Are compounds of radioactive elements also radioactive

Radioactive substances

Radioactive substances have the property of sending out energy in the form of radiation spontaneously and without any external influence and thereby converting themselves into other substances or isotopes, often through a series of intermediate stages. Radioactive substances may only be used with the approval of the competent authority under state law.

Radiation of radioactive substances

The rays of radioactive substances have the ability to "ionize" atoms directly or indirectly on their way through matter (air or other substances); they are therefore also called "ionizing rays". A substantial part of the harmful effect of rays on the human organism is based on this property of ionization. Ionization causes the electrically neutral (non-conductive) molecules and atoms to split into positively and negatively electrically charged particles, called ions. This creates ion pairs in the body tissue, creating new chemical compounds that act like poison on tissue and organ cells. If the radiation exposure is too strong, too long or too frequent, severe biological damage is caused. The rays themselves are neither visible nor noticeable.

Different types of radiation of radioactive substances

Types of rays: A distinction is made between alpha, beta and gamma rays. The type of radiation emitted by a radioactive substance depends on the types of atoms that make it up. Alpha and beta rays are so-called particle rays (corpuscular rays); Gamma rays are electromagnetic waves that are comparable to X-rays. Alpha rays are mainly emitted by the natural radioactive elements; the artificial radioactive substances (radio isotopes) mainly emit beta and gamma rays.

Alpha rays have a short range, e.g. B. in air about 4 cm; the depth of penetration is also small, e.g. B. only fractions of a millimeter in skin tissue. A sheet of paper would suffice to shield the radiation. Radiation to the body from the outside is therefore relatively harmless. However, if they come into close contact, for example through the absorption (incorporation) of dust or liquid into the body through the mouth and nose, serious damage occurs. Natural alpha emitters are z. B. uranium 238, radium 226, thorium 230; an artificial one is e.g. B. Plutonium 239.

Beta rays have a longer range, e.g. B. in air a few meters (up to 8 m). The penetration is also greater, e.g. B. in the human body to about one centimeter. Thin metal plates (e.g. sheet aluminum) are required to shield the radiation. Again, the main danger is the absorption of such substances into the body. Beta emitters are z. B. Strontium 90, Thallium 204, Phosphorus 32, Thorium 234.

Gamma rays have a long range - several hundred meters in air - and are very penetrative. As with X-rays, the human body is completely irradiated. For effective shielding, materials with the highest possible specific density must be used, e.g. B. lead; the thickness of the protective layer depends on the energy and strength of the radiation. The main danger lies in the external radiation on the body. Gamma emitters are z. B. Cobalt 60, Iridium 192, Radium 226 and Cesium 137.

In addition to these three components of "ionizing radiation" there is neutron radiation. It is created by the neutrons released during nuclear fission. These are above all the high-energy so-called fast neutrons. They do not ionize themselves, but they are penetrating and secondarily release strongly ionizing particles, whereby they have a high damaging effect.

Use of radioactive substances

When using radioactive substances, a distinction is made between enclosed and open radioactive substances. Enclosed radioactive substances are permanently enclosed in a tight, solid, non-radioactive (inactive) cover or are always embedded in solid inactive substances in such a way that radioactive substances are reliably prevented from escaping under normal operational stress. The dimensions of this envelope or embedding must be at least 0.2 cm. Sealed radioactive substances are z. B. used to measure the thickness and basis weight of running webs made of sheet metal, paper, plastic and the like., To measure the level of containers, to dissipate electrostatic charges through ionization of the air and to control welds (non-destructive material testing).

Open radioactive materials do not have a tight envelope; they are in solid, liquid, gas, vapor, powder or dust form. They are used industrially as indicators for marking or labeling, e.g. B. to elucidate reaction sequences in chemical processes, in metallurgy, in trace technology.

Any radiation exposure or contamination of people and the environment through radioactive substances must be kept as low as possible, even below the limit values, and any unnecessary exposure or contamination must be avoided. The basic rules of radiation protection when handling radioactive substances are:

  • Shielding of the radiation source using suitable materials of sufficient thickness (lead brick). This also includes protective clothing (suits, aprons, gloves, etc.).
  • The greatest possible distance from the radiation source in accordance with the range of the radiator in the open air (safety distance). The "square law of distance" applies: The intensity of the radiation decreases with the square of the distance from the radiation source. Therefore, long-handled tools, pliers, transport containers with long drawbars, remote grippers and the like are used when handling radioactive materials.
  • Stay in the vicinity of radioactive substances as short as possible so that the duration of the radiation exposure is limited to what is absolutely necessary.

In addition, it must be avoided that radioactive substances get into the body, e.g. B. via the mouth and nose (incorporation) or through the skin (contamination).

Since the radioactivity is neither visible nor noticeable, every work must be monitored by radiation protection measuring devices. The radiation dose absorbed by the individual employees must be measured continuously, e. B. with pocket dosimeters and film stickers on the work clothes. Limit values ​​of the permissible annual dose are regulated in the Radiation Protection Ordinance.

Occupationally exposed persons are persons who carry out "activities" or "work" within the meaning of the Radiation Protection Ordinance.

"Activities" include - to put it simply - the handling of artificially generated radioactive substances or naturally occurring radioactive substances, if this is wanted and carried out in a targeted manner. "Work" includes actions that can increase radiation exposure or contamination in the case of naturally occurring radioactivity. These are e.g. B. underground work in mines where radon can be released, work with thoriated welding electrodes and gas glow stockings as well as other work in which exposure to uranium or thorium and their decay products is to be expected. The occupation of flying personnel (exposure to cosmic rays) also falls under this term.

For the purpose of control and preventive occupational health care to the extent required, people who perform activities in accordance with the Radiation Protection Ordinance are assigned to categories A and B, depending on the level of radiation exposure (Figure).

The upper limit for all occupationally exposed persons is a maximum of 20 mSv per calendar year for the effective dose, for the organ dose 150 mSv (eye lens), 500 mSv (skin, hands, forearms, feet, ankles), 50 mSv (gonads, uterus, bone marrow) ), 300 mSv (thyroid, bone surface) and for other organs 150 mSv. Lower values ​​apply to persons under the age of 18 and pregnant women. For individuals in the general population, the upper limit of the effective dose inside and outside the company premises is 1 mSv per calendar year.

Occupational medical check-ups are mandatory for occupationally radiation-exposed persons of category A before starting an activity with radioactive substances. Annual medical check-ups follow. The working life dose must not exceed 400 mSv.

It is important to delimit and mark the various radiation protection areas (including the corresponding warning signs (figure)) and to check the dose limits permitted in these areas. Radiation protection areas are divided into controlled areas, restricted areas and transition areas (figure).

The local dose / dose rate or the concentration of radioactive substances in the air or the contamination of the workplaces must be measured in all radiation protection areas. The body dose must be measured on people who are in controlled areas, regardless of whether they are occupationally exposed to radiation or not. When leaving controlled areas in which open radioactive substances are present, people must be checked for contamination (hand-foot monitors at the exits).

Employees who work in restricted or controlled areas must be instructed about the working methods, the possible dangers and the protective measures before starting work. The instructions must be repeated at least once a year.

External personnel (e.g. maintenance, repair and cleaning staff, visiting researchers, temporary workers) may only be employed in controlled areas if they are wearing a dosimeter to monitor the radiation dose. In addition, it must be in possession of an official radiation passport and present it to the respective workplace. The radiation exposure recorded at the various places of employment is entered in the radiation pass. This ensures that all loads are recorded completely and without gaps.

During "work" according to the Radiation Protection Ordinance, during which naturally occurring radioactive substances may occur, the radiation exposure must also be kept as low as possible and protective measures must be taken for the remaining radiation.

For example, exposure to cosmic rays to which aircraft crews are exposed in their work must be controlled and limited. With an effective dose of more than 6 mSv in a calendar year, preventive occupational medical examinations must be carried out before the start of employment or continued employment and at one-year intervals. On long-haul flights z. B. Radiation exposures of 0.05 to 0.1 mSv per flight are achieved.

The accident insurance institutions have set up regional radiation protection centers for the care and outpatient monitoring of people who were exposed to increased radiation doses (list of centers in the leaflet: First aid in the event of increased exposure to ionizing radiation). Illnesses due to increased exposure to radiation are notifiable occupational diseases.

The entrepreneur (business owner, employer) is responsible for radiation protection and must ensure compliance with all protective regulations. He appoints radiation protection officers - in the required number - for the practical implementation of radiation protection, but remains responsible for fulfilling the legal obligations. The person responsible for radiation protection must therefore control the execution of the radiation protection officer's tasks using suitable means. In addition, he must issue a radiation protection instruction in which the protective measures to be observed in his company are listed.

Additional Information:

The offer of B · A · D on the subject of occupational medicine

The offer of B · A · D on the subject of occupational safety

literature

  • General administrative regulation for Section 40, Paragraph 2, Section 95, Paragraph 3 of the Radiation Protection Ordinance and Section 35, Paragraph 2 of the X-ray Ordinance ("AVV radiation passport")
  • Ordinance on protection against damage caused by ionizing radiation (Radiation Protection Ordinance - StrlSchV) (CHV 10)
  • UVV nuclear power plants (BGV C 16)
  • Guideline for the preventive occupational health care of occupationally exposed persons by authorized doctors, ed. v. Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU)
  • First aid in the event of increased exposure to ionizing radiation (BGI 668) / (GUV-I 668)
  • Radiation accident survey form (BGI 668-1)
  • Monitoring of metal scrap for radioactive components (BGI 723)
  • Handling of thorium oxide-containing tungsten electrodes in tungsten inert gas welding (TIG) (BGI 746)
  • Radon - a noble gas pollutes living, ed. v. Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU), 2006
  • Radon at indoor workplaces (BGIA 02/2003) (Link)
  • Radioactive substances - responsibilities of the state authorities, online information from the Federal Institute for Materials Research and Testing (BAM)

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