N/A
Iron	0.002 wt%	N/A
Lithium	0.001 wt%	N/A
Sodium	0.010 wt%	N/A
Phosphorous	0.043 wt%	N/A
Silicon	0.047 wt%	N/A
Zinc	0.019 wt%	N/A
Zirconium	0.031 wt%	N/A
Fluoride	42.9 µg/mL	ND
Chloride	ND	5.06 µg/mL
Sulfate	226 µg/mL	380 µg/mL
Nitrate	0.935 µg/mL	9.46 µg/mL
Nitrite	ND	<1 µg/mL
Phosphate	ND	ND
Water Content	47.5%	61.5%

Based on past processing knowledge of the ion exchange resins in the reactor basins, it was assumed that the contaminants shown in Table 2 were removed from the water. The typical range of radioactivity is also shown in Table 2.

Previous vitrification studies with organic ion exchange resins had been performed at the SRTC.¹ These studies were performed with a resorcinol based organic ion exchange resin, which was proposed for use in removing the Cs from HLW supernate. SRTC proposed that the spent resin would be fed with the HLW sludge and glass frit to the Defense Waste Processing Facility (DWPF) melter.

Table 2 - Typical Resin Contaminants

Contaminant	Amount
Na	27 ppm
Ca	8 ppm
K	5 ppm
Si	1 ppm
NO3-	10 ppm
SO4--	17 ppm
Cl-	6 ppm
Cs-137	180 - 280 dpm/ml
Sr-90	50 - 95 dpm/ml
Tritium	0.054 - 0.31 µCi/ml

Preliminary crucible studies at SRTC indicated that the maximum amount of resin that could be incorporated in the glass matrix was 5 grams of resin/100 grams of glass produced. This loading was mainly bounded by the redox (Fe2+/S Fe) of the glass, since the presence of organics tends to cause more reduced glasses. The other significant finding of the crucible studies was that the presence of nitrates helped lower the redox ratio, permitting greater amounts of organic to be treated per gram of glass produced.

Crucible study results were used to determine the resin loading for larger scale studies in a reduced scale DWPF melter. Results from the larger scale study were consistent with the crucible findings and also found that the glass had slightly poorer durability with the resin present, which was expected because of the higher redox. However, the durability was still magnitudes better than the Environmental Assessment (EA) glass durability results for HLW.²

Additional studies with the resorcinol resin were performed at the DOE/ Industrial Center for Vitrification Research (Center). Both crucible and pilot-scale vitrification studies were performed. The crucible- scale studies determined the resin loading obtainable, while the pilot-scale studies were used to determine the viability of processing resin with HLW feed in the Stir-Melter^® stirred melter. In the crucible-scale studies, the theoretical resin loading limit was determined to be 4.91 grams of resin/100 grams of glass produced. Equations were also developed to perform theoretical limit calculation under varying process conditions.

For the pilot-scale studies, Cs-loaded resorcinol resin was blended with the feed to the melter. The feed used in the experiments was the same feed that was used for the first cold chemical campaign in the DWPF. This feed differed from the feed used in the SRTC melter studies because it also contained the precipitate hydrolysis aqueous (PHA) simulant from supernate processing without resin. Although the feed composition was not completely representative of the expected feed composition, if resin pre-treatment of the supernate was used, it was felt that the small amount of PHA present would not affect the resin vitrification results. The data provided a strong indication that vitrification of the resin in the DWPF type feed was plausible. In these studies, resin loadings were comparable to the crucible-scale results and melter operating conditions were not greatly affected.²

Based on the results provided by previous research with resin vitrification, attempts were made to vitrify the reactor ion exchange resin in a CaO-Fe₂O₃-SiO₂ glass system. This system was used since the iron component could provide an accurate indicator of the redox of the glass, and the ternary system was being well characterized for homogeneity and durability by research at the Center.³ Ferric oxide also can serve as a redox buffer by being reduced prior to other glass forming elements and thus provides oxygen for oxidation reactions.

Six glass compositions were selected from the ternary studies based on tested durability and predicted glass processing properties. Two of the compositions were used exactly as formulated, while the other four were combined to make two different new compositions, where the new compositions had better processing parameters. The base compositions were fabricated from reagent grade chemicals with Fe(NO3)₃ used as the glass additive for the Fe₂O₃ component to help lower the redox. Various resin loadings were then added to the batch materials.

The water and anion species content of the cation/anion coupled reactor resin was very high. When calcined at 600°C, only 3.08% material remained. Theoretically, this should correlate with the ability to achieve high waste loadings in the glass matrix because most of the material would be pyrolyzed or combusted during vitrification. On account of this, the first glass compositions tested used very high waste loadings, but the organics apparently hindered glass formation. Successive tests halved the amounts of resin until an acceptable resin loading was found. The compositions tested are listed in Table 3. Table 3 also shows the composition of batch 13, which was the same composition used in batch 1 but pre-calcined resin was added instead of the untreated resin.

Table 3 - CaO-Fe₂O₃-SiO₂ Batch Compositions Tested

Batch ID	Al2O3 Wt%	B2O3 Wt%	CaO Wt%	Fe2O3 Wt%	Na2O Wt%	SiO2 Wt%	g Resin/ g Glass
1	0.0	9.4	8.4	4.8	18.6	48.6	1.623
2	14.6	3.7	16.3	4.6	17.9	33.3	1.623
3	0.0	9.4	8.4	4.8	18.6	48.6	0.812
4	0.0	9.4	8.4	4.8	18.6	48.6	0.406
5	0.0	9.4	8.4	4.8	18.6	48.6	0.195
6	0.0	9.4	8.4	4.8	18.6	48.6	0.097
7	14.6	3.7	16.3	4.6	17.9	33.3	0.203
8	14.6	3.7	16.3	4.6	17.9	33.3	0.101
9	0.0	0.0	6.7	20.0	14.7	49.0	0.203
10	0.0	0.0	6.7	20.0	14.7	49.0	0.101
11	0.0	8.2	13.3	19.9	7.3	41.1	0.203
12	0.0	8.2	13.3	19.9	7.3	41.1	0.101
13	0.0	9.4	8.4	4.8	18.6	48.6	1.429

All glasses were melted in covered high purity (99.8%) alumina crucibles at 1050°C because of the desire to use the Stir-Melter^® for processing the resin. The Stir-Melter^® is limited to operating temperatures of 1050°C because of the Inconel components.

The first few batches melted with high resin loadings did not produce glass. It was not until the resin loading was decreased to around 0.2 g resin/g glass (20 wt%) that the final product resembled a homogeneous glass. Once the glasses were cooled, they were broken out of the crucibles to determine the physical appearance, the PCT durability, and the Fe²⁺/Fe³⁺ ratio. The physical appearance of the batches that made glass are given in Table 4. For the remaining batches, including 13 with the pre-calcined resin, the organic content was too high to allow incorporation into the glass matrix so they were not included in further analyses.

Table 4 – Appearance of CaO-Fe₂O₃-SiO₂ Glasses

Glass ID	Description
5	Brown Glass
6	Brown Glass
7	Black glass with small porous salt layer over edge
8	Black glass with salt layer on top
9	Glass with transparent salt layer
10	Brown Glass
11	Brown glass with small salt layer
12	Brown glass with small amount of salt layer

As shown in Table 4, some of the glasses appeared to have a salt layer form on the glass surface. This salt layer was examined using Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS). Only one sample of each composition was inspected, since the salts should have been the same for the same glass compositions with only the amount varying. Results for the different salts are shown in Table 5.

Table 5 - Salt Chemical Components

Glass ID	Description
5	No layer, but Na2SO4 and CaSO4 in glass
8	Na2SO4
9	Na2SO4
11	Nothing in layer, but some S in glass

The PCT was performed on all eight of the batches that produced glass. The salt layers were not included with the glass if it could be easily removed from the glass surface. The PCT is a crushed glass leach test that measures the releases of B, Si, Na, and other elements in 90°C ASTM Type I water over a period of seven days.⁴ Glass from each crucible was run in triplicate for the PCT and the results were averaged. The PCT results in ppm are given in Table 6. The measured leachate pH is also listed in Table 6, since this provides a secondary indication of glass durability.

Table 6 - PCT Results for CaO-Fe₂O₃-SiO₂ Glasses in PPM

Glass ID	B	Si	Na	pH
5	45.95	115.82	309.14	11.27
6	66.50	48.12	332.92	11.17
7	14.66	37.13	240.92	11.61
8	47.13	53.32	589.86	11.79
9	0.74	325.60	1630.30	12.37
10	0.22	378.24	1755.50	12.44
11	15.37	15.91	47.49	10.02
12	10.38	20.69	38.24	10.07

No apparent trend was observed between the amount of resin in the glass and the PCT release. However, it appeared glasses 9 and 10 had relatively poor durability based on the high Na released and the high measured pH.

The Fe²⁺/Fe³⁺ ratio was determined since the redox is a very important factor for glass processing. High ratios are not desirable in glass melters due to the potential to reduce elemental or metal oxides to pure metals or sulfides, which can decrease the efficiency of joule heated melters. Theoretically, the ratio should be higher for the glasses with higher resin loading because of the higher organic content. The Fe²⁺/Fe³⁺ ratio for the eight glasses are given in Table 7. The salt component data is also included in the table so the effect of the redox ratio on the formation of salt layers could be assessed.

Table 7 - Fe²⁺/Fe³⁺ Ratio for CaO-Fe₂O₃-SiO₂ Glasses

Glass ID	Fe2+/Fe3+ Ratio	Salt Component
5	1.21	No salt layer
6	0.486	N/A
7	2.49	Likely Na2SO4
8	1.56	Na2SO4
9	0.036	Na2SO4
10	0.034	ND
11	0.049	Some S in glass detected
12	0.033	Likely S in glass

As can be seen from the results, some of the glasses were very reduced, and in all cases the higher resin loading glasses had higher ratios. A comparison of the redox ratios to the salt components seems to indicate that the salt layers were more likely to form at the higher redox ratios.

Based on the salt layer analyses, PCT results, and Fe²⁺/Fe³⁺ ratios, only glasses 5, 6, 11, and 12 were considered acceptable for further analyses. These glasses were examined for total constituent analysis using Inductively Coupled Plasma-Emission Spectroscopy (ICPES). Since glasses 5 and 6 were the same batch composition and only differed in the resin loading, only one of the glasses was chemically characterized. Results for glasses 11 and 12 indicated that the glass compositions were very similar when the same batch compositions were used. Results are presented in Table 8.

Table 8 - Chemical Compositions Results for CaO-Fe₂O₃-SiO₂ Glasses

Oxide	#6	#11	#12
Al2O3	3.285	2.679	2.186
B2O3	10.579	9.235	8.991
CaO	9.145	13.841	13.893
Fe2O3	4.962	18.707	18.375
MgO	0.008	0.007	0.008
Na2O	20.515	10.253	10.437
SiO2	49.001	39.882	43.323
Total	97.496	94.603	96.213

Once the chemical composition results were received, the PCT results were normalized. Since no acceptance criteria have been established for LLMW, the durabilities of the glasses produced were compared against the HLW criteria which states that the glass produced must be more durable than the EA glass.⁵ The normalized PCT results and the EA glass values are contained in Table 9. The chemical composition for glass 6 was used for normalizing the results for glass 5.

Table 9 - Normalized PCT Results (g/L) for CaO-Fe₂O₃-SiO₂ Glasses

Glass ID	B	Si	Na	pH
5	1.574	0.510	2.240	11.27
6	2.024	0.210	2.188	11.17
11	0.536	0.085	0.624	10.02
12	0.372	0.105	0.494	10.07
EA	16.695	3.922	13.346	11.91

As can be seen from the results given in Table 9, the normalized releases for B, Si, and Na for the four glasses were substantially less than the EA glass. Once again, no apparent trend was observed between the resin loading and the PCT release.

X-ray Diffraction (XRD) analyses were also performed to determine if any crystals were present. The XRD results are contained in Table 10. Quantitative XRD results were not available.

Table 10 - XRD Results for
CaO-Fe₂O₃-SiO₂ Glasses

Glass ID	Phase Detected
6	Unidentified*
11	SiO2-Quartz
12	Quartz

Based on all of the analytical results, glass #11, which contained 8.2 wt% B₂O₃, 13.3 wt% CaO, 19.9 wt% Fe₂O₃, 7.3 wt% Na₂O, and 41.1 wt% SiO₂ with a 20 wt% resin loading produced the most viable candidate for vitrification demonstrations. The reasons for this choice included a higher waste volume content than #12, predicted viscosity within the processing region of most melters, very low PCT releases, and a redox ratio which provided more oxidizing than reducing conditions. However, this glass did contain some unreacted quartz when examined with XRD, but it probably would have been incorporated into the glass matrix if higher melting temperatures had been used. This glass wasteform represents a two fold volume increase based on treatment of the dry and clean resin. However, when the resin is actually used for treatment, the resin waste will be in an aqueous form with materials captured on the resin so there will be a greater mass of waste. Therefore, the volume reduction potential of vitrification should be greater for spent resin because the same mass of resin could be treated but the actual weight of the waste would increase.

Due to the relatively low weight percentage of resin that was incorporated in the CaO-Fe₂O₃-SiO₂ glasses, it was decided that pre-treatment of the resin might be necessary. A relatively new oxidation process developed by SRTC for oxidizing organic wastes was considered. This process uses a nitric-phosphoric acid solution to completely destroy the organic content of the waste leaving a waste residue in the solution.

In the process, dilute nitric acid is intermixed with concentrated phosphoric acid. Phosphoric acid is used since it allows oxidation temperatures up to 200°C, and it is relatively non-corrosive towards 304-L stainless steel at room temperature. This solution completely oxidizes organic materials to CO₂, CO, and inorganic acids and is usually complete within a few hours for most organic materials, including resins and plastics.⁶

Previous efforts were made by R.A. Pierce of SRTC to oxidize resin using the nitric-phosphoric acid pre-treatment process and had proven successful, so oxidation of a sample of the clean cation/anion resin was attempted. Several pre-trials were performed to optimize the temperature and pressure processing conditions and to minimize foam development. It was confirmed that temperature was the critical factor for controlling foaming. Good oxidation rates of the resin were attained at around 190°C and 5 - 10 psig. Using these conditions, the resin dissolved in about 20 minutes, and 70 - 80% of the resin was oxidized to CO₂ and H₂O in the first 30 minutes. Higher oxidation rates may have been obtained at both higher temperatures and pressures, but it was not felt that this was necessary.

Initial attempts were made to separate the phosphoric acid out of the resulting solution, but were not successful. In order to overcome this problem and to optimize the amount of resin that could be loaded in glass, it was decided to test an iron-phosphate glass composition which had been used in making Pu bearing glasses. The composition was tested with pure phosphoric acid before using the actual resin solution to ensure that glass could be made.

The first composition tested used only Fe₂O₃ and Na₂O additives (batch 14). When melted at 1150°C, this composition did not appear to be glass but was more of a crystalline solid. After further evaluation of Pu glass compositions, it was decided that the presence of BaO strongly influenced glass formation and that too much iron had been added in the first batch. To test the new composition, two different batches were made. Batch 15 contained BaO, while batch 16 did not and substituted Na2O for the BaO. Both were melted at 1150°C for 4 hours and removed from the furnace. Only batch 15 produced glass, while batch 16 appeared to be a crystalline solid. The compositions tested using pure phosphoric acid are shown in Table 11 on a weight percent additive basis.

Table 11 - Phosphoric Acid Batch Compositions (Wt%)

Additive	#14	#15	#16
H3PO4	52.46	56.58	49.69
BaO	0.00	3.26	0.00
Fe2O3	30.85	24.67	23.57
Na2HPO4•7H2O	16.68	15.50	26.74

Once the proper batch composition was determined, the oxidized clean resin sample was mixed with the appropriate glass additives and vitrified at 1150°C for 4 hours. This batch was the same composition as batch 15, except the phosphoric-nitric oxidation solution was used rather than pure phosphoric acid, and was called batch 17. A homogeneous black glass was produced with a very low viscosity. To determine whether the resin residue had an effect on the glass composition and durability, characterization of compositions 15 and 17 was performed.

The chemical compositions of glasses 15 and 17 (with and without resin residue, respectively) are contained in Table 12. Both glasses were very similar in composition, with the resin glass having slightly greater Al₂O₃ content and slightly lower Fe₂O₃ content. The small differences shown can be attributed to the cations contained in the resin and the slight digestion of the vessel walls by the oxidation solution. Both compositions were also very close to the expected oxide compositions based on the additives used in batching.

Table 12 - Chemical Composition Results for
Clean Resin Iron-Phosphate Glasses

Oxide	#15	#17
Al2O3	0.937	1.931
B2O3	0.013	0.025
BaO	2.899	2.780
CaO	0.207	0.235
Cr2O3	0.165	0.098
Fe2O3	35.407	33.947
La2O3	0.005	0.005
Na2O	5.080	4.947
Nd2O3	0.020	0.032
NiO	0.074	0.025
P2O5	59.649	59.834
PbO	0.023	0.026
SiO2	0.013	0.030
SrO	0.002	0.002
Total	104.446	103.854

The PCT⁵ was performed to determine the durability of the glass products. The results were normalized for the glass constituents and compared. A direct comparison could not be made with the PCT acceptance criteria because this criteria has only been established for HLW glasses, which are borosilicate based glasses. Therefore, the main effect studied was that of the resin on the durability. The normalized PCT releases for the primary glass constituents of the two glasses tested are contained in Table 13.

Table 13 - Normalized PCT Results (g/L) for
Iron-Phosphate Clean Resin Glasses

Glass ID	P	Ba	Na	Fe	pH
15	0.022	0.002	0.088	0.001	5.66
17	0.022	0.001	0.087	0.001	6.03

The normalized releases for the two glasses were very low and durability did not seem to be affected by the presence of the resin residue. Although no criteria are established for iron-phosphates glasses, the Na release is at least 100 times lower than the criteria for HLW.

XRD analyses of the resin residue glass (#17) was performed to determine if any crystalline species were present. It was determined that glass 17 was amorphous.

Theoretically, most of the organics in the resin should have been destroyed by the oxidation process. In order to determine if any organic material remained in the oxidation solution, the Fe²⁺/Fe³⁺ ratio was determined using colorimetric analysis. The Fe²⁺/Fe³⁺ ratio for the resin loaded glass (#17) was 0.301, while the ratio for the non-resin loaded glass (#15) was 0.443. Both of these are a little higher than limits established at SRTC for joule heated melters. However, the fact that the resin loaded glass had a lower ratio was a good indication that most of the organics in the solution had been destroyed.

Attempts were also made to use Na₂CO₃ as the glass forming additive instead of the Na₂HPO₄•7H₂O. Na₂CO₃ is a common glass additive for many LLMW and if used additional oxidation solution could be added because of the absence of phosphate from the sodium glass additive. When this batch was mixed, intense foaming occurred. As the sample was dried, the batch foamed over the sides of the crucible. Attempts were made to replace all of the batch contents in the crucible and the crucible was melted at 1150°C for 4 hours. The resulting product was not glass and appeared to be very crystalline. It was decided that Na₂CO₃ should not be used because of the foaming problem that occurred.

After it was determined that resin could successfully be oxidized and vitrified in an iron-phosphate glass matrix, a sample of spent resin was obtained from the Reactor facilities at SRS. This resin was used in cleaning basin water for the Reactors.

The resin was pre-treated using the nitric-phosphoric acid oxidation process. Approximately 120 mL of resin were dissolved in 100 ml of acid solution. Analyses of the resin solution indicated that it contained the species shown in Table 14.

The resulting oxidation solution was mixed with the same additives as mixed with glass 17 and heated to 1150°C at approximately 10°C/min and melted at 1150°C for 4 hours. The resulting product (batch 18) seemed glass-like in the center but was crystalline around the edges. Upon scrutiny of the batch sheet for #18, it was determined that BaCl₂•2H₂O had actually been used instead of BaCl₂. This resulted in not enough Ba being added to the batch composition and thus the desired batch composition was not melted. Another batch (#19) was made using the correct amount of BaCl₂•2H₂O and was melted at the same rate and for the same duration as batch 18. This composition was very crystalline in appearance and did not seem to contain any glass. Since the only difference between batch 19 and the batch with clean resin (#17) was the presence of radioactive material and the other species captured during the ion exchange filtration process, SEM analysis was performed on the product of batch 19 to determine if any unanticipated elements were present. The SEM analysis did not detect the presence of any elements other than the additives used in batching and some minor amounts of Al and K, which can be attributed to the Al₂O₃ crucible and the basin water, respectively.

The spent resin solution was submitted for total inorganic/total organic analysis to determine how much of the resin had not been oxidized. From the analyses of the spent resin solution, it was determined that 58,700 ppm of organic carbon and 1024 ppm of inorganic carbon had not been destroyed in the oxidation process. This could be partially attributed to the fact that Palladium had not been added during the oxidation step, which normally serves to help oxidize the organics. In order to give the remaining organics more time to pyrolyze during the vitrification process, a slower heat-up rate was used for the furnace. A new batch of feed (#20) was made using the same composition as batch 19, which was the same as the clean resin batch 17. This batch was heated to 1150°C at approximately 5°C/min and melted at 1150°C for 4 hours. The resulting product was a homogeneous black glass.

Table 14 - Dissolved Spent Resin Composition

Species	Content
Al	130 ppm
B	11.1 ppm
Ca	451 ppm
Cd	2.7 ppm
Cr	9.3 ppm
Cu	6.7 ppm
Fe	191 ppm
Mg	31 ppm
Na	6582 ppm
Ni	22.4 ppm
P	174,260 ppm
Si	<2.7 ppm
Zn	16.5 ppm
Cl-	1776 ppm
F-	274 ppm
NO3-	27,236 ppm
PO43-	<1000 ppm
SO42-	15,865 ppm
alpha	9.4 X 104 dpm/mL
Beta/Tritium	3.1 X 105 dpm/mL
Cs-137	6.29 X 10-2 µCi/mL
Tritium	2.31 X 10-2 µCi/mL

Glass 20 was characterized for chemical composition and PCT durability. The TCLP was also performed to determine the leaching behavior of the Resource Conservation and Recovery Act (RCRA) metals.

The chemical composition of glass 20 is given in Table 15. Glass 20 was very similar in composition to glass 17, which was the same batch composition, but clean resin solution was used instead of spent resin solution. The only major difference was the amount of Na₂O present. This difference may have resulted from either analytical or batching error, since glass 20 was found to contain 0.233 wt% Na₂O, while glass 17 contained 4.947 wt% Na₂O. Both of these glasses should have contained the same amount of Na₂O, so either the analysis for Na₂O were flawed or the glass was not mixed properly. In all likelihood, an error occurred during analysis, since the remaining principle components were near the expected concentrations. A few oxides were slightly higher for the spent resin, but most of the differences can be attributed to the contaminants expected to be present in reactor basin waters. SiO₂ probably increased due to Si leaching from the oxidation processing vessel.

Table 15 - Chemical Compositions Results for
Spent Resin Iron-Phosphate Glasses

Oxide	#20	#17
Al2O3	2.649	1.931
B2O3	0.013	0.025
BaO	2.796	2.780
CaO	0.262	0.235
Cr2O3	0.162	0.098
Fe2O3	34.007	33.947
La2O3	0.023	0.005
Na2O	0.233	4.947
Nd2O3	0.142	0.032
NiO	0.066	0.025
P2O5	58.383	59.834
PbO	0.173	0.026
SiO2	0.199	0.030
SrO	0.007	0.002
Total	99.116	103.854

A gamma PHA on the glass indicated a Cs-137 content of 4.22 X 10-2 µCi/g or a total of 1.181 µCi. Based on the analyses of the spent resin solution, which indicated that the Cs-137 activity was 6.29 X 10-2 µCi/mL or a total of 1.037 µCi of Cs-137 were in the solution stabilized in the glass. These values indicate that the Cs was retained.

The standard PCT procedure was performed on glass 20 and the triplicate results were averaged. These results were normalized for the glass elemental content. The results were 0.031 g/L P, 0.002 g/L Ba, 3.104 g/L Na, and 0.000 g/L Fe, with a measured leachate pH of 6.00. When compared to the normalized results for the clean resin glass (#17), the results for P, Ba, and Fe were not much different. Na release, however, was much greater for the spent resin glass (#20). This may be directly attributed to the suspected analytical errors discussed above. The raw data for the two glasses indicated that the Na release for glass 20 was 5.37 ppm, while the Na release for glass 17 was 3.19 ppm, which was not a very substantial difference. However, the decrease in Na content in glass 20 would have resulted in a higher normalized Na release when this value was calculated. Therefore, the differences in Na normalized release were probably an artifact of the faulty chemical composition analysis for Na₂O in glass 20, and the releases were probably equivalent. In either case, the Na release was much less than the EA accepted value for HLW borosilicate glasses.

The principal radioactive component of concern for the resins was Cs. Results for Cs are not presented in the table since the quantities released were very small. Leachate analyses results by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) indicate that 0.91 - 6.27 ppb of stable Cs-133 leached out and 3.44 - 4.53 ppb of Cs-137 leached out. Most of the Cs-137 numbers were tainted by the presence of Ba-137, which is a stable form of Ba and was a principle glass component. Most of the ICP-MS data indicated that at least 80% of the 137 isotope released was Ba.

A TCLP extraction using the modified EPA protocol was performed to determine the RCRA metal leaching. The modification consisted of using ground glass, approximately 150 µm, instead of the specified <1 cm glass specimen size. This was done because of the small amount of glass produced and would produce conservative results because of the larger sample surface area available for leaching. Results indicated that Ba was the only RCRA metal to leach above the analytical detection limits. Its release was 1.049 ppm, which is much lower than any of the EPA allowable limits.

The nitric-phosphoric acid oxidation process has been successful in dissolving 360 ml of resin in 100 ml of solution. Attempts are underway to vitrify this solution in a stable iron-phosphate glass matrix. If successful, this will result in a six fold volume reduction.

Crucible studies using the CaO-Fe₂O₃-SiO₂ glass system and clean cation/anion resin have shown that the organic content of the resin can be destroyed and the residue incorporated into a durable glass wasteform. However, using this process limits the resin loading to about 20 grams of resin/100 grams of glass produced. While this loading is higher than what has been seen in previous studies (5 grams of resin/100 grams of glass produced), it is still relatively low from a waste volume reduction standpoint. This may be appropriate for high radiation field resins or where loadings need to be kept to modest levels to restrict radiation doses. This glass composition could also be utilized when other wastes are being treated because the combination of the other waste and the resin would result in a better overall volume reduction.

The waste loading of the resin glasses can be maximized by using the referenced two step treatment process. When the nitric-phosphoric acid oxidation pre-treatment was used, 120 mL of the resin was dissolved in 100 mL of acidic solution. This solution can then be incorporated into an iron-phosphate glass matrix at a 57 wt% loading. The volume reduction was two fold, and researchers expect that a volume reduction of six to twenty fold is attainable. Cs-137 was retained during the vitrification process. Leach resistance of this final glass product with actual spent resin was exceptionally good. No significant quantities of the glass structure components or detectable amounts of cesium were leached from the glass product. TCLP results indicated that the Ba glass component and other RCRA metals did not leach above allowable limits from the glass.

Funding for this research and development work was provided by the Department of Energy - Office of Technology Development under the auspices of the Mixed Waste Focus Area and Technical Task Plan SR1-3-20-04 and SR1-6-MW-42.

The efforts of all personnel involved with this project are greatly appreciated. These include but are not limited to the following:

• Rich Deible of Reactor Engineering for his assistance in obtaining the clean and spent resins, as well as the available characterization data.

• RBOF operations for pulling and transporting the spent resin samples.

• Robert Pierce, James Clark, and Jim Smith of Chemical Technology Section for their efforts in oxidizing the resins.

• Phyllis Workman and Irene Reamer for their help with batching and melting the glasses.

• Phyllis Workman, Irene Reamer, and Mary Andrews for their help with performing the PCTs.

• Gene Ramsey and John Pareizs for the Iron-Phosphate glass composition formulation assistance.

1. N. E. Bibler, J. P. Bibler, M. K. Andrews, and C. M. Jantzen, "Initial Demonstration of the Vitrification of High-Level Nuclear Waste Sludge Containing an Organic Cs-Loaded Ion Exchange Resin", Presented at the Materials Research Society Meeting 1992, WSRC-MS-91-465.
   
2. T. N. Sargent, "Vitrification of Cesium-Contaminated Organic Ion Exchange Resin", Graduate Thesis for Clemson University - Environmental Systems Engineering, August 1994.
   
3. R. G. Ragsdale, "XRF and Leaching Characterization of Waste Glasses Derived from Wastewater Treatment Sludges", Graduate Thesis for Clemson University - Environmental Systems Engineering, December 1994.
   
4. C.M. Jantzen, N.E. Bibler, D.C. Beam, and W.G. Ramsey, "Nuclear Waste Product Consistency Test (PCT) - Version 7.0", WSRC-TR-90-539, Rev. 3.
   
5. C.M. Jantzen, N.E. Bibler, D.C. Beam, C.L. Crawford, M.A. Pickett, "Characterization of the Defense Waste Processing Facility (DWPF) Environmental Assessment (EA) Glass Standard Reference Material," WSRC-TR-92-346, Rev. 1, June 1, 1993.
   
6. R.A. Pierce, "Method for Acid Oxidation of Radioactive, Hazardous, and Mixed Organic Waste Materials", U.S. Patent # 5,960,368, Sept. 28, 1999.