234mPa

In the second separation, uranium is extracted from thorium. Ethyl acetate is the extractant for uranium, which is bound in a nitrate complex. Thorium remains in the aqueous phase. Thorium is then co-precipitated with Nd(OH)3 to avoid absorption of the beta particles emitted by 234Th and 234mPa by the large amount of NH4N03 if the solution were simply evaporated and counted. The filter with Nd(OH)3 is mounted on a planchet for counting beta and alpha particles. 

Calculate the total disintegration rate of alpha particles, in disintegration per minute, from the three isotopes of uranium in 1 mL of 0.02 M UO + solution of natural uranium. Calculate also the beta-particle disintegration rate of the 234Th and its short-lived 234mPa progeny that are in radioactive equilibrium with the 238U. 

Principle of Separation. Thorium co-precipitates with NdF3 while U02+ remains in solution. Filter paper with the neodymium fluoride precipitate and associated thorium is mounted on a planchet and counted for alpha and beta particles. The presence of alpha particles in the NdF3 precipitate indicates the amount of uranium that accompanies the precipitate unless 230Th is present. The ratio of the beta-particle count rate in the precipitate to the count rate in the initial sample of uranium with 234Th and 234mPa indicates the fractional yield of the co-precipitation process. 

Th itself decays with relatively weak betas (maximum beta energy 0.20 MeV) to 234mpa which is a high-energy beta emitter (maximum beta energy 2.29 MeV, half-life 1.17 min). Thus, if a filter is dried and carefully folded (possible with polycarbonate, e.g.. Nude-pore filters, not with membrane filters, which will break) to fit the beta detector holder and covered with a thin foil, the activity measured is due mainly to Pa, with some contribution from Th. 

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