Curium results

C22-0054. Identify the compound nucleus and final product resulting from each of the following nuclear reactions (a) carbon-12 captures a neutron and then emits a proton (b) the nuclide with eight protons and eight neutrons captures an a particle and emits a y ray and (c) curium-247 is bombarded with boron-11, and the product loses three neutrons. 

The nuclear reaction involving the bombardment of curium with calcium that directly produced element 116 occurred on December 6, 2000, at the Joint Institute for Nuclear Research in Dubna, Russia, in cooperation with personnel of the Lawrence-Livermore Berkeley Group. This nuclear reaction resulted in the production of a few atoms of the isotope ununhexium-292, which has a half-life of 0.6 milliseconds and emits four neutrons. Uuh-292 is also the most stable isotope of element 116 as it continues to decay into elements with Z numbers of 114, 112, 110, 108, and 106, plus emitting four alpha particles for each transmutation. (Z numbers are the number of protons in the nuclei of atoms.)... 

This, in turn is produced by successive slow neutron irradiation of curium-244 Californium-254 may be produced by thermonuclear explosion resulting in the reaction of uranium-238 with intense neutron flux followed by a sequence of p- decays (Cunningham, B. B. 1968. In Encyclopedia of Chemical Elements, ed. Clifford A. Hampel, New York Reinhold Book Co.)... 

The heavier isotopes of the element may result from rapid neutron capture process caused by intense neutron fluxes from thermonuclear explosions, followed by a series of p decay (Cunningham, B.D. 1968. Curium. In Encyclopedia of Chemical Elements, ed. C. A. Hampel, pp. 173-177. New York Reinhold Book Corp.)... 

Recent Results for Curium Metal Under Pressure. 125... 

The structural sequence dhcp — ccp was also expected to occur in the next element, curium. But the ccp phase was not observed under pressure. In contrast, the simple hexagonal close-packed (hep) and, at still higher pressure, an as yet undetermined structure is formed. If these results are confirmed by further study, curium structures will have to be considered as another intermediate stage between the lighter and the heavier actinides. ... 

The Mars Pathfinder rover carried an Alpha Proton X-ray Spectrometer (APXS), and the two Mars Exploration Rovers (MER - Spirit and Opportunity) carried Alpha Particle X-ray Spectrometers (also called APXS, but in this case more precise versions of the Pathfinder instrument, though without the ability to monitor protons for light element analyses). These instruments contained radioactive curium sources (Fig. 13.16) whose decay produced a-particles, which irradiated target rocks and soils. The resulting characteristic X-rays provided measurements of major and minor element abundances. The MER rovers also carried Mossbauer spectrometers, which yielded information on iron oxidation state. 

Especially interesting in a discussion of radionuclide speciation is the behaviour of the transuranium elements neptunium, plutonium, americium and curium. These form part of the actinide series of elements which resemble the lanthanides in that electrons are progressively added to the 5f instead of the 4f orbital electron shell. The effective shielding of these 5f electrons is less than for the 4f electrons of the lanthanides and the differences in energy between adjacent shells is also smaller, with the result that the actinide elements tend to display more complex chemical properties than the lanthanides, especially in relation to their oxidation-reduction behaviour (Bagnall, 1972). The effect is especially noticeable in the case of uranium, neptunium and plutonium, the last of which has the unique feature that four oxidation states Pum, Pu, Puv and Pu are... 

The berkelium monopnictides have been prepared on the multimicrogram scale by direct combination of the elements (138). In all cases, the lattice constants of the NaCl-type cubic structures were smaller than those of the corresponding curium monopnictides but comparable to those of the corresponding terbium compounds. This supports the semimetallic classification for these compounds. One additional report of BkN has appeared (139). The lattice parameter derived from the sample exhibiting a single phase was 0.5010 0.0004 nm, whereas that extracted from the mixed-phase sample of BkN resulting from incomplete conversion of a hydride was 0.4948 0.0003 nm. Clearly, additional samples of BkN should be prepared to establish more firmly its lattice constant. 

The production and oxide characterization data for a series of curium-americium oxide production runs are presented in Table I. The table includes the composite feed analyses, the product data for each run, and a summary of the product data. Totals and averages are presented to indicate performance even though the products are not usually combined. Approximately 93.7% of the feed material was converted into product. The normal losses of actinides from the product are the result of oxide particles that stick to the product handling equipment. These are not actual process losses because they are eventually returned to rework. 

Wallmann 49) has prepared C-type Cm203 a = 11.01 0.01) by igniting curium nitrate on a platinum plate in air (this yields a black intermediate oxide), followed by reduction with purifled hydrogen at temperatures from 600° to 850°C. The C-type sesquioxide transforms spontaneously at room temperature in a few days to the hexagonal A-type sesquioxide a = 3.80 db 0.02A., c = 6.00 0.03A.), presumably a result of radiation effects. 

Actinides in the environment can be classified into two groups (i) the uranium and thorium series of radionuclides in the natural environment and (ii) neptunium, plutonium, americium and curium which are formed in a nuclear reactor during the neutron bombardment of uranium through a series of neutron capture and radioactive decay reactions. Transuranics thus produced have been spread widely in the atmosphere, geosphere and aquatic environment on the earth, as a result of nuclear bomb tests in the atmosphere, and accidental release from nuclear facilities (Sakanoue, 1987). Most of these radionuclide inventories have deposited in the northern hemisphere following the tests conducted by the United States and the Soviet Union. 

This, too, is an a-emitter with a half-life of 2.25 x 10 years and, unlike the highly active jS-emitter gNp with a half-life of only 2.3 days, is particularly suitable for chemical work. Curium and americium also appear as the result of (n,y) reactions involving plutonium ... 

Only five transuranic elements exist or are anticipated to be produced in amounts which could lead to significant environmental concentrations. These are neptunium (Np), plutonium (Pu), americium (Am), curium (Cm), and californium (Cf). Of these five, only two, plutonium and americium, have been detected and measured already in the marine environment as a result of global fallout of nuclear testing debris. The procedures described below were developed specifically to measure plutonium and americium. However, as will be expanded later, the techniques for measuring americium are also able to detect curium and californium should they be present in significant amounts in the future. 

Fig. 14.4), it is best shown by the radii of the -1-3 cations (Fig. 14.5). There are two noticeable dilTerenccs between the two series of ions (1) although the actinide contraction initially parallels that of the lanthanides, the elements from curium on are smaller than might be expected, probably resulting from poorer shielding by 5/ electrons in these elements (2) the lanthanide curve consists of two very shallow arcs with a discontinuity at the spherically symmetrical Gd " (4/ ) ion. A similar discontinuity is not clearly. seen at... 

Clinical management can potentially reduce the effects of plutonium intake, although the effectiveness can be highly variable. Administration of the calcium salt of diethylenetriaminepentaacetic acid (DTPA) can accelerate removal of soluble forms of plutonium from body fluids and recent deposits. It is unable to remove intracellular deposits or activity buried in bone and must therefore be administered as soon as possible after an intake. In a review of 18 patients exposed to plutonium, americium, or curium, the US Food and Drug Administration concluded that administration of 1 g Ca-DTPA in 5 ml sterile aqueous solution, either by intravenous injection or as a nebulized inhalation dose, increased the rate of radioactivity elimination in urine by an average of 39-fold. Daily maintenance doses of Zn-DTPA resulted in continued elimination of radioactivity. 

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