Magnetic Isotope Effect in the Uranium Isotopes Separation

MAGNETIC ISOTOPE EFFECT IN THE URANIUM ISOTOPES SEPARATION

I. V. Zhyganiuk Institute for Safety Problems of Nuclear Power Plants, Nat. Acad. of Sci. of Ukraine 36a, Kirova str., Chornobyl 07270, Ukraine* Institute of Artificial Intelligence Problems, Nat. Acad. of Sci. of Ukraine and 40, Academician Glushkov Ave., Kyiv 03680, Ukraine

A. V. Zubko and O. B. Lysenko Institute of Environmental Geochemistry, Nat. Acad. of Sci. of Ukraine and 34a, Palladin Ave., Kyiv 03142, Ukraine

When uranyl nitrate is photolysed in the water solution, light isotope 235U is separated from isotope 238U ; an enrichment factor 퐾 = 1.04 . The initial samples were depleted by a light isotope of uranium 235U (degree 훽 = 0.00455). Regenerated uranyl nitrate was enriched by an isotope of uranium 235U (degree 훼 = 0.00464). Uranium tetrafluoride was depleted by an isotope of uranium 235U (degree 훽 = 0.00446). Uranium isotopes are separated by the magnetic isotope effect (MIE) in uranyl nitrate photoreduction.

Keywords: uranium isotopes, magnetic isotope effect.

In memory of Academician Emlen Sobotovich, an pairs induced by photolysis in heavy water solu- outstanding scientist tions; authors investigated MIE in these chemical reactions. These results are presented in this manuscript. For more details about MIE, I. INTRODUCTION see [2–10]. These effects and processes have been used for a new chemical separation of ura- The results of a theoretical investiga- nium isotopes. tion of interactions between electron magnetic

arXiv:1802.02530v1 [physics.chem-ph] 7 Feb 2018 moments and nuclear–magnetic moment pub- lished in work [1] in 1975; this work was II. EXPERIMENTAL the first to show that existence to the MIE. In the photoinduced reaction uranyl ni- Buchachenko A. and his group originally discov- trate was regenerated in the р-methoxyphenol ered the MIE in 1976 [2]. and heavy water solution. The initial samples Uranyl nitrate ions complexes are being of uranyl nitrate were depleted by a light iso- regenerated uranyl-ion and nitrate-ion radicals tope of uranium 235U (degree 훽 = 0.00455).

*Electronic address: [email protected] In work [9], the initial samples of uranyl ni- 2

trate were enriched by an isotope of uranium → hν 235U (degree 훼 = 0.112). Our experiments

235 • + • 235 were conducted in solutions of following con- [ UO2 OAr ] T→S UO2 (NO3 ) 2 −3 centration: UO2(NO3)2 — 1.6 · 10 mol/l, [р-

−2 → methoxyphenol] — 5.0·10 , NH4F — 1.0 mol/l, hν

238 • + H2SO4 — 0.5 mol/l in heavy water. UO •• 2 % [238 UO+ OAr ] → Depleted uranium dioxide was dissolved in 2 238 UF4 6 concentrated nitric acid; this solution was evap- orated; we had received uranyl nitrate in dry Figure 1: Scheme of the processes were being oc- residue. Solutions were prepared and mixed; curred in the photolysis of uranyl; in this scheme introduce next denotation: unpaired electron (·), they were placed in a quartz vessel. Next replaced phenol (Ar), triplet state (T), singlet state step, the solutions were deoxygenated flushing + (S), uranoyl (UO2 ) with argon; the quartz vessel was hermetically sealed. III. RESULTS AND THEIR Further, the solutions had been irradiat- DISCUSSION ing by an ultraviolet lamp (characteristics of the lamp: Δ휆 = 350 ÷ 450 푛푚, 푃 = 61푊 ), A triplet-singlet conversion had been fin- ished in radical pair before the uranyl regen- until a suspension with UF4 was formed in solutions. Next, the irradiation had been stop- erated to the uranyl nitrate; it is presented by Fig. 1. The triplet-singlet conversion has been ping, before the precipitate with UF4 didn’t completed formation. Then, the suspension occurred because electrons spines precessed in magnetic field of uranium nucleus 235U. An with UF4 was being decanted in the centrifuge. + Here, we had separated uranium tetrafluoride uranoyl UO2 is a singly charged complex of in the precipitate. Uranium isotope ratios were uranyl-ion with unpaired electron. At this stage 2+ being measured in the uranium tetrafluoride of reaction, an uranyl-ion UO2 is being en- 235 + and the uranyl nitrate. These results were be- riched by isotope U; the uranoyl UO2 is be- 235 ing obtained by MI-1201 mass spectrometer (at ing depleted by isotope U. Uranoyl formed State Institution ”Institute of Environmental the insoluble precipitate with uranium tetraflu-

Geochemistry, National Academy of Sciences of oride UF4 in a disproportionation reaction. 235 Ukraine”). The degree of enriched 훼 in isotope U (the degree of depleted (훽)) or isotope ratio in the sample determined to the formula

휈(235U) 훼 = , (1) 휈(235U) + 휈(238U) 3 where is 휈(235U) isotope substance amount factor 퐾(1) to have the value of 1.02. In present 235U ; is 휈(238U) isotope substance amount work, the enrichment factor 퐾(1) to have the 238U. larger value 1.04 (see formula (2)) than value Since, the averaged values degree of en- from paper [9]. riched or the isotope ratio: 1) the initial The enrichment factor related the sepa- (0) uranyl nitrate sample 훽 2+ = 0.00454, 2) ura- rated methods of uranium isotopes are shown UO2 nium tetrafluoride precipitate 훽UF4 = 0.00446, in papers [10, 11]. The Steenbeck’s centrifu- and 3) regenerated uranyl nitrate 훼 2+ = gal isotopes separations methods occupied a UO2 0.00464. Therefore, in this work isotope sep- first place in accordance with efficiency. But, aration 235U238U enrichment factor equal: the MIE method of isotopes separation takes the second place. Unfortunately, for implement 훼UO2+ (1 − 훼UO2+ ) 퐾(1) = 2 2 = 1.040, (2) 훽UF4 (1 − 훽UF4 ) centrifugal isotopes separation method we nec- (1) where 퐾 is the enrichment factor, and 훼 2+ essary have high expenses for factory building, UO2 is the degree of enriched regenerated uranyl ni- and for high technical complexity of construc- trate, 훽UF4 is the degree of depleted precipitate tion. Industrial method of isotopes separation with UF4 . by the gaseous diffusion is being implemented Isotopic composition of regenerated uranyl in the big industrial cluster includes plant and nitrate and uranium tetrafluoride was measured a power station. The building of such industrial by mass spectrometer. The enrichment factor cluster is a very expensive process. Therefore, of uranyl nitrate photolysed with MIE equal the industrial method of isotopes separation by 1.04, see formula (2). the gaseous diffusion is a difficult technical and The experimental evidence of the degrees economical problem. An initial compound is of enriched 훼 with isotope 235U from the regen- uranium hexafluoride for the centrifugal iso- erated uranyl nitrate showed on Fig. 2. Here, topes separation methods and for the method we see 16 dots under the line corresponding of isotopes separation by the gaseous diffusion. (0) to degree 훽 2+ = 0.00454, where uranyl ni- In the period of terrorist danger, the plant with UO2 trate depleted with isotope 235U. Next, we gaseous toxic uranium hexafluoride is a critical see 8 dots allocated in a vicinity of the line infrastructure object. corresponding to degree of the initial sample For the last 40 years, laser uranium sepa- (0) 훽 2+ = 0.00454. In the 41 experiments uranyl rations have been investigated for the industrial UO2 nitrate was enriched with isotope 235U, as we processes [10]. Unfortunately, these investiga- see 41 dots above the line corresponding to de- tions haven’t resulted in the commercial ura- (0) gree 훽 2+ = 0.00454. nium enrichment technology. UO2 It follows from work [9] that enrichment 4

Figure 2: Values of the degree of enriched 훼 in isotope 235U from the 65 experiments (for each of value showed confidence interval with 휀 = ±0.00035): degree of depleted of the initial uranyl nitrate sample 훽 = 0.00454 (1), and degrees of enriched (see formula (1)) regenerated uranyl nitrate (2).

Next, from papers [11, 12] follows that the studying. Authors are studying kinetic prop- MIE method of uranium isotopes separation erties ions, and stability of hydrate complexes has a maximum enrichment factor except for with ions in water solutions. centrifugal isotopes separation methods. The authors cordially thank Academician As of now, authors of the presented article of the NAS of Ukraine V. G. Baryakhtar for his are studying process of the uranium isotopes permanent attention and numerous discussions. separation in the uranium oxides from natural We are also grateful to our coauthors Cor- samples. These processes of uranium isotopes responding Member of the NAS of Ukraine separation have been induced MIE. R. Ya. Belevtsev, and Professor V. V. Dolin. We The isotope separation 235U from 238U in thank also Professor N. P. Malomuzh for the the photoinduced reaction uranyl nitrate with fruitful discussions of the results obtained. MIE in the water solutions demand further

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