Volume 93, Issue 9-10 - NRC-6

The yields of 7 Be from nat C, 27 Al, nat Cu, nat Ag and 197 Au targets and 10 Be from nat Cu, nat Ag and 197 Au targets in alpha- (400 MeV) and neutron- (maximum end-point energy, E 0 = 500 MeV) induced reactions were measured in order to compare them with the photonuclear-reaction yields at E 0 = 1000 MeV. The target-mass dependences of the yields of 7 Be and 10 Be showed very similar trends among alpha-, neutron-, and photon-induced reactions. The fragmentation yields of 7 Be decreased more slowly, and those of 10 Be increased gradually with an increase in the target mass; both yields intersected at an approximate target mass of 125. The exponential increase in the fragmentation-yield ratios of 10 Be to 7 Be with an increase in the neutron-to-proton ratio of the targets suggests that pre-formation of the fragments inside the excited nuclei is strongly influenced by the target properties, such as N / Z . Furthermore, the effect of the incident particle was clearly observed in the yield ratios of 10 Be to 7 Be from the Cu and Ag targets.

The influence of reaction channel on the isomeric cross-section ratio was investigated by analysing the experimental data on the reactions 52 Cr( p , n ) 52m,g Mn, 52 Cr( 3 He, t ) 52m,g Mn, 54 Fe( d , α) 52m,g Mn, 54 Fe( n , t ) 52m,g Mn and 54 Fe( 3 He, α p ) 52m,g Mn over the incident particle energy range extending up to 35 MeV. The influence is most pronounced when the channels differ widely, for example ( p , n ) and ( 3 He, t ) processes, i.e. when the reaction mechanisms are different. The nuclear model calculational code EMPIRE-II described the isomeric cross-section ratio rather well in the case of a simple nucleon emission reaction, but not when complex reaction channels were involved.

We produced 229 Th in the nuclear reaction 232 Th(γ, p 2 n ) 229 Ac, followed by disintegration to 229m,g Th. The 229m Th α-decay was searched for. Alpha-particle events of energy between 4.93 MeV and 5.05 MeV were observed in the separated thorium sample of β-decay products from an actinium source highly purified from the 232 Th + γ reaction products. The energies of the α-particles coincide with those expected for 229m Th.

A search for the isomeric transition of 229m Th at 3.5 eV was made by photon detection with a low-noise photomultiplier for samples prepared by a rapid chemical separation from the parent nuclide 233 U by means of an anion exchange method. The photon emission caused by the disintegration of 229m Th was not observed for 229 Th nitric acid solution samples. From the experimental results, the limits of the half-life of 229m Th as dissolved in HNO 3 solution are discussed.

The electronic K X-ray energies of pionic atoms were precisely measured on elements ranging from zinc to lead with a low-energy photon detection system. Some differences between pionic and muonic atoms were found in the atomic-number ( Z ) dependence of the energy shift. In the pionic atoms, the energy shift gradually decreases with an increase in atomic number, which is opposite to the trend for muonic atoms. In the low- Z region investigated elements, the energy shifts of K β X-rays were obviously larger than those of K α X-rays.

Chemical studies on element 104, rutherfordium (Rf), at JAERI (Japan Atomic Energy Research Institute) are reviewed. The transactinide nuclide 261 Rf has been produced in the reaction 248 Cm( 18 O, 5 n ) at the JAERI tandem accelerator with the production cross section of about 13 nb. On-line anion-exchange experiments on Rf together with the lighter homologues, group-4 elements Zr and Hf, in acidic solutions have been conducted with a rapid ion-exchange separation apparatus. From the systematic study of the anion-exchange behavior of Rf, it has been found that the properties of Rf in HCl and HNO 3 solutions are quite similar to those of Zr and Hf, definitely confirming that Rf is a member of the group-4 elements. However, we have observed an unexpected chemical behavior of Rf in HF solutions; the fluoride complex formation of Rf is significantly different from those of the homologues. Prospects of extending chemical studies on transactinide elements in the near future at JAERI are briefly considered.

The aim of this work is to illustrate the effect of parameter uncertainty (protolysis constants) in surface complexation modeling. As example the blind prediction of Np(V) sorption onto hematite was selected, applying the Diffuse Double Layer Model (DDLM). None of the p K parameter sets randomly generated within a space of two standard deviations did deliver unacceptable predictions for the distribution coefficients. Thus, the formally large spreading of the p K values as extracted from literature (even after normalization and extrapolation to infinite dilution) is actually not critical. For well-defined mineral systems, provided a suitable database is accessible, the DDLM approach seems to be promising.

In this work we studied the effect of external β radiation ( 90 Sr- 90 Y source with an activity of 7 mCi) on the dissolution rate of non-irradiated UO 2 as a chemical analogue of spent nuclear fuel (SF). The experiments were carried out at three different pH values inside a glove-box in nitrogen atmosphere to avoid oxygen contamination. The MAKSIMA code was used to model the generation of radiolytic products, both molecular species and radicals. The formation of hydrogen peroxide in solution was observed in the experiments, as was predicted by the MAKSIMA code. When H 2 O 2 could be quantified, its concentration was within the range predicted by this code. In addition, the application to our data of an empirical model for UO 2 dissolution in the presence of H 2 O 2 gave similar results. The UO 2 dissolution rates obtained in this work were similar to the UO 2 corrosion rates determined electrochemically and under γ irradiation with a similar dose rate. On the other hand, they were always lower than the ones obtained with "fresh" spent nuclear fuel, probably because in this case the dose rates to the solution are higher and, in addition, more than just β radiation is emitted by the fuel.

A new multitracer production system, which consists of a gas-jet-coupled multitarget system for short-lived radioactive tracers and a gas- and water-cooled target system for intense beam irradiations, has been installed on a beam line of the K540 MeV RIKEN Ring Cyclotron. The performance of the gas-jet system was investigated with 50 radionuclides of 18 elements produced in the 135 MeV nucl. -1 – 14 N induced reaction on nat Cu. The gas-jet efficiencies of the nuclides varying from 61 Cu to 24 Na, except for the chlorine isotopes, show a smooth variation as a function of the mass difference between a product and a target. The multitracers on the nat Ag and 197 Au targets were also produced by the 135 MeV nucl. -1 – 14 N beam with the intensity of 0.7 pμA, which was more than seven times the limit of the previous system.

Cross sections, averaged over a 235 U fission neutron spectrum, of some threshold reactions induced on zinc after short irradiations, have been measured. The studied reactions and the corresponding values are: 64 Zn( n , p ) 64 Cu, (37.4 ± 1.4) mb; 64 Zn( n , 2 n ) 63 Zn, (23.4 ± 2.0) μb; 66 Zn( n , p ) 66 Cu, (0.775 ± 0.079) mb; 68 Zn( n , p ) 68m Cu, (5.32 ± 0.65) μb; and 68 Zn( n , α) 65 Ni, (52.1 ± 2.3) μb, all referred to the cross section of the 27 Al( n , p ) 27 Mg standard reaction, (3.84 ± 0.18) mb. Working values for the resonance integrals of the reactions 70 Zn( n , γ) 71 Zn and 70 Zn( n , γ) 71m Zn, referred to the tabulated value for the resonance integral of the 68 Zn( n , γ) 69m Zn reaction, (0.24 ± 0.03) b, were also obtained. The results were (0.1350 ± 0.0093) b and (0.157 ± 0.029) b, respectively.

A resume is given of radiochemical measurements of nuclear reaction cross sections relevant to the production of some medically important radionuclides carried out at PINSTECH during the last decade. Systematic studies on fission neutron spectrum averaged cross sections of several threshold reactions, like ( n , 2 n ), ( n , p ) and ( n , α), on titanium, ruthenium, europium and dysprosium for the production of 45 Ti, 96 Tc, 153 Sm and 153 Gd are described.

For production of the therapy related Auger electron emitting neutron deficient nuclide 140 Nd ( T 1/2 = 3.37 d) two routes were investigated: the nuclear reaction nat Ce( 3 He, xn ) 140 Nd over the energy range from 15 to 36 MeV and the reaction 141 Pr( p , 2 n ) 140 Nd from 10 to 45 MeV. Some competing reactions leading to other Nd isotopes, namely 139 Nd and 141 Nd, as well as to 139 Ce were also investigated. Thin samples of cerium(IV)-oxide and praseodymium(III)-oxide were obtained by sedimentation and the conventional stacked-foil technique was used for cross section measurements. All the experimental data obtained in this work were compared with the results of theoretical calculations using the exciton model code ALICE-IPPE as well as with literature experimental data, if available. In general, good agreement between experimental and theoretical results was found. The theoretical thick target yields of all the product nuclides were calculated from the measured excitation functions. The theoretical thick target yield of 140 Nd over the energy range E 3He = 35 → 20 MeV amounts to 12 MBq/μA·h and over the energy range E p = 30 → 15 MeV to 210 MBq/μA·h. A comparison of the two 140 Nd-producing reactions is presented.

For production of the therapeutic radionuclide 114m In, proton and deuteron induced nuclear reactions were investigated using the stacked-foil technique on enriched 114 Cd and nat Cd targets up to E p = 36 MeV and E d = 21 MeV. The experimental cross sections of the 114 Cd( p , γ) 115m In, 114 Cd( p , n ) 114m In, 114 Cd( p , 2 n ) 113m In, 114 Cd( p , 4 n ) 111m,g In, 114 Cd( p , α n ) 110m Ag, 114 Cd( p , α) 111m,g Ag, 114 Cd( d , n ) 115m In, 114 Cd( d , 2 n ) 114m In, 114 Cd( d , 3 n ) 113m In, 114 Cd( d , p ) 115g Cd, 114 Cd( d , α) 112 Ag, 114 Cd( p , α n ) 111m,g Ag, nat Cd( p , x ) 114m In and nat Cd( d , x ) 114m In reactions are reported. Thick target yields are derived and different routes for production of 114m In are compared.

A short review of recent data concerning development of production methods of some radioisotopes at FLNR JINR (Dubna) is presented. Nuclear reactions, targets, yields and radiochemical separation procedures for production of highly-pure radionuclides are given.

A method was developed to produce 111 In from an In/In 2 O 3 target, whereby the parent 111 Sn was separated from the target material by means of ion exchange, using AG1-X4 and AG MP-1 anion exchange resins. The chemical separation had to be performed as quickly as possible, to ensure the highest possible yield of the final product ( 111 Sn has a half-life of 35.3 minutes). The 111 Sn is left on the resin to decay to 111 In, which is then eluted from the column. This method ensures that impurities in the final product are kept to a minimum.

72 As-labelled radiopharmaceuticals could be a valuable resource for Positron Emission Tomography (PET). In particular, the long half-life of 72 As ( T 1/2 = 26 h) facilitates the observation of long-term physiological or metabolic processes, such as the enrichment and distribution of antibodies in tumor tissue. This work describes the primary radiochemical separation of no-carrier-added (nca) 72 Se from cyclotron irradiated germanium targets and the development of a polystyrene type solid-phase extraction based 72 Se/ 72 As radionuclide generator, avoiding the addition of any selenium carrier. The irradiated germanium target is dissolved in HF conc and selenium is reduced with hydrazine dihydrochloride. The nca 72 Se (0) is adsorbed on a solid-phase extraction cartridge, representing the generator column. The 72 As is eluted using various aqueous solvents with 40–60% yield and < 0.1% 72 Se content. To be able to study the radiopharmaceutical arsenic chemistry, subsequent chemical modification of the nca 72 As eluates to nca [ 72 As]AsI 3 provides a versatile radioarsenic labelling synthon.

Non-invasive imaging of genes which are introduced into cells is a useful method for gene therapy monitoring. The labeling of acyclic purine and pyrimidine nucleoside derivatives with fluorine-18 required for the HSV-1 tk imaging approach with positron emission tomography (PET) is described. The methoxytritylated and tosylated precursors were radiolabeled using a K[ 18 F]F/kryptofix 2.2.2™ complex, followed by removal of the protecting groups under acidic conditions and HPLC purification. The radiochemical yields of the 18 F-tracers amount to 5–15% (decay corrected) after a synthesis time of 85–95 min; the radiochemical purity was >98% with an average specific activity of 19 GBq/μmol at the end of synthesis.

Treatment of cancer using boron neutron capture therapy requires the specific accumulation of a relatively high concentration of 10 B into tumor cells or tumor vasculature. In this paper, targeted liposomes were evaluated as carriers of 10 B for this purpose. Na 2 10 B 12 H 12 was successfully encapsulated into liposomes and relatively high amounts of 10 B could be targeted to ovarian carcinoma cells (OVCAR-3) and endothelial cells (HUVEC). This was achieved by coupling a monoclonal antibody or an RGD peptide to the liposomes. The results suggest that targeted liposomes could meet the requirements of successful neutron capture therapy in the near future.

Stabilization of recoil 56 Mn in mixed crystals of MnSO 4 KClO 4 was studied with especial emphasis on isothermal annealing of neutron irradiated target. The results showed that * MnO 4 - yield (%) varies linearly with the increase in perchlorate concentration from 0.100 to 0.500 mol fraction, reaching a maximum value of (89.0 ± 1.1)%. However, the value of intercept ( P 0 ) obtained was (63.0 ± 1.2)%. Isothermal annealing of 56 Mn in the present mixed crystal (MnSO 4 KClO 4 ) of the two molar concentrations ( i.e. , 0.100 and 0.500 mol fraction) of perchlorate was studied at different temperatures for a desired length of time. The retention values increased with increasing temperature and time of annealing for both the samples. The values found for the two concentrations were (67.0 ± 1.0)% and (89.0 ± 1.1)%, respectively, at room temperature. Retention value increased gradually in the beginning but slowed down with a lapse of time and finally attained saturation within about 20 min of heating at 373 K in both cases. Limiting saturations were found to be (86.0 ± 1.0)% (max) for 0.100 molar concentration and (96.0 ± 0.8)% (max) for 0.500 molar concentration. The rate of annealing was found to increase while the extent of annealing decreased. The recoil re-entry process obeys first order rate law and the energies of activation for the system (MnSO 4 KClO 4 ) computed from the classical Arrhenius plots were found to be 0.15 ± 0.05 eV for 0.1 molar ratio and (2.5 ± 0.06)×10 -2 eV for 0.5 molar ratio. The low value of activation energy indicates that there is a recombination of recoil fragments and participation of defect controlled reactions in thermal annealing, leading to higher saturation retention in 0.500 molar ratio. The results obtained are discussed in the light of vacancies created by the dopant and helping in the proposed recoils stabilization mechanism.

The performance, after irradiation at high gamma radiation doses, of the material known under the commercial name SrResin (Eichrom Industries, USA), consisting of a crown ether, 4,4 ′ (5 ′ )-bis( t -butyl-cyclohexane)-18-crown-6, in a solution of 1-octanol absorbed in a polymeric support, has been characterised. The matrix, disposed in columns moistened with dilute HNO 3 or imbibed with 8 M HNO 3 , was irradiated with a 60 Co radiation field at doses from 2 kGy up to 40 kGy, and the separative properties of the columns were measured through the barium–strontium separation. Although the effects of the irradiation are displacement of the elution volumes and an increase of losses of the elements, quantitative separation of barium and strontium is still feasible.

99 MoO 4 2- sorption behavior on 3 commercial hydrotalcites, produced by Sasol Chemie, was studied through batch experiments. Only one of them showed high sorption capacity. This product, the MG70 was identified by XRD diffraction analysis as hydrotalcite (Mg 6 Al 2 (OH) 16 CO 3 ·4H 2 O), while the other two, MG50 and MG30, were identified mainly as magnesium aluminum hydroxide hydrate, MgAl 2 (OH) 14 ·3H 2 O. Calcined MG70 (CMG70) was used to retain about 298.17±8.3 mg of 99 MoMoO 4 2- (MG70- 99 MoO 4 ). When this material was packed in a glass column, the generated 99m Tc was eluted by using NaCl or HNO 3 aqueous solutions. Saline solutions eluted 99m Tc with considerable amounts of 99 Mo while 0.1 M HNO 3 eluted 99m Tc together with a such small amount of 99 Mo that the 99 Mo μCi/ 99m Tc mCi ratios are close to the value recommended by the American Pharmacopeia.

A simple analytical method for simultaneous determination of 41 Ca and 90 Sr in nuclear reactor concrete was developed. Different methods such as acid leaching and alkali fusion were investigated for the decomposition of the samples and for the separation of Ca and Sr from the matrix. Hydroxide and carbonate precipitation was used to separate Ca and Sr from the matrix elements as well as from each other. The chemical yields of the separation procedures for 41 Ca and 90 Sr are 80–90% and the decontamination factors for all interfering radionuclides are more than 10 4 . The detection limits of the analytical method for 41 Ca and 90 Sr are 0.020 and 0.015 Bq, respectively. The methods developed here were used in the determination of 41 Ca in heavy concrete from two concrete cores in the Danish research reactor DR-2.

A new device was developed for the identification of several iodine species in aqueous solution using ion chromatography. Iodide, iodate and molecular iodine can be determined. (The equipment allows both conductivity and radioactivity detections.) The method is applicable for the determination of radioactive iodine contaminations in the cooling water of nuclear power plants.

In the present work, we focused on determination of some important activation products like 238 Pu, 239 Pu/ 240 Pu, 241 Am, and 237 Np, and 90 Sr as a fission product in spent ion exchange resins. The activation products of interest are alpha emitters, while 90 Sr is a beta emitter. Radioactive solutions of 241 Am, 238 Pu, 237 Np, and 90 Sr and pure ion exchange resins were used to prepare artificial samples which were subsequently subjected to an analytical procedure. This consisted of wet destruction of the resins with Fenton's reagent followed by separations using ion exchange. The activities found showed good agreement with calculated values and yields were also very good (above 50%). We also analysed five samples of spent ion exchange resin from the TRIGA Mark II research reactor. Activities of selected radionuclides were below expectations in all samples except in sample 1, which had higher activities of 90 Sr, 137 Cs, 60 Co, 152 Eu, and 154 Eu. Total beta/gamma activity did not exceed the max. permitted level for low level waste.

Kinetics of hydrolysis of tris(thenoyltrifluoroacetonate)thallium(III) in water was studied by back extraction of this moderately labile metal chelate, labelled with 204 Tl, from a water-immiscible organic solvent to aqueous solutions. A function of the distribution ratio of the metal was derived, which linearly depended on time after reaching quasi-equilibrium of chelate partition. Its extrapolation to zero time made it possible to evaluate the partition constant of the chelate. The rate constant of its hydrolysis was determined from the slope. The dependence of the rate constant on pH and on the ligand concentration shows that both acid and base hydrolysis of the chelate studied took place. The approach used can be helpful for determining partition constants of moderately labile metal complexes and the lability of the complexes in aqueous solutions.

A fast and simple method for the determination of 237 Np in soil is presented. The borate fusion decreases the sample pre-treatment time and a TEVA extraction chromatography separates neptunium from uranium and the interfering matrix components. A comparison of the sensitivities of alpha spectrometry and sector field ICP-MS for determination of 237 Np is presented.

In the Badgastein healing gallery aerosol fractions were collected with an 8-stage cascade impactor device. The Fe, Cr, Zn, Co and Sc concentrations were measured by INAA. The values found for Fe, Cr and Co and especially their increase with particle size in the coarse aerosol mode indicated their origin by mechanical grinding of the gallery train tracks or old metal wall brackets. Metal ratios derived from irradiation of a gallery rock sample as well as from wipe tests from the tracks and floor supported these findings. Fe 2 O 3 contents in the particles >1 μm were 19% (1–2 μm) and 70% (2–4 μm); however, also in the impactor stages covering the accumulation mode the rust content was between 1.7 and 5.1%. As these numbers clearly succeeded the Fe content of the rock sample, the Fe origin (as well as the origin of Cr and Co) presumably was again in the tracks and wall brackets; for the metal loads of the smaller aerosol fractions chemical weathering in the mine atmosphere might be the predominant process. Zn was mainly found in the fine particles; it probably had corroded from the zinc coatings of the gallery train.

The transport of water and salt solutions in unsaturated clay and clay rock was measured using the positron emission tomography (PET). The experimental device is described. KF marked with 18 F was used as conservative hydrodynamic tracer to image the flow profiles at different times. Homogeneous and heterogeneous flow regimes were identified. Hydrodynamic model parameters could be determined for the homogeneous regime. The results demonstrate the advantage of PET measurements for investigations of transport processes in geological matrices. They yield quantitative values of the spatial distribution in regard to the flow pattern inside the samples which are important for the validation and parameter estimation of geochemical transport models.