SECTION 9: Radiation-Producing Machines

• Radiation-Producing Machines
• Acquiring Radiation-Producing Machines
• Precautions and Guidelines for Analytical X-Ray Equipment
• Precautions and Guidelines for Electron Microscopes

Radiation-Producing Machines (top)

A radiation-producing machine is defined to be either any machine primarily intended to produce radiation, such as:

• x-ray diffraction or x-ray fluorescence units
  
• electron microscopes
  
• medical x-ray equipment
  
• x-ray radiography units
  
• cabinet x-ray systems
  
• particle accelerators

or any electrical equipment which is not primarily intended to produce radiation but produces radiation greater than 0.5 mrem/hour at any readily accessible point five centimeters from its surface. Any electronic tube operating at a potential above 10 kV should be considered as a possible source of x-rays even though it may not have been designed for that purpose. Such equipment may include:

• high voltage rectifiers
  
• transmitting tubes (such as those found in commercial and some amateur radio transmitters)
  
• high power amplifying tubes (e.g., klystrons and magnetrons) used to produce microwave fields
  
• discharge tubes in which the gas pressure may be varied while studying electrical discharge.

Consult with Environmental Health & Safety (EHS) if there are questions concerning the radiation-producing potential of any equipment.

The possession and use of these radiation-producing machines is regulated by the New Jersey Department of Environmental Protection (NJDEP).

Acquiring Radiation-Producing Machines (top)

Purchasing Machines

Any proposed purchase and installation of a radiation-producing machine must be reviewed and approved in advance by the Radiation Safety Officer. EHS will register the new machine with NJDEP.

Loans or Other Transfers of Machines

EHS must be notified in advance when any radiation-producing machine is planned to be acquired as a loan, transfer or a gift from another institution or from any individual or department at the University. EHS will register a new machine or will update any previously registered machine’s registration with the NJDEP.

Precautions and Guidelines for Analytical X-Ray Equipment (top)

• Call EHS for radiation surveys and monitoring of any newly installed or relocated machines and especially when the machine has been modified for special experiments.
  
• A survey meter with a low-energy NaI detector, rather than a G-M detector, is the most appropriate detector to survey for the low-energy x-rays associated with x-ray diffraction work.
  
• Under normal operating conditions, always turn off the machine high voltage before opening the enclosure (for enclosed beam systems) or before taking any action which could expose the primary beam path (for open beam systems).
  
• Each day before using the machine, open and close the shutter a few times to check that the shutter is functioning properly.
  
• Never assume that the unit was left in a safe working condition by the previous user. Check the shielding and interlock status before turning the unit on.
  
• Do not bypass any safety device or interlock without the approval of the person responsible for the machine. When any portion of the safety devices are disabled, post a conspicuous sign stating the date, your name and listing what has been disabled. Return the machine to its unmodified state with all interlocks and safety devices operational as soon as possible.
  
• Do not work near the open, unshielded beam. However, if it is necessary to work near the unshielded beam (e.g., during system alignment):
  
  • Reduce the beam current and high voltage to the lowest possible settings to reduce exposure rates.
    
  • Keep hands and body as far as possible from the beam by using appropriate alignment tools.
    
  • You are in a potentially hazardous situation. Think before each step.
    
• Know what you are doing and where to expect problems. Be aware of the dangers. Do not work in a hurry or allow yourself to become distracted.
  
• In the event of a known or possible exposure to the beam, notify EHS immediately (see Section 1, Radiation Spill & Incident Procedures).

Precautions and Guidelines for Electron Microscopes (top)

• Call EHS for radiation surveys and monitoring of any newly installed or relocated microscope, when the machine has been modified for special experiments, and following any service work in which the column has been opened.
  
• Uranium, often as uranyl acetate, may be used as a stain in some electron microscope procedures. Uranium is regulated somewhat differently than other radioactive materials and can be purchased directly by the user from a vendor. However, once uranium compounds are brought onto the Princeton University campus, the compounds fall within the scope of the University’s NRC radioactive material license. Some degree of inventory control is required and waste materials must be disposed of as radioactive waste. Contact EHS when uranium compounds are acquired.