The following rules govern the use of analytical X-ray equipment at NC State University. These rules comply with the radiation safety standards recommended by the NC DRP and the American National Standards Institute (ANSI).

Open and Enclosed-Beam Analytical Systems:

1. Warning Lights: An easily visible warning light labeled "X-RAY-ON" must be located near any switch that energizes an X-ray tube and out side the room. It is to be illuminated only when the tube is energized. This light must be of a fail-safe design. Under certain circumstances it may be difficult to comply with this requirement, e. g. old donated equipment. In that case it is possible to obtain an exemption through Radiation Safety and providing the following information:

1. A description of the safety devices evaluated and why they cannot be used.
2. A description of the alternative method that will be used to minimize the possibility of an accidental overexposure.
3. Procedures that will be used to alert personnel to the absence of a safety device.
   

2. Labeling: All analytical X-ray equipment must be labeled with a conspicuous sign or signs that bear the radiation symbol and the words (or similar words):
   

1. "CAUTION - HIGH-INTENSITY X-RAY BEAM" on the X-ray source housing.
2. "CAUTION - RADIATION - THIS EQUIPMENT PRODUCES RADIATION WHEN ENERGIZED" near any switch that energizes an X-ray tube.
   

3. Beam trap: A beam trap or other primary beam shield must be provided to intercept the primary beam.

Additional Requirements for Enclosed-Beam Systems:

1. Chamber: The X-ray tube housing, sample detector, and analyzing crystal must be enclosed in a chamber (or coupled chambers) that prevents entry of any part of the body.
2. Ports: Access ports to the sample chamber must be of a fail-safe design that prevents X-ray generation or entry of the X-ray beam into the chamber when any port is opened.

Additional Requirements for Open-Beam Systems:

1. Safety device: An interlocked safety device, which prevents entry of any part of the body into the primary beam or causes the beam to shut off, must be provided on all open-beam systems. A Principal Investigator may seek an exemption from this requirement through the Radiation Safety Division and providing the following information:
   
   
   1. A description of the safety devices evaluated and why they cannot be used.
   2. A description of the alternative method that will be used to minimize the possibility of an accidental overexposure.
   3. Procedures that will be used to alert personnel to the absence of a safety device.
      
      

2. Open-beam systems must be provided with the following warning devices:

   1. X-ray tube status (ON-OFF) located near the X-ray source housing, if the primary beam is controlled in this manner; and/or,
   2. Shutter status (OPEN-CLOSED) located near each port on the X-ray source housing, if the primary beam is controlled in this manner.

3. Ports and Shutters: Shutters at unused ports must be secured in the closed position to prevent accidental opening. Each port on the X-ray source housing must be equipped with a shutter that cannot be opened unless a collimator or other device has been connected to the port, if the system was installed after January 1, 1980.

   Operating Procedures

   3. Procedure Manual - Normal operating procedures must be written and available to all analytical X-ray equipment users. Analytical X-ray equipment must not be operated differently from that specified in the procedure manual unless written permission has been obtained from the Radiation Safety Officer.

   4. Bypassing Safety Device - A safety device must not be bypassed unless written approval has been obtained from the Radiation Safety Officer. This approval must be for a specified time. When a safety device has been bypassed, a conspicuous sign must be placed on the X-ray housing bearing the words (or similar words), "SAFETY DEVICE NOT WORKING."
      
      

   Radiation Limits

   1. Enclosed-beam systems - The exposure rate during normal operations must not exceed 2.5 mrem/hr at a distance of 5 cm from the protective chamber walls.
   2. Open-beam systems - The exposure rate at the maximum rated current and voltage with all shutters closed must not exceed 2.5 mrem/hr at a distance of 5 cm from the X-ray tube housing.
   3. Generator Cabinet - The exposure rate at a distance of 5 cm from the surface of the X-ray generator cabinet must not exceed 0.25 mrem/hr.
   4. During normal operations in restricted areas, scattered radiation levels in accessible areas in any one hour must not exceed 37.5 mrem to the hands or 2.5 mrem to the whole body.
   5. During alignment procedures, the dose equivalent to the hands in any one hour must not exceed 37.5 mrem.
   6. The local parts of an analytical X-ray system must include sufficient shielding and be so located and arranged so exposure rates in unrestricted areas do not exceed 2 mrem/hr or 100 mrem/yr.
      
      

   Radiation Safety Surveys

   1. The Radiation Safety Division will conduct radiation safety surveys upon installation of x-ray equipment, following maintenance or tube replacement, and verify the tube identification via inventory at least annually.

   2. The PI must ensure that radiation safety surveys are conducted:
      
      
      1. Following any change in the initial arrangement, number or type of local parts.
      2. Following any maintenance that requires the disassembly or removal of a local part.
      3. During the performance of maintenance and alignment procedures that require the presence of a primary beam and the disassembly or removal of a local part.
      4. When a visual inspection of the local parts reveals an abnormality.
      5. Each area or room containing open-beam analytical X-ray equipment must be equipped with a suitable radiation survey instrument. If in doubt about which survey instrument to purchase, contact Radiation Safety for assistance.
         
         

   Repair and Alignment Procedures

   The following safety precautions must be taken to reduce risks during repair and alignment procedures:

   1. The main switch, rather than the safety interlocks, must be used to shut down the equipment.
   2. No X-ray tube must be used without a suitable housing to restrict the radiation to a well-defined beam.
   3. A sign stating "Interlocks Not Working" must be posted on the equipment when the interlocks have been defeated for alignment purposes.
   4. The Radiation Safety Officer must approve alignment procedures, other than those recommended by the manufacturer.
   5. Alignment procedures must be written and available to all users.
   6. If the dose rate in an unrestricted area is exceeded during the repair or alignment procedure, temporary barriers must be set up and the area must be properly posted. The area must be kept under surveillance until normal operations have been restored.
   7. After re-assembly, the Radiation Safety or the user must check the X-ray equipment for leakage radiation. The results of this survey must be documented.

    

   The following safety precautions should be taken to reduce risks:

   1. The smallest practical voltage and current should be used during the alignment procedure.
   2. Long-handled tools and extension devices should be used to reduce the risk of the hand entering the beam.
   3. Protective glasses should be worn during alignment procedures.
   4. Temporary shielding should be added to reduce scattered radiation levels to a minimum.
   5. Alignment procedures recommended by the manufacturer should be used.
   6. Two-man teams should be used during alignment procedures. One person should make the adjustments while the other person watches for safety problems.
      
      

   Cabinet X-ray Systems

   The rules in this section apply to cabinet X-ray systems. These requirements are in conformity with NC DRP regulations.

   1. A key-activated control must be provided to ensure that X-rays will not be generated when the key is removed.
   2. Each door of a cabinet X-ray system must have a minimum of two safety interlocks. Each access panel must have at least one safety interlock.
   3. A control, other than the safety interlock, must be provided to resume X-ray generation following X-ray interruption by a safety interlock.
   4. Two independent means must be provided to indicate when X-rays are being generated. One may be a milliamp meter labeled to indicate X-ray tube current; the other indicator must consist of an easily seen warning light labeled "X-RAY ON."
   5. A clearly legible and visible label bearing the statement: "CAUTION: X-RAYS PRODUCED WHEN ENERGIZED" must be posted near the controls that energize the X-ray tube.
      
      

   Operating Procedures

   Normal operating procedures must be written and available to all cabinet X-ray equipment users. Cabinet X-ray systems must not be operated differently from that specified in the procedure manual unless written permission has been obtained from the Radiation Safety Committee.

   Radiation Limits

   Radiation emitted from a cabinet X-ray system must not exceed an exposure rate of 0.5 mrem/hr at any point 5 cm from the external surface at the maximum rated current and voltage.

   A cabinet X-ray system must contain sufficient shielding and be located so exposure rates in unrestricted areas do not exceed 2 mrem/hr, or 100 mrem/yr.