Curium-242, alpha decay

ISOTOPES There are 23 isotopes of curium. All of them are man-made and radioactive. The most stable is curium-247, with a half-life of 1.56xl0+ years (156,600,000 years), which through alpha decay transmutates into plutonium-243. 

ISOTOPES There are a total of 21 isotopes of californium. None are found in nature and all are artificially produced and radioactive. Their half-lives range from 45 nanoseconds for californium-246 to 898 years for californium-251, which is its most stable isotope and which decays into curium-247 either though spontaneous fission or by alpha decay. 

All Mars rovers to date have carried alpha-particle X-ray spectrometer (APXS) instruments for chemical analyses of rocks and soils (see Fig. 13.16). The source consists of radioactive curium, which decays with a short half-life to produce a-particles, which then irradiate the sample. Secondary X-rays characteristic of specific elements are then released and measured by a silicon drift detector. The Mars Pathfinder APXS also measured the backscattered a-particles, for detection of light elements, but the Mars Exploration Rovers measured only the X-rays. 

Determine the identity of the unknown product of the alpha decay of curium-245 ... 

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. 

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.)... 

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. 

Radioactive decay of and Pu form Am and Am, which are also important and persistent sources of alpha radioactivity in discharge fuel. Another persistent americium radioisotope is 152-year Am, formed by neutron capture in Am. Its isomeric decay and the beta decay of its short-lived daughter result in 163-day Cm, which is the most intense source of alpha activity in discharged uranium fuel. Successive neutron captures lead to em, em, and Cm. Higher-mass curium nuclides are usually not important in power reactor fuel. 

The electrometallurgical recycle technology does not involve separation of plutonium. The plutonium product is inherently commingled together with minor actinides (i.e. americium, curium, and neptunium), uranium, and fission products. The minor actinides contribute substantial decay heat and contamination with alpha, beta, gamma, and neutron radiation emitters. The fresh fuel product is highly radioactive, which complicates thefts and diversion. 

Alpha-neutron reactions, primarily with 018 in the uranium oxide fuel, except with the alpha coming from the decay of curium. 

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