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Abstract  

The independent yield of88Y from thermal neutron-induced fission of235U was determined relatively to the well-known yield of91Y. An upper limit obtained was 1.53×10–8%.

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Abstract  

The kinetics of the oxidation-reduction reaction between N,N-diethylhydroxylamine (DEHAN) and vanadium(V) in nitric acid media have been studied by spectrophotometry at 13.5 °C. The rate equation of reaction was found to be -d[V(V)]/dt = k [V(V)] [DEHAN] by investigating the influence of the concentration, acidity, ionic strength and the effect of initial concentration on reaction. The rate constant of reaction k = 36.38 mol/l-2 ·min-1 when = 2.0 mol/l. A possible mechanism of reaction has been suggested on the basis of chemical analysis, 1 H NMR and ESR spectra.

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Abstract  

N,Ndiethylhydroxylamine (DEHAN) can rapidly reduce Pu(IV) and Np(VI) extractable with trinbutyl phosphate (TBP) to Pu(III) and Np(V) unextractable with TBP in nitric acid solution. In order to apply DEHAN in the purification cycle step of U (noted as contactor 2D) of the secondcycle of the Purex Process to separate Np and Pu from U, the reduction of Np(VI) and the stability of Np(V) with DEHAN and the singlestage reduction extraction and backextraction of Np(VI) have been studied according to the experimental conditions of contactor 2D. The results show that more than 99% of Np(VI) can entirely be reduced to Np(V) with DEHAN within a few minutes either in aqueous or in organic phase containing uranium and without containing uranium, and more than 99% of Np(VI) can be backextracted from the organic to the aqueous phase with DEHAN as a reductant. More than 99% of Np(V) exists in nitric acid solution at least for 8 hours in presence of 0.01 mol/l DEHAN. These results are of benefit to the cascade extractionseparation of U/Np in contactor 2D in order to decontaminate Np from U.

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Hydroxylamine derivatives in Purex Process

I. Study on the kinetics of redox reaction between N,N-diethylhydroxylamine and nitrous acid

Journal of Radioanalytical and Nuclear Chemistry
Authors:
Zhang Anyun
,
Hu Jingxin
,
Zhang Xianye
, and
Wang Fangding

Abstract  

The kinetics of oxidation-reduction reaction between N,N-diethylhydroxylamine (DEHAN) and nitrous acid in nitric acid solution have been studied by spectrophotometry at 9.5°C. The rate equation is −d[HNO2]/dt=K[HNO2]·[DEHAN][HNO3] and the rate constantK=12.81 (mol/l)−2·min−1. A possible mechanism has been suggested on the basis of chemical analysis and Raman spectra. The activation energyE and the thermodynamic functions ΔH #, ΔG # and ΔS # are also calculated.

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Abstract  

The kinetics of oxidation-reduction reactions between N,N-diethylhydroxylamine (DEHAN) and plutonium(IV) in nitric acid solution have been studied by spectrophotometry at 25.2 °C. The initial rate equation of the reaction is -d[Pu(IV)]/dt=k 0[Pu(IV)]2[DEHAN]1.26/[H+]2.53, where the rate constant of the reaction (k 0) is (5.93±0.84).103 (mol/l)0.27 min-1. The complete rate equation and the rate constants of the reaction are also derived.

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Abstract  

The distributions of the chemical states of131I,132I,133I,134I and135I produced by the spontaneous fission of252Cf were investigated by the method of fractional precipitation separation in 6M NH4OH solution followed by measurement of the X-ray spectrum of the samples with a Ge(Li) detector. The iodine fission fragments were separately collected in the matrices of NaNO3, NaCl, dehydrated sodium sulfate, CH3COONa·3H2O, Na3H2IO6, KI and NaIO3 crystals. The results showed that the distribution of the chemical states was the function of the collection time, the nature of matrix materials and the type of iodine isotopes. The relative amount of the reduced states of134I decreased with the increase of collection time in the matrix of NaNO3. The ratio of the amount of reduced states to the total amount of the134I was the highest (50.4%) in NaCl matrix and the lowest (9.4%) in Na3H2IO6 matrix. The relative quantities of reduced states of135I were the highest (58.5% and 97.7%) and that of134I were the lowest (16.9% and 63.1%) in matrices of NaNO3 and NaCl, respectively.

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Abstract  

The distribution of the chemical states of tellurium isotopes produced by252Cf spontaneous fission, collected separately in the matrixes of NaCl, Kl, NaF, CH3COONa·3H2O, Na2SO4 and NaNO3 crystals have been investigated. Two chemical states of tellurium isotopes maintained in these matrixes are Te(IV) and Te(VI). The relationships between the distribution of the chemical states of tellurium isotopes and the produced mode of tellurium, the chemical properties of collection matrixes, the time for collecting fission fragments are studied and the possible mechanism of the interactions of the fission products and the matrixes is discussed. The results show that the distribution of chemical states of tellurium isotopes depends on the chemical properties of the collection matrixes mainly.

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Abstract  

The reduction kinetics of pertechnetate by thiocyanate in perchloric acid is studied by spectrophotometric method. The effect of the concentrations of pertechnetate, hydrogen ion and thiocyanate on the reaction rate is investigated. The kinetic expression at 25°C is: −dC VII/dt=(2.2±0.4)·10−3 [TcO4 ]1.1 [H+]3.2 [SCN]3.3 The effect of temperature on the reaction rate is studied. The activation energy is 91 kJ/mol. The possible mechanism of the reaction is discussed.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
Zhao Xin
,
Li Xueliang
,
Guo Jingru
,
Wang Fangding
,
Tang Peijia
,
Liu Daming
,
Cui Anzhi
, and
Su Shuxin

Abstract  

The cumulative yields of127gSn and128Sn in the region near symmetry for the spontaneous fission of252Cf have been measured by a radiochemical method for the first time. The yield values are (0.0437 ±0.0021)·10–2 and (0.182±0.009)·10–2, respectively. The cumulative yield of128Sn measured in this work is compared with those predicted based on WAHL's empirical Zp and Ap' models. The measured value is higher than both predictions, values 0.164·10–2 from the Zp model, and 0.144·10–2 on the basis of Ap' models.

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Abstract  

The fractional cumulative yields (FCY) of133mTe and133gTe in the spontaneous fission of252Cf were measured for the first time by a radiochemical method. The values ofFCY are 0.533±0.014 and 0.291±0.042 for133mTe and133gTe, respectively. The isomeric state to ground state fractional independent yield (FIY) ratio of133Te,R, was found to be 3.5. The root-mean-square angular momentum of the primary fragment corresponding to the fission product133Te, Jr.m.s.=8.8h, was estimated according to a simple one-parameter statistical model. The fractional cumulative yields from this work together with other literature data in the mass region A=131–141 are compared with the normal yields given by the empiricalZ p model by Whhl. It suggests that both theN=82 neutrons shell and nucleus pairing effects are not apparent for the spontaneous fission of252Cf.

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