Radiation protection

Radiation protection

          Nowadays, the progression of science and technology has played a role in daily life and the development of the country in every aspect. However, an aspect that should not be overlooked is the correct knowledge and understanding of technology. The misunderstanding results in an improper technology control leading to danger. It is in the same way as radioactive substances application because radioactive substances have many benefits, but the disadvantages are also presented depending on the amount, type, and duration of radiation exposure. For example, acute high doses of radiation can cause death. The radiation exposure to the reproductive organs causes infertility and can transmit to the offspring, which leads to deformity.

Therefore, staffs working in radiation should have knowledge, and understanding of radiation protection. Those will be able to utilize radiation in the most effective and safe way.

Sources of radiation

radioactive substance is substance that emit radiation. Radiation is a particle or wave emitted by a radioactive atom. Radioactive substances can be classified according to the sources.

1. Nature: natural radioactive substances are Uranium 235, Uranium 238, Carbon 14, which coincide with the birth of the earth.
2. Man-made: it is from a nuclear reaction in a nuclear reactor, or in a particle accelerator (Neutron generator or Cyclotron generator), etc. Radioactive substances obtained from human production, such as Cobalt 60, Iodine 131, Cesium 137, and Neutrons.

Both groups of radioactive substances will emit radiation, namely alpha radiation, beta radiation, and gamma neutron radiation. In addition, well-known and widely used radiation with many benefits, is X-rays, which are generated by X-ray generators. This is produced by a high voltage electric system to accelerate the electrons at high speed to hit a target made of heavy metal. This radiation has ability to penetrate through various objects. The amount of penetration depends on the density of that object.

Benefits of radiation

          The radiation can be used for medical, industrial, agricultural, and research purposes as follows:

• Alpha radiation is used as a component of lightning rods (Am-241 , Ra-226), dust suppression equipment (Po-210), and as a component of smoke detectors (Am-241).
• Beta radiation is used for pterygium treatment (Sr-90), hydrophobic substance (H-3), reflective/fluorescent substance (Pm-147), and the pain suppressor for bone metastatic cancer (Sm-153).
• Gamma radiation is used for cancer treatment (Co-60), disinfection (Co-60), diagnosis and treatment of thyroid disease. (Co-60, I-125 , I-131) , kidney functional test (I-131), liver/ biliary tract/ myocardial functional test (Tc-99m) , Pulmonary/cerebral blood flow study (Tc-99m).
• X-rays are used for organ images and foreign object detection.

One important radioactive substance is Cobalt-60. In February 2000, it was a case where we realized the dangers of radiation that we should not overlook. Cobalt-60 (Co-60) is a radioactive substance that does not exist in nature. It is made by Cobalt-59, which are metals in nature, impregnated with neutrons in nuclear reactors. It has a half-life of 5.26 years and decays to gamma and beta radiation. However, the most useful radiation is gamma radiation, which can be used in various ways as follows:

1. Agricultural

1. 1. Mutation Breeding, such as rice varieties 6, 10, 15, Doi Kham soybean, and Banana Hom Thong KU1
   2. Sterile Insect technique, such as exterminating fruit flies on Doi Ang Khang, Chiang Mai.
   3. Food Preservation by the Food and Agricultural Produce Irradiation Center of the Office of Atomic Energy for Peace provides the following services:

a. Inhibit germination: potato, onion, garlic, ginger

            b. Delay ripening: mango, apaya

            C. Slow bloom: mushroom

            D. Destroy parasites: pork, fermented pork

            E. Reduce bacteria and fungi: fresh fish, fresh meat, frozen shrimp, spices

            f. Insect control: rice, mung bean, dried fruit, dried fish, sweet tamarind

Products that have been irradiated do not have any residual radiation. This is due to the gamma radiation will not cause the medium to become radiation. Therefore, irradiated food is safe for consumers.

2. Industrial

In Thailand, there are approximately 165 industrial plants that use radioactive cobalt-60 as follows:

      2.1 Level measurement: weaving factories, plastic factories

      2.2 Thickness measurement: metal factories

      2.3 Density measurement: plastic factories, tile factories

      2.4 Exploration of boreholes to search for mineral resources

      2.5 Radiation for medical supplies: syringes, gloves, scalpels and medicines.

3. Medical

There are 39 cobalt-60 machines in medical institutions and hospitals in Thailand for cancer and in various tests as mentioned above.

Storage of radiation sources

        Practical, people usually do not receive too much radiation. Because in the operation of radiation, it is necessary to cover or block with concrete, metal, or lead to reduce the radiation rate and prevent radiation leakage. The commonly used radioactive Cobalt-60 is a sealed source. When it is used in medical aspect, the radiation source is placed in a shielding material, such as Uranium and Lead. During use, the radiation source is moved through the irradiation port by a pneumatic system to the target.

For industrial or radiography, radioactive substance is contained within the projector. The radiation source will be driven to the desired point via a remote-control device to irradiate. The unit of radiation is measured in Gray, Rad, Sievert, and Rem, with the amount of radiation 1 Gray = 1 Sievert = 100 Rad and 1 Rad = 1 Rem.

Danger or harm from radiation

        As mentioned above, radiation is a particle or wave emitted by an atom, therefore, it has no color, smell, or anything that can be noticed. The person who received it did not know that he had been exposed to radiation. Thus, those workers need to use external radiation detectors for measurement of the amount of acquired radiation. For the diagnosis and treatment with x-rays, patients and staffs can be obtained radiation as follows:

- from the x-ray beam directly.

- from radiation leakage.

- from scattered radiation that touches the patient.

In addition, the causes of radiation exposure for patients include:

- Non-essential radiological examinations

- Repeated radiography

- Using improper radiography techniques

- Officers misunderstanding or unaware of the principles of protection from radiation

Radiation hazards to humans can be divided into two groups:

1. External exposure

The severity of the injury depends on the strength and duration of exposure. However, the injured patients do not receive the radioactive material into the body. Therefore, there is no radiation to harm others.

2. Internal exposure

It is usually found in the case of the radiation, in form of gas, liquid, or dust, leakage from a storage site, from nuclear power plant explosions in Chernobyl, Russia, or from explosion of nuclear weapons in Hiroshima and Nagasaki, Japan. Radioactive substances are dispersed into the air and water, which humans may be exposed to radiation by inhaling, consuming contaminated matters, or radioactive implantation for treatment. Radioactive substances in the body emit radiation that harms to body for a long time until it is eliminated from the body. Moreover, it can also radiate to harm people nearby as well.

Exposure to radiation can affect the body in two ways:

1. Acute or Deterministic Effect: when exposed to large doses of radiation (more than 10 Rad at one time) causing a large number of cells to be injured, damaged, or dead. That leads to radiated organs unable to function. The important organs of the body that will change when exposed to radiation are:

• Bone marrow is the most sensitive organ and changes quickly because it is an organ that is being created all the time.

• The gastrointestinal tract is an organ that is less sensitive to radiation than the bone marrow.

• Skin can be found either without wound but burning and darken or getting a large amount with redness and blistering.

• Reproductive organs

• Brain and central nervous system: The neurons are relatively resistant to radiation. Most of these changes are caused by the destruction of the blood vessels that supply the brain rather than by the death of brain cells.

• Lungs

Symptoms of radiation exposure are divided into three stages:

Phase 1: Initial Syndrome occurs at the beginning of radiation exposure or hours after exposure. There will be fatigue, loss of appetite, vomiting, diarrhea, fever, and skin symptoms. These symptoms may last for several days.

Phase 2: Remission phase is when the symptoms of phase 1 disappear.

Phase 3: Established acute radiation syndrome will have symptoms and will be detected due to the destruction of that organ, such as

• Bone marrow: white blood cells gradually decrease, resulting in reduced immunity. Thus, it will easily cause infection. Moreover, decreased platelet count leads to easy to bleed and difficult to stop.
• Gastrointestinal tract: nausea, vomiting, and diarrhea
• Central Nervous System and Brain: loss of muscle control, dyspnea. If patients have these symptoms of this system, patients will die 100%.
• Pulmonary symptoms: pulmonary edema is usually the cause of death in the 3^rd - 4^th week. If patients expose to radiation whole body, it will cause the following symptoms:

1. Received radiation 3-5 Gray: the bone marrow does not produce hematopoietic cells. The death rate is up to 50% and patients may die within 30-60 days.
2. Received radiation 5-15 Gray: radiation affects the gastrointestinal tract, which causes nausea and vomiting, and patients may die within 10-20 days.
3. Received radiation more than 15 Grays: radiation affects the nervous system, which may cause death within 1–5 days.

2. Delayed or Stochastic Effect: when the body receives a small amount of radiation, if the cells die, the body will not have any abnormal symptoms. However, if the cells do not die, then the abnormality of that cell may occur. The effects that occur after exposure to radiation are cancer and genetic effects. The correlation between radiation exposure and the risk of cancer is related to the type of exposure and the amount of radiation. For the impact on the human genetics, it can be summarized as follows
   1. Mutation
   2. Any radiation dose plays a role in causing genetic risk in germ cells.
   3. The frequency of radiation-induced mutations is directly proportional to the radiation dose.
   4. The effects of radiation depend on the radiation exposure rate and duration of exposure.
   5. Most of the radiation-induced mutations will be inferior, therefore, there will be no expression in next generations. However, effects on reproductive organs and fetus can cause sterility, miscarriage, birth defects, and risk of cancer.

Table shows the effect of radiation on sterility.

Table shows the effects of radiation on fetus.

Effect on cancer, which must receive a large amount of radiation at one time or several times repeatedly for a long time, will be shown over many years.

Table shows the effects of radiation on the body by the International Commission on Radiological Protection (ICRP), an international organization for radiation protection. The effects of radiation on the body have been compiled as follows.

The table shows the radiation dose limits for the general public and radiation workers per year according to the criteria of the ICRP

Note: The millisievert is a measure of the amount of radiation received by the body. In a typical year, an individual receives about 2.23 mSv from natural radiation.

Radiation protection

For radiation workers, you should do the following:

1. Spend the shortest working time: the amount of radiation receiving depends on the time of exposure. You should avoid unnecessary radiation exposure.
2. Keep the distance as far as possible from the radiation source: Air can be a barrier against radiation. If the distance is 2 times from the radiation source, the radiation dose is reduced to ¼.
3. Provide appropriate radiation shield for each type of radiation according to their properties.
   • Alpha radiation can be blocked by a sheet of cardboard.
   • Beta radiation can be blocked by low mass materials such as thick plastic sheets.
   • Gamma or X-rays can be blocked by high mass materials such as lead or iron.
   • Neutron radiation can be blocked with concrete, wax, or paraffin.
4. Limit the space of radiation: it is very useful for prevention of unnecessary radiation exposure. That is to limit only the size of the beam region according to the size of the organ for examination, which can provide small amount of radiation and produce a clear image.
5. Have radiation shield at all times during radiography and not protrude any parts of your body out of the shield if it is not necessary.
6. Hold and fix the patient during radiography by relatives or others who are not involved in radiation work. They must wear a shirt and gloves for radiation protection every time.
7. Maintain radiation equipment regularly in a safe and usable condition at all times.
8. Attached a radiation measuring device while working to check the quantity of received radiation.
9. Be careful of radioactive contamination to the body either through inhalation, ingestion, or contact with skin or wounds.
10. Label name of radioactive substances clearly, in terms of type, date, strength of radioactive substances.

For general people

1. Should not be near the radioactive area or operation area. Generally, there has an attached warning sign (a three-pointed propeller).
2. Should avoid radioactive examinations or treatments in pregnant women. If it is necessary, you should consult with a doctor and strictly follow the instructions.
3. Avoid taking X-rays multiple times.
4. Should have a radiation shield for pediatric patients who need X-rays, especially in the genital area.
5. Prohibit pregnant women and children to visit patients who have been implanted radioactive substance.
6. Should obtain consent from a physician about returning home after radioactive implantation.

Personal radiation meter is a device for collecting data of amount of received radiation from outside the body for assessment the level of danger from radiation exposure. There are 3 types:

1. Pocket dosimeter: it is used for people who have to enter to a relatively high radiation area for a short period of time. When leaving the area, the received radiation dose can be read immediately.
2. Film Badge: It is a film in the cartridge. X-rays, gamma rays, beta and neutrons can be measured by this tool. In addition, it can also measure radiation over a wide range and distinguish type and doses of radiation. The outer part of the film wrapper has the name, date of use, and user identification number.
3. TLD (Thermolumine scene dosimeter): There are many types and different range of applications. It can measure much smaller radiation doses with greater certainty than film. In addition, it can be reused. However, it is more expensive than film and cannot store permanently as film.

Precautions for using Personal Radiation Monitors

   1. Do not borrow or exchange.

   2. Be careful not to get wet, get moisture, break, or damage.

   3. Be careful not to be close with heat or direct sunlight, such as in a car.

   4. Use the radiation meter correctly according to the purpose.

   5. Return it for evaluation of radiation exposure (films and TLDs are evaluated every 1-3 months).

Source: Rungthip Udomwisetsan

Diagnostic Radiology Unit

Songkhla Nakarin Hospita