Prozess Investigation

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1 Radiotracer in Prozess Investigation Fraunhofer Institute for Nondestructive Testing Dresden Dr. rer. nat. habil. Albert Zeuner Fraunhofer IZFP-D Maria-Reiche-Straße 2 D Dresden +49(0)351 / (Laboratory) Albert.Zeuner@izfp-d.fraunhofer.de de and (0351) / (0172) Albert.Zeuner@web.de 1 Veranstaltung Ort, Termin

2 Function and Purposes of IzfP-D The Fraunhofer Institute for Nondestructive Testing (IZFP) was founded in 1972 and is situated in Saarbrücken. The Dresden branch (IZFP-D) was founded in Purposes of the IZFP-D: Improvement of the product quality Lowering of the Quality costs Confirmation of the technical safety for devices, machines and plants as condition of their use 2

3 Content 1. Introduction ti 4. Evaluation of measured values 4.1. General 2. Labelling 4.2. Residence time investigations General Problems Mean residence time 2.2. Addition of labelled material Mixing behaviour 2.3. Radionuclides as labelling agent Vessel number Labelling possibilities Mixing investigations Amount of labelling agent Measuring technique Batch processing Continuous operation Other homogeneity terms 3.1. General 5. Investigated subjects 3.2. Sample measurement 5.1. Residence time Outside (probe) measurement 5.2. Mixing investigations 5.3. Other activities 6. Radiation protection aspects 7. Summary 3

4 1. Introduction some basics of radionuclides sealed sources solid material open radionuclides = radiotracer use of ionizing radiation itself where is the radioactive material? in what concentration the actual (radio-)tracer technique - RNT - potassium content in the potash industry applicati ions: estimation of radionuclides in human body ( Body counter ) soil analysis (gamma spectrometry) investigation of residence time and mixing processes chemical investigations (equilibria) nuclear medicine 4

5 2. Labelling residence time and mixing investigations The radioactve material has the function of labelled atoms and allows conclusions with regard to the origin of the radiation in nuclear medicine - scintigraphy in continuously working technical devices residence time analysis mixing investigations application: nuclear medicine technique principle: addition of a (radioactive) indicator measurement of the indicator concentration conclusion about the behaviour of the interesting material what indicator? how much? measuring technique justified? 5

6 2. Labelling some remarks to labelling of material (with radionuclides) pr roblem 1: problem 2: an nswer: to label something (by an indicator) means to change its properties but the properties of labelled material must not differ from those of the original material. well detectibility much labelling agent but large change of properties little labelling agent small change of properties but bad detectibility 99m Tc : 0.1 GBq example for calculation: 10 8 Bq 3 x atoms labelling paradox Let s assume a 100-fold spillover: extremely little material = practically use of 10-9 moles no change of the properties radionuclides! ca g extremely well detectibility tibilit less than each other in addition: decay of the radioactivity imputity 6

7 2. Labelling process analysis versus radionuclide technique quality amount connections between result (product) cs tech hnical eco onomic cha aracteristi yield conversion degree costs of material energy equipment investigation possibilities: singular investigation at constant parameters actual state repeated investigation with parameter variation correlations process parameters use of radionuclides allows to estimate: pressures temperatures amounts and concentrations flow rates balances this results in: residence time reaction time mixing homogeneity of materials and energies depending on time and place elapsed time velocity filling degree 7

8 3. Measuring technique scheme of radiotracer application radionuclides properties nuclear physical physical chemical availability costs process section in investigation technical physical conditions chemical radioactive contamination of the environment economic results yield conversion energy input costs choise of a radionuclide activity estimation injec ction de evice outside probes sa amples control process interpretation radioactive labelling of a sample of the material input signal measuring values (incl. correction) transitionfunction labelling measurement evaluation 8

9 3. Measuring technique outside (probe) measurement scintillation detector inserted into a cooling jacket and in an collimator (lead, tungsten) O

10 3. Measuring technique sample measurement sample beaker h 4 h 3 above the h 2 detector h 1 theoretical the pulse density depends on the sample mass (sample high) for this reason a calibration is necessary, real due to the self-absorption of measurement radiation inside the sample 10

11 4. Evaluation material transport rel. units different shapes of residence time distributions, depending di on n 0 t 0 t normalized mean residence time 11 input signal Dirac pulse answer signal residence time distribution

12 4. Evaluation material transport than: mean residence time 1. initial moment most important parameter mean residence time : first step: density function derived: elapsed time between 2 (detector) positions, 1 und 2 material velocity between 2 (detector) positions material amount between 2 (detector) positions filling degree 12

13 4. Evaluation material transport third step: plug flow or mixer? 2 = ( ) 2 the variance around the mean value 2. central moment Z t ) t E( t) w( t) characterizes the uniformity of the 0 material transport vessel ( E ( t ) ) vessel number ( dt n n = Z( t 2 ) 2 n n 1 - mixer behaviour - plug flow 13

14 4. Evaluation batch mixer mixing investigation labelled substance is added at one point of the mixer volume samples are taken at different moments (after stopping the mixer) mean value, standard deviation, and variance are calculated the variance is plottet against time the optimal mixing time is at the minimum of the variance continuously working mixers labelled substance is continuously added at the mixer inlet one or more detectors puls rate is plotted as function of time in case of homogeneous mixing, the pulse rate at each detector is constant t 14

15 4. Evaluation time optima al mixing x, σ, x σ x x decomposition mixing investigation practice theory batch operation: At different moments, the mixer is stopped, samples are taken; mean value, standard deviation, and variance are calculated variance against mixing i time (mixing of two sorts of sand) 15

16 4. Evaluation mixing investigation, other homogeneity terms 1. homogeneity degree H: H=1-ν...only usable when the measured values are near to a Gauss or Poisson distribution. In practice, the variance may be greater than 1, so a negative homogeneity degree would arise. 2. relative inhomogeneity I Between the mean µ and the standard d deviation i σ of the Poisson distribution exists the relationship In practical investigations, the condition that the particles do not influence each other is not fulfilled, this equation may be not valid. For these cases the connection between mean and standard deviation is assembled by the definition of the relative inhomogeneity I: I (relative inhomogeneity) If I >1 - the mixture is classified as allows to compare different substochastic (inefficient mixing) mixing investigations and shows the difference of the If I <1 - the mixture is hyperstochastic found homogeneity to the ideal value I = 1 16

17 5. Investigated subjects (extract) residence time Solid: material transport in a lot of drum dryers and rotary kilns in coal processing and in cement and potash industry. radiotracer: 140 La, eluated from a 140 Ba/ 140 La generator. transport of a single particle through a screw conveyor by the CARPT method. a small glass ball was activated. The built radionuclide was 24 Na. Liquid: In a pilot plant (two-phase system, 20 bar pressure) a benzene derivative was labelled with 82 Br. 7 detectors at different points along the plant. Gaseous: In a gas reactor the transport of the gaseous phase was investigated by addition of 41 Ar. This work was referred already in the 4. IGCC&XtL in The air exchange in cabs of trucks was investigated by using 85 Kr. 17

18 5. Investigated subjects (extract) mixing solid: Optimization of mixing time for batch mixers by using 99m Tc. The binder distribution ib ti in mineral wool plates was investigated t by different radionuclides ( 140 La, 99m Tc, 32 P) to study the influence of radiation from outside volume elements. In the same way the distribution of one reaction partner in polyurethane foam was investigated ( 99m Tc). 18

19 5. Investigated subjects (extract) other activities Isotope generators: Because radionuclides from isotope generators are very useful also for technical application, a lot of investigations were done by these generator nuclides ( 113m In, 99m Tc). As these radionuclides are not usable for investigation of processes at higher temperatures, a 140 La generator was developed. 140 La was used for a lot of investigations in rotating ti drums, especially at higher h temperatures. t By labelling with 99m Tc the grain growth in a fluid bed was investigated. In connection with the labelling lli of crushed brick, the solubility of La 2 O 3 was estimated. some special investigations with sealed sources very exact density estimation determination of steam content in streaming hot water. 19

20 6. Radiation protection aspects The IZFP (Institute for non-destructive testing) Dresden has a legal permission to apply radionuclides for investigations also outside the laboratory. The radioactively contaminated material is to collect and to store until its activity lies below the maximum permissible value, accordingly to the annex XVI of the German radiation protection ordinance. Being compliant with these limitations is not an issue, especially in pilot plants. The radiation exposure for the involved personnel of the industrial partner can be neglegted. The radiation exposure of the staff of the institute is controlled by dosimeters and in no case exceeded the limiting values. 20

21 7. Summary Radiotracers offer some advantages in investigation of laboratory and technical processes: - The amount of radiotracers is in the order of 10-6 moles/use. This is normally below the concentration of other impurities and does practically not influence the quality of the product, - By using short lived radionuclides, the time until the activity is below the permitted limit is short. So, a temporary storage causes no issues, especially in investigation in laboratory or pilot plant scale, - By using short lived gamma radiation emitting radionuclides, the necessity of taking samples is omitted and probes can be positioned outside the walls of the plant. - Results of the measurement are available shortly after the end of the experiment. can be used in investigation of material transport and mixing processes. - vessel number n can be calculated only from the measured values - Mixing investigations have been explained, as well as another interpretation of homogeneity. 21

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