Thorium concentration ratio

Neder H, Heusser G, Laubenstein M (2000) Low-level y-ray germanium-spectrometer to measure veiy low primordial radionuclide concentrations. ApplRadiat Isot 53 191-195 Palacz ZA, Freedman PA, Walder AJ (1992) Thorium isotope ratio measurements at high abundance sensitivity using a VG 54-30, an energy-filtered thermal ionization mass spectrometer. Chem Geol 101 157-165... 

The accumulation of radiogenic helium in confined groundwaters is mainly determined by the duration of water entrapment. Applying the data available on uranium and thorium concentrations in the host rocks and rock water ratios, reliable, though semiquantitative, dating is possible in the range of 104 10s years. 

Figure 2. Thorium concentration profile and distribution ratio for Contactor I (%) aqueous phase (O) solvent phase (X) distribution ratio (DTn) (------) calcu-...

Sheppard, S.C., Evenden, W.G., 1988. Critical compilation and review of plant/soil concentration ratios for uranium, thorium and lead. Critical compilation and review of plant/soil concentration ratios for uranium, thorium and lead. J. Environ. Radioact. 8, 255-285. 

Becker, J. S., Burow, M., Boulyga, S. F., Pickhardt, C., Hille, R., and Ostapczuk, P. 2002. ICP-MS determination of uranium and thorium concentrations and U-235/U-238 isotope ratios at trace and ultratrace levels in urine. Atom Spectrosc 23(6), 177-182. 

The results showed that the activity concentrations of U and Th ranged from 138 -218 Bq/L and from 101 - 339 Bq/kg, respectively, with average values of 156 and 187 Bq/kg, respectively. These values showed enhancement in uranium and thorium concentrations in the area compared to the background level (40 - 50 Bq/kg). Fractionation of uranium isotopes was observed, where U/ U activity ratio was less than unity in all cases, with an average value of 0.83. It is also clear that Th and Ra are in secular equilibrium. These findings may be due to the rapid dissolution of from the damaged crystal lattices and lower mobility of thorium due to the low solubility of the thorium salts. 

Limited uranium concentralion. In solution reactors, uranium concentration is limited b solubility or corrosion effects, and in slurries, by the effective iscosity and settling characteristics. In H20-moderated reactors, in particular, a high uranium or thorium concentration is necessary for a high convcr.sion ratio. Concentrations up to 1000 g/liter, however, may be con.sidcred for solutions and up to 4000 g/liter for fluidized beds. 

When the neutron leakage is not negligible and Vree/Vih is less than 1, a finite thorium concentration exists for which the breeding ratio is a maximum. This is indicated in Fig. 2-4, in which the initial breeding ratio is... 

Fig. 2-4. Breeding ratio as a function of thorium concentration and vfea vih io a one-region reactor. Reactor temperature = 300°C, r tf, = 2.25.

The initial breeding ratios and critical concentrations obtained from the Eyewash and two-group, two-region calculations are given in Fig. 2-5 for slurry-core reactors (zero core thorium concentration also corresponds to a solution-core reactor). With solution-core reactors the effect of the value of Tjrea upon breeding ratio was less pronounced than for slurry-core reactors, since fewer resonance absorptions take place with the lower fuel concentrations. The blanket thorium concentration had little influence upon the above effect for blanket thorium concentrations greater than 250 g/liter. 

Fiq. 2-7. Effect of core thorium concentration on breeding ratio and wall power density of two-region slurr " reactors, rj = 2.25, total reactor power = 100 Mw (heat), pressure vessel = 10 ft ID, in blanket = 3 g/liter, poison fraction = 0, temperature = 280 C. 

The breeding ratio for the reacior varialiles considered is plotted in Fig. 2-11 as a function of pressure-vessel size for 4- and 5-ft-diameter cores with several blanket thorium concentrations. More extensive results, including neutron balances, are given in Table 2-8 for selected reactors. The neutron... 

Fig. 2-11. Breeding ratio as function of pre.ssure vessel size for various core diameters and blanket thorium concentrations. Core poison fraction = 0.07, corrosion products = 0, co])per concentration = 0, blanket U = 3.0 g/kg of Th, = 2.2"), mean temi)cratui e = 280°C, cciuilibrium isotope concentrations.

Fig. 2-13. Breeding ratio vs. thorium concentration for one-region reactors of...

Pa233 ijj tije blanket, breeding ratio, and core and blanket poison fractions as functions of time for a two-region 60-Mw thorium breeder reactor. Core thorium concentration = 150 g Th/liter, blanket thorium concentration = 1000 g Th/liter, temperature = 280°C. 

Fig. 2-17. Comparison of breeding ratios and core concentrations for two-region breeder reactors with various core-thorium concentrations. Core diameter = 4 ft, reactor diameter =9 ft, 280°C, blanket thorium concentration = 1000 g/liter, blanket ))iocessing started when blanket concentration reached...

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