Mass-yield distribution

Figure 1 shows some of the single fallout particles collected after the Chinese nuclear explosion on May 14, 1965 (14). Figure 2 shows the mass-yield distribution of the fission products in some of the single fallout particles (5). The values of H calculated in this manner range from 30-50 sec., as shown in Table 1(4). 

Figure 2. Mass-yield distribution of the fission products in single fallout particles collected at Osaka, Japan and Fayetteville, Ark. after the May 9, 1966 Chinese nuclear explosion (4)...

Just as earlier we were able to observe mass-yield distributions of the fission products from the fissionable nuclide used in the Chinese nuclear device, it is possible to see part of the mass-yield curve from the fission of 244Pu, which was synthesized originally in a supernova. Figure 6 shows the mass-yield distribution of the excess fissiogenic xenon observed in the meteorite Pasamonte (15). 

Figure 6. Mass-yield distribution of the fissiogenic xenon isotopes in the meteorite Pasamonte (15)...

Figure 11.15 Schematic representation of the mass yield distributions for the spontaneous fission of the trans-berkelium nuclides. (From D. C. Hoffman, et al., Spontaneous Fission in Nuclear Decay Modes, D. N. Poenaru, Ed. Copyright 1996 IOP Press. Reprinted by permission of IOP Press.)...

Mass-yield distributions for thermal-neutron-induced fission of the following nuclides ... 

The general form of the mass-yield distribution was also known the yield drops rapidly with increasing mass number above 144. By showing that the cumulative fission yield of the 4-year product was about twice that of the 48-h product, combined with the results of activation measurements, Pm and Pm were identified by mass number as well as atomic... 

Schematic representations of all of the measured mass-yield distributions (normalized to 200% fragment yield) for SF of the trans-Bk isotopes are shown in Fig. 18.13 (Hoffinan and Lane 1995). It is interesting to observe rather sudden changes from asymmetric to symmetric fission as reflected by the mass distributions changing from asymmetric to symmetric mass distributions as the neutron number increases toward N 160 for the elements Fm Z = 100), No (Z= 102), andRf(Z= 104).

Schematic representation of all known mass-yield distributions for spontaneous fission (SF) of trans-Bk isotopes (Hoffman and Lane 1995) (see also Fig. 4.16 in Chap. 4, Vol. 1)...

As typical data, the TKE and mass-yield distributions observed in SF of Md (Hulet et al. 1989) are depicted in Fig. 18.14a, b, respectively two components are clearly seen in the TKE distribution. The two-component analysis yielded the fact that the high-TKE events mostly constitute the sharp mass-yield curve around symmetry and the low-TKE ones a broad flat-topped distribution. Some theoretical calculations to understand bimodal fission of heavy actinides have been extensively performed (Warda et al. 2002 Asano et al. 2004 Bonneau 2006 Dubray et al. 2008 Ichikawa et al. 2009). 

The presence of two kinds of deformation paths in low-energy fission of actinides has been verified by examining the correlation among saddle-point configurations, scission configurations, and mass-yield distributions (Nagame et al. 1996, 2001). The first path is initiated at... 

Ganapathy, R. and Kuroda, P. K. Mass-Yield Distribution of the Iodine... 

The population of fission product elements as a function of time is changing rapidly. These may be estimated from a knowledge of the half-lives of the fission product chain members, the mass chain yield, and the independent yield distribution along the mass chains. Although there are some uncertainties in these procedures largely because of lack of data on short-lived species, and a less than perfect understanding of the charge distribution function, reasonable estimates of radioactive atom... 

For f=3.7% (and above), D-2, indicating that the network is sufficiently dense and uniform that the blend can be considered an effective medium-, i.e. the fractal dimensionality is the same as the spatial dimensionality. As f is decreased toward the percolation threshold, D becomes less than the spatial dimensionality indicating a self-similar structure with holes on every length scale. At f f,., the analysis of the mass density distribution yielded D = 1.5. 

Uniform Surface Injection. Although a mass transfer distribution yielding a uniform surface temperature is most efficient, it is much easier to construct a porous surface with a uniform mass transfer distribution. Libby and Chen [34] have considered the effects of uniform foreign gas injection on the temperature distribution of a porous flat plate. For these conditions, however, boundary layer similarity does not hold. Libby and Chen extended the work of Iglisch [35] and Lew and Fanucci [36], where direct numerical solutions of the partial differential equations were employed. An example of the nonuniform surface enthalpy and coolant concentrations resulting from these calculations is shown in Fig. 6.16. 

In addition to measuring the variation of mass yield, the variation of fission yield in isobaric mass chains as a function of the proton number has bear studied. In Figure 14.10, "individual yield data are presented for the A = 93 chain. In gmeral, the charge distribution yields follow a Gaussian curve with the maximum displaced several units below the value of Z for stable nuclides with the same A. For A = 93 the yield is largest for Z = 37 and 38 most probable charge, Zp) compared to the stable value of Z = 41. 

Mechanistic Uncertainties and Errors. Mass-balance mechanism yield consistency tests are definitive only to the extent that complementary changes in the product yield distributions have been monitored. To illustrate the nature of this limitation, we recall that stable and activated nascent products are formed from F-for-F Reaction 18 via respective Reactions 24 and 25. Because the yield from Reaction 25 is not subject to decomposition, no (P/Z) interdependence is possible between these contributions to Y(CH3CHF F). Chemical intuition thus provides the only basis for assigning the species from Reactions 24 and 25 to the same primary reaction channel (25,34,45). 

This last equation expresses the balance between formation and loss of the intermediate. The first term on the right represents formation by enzyme 1, the third consumption by enzyme 2, and the second loss by diffusion, this process being proportional to the total area of the cell wall and therefore to the total number, n, of the cells among which the bacterial mass is distributed, and 2 are factors giving the yields of intermediate from enzyme and of enzyme from intermediate respectively. 

Abstract This chapter first gives a survey on the history of the discovery of nuclear fission. It briefly presents the liquid-drop and shell models and their application to the fission process. The most important quantities accessible to experimental determination such as mass yields, nuclear charge distribution, prompt neutron emission, kinetic energy distribution, ternary fragment yields, angular distributions, and properties of fission isomers are presented as well as the instrumentation and techniques used for their measurement. The contribution concentrates on the fundamental aspects of nuclear fission. The practical aspects of nuclear fission are discussed in O Chap. 57 of Vol. 6. 

There is, however, an interesting exception in the figure, namely Md, which shows a neutron yield of about 2 rather than an extrapolated value of 4. The nucleus of Md is the only nucleus among those shown in Fig. 4.20 with a symmetric yield distribution as seen in O Fig. 4.16. (The fermium isotopes with A = 254, 256, and 257 (N = 154, 156, and 157) shown also in Fig. 4.20 have an asymmetric mass distribution (see Fig. 4.16)). Unfortunately, no values of prompt neutron emission are known for the other isotopes with Z > 100 that show a symmetric mass distribution ( Fig. 4.16). 

It is interesting to note that the spectra of ternary particles extend to different atomic numbers, which coincide nearly with the size of the neck that results from the postulate extracted from the mass yield and nuclear charge distributions. To correlate the data, it has been postulated that the two spheres of the dumbbell configuration shown in O Fig. 4.11 for the fission of are practically the same for all asymmetrically fissioning nuclei from Z= 90 to about 99 and, consequently, that the variation in the neutron/proton numbers of the different compound nuclei must be connected with the size of the neck. O Fig. 4.29 is the direct experimental proof for this assumption in the fission of uranium, the neck size is (92 — 82 =) 10 protons in the fission of californium, the neck size is (98 — 82 =) 16 protons. The situation is similar for neutrons and for the total mass. This is, however, less convincing due to prompt neutron emission. 

For studying fission properties such as mass-yield and total kinetic energy (TKE) distributions of very short-lived spontaneous fission (SF) isotopes, the SWAMI (spinning-wheel analyzer for millisecond isotopes) apparatus was constructed (Hulet et al. 1989). The schematic diagram is shown in O Fig. 18.8. 

Fig. 10 SOA product volatility distributions for a-pinene and limonaketone in dark green and mass yields vs Cqa as dark green curve. Precursors with similar volatility, structure, and chemistry have similar yields. Product volatility distribution and yields fOTD-limonene ozonolysis are shown as light green bars and a light green curve (and gray data points). Oxidation of the additional exocyclic double bond in limonene results in substantially less volatile SOA products and correspondingly higher SOA yields...

Prototypes lean toward the use of stored hydrogen as a fuel, because the reforming of hydrocarbons is comphcated when dealing with PEMFC technology. At present, the storage solutions available are unable to deliver sufficient mass yields (that is, the mass of hydrogen in comparison to the mass of the tank) - around 3%, which is prohibitive in terms of autonomy. In addition, the hydrogen distribution infrastructure is practically non-existent, and to create such an infrastracture would entail enormous investment costs. 

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