Fernando F. Fondeur

INVESTIGATING HYDROGEN GENERATION AND CORROSION IN THE TREATMENT TANK AND THE POTENTIAL FORMATION OF A FLOATING LAYER IN NEUTRALIZATION TANK DURING WASTE TANK HEEL CHEMICAL CLEANING

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Reactivity of Resorcinol Formaldehyde Resin with Nitric Acid

Abstract Solid‐state infrared spectroscopy, differential scanning calorimetry, and elemental analysis have been used to evaluate the reactivity of resorcinol formaldehyde resin with nitric acid and characterize the solid product. Two distinct reactions were identified within the temperature range 25–55°C. The first reaction is primarily associated with resin nitration, while the second involves bulk oxidation and degradation of the polymer network leading to dissolution and off‐gassing. Reaction was confirmed with nitric acid concentrations as low as 3 M at 25°C applied temperature and 0.625 M at 66°C. Although a nitrated resin product can be isolated under appropriate experimental conditions, calorimetry testing indicates no significant hazard associated with handling the dry material.

Thermal Stability of Formohydroxamic Acid

The thermal stability of formohydroxamic acid (FHA) was evaluated to address the potential for exothermic decomposition during storage and its use in the uranium extraction process. Accelerating rate calorimetry showed rapid decomposition at a temperature above 65°C; although, the rate of pressure rise was greater than two orders of magnitude less than the lower bound for materials which have no explosive properties with respect to transportation. An FHA solution in nitric acid did not reach runaway conditions until 150°C. Water appeared to temper the FHA decomposition. Analysis by differential scanning calorimetry showed that FHA melted at 67°C and thermally decomposed at 90°C with an enthalpy of −1924 J/g. The energics of the FHA thermal decomposition are comparable to those measured for aqueous solutions of hydroxylamine nitrate. Solid FHA should be stored in a location where the temperature does not exceed 20–25°C. As a best practice, the solid material should be stored in a climate-controlled environment such as a refrigerator or freezer. FHA solutions in water are not susceptible to degradation by acid hydrolysis and are the preferred way to handle FHA prior to use.

THERMAL AND SPECTROSCOPIC ANALYSES OF CAUSTIC LIDE SOLVENT EXTRACTION SOLVENT CONTACTED WITH 16 MOLAR AND 8 MOLAR NITRIC ACID

Thermal and spectroscopic analyses were performed on multiple layers formed from contacting Caustic Side Solvent Extraction (CSSX) solvent with 1 M or 3 M nitric acid. A slow chemical reaction occurs (i.e., over several weeks) between the solvent and 1 M or 3 M nitric acid as evidenced by color changes and the detection of nitro groups in the infrared spectrum of the aged samples. Thermal analysis revealed that decomposition of the resulting mixture does not meet the definition of explosive or deflagrating material.

The Effect of Magnetic Fields on Uranium and Strontium Sorption on Monosodium Titanate

The presence of a magnetic field gradient enhanced the rate of strontium and uranium sorption onto monosodium titanate. The enhancement was evident only in the early contact times and did not impact the equilibrium capacity of the sorbent. No enhancement was seen when the sorption test was conducted under a homogeneous magnetic field. Further studies are needed to determine if the enhancement is also seen with other cations and/or anions.

Analysis of solids remaining following chemical cleaning in tank 6F

Following chemical cleaning, a solid sample was collected and submitted to Savannah River National Laboratory (SRNL) for analysis. SRNL analyzed this sample by X-ray Diffraction (XRD) and scanning electron microscopy (SEM) to determine the composition of the solids remaining in Tank 6F and to assess the effectiveness of the chemical cleaning process.

Analysis of antifoam agent degradation products in an evaporator

ABSTRACT A wetting agent used to control foaming in the Chemical Processing Cell at the Defense Waste Processing Facility degrades to form compounds that could volatilize to form vapor exceeding the lower flammability limit. Three identified components of concern were hexamethyl disiloxane, trimethyl silanol, and propanal. Analytical methods were developed and implemented on a real waste sample to monitor degradation products. Using standards, an extraction method with dichloromethane and analysis by gas chromatography-mass spectrometry and hydrogen nuclear magnetic resonance was developed. Both methods had detection limits less than 1 mg/L for the analytes.

Determination of the Impact of Glycolate on Cs, Sr, and Actinide Separations in High-Level Waste

The Defense Waste Processing Facility (DWPF), responsible for vitrifying high-level waste (HLW) at the Savannah River Site (SRS), is planning to introduce glycolic acid as a reductant during chemical conditioning of the waste prior to vitrification. A portion of this glycolic acid may be recycled back to the tank farm as sodium glycolate. Since glycolate can serve as a complexing agent for a variety of metallic ions, recent studies were performed to examine the effect of glycolate on the removal of Sr and actinides by monosodium titanate (MST) and modified MST (mMST) and the separation of Cs by the caustic-side solvent extraction (CSSX) process.

Analysis of the Leaching Efficiency of Inhibited Water and Tank Simulant in Removing Residues on Thermowell Pipes

A cleaning protocol was determined and modeled, using the shrinking core model, for the removal of a solid residue coating thermo well pipes contained in the riser of a Savannah River Site (SRS) waste tank (Tank 48H). The solid residues on two sets of thermo well pipe samples removed from the D2 riser in SRS Tank 48H were characterized by high performance liquid chromatography (HPLC), ion chromatography (IC) and gamma spectroscopy. The residue thickness was determined using the ASTM standard D 3483-05 and was found to be three orders of magnitudes below the 1 mm thickness estimated from an earlier video of the tank cooling coil inspection. The actual estimated thickness ranged from 4 to 20.4 microns. The mass per unit area ranged from 0.15 to 0.82 milligrams per square centimeter. The residues appear to consist primarily of potassium tetraphenylborate (39.8 wt% KTPB) and dried salt solution (33.5 wt% total of nitrates, nitrites, and oxalate salts), although ∼30% of the solid mass was not accounted for in the mass balance. No evidence of residue buildup was found inside the pipe, as expected. Two aqueous solutions representing waste processing streams were chosen for the cleaning trials. The residue leaching characteristics were measured by placing one pipe in inhibited water (0.01 M NaNO2 and 0.01 M NaOH) and one pipe in Defense Waste Processing Facility (DWPF) Recycle simulant (primarily 0.20 M NaNO2 and 0.18 M NaOH). After soaking for less than 4 weeks, the inhibited water was 95.4% effective at removing the residue and the DWPF Recycle simulant was 93.5% effective. The surface appearance of the pipes after leaching tests appeared close to the clean shiny appearance of a new pipe. Total gamma counts of leachates averaged 48.1 dpm/mL, or an equivalent of 2.35E-11 Ci/gm Cs-137 (dry solids basis), which is much lower than the 1.4 E-03 Ci/gm expected for Tank 48H dry slurry solids.

An Accelerated Rate Calorimetry Study of Caustic-Side Solvent Extraction Solvent without Extractant

This study found that 4 - 48 part per thousand (ppth) of Caustic Side Solvent Extraction (CSSX) solvent without extractant in caustic salt solution at evaporator-relevant temperatures result in no process-significant energetic events. However, the data suggest a chemical reaction (possible decomposition) in the CSSX solvent near 140 C. This concentration of entrained solvent is believed to markedly exceed the amount of solvent that will pass from the Modular Caustic Side Solvent Unit (MCU) through the downstream Defense Waste Processing Facility and enter the evaporator through routine tank farm operations. The rate of pressure rise at 140 C differs appreciably - i.e., is reduced - for salt solution containing the organic from that of the same solution without solvent. This behavior is due to a reaction between the CSSX components and the salt solution simulant.