Fission yield

FIGURE 17.22 The fission yield of uranium-235, Note that the majority of fission products lie in the regions close to A = 90 and 130 and that relatively few nuclides corresponding to symmetrical fission (A close to 117) are formed. 

A large neutron cross section of 235U for fission (5.8 x 10 26 m2), a high fission yield (6%) for "Tc, and a long half-life of the resulting "Tc (2.1 x 105 yr) make this radionuclide one of the principal nuclear wastes. Fig. 1 shows radioactivity of nuclear wastes plotted against cooling time in years. Tc activity is very important in the time interval 104-106 years. 

Nuclei formed in fission Decay characteristics, fission yields, and... 

Amongst other N-nucleophilic species, hydroxylamine exhibits some abnormal behavior besides oxime formation (p. 25). Thus it reacts with diphenyl cyclopropenone42 probably by 1,4-addition and subsequent oxidation and/or decarboxylation giving rise to 3,4-diphenyl isoxazolone (328) and desoxybenzoin oxime. With pentyl cyclopropenone48 hydroxylamine undergoes addition followed by normal oxima-tfon after ring fission yielding 2,3-dioximino octane (329). 

This useful technique has made many contributions to radio- and nuclear chemistry, although primarily for investigational purposes rather than those of separation for its own ends. Thode and his co-workers have made many investigations into the inert gases produced in fission and it was by these means that the fine structure of fission was first discovered (79), (121). Since then several other elements, the rare-earths, strontium, caesium, zirconium, and molybdenum (35), (50), (132) have been investigated, and the isotopic ratios obtained provide relative values of fission-yields which are more accurate than can be obtained by standard radiochemical means. The latter technique, however, requires rather less heavily irradiated material than the former. 

Inghram, M., R. J. Hayden and D. C. Hess 235U Fission Yields in the Rare-... 

Wiles, D. R., B. W. Smith, R. Horsley and H. G. Thode Fission Yields of the Stable and Longlived Isotopes of Caesium, Rubidium, and Strontium, and Nuclear Shell Structure. Canad. J. Physics 31, 419 (1953). 

Among the long-lived isotopes of technetium, only Tc can be obtained in weigh-able amounts. It may be produced by either neutron irradiation of highly purified molybdenum or neutron-induced fission of uraniimi-235. The nuclides Tc and Tc are exclusively produced in traces by nuclear reations. Because of the high fission yield of more than 6%, appreciable quantities of technetimn-99 are isolated from uranium fission product mixtures. Nuclear reactors with a power of 100 MW produce about 2.5 g of Tc per day . 

Curtis, D., Benjamin, T. et al. 1989. The Oklo nuclear reactors cumulative fission yields and nuclear characteristic of reactor 9. Earth and Planetary Science Letters, 89, 193-206. 

It was also assumed that the production ratios of the three radionuclides were the same as the ratios given for weapon fission yields (12). For each of the three storms and the reported nuclear explosions for the period, an analysis of the fractional deposition by event was made for each collection site along, and by regions of, the California coast. Based on these assumptions, the fraction of 140Ba from the most recent atmospheric nuclear explosion before each storm was 1.00. The 140Ba deposition on storm date was extrapolated to the explosion date. The initial... 

Thienyllithium derivatives with an alkyl group or H atom at C-5 deprotonate at C-3 with further BunLi in HMPT this leads to ring fission, yielding ene-yne thiolates which can be methylated to form the enyne sulfides. If the mole ratio BuLi/thiophene exceeds... 

Fig. 3. Mass fission yield curves as function of excitation energy and degree of fission probability...

The three neutrons released by fission of a 235U nucleus can induce three more fissions yielding nine neutrons, which can induce nine more fissions yielding... 

The technetium isotope of interest for nuclear fuel waste disposal is Tc. It is a pure 3-emitter (E = 0.293 MeV) with a half-life of 2.13x10 years. Its high fission yield of 6% accounts for the relatively high concentration 0.02% by weight) (1) in fuel discharged from a CANDU (CANada Deuterium Uranium) reactor (burnup 650 GJ/kg U). 

Whetherill, G. W. (1953) Spontaneous fission yields from uranium and thorium. Phvs. Rev., 92, 907-12. 

The two fission-produced radio-strontium isotopes of interest in environmental samples are 90Sr and 89Sr. Sr-90 has a fission yield of 5.8 %, a half-life is 28.78 a, and the radioactive daughter 90Y with a half life of 2.67 d, to which it decays by beta-particle emission. Sr-89 has a fission yield of 4.7%, a half life of 50.52 d, and decays to the stable daughter89 Y. The decay schemes given in Figure 13.1 show that these two radio-strontium isotopes for practical purposes can only be measured by beta-particle counting. 

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