[en] With this method the element whose isotopes are to be separated is selectively excited by laser radiation and the excited isotope is brought in contact with a reaction partner (scavenger). In order to enrich ³⁷Cl vaporous iodine monochloride in acetylene is exposed to the radiation of a rhodamine-GG dye laser resulting in the formation of cis-1.2-iodine-chlorine-acetylene. For enrichment of a chlorine isotope resp. of ³⁴S or ³⁶S there is used a mixture of Cl₂ and SO₂, irradiated by 4200 A resp. 3500-3800 A, and the additive reaction Cl₂ + SO₂ → SO₂Cl₂. With the same mixture one of the oxygen isotopes ¹⁷O and ¹⁸O can be excited. (RW)

[en] Numerically supported safety analyzes generally require a validation of the calculation tools used. This also applies in particular to criticality safety analyzes of transport and storage containers for fissile radioactive materials, the testing and evaluation of which is the responsibility of BASE. Because of the geometric and physical complexity of such containers, Monte Carlo calculations are carried out. The results of such calculations are validated by comparing them with measurement results for critical experiments. The aim of the research project was the evaluation of existing validation approaches and the development of new validation methods in which correlations between the critical experiments used for validation are taken into account. At the beginning of the project, there were approaches for applying a Bayesian updating process to use cases to be validated in criticality safety analyzes and for determining the necessary covariance data. For use in an official environment, however, these were either unsuitable or insufficiently examined for their suitability. In the project, specific solutions and recommendations for action were developed and implemented in software so that the necessary tools for validation are available via a Bayesian update.

[en] With this method the element whose isotopes are to be separated is selectively excited by laser radiation and the excited isotope is brought in contact with a reaction partner (scavenger). In order to enrich Cl vapours iodine monochloride in acetylene is exposed to the radiation of a rhodamine-GG dye laser resulting in the formation of cis-1.2-iodine-chlorine-acetylene. For enrichment of a chlorine isotope resp. of S or S there is used a mixture of Cl and SO, irradiated by 4200 A resp. 3500-3800 A, and the additive reaction Cl+SO SOCl. With the same mixture one of the oxygen isotopes O and O can be excited. (orig./PW)

[en] Short communication

[en] Disappearance of NF₃ and appearance of NF₂ and N₂F₂ in an excimer laser is followed quantitatively with a mass spectrometer. A model for the kinetics is presented. (orig.)

No abstract available

[en] The validation of a code for criticality safety analysis requires the recalculation of benchmark experiments. The selected benchmark experiments are chosen such that they have properties similar to the application case that has to be assessed. A common source of benchmark experiments is the 'International Handbook of Evaluated Criticality Safety Benchmark Experiments' (ICSBEP Handbook) compiled by the 'International Criticality Safety Benchmark Evaluation Project' (ICSBEP). In order to take full advantage of the information provided by the individual benchmark descriptions for the application case, the recommended procedure is to perform an uncertainty analysis. The latter is based on the uncertainties of experimental results included in most of the benchmark descriptions. They can be performed by means of the Monte Carlo sampling technique. The consideration of uncertainties is also being introduced in the supplementary sheet of DIN 25478 'Application of computer codes in the assessment of criticality safety'. However, for a correct treatment of uncertainties taking into account the individual uncertainties of the benchmark experiments is insufficient. In addition, correlations between benchmark experiments have to be handled correctly. For example, these correlations can arise due to different cases of a benchmark experiment sharing the same components like fuel pins or fissile solutions. Thus, manufacturing tolerances of these components (e.g. diameter of the fuel pellets) have to be considered in a consistent manner in all cases of the benchmark experiment. At the 2012 meeting of the Expert Group on 'Uncertainty Analysis for Criticality Safety Assessment' (UACSA) of the OECD/NEA a benchmark proposal was outlined that aimed for the determination of the impact on benchmark correlations on the estimation of the computational bias of the neutron multiplication factor (k_eff). The analysis presented here is based on this proposal. (orig.)

[en] Fractional hyperfine density shifts (fds) for ¹³⁷Ba⁺ (I = 3/2) ions are measured by means of direct optical pumping in noble gas buffers. The results for the fds(¹³⁷Ba⁺, 6s²Ssub(1/2)) in units of 10^-9/Torr (0⁰C) (measured at temperatures between 375 and 395 K) are: +7(7) (He), -74(8) (Ne), -825(80) (Ar), -1,500(200) (Kr), and < -1,600 (Xe). These shifts for the ¹³⁷Ba⁺ ion are considerably more negative than those for the isoelectronic ¹³⁷Cs atom. It is shown that this difference can be explained by taking into account the additional charge induced interaction. The hyperfine splitting frequency of the unperturbed ¹³⁷Ba⁺, 6s²Ssub(1/2) state is extrapolated to ν₀ = 8037741.6(6) kHz. (orig.)

[en] Isotope selective ionization of atoms requires high-resolution dye lasers; often the evaporation of the atomic species is not straightforward. Organometallic compounds are a volatile source of metals at room temperature and even below. The metal part of the organometallic compound is readily obtained using excimer laser-induced photoelimination. Using laser mass spectroscopy with nanosecond and picosecond laser pulses, the authors could identify that more than 95% of CH/sub 3/TeTeCH/sub 3/ can be dissociated by one excimer laser pulse and that the photoproduct Te/sub 2/ dimer shows narrowband spectral features suitable for isotope selective ionization. Isotopically enriched tellurium targets are used for the production of enriched iodine /sup 123/I radioactive isotopes for nuclear medicine. The authors' demonstrate the possibility of a complete laserbased enrichment system for the production of /sup 123/I isotopes suitably enriched to be used for days

[en] We study the influence of calculation parameters on Monte-Carlo generated correlation coefficients of k_eff values for a data set of critical experiments. The correlation coefficients can be used e.g. to reduce conservatism in bias estimations, but generally must be treated correctly if a data set includes correlations. We find that the actual value of the correlation coefficient for a given data set depends on the number of samples and the ratio of the sampling uncertainty to the Monte-Carlo uncertainty of the individual k_eff calculation. We also discuss that the number of input parameters of the model to calculate the k_eff values do not necessarily impact the convergence of the correlation coefficient with increasing sample number. However, we explain how varying the aforementioned parameters lead to different converged results for the correlation coefficients. The conclusion is that a correlation coefficient should not be discussed isolated but with the underlying uncertainties of both, the k_eff estimation and the Monte Carlo sampling approach. The underlying modelling approach of the experimental data has to be described in detail. This should include a sensitivity analysis of the impact of input parameters on the k_eff uncertainty with respect to the modelling approach