Reduction of Sodium Nitrate Liquid Waste in Nuclear Reprocessing Plants

Conference · Sat Jul 01 04:00:00 EDT 2006

OSTI ID:21208659

Numata, M; Mihara, S; Kojima, S; Ito, H ^[1]; Kato, T ^[2]

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1. JGC Corporation, Technologies Research Center, 2205, Narita-cho, Oarai-machi, Higashiibarakigun, Ibaraki Pref., 311-1313 (Japan)
2. JGC Corporation, Yokohama World Operation Center, 2-3-1, Minato Mirai, Nishi-ku, Yokohama, Kanagawa Pref., 220-6001 (Japan)

Sodium nitrate solution has been generated from nuclear reprocessing plant as a result of neutralization of nitric acid. The sodium nitrate has been immobilized by bitumen, cement or other material in the site and waste packages have been produced. In order to reduce an environmental impact of the waste packages from the reprocessing plant, it is preferable to decompose nitrate ion to harmless gases such as nitrogen. A combination of formic acid and catalyst has been proposed for this purpose. But, the method is inadequate for a full decomposition of the nitrate ion. In addition, a mixture of NO and NO{sub 2} is produced during the reaction. Formaldehyde and hydrazine were selected as reductants and a combined use of Pd-Cu catalyst was tried to decompose the nitrate ion. As a result, the nitrate ion can almost entirely be decomposed without any generation of NO and NO{sub 2}. The test was conducted by 1 L flask. In case of formaldehyde, nitrate ion concentration can be reduced from 0.017 mol/l to 3.9x10{sup -4} mol/l. In case of hydrazine, nitrate concentration can be decreased from 2.8 mol/l to 9.5 x 10{sup -3} mol/l and ammonium ion is detected. The ammonium ion concentration in the final solution is 0.12 mol/l when 2.8 mol/l nitrate is reduced by hydrazine. Chemical reactions for formaldehyde on the Pd-Cu catalyst are estimated as combination of: NO{sub 3-} + HCHO = NO{sub 2-} + HCOOH; 2NO{sub 2-} + 3HCOOH = N{sub 2} + 3CO{sub 2} + 2H{sub 2}O + 2OH-; 4NO{sub 2-} + 3HCHO = 2N{sub 2} + 3CO{sub 2} + H{sub 2}O + 4OH-. the other hand, for hydrazine with the Pd-Cu catalyst: 3N{sub 2}H{sub 4} = 2NH{sub 3} + 2N{sub 2} + 3H{sub 2}; NO{sub 3-} + H{sub 2} = NO{sub 2-} + H{sub 2}O; NO{sub 2-} + NH{sub 3} = N{sub 2} + H{sub 2}O + OH-. The fundamental research shows that the combination usage of the Pd-Cu catalyst and formaldehyde or hydrazine is applicable for the reduction of nitrate liquid waste in the nuclear reprocessing plant. (authors)

• Research Organization: WM Symposia, Inc., PO Box 13023, Tucson, AZ, 85732-3023 (United States)
• OSTI ID: 21208659
• Report Number(s): INIS-US--09-WM-06177
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
BITUMENS
CASKS
CEMENTS
ENVIRONMENTAL IMPACTS
FUEL REPROCESSING PLANTS
LIQUID WASTES
NITRIC ACID
NITRIC OXIDE
NITROGEN DIOXIDE
RADIOACTIVE WASTES
SODIUM NITRATES