Influence of NO{sub x} and HNO{sub 2} on iodine quantity in spent-fuel solutions

Journal Article · Sun Dec 01 04:00:00 EST 1996 · Nuclear Technology

OSTI ID:418084

Sakurai, Tsutomu; Takahashi, Akira; Ishikawa, Niroh; Komaki, Yoshihide; Ohnuki, Mamoru ^[1]

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1. Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Dept. of Chemistry and Fuel Research

The quantity of iodine in spent-fuel solutions tends to decrease with an increase in the dissolution rate. This phenomenon is ascribed to the presence of nitrous acid (HNO{sub 2}) generated in the dissolution process because of the following three findings: (a) in a hot nitric acid solution, the steady-state HNO{sub 2} concentration increases with an increase in the rate of its production and decreases with an increase in temperature, (b) the HNO{sub 2} decreases the quantity of colloidal iodine (the main component of residual iodine in a simulated spent-fuel solution) in proportion to its concentration up to {approximately}3.0 {times} 10{sup {minus}3} M, and (c) a higher dissolution rate of UO{sub 2} causes a higher HNO{sub 2} production rate, hence, a higher HNO{sub 2} concentration in the solution. The HNO{sub 2} did not appear (i.e., [HNO{sub 2}] < 2 {times} 10{sup {minus}4} M) in the dissolution of a UO{sub 2} pellet ({approximately}1 g) with a low dissolution rate, 0.4 g/h of UO{sub 2} at 100 C. When high concentrations of I{sub 2} and NO{sub 2} (263 parts per million of I{sub 2} and 38% of NO{sub 2}) in an N{sub 2} flow were passed through a simulated spent-fuel solution at 100 C, the predicted colloid of AgI was produced as a chemical equilibrium product of the reaction AgI(s) + 2HNO{sub 3}(aq) = {1/2}I{sub 2}(aq) + AgNO{sub 3}(aq) + NO{sub 2}(g) + H{sub 2}O({ell}). This findings suggests that colloidal iodine may be produced secondarily in the dissolver of reprocessing plants; this can be one of the reasons why the residual iodine quantity in spent-fuel solutions is higher in reprocessing plants than in laboratory-scale experiments.

• Sponsoring Organization: Japanese Science and Technology Agency (Japan)
• OSTI ID: 418084
• Journal Information: Nuclear Technology, Journal Name: Nuclear Technology Journal Issue: 3 Vol. 116; ISSN 0029-5450; ISSN NUTYBB
• Country of Publication: United States
• Language: English

Related Subjects

05 NUCLEAR FUELS
ADSORBENTS
ECOLOGICAL CONCENTRATION
FUEL REPROCESSING PLANTS
FUEL SOLUTIONS
IODINE
NITROGEN OXIDES
OFF-GAS SYSTEMS
PRODUCTION
SAFETY ENGINEERING
SILVER IODIDES
SILVER NITRATES
URANIUM DIOXIDE