Search

Neutron total cross sections of natFe, 197Au and natW have been measured at the nELBE neutron time-of-flight facility in the energy range from 0.2 - 8 MeV with an uncertainty due to counting statistics of up to 2 % and a total uncertainty due to systematic effects of 1 %. The neutrons are produced with the superconducting electron accelerator ELBE using a liquid lead circuit as photo-neutron target. By periodical sample-in-sample-out measurements the transmission of the sample materials has been determined using a low-threshold plastic scintillation detector. The resulting effective total cross sections show good agreement with previously measured data that cover only part of the energy range available at nELBE. The results have also been compared to evaluated library files and recent calculations based on a dispersive coupled channel optical model potential.

This report describes recommendations to CIELO (Collaborative International Evaluated Library Organisation) to improve the evaluated cross sections for neutron induced interactions on 16O and 238U. The objective of CIELO is the creation of a world-wide recognised nuclear data file with a focus on six nuclides, i.e. 1H, 16O, 56Fe, 235U, 238U and 239Pu. Within the CIELO project the Joint Research Centre is responsible for the production of evaluated data files for 16O and 238U in the resonance region. The available experimental data and current status of evaluated data libraries for 16O are reviewed and recommendations to improve the present status are given. For 238U a full ENDF compatible resonance file for the resolved and unresolved resonance region is described., JRC.G.2-Standards for Nuclear Safety, Security and Safeguards

The rainbow trout (Oncorhynchus mykiss), an important species in Bulgarian aquaculture, is farmed in different production systems as raceways, net cages etc. The aim of the present study was to evaluate the effect of two different rearing systems on fish production, survival rate, meat chemical, mineral composition and farming economic efficiency of culticated rainbow trout (Oncorhynchus mykiss). The information from a survey on fish production and economic efficiency traits was collected from two national rainbow trout farms using the two commonest fish farming systems: in raceways, Happy Fish Ltd fish farmandinnetcages,ForestGroupLtdfishfarm.Theaverageindividualweightgain(g),totalweightgain(kg), feedconversionratio,productioncostsof1kg fish and the economic efficiency coefficients were determined for the two studied fish farms. The final live weight of rainbow trout in net cages was 0.30 kg vs 0.35 kg in raceways. The average individual weight gain was higher in raceways farming system (0.30 kg) than in net cages farm (0.26 kg). The mortality rate of fish in raceways was considerably lower: only 1% as compared to that in net cages (4%). The feed conversion ratio at the end of the experiment showed identical values for trout in both farms 1.01. The meat water content of fish reared in raceways and net cages was 77.46±0.65% and 74.52±0.52% respectively (P≤0.01).The protein content of fish meat was higher in fish farmed in net cages 18.84±0.29% as compared to fish cultivated in raceways 17.60±0.49% (P≤ 0.05). Meat fat content of rainbow trout, reared in the net cage system was also considerably higher (5.26±0.30%) than the respective parameter in fish farmed in ponds(3.60±0.15%)(P≤0.001).The content of Ca and P washig her in rainbow trout sreared in race ways(138.96±1.12mg.kg-1and2844.32±39.31mg.kg- 1) compared with the values of these parameters of fish in net cages (134.46±1.96 mg.kg-1 and 2690.31±42.81 mg.kg-1) (P≤ 0.05). The K and Na content exhibited the opposite tendency with substantially higher values in trouts farmed in net cages (2658.26±48.75 mg.kg-1 and 671.31±16.16 mg.kg-1) than in fish in raceways (2552.90±39.93 mg.kg-1 and 569.32±13.75 mg.kg-1)(P≤0.05, P≤0.001). The production costs of 1 kg rainbow trout were by 17.27% lower in the Forest Group farm than in the Happy Fish farm. The coefficient of economic efficiency in the net cage farm was by 23.44%higher than that of the race ways production system.

International audience; Cross sections for neutron-induced reactions of Am241 in the resonance region have been evaluated. Results of time-of-flight cross section experiments carried out at the GELINA, LANSCE, ORELA and Saclay facilities have been combined with optical model calculations to derive consistent cross sections from the thermal energy region up to the continuum region. Resolved resonance parameters were derived from a resonance shape analysis of transmissions, capture yields, and fission yields in the energy region up to 150 eV using the refit code. From a statistical analysis of these parameters, a neutron strength function (104S0=1.01±0.12), mean level spacing (D0=0.60±0.01 eV) and average radiation width (⟨Γγ0⟩=43.3±1.1 meV) for s-wave resonances were obtained. Neutron strength functions for higher partial waves (l>0) together with channel and effective scattering radii were deduced from calculations based on a complex mean-field optical model potential, applying an equivalent hard-sphere scattering radius approximation.

Neutron induced capture cross section measurements for 197Au have been performed in the energy region between 4 keV and 80 keV. The experiments have been carried out at the time-of-flight facility GELINA. The prompt capture gamma-rays were detected by two C6D6 liquid scintillators, placed at 12.5 m distance from the neutron source. The shape of the neutron flux was measured with a 10B-loaded double Frisch-gridded ionization chamber based on the 10B(n,alpha) reaction. The total energy detection principle in combination with the pulse height weighting technique was applied. The data have been normalized to the well-isolated and saturated 197Au resonance at 4.9 eV. Special procedures have been applied to reduce bias effects due to the weighting function, normalization, dead time and background corrections. Uncertainties due to normalization, neutron flux and weighting function are 1.0 %. An additional uncertainty of 0.5 % results from the correction for self-shielding and multiple interactions, which have been verified by experiment. Resonance fluctuations have been studied by additional measurements at a 30 m 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 a standard evaluation of the 197Au(n,gamma) cross section that was based on a least squares fit of experimental data available in the literature prior to this work and are fully consistent with the latest average capture cross section obtained in a quasi-Maxwellian spectrum at 25 keV.

Advantages of using algae for wastewater treatment include: low operational cost, possibility of recycling assimilated nitrogen and phosphorus within the algae biomass as a fertilizer, accumulated biomass for biofuel. Our purpose was to study the influence of organic carbon on bioremediation process of wastewater originate from aquaculture with use of microalgae from genera Botryoccocus and Scenedesmus. Algae cultivation was initiated in a bioreactor of 500ml Erlenmeyer flask containing 250ml wastewater. The experiment was conducted in variants without any organic carbon sources and the other with organic carbon source – glucose (1,125g.l-1). Light regime was adjusted at 15:9 h light:dark cycle in an illumination incubator until the end of experiment. The temperature was kept between 25 and 27oC. The pH varied between 6.5 and 7.5 and by this reason it was not adjusted. Species grown in wastewater with added glucose showed a better cleansing effect compared with the same grown in wastewater without any carbon sources. Better growth indicators and faster absorption of wastewater compounds was observed in S. dimorphus.

Microalgae have several advantages, including higher photosynthetic efficiency as well as higher growth rates and higher biomass production compared to other energy crops. The Scenedesmus dimorphus strain was studied by using two media – BBM and 3N-BBM, and its potential for biofuel production was established. The temperature varied between 25 – 27ºC during the experiment. Fluorescent light was used to assure optimal light condition and a photoperiod of 15/9h light and dark cycle was maintained.The duration of the experiment was 25 days. Dry weight, optical density, chlorophyll, carotenoids and total lipids were measured for the biomass evaluation. The received results showed that the maximum vegetative growth was reached after approximately 16 days of incubation. The maximum growth rate during this period was 1.690 mg.l -1 dry weight in 3N-BBM medium, and in BBM medium – 0.960 mg.l -1. The lipid content which we received from the examined strain was 21.6% in BBM medium, and in 3N-BBM – 18.5%.

An ENDF-6 compatible evaluation for neutron induced reactions in the resonance region has been completed for 182,183,184,186W. The parameters are the result of an analysis of experimental data available in the literature together with a parameter adjustment on transmission and capture data obtained at the time-of-flight facility GELINA. Complete evaluated data files in ENDF-6 format have been produced by joining the evaluations in the resonance region with corresponding files from the JEFF-32T1 and ENDF/B-VII.1 library. The evaluated files have been processed with the latest updates of NJOY.99 to test their format and application consistency as well as to produce a continuous-energy data library in ACE format for use in Monte Carlo codes. The evaluated files will be implemented in the next release of the JEFF-3 library which is maintained by the Nuclear Energy Agency of the OECD. The evaluated files will be implemented in the next release of the JEFF-3 library which is maintained by the Nuclear Energy Agency of the OECD., JRC.D.4-Standards for Nuclear Safety, Security and Safeguards

A new evaluation of neutron induced reactions on 197Au nucleus in the energy regions below 500 eV and from 4 keV and 100 keV is presented. Complete evaluated data files in ENDF-6 format have been produced by joining the evaluation with corresponding files from the ENDF/B-VII.1 library. The evaluation in the unresolved resonance region between 4 keV and 100 keV is based on a generalized single-level representation compatible with the energy-dependent option of the ENDF-6 format. The average partial cross sections have been expressed in terms of transmission coefficients by applying the Hauser-Feshbach statistical reaction theory including width fluctuations. The transmission coefficients have been obtained from a combined analysis of the capture cross section resulting from the cross section standards evaluation project and theoretical non-fluctuating cross sections derived from a dispersive coupled channel optical model. The evaluated cross sections have been validated by a comparison with transmission and capture data obtained at the time-of-flight facility GELINA. The evaluated files have been processed with the latest updates of NJOY.99 to test their format and application consistency as well as to produce a continuous-energy data library in ACE format for use in Monte Carlo codes. The ACE files have been utilized to study the effect of the evaluated resonance parameters on results of lead slowing-down experiments. The evaluated files will be implemented in the next release of the JEFF-3 library which is maintained by the Nuclear Energy Agency of the OECD., JRC.D.4-Standards for Nuclear Safety, Security and Safeguards

The relationships among 15 morphometric measurements and carcass weight in European perch (Perca fluviatilis) were examined in connection with sexual dimorphism. The determinated sex ratio was 1:1.3 in the advantage of the male sex. The female perch were larger than male perch by 20,7%, but the carcass weight of the male specimens was by 4,7% better in comparison with the ones measured in female specimens. There were found five morphometric characters that differ between genders: lD1 (1-st dorsal fin lenght) (p≤0.05), lA (anal fin lenght)(p≤0.05), hA (anal fin height) (p≤0.05), lp (pectoral fin lenght) (p≤0.001), lV (ventral fin lenght) (p≤0.05).

The purpose of the study was to determine the dissolved oxygen consumption of rainbow trout, cultivated in raceway. The consumption analysis is based on a process automatic oxygen measurement system and compares the theoretically calculated amount of food for trout feeding based on the flow and oxygen consumption of the cultivated fish with wise used in the trout nutrition practice – calculation of feed amount according to water temperature and individual fish weight. The average amount of oxygen consumed by the fish in our trial measured in an interval of 1 minute was 0.295 mg.l-1. The comparison between the calculated amount of food by the equation σ = 0.054.Q. (O in-O out) and quantity of food used in feeding of rainbow trout based on water temperature and individual fish weight did not show statistically significant differences.