Materials Recovery and Waste Form Development -- Slides for Low Temperature Chlorination
These slides showcase the work done by INL in the low temperature chlorination work package during FY25.
11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
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Advanced Low-Temperature Chlorination of Zirconium
Recovery of Zr from nuclear fuel is of high interest because the Zr cladding material comprises up to 50% of the high-level radioactive waste (HLW) that requires disposition. An ideal Zr-recovery process would not only recover the bulk Zr from the fuel or cladding but would also provide decontamination from the components that give rise to the HLW designation. A simplified decontamination pathway providing recovered Zr in compliance with low-level radioactive waste acceptance criteria could significantly reduce the burden of HLW requiring geologic disposition. A newly developed advanced low-temperature chlorination process presents an opportunity to recover a ZrCl4 product that is effectively decontaminated from the elements of concern. This advanced low-temperature chlorination process uses a mixture of the sulfur-containing chlorination compounds sulfur monochloride (S 2 Cl 2 ) and thionyl chloride (SOCl 2 ).
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Completion and Testing of a New High-Temperature Cell Holder to Support High Dose Rate Electron Beam Irradiations of Select Sulfur Chlorides (S2Cl2 and SOCl2) for Advanced Low Temperature Chlorination of Zirconium-based Used Nuclear Fuel Cladding
Short communication on the completion and testing of a new high-temperature cell holder to support high dose rate electron beam irradiations of select sulfur chlorides (S2Cl2 and SOCl2) for advanced low temperature chlorination of zirconium-based used nuclear fuel cladding.
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
Radiolytic evaluation of select sulfur chlorides (S 2 Cl 2 and SOCl 2 ) for advanced low temperature chlorination of zirconium-based used nuclear fuel cladding
New sulfur chloride compounds—sulfur monochloride (S 2 Cl 2 ) and thionyl chloride (SOCl 2 )—have been proposed as alternative chlorinating agents for the chemical decladding of zirconium-based used nuclear fuel cladding materials. However, the radiation stability of these compounds has not been thoroughly evaluated, despite envisioned process conditions involving intense, multi-component radiation fields. Knowledge of the radiation chemistry of these sulfur chlorides is essential for the development and optimization of alternative chlorination technologies. To this end, we present preliminary findings on the gamma radiolysis of neat S 2 Cl 2 and SOCl 2 at ambient temperature up to ~ 34 MGy. In this study, Raman spectroscopy and density functional theory calculations were used to identify the Raman-active degradation products from S 2 Cl 2 and SOCl 2 radiolysis. Both sulfur chloride compounds exhibited significant radiation resistance, with respect to changes in the Raman signatures of the parent compounds and the ingrowth of Raman-active degradation products. For S 2 Cl 2 , molecular chlorine (Cl 2 ) was directly identified as the predominant degradation product, which was completely consumed at higher absorbed doses (> 9 MGy). Similarly, the main degradation product from SOCl 2 radiolysis was also Cl 2 , although in this system it continued to grow in with dose over the entire dose range. Further, an “S=O” containing degradation product(s) was also identified as a compliment to Cl 2 . Overall, the perceived radiation resistance of these sulfur chloride compounds makes them suitable for inclusion in a used nuclear fuel chemical decladding process, especially as radiolytically formed Cl 2 can be used to reform the parent compounds, thereby increasing the longevity of the solvents used.
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
Preliminary Assessment of Alternate Chlorination Process
Recent advancements towards low-temperature chlorination with disulfur dichloride and thionyl chloride of Al-clad used nuclear fuel (UNF) have been summarized for work control technical expertise development at the Savannah River National Laboratory (SRNL). This technique aims to provide a more effective method for separating U from cladding or alloying elements. A preliminary assessment determined needs for unit operation developments in regard to reaction kinetics and reagent quality. Furthermore, an analysis of an Uruguay fuel plate (U-Al x fuel meat), with low-enriched uranium (LEU) and located at SRNL, was a potential candidate for future experiments with lightly irradiated (0.08% burnup) fuel to test for chlorination. Future proposed work would involve kinetic studies, reagent quality assessments, and the machining of the fuel plate down to an appropriate bench-scale size and testing the effectiveness of low-temperature chlorination on the fuel plate.
Chlorination↗
Alternate Chlorination: Status & Upcoming Activities for Evaluating Radiation Stability of S2Cl2/SOCl2 Systems
Presentation covering the INL Center for Radiation Chemistry Research's progress on evaluating the radiation stability of select sulfur chlorides (S2Cl2 and SOCl2) for alternative advanced low temperature chlorination of zirconium-based used nuclear fuel cladding.
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
Tests of stratospheric models - The reactions of atomic chlorine with O3 and CH4 at low temperature
The rate-constant ratio of the photochemical reactions of atomic chlorine with O3 and CH4 was determined using data from laboratory experiments on competitive chlorination of O3/CH4 mixtures at stratospheric temperatures (197-217 K). Two experimental approaches were used: (1) measuring the k1/k2 ratio for the reactions of atomic chlorine with ozone and methane and (2) testing for some of the ClO/CH3O2 chemistry. The chlorine and ozone concentrations were monitored by UV-Vis spectroscopy, and the CH3Cl concentration was measured by FTIR. The results on the k1/k2 ratio are in excellent agreement with the current NASA recommendation (DeMore et al., 1990), being only 12 percent higher. On the other hand, results on the ClO + CH3O2 reaction do not support the rate constant suggested by Simon et al. (1989).
Demore, W. B.↗
The chlorination and separation of aluminum using low-temperature sulfur chloride reagents
There is currently no strategy for the permanent waste disposal or recycling for used nuclear fuelsfrom research reactors. For this reason, low-temperature reactions have been developed for thechlorination of the Al alloys and subsequent separation from used nuclear fuels to reducethe volume of high-level waste in storage. Three sulfur chloride reagents – S 2 Cl 2 , SOCl 2 , and SO 2 Cl 2 —were tested, and two were found to quantitatively chlorinate Al metal and Al alloys undermild conditions. Further, these low-temperature reactions proceed between 298 and 411 K, and up to 5 gof metal is chlorinated in 1–3 h. Preliminary results indicate that the reactivity and exothermicity ofthe reaction between the Al and sulfur chloride reagents is highly dependent on the surface area-to-volume ratio of the metal and the volume of solvent. Elemental S is produced as a by-productduring the chlorination with S 2 Cl 2 but can be quantitatively rechlorinated under mild conditions toregenerate the initial chlorination reagent. Therefore, in this case, chlorine is the only elementconsumed in the reaction, thus minimizing the waste generated during the chlorination process.The AlCl 3 may then be separated from other materials present in Al 6061 or Al 8001 because of itshigh solubility in the sulfur chloride reagents. This process may also be extended to chlorinate Alfrom research reactor fuels.
aluminum↗
Application of Chlorine-Assisted Chemical Vapor Deposition of Diamond at Low Temperatures
Low temperature deposition of diamond has been achieved by a chlorine-assisted diamond chemical vapor deposition (CA-CVD) process. This method begins with the thermal dissociation of molecular chlorine into atomic chlorine in a resistively heated graphite furnace at temperatures between 1300 and 1500 deg. C. The atomic chlorine, upon mixing, subsequently reacts with molecular hydrogen and hydrocarbons. The rapid exchange reactions between the atomic chlorine, molecular hydrogen, and hydrocarbons give rise to the atomic hydrogen and carbon precursors required for diamond deposition. Homoepitaxial diamond growth on diamond substrates has been studied over the substrate temperature range of 100-950 C. It was found that the diamond growth rates are approximately 0.2 microns/hr in the temperature range between 102 and 300 C and that the growth rates do not decrease significantly with a decrease in substrate temperature. This is unique because the traditional diamond deposition using H2/CH4 systems usually disappears at substrate temperatures below approx. 500 deg. C. This opens up a possible route to the deposition of diamond on low-melting point materials such as aluminum and its alloys.
Pan, Chenyu↗
HCl Vapour Pressures and Reaction Probabilities for ClONO2 + HCl on Liquid H2SO4-HNO3-HCl-H20 Solutions
Henry's Law solubility constants for HCl have been measured for liquid H2SO4-HNO3-HCl-H2O solutions; the results are in good agreement with predictions from published semiempirical models. The ClONO2 + HCl reaction on the surfaces of such solutions with compositions simulating those of stratospheric aerosols has been investigated; as the composition changes following the temperature drop characteristic of the high-latitude stratosphere the reaction probability gamma increases rapidly. Furthermore, the gamma values remain essentially unchanged when HN03 uptake is neglected; the controlling factor appears to be the solubility of HCl. These results corroborate our earlier suggestion that supercooled liquid sulfate aerosols promote chlorine activation at low temperatures as efficiently as solid polar stratospheric cloud particles.
Elrod, M. J.↗
A molecular beam mass spectrometric study of the formation and photolysis of C(lc)lO dimer
A study of the chlorine oxides present at temperatures and pressures typical of the Antarctic stratosphere was carried out. A series of low temperature flow reactors was constructed and used in conjunction with molecular beam mass spectrometric techniques to identify species and characterize their kinetic behavior at temperatures of -20 to -70 C and pressures of from 30 to 130 Torr. It was found that the gas phase chlorine-oxygen system was quite complex at low temperatures. ClO dimer was identified and found to be thermodynamically very stable under stratospheric conditions. It was also found that any system which contained ClO also contained a larger oxide. The oxide was identified as Cl2O3. A survey of possible higher oxides, which have been postulated as possible chlorine sinks in the stratosphere, was also carried out. The rate of formation of ClO dimer was measured as a function of temperature and pressure. Measurements were made of both the decay of ClO and the formation of the dimer. By comparing these rates it was determined that virtually all of the ClO was converted to the dimer under stratospheric conditions, and that the other ClO reactions were not important under these conditions.
Greene, Frank T.↗
Integrated low-temperature PVC and polyolefin upgrading
Polyolefins and their chlorinated derivatives such as polyvinyl chloride (PVC) are among the most prevalent plastics in global production and waste streams. Traditional waste-to-energy methods such as incineration and pyrolysis, as well as most chemical upcycling methods for PVC utilization, require thorough, high-temperature dechlorination to prevent the release of toxic chlorinated compounds. Here, we present here a strategy for upgrading discarded PVC into chlorine-free fuel range hydrocarbons and hydrogen chloride in a single-stage process catalyzed by chloroaluminate ionic liquids. This approach offsets endothermic dechlorination and carbon-carbon bond cleavage with exothermic alkylation and hydrogen transfer by isobutane or isopentane in a low-temperature tandem process. The light isoalkanes are available from refinery processes and partly from recycling of the product stream. This process is suitable for handling real-world mixed and contaminated PVC and polyolefin waste streams.
Zhang, Wei [East China Normal Univ. (ECNU), Shangh↗
Martian subsurface cryosalt expansion and collapse as trigger for landslides
On Mars, seasonal martian flow features known as recurring slope lineae (RSL) are prevalent on sun-facing slopes and are associated with salts. On Earth, subsurface interactions of gypsum with chlorides and oxychlorine salts wreak havoc: instigating sinkholes, cave collapse, debris flows, and upheave. Here, we illustrate (i) the disruptive potential of sulfate-chloride reactions in laboratory soil crust experiments, (ii) the formation of thin films of mixed ice-liquid water “slush” at −40° to −20°C on salty Mars analog grains, (iii) how mixtures of sulfates and chlorine salts affect their solubilities in low-temperature environments, and (iv) how these salt brines could be contributing to RSL formation on Mars. Our results demonstrate that interactions of sulfates and chlorine salts in fine-grained soils on Mars could absorb water, expand, deliquesce, cause subsidence, form crusts, disrupt surfaces, and ultimately produce landslides after dust loading on these unstable surfaces.
J. L. Bishop↗
Chemistry of the CO dimer at low temperatures
Researchers conducted a series of experiments on the chlorine-catalyzed photodecomposition of O sub 3 both in the gas and in inert solvents such as CF sub 4 and CO sub 2 in the temperature range about 190 to 225 K. The liquid medium was chosen in order to minimize possible surface loss of long-lived ClO dimer, and to aid in the stabilization of transient excited intermediates. The mechanism of dimer formation was as follows: (1) Cl sub 2 + hv yields Cl + Cl; (2) Cl + O sub 3 yields ClO + O sub 2; (3) ClO + ClO yields Cl sub 2 O sub 2. The experiments were done in cooled low temperature cells, with irradiation from an Osram high pressure mercury arc, filtered to remove radiation below 325 nm. Spectral analysis was by means of a Cary Model 2200 UV spectrometer. The principal objectives were: (1) to determine the lifetime of the dimer as a function of temperature; (2) to observe spectral changes in the mixtures which could be attributed to dimer or related products; and (3) to observe chemical or photochemical reactions of the dimer.
Demore, W. B.↗
Hydrodesulfurization of chlorinized coal
A method of desulfurization is described in which high sulfur coals are desulfurized by low temperature chlorinolysis of coal in liquid media, preferably water, followed by hydrodesulfurization at a temperature above 500 C. The coals are desulfurized to an extent of up to 90% by weight and simultaneously dechlorinated to a chlorine content below 0.1% by weight. The product coals have lower volatiles loss, lower oxygen and nitrogen content and higher fixed carbon than raw coals treated with hydrogen under the same conditions. Heating the chlorinated coal to a temperature above 500 C. in inert gas such as nitrogen results in significantly less desulfurization.
Kalvinskas, J. J.↗
Uptake of Hypobromous Acid (HOBr) by Aqueous Sulfuric Acid Solutions: Low-Temperature Solubility and Reaction
Hypobromous acid (HOBr) is a key species linking inorganic bromine to the chlorine and odd hydrogen chemical families. We have measured the solubility of HOBr in 45 - 70 wt% sulfuric acid solutions representative of upper tropospheric and lower stratospheric aerosol composition. Over the temperature range 201 - 252 K, HOBr is quite soluble in sulfuric acid, with an effective Henry's law coefficient, H* = 10(exp 4) - 10(exp 7) mol/L/atm. H* is inversely dependent on temperature, with Delta H = -46.2 kJ/mol and Delta S = -106.2 J/mol/K for 55 - 70 wt% H2SO4 solutions. Our study includes temperatures which overlap both previous measurements of HOBr solubility. For uptake into aqueous 45 wt% H2SO4, the solubility can be described by log H* = 3665/T - 10.63. For 55 - 70 wt% H2SO4, log H* = 2412/T - 5.55. At temperatures colder than approx. 213 K, the solubility of HOBr in 45 wt% H2SO4 is noticeably larger than in 70 wt% H2SO4. The solubility of HOBr is comparable to that of HBr, indicating that upper tropospheric and lower stratospheric aerosols should contain equilibrium concentrations of HOBr which equal or exceed those of HBr. Our measurements indicate chemical reaction of HOBr upon uptake into aqueous sulfuric acid in the presence of other brominated gases followed by evolution of gaseous products including Br2O and Br2, particularly at 70 wt% H2SO4.
Iraci, Laura T.↗
Coal desulfurization by aqueous chlorination
A method of desulfurizing coal is described in which chlorine gas is bubbled through an aqueous slurry of coal at low temperature below 130 degrees C., and at ambient pressure. Chlorinolysis converts both inorganic and organic sulfur components of coal into water soluble compounds which enter the aqueous suspending media. The media is separated after chlorinolysis and the coal dechlorinated at a temperature of from 300 C to 500 C to form a non-caking, low-sulfur coal product.
Kalvinskas, J. J.↗
Stability and photochemistry of ClO dimers formed at low temperature in the gas phase
The recent observations of elevated concentrations of the ClO radical in the austral spring over Antarctica have implicated catalytic destruction by chlorine in the large depletions seen in the total ozone column. One of the chemical theories consistent with an elevated concentration of the ClO is a cycle involving the formation of the ClO dimer through the association reaction: ClO + ClO = Cl2O2 and the photolysis of the dimer to give the active Cl species necessary for O3 depletion. Here, researchers report experimental studies designed to characterize the dimer of ClO formed by the association reaction at low temperatures. ClO was produced by static photolysis of several different precursor systems: Cl sub 2 + O sub 3; Cl sub 2 O sub 2; OClO + Cl sub 2 O spectroscopy in the U.V. region, which allowed the time dependence of Cl sub 2, Cl sub 2 O, ClO, OClO, O sub 3 and other absorbing molecules to be determined.
Cox, R. A.↗