PROCESSES
1. Process Control; In the Gamma Irradiation Facility, the irradiation process is realized by means of a powerful and reliable computer system (Programmable Logic Control), which is acknowledged in all over the world. Each stage of irradiation process is controlled in a very sensitive manner and if an abnormal case is occurred, Irradiator turns off automatically and gives audio and visual alarms. Furthermore each stage is recorded automatically.

2. Product Transportation System (Conveyor and Source transition system); The products to be processed are placed inside the aluminum tote boxes on the conveyor in their own packages and are sent to the irradiation room by means of the conveyor. The boxes full of products are moved around the source by means pneumatic pistons and exposed to gamma irradiation. After the irradiation process the tote boxes full of products are taken out automatically by conveyor and stored at the irradiated product area. The dimensions of the tote boxes made of aluminum are 58 x 64 x 124 cm and each of them can carry loads up to 125 kg.

3. Source and Source Rack: Source rack consists of a stainless steel frame with dimensions of 250x300 cm and 20 rectangular intermediate modules. 40-source pencils that are 45 cm long and with a diameter of 0.81 cm can be placed on each module. Metallic formed Co-60 slugs used as gamma source are placed in these source pencils. Source pencils are double encapsulated in stainless steel tubes and both ends are welled in a leakage proof manner. The manufacturer company of the source pencils shall protect their leakage proof characteristics for 20 years. Unstable Co-60 isotope is obtained from the stable Co-59 atom by adding a neutron into its nucleus via neutron bombardment in the nuclear reactors. Co-60 isotope emits one beta and two gamma rays with energy levels of 1.17 MeV and 1.33 MeV and transformed to stable Ni-60 atom. Since beta particles cannot pass through the stainless steel, irradiation process is realized only by the gamma rays. The irradiated products never become radioactive whatever the irradiation period is. The energy level of the gamma rays emitted by Co-60 isotopes is not enough to make any material radioactive. Therefore in theory no treaded product by gamma irradiation process shall be radioactive.

3.a. Gamma radiation; Gamma rays are electromagnetic energy same as the radio waves, TV waves, microwave, visible light or x-rays. On the other hand the wavelength and energy of all these ray types are different than each other. Microwaves have so much energy to cause the molecules move and result heat energy. Gamma rays have more energy when compared to the other ray types they can diffuse inside the materials easily. They might pick electrons from the atoms or molecules while they are passing through the materials. As a result of these electric charged particles (i.e. ions) are formed. The energy stored within the material is called "absorbed energy". 1 kGray ray dose equals to 1 kilo Jul/kg energy. If this energy is represented as heat energy, 10 kGy-absorbed doses can increase 2.5°C the temperature of 1 kg water.

3.b. Ionizing Radiation and its Impact Mechanism; Gamma rays are ionizing rays. When ionizing rays have an impact on the material they can pick electrons from the atoms. This process is called ionization. Free electrons can take part in the chemical reactions or destroy DNA molecules from the living organisms. This process is the base for killing the microorganism by irradiation,

4. Irradiation Cell (Biological Shield): This is the shielded room in which the irradiation process is realized. When the Irradiation Facility is operating, the Co-60 source rack is taken out of the water pool and placed among the boxes full of products. In order to avoid any radiation leakage out of the irradiation cell the walls and ceiling and floor of the irradiation cell are made of 180 cm thick concrete. 180 cm thick concrete barriers eliminate the gamma radiation formed by 4.0 MCi Co-60 sources and decrease the dose to an acceptable level for the employees and the environment. These protective concrete barriers are called biological shield. The thickness of the biological shield depends on the activity of the employed cobalt source and it was designed to meet the requirements of the International Radiation Protection Regulations. The personnel and product entry doors of the irradiation cell can be accessed after a maze for protection purposes.

5. Source Storage Pool: In order to turn the irradiation process off in the Irradiator, Co-60 source panel is dived into a 6-meter deep pool full of water. Co-60 source continues emitting gamma radiation within the water. On the other hand the water mass within 3.2 meters thick from the upper part of the source rack avoids the gamma lights to reach in the irradiation cell. In this way the personnel can enter to the irradiation cell without being exposed to the gamma rays and carry out the maintenance and repair works safely.

6. Product Storage Area: The product storage area in the gamma irradiation facility consists of two parts: unprocessed products storage area and processed products storage area. The products received are taken to the unprocessed products storage area and after they are prepared for irradiation process loaded to the conveyor. After the irradiation process the treated products are taken to the processed products storage area for loading to the vehicles.