Radioactive Exposure. Abstract of Article:

Transcription

1 Radioactive Exposure Abstract of Article: All ionizing radiations, at sufficiently large exposures, can cause cancer. Many, in carefully controlled exposures, are also used for cancer therapy. Ionizing radiation and radioactivity are found naturally within the environment and their levels depend generally on the distribution of natural radionuclides within the environment. Industrial and medical uses of radiation are beneficial to man. The benefits derived in these cases notwithstanding, use of radiation and radionuclides can be hazardous to man and the environment if such use isn t regulated and exposure to radiation kept within acceptable limits. As radioactive material decays, or breaks down, the energy released into the environment has two ways of harming a body. It can directly kill cells, or it can cause mutations to DNA. If those mutations are not repaired, the cell may turn cancerous. When the radiation damages nearby healthy tissue, it can cause side effects. Many people worry about this part of their cancer treatment. Before treatment, talk with your doctor or nurse about what you might expect.

2 1. Steel- Cradle to grave cycle: Article Writing Competition: Radioactive Exposure

3 2. Radioactive radiation, hazards and risks. There are three major types of natural radioactivity: Alpha Radiation Alpha radiation consists of a stream of positively charged particles, called alpha particles, which have an atomic mass of 4 and a charge of +2 (a helium nucleus). When an alpha particle is ejected from a nucleus, the mass number of the nucleus decreases by four units and the atomic number decreases by two units. For example: U 4 2He Th The helium nucleus is the alpha particle Beta Radiation Gamma Radiation Beta radiation is a stream of electrons, called beta particles. When a beta particle is ejected, a neutron in the nucleus is converted to a proton, so the mass number of the nucleus is unchanged, but the atomic number increases by one unit. For example: e Pa The electron is the beta particle. Gamma rays are high-energy photons with a very short wavelength ( to 0.1 nm). The emission of gamma radiation results from an energy change within the atomic nucleus. Gamma emission changes neither the atomic number nor the atomic mass. Alpha and beta emission are often accompanied by gamma emission, as an excited nucleus drops to a lower and more stable energy state. 2.2 Hazards Spontaneous decay of radioactive materials produces radiation. Radiation may be ionizing and nonionizing. Alpha and beta, gamma and X-rays particles are the most common forms of ionizing radiations. Radioactive iodine is a beta particle released during nuclear plant accidents. The amount of energy the radiations can deposit in a given space varies with each type. Radiations also differ in the power to penetrate. Inside the body the alpha particle will deposit all its energy in a very small volume of tissue while gamma radiation will spread energy over a much larger volume.

4 2.3 Risks The most important are: The higher the radiation dose, the greater the chance of developing cancer. The chance of developing cancer, not the seriousness of the cancer, increases as the radiation dose increases. Cancers caused by radiation do not appear until years after the radiation exposure. Some people are more likely to develop cancer from radiation exposure than others. 3. Brief History of serious radiation of exposure in the world. In December 1983-February 1984, in Ciudad Juarez, Mexico, and the United States, occurred one of the first widely reported cases of radiation exposure from the inadvertent destruction of orphaned sources through the scrap metal recycling process. On September 13, 1987, at Goiania, Brazil, a radioactive source was removed from an abandoned hospital in the city. Over time, the radioactive source was handled by multiple people, and led to the exposure to high levels of radiation of at least 245 people. Twenty of those showed sign of radiation exposure and needed hospital treatment. At least four people died. At a hospital clinic located in Zaragoza, Spain, between the dates of December 10 and December 20, 1990, at least 27 patients who were receiving radiotherapy for cancer were accidentally exposed to high levels of radiation, which resulted in the deaths of 11 patients, and severe injuries to the others. 4. Contamination of metal scrap used for steelmaking by radioactive sources. The United Nations Economic Commission for Europe (UNECE) describes the three ways radioactively contaminated scrap is produced: Discrete radioactive sources may be mixed with scrap when they escape from regulatory control by being abandoned, lost, or stolen. Uncontrolled material contaminated with natural or man-made radionuclides from industrial processes may enter the scrap stream. 1. Example 1:. Pipe scale from oil and gas drilling that contains naturally occurring radioactive material (NORM). As the oil or gas is pumped from the ground, radionuclides and other minerals from the surrounding soil and water are deposited in pipes or equipment. This material may not be under regulatory control in the first place. 2. Example 2: Material improperly released from the nuclear industry that was contaminated with man-made radionuclides above regulated limits. Material with a very low levels of radioactivity that are below regulatory limits

5 5. Effects of Radiation exposure to human health. High doses of ionizing radiation can lead to various effects, such as skin burns, hair loss, birth defects, illness, cancer, and death. The basic principle of toxicology, the dose determines poison, applies to the toxicology of ionizing radiation as well as to all other branches of toxicology. In the case of threshold effects ( deterministic effects in the language of radiation toxicology), such as skin burns, hair loss, sterility, nausea, and cataracts, a certain minimum dose (the threshold dose), usually on the order of hundreds or thousands of rad, must be exceeded in order for the effect to be expressed. An increase in the size of the dose above the threshold dose will increase the severity of the effect. The thyroid gland is one of the most radiation-sensitive parts of the body, especially in babies and children. Most nuclear accidents release radioactive iodine into the atmosphere. This is absorbed by the body. Absorption of too much radioactive iodine can cause thyroid cancer to develop several years after exposure. 6. Measuring Radiation and safe limits of exposure 6.1 Radiation Measurements Radioactivity Absorbed Dose Dose Equivalent Exposure Common Units curie (Ci) rad rem roentgen (R) SI Units becquerel (Bq) gray (Gy) Sievert (Sv) coulomb/kilogra m (C/kg)

6 6.2 Safe limits of exposure There is no firm basis for setting a "safe" level of exposure above background for stochastic effects. Many sources emit radiation that is well below natural background levels. This makes it extremely difficult to isolate its stochastic effects. In setting limits, EPA makes the conservative (cautious) assumption that any increase in radiation exposure is accompanied by an increased risk of stochastic effects. However, there do appear to be threshold exposures for the various non-stochastic effects. (Please note that the acute affects in the following table are cumulative. For example, a dose that produces damage to bone marrow will have produced changes in blood chemistry and be accompanied by nausea.) Exposure Time to Onset Health Effect (rem) (without treatment) 10-May changes in blood chemistry 50 nausea hours 55 fatigue 70 vomiting 75 hair loss 2-3 weeks 90 diarrhea 100 hemorrhage 400 possible death within 2 months 1,000 destruction of intestinal lining internal bleeding and death 1-2 weeks 2,000 damage to central nervous system loss of consciousness; minutes and death hours to days 7. Preventive Control Method of radiation exposure. Three main factors contribute to how much radiation a person absorbs from a source. The following factors can be controlled to minimize exposure to radiation. Increasing distance from the source of radiation The intensity of radiation falls sharply with greater distance, as per the inverse square law. Increasing the distance of an individual from the source of radiation can therefore reduce the dose of radiation they are exposed to. For example, such distance increases can be achieved simply by using forceps to make contact with a radioactive source, rather than the fingers.

7 Decreasing duration of exposure The time spent exposed to radiation should be limited as much as possible. The longer an individual is subjected to radiation, the larger the dose from the source will be. One example of how the time exposed to radiation and therefore radiation dose may be reduced is through improving training so that any operators who need to handle a radioactive source only do so for the minimum possible time. Reducing incorporation into the human body Potassium iodide (KI) can be given orally immediately after exposure to radiation. This helps protect the thyroid from the effects of ingesting radioactive iodine if an accident occurs at a nuclear power plant, for example. Taking KI in such an event can reduce the risk of thyroid cancer developing. Shielding Shielding refers to the use of absorbent material to cover a reactor or other source of radiation, so that less radiation is emitted in the environment where humans may be exposed to it. 8. Monitoring techniques of radiation exposure. The Radiation Exposure Monitoring Profile requires imaging modalities to export radiation exposure details in a standard format. Radiation reporting systems can either query for these "dose objects" periodically from an archive, or receive them directly from the modalities. The radiation reporting system is expected to perform relevant dose QA analysis and produce related reports. The nature of such analysis and format of the reports is not considered a topic for standardization and is not covered in the profile. The profile also describes how radiation reporting systems can submit dose reports to centralized registries such as might be run by professional societies or national accreditation groups. By profiling automated methods, the profile allows dose information to be collected and evaluated without imposing a significant administrative burden on staff otherwise occupied with caring for patients.

8 9. Relevance of radioactive exposure of UNICOIL. The gauge radiation at UNICOIL which is being monitored every six month. We have 2 thickness gauges at CRM, 2 at CGL entry & 1 coating gauge at process. All are using the X-ray as the source which has radiation. As per UNICOIL safety norms, no one is allowed near the vicinity of the gauge by 2 meters when gauge is ON. Secondly, when maintenance personnel are working on gauge, the shutter is switched off which will block the radiation. IRM THICKNESS GAUGE RADIATION CHECKLIST Measured Radiation Level In MicroSiever/Hr CRM Distance (Meters) Limit MicroSiever/Hr milirem milirem Entry Thickness Gauge Exit Thickness Gauge CGL Entry Thickness Gauge Exit Thickness Gauge NOTE: 1 Micro sievert /hr=0.1mili rem Recommended preventive and monitioring techniques for UNICOIL. Methods for minimizing time in a field of radiation : Pre-plan and discuss the task thoroughly prior to entering the area. Use only the number of workers actually required to do the job. Have all necessary tools before entering the area. Use mock ups and practice runs and Take the most direct route to the site. Never loiter in an area controlled for radiological purposes. Work efficiently but swiftly and do the job right the first time. Perform as much work outside the area as possible. Methods for maintaining distance from sources of radiation: The worker should stay as far away as possible from the source of radiation. Be familiar with radiological conditions in the area. During work delays, move to lower dose rate areas. Use remote handling devices when possible.

9 Proper uses of shielding: Shielding reduces the amount of radiation dose to the worker. Different materials shield a worker from the different types of radiation. Use permanent shielding such as non-radiological equipment/structures. Use shielded containment (e.g., glove boxes, etc.) when available. Wear safety glasses/goggles to protect the eyes from beta radiation, when applicable. It should be remembered that the placement of shielding my actually increase the total dose (e.g., man-hours involved in placement, Bremsstrahlung, etc.). Temporary shielding (e.g. lead or concrete blocks) can only be installed when procedures are used. Once temporary shielding is installed, it cannot be removed without proper authorization. 11. International regulations/legislations in radiation exposure-related to steel industry. The Radiation (Emergency Preparedness and Public Information) Regulations 2001 (REPPIR) Ionising Radiations Regulations 1999 (IRR99) Radioactive Substances Act International Commission on Radiological Protection Radiation Protection Convention, 1960 (No. 115) Occupational Cancer Convention, 1974 (No. 139) Working Environment (Air Pollution, Noise and Vibration) Convention, 1977 (No. 148) 12. Recommendation for effective implementation of regulations/legislations. Effective implementation of Regulation/Legislation involves three key elements broadly categorized as organization, interpretation, and application. Effective organization entails that Regulations/Legislations are implemented by the appropriate agencies or that agency are created for this purpose. Interpretation means that legislative intent is translated into operating rules and guidelines. Application means that the new rules are in coordination with ongoing operations. 13. Conclusion: This Article has provided an overview of the health effects related to ionizing radiation exposure in humans and laboratory animals. These effects can be both non-carcinogenic and carcinogenic in nature. Non-carcinogenic effects primarily result in immediate effects, mainly to organs with rapidly dividing cells, which include the hematopoietic system, gastrointestinal tract, and skin, or delayed effects such as cataracts and embryo/fetal development problems. Carcinogenic effects also may

10 occur in any number of organ systems. This end point may not be expressed for several years after the initial exposure. The dose-response relationships for these effects are known from the massive amount of data from studies on both humans and animals. Epidemiology studies are not likely to provide significant refinement of radiation risk estimates. The most fruitful approach to further understanding risk from exposure to ionizing radiation is through molecular studies, including the identification of unique biomarkers and pathogenic pathways at the cellular and tissue levels.