ÖZET İlerleyen teknoloji ile proses ve kalite kontrolünün önemi artmış, buna bağlı olarak da nükleer teknikler endüstrinin hizmetine girmiştir. Endüstri alanında seviye ve kalınlık belirlenmesi; hata tespiti, miktar tayini ve karışım zamanı tayini gibi konularda bu tekniklerden yararlanılmaktadır. Önemli bir nükleer teknik grubunu oluşturan radyoaktif izleme teknikleri de uygulama alanları giderek yaygınlaşan bir izleme tekniğidir. Bu Yüksek Lisans tez çalışmasında, radyoaktif izleme tekniği kullanarak farklı malzemelerin karışım zamanlarının tayin edilmesi amaçlanmıştır. Bir başka deyişle viskoziteleri farklı malzemeler üzerinde deneysel olarak çalışarak ve radyoaktif izleme tekniği yardımı ile uygun karışım zamanlarının belirlenmesi hedeflenmiştir. Deneysel çalışmalarımızda 9 adet sıvı malzeme kullanılmıştır. Çalışılan malzemeler seçilirken viskozite ve yoğunlukları birbirinden farklı ve deneysel çalışmalarımızda güvenlik açısından problem olmayacak malzemeler tercih edilmiştir. Bu malzemelerin yoğunluk ve viskozite gibi, özellikleri laboratuvarda deneysel olarak ölçülmüş ve hassasiyet açısından her ölçüm birkaç kez tekrarlanmıştır. Sonuçlarda mukayeseli incelemenin yapılabilmesi için deneylerimizde iki farklı izleme tekniği ile çalışılmıştır. `Radyoaktif İzleme Tekniği` ve `Boya İzleme Tekniği` için kullanılan izleyiciler farklı özellikler taşımaktadırlar. Sözkonusu tekniklerin birbiriyle mukayesesinin minimum hata ile yapılabilmesi için, aynı deney şartlarında, iki tekniği birarada uygulamanın daha yerinde olacağı düşünülmüştür. Bundan ayrı olarak, sürekli sayım ve örnek alma teknikleri çerçevesinde karışım zamanı tayinleri yapılmış ve farklı iki izleme tekniğinin sonuçlan mukayeseli olarak incelenmeye çalışılmıştır. Deney dataları ile her malzeme için ayrı ayrı çizilen grafikler de karışım zamanlan hassasiyetle tespit edilmiştir. Ayrıca, karışım zamanına viskozitenin etkisi belirlenmiş viskoziteye bağlı olarak kalibrasyon eğrisi çıkarılmıştır. vı DETERMINATION OF MIXING TIME BY USING RADIOTRACER TECHNIQUE SUMMARY Tracers can be used to label substances or objects in order to distinguish them, to follow their movement, changes of concentration, distribution between phases, etc. The tracers should allow sensitive and rapid dedection, they should not change the properties of the material. The tracer method has proved to be a very powerful tool in the study of many physical and chemical phenomena. Despite the extensive use of this method, there have been few efforts to define it or clearly enunciate its principles. The tracer method is a technique for obtaining information about a system or some part of a system by observing the behavior of a specific substance, the tracer, that has been added to the system. The tracer method usually involves the use of the tracer to label, or make easily identifiable, a specific phase or part of the system, called the traced material. The tracer method provides information about a system or a part of a system that often could not be otherwise determined. In many applications there is no alternate method for obtaining the desired information. Often when there is a choice of methods, the tracer method is chosen because it reduces the amount of work necessary to obtain the desired information. There are two major requirements for a tracer. First, it must behave exactly like the traced material. Second, it must have one property that distinguishes it from the traced material so that it can be easily dedected in the presence of other material. vuThe tracer method is independent of the distinguishable property used to identify the tracer. Such properties as color, refractive index, conductivity, and density of additive substances have been successfully used in tracing experiments. The radioisotope, or radiotracer, however, is the most universal and practical tracer. The advantages of the radiotracer can best be understood by examining the two primary requisities of a tracer and how the radiotracer meets these requirements. The first requirement is that the tracer can be identical to the traced material. The smallest element of a radioisotope that retains the properties of a quantity of the substance in one atom. Since isotope of the same element have essentially the same chemical properties, radioisotopes can be used to trace elemental materials at the atomic level. The requisite that the tracer have a distinguishable property that allows its identification is easily met by the radioisotope, it decays spontaneously with the attendant emission of radiation. When you realize that one radioactive decay event is detectable and that this represents an observation on the atomic level, you get a feeling for the high sensitivity of the radiotracer method. In addition to their almost unlimited application and their ease of dedection, radiotracers have four other advantages that should be stressed: 1. They can be made selective, 2. They enable unambiguous measurements to be made. 3. They permit the simple statistics of radioactive decay to be used to predict maximum measurement precision. When several radiotracers are available, they following factors should be considered before a choise is made: -cost -half-life -radiations emitted, both type and energy - radiation hazard - availability viu-cost -half-life -radiations emitted, both type and energy - radiation hazard - availability Radiotracer techniques have found wide usage in the study of chemical and mechanical manufacturing processes. These are techniques for the determination of mixing times, residence times, and frequency responses. Radiotracer techniques are usefull in these application because they can often be dedected outside of metal containers without recourse to sampling. Batch-mixing operations are important to many processes. Radiotracers offer an excellent means for determining the optimum mixing time in these processes. The purpose of mixing is to make the resultant mixture homogeneous, but the homogeneity is relative to the scale size that is considered. Whether or not a mixture is homogeneous at a given scale size is determined by examining samples of that size and determining if they have the same composition. Radiotracer techniques for determining optimum mixing times involve mixing a suitable radiotracer with one constituent of the materials to be mixed and then carrying out the mixing operation in the usual manner. The time required for homogeneous mixing occurs when the radiotracer concentration becomes homogeneous throughout the mixture at the scale being investigated and to the limiting variability of the tracer measurement. This can be determined either by continuous radiation dedection at some point in the mixer vessel or by counting discrete samples. In the continuous-dedection method, after mixing begins, the radiotracer phase undergoes gross movement. This gives rise to large variations in the counting rate. As the mixing proceeds, the counting rate fluctuations begin to get smaller and smaller until, finally, the fluctuation in the counting rate are due only to the statistical fluctuations of the dedector system. At this point the mix is as homogeneous as can be determined by the measurement technique. IXIn the continuous-dedection method, after mixing begins, the radiotracer phase undergoes gross movement. This gives rise to large variations in the counting rate. As the mixing proceeds, the counting rate fluctuations begin to get smaller and smaller until, finally, the fluctuation in the counting rate are due only to the statistical fluctuations of the dedector system. At this point the mix is as homogeneous as can be determined by the measurement technique. In the discrete-sampling method, random samples can be taken at fixed time intervals and counted with a dedector connected to a scaler. Complete mixing at the sample size employed is indicated when the fluctuations in the counting rate from one sample to the next are due only to the statistical fluctuations in the measurement of individual samples. A more elaborate and theoretically sound sampling method is to take multiple samples at discrete time intervals. The standard deviation from the mean of each set of samples can be determined from the normal estimator equation. When the standard deviation is constant with time, the mix is homogeneous. In this thesis, the purpose is to determine the mixing time of different liquid materials by using radiotracer technique. In other words, we studied on different liquids which have different densities and viscosities to determine the mixing time experimentally. Nine liquids are used in our experiments that are water, liquid soap, sunflower oil, corn oil, olive oil, motor oil, antifreeze, ink, and glycerin. The densities and viscosities of these liquids are measured experimentally in the laboratory. Each measurement is repeated several times for sentivity of the studying. Two different tracer techniques are used in our study which are radiotracer technique and paint tracer technique to compare them at the end of the experimental work.In the first technique, a gamma ray source as sodium-24 is used for experimental cases. Irradiation of sodium have been done in ITU TRIGA Mark-II Reactor at 250 KW full power rate. Irradiation time are calculated according to appropriation of the radiotracer technique, with using nuclear safety criteria. In the result of the studies, graps are drawn for each materials to determine the mixing time by using the experimental data. In addition, the effect of viscosity and density to the mixing time is researched and then the results of these graps are written in detail at the last part of the thesis. XI 109