Characteristics of ionizing radiation

ELECTROMAGNETIC CONTAMINATION

Intensity of electromagnetic radiation is measured in W/m² and determined by frequency.

Low frequency (0-300 kHz; 1-1000 km) radiated by all electro-devices, cables, cords, power lines.

Center frequency (0.3-3 MHz; 100 m-1 km) – wireless connection (radio).

High frequency (3-30 MHz; 10 m-100 m) – radio.

Very high frequency (30-300 MHz; 1 m-10 m) – TV, radio.

Ultrahigh frequency (0.3-3 GHz; 10 cm-100 cm) – radio.

Superhigh (microwave) frequency (3-30 GHz; 1 cm-10 cm) – radiolocation, satellite communication.

Extremely high frequency (30-300 GHz; 1 mm-10 mm) – radars.

Optical diapason:

- infrared radiation (0.1 mm – 0.76 microns): body with T>0;

- visible radiation (0.76 microns – 0.4 microns);

- ultraviolet radiation (0.4 microns – 0.2 microns): sun, daylight lamps;

- ionizing: radiation.

Biological effect is determined by force, intensity, size of exposed surface, frequency as the higher frequency radiation penetrates deeper.

EMF polarizes body cells (water cells) forcing them to move in EMF frequency. Exposure to EMF also causes ion-currents. Due to mentioned effects EMF causes heating of the body. The heat absorbed by the body from EMF may be backed away to some limit (10 mW/m2), or else it rises the temperature of the body. It has the most adverse effect on organs that much water and poor blood circulation, such as eyes, brain, kidneys, stomach, bladder. Blood circulation system may be imagined as cooling one. Exposure of eyes causes clouding of the crystalline lens, cataract, what appears after several days.

Ultraviolet radiation has the slight ionizing effect yet. They are divided into three subgroups: UVA near the natural, UVB carcinogenic, UVC ionizing (shortest waves, highest frequency). Among effects mentioned above malignant skin and eyes effect. Safe distance to daylight lamp: 3 m, to welding work: 5 m.

Ionizing radiation or briefly “radiation” is the emission or transfer of radiant energy as:

- particles: alpha, beta, neutrons;

- electromagnetic waves: gamma rays, X-rays.

Alpha radiation: a helium nucleus emission (containing two neutrons and two protons) with start speed 20,000 km per sec. It has greatest energy that’s why causes major damage as cells and atom decay. However its penetrating capability is the lowest among the other emissions. Paper sheet or clothing stop alpha radiation completely. It travels only for 1 cm in the air.

Beta radiation: a high-speed electron or positron emission. It’s less destroying power but greater penetrating capability as compared with alpha particle. Metal shield or glass absorbs it completely, clothing – about 50%. It travels for 11 cm in the air.

Gamma radiation: electromagnetic waves emitted as photons - portions of electromagnetic radiation. Its destroying power is 100 times less than beta and 10000 times less than alpha radiation. However its penetrating capability is the greatest what makes it major hazard of radiation exposure. Only anti-rad shelters are effective to reduce gamma exposure.

Neutron radiation: neutrons stream with the start speed 20,000 km per sec. Neutrons have zero charge and meet no resistance penetrating into cells and atoms. Neutrons transfer much energy, which excites and decomposes cells and atoms. The only protection from neutron exposure is anti-rad shelters.

Ionizing produced by radiation is the primary cause of its biological effect.

To ionize means to change or become changed into ions.

Radiation sickness: illness caused by overexposure of the body or a part of the body to ionizing radiations from radioactive material or x-rays. It is characterized by vomiting, diarrhoea, and in severe cases by sterility and cancer.

Radiation sickness degrees:

1. first-degree: D_eq=100-200 rems. Symptoms: periodically headache, running high temperature, nausea. Latent period: 2-3 weeks.

2. second-degree: D_eq=200-400 rems. Symptoms: similar to 1^st degree but they are stable and strong. Latent period: 1 week.

3. third-degree: D_eq=400-600 rems. Symptoms: unconsciousness, intradermal and mucous membrane bleeding, vomiting. Latent period: a few hours.

4. fourth-degree: D_eq=>600 rems. Without intensive medical treatment it’s fatal within 2weeks.

Blood cell affection:

- reducing quantity of red blood cells erythrocytes, which transport oxygen and carbon dioxide, combined with the red pigment haemoglobin, to and from the tissues, causes oxygen insufficiency, hypoxia, disturbs blood clotting.

- reducing quantity of white blood cells leucocytes, which fight viruses, weakens immunity.

All tissues and organs are broken into three sensitivity groups:

1. Very sensitive: blood and lymphatic tissues, intestine, genital organs, crystalline lens.

2. Poorly sensitive: kidney, lungs, liver, skin.

3. Stable: nervous system, heart, muscles, connective tissue.

Radiation exposure can be external or internal.

Background radiation dose reaches 100 mR.

On X-ray examination: photoroentgenography – 370 mR. Tooth – 3 R. 3 hrs watching TV – 0.5 mR.

Дата добавления: 2014-01-04