Band 98, Heft 6 -

In order to examine the decontamination behavior of the Pu and fission products (FPs) that contained with the uranyl nitrate hexahydrate (UNH) crystals in the U crystallization process, experiments were carried out using mixed oxide (MOX) fuel dissolver solution. The experiments confirmed that Eu was adequately decontaminated by washing the UNH crystals with a HNO 3 solution. However, Ba crystallized as Ba(NO 3 ) 2 and the washing was ineffective for the decontamination of Ba. High HNO 3 and Pu concentrations in the mother liquor, the decontamination factor (DF) of Cs was low because Cs precipitated with Pu as Cs 2 Pu(NO 3 ) 6 . The Pu clearly showed a reasonable DF because the amount of Pu in the dissolver solution was higher than that of Cs. Almost all the amount of Pu remains in the mother liquor except the one in the Cs 2 Pu(NO 3 ) 6 precipitate.

In order to study the gas-phase chemical behavior of transactinides, an on-line isothermal chromatography apparatus has been developed and applied to separate short-lived technetium isotopes in the form of TcO 3 from fission products. The fission products from a 252 Cf source were continuously and rapidly transported through the capillary to the isothermal chromatography apparatus using the N 2 /KBr gas-jet techniques. Volatile oxide molecules were formed at the reaction zone kept at 900 °C since a trace amount of oxygen existed in the N 2 carrier gas. With the new developed isothermal chromatography apparatus, a selective separation of Tc from fission products was achieved. After isothermal chromatographic separation, 101,103,104,105,106,107,108 Tc were dominantly observed together with their Ru daughters in the γ-spectrum, The chemical yields of 101 Tc, 104 Tc and 105 Tc isotopes with longer half-lives are about 55−57%, and those of 103 Tc, 106 Tc, 107 Tc and 108 Tc isotopes with shorter half-lives dropped down to 25−28%. The adsorption enthalpy of the investigated compounds on quartz surfaces was determined to be −150±5 kJ/mol by fitting the measured retention curves with a Monte Carlo model. The observed species of technetium oxide is attributed to TcO 3 , which is in good agreement with previous experimental results. That means our system worked properly and it can be used to investigate the gas-phase chemical behavior of transactinides.

The present study reports the coprecipitation of gadolinium with calcium sulphate dihydrate, in aqueous solutions of sulphuric acid, at constant ionic strength using a radiotracer technique. The experimental results obtained at ambient temperature, show that the quantity of gadolinium ions coprecipitated in gypsum identified by X-ray diffraction (XRD) and elemental analysis is very small, lower than 4ߙat.ߙ%. The mechanism of coprecipitation of Gd(III) has been discussed, although the elementary processes of the mechanism are not clear. The distribution of gadolinium between precipitate of gypsum and saturated aqueous solutions of H 2 SO 4 has been measured between 30 and 70 °C. Experiments of coprecipitation indicate that the coefficient of distribution of Gd(III) depends on the solubility and nature of solid calcium sulphate phase.

The known IODO-GEN™-method [1] was adapted for radiolabeling of humic and fulvic acids with 131 I. The water insoluble oxidizing agent 1,3,4,6tetrachloro-3α,6α-diphenylglycoluril (IODO-GEN™) forms an iodous ion species (I + ), which undergoes an electrophilic I/H-substitution on aromatic moieties of the humic and fulvic acids. This method offers mild conditions with a lesser extent of oxidative alterations of the target molecule, accompanied by an easy handling due to the virtual water-insolubility of the oxidizing agent. The method was optimized and different techniques were tested for the purification of the radioiodinated humic material. The yield of the labeling procedure varies between 45 and 75% depending on the provenance of the humic material and the applied purification method. A specific activity up to 40 MBq/mg was achieved. Furthermore, the known inherent photo-susceptibility of the iodinated humic substance and the influence of reducing agents were verified. An additional release of 131 I up to 20% and up to 35%, respectively were observed.

CoTreat is a commercial titanate material that is effective for the removal of 60 Co and other activated corrosion product nuclides from nuclear waste effluents. A basic study has been carried out to investigate the uptake mechanism and selectivity of CoTreat material for trace sorption of 54 Mn, 59 Fe, 57 Co, 63 Ni, 65 Zn and 110m Ag. The analyses of the trace sorption isotherms indicate that except for 110m Ag the uptake mechanism for the trace metal ions is surface complex formation. The selectivity of the material for the metal ions studied decreases in the order Fe>Ag>Mn>Co ≈Ni>Zn. Except for Fe, the selectivity thus decreases with the increasing tendency of the cations to hydrolyse.

Radioactive decay is an important subject to take into account when studying the thermo-hydro-dynamic behavior of the buffer clay material used in the containment of radioactive waste. The modern concepts for the multibarrier design of a repository of high level waste in deep geologic formations consider that once canisters have failed, the buffer clay material must ensure the retention and/or delay of radionuclides within the time framework given in the assessment studies. Within the clay buffer, different chemical species are retarded/fixed according to several physicochemical processes (ion exchange, surface complexation, precipitation, matrix diffusion, ...) but typical approaches do not consider the eventuality that radioactive species change their chemical nature ( i.e. phase) thereby affecting their reactive behavior. The radioactive decay of an element takes place independently of the phase (aqueous, solid or gaseous) to which it belongs. This means that, in terms of radionuclide fixation, some geochemical processes will be effective scavengers (for instance mineral precipitation of crystal growth) while others will not (for instance ion exchange and/or sorption). In this contribution we present a reactive radioactive decay model of any number of chemical components including those that belong to decay series. The model, which is named FLOW-DECAY, also takes into account flow and isotopic migration and it has been applied considering a hypothetical model scenario provided by the project ENRESA 2000 and direct comparison with the results generated by the probabilistic code GoldSim. Results indicate that FLOW-DECAY may simulate the decay processes in a similar way that GoldSim, being the differences related to factors associated to code architecture.

A simple method for fitting the values of the experimental breakthrough curves in the form of pulse response obtained in dynamic flow column experiments is presented. It is based on the equation obtained by the analytical solution of a 1-D advection-dispersion equation (ADE) under defined conditions (equilibrium dynamics, linear sorption isotherm, constant bed height, pulse input), where the concentration (or activity) dependence on the number of pore volumes is expressed explicitly. It is shown that the method can be used in the case of validity of a non-linear Freundlich sorption isotherm if the experimental data are fitted by means of a Newton-Raphson multidimensional non-linear regression procedure in which the regression function consists of the above mentioned ADE equation and of the equation for a retardation coefficient including the first derivative of the Freundlich equation. Values of four parameters, namely, Freundlich equation parameters ( nF , kF ), Peclet number ( Pe ) and integration constant ( k int ) are sought in the course of the regression procedure. Applicability of the method is demonstrated in the evaluation of breakthrough curves of the 137 Cs and 85 Sr obtained by dynamic flow column experiments in beds of five different types of crushed crystalline rocks, where synthetic groundwater spiked with both radionuclides is used.

In the study, the activities of uranium 234 U and 238 U in the Vistula River water samples which were collected from November 2002 to October 2003, were measured using alpha spectrometry. In winter, the highest concentration of uranium isotopes and total uranium was in the Vistula River water from Malbork (13.13±0.22 Bq m −3 for 234 U, 12.45±0.21 Bq m −3 for 238 U and 1.02±0.30 mg m −3 for total uranium), and the lowest was in water from Dęblin (1.73±0.07 Bq m −3 for 234 U, 1.55±0.07 Bq m −3 for 238 U and 0.13±0.09 mg m −3 for total uranium). In analyzed river samples uranium isotopes 234 U and 238 U are not in the radioactive equilibrium state. The values of 234 U/ 238 U activity ratio lie between 1.05–1.70. During spring, the highest concentration of uranium isotopes and total uranium was found in the Vistula River water from Malbork (12.36±0.19 Bq m −3 for 234 U, 10.77±0.17 Bq m −3 for 238 U and 0.88±0.25 mg m −3 for total uranium), and the lowest was in water taken from Sandomierz (5.77±0.14 Bq m −3 for 234 U) and Kraków (4.08±0.11 Bq m `−3 for 238 U and 0.33±0.18 mg m −3 for total uranium). The values of 234 U/ 238 U activity ratio lie between 1.15–1.64. In summer, the highest concentration of uranium isotopes and total uranium was found in the Vistula River water samples taken from Malbork (8.22±0.21 Bq m −3 for 234 U, 7.60±0.21 Bq m −3 for 238 U and 0.62±0.29 mg m −3 for total uranium), and the lowest was in water from Sandomierz (6.37±0.12 Bq m −3 for 234 U) and Kraków (3.56±0.19 Bq m −3 for 238 U and 0.29±0.33 mg m −3 for total uranium). The values of 234 U/ 238 U activity ratio lie between 1.08–1.95. In autumn the highest concentration of uranium isotopes and total uranium was in the Vistula River water from Malbork (17.80±0.25 Bq m −3 for 234 U, 15.12±0.23 Bq m −3 for 238 U and 1.23±0.34 mg m −3 for total uranium) and the lowest was in water from Toruń (8.15±0.49 Bq m −3 for 234 U) and Kraków (6.34±0.47 Bq m −3 for 238 U and 0.52±0.78 mg m −3 for total uranium). The values of 234 U/ 238 U activity ratio lie between 1.10–1.74. Annually, the southern Baltic Sea is enriched by about 507 GBq uranium isotopes 234 U and 238 U, with 490 GBq going to the Gdańsk Bay and 16.5 GBq to Vistula Lagoon. The highest surface 238 U runoff was observed in spring (to 1200 kBq km −2 quarter −1 for catchment´s area), the lowest in summer for Bug with Narew catchment´s area to 20 kBq km −2 quarter −1 ). These studies are very important for the inflow estimation of natural and anthropogenic alpha radionuclides to the Baltic Sea.

Results of 63 Ni and 60 Co determination in forest litter samples collected in 2007 in highly contaminated Chernobyl exclusion zone as well as in isolated “ruthenium hot particles” collected in 1986 in Northeastern Poland are presented. In case of bulk samples relatively complicated radiochemical procedure was necessary for nickel separation from matrix elements and other radioisotopes present. The main steps in radiochemical operations were cobalt separation on Dowex 1×8 anion-exchange resin and separation of most of the matrix elements under basic conditions. Nickel was precipitated with sodium sulfide and when dissolved in aqua regia , Ni-DMG complex was formed, extracted with chloroform and back-extracted with hydrochloric acid. 63 Ni activity was measured with a liquid scintillation spectrometer, and the chemical yields were controlled by means of AAS method. A significant correlation between 60 Co and 63 Ni was found for both sets of samples, and the 63 Ni/ 60 Co mean ratio (decay corrected) is comparable for the two sets of samples.

It is argued that in the recent papers by A. Vivier and J. Aupiais (Radiochim. Acta 95 , 471 (2007) and 96 , 385 (2008)) some relevant probability distributions are incorrectly composed. The argument is supported by applying the Feller and Markov formulae.

Recently, the Bayesian approach has been considered in the standard ISO to refine the determination of the decision threshold by taking into account all accessible information such as type A and type B uncertainties. In a previous paper [1] and later a corrigendum [2], we had demonstrated that such treatment was not properly performed and we have developed a complete treatment without simplification, based on the Bayesian approach and Poisson distribution. A new law of distribution of the net counting knowing one experimental determination of the background was thus introduced. Here, we discuss the comments from S. Sterlinski about this law of distribution. All variables in bold and italic are random while all variables in italic style are numbers experimentally obtained after a measurement.