Regulations

9. Ionizing and Non-Ionizing Radiation Safety   (See also Ionizing and Non-Ionizing Radiation)

9.1 Introduction to Radiation at the Weizmann Institute

There are two kinds of radiation used at the Weizmann Institute:

1. Nuclear Radiation
Nuclear radiation differs from heat and other types of radiation in that each particle or photon has a sufficiently high energy to cause ionization.
  1. Radioactive particles
    • Alpha
    • Beta (electrons)
    • Neutrons
  2. Electromagnetic nuclear radiation
    • Gamma rays
    • X-rays
2. Non-Nuclear Radiation
Electromagnetic Radiation, including

9.2 Nuclear Radiation

Nuclear radiation is used at the Institute for the following research purposes:

  1. Tracers (e.g. Phosphorous-32, Iodine-125)
  2. Radiation Source for irradiating experimental animals
  3. Neutrons (used only in accelerators)
Naturally occurring or artificially made (nuclear reactor) substances consist of atoms which are unstable - that is they undergo spontaneous transformation into more stable atoms. Such substances are said to be radioactive and the transformation process is known as radioactive decay. Radioactive decay is usually accompanied by the emission of radiation in the form of charged particles or electromagnetic gamma rays. Radioactive decay is characteristic of the material, and is unaffected by the physical, chemical or biological environment.

9.2.1 Radioactive Particles

Alpha - radiation consists of helium nuclei with two units of positive charge.
Beta - radiation consists of a high-speed electron with one unit of negative charge.
Neutron - is an uncharged particle, that cannot cause ionization directly. It can transfer its energy to charged particles.

9.3 Electromagnetic Radiation

Electromagnetic radiation may be considered as a type of wave with a wide possible spectrum of frequencies and wavelengths. As the wavelength of radiation decreases, the energy associated with it increases, as does it's potential to ionize biological matter. Electromagnetic radiation includes both nuclear and non nuclear radiation, depending on the energy level.

9.3.1 Electromagnetic Nuclear Radiation

X-rays and gamma rays, with short wavelength and high energy, transfer their energy, as neutrons, to charged particles. The essential difference between the two types of radiation lies in their origin, whereas gamma rays result from changes in the nucleus and x-rays are produced by different x-ray machines.

Ionizing radiation is more energetic, and likely to ionize material and directly affect cell chemistry, destroying cells or causing genetic damage which may lead to cancer. The impact depends on the area affected, whether the energy is absorbed by the skin, or if radioactive materials are ingested or inhaled where they can react with vital organs. Sources emitting ionizing radiation at the Institute include tracer isotopes (e.g. H-3, Cr-51, I-125, P-32, S-35), X-ray apparatus, and nuclear accelerators.

9.3.2 Non-Nuclear Radiation

Non-ionizing radiation consists of less energetic electromagnetic waves, and is most commonly manifested by energy dissipation in the form of heat. The eye is the principal organ affected, but other potential exposure effects include inflammation of organs, fetal abnormalities, headache and fatigue. Sources emitting non-ionizing radiation at the Institute include microwave ovens, high pressure short-arc lamps (e.g. spectrophotometers and fluorometers), lasers, nuclear magnetic resonance (NMR) spectrometers, visual display terminals (VDTs), and U.V. lamps and tables.

Ultrasonic radiation consists of high speed sound vibrations that can only promulgate through a suitable medium, such as air or water. The nature of the type of radiation, the environment, and the characteristics and health of the biological organism are extremely important when ascertaining the biological damage likely to be encountered from exposure to radiation. Ultrasonic radiation is used for diagnostic, cleaning, and chemical purposes. Concentrated beams of ultrasound waves can be focused on a target, and reflected vibrations detected can be displayed as a moving image (e.g. echo reflection ultrasonography). Ultrasonic baths are used to 'shake off' dirt from delicate equipment. Ultrasound is also used to start or control chemical reactions, for example to make polymers.

9.4 Responsibilities and Authorization for Non-Ionizing and Ionizing Radiation

The responsible authorities, regulations and recommended safety practices depend mostly upon the radiation type. Radiation is managed at the Institute in accordance with the EHS regulations and guidelines of the Ministry of Environment, Ministry of Labor, Israeli Atomic Energy Commission and Institute policy and practices; and in accordance with the International Atomic Energy Agency (IAEA) and the International Commission on Radiological Protection (ICRP).

Both the Safety and Radiation Safety Officers are appointed by the Ministries of Labor and Environment. However, the Radiation Safety Officer is directly responsible for ensuring safe use of ionizing radiation, with the help of the Radiation Inspectors. In practice, the Radiation Safety Officer and the Radiation Inspectors are active in most aspects of EHS radiation concerns. Youth under 16 years, are forbidden to work with radioactive materials.

The Radiation Inspectors, under the Radiation Safety Officer, periodically test the radiation laboratories and devices for hazardous radiation levels, with special attention to the potential for transferring contamination. Every laboratory apparatus must be checked for radiation before service or repair work can be performed on them. Certain machines may only be operated by a trained user, at the request of the scientist and with authorization from the Radiation Safety Officer. The Radiation Safety Officer informs personnel of all innovations and changes in work procedures. The research team Directors are responsible for maintaining proper and safe work procedures for individual and general protection.

Any person intending to work with radioisotopes, or radiation emitting apparatus, must receive advance training and authorization from the Safety Unit, including medical examinations prescribed by the Industrial Hygiene/Medical Doctor. Only authorized persons can order radioactive materials, and all radioactive materials first arrives in the Central Radiation Laboratory for storage or redistribution. Every radioactive substance (including wastes) must be properly shielded and labeled. No materials may be shipped outside the Institute without authorization from the Safety Unit. Persons working directly or indirectly with radiation must follow all EHS procedures, and inform the Safety Unit if they suspect any problems with the equipment or their health that may be associated with radiation exposure.

9.5 How to Recognize and Protect Yourself and Others from Radiation

Entrances to radiation work areas and equipment are marked with the radiation hazard symbol and appropriate warnings, and/or have auditory or visual alarms. Entry is forbidden to many work areas when radiation-emitting equipment is operating.

Recommended safety practices and procedures depend on the type of experiment, procedures, and wastes. Special consideration is required when working with animals. The principle behind radiation safety is to control radiation hazards and assure that exposures are reduced to levels as low as reasonably achievable (ALARA), by:

  1. minimizing the exposure time.
  2. maintaining as much distance as possible from the radiation source.
  3. making every effort to shield radiation.
Other non-radiation hazards may be associated with radiation producing equipment or sources, including chemical, biological and electrical hazards (see appropriate Safety Manuals).