The effect of ionizing radiation on uranophane

Utsunomiya, Satoshi; Wang, Lu Min; Douglas, Matthew; Clark, Sue B.; Ewing, Rodney C.

doi:10.2138/am-2003-0119

Cited by 16 publications

(14 citation statements)

References 31 publications

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“…In these compounds I−O bond distances of IO 3 are from 1.772 Å to 1.858 Å, and the average value is 1.809 Å [29][30][31][32]. IO 4 structure is observed in one compound, Ag 4 (UO 2 ) 4 (IO 3 ) 2 (IO 4 ) 2 O 2 , in which the average I−O bond distance is 1.909 Å and IO 4 sharing [25] and after Burns [26]. two oxygen with UO 5 polyhedra [29].…”

Section: Incorporation Mechanism Of Iodine Into Uranophanementioning

confidence: 92%

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Incorporation of iodine into uranophane formed during the corrosion of spent nuclear fuel

Wu¹,

Chen²,

Kang³

et al. 2009

Radiochimica Acta

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In order to evaluate the potential incorporation of 129 I into uranyl phases that would form during oxidative alteration of spent nuclear fuel, uranophane was synthesized under mild hydothermal conditions of 165 • C in the presence of iodide, iodate and periodate, respectively. The precipitates were examined and analyzed using powder X-ray diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscope (SEM) equipped with an energy-dispersive X-ray spectroscopy (EDS). The results indicate that significant amount iodine can be incorporated into the structure of uranophane in the form of IO 4 − , and less in the form of IO 3 − . Crystallo-chemical analyses suggest that the incorporation mechanisms would be the substitution of iodate and periodate for SiO 4 tetrahedron in the sheet.

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Section: Incorporation Mechanism Of Iodine Into Uranophanementioning

confidence: 92%

“…7, uranophane consists of alternating stacks of U−Si−O sheets with interlayer cations bonded to water molecules or hydroxyl in the α-direction [25]. The sheet contains chains of edge-sharing UO 5 polyhedra that are cross-linked via SiO 4 tetrahedra [13] by sharing two oxygen atoms.…”

Section: Incorporation Mechanism Of Iodine Into Uranophanementioning

confidence: 99%

Incorporation of iodine into uranophane formed during the corrosion of spent nuclear fuel

Wu¹,

Chen²,

Kang³

et al. 2009

Radiochimica Acta

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“…Radiation can induce the conversion of crystalline U silicate solids to amorphous U silicate solids, which may be overlooked in XRD studies. 74 However, the amorphous U phases were not characterized in this system.…”

Section: Clarkeite Association With Uranyl Silicates In Natural Envirmentioning

confidence: 93%

Characterization of Uranium in Archived 2H Evaporator Scale

Duff¹

2004

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“…The secondary end product from such oxidizing and radiation environment will be a variety of uranyl oxyhydroxides, silicates and other uranium compounds. 17 Although only a few literature citings are available dealing with the effects of ionizing radiation on uranyl silicate phases 18 , it is quite obvious that uranyl silicate structures become disordered in the presence of very high ionizing radiation fields. For examples, studies performed with uranophane exposed to high ionizing radiation shows that there is gradual disordering or amorphization (i.e., conversion from crystalline to amorphous) of the entire uranyl sheet silicate structure at room temperature.…”

Section: H 2 O)mentioning

confidence: 99%

“…Amorphization dose for uranophane at room temperature has been reported to be 1.3 x 10 12 rad. 18 Based on an SRS evaporator maintenance cycle of three months on the average, and an average evaporator radiation dose rate of 1.30 E+3 rad per hour (based on the predominant radionuclide, Cs-137 at one curie per liter), one can estimate the maximum ionizing radiation minerals formed in the evaporator would be exposed to. This value is approximately 2.8 E+06 rad.…”

Section: H 2 O)mentioning

confidence: 99%

Conditions Conducive to Forming Crystalline Uranyl Silicates in SRS Evaporators

Oji¹

2004

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SUMMARYThe laboratory conditions (temperature range of 80-150º C, hydrothermal and oxidizing environment, soluble uranium and silica, atmospheric and pH conditions) under which synthetic uranyl silicates are made are almost identical to SRS evaporator conditions, with the exception of differences in sodium ion (Na + ) concentration. Synthetic uranyl silicates have been made only under low Na + concentration (<0.02 M), while attempts to synthesize uranyl silicates in this study in the presence of high Na + concentration (5.6 M), which are typical of SRS evaporators have proved unfruitful.In the presence of soluble silica and uranyl ion, uranyl silicates (sodium weeksite, sodium boltwoodite and uranophane) have been synthesized at moderately low to high pH in temperature ranges of 80-150 ºC and at less than 0.02 M Na + ion concentration in the reaction mixtures. However, in the presence of high Na + concentration the main product distribution for the same soluble silica-uranium reaction mixture shifts towards the formation of clarkeite (Na[(UO 2 )O(OH)](H 2 O) 0-1 ), a hydrated sodium uranate and not towards the formation of uranyl silicates.There is a threshold Na + concentration requirement above which uranyl silicates are not formed under laboratory conditions that are quite similar to SRS evaporator conditions. This threshold Na + concentration, which is yet to be determined, may be influenced by the sodium-to-uranium ratio in a reaction mixture.Therefore, based on the synthesis information presented in this study the following conclusions are made:• Crystalline uranyl silicates are readily formed in the presence of dissolved uranium and silica.• The presence of high Na + concentration in a reaction mixture of dissolved uranium and silica inhibits the formation of crystalline uranyl silicates.• The reaction path way favors the formation of hydrated sodium uranates over the uranyl silicates in a reaction mixture with high Na + concentration.• Crystalline uranyl silicate minerals are not easily produced under SRS evaporator conditions because of high Na + concentration in the evaporators and in the evaporator feed tanks.• The principal uranium minerals which could be produced under evaporator conditions are sodium uranium minerals or clarkeite, which could also exist in the dehydrated form called sodium uranate.

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The effect of ionizing radiation on uranophane

Cited by 16 publications

References 31 publications

Incorporation of iodine into uranophane formed during the corrosion of spent nuclear fuel

Incorporation of iodine into uranophane formed during the corrosion of spent nuclear fuel

Characterization of Uranium in Archived 2H Evaporator Scale

Conditions Conducive to Forming Crystalline Uranyl Silicates in SRS Evaporators

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