Volatilities of ruthenium, iodine, and technetium on calcining fission product nitrate wastes

Conference · Tue Jan 01 04:00:00 EST 1980

OSTI ID:5086905

Rimshaw, S J; Case, F N

Various high-level nitrate wastes were subjected to formic acid denitration. Formic acid reacts with the nitrate anion to yield noncondensable, inert gases according to the following equation: 4 HCOOH + 2 HNO/sub 3/ ..-->.. N/sub 2/O + 4 CO/sub 2/ + 5 H/sub 2/O. These gases can be scrubbed free of /sup 106/Ru, /sup 131/I, and /sup 99/Tc radioactivities prior to elimination from the plant by passage through HEPA filters. The formation of deleterious NO/sub x/ is avoided. Moreover, formic acid reduces ruthenium to a lower valence state with a sharp reduction in RuO/sub 4/ volatility during subsequent calcination of the pretreated waste. It is shown that a minimum of 3% of RuO/sub 4/ in an off-gas stream reacts with Davison silica gel (Grade 40) to give a fine RuO/sub 2/ aerosol having a particle size of 0.5 ..mu... This RuO/sub 2/ aerosol passes through water or weak acid scrub solutions but is trapped by a caustic scrub solution. Iodine volatilizes almost completely on calcining an acidic waste, and the iodine volatility increases with increasing calcination temperature. On calcining an alkaline sodium nitrate waste the iodine volatility is about an order of magnitude lower, with a relatively low iodine volatility of 0.39% at a calcination temperature of 250/sup 0/C and a moderate volatility of 9.5% at 600/sup 0/C. Volatilities of /sup 99/Tc were generally <1% on calcining acidic or basic wastes at temperatures of 250 to 600/sup 0/C. Data are presented to indicate that /sup 99/Tc concentrates in the alkaline sodium nitrate supernatant waste, with approx. 10 mg /sup 99/Tc being associated with each curie of /sup 137/Cs present in the waste. It is shown that lutidine (2,4 dimethyl-pyridine) extracts Tc(VII) quantitatively from alkaline supernatant wastes. The distribution coefficient (K/sub D/) for Tc(VII) going into the organic phase in the above system is 102 for a simulated West Valley waste and 191 for a simulated Savannah River Plant (SRP) waste.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: W-7405-ENG-26
• OSTI ID: 5086905
• Report Number(s): CONF-801038-4
• Country of Publication: United States
• Language: English

Related Subjects

052001* -- Nuclear Fuels-- Waste Processing
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
ANIONS
AZINES
CALCINATION
CARBOXYLIC ACIDS
CHALCOGENIDES
CHARGED PARTICLES
CHEMICAL REACTIONS
COMPARATIVE EVALUATIONS
DECOMPOSITION
DENITRATION
DEVOLATILIZATION
ELEMENTS
EXTRACTION
FORMIC ACID
HALOGENS
HETEROCYCLIC COMPOUNDS
HIGH TEMPERATURE
HIGH-LEVEL RADIOACTIVE WASTES
IODINE
IONS
MANAGEMENT
MATERIALS
METALS
MONOCARBOXYLIC ACIDS
NITRATES
NITROGEN COMPOUNDS
NONMETALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PLATINUM METALS
PROCESSING
PYRIDINES
PYROLYSIS
RADIOACTIVE MATERIALS
RADIOACTIVE WASTE PROCESSING
RADIOACTIVE WASTES
REDUCTION
REFRACTORY METALS
RUTHENIUM
RUTHENIUM COMPOUNDS
RUTHENIUM OXIDES
SEPARATION PROCESSES
SOLIDIFICATION
SOLVENT EXTRACTION
TECHNETIUM
TEMPERATURE DEPENDENCE
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
VERY HIGH TEMPERATURE
VOLATILITY
WASTE MANAGEMENT
WASTE PROCESSING
WASTES