[en] Recently, chromium isotopes have been enriched using gas centrifuges that were developed by the United States Department of Energy for the purpose of enriching uranium in the fissionable isotope ²³⁵U. The process gas employed was chromyl-fluoride. The enrichment was carried out using a single gas centrifuge that was set up to emphasize the enrichment of the light isotope ⁵⁰Cr, which has a natural abundance of 4.35%. The highest enrichment tested to date is 21.4%. Higher values are possible with additional repasses. The heavy isotopes ⁵⁴Cr can be enriched instead of the ⁵⁰Cr with an adjustment to the machine flows. Currently, work is under way to refine the cost projections associated with feed production and conversion back to an oxide and to optimize the centrifuge separative performance. (orig.)

[en] Following the theory of relativity, in the presence of an ultrastrong magnetic field (UMF) and utilizing a nuclear shell model, we carry out an estimation of the neutrino energy loss (NEL) rates of nuclides ^53–60Cr, which occur by electron capture in magnetars. The results show that the NEL rates greatly increase when a UMF is present, and can even exceed nine orders of magnitude at relatively lower density and temperature (e.g. ρ₇ = 5.86, Y_e = 0.47, T₉ = 7.33) in the range from 10¹³ G to 10¹⁸ G. However, the increase in rates was no more than six orders of magnitude at relatively higher density and temperature (e.g. ρ₇ = 4.86 × 10⁸, Y_e = 0.39, T₉ = 14.35)

No abstract available

[en] A re-evaluation has been made of neutron and gamma production cross sections for reactions of neutrons with ⁵⁰,⁵²,⁵³,⁵⁴Cr and natural Cr. In addition, energy level schemes and Q values are presented. 97 references

[en] The United States depends entirely on foreign sources for the critical material, chromium, making it very vulnerable to supply disruptions. This vulnerability results because chromium is essential for the fabrication of corrosion-resisting steels and high-temperature, oxidation-resisting alloys in applications that are vital to the nation's technological well-being; because no substitutes are known for these materials in those applications; and because the known, substantial deposits of chromite ore are only in a few geographical locations that could become inaccessible to the United States as a result of political actions. The effectiveness of programs such as stockpiling, conservation, and research and development for substitutes to reduce the impact of disruption of imports of chromite and ferrochromium are discussed. Alternatives for decreasing chromium consumption also are identified for chromium-containing materials in the areas of design, processing, and substitution

[en] Early solar materials bear a variety of isotopic anomalies that reflect compositional differences deriving from distinct stellar nucleosynthetic processes. As shown in previous studies, the stepwise dissolution with increasing acid strengths of bulk rock carbonaceous chondrites liberates Cr with both excesses and deficits in ⁵³Cr and ⁵⁴Cr relative to the terrestrial standard. The magnitude of the ⁵⁴Cr variations within a meteorite decreases in the sequence CI1 > CR2 > CM2 > CV3 > CO3 > CK4 and correlates with the degree of metamorphism of each carbonaceous chondrite class. This study shows that the Tagish Lake meteorite presents the highest excesses in ⁵⁴Cr ever measured in a bulk silicate phase. According to this study, the Tagish Lake meteorite is composed of the least re-equilibrated material known at this time. The magnitude of ⁵⁴Cr variation decreases now in the following sequence: Tagish Lake (ungrouped CI2) > Orgueil (CI1) > Murchison (CM2) > Allende (CV2). Moreover, this study shows that excesses in ⁵³Cr relative to Earth can be interpreted as representing the extent of aqueous alteration on meteorite parent bodies. Finally, the high ⁵⁴Cr anomalies measured in this meteorite make Tagish Lake one of the major targets to decipher the host of these anomalies.

[en] The criterion for efficiency for separation of binary isotopic mixtures is the well-known value function. However, in the case of multi-isotope separation, this value function does not exist. In this paper the authors develop a criterion to define the efficiency for separation of multi-isotope mixtures. It is based o the concept of the match-abundance ratio cascade (MARC) originally introduced by De La Garza for a ternary isotope mixture. The criterion has the property that, when applied to binary mixtures, it is the same as the value function. This approach has demonstrated that for obtaining the optimal parameters of a single stage in the cascade it is necessary to minimize the linear combination of the inverse values of partial separative powers for all mixture components. A numerical example using this efficiency criterion is presented using the separation of chromium isotopes by a single gas centrifuge

[en] The effects of Cr³⁺ and (CrO₄)^2- on water cultured young wheat were investigated, making ⁵¹Cr-labelled Cr₂ (SO₄)₃ and Na₂ CrO₄ as the Cr sources. How they were absorbed into the roots, moved and changed their forms in the plant body were examined. Both Cr³⁺ and (CrO₄)^2- did not have any difference on dry weight, but (CrO₄)^2- showed higher absorption and moving ratios as compared with Cr³⁺. When (CrO₄)^2- in water extract was passed through cation exchange resin, almost all (CrO₄)^2- passed through the resin, and the ratio of the passed part from roots was larger than that from above-ground parts. When (CrO₄)^2- in water extract was separated by filter paper electrophoresis, migration to + direction from the origin was observed in both roots and above-ground parts. (Kobatake, H.)

[en] All individual phases of the ternary Cr-C-N system including stable and metastable ones can be deposited at low temperature by metalorganic chemical vapor deposition (MOCVD). These growth processes are mainly based on the use of bis(benzene)chromium as chromium source and various co-reactives. Then, from a good control of the reactive gas phase, it is possible to combine these MOCVD processes to grow in the same reactor protective coatings designed with a complex architecture based on polyphased, nanostructured or multilayer structure which exhibit enhanced properties. These deposition processes are described and the main features of the coatings are discussed

[en] The effect of Cr_O3 addition on the densification and grain growth of UO₂ pellets has been studied. The pellets were sintered at 1700 .deg. C for 4 hours in dry and wet hydrogen atmospheres. The densification and grain size of UO₂ pellets with the addition of Cr₂O₃ were affected by the oxygen potential of sintering atmospheres. The grain size of UO₂ pellets increases with the amount of Cr₂O₃ in all the sintering atmospheres. Maximum sintered density and grain size of UO₂ pellets with C₂O₃ were obtained under the condition that the ratio of H₂O to H₂ gas equals to 0.01 in the sintering atmosphere. Inhomogeneous microstructure was found in the UO₂ pellets sintered in dry hydrogen atmosphere. It is thought that the precipitated chromium which is reduced from chromium oxide gives rise to the inhomogeneous microstructure