Le comportement de certains radionucléides (RN) anthropiques (137Cs, 238,239+240Pu et 241Am) a été étudié dans des échantillons naturels de sol, d’eau et de sédiments prélevés dans le Massif du Boréon. Dans ce milieu non anthropisé, ces RN restent détectables et proviennent des essais nucléaires atmosphériques (238,239+240Pu et 241Am) et de l’accident de la centrale nucléaire de Tchernobyl (137Cs). Les pollutions radioactives restent en surface dans ces sols non perturbés. Dans les sédiments lacustres, l’apport direct des retombées radioactives est détectable en profondeur car sous l’effet de la sédimentation les RN ont quitté la surface. Les transferts entre ces 2 compartiments naturels ont montré l’importance de l’eau comme vecteur de transport et la prédominance du lessivage par rapport à la lixiviation. Le lessivage transporte les RN des pentes du bassin versant, vers la clairière puis vers les sédiments via la phase aqueuse. Dans les échantillons solides, les RN ont une faible mobilité, 241Am est l’isotope le plus mobile et 137Cs l’isotope le moins mobile. Les isotopes 238,239+240Pu ont un comportement intermédiaire. La mobilité est corrélée au contact de l’échantillon solide avec l’eau, ainsi la mobilité des RN est plus importante dans les sédiments que dans le sol. L’évolution temporelle de la radioactivité n’a pu être décrite malgré un essai basé sur les isotopes de Pb en raison de la complexité du milieu naturel. Deux approches (tests de sorption et analyse structurale de l’eau et du sédiment dopés par spectroscopie d’absorption X et spectroscopie laser résolue en temps) au laboratoire ont permis de mieux comprendre le comportement de Am à travers son analogue Eu. Dans l’eau dopée, la présence de 2 complexes, un inorganique Eu(OH)CO3(aq) et un organique avec les acides humiques, a été envisagée. Les sédiments lacustres ont une importante capacité de rétention avec une cinétique de sorption rapide présageant de la faible mobilité de Am dans ce milieu naturel. / The behavior of certain anthropogenic radionuclides (RNs) (137Cs, 238,239+240Pu, 241Am) was studied in samples of soil, water and sediment collected in the Boreon Massif. In this non-anthropized environment, these RNs are still measurable. They come from nuclear weapon tests (238,239+240Pu and 241Am) and from the Chernobyl nuclear power plant accident (137Cs). Radioactive pollutions stay near the surface in these undisturbed soils. In the lake sediments, direct deposits of the radioactive fallouts are detected in depth due to the effect of sedimentation causing RNs to leave the ground surface. The transference between those two natural compartments has shown the importance of water as a transport vehicle and the prevalence of leaching compared to lixiviation. Leaching carries RNs from the drainage basin slopes, to the clearing and then to the sediment through the aqueous phase. In solid samples, RNs have a low mobility, 241Am is the most movable isotope and 137Cs the less movable. 238,239+240Pu isotopes have an intermediate behavior. Mobility rate is correlated with the contact of the solid sample with water. Thus, RN mobility is more important in sediment than in soil. Temporal evolution has not been performed despite a tentative based on Pb isotopes due to the natural environment complexity. Two approaches (sorption tests and structural analysis of spiked water and sediment by X-ray absorption spectroscopy and time-resolved laser induced spectroscopy) in the laboratory have led to a better knowledge of Am behavior using Eu as an analog. In spiked water, the presence of two complexes, one inorganic Eu(OH)CO3(aq) and one organic with humic acids, has been considered. Lake sediment has an important retention capacity with a kinesis of rapid sorption predicting the low mobility of Am in this natural environment.

No description available.

R.D. Haun. / "January 18, 1957." Based on a thesis, M.I.T. Dept. of Physics, January 7, 1957. / Bibliography: p. 63. / Army Signal Corps Contract DA36-039-sc-64637. Dept. of the Army Task 3-99-06-108 and Project 3-99-00-100.

Richard K. Steinberg. / "June 17, 1949." "Abridged version of a thesis." / Bibliography: p. 16. / Army Signal Corps Contract No. W36-039-sc-32037 Project No. 102B. Dept. of the Army Project No. 3-99-10-022.

A. Roberts, Y. Beers [and] A.G. Hill. / "June 6, 1949." / Includes bibliographical references. / Army Signal Corps Contract No. W-36-039-sc-32037 Project No. 102B. Dept. of the Army Project No. 3-99-10-022.

AbstractIn this study a coincidence circuit composed of Ortec modules with Ge(Li)-NaI(Tl) detectors was utilized. An investigation of the different fractional threshold settings of a Constant Fraction of Pulse Height Trigger was made.Two different isotopes were investigated. A sample of 22Na was used as a prompt source. The half-life of the 0.081 Mev energy levelof 133Cs was studied. This half-life has been reported as being 6.3 nsec. Results were compared with results of a previous study at Ball State University which had used a conventional single channel analyzer and had used the zero crossover point for timing purposes.The best value received for the 133Cs energy state using a slope measurement was 8.12 t 0.25 nsec. Using a centroid shift measurement the best value of the 133Cs energy state was 5.66 nsec.Ball State UniversityMuncie, IN 47306

We combined an ECDL and the fluorescence detection system into a portable frequecy-stabilized laser.We installed an atomic cesium cell inside rather than outside the external diode laser cavity in order to minimize the frequency-stablized laser to palm size.In this way, we improved the mobility of the frequecy-stabilized laser. Moreover, the enhanced intensity of laser inside the external cavity increased the signal to noise ratio of the error signal for feedback control. We used Allan variance as an efficient method to quantify noise of the laser and we found the best value was 2.9954E-12 when the time integration was 90 second and the line width of laser was 200 kHz by beat frequency. This design can be exploited to lock the offset frequency of a femtosecond frequency comb laser, thus being helpful in the reaserch of CEP(carrier-envelope phase) light source.

Through collaborative efforts at Texas A&M University and Sandia National Laboratories, a crystalline silicotitanate (CST), which shows extremely high selectivity for radioactive cesium removal in highly concentrated sodium solutions, was synthesized. The effect of hydrogen peroxide on a CST under cesium ion exchange conditions has been investigated. The experimental results with hydrogen peroxide showed that the distribution coefficient of cesium decreased and the tetragonal phase, the major component of CST, slowly dissolved at hydrogen peroxide concentrations greater than 1 M. A simple and novel experimental apparatus for a single-layer ion exchange column was developed to generate experimental data for estimation of the intraparticle effective diffusivity. A mathematical model is presented for estimation of effective diffusivities for a single-layer column of CST granules. The intraparticle effective diffusivity for Cs was estimated as a parameter in the analytical solution. By using the least square method, the effective diffusivities of 1.56 ± 0.14 x 10-11 m2/s and 0.68 ± 0.09x 10-11 m2/s, respectively, were obtained. The difference in the two values was due to the different viscosities of the solutions. A good fit of the experimental data was obtained which supports the use of the homogeneous model for this system. A counter-current ion exchange (CCIX) process was designed to treat nuclear waste at the Savannah River Site. A numerical method based on the orthogonal collocation method was used to simulate the concentration profile of cesium in the CCIX loaded with CST granules. To maximize cesium loading onto the CST and minimize the volume of CST, two design cases of a moving bed, where the fresh CST is pulsed into the column at certain periods or at certain concentration of cesium, were investigated. Simulation results showed that cesium removal behavior in the pilot-scale test of CCIX experiment, where the column length is 22 ft and the CST is pulsed 1 ft in every 24 hours, was well predicted by using the values of the effective diffusivities of 1.0 to 6.0 × 10-11 m2/s.

No description available.

Darbe apibendrinami duomenys apie cezio-137 kaupimąsi dirvoje ir jo perėjimą į augalus bei gyvulio organizmą. Pateikti šio izoztopo pasiskirstymo ir kaupimosi įvairiuose gyvulių organuose bei audiniuose dėsniai, apžvelgti įvairūs metodai, mažinantys cezio-137 kaupimąsi ir greitinantys jo pasišalinimą iš gyvulių organizmo bei gyvulininkystės produktų. Tirtas pienas, mėsa, bulvės, grūdai ir geriamasis vanduo iš Šakių rajono. Buvo nustatomas 137Cs savitasis aktyvumas ir bendrieji alfa ir beta aktyvumai. Radiometriniai tyrimai atlikti radiacinės saugos centre. / We have summarized the data concerning accumulation of 137Cs in soil and the transition of the radionuclides to plants and animals. The presented survey gives some information about the distribution and accumuliation of 137Cs in different organs and tissues of animals about the possible methods of reducing the amount of radionuclides in the organism of animals and in products of animal origin. There was tested milk, meat, potatoes, grain and drinking water from Šakiai region. There was instituted the specific activity of 137Cs and general alpha and beta activities. The radiometric tests were performed in the Radiation Protection Centre.