Irradiation process-controlled

FOOD IRRADIATION PROCESS CONTROL AND DETECTION OF IRRADIATED FOODS... 

The system is widely used for calibration purposes, but its routine application for irradiation process control is also well known. It is mainly used in gamma and X-ray fields, but the solution can also be used for electron dosimetry. 

The sterilization processes described in the Ph Eur are preferred, especially terminal sterilization in the final container alternative processes have to be justified. All sterilization processes will need to be described and appropriate in-process controls and limits included. Where Ph Eur prescriptions are followed, there should be a statement to this effect in the application. Most of this information should be discussed in the development pharmaceutics section. Reference is made to the specific guidelines on ethylene oxide sterilization and irradiation sterilization, which are discussed further below. The possibility of parametric release for terminal processes such as saturated steam and irradiation is mentioned (see below). For all sterile products there should be a sterility requirement included in the finished product specification regardless of the outcome of validation studies. 

Modification of zeolites, based on chemisorption of silane or diborane and subsequent hydrolysis of the chemisorbed hydride groups can also be applied for encapsulating gas molecules in zeolites. For example, krypton and xenon can be encapsulated in mordenite combining the modification process with a physical adsorption of the noble gases at moderate pressures and temperatures (e.g. 100 kPa, 300 K). The encapsulates are homogeneous and stable towards acids, mechanical grinding and y-irradiation. By controlling the pore size reduction however, the thermal stability can be controlled. 

If you eat processed food, you have probably eaten ingredients exposed to radioactive rays. In the United States, up to 10 percent of herbs and spices are irradiated to control mold, zapped w ith X rays at a dose equal to 60 million chest X rays. Although food irradiation has been used in one way or another for more than 40 years, it faces an uncertain future in this country. 

An advantage of fission-product Mo is the high specific activity of Mo (> 10 Ci/g Mo). Disadvantages are the (1) elaborate and expensive post-irradiation processing facilities, (2) chemical separation of the highly-toxic a-emitters (transuranic radionuclides) and pure yff-emitters, (3) special problems of quality control, and (4) large quantities of long-lived radioactive waste. 

In this process, oxide fuel is dissolved in a molten chloride salt mixture through which Q2-HCI gas is flowing. Dissolved uranium and plutonium are then recovered as oxides by cathodic electrodeposition at 500 to 700°C. The process was demonstrated with kilogram quantities of irradiated fuel, with production of dense, crystalline UO2 or UO2-PUO2 reactor-grade material. Difficulties were experienced with process control, off-gas handling, electrolyte regeneration, and control of the plutonium/uranium ratio. Development has been discontinued. 

Fig. 4.5. Block-diagram of a combined irradiation and measurement device. DMR 10 (C. Zeiss, Oberkochen) process controlled by microprocessor TM 990 (Texas Instruments, Freising). PSl, PS2, alternatively active shutters F, interference filter B, beam splitter to P (photo diode) and sample cell (S), which is stirred R, reference cell ST 75, high-pressure...

The combination of an irradiation and measurement device needs some modification of the sample compartment of the spectrometer. In some cases problems with the geometry can arise. For this reason another approach was tried using the advantage of fibre optics. A bundle of quartz fibres (approx. 1 cm in diameter) allows process-controlled irradiation of the cell in a conventional double beam spectrometer (see Fig. 4.9) without any modification of the sample compartment. Only the cell holder has to be modified to allow the output of the fibre to be fixed [53]. 

Quite a few different set-ups have been demonstrated, in which an irradiation apparatus was combined with different methods of spectroscopy. In all these combinations, process control either by microprocessors or by personal computers, was achieved. Modem instmments contain a microprocessor for process control of the spectrometer and data transfer to a dedicated personal computer. Quite a few years ago data stations were integrated in the spectrometers. However, their flexibility is poor and their software is restricted to the instmmentation making adaptations to user specified problems very difficult. 

C-doped Ti02 was also prepared through the following processes controlled oxidative annealing of titanium carbide (TiC) for decomposition of trichloroacetic acid under visible light irradiation... 

CL-AGE copolymer films of ca. 3-mil-thickness were additionally vacuum-dried for 48 hours. Two sample temperatures, 25°C(semi-crystalline state) and 80°C(melt state), were utilized for irradiation. For the higher temperature of 80°C, a heated steel plate was used as the substrate for the copolymer. The film sample was placed on this temperature-controlled steel plate and passed through the electrocurtain system described below. For the irradiation process which required two passes, following the first pass the sample was again immediately placed on another 80 C steel plate and passed through the electrocurtain system a second time. 

Also an onboard electrical power supply, e.g., by photovoltaic cells or thermogenerators coimected to a lab-frame irradiation source, would introduce additional, frequency-independent degrees of freedom, enabling a multi-force manipulation of the processed liquids. Another extension of present centrifugal systems is the (wireless) data communication with the lab-frame workstation for an improved process control and analysis. 

The main application fields of dosimetry in radiation processing include installation, operational and performance qualification, and routine process control. The selection of suitable routine dosimetry systems depends on the actual measurement to be carried out. Various characteristics should be considered, such as accurate and reproducible response, dose and dose rate range, energy of radiation, environmental effects on the response, stability before, during, and after irradiation, and method of evaluation. 

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