Curium isotope

A. M. Friedman, H. Diamond and J. R. Huizenga Curium isotopes 246 and 247 from pile-irradiated Plutonium. Physic. Rev. 94, 974 (1954). 

There is no natural curium on Earth. All of its isotopes are man-made and artificially produced through nuclear reactions with other elements. The curium isotope Cm-242 was first produced by bombarding plutonium-239 with helium nuclei (alpha particles), which contributed neutrons that changed Pu to g Cm. 

Symbol Cm atomic number 96 atomic weight 247 a radioactive transuranium actinide series element electron configuration [Rn]5/ 6di7s2 most stable valence state +3 most stable isotope Cm-247. Curium isotopes, half-hves and decay modes are ... 

It may be synthesized by several other methods. Curium isotopes of lower mass numbers may be obtained by charged particle bombardments of plutonium-239 ... 

The element was discovered independently by several groups nearly simultaneously. In 1958, Ghiorso, Sikkeland, Walton, and Seaborg at Berkeley, California, synthesized an isotope of this new element by bombardment of a mixture of curium isotopes containing 95% Cm-244 and 4.5% Cm-246 with carbon-12 ions. This new element was named nobelium in honor of Alfred Nobel, discoverer of dynamite. 

Optimization of Irradiation Times. By far the greatest usage of the calculational model has been to study the optimization of irradiation times. This is a multi-dimensional problem of great complexity which has as its motivation the proper utilization of very expensive facilties and a very valuable inventory of intermediate products, mainly the mixtures of curium isotopes. The problem does not lend itself to a complete solution however, various simplifying approximations can be applied to the problem to explore the interacting parameters. 

A research and development program on the recovery and purification of potentially useful by-product actinides from the nuclear fuel cycle was carried out some years ago in the Federal Republic of Germany as part of the "Actinides Project" (PACT). In the course of this program, procedures for the recovery of neptunium, americium and curium isotopes from power reactor fuels, as well as procedures for the processing of irradiated targets of neptunium and americium to produce heat-source isotopes, have been developed. The history of the PACT Program has been reviewed previously (1). Most of the PACT activities were terminated towards the end of 1973, when it became evident that no major commercial market for the products in question was likely to develop. 

Americium and curium isotopes formed during irradiation of nuclear reactor fuels are diverted into the high-level waste (HLW) stream during fuel reprocessing. The HLW is thus the biggest... 

Californium-252 production was especially challenging, as it involved the sequential capture of 14 neutrons along with the intermediate separation and fabrication of two intermediate targets (americium and curium isotopes) when starting with Pu-23 9.27 This production campaign lasted ten years, produced about 10 g of Cf-252, and then was terminated. The product was evaluated as a neutron source but had insufficient value to justify continuing production. 

Six long-lived radionuclides beyond uranium exist which have half-lives greater than 100 ka ( Np, Np, Pu, Pu and Cm). The first two are natural by-products of the nuclear industry. Nuclear-weapons tests will generate the plutonium and curium isotopes although attempts have been made to detect pre-solar system Pu in ores (Hoffman et al., 1971) or Pu from more recent supernova debris. The detection of these isotopes is still in the development stage. Unlike the natural elements, isobaric... 

The curium isotope with the longest half life is curium-247. Its half life is 15.6 million years. The half life of a radioactive element is the time it takes for half of a sample of the element to break down. After about 15.6 million years, only 0.5 grams of the isotope would remain from a one-gram sample produced today. The other 0.5 gram would have changed into another element. 

The americium and curium isotopes formed during irradiation of nuclear reactor fuels are diverted into the high-level waste (HLW) stream during fuel reprocessing. The HLW is thus the biggest potential source for these elements, and R+D activities to develop a process for the recovery of Am and Cm from HLW were started in 1967. A major condition was that the process to be developed must not essentially increase the waste amount to be processed further, must not use strongly corrosive reagents, and must be compatible with the final waste solidification procedure. 

Step 1. The mass number of the curium isotope is 245. Therefore the sum of the mass numbers of the products must also be 245, and must have a mass number of 241. 

Sec. 5.1 under Am. Repeated irradiation of the Pu and Am and extraction of Cm yields as much as 80 g Cm per kilogram of initial Pu [F2]. Further kradiation of the Cm yields the higher-mass curium isotopes and the transcurium elements. 

Cm. The isotope Cm, with a half-life of 5500 years, is a member of the long-lived group of alpha-emitting curium isotopes. It is produced by neutron capture in Cm. 

Cm. The isotope Cm, with a half-life of 350 days, is the highest-mass curium isotope produced in appreciable quantities in the kradiation of Cm. Very pure Cm is now being produced by tiie alpha decay of Cf, which is the principal transcurium isotope produced in the long-term neutron irradiation of plutonium, americium, curium, and berkelium. Cf decays with a half-life of 2.65 years, 3 percent by spontaneous fission and 97 percent by alpha emission. 

However the problem of curium isotopes utilization stand over because the fuel fabrication (even we add a small amount of curium) process is very awkward due to high activity of these isotopes (mainly Cm and... 

The transmutation of curium in reactors poses yet another set of problems compared with neptunium and americium because the curium isotopes have both shorter half-lives and higher spontaneous fission branches. In spent fuel, (Tm = 163 d) is by mass about 100 times... 

Curium is extracted and transported for 100-150-year cooling in the repository. After the cooling, all curium isotopes (except curium-245) are transformed into the plutonium isotopes. This isotopic mixture is then transported back to the reactor for further burning ... 

When reprocessing SNF, it is assumed that the extracted fission products first are vitrified and then, after necessary cooling, are enclosed in special containers providing a multi-barrier shielding and transported to be finally disposed in deep geological formations. Minor actinides (except for curium) are not separated from plutonium and are used in the reactor as a fuel component. Curium is extracted and transported to the temporary repository for 100-150-year cooling. Upon being cooled, all curium isotopes (except for curium-245) are transformed into plutonium isotopes. Then this isotopic mixture is used to produce new fuel for the reactor. 

The first curium isotope, Cm, was prepared by Seaborg, James, and Ghiorso in mid-1944 by cyclotron a bombardment of and was identified by its characteristic a radiation [9]. Werner and Perlman separated the first weighable quantity of curium (40 ng of impure Cm oxide), which was prepared by prolonged neutron irradiation of Am [10]. 

Properties of the known curium isotopes, which range in mass from 238 to 251, are summarized in Table 9.1. Electron binding energies, x-ray spectra, and L-shell fluorescence data for curium are available, as well as both a and spontaneous fission data [11-13]. Three isotopes ( Cm, Cm, and Cm) are available in quantities sufficient for chemical study. Macroscopic studies with Cm and Cm are complicated by the high a activities of these isotopes (half-lives of 163 days and 18.11 years, respectively). The isotope Cm is desirable for chemical studies (half-life 3.40 x 10 years). Approximately 100 mg of are... 

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