Resonance parameters for neutron induced reactions in 106,108,110,111,112,113,114,116Cd have been evaluated. The parameters are the result of an analysis of experimental data available in the ...literature together with a parameter adjustment to transmission and capture data obtained at the time-of-flight facility GELINA. The parameters derived from the GELINA data are in reasonable agreement with those quoted in the literature. From the analysis of the GELINA transmission data a thermal neutron total cross section equal to 2450±40b has been deduced for natCd at 300K. This value is in agreement with results of previous measurements which have been performed at thermal reactor beams using different techniques. It differs by about 1.5% from the value 2413b which was recently deduced from an adjustment to results of an integral experiment. The GELINA transmission and capture data in the low energy region are not fully consistent with resonance parameters recommended in evaluated data files. The impact of the resonance parameters obtained in this work on cadmium transmission factors and on the interpretation of an integral experiment is discussed.
Summary
Klippel‐Trénaunay syndrome is a rare congenital disorder affecting the vascular and lymphatic systems. The clinical presentation can vary widely, but the syndrome is broadly characterised by ...capillary, venous and lymphatic malformations as well as limb hypertrophy. We present the case of a 35‐year‐old parturient who underwent an emergency caesarean section for suspected fetal distress, and describe the anaesthetic management during the peripartum period. Only a small number of similar cases have been described, and the multisystem nature of the condition presents several challenges to both the obstetric and anaesthetic management. The major points of concern to the anaesthetist are haematological, with a tendency to both abnormal bleeding and clotting disorders, compounded by vascular malformations which may present anywhere in the body including the epidural space and airway. Other considerations relate to limb hypertrophy and spinal abnormalities, as well as pulmonary and ocular sequelae and chronic pain. Strategies for safe patient management include early multidisciplinary involvement, and assessment of the presence and extent of any vascular anomalies with advanced imaging techniques. The risk of significant blood loss can be mitigated with antifibrinolytic and uterotonic medication as well as cell salvage, with treatment carefully balanced against the concurrent risk of thrombosis.
Cross section measurements have been performed at the time-of-flight facility GELINA to determine the average capture cross section for
197
Au in the energy region between 3.5 keV and 84 keV. Prompt ...γ-rays, originating from neutron-induced capture events, were detected by two C
6
D
6
liquid scintillators. The sample was placed at about 13m distance from the neutron source. The total energy detection principle in combination with the pulse height weighting technique was applied. The energy dependence of the neutron flux was measured with a double Frisch-gridded ionization chamber based on the
10
B(n,α) reaction. The data have been normalized to the well-isolated and saturated
197
Au resonance at 4.9 eV. Special care was taken to reduce bias effects due to the weighting function, normalization, dead time and background corrections. The total uncertainty due to normalization, neutron flux and weighting function is 1.0%. An additional uncertainty of 0.5% results from the correction for self-shielding and multiple interaction events. Fluctuations due to resonance structures have been studied by complementary measurements at a 30m flight path station. The results reported in this work deviate systematically by more than 5% from the cross section that is recommended as a reference for astrophysical applications. They are about 2% lower compared to an evaluation of the
197
Au(n, γ) cross section, which was based on a least squares fit of experimental data available in the literature prior to this work. The average capture cross section as a function of neutron energy has been parameterized in terms of average resonance parameters. Maxwellian average cross sections at different temperatures have been calculated.
Neutron Resonance Spectroscopy at GELINA Schillebeeckx, P.; Borella, A.; Kopecky, S. ...
Journal of the Korean Physical Society,
08/2011, Letnik:
59, Številka:
2(3)
Journal Article
Recenzirano
The neutron time-of-flight facility GELINA installed at the JRC-IRMM Geel (B) has been designed to produce cross section data for neutron induced reactions in the resonance region. It is a multi-user ...facility, providing a pulsed white neutron source, with a neutron energy range between 10 meV and 20 MeV and a time resolution of 1 ns. The research program concentrates on cross section data needs for nuclear energy applications. In this contribution efforts to improve the quality of cross section data in the resonance region are discussed. These efforts include the implementation of self-indication measurements and improved data reduction and resonance analysis procedures. Due to these efforts accurate neutron-induced cross section data and resonance parameters together with their covariance information can be obtained from thermal up to the unresolved resonance region. KCI Citation Count: 7
The international High Priority Request list notes: - "In the nuclear industry hafnium is used as neutron absorbing material to regulate the fission process. Interpretation of critical experiments ...with UOx fuel conducted by CEA in the AZUR zero-power reactors has shown systematic underestimation of the reactivity worth that may be attributed to an overestimated natural hafnium capture cross section in the epi-thermal energy range"To service the request for improved resonance data a PhD project has:-a) Improved REFIT R-matrix evaluation code.b) Obtained hafnium oxide samples enriched in Hf176, 177, 178, 179 isotopes.c) Gained support from NUDAME and EUFRAT projects.d) Prepared enriched and natural Hf samples.e) Performed capture and transmission Time of Flight measurements at the GELINA linear accelerator.f) Analysed the capture counts to generate yields using AGS and AGL codes.g) Used REFIT to perform least squares analysis of GELINA measurements.(Included previous ORNL, Harwell and RPI transmissions and capture yields.)h) Submitted results to EXFOR.i) Included resolved resonance parameters in JEFF evaluations taking the resolved range to over 1keV. j) Tested evaluations with suitable benchmarks.k) Passed resolved resonance data to CEA Cadarache for unresolved analysis.Resultant Hf evaluations will be included in JEFF3.2. KCI Citation Count: 0
Cross section data in the resolved and unresolved resonance region are represented by nuclear reaction formalisms using parameters which are determined by fitting them to experimental data. ...Therefore, the quality of evaluated cross sections in the resonance region strongly depends on the experimental data used in the adjustment process and an assessment of the experimental covariance data is of primary importance in determining the accuracy of evaluated cross section data. In this contribution, uncertainty components of experimental observables resulting from total and reaction cross section experiments are quantified by identifying the metrological parameters involved in the measurement, data reduction and analysis process. In addition, different methods that can be applied to propagate the covariance of the experimental observables (i.e. transmission and reaction yields) to the covariance of the resonance parameters are discussed and compared. The methods being discussed are: conventional uncertainty propagation, Monte Carlo sampling and marginalization. It is demonstrated that the final covariance matrix of the resonance parameters not only strongly depends on the type of experimental observables used in the adjustment process, the experimental conditions and the characteristics of the resonance structure, but also on the method that is used to propagate the covariances. Finally, a special data reduction concept and format is presented, which offers the possibility to store the full covariance information of experimental data in the EXFOR library and provides the information required to perform a full covariance evaluation.
Transmission, capture and self-indication measurements on^(197)Au have been performed at the neutron time-of-flightfacility GELINA, operated by the European Commission, at EU-JRC-IRMM inBelgium. Part ...of this work was performed within the framework of the EFNUDATproject, with the objective to improve resonance parameters for the ^(197)Au(n, γ) cross section. Resonance parameters, i.e.,energy, spin, parity, neutron and radiation width, have been deduced in theenergy domain up to 200 eV. A comparison with results of measurementsperformed at RPI and at n_TOF shows a good agreement betweenthe data sets. In particular the nuclear resonance parameters, of the firsts-wave resonance at 4.9 eV, extracted at RPI are in very good agreement withthe results of the present work. KCI Citation Count: 0
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