[en] Sources of tritium, both natural and artificial, are covered, the latter including tritium in nuclear reactors. Tritium occurence in the atmosphere, ocean surfaces, ground water, surface water and solar winds is discussed. Detection using liquid scintillation counters is assessed. Tritium as an environmental problem and radiation hazards of tritium in the human body are considered. The experimental procedures for determining the tritium content of the environment are detailed. Experiments included the determination of tritiated water in air, tritium in sea water, in reactor hall air and in reactor dump tank water. The errors are evaluated, results presented and discussed. (U.K.)

[en] Design, modeling and simulation of fluidized bed risers and reactors depend strongly on the knowledge, operational and hydrodynamic characteristics. In this study effort has been made to describe fluidization phenomenon and its application in fluidized beds is briefly explained. The bubble fluidized bed reactors will be introduced and the computerized calculation needed for simulating of a fluidized bed riser with 0.3m diameter and 5 m height will be given. The effect of bed height on the bubble diameter and mass transfer area is calculated and the result are discussed. Operational; conditions of the bed, type and characteristics of the catalyst, has been selected so to suit the production of Maleic Anhyd ric from the n-Butane oxidation

[en] Since we don't have enough knowledge about the Physics of earthquakes. therefore. the study of seismic precursors plays an important role in earthquake prediction. Earthquake prediction is a science which discusses about precursory phenomena during seismogenic process, and then investigates the correlation and association among them and the intrinsic relation between precursors and the seismogenic process. ar the end judges comprehensively the seismic status and finally makes earthquake prediction. There are two ways for predicting earthquake prediction. The first is to study the physics of seismogenic process and to determine the parameters in the process based on the source theories and the second way is to use seismic precursors. In this paper the theory of earthquake is reviewed. We also study theory of earthquake using models of earthquake origin, the relation between seismogenic process and various accompanying precursory phenomena. The earthquake prediction is divided into three categories: long-term, medium-term and short-term. We study seismic anomalous behavior. electric field, crustal deformation, gravity. magnetism of earth. change of groundwater variation. groundwater geochemistry and change of Radon gas emission. Finally, it is concluded the there is a correlation between Radon gas emission and earthquake phenomena. Meanwhile, there are some samples from actual processing in this area

[en] ¹³¹I is one of the most widely used radionuclide in medical diagnosis and therapy, especially for thyroid gland. Separation of ¹³¹I from natural uranium fission product mixtures has been accomplished by sorbing the ¹³¹I on special Platinum-Charcoal sorbent and de sorbing for buffer solution (NaHCO₃ + Na₂S₂O₃). High radiochemical and chemical purity is obtained by this method. By means of computerized codes such as ^WIMSD5^and^CITATION^, the TRR core is simulated and by using ^ORIGEN^code, ¹³¹I production rate is calculated. Experimental results are compared with calculated quantities

[en] In this work an irradiation system for neutron transmutation doping of silicon is proposed. This system is based on using of partial reflector environment surrounding irradiation channel. the influence of type and dimensions of reflectors on the irradiated silicon are investigated and simulated by using MCNP, WIMS and CITATION computer codes. The best system for silicon ingots with the diameter up to 5 cm and up to 10 cm are chosen for Tehran Research Reactor, and the proposed system which belong to 5 cm silicon ingots is constructed

[en] The reduction of U(V I) to U(IV) is of great importance in nuclear and radioanalytical process. Presence of nitrate ions interfere in the reduction process and oxidizes U(IV) to U(V I). In this work it has been tried to minimize the inhibiting effect of nitrate ions by using orthogonal array design to optimize the parameters that affect the reduction of U(V I) to U(IV). The effects of temperature, acid concentration, amount of zinc and reaction time were studied first by three-level orthogonal array design with an OA₉(3⁴) matrix without considering the interaction between the parameters. Exact levels of the parameters were then chosen and experiments were carried out by designing a two level orthogonal array with an OA₈(2⁷) matrix and the interaction effects were taken into consideration. Finally, the optimum conditions for the reduction of U(V I) to U(IV) were proposed

[en] A new method based on adaptive linear neuron (Adaline) is used to estimate the radon concentration in soil associated with the environmental parameters. Analysis of the data obtained from a site in Thailand indicates that our proposed method is able to differentiate temporal variation of radon concentration related to the environmental parameters from those caused by phenomena in the earth (e.g. earthquake). The result also shows agreement between our method and another method based on impulse responses from multivariable time series (complex mathematical equations)

[en] Neutron transmutation doping of silicon (NTD) is one of the important applications in industrial utilization of research reactors. In this paper, the proposed irradiation system based on using a reflecting environment around the irradiation channel of the NTD facility was designed and simulated for irradiation of silicon in the Tehran research reactor (TRR) by using codes such as MCNP, WIMS and CITATION. This system is very simple and does not require conventional methods, such as continuous movement and use of absorbing materials and windows, for flattening of neutron flux in the radial and longitudinal direction. The influence of type and dimensions of reflectors on the irradiated silicon crystal was investigated and also the optimum conditions were determined for TRR for silicon ingots with diameter up to 5 cm and up to 10 cm

[en] Separation of ¹³¹I from natural uranium fission product mixtures has been accomplished by sorbing the ¹³¹I on special platinum-charcoal sorbent and desorbing by buffer solution (NaHCO₃+Na₂S₂O₃). High radiochemical and chemical purity is obtained by this method. Important parameters such as temperature, distillation rate, sorbing and desorbing rates and ¹³¹I separation yields have been investigated

[en] Durable borosilicate glasses for the immobilizing of radioisotopes from nuclear waste streams generated by a radiopharmaceutical production unit are studied. Different boron frits (glasses) and waste-loaded glasses were prepared under various experimental conditions. The effects of some parameters such as melting temperature, cooling procedure and various raw materials were investigated. The best composition of the frits as well as the best glass/waste ratio was determined to optimize the immobilization process. All experiments were performed in non-active bench scale. (author)