FUNDAMENTAL AND APPLIED FUNDMENTAL RESEARCH·Radiochemistry and Nuclear Chemistry
157
Radiochemistry and Nuclear Chemistry
Extraction of U, Pu, Am, Eu and Sr With TODGA-DHOA/OK
ZHU Wen-bin, JIANG De-xiang, YE Guo-an, YE Yu-xing
The extraction of U(Ⅵ), Pu(Ⅳ), Am(Ⅲ) Eu(Ⅲ) and Sr(Ⅱ) with N,N,N’,N’-tetraoctyl-3-oxapentane
diamide (TODGA) and N, N-dihexyl-octanamide (DHOA)/kerosene (OK) as extractants from nitric acid
solutions has been studied. The results show that the value of D(M) (there, M are U, Pu, Am and Eu)
increase with the increasing HNO3 concentration, while the value of D(Sr) reaches the maximum at
3 mol/L HNO3.
The value of D(Pu), D(Am), D(Eu) and D(Sr) decrease with the increasing DHOA concentration,
while the D(U) slightly increase with an increase of DHOA concentration.
Study on Catalyzed Electrolytic Plutonium Oxide Dissolution
LIU Li-sheng, GUO Jian-hua, CHANG Li, LI Rui-xue,
CHANG Shang-wen, OUYANG Ying-gen
The dissolution of PuO2 prepared or calcinated at high temperature has been a difficult task. It is
shown that crystalline PuO2 is very difficult to dissolve in nitric acid solution, and insoluble in nitric acid
solution below about 4 mol/L. Now the electrochemical method is frequently used in the dissolution of
PuO2.
The cell for catalyzed electrolytic Plutonium oxide dissolution (CEPOD) is a 2-compartment cell,
and the anode and cathode compartments are separated from each other. PuO2 is oxidized in anode
compartment:
＋
－
PuO2
PuO2 ＋e
E0=1.58 V
(1)
＋
－
2
0
PuO2
PuO2 ＋2e
E =1.24 V
(2)
2+
+
The final product of oxidative dissolution will be PuO2 . Ag added in anode electrolyte will be
oxidized into Ag2+ which is a strongly oxidizing ion.
－
Ag+
Ag2+ + e
E0=1.98 V
(3)
Based on the above potentials, it is possible for the dissolution of PuO2.
A new H-model cell is designed, 2 compartments of which are separated by a porous sintered glass
(pore diameter is 2.5-3.5 μm). The capacity of each compartment is 10 mL. Pt plate is used as working
electrode (area is 1 cm2), Pt wire is used as counter electrode and reference electrode, respectively. The
potential of reference electrode is 0.7 V in 6 mol/L HNO3 solution.
The use of catalyzed electrolytic Plutonium oxide dissolution was studied in the cell. PuO2 can be
oxidized into PuO22+ with Ag+ in anode compartment, and the dissolution rate is higher than 99%. The
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dissolution velocity increases with increasing Ag+ concentration and current density. The effect of HNO3
acidity in the range of 4-8 mol/L on dissolution velocity can be ignored. The current efficiency of
dissolution increases with increasing Ag+ concentration and decreases with increasing current density.
There is no definitely difference between the dissolution rates of Pu and Am contained in PuO2 powder.
The electro- migration of Ag+ from anode compartment to cathode compartment is slow.
Study on Method for Separating Micro Plutonium
From Abundant Uranium
LI Hui-bo, WANG Xiao-rong, LIN Can-sheng, SONG Feng-li, GAO Yu-lan
Extraction-chromatography has not only the selectivity of solvent extraction but also high performance character of chromatography, so it has significant advantage on the separation supermicroelements,
especially actinides. In present research micro plutonium was separate from abundant uranium by extraction-chromatography and ion exchange. Firstly extraction-chromatography was use to remove most U and
fission elements, then ion exchange was performed to refine and purify Pu.
Based on a series of static experiments, the quaternary ammonium and TBP extraction-chromatography were selected and the adsorption acidity are 4 and 2 mol/L, respectively. Type 256 anion exchange
resin was selected and the adsorption acidity is 6.5 mol/L. The single column condition experiments and
bunch columns demonstration experiments also were studied. The result shows that the Pu recovery
attains to near 70% and the purification coefficient to U is 107 by using the program.
Study on Extraction of Pu(Ⅳ) by Tri-iso-Amyl Phosphate
CHENG Qi-fu, LUO Fang-xiang, LIU Xie-chun, YE Guo-an, XIAO Songt-ao, LI Gao-liang,
ZHANG Hu, HUANG Xiao-hong, ZHU Wen-bin, JIANG De-xiang
The extraction performance of Pu(Ⅳ) with tri-iso-amyl phosphate (TiAP) were studied. The effects
of the concentration of nitric acid and the ratio of phase on the extraction efficiency of Pu(Ⅳ), and on the
formation of second organic phase were investigated. The experimental results indicate that the
distribution ratios of Pu(Ⅳ) increase obviously with increasing aqueous nitric acid concentration, and it is
not found the formation of second organic phase when the concentration of Pu(Ⅳ) in organic phase is
reached 77 g/L and the concentration of nitric acid in aqueous phase is 3.5 mol/L. In addition, the
reduction back-extraction condition of Pu(Ⅳ) from 30% TiAP/OK was also studied.
The results show that Pu(Ⅳ) loaded in the organic phase could be effectively back-extracted into
aqueous phase by using 0.8 mol/L DMHAN-0.3 mol/L MMH-0.3 mol/L HNO3 as the stripping agent; at
20 ℃, the stripping percentage of Pu(Ⅳ) is over 90% while the concentration of Pu(Ⅳ) in the organic is
approached 25 g/L at phase ratio (O/A) 2.
FUNDAMENTAL AND APPLIED FUNDMENTAL RESEARCH·Radiochemistry and Nuclear Chemistry
159
Kinetic Studies on Reactions Between Monomethylhydrazine and Fe3+
as Well as N,N-Dimethylhydroxylamine and Fe3+
by Measuring Potential of Fe3+/Fe2+
CHEN Hui, ZHANG Hu, HE Hui, LI Gao-liang
The kinetic studies on the reactions between monomethyldrazine and Fe3+ as well as N,N-dimethylhydroxylamine and Fe3+ in nitric acid system are performed by measuring open-circuit potential of Fe3+/
Fe2+. The effect of some factors such as the concentration of MMH or DMHAN, the concentration of
nitric acid, ionic strength, temperature and the concentration of Fe3+ on the reaction rate is also studied.
The reaction rate equation may be expressed as follows for MMH-Fe3+:
－
＋
－
－dc(Fe3+)/dt＝k c1.3(MMH) c 2(H )·c(Fe3+) c 0.5(Fe2+)
－
－
The rate constant is 1.15×10 3 (mol/L)1.2 s 1 at 55 ℃ and activation energy of the reaction is
(94.51±6.1) kJ/mol. The influence of ionic strength on the reaction is negligible.
The reaction rate equation may be expressed as follows for DMHAN-Fe3+:
－
＋
－
－dc(Fe3+)/dt＝k c2(DMHAN) c 2.9(H ) c(Fe3+) c 1(Fe2+)
－
－
The rate constant is1.32×10 3 (mol/L)1.9·s 1 at 50 ℃ and activation energy of the reaction is
(113.9±2.4) kJ/mol. The influence of ionic strength on the reaction is negligible.
Reaction Between Mono-methylhydrazine and Tc(Ⅶ)
in Nitric Acid Medium
WEI Yan, PAN Yong-jun, JIAO Hai-yang, CONG Hai-feng,
ZHENG Wei-fang, JIA Yong-fen
Methyl hydrazine (MMH) is a supporting reagent used in the Purex process in order to eliminate
nitrous acid in the system. The reaction between MMH and Tc(Ⅶ) in nitric acid medium was studied by
extraction method. The influences of temperature, acidity, the concentrations of MMH and pertechnetate
on the reaction is investigated. The results indicate that the reaction period is composed of three stages,
induction period, fast reaction period and the termination of the reaction.
The length of the induction period is related to the acidity, the concentration of MMH, and that of
Tc(Ⅶ) in nitric acid solution. The rate equation of the induction period is found as follows:
－dc(Tc(Ⅶ))/dt = k1 c0.64(H+) c0.45(MMH) c(Tc(Ⅶ))
－
－
where k 1 ＝ (0.029±0.00 2 ) (mol/L) 1.09·h 1 at 40 ℃ and 3.0 mol/L of nitrate concentration. The
activation energy of this stage Ea1 is (56.5±0.2) kJ/mol.
After induction period the reaction comes into the period of fast reaction. The rate equation in this
period is found as follows:
－dc(Tc(Ⅶ))/dt = k2 c0.47(H+) c0.22(MMH) c(Tc(Ⅶ))
－
－
where k2＝(0.186±0.002) (mol/L) 0.69·h 1 at 40 ℃. The activation energy of this stage Ea2 is (51.6±0.4)
kJ/mol. The ionic strength has no influence on the reaction rate.
From the above results it is seen that the reaction rate between methyl hydrazine and heptavalent
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Annual Report of China Institute of Atomic Energy 2006
technetium is very slow, and the presence of heptavalent technetium has no great influence on the
consumption of methyl hydrazine.
Reaction of N, N-Dimethylhydroxylamine and Tc(Ⅶ)
in Nitric Acid Medium
WEI Yan, JIAO Hai-yang, PAN Yong-jun, CONG Hai-feng, ZHU Guo-hui, JIA Yong-fen
N, N-dimethylhydroxylamine (DMHAN) is the reductant used in the Purex process study. The
reaction of Tc(Ⅶ) and DMHAN in nitric acid medium was researched by extraction method under
different temperature, acidity, the concentrations of DMHAN and Tc(Ⅶ). The results indicate that Tc(Ⅶ)
is not reduced by DMHAN under different acidity at temperature of 30 ℃ and 40 ℃ and different
concentration of DMHAN at 40 ℃ in 200 h..
From the above results it is seen that the consumption of DMHAN in nitric acid by Tc(Ⅶ) can be
ignored.
Stability of N, N-Dimethylhydroxylamine in Nitric Acid Medium
WEI Yan, CONG Hai-feng, JIA Yong-fen
N, N-dimethyl hydroxylamine (DMHAN) is the reductant used in the Purex process study. Its
stability directly influences its application in the Purex process. DMHAN was synthesized, the purity of
synthesized DMHAN was analyzed to be 99%, and the synthesized DMHAN meets the needs of the
experiment. A titration method for determination of the concentration of DMHAN was established based
on the potassium dichromate titration after the ferric oxidation.
The ratio of DMHAN to ferric during the oxidation of DMHAN is determined as 1∶4. Methanol,
formaldehyde, and formic acid, which are possible oxidized products of DMHAN, do not influence the
result of analysis. Using this titration method, the stability of DMHAN in nitric acid was studied. The
decomposition of DMHAN in nitric acid depends on temperature and the concentration of nitric acid. The
decomposition of DMHAN is lower than 10% within 100 h when the temperature is lower than
35 ℃ and the acidity is lower than 3.0 mol/L. DMHAN is decomposed quickly when the temperature is
higher than 35 ℃ and the acidity is higher than 3.0 mol/L. Decomposition of DMHAN produces NO.
Reaction Kinetics Between Mono-methylhydrazine and Nitrous Acid
WEI Yan, CONG Hai-feng, JIAO Hai-yang, PAN Yong-jun, JIA Yong-fen
Mono-methyl hydrazine is one of supporting reagents in the Purex process in order to eliminate
nitrous acid in the system. The research on the reaction between them is not found in the literature so far.
In order to avoid the possible effect of nitric acid, the oxidation of mono-methylhydrazine by nitrous acid
FUNDAMENTAL AND APPLIED FUNDMENTAL RESEARCH·Radiochemistry and Nuclear Chemistry
161
in perchloric acid medium is researched by spectrophotometric method at first. The influences of acidity,
concentrations of methyl hrdrazine and nitrous, and temperature on the reaction rate are studied. The rate
equation is found as follows:
－dc(HNO2)/dt=k c0.94(H+) c1.11(MMH) c(HNO2)
－
－
where k=(46.02.7) (mol/L) 2.05s 1 at 4.5 ℃ and is 0.5 mol/L of perchlorate concentration. The
corresponding activation energy of the reaction is Ea=(42.4±0.1) kJ/mol.
Then the reaction between methyl hydrazine in nitric acid medium is also investigated by the similar
method. The influences of acidity, temperature, and the concentrations of nitrate, methyl hydrazine,
nitrous acid on the reaction is studied. The reaction rate equation in nitric acid medium is as follows:
－
－dc(HNO2)/dt=k c(H+) c1.14(NO3 ) c1.08(MMH) c(HNO2)
－
－
where k=(1152) (mol/L) 3.22s 1 at 2.6 ℃ and 0.5 mol/L of nitrate concentration. The corresponding
activation energy of the reaction is Ea=(37.8±0.1) kJ/mol.
－
From above mentioned two rate equations, it is seen that NO3 participates in the reaction in the
nitric acid medium. The rate constant in nitric acid medium is higher than that of in perchloric acid
medium. Activation energy Ea in nitric acid medium is lower than that of in perchloric acid medium, and
it suggests that the presence of nitric acid is advantage to the elimination of nitrous acid by methyl
hydrazine. From the research above, we can see that methyl hydrazine can react with nitrous acid very
quickly in nitric acidmedium, and the nitrous acid in the system can be eliminated by methyl hydrazine.
Stability of Monomethyl Hydrazine in Water and Nitric Acid
LI Gao-liang, HE Hui, CHEN Hui, TANG Hong-bin
The stability of monomethyl hydrazine in water and nitric acid was studied. The effects of some
factors on the spectrophotometric analysis of monomethyl hydrazine were investigated.
The results indicate that little effects were made to the analysis results, when there is a little amount
of nitric acid, nitrous acid, methyl alcohol, formic acid, formaldehyde, methylamine, N,N-dimethylhydroxylamine or ferrous iron in the analysis system. Molar absorption coefficient is found to be about
－
－1
3.06×103 L·mol 1·cm
at 20 ℃, and hydrolysis velocity of monomethyl hydrazine is different under
different temperature or concentration of nitric acid. Increasing the concentration of nitric acid or
decreasing the temperature is propitious to the stability of monomethyl hydrazine. The stability of
monomethyl hydrazine is affected by many factors, which will be studied thoroughly in future.
Synthesis of Dihydroxyurea and Its Possible Application in Purex Process
YAN Tai-hong, ZHU Jian-min, ZHANG Yu, XIAN Liang, ZHENG Wei-fang, YE Guo-an
In the development of advanced Purex process which have been expected to reduce costs and lessen
environmental impact, one option for advanced Purex flowsheets is to adopt a new reductant in the U/Pu
split. So we synthesized a new reductant-dihydroxyurea (DHU) through the reaction of the nontoxic bis
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Annual Report of China Institute of Atomic Energy 2006
(trichloromethyl) carbonate (BTC) with hydroxylamine (yield: 40%). The product is characterized by
elemental anal, FT-IR, 1HNMR, 13CNMR and MS.
Its acid stability and thermic stability experiment results show that at 15 ℃ DHU is stable in 02.5 mol/L HNO3 when being placed for 100 h; At 50℃, DHU decomposed to 91%, 72%, 63%, 31% in 0.5,
1.0, 2.0, 2.5 mol/L HNO3 solution; At 90 ℃, DHU decomposes readily when the concentration of HNO3
is over 2.0 mol/L. DHU was determined colorimentrically with alkali ethanol-water solution. Besides, the
reaction between DHU and FeCl3 in water and ethanol is studied, respectively. The results show that DHU
can reduce Fe(Ⅲ) to Fe(Ⅱ) quickly, and it means DHU can reduce Pu(Ⅳ) to Pu(Ⅲ) thermodynamically.
All the results show that the application of DHU to the U/Pu split in the Purex process is possible.
Synthesis of Zirconyl Pyrophosphate and Study
on Adsorption Property to Cesium
SONG Feng-li, LIN Can-sheng, WANG Xiao-rong, CUI Yu-guo
Zirconyl pyrophosphate and zirconyl molybopyrophosphate were synthesized, and the adsorption
property to cesium was experimentally studied for zirconyl pyrophosphate synthesized at different
conditions. The synthesized samples with the best adsorption property were analyzed and characterized.
The comparison absorption properties between zirconyl molybopyrophosphate with the best adsorption
and zirconyl pyrophosphate were performed.
Results show that adsorption properties to cesium have little discrepancy for zirconyl pyrophosphate
synthesized in different conditions. The zirconyl molybopyrophosphate shows the best adsorption
property when the ratio of pyrophosphate to molybdate is 8 to 1 and zirconyl is enough. Compared with
zirconyl molybopyrophosphate, zirconyl pyrophosphate can be used within a larger range when the
distribution coefficient is appropriate. The ion exchange capacity of zirconyl pyrophosphate is higher than
that of zirconyl molybopyrophosphate, the chemical stability of zirconyl pyrophosphate is similar to that
of zirconyl molybopyrophosphate.
Zirconyl pyrophosphate is amorphous porous compound with pore size of about 1.5 nm, the fraction
of pore size of greater than 20 nm is little, and the specific area is 180 m2/g. There are O－P－O, Zr－O
and －OH in the molecule structure, the chemical formula is (3ZrO·2HP2O7)n·8.6nH2O. It has good
thermal stability.
For the zirconyl pyrophosphate-cesium system, the adsorption equilibrium time is 0.5 h; the adsorption distribution coefficient decreases with the temperature increasing; after adsorption equilibrium at the
2 mol/L HNO3 and 12 ℃ was came, the desorption rate is 46.7% and 62.4%, respectively by 5 mol/L and
10 mol/L HNO3 solution. If desorption temperature increases the desorption rate will be larger. In
dynamic tests zirconyl pyrophosphate shows good adsorption property to cesium, and desorption of
cesium is entire of 8 mol/L HNO3 and 60 ℃.
The adsorption of zirconyl pyrophosphate to cesium accords with Langmuir adsorption isotherm, the
adsorption heat is －34.4 kJ/mol. The adsorption mechanism is that the hydrogen ions in hydroxyl are
exchanged by cesium ion.
In the dynamic tests with the mixed fission products solution (2 mol/L HNO3), 137Ce in solution is
almost all reclaimed, the decontamination factor of 137Ce to 95Nb is 83, 137Ce to 95Zr is 380, 137Ce to 106Ru
is 1 500 and 137Ce to 144Ce is 3 700.
FUNDAMENTAL AND APPLIED FUNDMENTAL RESEARCH·Radiochemistry and Nuclear Chemistry
163
Analysis of Nitrous Acid in Spent Fuel Reprocessing Process
CONG Hai-feng, JIA Yong-fen, JIAO Hai-yang
In the high-enriched uranium spent fuel reprocessing process, too high concentration of nitrous acid
in 1AP may destroy the reductant in 1B settler, and cause difficulty for the separation of uranium and
plutonium. The accurate analysis of HNO2 concentration in 1AP is of great importance for the control of
technical process.
Spectrophotometric method was used for the determination of nitrous acid concentration. In this
method, the medium is HNO3 with pH of 1.0-2.0. Nitrous acid reacts with p-aminobenzene sulfonic acid,
N-(1-naphthyl) ethylenediamine to form water soluble compound with reddish violet dye and maximum
absorption wave length is 545 nm as well as the molar absorption coefficient is 6.24×104. Beer’s law is
obeyed in the range of 1-38 mg/25 L of HNO2 concentration. The method has been used for the
concentration determination of nitrite in the simulative sample of 49-3 process. Aluminum ion, nitric acid
and uranium nitrate has no influence on the analysis. The results are satisfactory, which means that it can
be used for the concentration determination of nitrous acid in spent fuel reprocessing process.
Research and Development of Mixed-Settler Extractor：
Equipment of Extraction and Separation Spent Fuel Reprocessing
CHANG Shang-wen, LI Hui-rong, JIAO Hai-yang
The present study concerns in the development of mixed-settler extractor in Purex process in order to
treat the spent fuel from research reactor. The development is based the extractor used to treat power
reactor spent fuel, and certain advanced design was done.
1) Not only the main framework of the extractor, but also the extraction method that aqueous phase
mixed with countercurrent organic phase, and the mechanical agitating method driven by the microelectromotor keep basically unchanged compared with the former. For the groove, the volume of the
agitating room is 5 mL, the separating room 12.5 mL, respectively. Especially, for the 10 grades extractor,
added a groove of the agitating room 8 mL, the separating room 20 mL, respectively.
2) According to the technologic requirement, the grades of the extractor was exchanged, adding the
18-grades, 14-grades and 12-grades.
3) The illumination system was improved by the low-heat LBD instead of the high-heat incandescent
light to reduce the effect of extracting and separating caused by the radiation.
4) The bottom frame of the groove is made of the square iron instead of former angle iron so that it is
simply and easily produced, also convenient for arranging the signal line and feeding plastic tube.
5) Due to using involute rolling tooth method instead of former cutting tooth method to produce the
gears of the agitator, the meshing precise has been greatly improved, the central tolerance and the vertical
tolerance has been sufficiently ensured and the agitating effect to the mixture caused by the meshed gear
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Annual Report of China Institute of Atomic Energy 2006
has also dramatically been decreased.
6) The shape of the spindle has been improved by the variable diameter spindle with axial edge
limiting the position of the two bearing installed instead of the former invariable diameter spindle so as to
ensure the central tolerance and the agitating efficiency better.
7) The shape of the channel ban of the aqueous’s doorway that located in the mixed chamber has
been modified to be arc, therefore, the flowing resistance of the aqueous phase can be decreased and the
interphase deposition can be reduced.
8) The instantaneous sampling device adopted electromagnetic three-way valve instead of the former
slip sampling operated more convenient.
9) All grades sampling device that is made of the organic glass instead of the former made of the
stainless steel was more simple and more convenient to be operated by the manipulator.
Now, the whole set of the equipment has been completely installed, preparing for the studying of the
extractive dynamics.
Adsorption of 90Y on Experimental Vessel Wall
SONG Zhi-jun, DING You-qian, ZHANG Sheng-dong, CUI An-zhi, YANG Zhi-hong
In the experiment about 90Sr-90Y, the lost 90Y is often found. The reason may be adsorption of 90Y. So,
it is of great importance to study the adsorption behavior of 90Y on the common materials and put forward
the method to avoid it.
It was studied the adsorption of element yittium on the test tubes made of polyethylene,
polypropylene and glass under different pH solutions. 90Sr was obtained by HDEHP extraction from
HLLW. The solutions were made of 0.1 mol/L NaNO3 and pH values of 0.045, 1.23, 1.94, 3.02, 4.01, 4.92,
5.99, 7.01, 7.83, 8.98, 9.97, respectively. The solutions were added to the test tubes made of above three
materials, and the tracer 90Sr was added, too. After two weeks, 90Sr and 90Y achieved to equilibrium. The
tubes were counted on NaI(Tl) detector under the threshold of 150 keV, when the efficiency of 90Sr was
about zero. Therefore, the counts all came from 90Y. Suppose the count rateis A. Then the solutions were
pulled out. The according solutions were added to ensure the identical counting condition and counted
immediately. Suppose the count rate is B. The tubes were counted again after 10 days, and found the
decay of counts is fit to the decay of 90Y, which made out the nuclide absorbed on the wall of the vessel is
90Y,
not 90Sr. So, the adsorption rate of 90Y is B/A×100％.
The results are shown in Fig. 1. It is seen that: 1) For the three materials, the effect of pH on the
adsorption rate of 90Y has a similar tendency. It indicates that this varied trend is not determined by the
material, but affected by the existing form of 90Y. 2) At pH<3, the adsorption on the three materials are all
small. 3) The adsorption ability of glass is much more than that of polyethylene and polypropylene. When
pH<7, the adsorption on the polypropylene is more than that of polyethylene, while pH>7, it is opposite;
the reason for this is not clear. Therefore, in the experiment about
90Sr-90Y,
glass is the worst choice
among the three materials. And to make the pH of solution less than 3 can avoid the adsorption of 90Y.
FUNDAMENTAL AND APPLIED FUNDMENTAL RESEARCH·Radiochemistry and Nuclear Chemistry
Fig. 1
165
Adsorption rate of 90Y on three materials under different pH
◆——Glass；□——Polyethylene；▲——Polypropylene
Measurement of 90Sr in Soil Samples With a Pure Instrumental Method
SUN Hong-qing, ZHANG Sheng-dong, MA Peng, TANG Pei-jia
A pure instrumental method of 90Sr determination in soil samples is developed in order to meet fast
measurement of batch soil samples. Gamma-ray spectrum of soil samples and the bremsstrahlung effect
from
90Sr-90Y
beta-radiation is measured by 3×3 NaI(Tl) Gamma-ray spectrometry. We choose the
energy range 70-300 keV as ROI.
The contents of radionuclides in soil samples are determined by HPGe Gamma-ray spectrometer. The
Influence affects of radioisotopes for bremsstrahlung effect is measured by 3×3 NaI(Tl) using standard
samples of the radioisotopes. We can get the residue bremsstrahlung effect of
90Sr-90Y
by subtract the
Influence of radioisotopes.
The detect efficiency of NaI (Tl) for bremsstrahlung effect of
radionuclides are not present,
90Sr
90Sr-90Y
is 0.112%. If interfering
concentrations of 0.29 Bq/g can be determined by now.
Progress on Study of 93Zr Separation
YANG Jin-ling, ZHANG Sheng-dong, CUI An-zhi
93 Zr,
(T1/2=1.53×106 a), is a long-lived pure β-particle-emitting radionuclide with energy of
60.6 keV (97.5%) and 91.4 keV (2.5%). It is produced by nuclear fission and neutron activation of the
stable isotope of 92Zr. As it has high fission yield among all the fissionable materials, it should be paid
more attention to when high-level radioactive wastes are dealed with. But up to now, there are few reports
about 93Zr separation method and there is deficient in nuclear data of 93Zr. In order to handle the waste and
supply samples for measuring its nuclear data, a radiochemical method needs to be developed in order to
separate 93Zr from the solutions.
A silica gel adsorption method is choosen to separate Zr, because this method is useful, simple and
especially, it has high selectivity for adsorption of Zr. Experiments show that Cs, Sr, Mn, Co have no
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Annual Report of China Institute of Atomic Energy 2006
significant adsorption in silica gel. With increasing of the acid concentration, the adsorption of Pu and U
in silica gel are decreasing. Also, the elute solution is common and easily to be got.
First, it was tested the adsorption and deadsorption behavior of stable Zr on silica gel with spectrophotometry assay. The column (4 mm diameter, 10 cm length) was made of glass. And the column was
conditioned with 1 mol/l HNO3. Then a sample, which is 1 mol/L HNO3 solution and contions stable Zr,
was loaded to the column with 1 mol/L HNO3. The adsorbed Zr was eluted with 10 mol/L HNO3. Results
show that the adsorption and elution are quantitative in the range of allowable error. Secondly, 95Zr was
separated from uranium fission products with the same method and the radio- chemical yield is greater
than 99%. The decontamination factors are 2.13×103, 1.18×104, 1.54×104, 4.3×102 for
152Eu
137
Cs,
85
Sr, Pu,
respectively. But they still did not satisfy our demand. So steps of stripping and re-extracting using
TBP were added. Finally, using certain steps 93Zr from test fuel element was separated. The solute about 1
mL was loaded to the column and the column was washed with 23 column volume of 1 mol/L HNO3.
Then 93Zr was eluted with 10 mol/L HNO3. The solution after stripping and re-extracting using TBP was
last loaded on the second silica gel column. Repeat the steps of the column separation. The elutriant was
measured by HGPe detector and liquid scintillation analyzer. The results show the decontamination of the
γ-emitting are almost complete. And there are some counts in low energy range of liquid scintillation
analyzer. But we should do more work to determine it is 93Zr or not. In addition, the product is 10 mol/L
HNO3 solution with volume of 10 mL. It is not very satisfying with too high acid and too large volume.
So the work should be improved in the near future.
Separation of 107Pd by Chromatographic Method With DMG Resin
LIANG Xiao-hu, ZHANG Sheng-dong, MAO Guo-shu, SUN Hong-qing
107Pd
is a long lived fission product, which is a pure β-emitter with a maximal energy of 33 keV and
a fission yield of 0.14%. Present work researches and develops a free-carrier radiochemical separation
procedure of
107Pd
from mixed fission products in order to meet the requirement of the measurements of
nuclear data especially the measurement of its half-life.
For the separation of palladium, column chromatographic method has its advantage over the others
on decontamination, operation safety concerned in the high-level liquid waste. Resins adsorbed some
chelated regent have high selectivity to the objects, and the dimethylglyoxmine (DMG) is an excellent
chelated regent in separating and determining palladium, so we adopted column chromatographic method
with DMG in the resin as the column stuffing .
The high-level liquid waste, raw solution, was converted to the medium of 1 mol/L HNO3, then
loaded on a column filled with AmberliteXAD-7 resin impregnated by 1% DMG-mathanol solution. After
eluting with 1 mol/L HNO3, the palladium-DMG complex was dissolved in the methanol as desorption
reagent. The desorption solution was evaporated and dissolved by chloroform. The organic phase
containing Pd was washed twice with 1 mol/L HNO3 to remove the impurity, then evaporated and
dissolved by aqua regia. After converted to 1 mol/L HNO3 medium, the column separation was again
FUNDAMENTAL AND APPLIED FUNDMENTAL RESEARCH·Radiochemistry and Nuclear Chemistry
167
performed.
We use
109
Pd and many other radionuclides as tracers to determine the recovery and the decontami-
nation factors of the procedure, and the procedure was checked by the dissolved test fuel element of
Qinshan Nuclear Power Plant. The average recovery of the whole procedure is about 30%, and the loss of
107
Pd mainly happened in the steps of chloroform extraction and medium conversion. The procedure have
very high decontamination factors of more than 2×1010 to α and β nuclides and more than 2×108 to
γ-emitting nuclide 137Cs. Using this procedure we can separate the 107Pd with the purity to meet the liquid
scintillation measuring. However, the content of 107Pd in separated sample is mush low than predicted one,
and it may be due to the formation of the alloy which can not be dissolved by HNO3.
Discussion of Data Difference Among Measured Thermal
Neutron Cross Section of 135Cs
WANG Xiu-feng, ZHANG Sheng-dong, DING You-qian, SUN Hong-qing,
GUO Jing-ru, CUI An-zhi, YANG Lei
Fission product
135Cs
emits pure β rays, it has a half life of 2.3×106 a and a yield of 6.53% in
235U
fission. It’s one of the most important nuclides for high-level waste disposal.
We used relative fission yield method to measure the thermal neutral cross section of 135Cs in present
work. Based on the accurate fission yields of 137Cs and 135Cs, the number of 135Cs atoms can be calculated
by the number of 137Cs atoms in the fission products to as avoid the measurement of the number of 135Cs
atoms. 197Au and 55Mn were selected to serve as neutron fluence monitor when 135Cs was activated. HPGe
detector was used to measure the radioactivity of 136Cs from the activation of 135Cs.
We obtained
135Cs
by irradiating
235U
targets. Each target contains about 100 μg
2×1013
were irradiated for 7 d at the neutron fluence rate of
－2
235U.
The targets
－1
cm ·s , and were cooled them for several
months. Then the 135Cs was separated from mixed fission products, and again activated for 8 h. After the
irradiation the radioactivities of
198Au
and
56Mn
from monitor
197Au
and
measured at once to calculate the neutron fluence. The radioactivities of
measured in order to calculate the thermal neutral cross section of
135Cs
55Mn,
136Cs
respectively were
and
137Cs
were also
based on the fission yields and
neutron fluence.
Measured thermal neutron cross sections of 135Cs are listed in Table 1. The measured value from this
work is obvious less than that from other authors.
Table 1
Measured thermal neutron cross section of 135Cs
Author, year
Method
1028σ0/m2
Sugarman，1949
Radiochemical
14.5±4
Baerg et al，1958
MS
8.7±0.5
Hatsukawa et al，1998
MS
8.3±0.3
This work
Relative fission yield
2.67
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Annual Report of China Institute of Atomic Energy 2006
The A=135 and 137 mass chains are shown in the Fig. 1.
Fig. 1
A=135 and 137 mass chains
Fig. 1 shows that the independent yield of
However, the thermal neutron cross section of
135Cs
135Xe
is very low, most of it is from the decay of
is up to 2.6×10
－22
135Xe.
m2. At high neutron fluence rate,
the activation reaction of 135Xe+n→136Xe will decrease the production of 135Cs. The uranium targets were
－
－1
irradiated for 7 d at the neutron fluence rate of 2×1013 cm 2·s
calculated result shows that the 2/3 of
135Xe
value closes to the ratio between yields of
show the
135Xe
yield value of
1011
－2
－1
cm ·s
atoms consumed by
135 Cs
in this work. At above condition the
is consumed by activation of
135Cs
135Xe+n→136Xe,
and this ratio
from MS methods and this work. The calculation results
135Xe+n→136Xe
must be controlled in order to obtain an accurate
by relative fission yield method, and the neutron fluence less than 1.0×
is necessary.
Development of Target (Source) Preparation Technique
With Pulse Electroplating and Direct Current Plating
YANG Chun-li, SU Shu-xin, ZHANG Sheng-dong
In recent years, in order to research the chemical behavior of heavy element, targets of actinide are
prepared to produce the neutron-rich isotopes of heavy element. Since the 1970s, molecular plating
technique has been adopted to prepare targets of actinide which were used for the measurement of fission
cross-section or the accelerator bombardment. Traditional molecular plating used direct current power
which had many disadvantages. In order to overcome these disadvantages and prepare thicker and more
adherent targets of actinide, the pulse electroplating technique was applied. After determining the
optimum conditions of pulse electroplating for U in 2005 and 2006, we try to investigate the three
adjustable parameters which effect the pulse electroplating, including the wave form, frequency,
occupation ratio and the current density. In the first place, we reconstructed the pulse power, considering
the demand of the experiment.
The former pulse power has a top voltage of 110 V which can get a current below 1 mA while the
electroplating was carried out in the N, N-dimethylformamide (DMF). This current is far below the
required current in the molecular plating and confined the improvement of the plating rate. In order to
determine the optimum current density for the pulse plating of actinide and improve the quality of the
FUNDAMENTAL AND APPLIED FUNDMENTAL RESEARCH·Radiochemistry and Nuclear Chemistry
169
coating, we reconstructed the pulse power. Through the reconstruction, the range of voltage and current
was widened and the open time and shut time can be adjusted independently. The Table 1 lists the
parameters of the new and the former pulse power.
Table 1
Voltage
Current
Parameters of new and former pulse power
Frequency
Occupation
Power
Periodic reverse
ton/ms
toff/ms
U/V
I/mA
f/Hz
ratio R/%
current
New power
0-2 000
0-500
0-5 000
0-100
0-500
0-500
Yes
Former power
0-110
0-100
0-2 000
0-100
Non-adjustable
Non-adjustable
No
On the basic of the former research about direct current plating made by Yan Shuheng et al, a
constant direct-current plating was carried out in isopropanol and DMF containing a small amount of
nitric acid respectively. The adherent and homogeneous target of uranium can be prepared by this method.
The surface density changes between 1.2-2.3 mg/cm2. Through changing the current, the influence of the
current density on the yields and the surface density in these two different solvents was investigated. The
results are shown in the Fig. 1 and Fig. 2.
The results show that in both solvents, the yields increase with the current density and arrive at the
top at the 8-10 mA/cm2, respectively 96.11% (isopropanol) and 88.45% (DMF). After that, when the
current density continues to be improved, the yields do not increase because of the release hydrogen and
the quality of coating become worse. The results show that with constant direct-current plating method,
the yield and surface density were all higher in the isopropanol than in the DMF.
Automatic Determination of About 100 mg Uranium
by Developed Potentiometric Titration Based on Conventional Method
LIU Quan-wei, ZHU Hai-qiao, LUO Zhong-yan, LIANG Liang,
HAO Xiao-juan WU Ji-zong
Accurate determination of uranium is significant in the nuclear fuel production, accountancy, nuclear
safeguards and other procedures of nuclear fuel cycle. Electrochemical method based on the redox
titration is conventionally used for the determination of about a gram amount of uranium in different
nuclear fuel materials.
In the conventional method, The U(Ⅵ) is reduced to U(Ⅳ) with Fe(Ⅱ) sulfate solution in
concentrated phosphate acid. Then the excess of Fe(Ⅱ) is oxidized with nitric acid in the existence of Mo.
At last U(Ⅳ) is titrated with potassium dichromate.
In this work automatic determination of about a hundred milligram amount of uranium was
developed based on the conventional method of potentiometric titration of about a gram amount of
uranium.
In this method of potentiometric titration, the suitable concentration of potassium dichromate
170
Annual Report of China Institute of Atomic Energy 2006
solution optimizes the precision of analytical result. The reason is that if the more concentrated potassium
dichromate solution is adopted, the ratio of the end point excursion to the titration volume is bigger which
makes the precision worse, if more diluted potassium dichromate solution is adopted, kurtosis of
potentiometric curve is less which also makes the precision worse. In this work concentration of
potassium dichromate solution was optimized with selection of different concentration of the solution. At
last 2.062 28 g/L of potassium dichromate solution is adopted as the titration solution.
The titration volume of potassium dichromate solution is small because the titrated uranium is only
about 100 mg, so the accuracy of the burette scale is significant for the accuracy of the analytical result. In
this work the burette was scaled for more accurate determination by weighing of purified water according
to the density of the water in the verified temperature.
The amount of reagents used in this titration requires ascertainment according to the amount of
uranium. In this work the experiments for the suitable amount of reagents was conducted. The optimized
amount of reagents is verified through comparing the results of titration.
This titration procedure need be completed within 7 min to avoid the U(Ⅳ) oxidized by oxygen in
the air and make the result on the low side. In this work, the computer control program was optimized
through dividing the titration procedure into fleet titration of preparation and titration of end point with 10
µL every step. The above measure not only makes the procedure be completed within 7 min, but also
ensures the accuracy of the end point.
The China national reference material of U8O3 was determined according to the above optimized
experimental conditions (Table 1). The result shows that the precision value better than 0.01% and
accuracy of the method was verified by the value of China national reference material of U8O3.
Table 1
Content of
Analytical result of national reference material of U8O3
Average content
No.
Content of national reference
RSD of content for national
material of U8O3/%
reference material of U8O3/%
84.711
0.02
RSD/%
uranium/%
1
84.711
2
84.711
3
84.701
4
84.731
5
84.688
6
84.724
of uranium/%
84.711
0.007
Development of Series of Uranium Isotopic Reference Materials
ZHU Hai-qiao, LUO Zhong-yan, HAO Xiao-juan, LIANG Liang, LIU Jun-ling, LIU Quan-wei
A series of standard uranium isotope reference solution were prepared with high purity 235U and 238U.
Basic procedure shows in Fig. 1.
FUNDAMENTAL AND APPLIED FUNDMENTAL RESEARCH·Radiochemistry and Nuclear Chemistry
171
Because the amount of high purity 235U and 238U is not abundant, the method of determination of 100
mg of high purity uranium was developed based on the standard method, for determination of 1 g uranium.
The method was applied to the proficiency testing of inter-laboratory comparisons in China’s nuclear
industries. The results of the inter-laboratory comparisons indicate that the modified method is accurate
and reliable (L19 in Fig. 2). Series of the uranium isotopic reference materials were developed based on
the above method. The result shows that the relative standard uncertainty of these series uranium isotope
reference solution is better than 0.05%. These uranium isotopic reference materials were used to
recalibrate China’s existing 26 uranium solutions, make these solution have lower uncertainty, and trace
to the benchmark of potassium dichromate.
Fig. 1 Procedure of series of uranium isotopic reference materials
Fig. 2
Inter-laboratory comparisons
172
Annual Report of China Institute of Atomic Energy 2006
Determination of Fission Product 148Nd in Irradiated Material
by ID-MC-ICP-MS
WANG Tong-xing, ZHOU Tao1, ZHAO Yong-gang, ZHANG Ji-long
(1 National Institute of Metrology P. R. China)
In present work the determination of
148
Nd concentration in fission products were studied using
MC-ICP-MS. Optimum concentration, measurement time, torch position, nebulizer gas flow rate,
collision gas flow rate and ion lens system were experimentally studied. The precision of measurement for
Nd isotopic ratio is better than 0.01% with the optimum parameters.
The isotope dilution technique was applied for measuring the isotopic ratios of neodymium. There
are two steps in the research work. One is that the concentration of the
144Nd
spike is measured by using
the natural neodymium and the result is 111.17 g/g with relative standard deviation of 0.08%. And the
other is that the 148Nd concentration in the sample is measured using the 144Nd spike and the result is 4.65
ng/g with relative standard deviation of 0.3%. A new measurement method is established in our
laboratory.
A mathematical model was established for the uncertainty evaluation in the measurement. This
model has evaluated the uncertainties contributed by different factors. And the standard uncertainty,
combined standard uncertainty and expanded uncertainty are evaluated.
Determination of Lead in Blood Using Isotope Dilution Multicollector
Inductively Coupled Plasma Mass Spectrometry
WANG Chen, WANG Tong-xing, ZHANG Ji-long, ZHU Liu-chao, CHEN Yan,
CHANG Zhi-yuan, LI Li-li, ZHAO Yong-guang
A method for determination of trace Pb in Bovine Blood by isotope dilution multicollector
inductively coupled plasma mass spectrometry (MC-ICP-MS) was established.
Appropriate amount of highly-enriched
206Pb
(SRM991) spike was carefully added to each samples
by weighing. As for the blood analytical method, a CEM Mars5 microware digester was used for reducing
the organic fraction in the blood. After this process, samples were evaporated to dryness and reconstituted
in 2% HNO3 solution, and then centrifuged. The supernatant was analyzed by multicollector inductively
coupled plasma mass spectrometry.
A blank determination consisted of a small amount of spike added to CEM Mars5 vessel and treated
exactly the same as the samples .The average Pb blank obtained in our laboratory is (5.55+2.09) ng. A
NIST standard reference material (SRM) 955b level 3 (lead in blood) is used to evaluate the accuracy of
lead concentration measurements in blood. The measured lead concentration in the SRM is 207.78 g/mL,
which is in good agreement with the certified value of (205.9±2.1) g/L. The established method was
used for determination the lead concentration of three blood samples, the density of the samples was
FUNDAMENTAL AND APPLIED FUNDMENTAL RESEARCH·Radiochemistry and Nuclear Chemistry
173
calibrated by weighing, the uncertainty of the measurement result was also evaluated. The lead
concentration of the three blood samples are (102.66±5.54), (181.71±3.98) and (304.11±3.90) g/L,
respectively.
Reformation and Upgrade 3070E-X Fluorescence Spectrometer
SONG You, ZHENG Wei-ming, LIU Gui-jiao
3070E-X fluorescence spectrometer of our laboratory was bought from the RIGAKU company in
1989. In the 12 years’ operation, the spectrometer has measured a great deal of samples and provided
several ten thousand analysis dates. But the function of spectrometer has descended obviously in recent
years, the breakdown rate has increased，the data processing system has already dropped behind seriously.
In April 2006, the spectrometer has been reformed and upgraded to deal with these problems. After
upgrade, the system control, the analysis parameter constitution, the data processing and the analysis
result manifestation has been done by the new exterior computer and the report forms printing has been
completed by the wide printer under the Chinese characters environment. The original monochrome CRT
display, the special keyboard and the original floppy drive of 360 ks have been replaced. Because of
reducing the MEMORY plank, the terminal connect plank, the CRT control plank, the CRT adapter plank,
the spectrometer stability has been raised and the breakdown rate has been reduced. For reformed
3070E-X fluorescence spectrometer, relative deviation of the four hundred times copper Kα is 0.51% (A
class is 0.53%), the precision of the twenty times copper Kα is 0.07% (A class is 0.14%), and it has passed
the appraisal and its various signs have fulfilled the standard of the A class instrument.