Investigation of the spent fuel element of the first atomic power station

Smirnov-Averin, A.P.; Galkov, V. I.; Sevast'yanov, Yu.G.; Крот, Н. Н.; Ivanov, Vladimir I.; Sheinker, I. G.; Stabenova, L. A.; Kir'yanov, B. S.; Kozlov, A. G.

doi:10.1007/bf01484526

Cited by 4 publications

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“…After coagulation, the precipitate was centrifuged, washed with ice-cold double-distilled water, dissolved in the minimal amount of HClO 4 , and diluted with water. The concentrations of Np(VI) and Np(V) in the solutions prepared were determined complexometrically after reduction to the tetravalent state with hydroxylamine in 4 M HCl [7]. The Np(VII) concentration was determined spectrophotometrically using absorption maxima at 4123 413 and 6183 620 nm (extinction coefficients e 410 = 1400 and e 619 = 390 l mol 31 cm 31 [1]).…”

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Behavior of Np(VII, VI, V) in silicate solutions

et al. 2004

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Properties of Np(VII, VI, V) in silicate solutions were studied spectrophotometrically. In noncomplexing media, the Np(VII) cation transforms into the anionic species at pH 5.5!7.5. In the presence of carbonate ions, this rearrangement occurs at pH 10 !11.5, and in silicate solutions, at pH 10.5!12.0. These data show that Np(VII) cation forms complexes with carbonate and silicate ions, the latter being stronger. From the competitive reactions of Np(VI) complex formation with carbonate and silicate ions, the stability of NpO 2 SiO 3 complex was estimated (log > = 16.5) using the known stability constant of NpO 2 (CO 3 ) 3 4! . Complexation of Np(V) with SiO 3 2! ions was not detected by the methods used. It is known that in alkaline solutions Np(VII) exists as an anion NpO 4 (OH) 2 33 [133], and in acidic solutions, as a cation NpO 3 + [4] or Np(OH) 6 + [5]. The cationic form transforms into the anionic form in 1 M NaNO 3 or NaClO 4 at pH 5.537.5 [6]. In the presence of carbonate ions ([KHCO 3 ] + [K 2 CO 3 ] = 0.5 M), this transition occurs at pH 10 311.5. Thus, the range of the existence of the cationic Np(VII) form is extended by three pH units. Hence, we can conclude that Np(VII) cation forms a complex with carbonate ions [6]. There are no data on Np(VII) behavior in silicate solutions, in which both metasilicate SiO 3 23 and orthosilicate SiO 4 43 ions (and protonated species of the latter) can exist.In this work, the state of Np(VII) in silicate solutions was studied spectrophotometrically. In addition, complex formation of Np(VI) and Np(V) with silicate ions was studied. EXPERIMENTALChemically pure grade HClO 4 , ultrapure grade LiClO 4 and NaOH (the latter as a 17 M solution), analytically pure grade NaHCO 3 , recrystallzed pure grade NaClO 4 and chemically pure grade Na 2 CO 3 , and A grade Na 2 SiO 3 . 9H 2 O (Reakhim) were used. All solutions were prepared with double-distilled water and standardized by usual methods. The silicate solution was ozonized to oxidize traces of reducing agents and purged with purified air to remove the dissolved ozone.The 237 Np preparations were purified by anion exchange. The Np(IV) nitric acid solution was evaporated with HClO 4 until a white vapor appeared, and this procedure was repeated. The wet salts were dissolved in 0.01 M HClO 4 . Spectrophotometric analysis showed that neptunium was almost fully in the hexavalent state. A part of the Np(VI) solution was mixed with 4 M LiOH (final concentration of LiOH 0.7 M) or with 17 M NaOH and ozonized to obtain Np(VII). To another part of the Np(VI) solution, NaNO 2 was added, and the resulting Np(V) was precipitated with ammonia. After coagulation, the precipitate was centrifuged, washed with ice-cold double-distilled water, dissolved in the minimal amount of HClO 4 , and diluted with water. The concentrations of Np(VI) and Np(V) in the solutions prepared were determined complexometrically after reduction to the tetravalent state with hydroxylamine in 4 M HCl [7]. The Np(VII) concentration was determined spectrophotometricall...

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Behavior of Np(VII, VI, V) in silicate solutions

et al. 2004

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“…)· Since it is known that nitrous acid (nitrogen oxides) plays a leading role in the oxidation of Pu(III) and Np(IV) with nitric acid in TBP solutions [12][13] and in the oxidation of U(IV) in an aqueous HN0 3 solution [14], this is a potentially serious problem. Indeed, it was the varying concentration of HN0 2 that was used by the authors of reference [5] to explain the non-reproducibility of the induction period that they observed in their experiments on the oxidation of U(IV) in 20% TBP.…”

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confidence: 98%

“…Due to the rather slow rate of reaction at ambient temperatures, the kinetics were studied spectrophotometrically [5,19] In most cases the kinetic curves of the U(IV) oxidation showed an induction period ( Fig. 1) which was decreased as [HN0 3 ] increased.…”

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The Oxidation of U(IV) by Nitric Acid in 30% Tri-Butyl Phosphate Solutions

et al. 1999

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“…The oxidation states of neptunium in solutions prepared were monitored spectrophotometrically on a Shimadzu PC-3100 spectrophotometer (Japan). The neptunium concentration was determined complexometrically after the reduction to Np(IV) [3]. Na 2 CO 3 and NaHCO 3 were of chemically pure and analytically pure grade.…”

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Behavior of Np(VI) and Np(V) Ions in NaHCO3 Solutions Containing H2O2

et al. 2005

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The behavior of Np(VI) and Np(V) in NaHCO 3 and NaHCO 3 + Na 2 CO 3 solutions containing H 2 O 2 was studied spectrophotometrically. In 0.7531.0 M NaHCO 3 , hydrogen peroxide oxidizes Np(V) to Np(VI). The kinetics curves of Np(V) oxidation into Np(VI) have a complex shape and are characterized either by an induction period of up to tens of minutes or by a period of steady-state Np(VI) concentration, followed by an increase in the Np(VI) concentration. When Np(VI) initially exists in the solution, the induction period is lacking. The process character changes when the bicarbonate concentration decreases, or when Na 2 CO 3 is added. In 1.0 M Na 2 CO 3 , 0.5 M NaHCO 3 + 0.5 M Na 2 CO 3 , or 0.013 0.5 M NaHCO 3 , hydrogen peroxide completely reduces Np(VI) into Np(V). The probable mechanisms of this process were discussed. Accumulation of Np(VI) in NaHCO 3 solutions can be accounted for by assuming that Np(VI) itself participates in the transformations. Initially, the reaction of Np(VI) with H 2 O 2 yields the excited *Np(V) ion. Then it reacts with another H 2 O 2 molecule and forms a carbonate3peroxide complex. In the collision of the latter with unexcited Np(V), two electrons from two Np(V) ions are transferred onto the O 2 2! ligand with formation of two Np(VI) ions.It was found in [1] that, in the course of g-radiolysis of aerated or Ar-saturated NaHCO 3 solutions containing 2 0 10 34 M Np(V), neptunium(VI) is formed with the yield G Np(VI) of about 8 ions per 100 eV. This value exceeds the yield of the oxidant species, OH radicals (G OH = 2.9 particles per 100 eV [2]) and is close to the total yield of all primary products of water radiolysis, i.e., G OH + G e ! (aq) + G H + 2G H 2 O 2 .It follows from the data obtained that H 2 O 2 under these conditions is an oxidant with respect to Np(V). It was interesting to examine the behavior of H 2 O 2 not nascent but specially introduced into the solution. EXPERIMENTAL 237Np purified by ion exchange was used. The nitric acid solution of Np(IV) after passing through an ion-exchange column was twice evaporated with perchloric acid up to appearance of white fume. The dry residue of NpO 2 (ClO 4 ) 2 . aq was dissolved in 0.01 M HClO 4 , and NaNO 2 was added to a part of the solution obtained to convert Np(VI) into Np(V), which was then precipitated as hydroxide with aqueous ammonia. After coagulation, the NpO 2 OH precipitate was separated by centrifugation, washed twice with cold double-distilled water, and dissolved in a minimal amount of an HClO 4 solution. The oxidation states of neptunium in solutions prepared were monitored spectrophotometrically on a Shimadzu PC-3100 spectrophotometer (Japan). The neptunium concentration was determined complexometrically after the reduction to Np(IV) [3]. Na 2 CO 3 and NaHCO 3 were of chemically pure and analytically pure grade. Na 2 CO 3 was additionally purified by recrystallization from double-distilled water. Medicinal grade hydrogen peroxide stabilized with sodium dihydrogen phosphate was vacuum-distilled. The working solution...

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Investigation of the spent fuel element of the first atomic power station

Cited by 4 publications

References 0 publications

Behavior of Np(VII, VI, V) in silicate solutions

Behavior of Np(VII, VI, V) in silicate solutions

The Oxidation of U(IV) by Nitric Acid in 30% Tri-Butyl Phosphate Solutions

Behavior of Np(VI) and Np(V) Ions in NaHCO3 Solutions Containing H2O2

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