Fission betas

Intramolecular formation of a cation diradical can lead to cyclization or to fission beta to the site of charge density, eq. 66 (199) ... 

If a neutron penetrated a uranium nucleus, for example, the result might be fission. But if the neutron happened to be traveling at the appropriate energy when it penetrated—somewhere aroimd 25 eV—the nucleus would probably capture it without fissioning. Beta decay would follow, increasing the nuclear charge by one unit the result should be a new, as-yet-unnamed transuranic element of atomic number 93. That was one of Plac-zek s points. It would prove in time to be crucial. 

The principal radioactive decay processes are alpha decay, beta decay, gamma emission, and spontaneous fission. Beta decay can occur through the emission of an electron (fi decay) or a positron (fi decay) from the nucleus. Closely related to positron emission is orbital electron capture. 

A D—T fusion reactor is expected to have a tritium inventory of a few kilograms. Tritium is a relatively short-Hved (12.36 year half-life) and benign (beta emitter) radioactive material, and represents a radiological ha2ard many orders of magnitude less than does the fuel inventory in a fission reactor. Clearly, however, fusion reactors must be designed to preclude the accidental release of tritium or any other volatile radioactive material. There is no need to have fissile materials present in a fusion reactor, and relatively simple inspection techniques should suffice to prevent any clandestine breeding of fissile materials, eg, for potential weapons diversion. 

An isopropyl carbocation cannot experience a beta fission (no C-C bond beta to the carbon with the positive charge).It may either abstract a hydride ion from another hydrocarbon, yielding propane, or revert back to propene by eliminating a proton. This could explain the relatively higher yield of propene from catalytic cracking units than from thermal cracking units. 

When a uranium-235 atom undergoes fission, it splits into two unequal fragments and a number of neutrons and beta particles. The fission process is complicated by the fact that different uranium-235 atoms split up in many different ways. For example, while one atom of 292U is splitting to give isotopes of rubidium (Z = 37) and cesium (Z = 55), another may break up to give isotopes of bromine (Z = 35) and lanthanum (Z = 57), while still another atom yields isotopes of zinc (Z = 30) and samarium (Z = 62) ... 

Consider file fission reaction in which U-235 is bombarded by neutrons. The products of the bombardment are rubidium-89, cerium-144, beta particles, and more neutrons. 

Graessley J.H. Zufall, Fifth Quarterly Progress Report On Fission Product Applications Using Gaseous Beta Sources , USAEC Contract AT(30-l)-2343, Task II, Air Redn Co, Murray Hill, NJ (I960) 6)J.H. Wotiz, et al, A Novel... 

Major limitations in fission product decontamination will require tests with mixer-settlers. However, we anticipate from the distribution ratio measurements that Tc, Ru, and Pd will limit the overall decontamination from beta activity (other than from lanthanides). ... 

A possible alternative mechanism for the formation of fragment alkyl ions comes immediately to mind—namely, beta fission of the Ci8 ion formed in Reactions 6 and 7 to form a smaller alkyl ion and an olefin. Thus we write as a typical example ... 

This reaction exemplifies the important process of methyl removal, which becomes even more significant in the case of multiply branched paraffins. The rather large exothermicity of Reaction 11 results from the fact that a secondary carbonium ion is formed. The beta fission process can be illustrated using reactions in 8-ra-hexylpentadecane (compound 2) as an example. Table II shows that the ions formed by C-C fission at a branch point (Ci4+, m/e = 197 and Ci5+, m/e = 211) have intensities appreciably larger than the other alkyl ions in the same region... 

Note that in contrast with normal paraffins (Equation 10), beta fission at the branch point is exothermic, and the reaction is energetically allowed. A similar exothermic reaction can be written using C2H5 + as the reactant ion, and two other reactions equivalent to Reaction 12 can be written—namely, those with the charge in the initially formed C2i+ ion on the other two branches of the molecule. One of these other reactions will also produce a Ci4 + ion, but the other will produce a Ci5 + ion. 

MW + 1 ion), and this reaction is 35-40 kcal./mole exothermic. We might expect that the rate for this reaction would be appreciably greater than the rate for primary H abstraction, and we consequently postulate that primary H abstraction to yield MW — 1 ions will not occur to any significant extent. The other process we must consider is a simple extension of Reaction 12—namely, beta fission at a branch point. However, we now wish to consider the case where the branch point is a quaternary carbon. As a typical example ... 

In effect we postulate that the olefin ion is formed by a 1-3 hydride ion shift accompanied by a beta homolytic bond fission. The fact that olefin ions are formed only at branch points (except methyl branch points) could be explained on an energetic basis if it were not for the contrary fact that the over-all energetics are highly unfavorable. Thus in Reaction 20 we see that a disubstituted olefin ion is formed, and this will be true for any branch other than a methyl branch. Thus ... 

Strontium-90 is a fission product of uranium, which is used in permanent nuclear batteries as an energy-rich beta emitter. 

Gas-filled detectors are used, for the most part, to measure alpha and beta particles, neutrons, and gamma rays. The detectors operate in the ionization, proportional, and G-M regions with an arrangement most sensitive to the type of radiation being measured. Neutron detectors utilize ionization chambers or proportional counters of appropriate design. Compensated ion chambers, BF3 counters, fission counters, and proton recoil counters are examples of neutron detectors. 

McClellan, R. O., Barnes, J. E., Boecker, B. B., Cuddihy, R. G., Hobbs, C. H., Jones, R. K. and Redman, H. C. (1970a). Some observations on the toxicity of beta-emitting radionuclides inhaled in fused clay particles, page 197 in Fission Product Inhalation Program Annual Report 1969-1970, Report No. LF-43 (Lovelace Foundation, Albuquerque, New Mexico). 

Figure 12.5 illustrates the basic components of the Purex process three purification cycles for both uranium and plutonium are shown. High levels of beta and gamma radioactivity are present only in the first cycle, in which 99.9% of the fission products are separated. The other two cycles, based upon the same chemical reactions as the first cycle, obtain additional decontamination and overall purity of the uranium and plutonium products. 

Uranium is the fourth metal in the actinide series. It looks much like other actinide metallic elements with a silvery luster. It is comparatively heavy, yet malleable and ductile. It reacts with air to form an oxide of uranium. It is one of the few naturally radioactive elements that is fissionable, meaning that as it absorbs more neutrons, it splits into a series of other lighter elements (lower atomic weights) through a process of alpha decay and beta emission that is known as the uranium decay series, as follows U-238—> Th-234—>Pa-234—>U-234—> Th-230 Ra-226 Rn-222 Po-218 Pb-2l4 At-218 Bi-2l4 Rn-218 Po-2l4 Ti-210—>Pb-210—>Bi-210 Ti-206—>Pb-206 (stable isotope of lead,... 

Man-made radioactive atoms are produced either as a by-product of fission of uranium atoms in a nuclear reactor or by bombarding stable atoms with particles, such as neutrons, directed at the stable atoms with high velocity. These artificially produced radioactive elements usually decay by emission of particles, such as positive or negative beta particles and one or more high energy photons (gamma rays). Unstable (radioactive) atoms of any element can be produced. 

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