The interaction of iodine with insoluble residue in the dissolution of simulated spent-fuel pellets

Journal Article · Mon Apr 01 04:00:00 EST 1991 · Nuclear Technology; (United States)

OSTI ID:5649949

Sakurai, T; Takahashi, A; Ishikawa, N; Komaki, Y ^[1]

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1. Japan Atomic Energy Research Inst., Physical Chemistry Lab., Tokai-mura, Ibaraki-ken 319-11 (JP)

To properly control radioiodine ({sup 129}I) when reprocessing nuclear fuels, it is important to understand the interaction between iodine and the insoluble residue produced during the dissolution of spent fuels. Simulated spent-fuel pellets ({approximately} 1 g each) equivalent to spent fuel with a burnup of 5% fima were dissolved in 4.1 M HNO{sub 3} or a simulated spent-fuel solution to examine this interaction and the material balance of iodine. In dissolution in 4.1 M HNO{sub 3}, 2 to 5% of the iodine in the pellet is conveyed to the insoluble residue (8 {plus minus} 1 mg), 1 to 5% remains in solution, and the balance volatilizes into the off-gas. The process that incorporates iodine into the residue is the formation of slightly soluble iodides, such as PdI{sub 2} and AgI, on the surface of the residue. The quantity of iodine in the residue averages 1.1 {plus minus} 0.5 Mg I/mg of residue. Pellet dissolution in simulated spent-fuel solutions with a uranium concentration of {ge}170 g U/{ell} and corresponding amounts of fission product elements causes a marked increase in the amount of residue and a significant increase in the amount of iodine involved. This phenomenon is due to the secondary precipitation of some metal molybdates. The PdI{sub 2} and AgI in the residue are in equilibrium with Pd{sup 2+}, Ag{sup +}, and I{sup {minus}} in the solution. The I{sup {minus}} can be oxidized into I{sub 2} in a hot nitric acid solution bubbled with NO{sub 2}. The action of NO{sub 2} causes part of the iodine in the residue to be eluted into the solution and then volatilized into the off-gas during the operation to expel iodine (IO{sup {minus}}{sup 3}) form the solution. A process consisting of (a) heating of the residue in a IO{sup {minus}}{sub 3}-concentrated HNO{sub 3} at 100{degrees} C will transfer 50 to 90% of the iodine in the residue to the gas phase. The remaining iodine is probably inside the residue as it is difficult to remove.

• OSTI ID: 5649949
• Journal Information: Nuclear Technology; (United States), Journal Name: Nuclear Technology; (United States) Vol. 94:1; ISSN NUTYB; ISSN 0029-5450
• Country of Publication: United States
• Language: English

Related Subjects

050800* -- Nuclear Fuels-- Spent Fuels Reprocessing
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
ACTINIDES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHALCOGENIDES
DISSOLUTION
ELEMENTS
ENERGY SOURCES
FUEL PELLETS
FUELS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IODINE 129
IODINE ISOTOPES
ISOTOPES
MATERIALS
METALS
NITRIC ACID
NITROGEN COMPOUNDS
NITROGEN OXIDES
NUCLEAR FUELS
NUCLEI
ODD-EVEN NUCLEI
OXIDES
OXYGEN COMPOUNDS
PELLETS
QUANTITY RATIO
RADIOISOTOPES
REACTOR MATERIALS
REPROCESSING
RESIDUES
SEPARATION PROCESSES
SIMULATION
SPENT FUELS
URANIUM
YEARS LIVING RADIOISOTOPES