U-fission

Thiel K, Vorwerk R, Saager R, Stupp HD (1983) U fission tracks and U-series diseqttilibria as a means to study recent mobilization of ttranittm in archean pyritic conglomerates. Earth Planet Sci Lett 65 249-262... 

But Au, Pd, Be, and Po are not among the strongly active products of U fission. Thus, Au and Fd are separated from Tm by reduction with formic acid. Be la ppted. from 12 V SCI by SQe. Te la not ppted. under these conditions. On the other hand, hydrazine HC1 ppte. Te hut not Fo. 

Besides their presence due to in situ radioactive decay within a given solid sample, radiogenic " He, " Ar, Xe, Pu-fission xenon (and krypton), and likely also U-fission xenon, are also prominent or observable constituents of planetary atmospheres, and their abundance is important in constraining models for planetary atmosphere evolution (see Chapter 4.12). 

If a mineral crystallizes at relatively high temperatures, any damage to the crystal stmcture produced by U fission rapidly heals. This anneahng occurs by atomic reorganization of the crystal structure and, thus, is a diffusive... 

A typical electrical generating plant has a capacity of 500 megawatt (MW 1 MW = 10 J s ) and an overall efficiency of about 25%. (a) The combustion of 1 kg of bituminous coal releases about 3.2 X 10 kj and leaves an ash residue of 100 g. What weight of coal must be used to operate a 500-MW generating plant for 1 year, and what weight of ash must be disposed of (b) Enriched fuel for nuclear reactors contains about 4% U, fission of which gives... 

Radioactive decay constant Absorption cross section, b Direct yield from U fission, y atoms per atom fissioned... 

Practical irradiation periods for fuel in power reactors are in the range of about 1 to 4 years. Most of the fission-product nuclides reach saturation in this period. An example is 8.05-day I, which is formed in 2.93 percent of U fissions. Its saturation activity is 0.023 Ci/W. 

Effects of Gamma-Ray U Fission Spectrum Neutron, and Combined Gamma-Ray... 

Thermal fission of (fission of U, fission of Pu isotopes and n.y-reactions are important effects in a nuclear reactor). 

U-fission product mixtiires (extraction of quaternary alkylammonium-plutonyl nitrate complex into hexone-TTA extraction... 

At Brookhaven a series of 20 U0t-H,0 exponential-lattice experiments has been performed The UO> fuel is 3% U enriched and has a density of 9.S7 g/cm. The particulars of the experiments are reported in a review paper Measurements were made for critical buckling, reflector saviiKS, 6, the ratio of u fissions to fissions and p, the ratio of epicadmium to subcadmium absorptions in u . ... 

Detailed parameter measurements made in the SE included determinations of the thermal-neutron distributions in terms of subcadmium foil activation thermal-neutron temperatures in terms of Lu/l/v activity ratios epithermal-neutron fractions in terms of Th capture and u fission cadmium ratios U production in terms of neutron captures in Th and lattice fissions in terms of the Th/ U fission ratios. The HAMMER computations generally agreed with the intracell activation profiles. The spectral index measurements agreed poorly because the computations overestimated the spectral index in all coolants. 

The fast fission factor e, the material buckling B, the quantity Ap/AB were measured in critical assemblies of each fuel mixture. The thermal-neutron diffusion area L wa.8 calculated from thermal-neutron cross sections. The delayed-neutron fraction was determined from the delayed-neutron fractions for U and measured by Keepin and the "U-to- U fission ratio measured in the critical assemblies. 

Eiqterimental evidence indicates that the fast het-erogeneity effect. as inferred from the measured spatial distribution of the U fission rates within the unit cell is accounted for reasonably well. However, the calculated central reactivity difference between a homogeneous sample (Set A) and a plate-type heterogeneous sample (Set C) was about a factor of 4 lower, than the experimental value. The measured reactivity worth of a nominally 2-in. cube, plate-type heterogeneous sample was 20% (or 0.464 a 0.004 Ih) more than an equivalent homogeneous sample. Both samples had Uie core composition of Assembly 5. It appears, therefore, that equivalence theory is not adequate for the treatment ot the resonance... 

Counter traverses were made tor B (n,a) and for Pu, and U fission from core center fiirough the... 

The fission counter traverses described above were normalized, with the aid of central fission ratio measurements, to give " o/ Pu and U/ " fission ratios as a function of radial position as shown in Table L The analytical values coOipare well, especially for thb U/ °Pu ratio. The discrepancy in the / Pu ratio is believed to Ipe the result of errors in the ENDF/B-68 cross sections for U. This conclusion is supported by the fact that six sioh ratios, relative to U, all ve about the same error and in the same directitm. 

The calculated and measured U fission-rate distributions as a function of the core height are shown in Fig. 1. The measured points were obtained with foils placed next to the slab in the unit cell. In the blanket region the foils were placed on top of the depleted uranium blocks. The accuracy of the relative activities of the foils was 0.5 to 1.0%. The solid line was obtained with the heterogeneous core fluxes using Sn 4 and the anisotropic option foil cross sections were those of the... 

The results of analysis including the keff bias, Ak Oieterogeneity), fission ratios, reaetton rate traverses, Na void reactivity effects, and the wortii of fuel and B C drawer at the core center are shown in Table I. Of particular interest is the U fission ratios. The C/E values in the high Ptt zoned assemblies are lower by 2 to 4%... 

The reaction rate parameters measured are ratio of therinat-to-thermal captures, (pu) ratio of qiithermal-to-aiermai fissions (6 ratio of U captures to U fissions (C ) ratio of U fissions to U fissfams (On) and ratio id Lu-to- CU subcadmium captures in the fuel normalized to the same ratio in a Maxwellian thermal flux (R). Measurement and analysis techniques used in this study were Identical to those described In Ref. 3. 

Additional ZPR3-48 analysis was done to define other potential data tests. Figure 1 compares calculated and measured U fission rate profiles the agreement implies adequate U removal cross sections at high energies in ENDF/B-IV. 

Fig. 1. Comparison of radial U fission rate proHle measured in ZPR 3-48 with GA calculation using ENDF/B-nr.

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