الفهرس 
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Abstract
Radiochromic dyed thin film dosimeters have wide-spread applications in radiation processing for installation, process qualification and routine dose control for both gamma rays and electron beam irradiation. These film dosimeters have been introduced for low- and high-dose monitoring. The introduction of new types of films is due to the effort of seeking for more reliable, more stable, simpler and cheaper systems as routine dosimeters and/or label dosimeters. Many radiochromic films such as GAFCHROMIC films and label dosimeters based on diacetylenes and polydiacetylenes compounds introduced earlier especially for low dose application such as food irradiation and radiation therapy applications. Because these compounds are highly radiation sensitive and polymerize when subjected to γ-ray producing a highly coloured polyconjugated polymer, were used successfully in gamma and electron beam radiation monitoring labels and dosimeters.
Radiation indicators may be labels, paper, inks, or packing materials which undergo a visual colour change or become coloured when exposed to ionizing radiation [Abdel-Rehim, 1985]. They may be used to show that products have been exposed to radiation source and may be used for qualitative indication of radiation exposure [ISO/ASTM 51539, 2004]. While label dosimeters may be used for quantitative dose measurements during radiation processing.
The main objective of this work is to study the possibility of preparing polymeric dyed films, radiation indicators and label dosimeters for routine process control in industrial radiation processing, especially at Egypt Mega Gamma-1 industrial irradiator at National Center for Radiation Research and Technology (NCRRT), Cairo. The results obtained in this work can be summarized in the following:
Section (1):
Deals with the investigation of some polymeric films to make them readily usable in high-radiation dosimetry applications (e.g. sterilization of medical products, sterilization of pharmaceutical products and polymer modification). This section is divided into two parts:
part I: This part includes the preparation and development of polymeric dyed films for high-dose dosimetry applications, these films are based on poly (vinyl alcohol) dyed with p-nitrophenol (4-Np). These flexible plastic film dosimeters are bleached when exposed to gamma-ray photons (i.e. from yellow to colorless). The radiation chemical yield (G-Value) for different concentrations of the dye as well as the dye with three different additive substances (alanine, chloral hydrate and trichloro acetamide). It was found that these films are highly stable for long time before and after irradiation under different storage conditions. The response of these films is not affected by humidity change in the range of relative humidity (0-56%) and also they are not affected by the change of temperature in the range 20-40 oC. pVA films dyed with 4-Np are suitable in the dose range from 1-200 kGy. These properties suggest them to be useful for routine and dose mapping in sterilization range of radiation processing and for high-dose radiation dosimetry. They are easy to prepare in a laboratory and don’t require toxic solvents in its preparation.
part II: This part includes the preparation and development of polymeric dyed films for high-dose dosimetry applications, these films are based on poly (vinyl alcohol) dyed with Luxol fast blue (LFB). These flexible plastic film dosimeters are bleached when exposed to gamma-ray photons (i.e. from blue to colorless). The radiation chemical yield (G-Value) for different concentrations of the dye as well as the dye with additive substance as chloral hydrate. It was found that these films are highly stable for long time before and after irradiation under different storage conditions. The response of these films is not affected by humidity change in the range of relative humidity (0-60%) and also they are not affected by the change of temperature in the range 0-50 oC. pVA films dyed with LFB are suitable in the dose range from 5-120 kGy. These properties suggest them to be useful for routine and dose mapping in sterilization range of radiation processing and for high-dose radiation dosimetry. They are easy to prepare in a laboratory and don’t require toxic solvents in its preparation.
Section (2):
It deals with the investigation of some polymeric films to make them readily usable in food irradiation processing and water treatment. This section included one part:
part I: this part includes film dosimeter made of poly (vinyl alcohol) incorporating Rosolic acid indicator (RA) as an acid-releasing agent upon irradiation. These plastic films undergo color change from red to yellow as a result of radiation-induced HCl formation which in turn changes the form of the indicator from its basic to acidic form. The radiation chemical yield, G-value of the formed acid was discussed. The useful dose range of these films extends from 1-55 kGy depending upon chloral hydrate concentration. These films have negligible humidity effect in the range of relative humidity (RH) from (0-50%) and also have negligible temperature effect during irradiation from (10-50 oC). These films are highly stable before and after irradiation under different storage conditions.
Section (3):
It deals with the investigation of some polymeric dyed mixed films, to make them readily usable in both high-radiation dosimetry applications and low-dose applications (e.g. sterilization of medical products, sterilization of pharmaceutical products, polymer modification and food irradiation processing). This section is divided into two parts:
part I: This part includes the preparation and development of polymeric dyed mixed films for high-dose dosimetry applications, these films are based on poly (vinyl alcohol) dyed with a mixture of two dyes namely 2,6 dichlorophenol indopheniol sodium salt DCp (blue dye) and p-nitrophenol or 4-Np (yellow dye) with different concentrations of chloral hydrate. The color of this film changes from the green color to the yellow and finally to colorless. In these films first bleaching reaction for DCp takes place in the dose up to 50 kGy then the second bleaching reaction occurs in the dose up to 150 kGy. The response of these films is affected by the change in chloral hydrate concentration and also the ratio of the two combined dyes. These films could be used in two dose ranges, the first after complete bleaching of DCp up to 50 kGy and the second up to 150 kGy after complete bleaching to the yellow color of 4-Np. The response of these films is not affected by humidity change in the range of relative humidity (0-60% RH) and also they are not affected by the change of temperature in the range 0-40 oC. pVA films dyed with (DCp/4-Np)/pVA are suitable in the dose range from 1-150 kGy. These properties suggest them to be useful for routine and dose mapping in sterilization range of radiation processing and for high-dose radiation dosimetry. They are easy to prepare in a laboratory and don’t require toxic solvents in its preparation.
part II: This part includes the preparation and development of polymeric dyed mixed films for using in high-dose dosimetry applications as label and dosimeter for medical, pharmaceutical products and food irradiation processing. These films are based on poly (vinyl alcohol) dyed with a mixture of two indicator dyes namely TBpB tetrabromophenol blue and MCp metacresol purple with different concentrations of chloral hydrate, the color of this film changes from the green color to the yellow and finally to red color. In these films first transformation from the blue color (basic form of TBpB) to yellow color (acidic form) at about 30 kGy depend upon the chloral hydrate as a result radiation-induced HCl formation which in turn the indicator color change to its acidic form then the second up to 37 kGy after complete transformation . The response of these films is affected by the change in chloral hydrate concentration and also the ratio of the two combined dyes. The amount of acid formed due to irradiation process depends on the absorbed dose and chloral hydrate concentration. The response of these films is not affected by humidity change in the range of relative humidity (0-50% RH) and also they are not affected by the change of temperature in the range 0-40 oC. pVA films dyed with (TBpB/MCp)/pVA are suitable in the dose range from 1-37 kGy. These properties suggest them to be useful for food irradiation processing and for high-dose radiation dosimetry as label and dosimeter. They are easy to prepare in a laboratory and don’t require toxic solvents in its preparation.
Section (4):
It deals with the investigation and possibility of binding of Hydrazine sulphate powder in rods shape for use as radiation dosimetry system for gamma radiation processing, process qualification and routine dose control for both gamma rays and electron beam irradiation. These rod dosimeters have been introduced for low- and high-dose monitoring. Many rod dosimeters introduce earlier especially for low dose application such as food irradiation, radiation therapy applications and sterilization of medical products
part I: This section deals with EpR spectrometer to determinate optimum EpR parameters for measurement of radiation-induced paramagnetic centers in quartz rods. The results show that, optimum parameters are, microwave power = 2.012 mW, modulation amplitude = 3.00 Gauss, modulation frequency = 100 kHz, sweep width = 200 G, microwave frequency = 9.775 GHz, time constant = 163.48 ms, receiver gain = 8930 and sweep time = 20.97 s. The preparation and development of HZS rods for low and high-dose dosimetry applications, the results obtained in this work can be summarized as follow:
1 – A new EpR rod dosimeter (HZS) has been prepared by a simple technique in the laboratory using ethylene vinyl acetate copolymer and paraffin wax as binding materials.
2 – The binding mixture of EVA/paraffin does not present interference or noise in the EpR signal before and after irradiation.
3 – The prepared rods have good mechanical properties adequate for easy and safe handing.
4 – These rods can be used with good precision in the dose range from 0.05 to 100 kGy.
5 – These rod dosimeters have insignificant dependence on the change of relative humidity during irradiation.
6 – The overall uncertainty for calibration of the HZS rod dosimeters at 2σ was found to be 2.64 %.
7 – These dosimeters can be applied in many fields, inhibition of sprouting in fruits, fresh food irradiation, food irradiation, medical sterilization and water treatment.