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Office of Homeland Security & Emergency Coordination
Radiation Safety Division (RSD)
United States Department of Agriculture

X-Ray Producing Equipment

DEFINITION

PART 1: KINDS OF X-RAY EQUIPMENT

PART 2: X-RAY EQUIPMENT POSSESSION

PART 3: REQUIREMENTS FOR USING X-RAY EQUIPMENT

PART 4: ADDITIONAL REQUIREMENTS FOR ANALYTIC X-RAY EQUIPMENT

APPENDIX A: GENERAL SAFETY CHECKLIST for Analytic Equipment

APPENDIX B: GENERAL SAFETY CHECKLIST for Cabinet Equipment

 


 

DEFINITION

X-ray radiation is a form of high frequency electromagnetic radiation, also characterized as high energy photon particles, usually called, x-rays. X-rays can be electronically produced when an x-ray tube is turned on and electronically activated. Turning the equipment off stops the production of x-rays. X-ray radiation is the same kind of radiation as gamma radiation, but generated by a different process and discovered and named under different circumstances. The two types of radiation are now usually distinguished by their origin: x-rays being electronically produced when electrons undergo energy level transitions as they orbit the atomic nucleus, while gamma rays are emitted by the nucleus as the result of radioactivity.

An x-ray tube is a vacuum tube that produces x-rays. It has a cathode, which emits electrons into the glass-enclosed vacuum, and an anode, to collect the electrons, thus establishing a flow of electrical current, known as the beam, through the tube. A high voltage power source, for example 30 to 150 kilovolts (kV), is connected across the cathode and anode to accelerate the electrons. Electrons from the cathode collide with the anode material, usually tungsten, molybdenum, or copper, and excite electrons within the anode material. About 1% of the energy generated is emitted, usually perpendicular to the path of the electron beam, as x-rays. The rest of the energy is released as heat. The x-ray energy spectrum depends on the anode material and the accelerating voltage, which can generate, modulate, or stop x-ray production.

In USDA, x-ray producing equipment includes a wide range of equipment types such as:

Cabinet Equipment:

  • Baggage and parcel inspection systems
  • Laboratory Cabinet x-ray units

Analytic Equipment:

  • Laboratory Fluorescence analyzers
  • Diffractometers

Medical Equipment

  • Diagnostic equipment
  • Bone Densitometers.

 

PART 1: KINDS OF X-RAY EQUIPMENT

 

Cabinet X-Ray Equipment

Cabinet x-ray equipment includes laboratory cabinet equipment, and baggage and parcel inspection systems. This type of equipment is typically regarded as low hazard.

  • A laboratory cabinet x-ray unit is a system with an x-ray tube installed in a shielded enclosure intended to contain the item being exposed. The enclosure protects people from the area of x-ray exposure. Shielding surrounds the volume exposed to x-rays and the shielding is an inherent part of the system. Cabinet x-ray systems are primarily used for industrial quality control inspections.
  • Baggage and parcel inspection systems are used at airport baggage screening and security points. Security applications range from screening baggage at airports to systems used to inspect trucks entering the United States.

 

Analytic X-ray Equipment

Analytic x-ray equipment is used in laboratory settings in research and industry, to make microscopic measurements and examinations of chemical compounds and sample materials on an atomic or nuclear scale. The intense beam of low-energy x-rays produced by analytical x-ray equipment can cause serious injury following a brief exposure to the primary beam. Such injuries are usually burns to the fingers and hands, which can be severe.

  • X-ray fluorescence is the emission of characteristic "secondary" (or fluorescent) x-rays from a material that has been excited by high-energy x-rays or gamma rays. The phenomenon is used in an x-ray fluorescence (spectroscopy) analyzer for chemical analysis, particularly in the investigation of metals, glass, ceramics, and building materials, and for research in geochemistry, forensic science, and archaeology. For laboratory equipment, the target material being analyzed is usually bombarded by electronically produced x-rays. This equipment should not be confused with portable x-ray fluorescent analyzers, which contain radioactive sources.
  • A diffractometer is an instrument for analyzing the structure of a material from the scattering pattern produced when a beam of x-ray radiation interacts with it. This scattered pattern is called diffraction. A diffractometer consists of an x-ray source and a detector. X-ray diffraction yields the atomic structure of materials by the scattering of x-rays through the electrons of the individual atoms in the sample. X-ray scattering techniques can reveal information about the crystallographic structure, chemical composition, and physical properties of materials ranging from simple inorganic solids to complex compounds, such as proteins. A diffractometer can also be used to identify unknown substances, by comparing diffraction data against a database. These x-ray systems are designed for use in a laboratory setting.

 

Medical Equipment

Medical equipment uses x-rays to assist in medical diagnosis, including the progress or remission of disease states. Medical equipment may also be used to deliver x-ray exposure for therapeutic treatment.

  • Diagnostic equipment (including dental and veterinary equipment) is equipment designed to generate and record an x-ray pattern in a live human or animal, providing the user with an internal diagnostic image. Simple diagnostic x-ray equipment is very effective at imaging gross abnormalities in bone structures, such as fractures. A typical radiation dose of an x-ray procedure is about 500 milli-Rems to the skin, which decreases with depth.
  • A bone densitometer is a diagnostic x-ray device that measures bone mineral density. It is based on “dual-emission x-ray absorptiometry.” It is also called a DXA scan, (previously known as a DEXA scan). The patient is exposed to two x-ray beams of different energies. When soft tissue absorption is subtracted out, the bone mineral density can be determined. The DXA scan is typically used to diagnose and follow osteoporosis, low bone density. It should not be confused with a bone scan, which diagnoses disorders of the bones such as infections, fractures, or tumors. A DXA scan radiation dose is approximately 50 milli-Rems, which is less than the amount of radiation that one receives on a roundtrip flight from California to New York.

 

PART 2: X-RAY EQUIPMENT POSSESSION

 

Authorized Users

There are two categories of authorized users: Permit Holders and associate users. An x-ray Permit Holder is a person whose training and experience have been reviewed and approved by the Radiation Safety Division, who is named on the Permit, and who uses or directly supervises the use of x-ray equipment. Any USDA employee seeking to acquire x-ray equipment must have a Permit issued by the Radiation Safety Division. Only the Permit Holder and the associate users listed on the Permit are authorized to acquire, possess, store, or use x-ray equipment.

An associate user is a person listed on the Permit who is authorized to work with the x-ray equipment under the Permit Holder’s supervision. The Permit Holder must be the supervisor of the associate users listed on the Permit. The Permit Holder may delegate specific tasks to associate users (such as doing surveys or taking measurements), but the Permit Holder is responsible for the safety and security of the x-ray equipment.

An x-ray Permit lists approved x-ray equipment, actual equipment inventory, storage rooms, and associate users. Once approved, a Permit Holder has access to the Permit tracking data base known as RSMS, (Radiation Safety Management System). The Permit Holder’s primary responsibility is to ensure that x-ray equipment, as listed on the Permit, is used safely and according to USDA radiation safety requirements. The Permit Holder must also see that procedures and engineering controls are used to keep radiation doses as low as reasonably achievable (ALARA).

Other individuals may operate cabinet or baggage scanning equipment after they have received appropriate training from the Permit Holder

 

Training Requirements

For cabinet and diagnostic equipment (which includes parcel and baggage scanners), the Permit Holder shall have received instruction and training in the principles and practices of radiation safety as specified by RSD, and in the performance and operation of the x-equipment. Before beginning work with x-ray equipment, associate users must receive radiation safety training. This may include specified RSD distance learning and an LRPO review.

See “Part 4: Additional Requirements for Analytical X-ray Equipment,” listed below.

 

Acquiring X-Ray Equipment

Before a purchasing agent can place an order to buy x-ray equipment on behalf of a Permit Holder, the Radiation Safety Division must review and approve the information on the purchase order. X-ray equipment may also be transferred from another USDA employee, who must also have an x-ray Permit. The Radiation Safety Division must review and approve such x-ray equipment transfers between Permit Holders, in order to review and update Permit and inventory data for both people. If a Permit Holder at a location leaves permanently, and the x-ray equipment is to be maintained at that location, it must be transferred to another Permit Holder at that location. X-ray equipment may also be transferred from a person or organization outside of USDA. Before x-ray equipment can be transferred from outside of USDA, the Radiation Safety Division must approve the equipment transfer.

 

Receipt of X-Ray Equipment

Upon receipt of new x-ray equipment, the Permit Holder must submit the following to the Radiation Safety Division:

  • “X-Ray Inventory Record” (RSS-29), or equivalent information;
  • manufacturer's information sheet and specifications for the equipment.

Upon receipt of x-ray equipment that is not new, but transferred from another user, similar, equivalent information is required.

 

Transfer or Disposal  

X-ray equipment cannot be transferred or disposed of without the approval of the Radiation Safety Division. If a Permit Holder leaves USDA without arranging for proper transfer of x-ray equipment, local management must maintain control of the equipment until the name of a new Permit Holder candidate can be submitted to the Radiation Safety Division. To remove x-ray equipment from a Permit, the x-ray equipment can be:

  • made non-functional, or
  • disposed of, or
  • listed on anther Permit, or
  • transferred outside of USDA;

 

PART 3: REQUIREMENTS FOR USING X-RAY EQUIPMENT

 

Radiation Safety Considerations

The requirements of the “Radiation Control for Health and Safety Act of 1960,” (21 CFR Part 1020) is the controlling legislation for this program which lists manufacturer safety specifications. X-ray producing equipment must be operated in accordance with these specifications and the manufacturer’s instructions.

Title 21: Food and Drugs
Chapter I: Food and Drug Administration, Department of Health and Human Services
Subchapter J Radiological Health
Part 1020 Performance Standards for Ionizing Radiation Emitting
§1020.30 Diagnostic x-ray systems and their major components.
§1020.31 Radiographic equipment.
§1020.32 Fluoroscopic equipment.
§1020.40 Cabinet x-ray systems.
§ 892.1170 Bone densitometers

Analytic x-ray equipment is not included in this regulation.

 

Surveys

Surveys for leakage radiation are to be performed:

  • when the equipment is installed,
  • when there has been significant modification or repair of the equipment, or
  • when conditions indicate a potential problem.

Radiation levels must not exceed 0.5 milli-rem/hour when measured at a distance of 5 centimeters from any surface on the unit. Radiation surveys are generally aimed at detecting areas where x-rays could be leaking through voids or breaks in the shielding. A standard Geiger-Mueller detector (GM) detector can be used to detect a problem. These surveys can be arranged in a maintenance contract with the manufacturer.

 

Posting of Signs, Labels, and Indicators

All x-ray producing equipment must be labeled with a sign stating “Caution – this equipment produces x-rays when energized.” A fail-safe warning light or device with words “x-rays on” must be located near any switch that energizes an x-ray tube. There must also be an ammeter indicator showing x-ray tube current.

 

Dosimetry Area Monitors

The Radiation Safety Division assigns 3 area monitors for each piece of x-ray equipment. An area monitor is like a personnel dosimeter, except that is it not worn by individuals, but placed nearby the x-ray equipment, to detect any possible radiation leakage.

 

Posting Requirements for Cabinet Equipment

The following documents should be placed near the controls of cabinet x-ray equipment (laboratory cabinet equipment and baggage scanners):

  • written operating instructions
  • Appendix B: general safety checklist (found at the end of this document)

 

Records Retention

The Radiation Safety Division maintains records of the purchase, transfer, and disposal of x-ray producing equipment as part of its overall inventory program. Records of radiation surveys and performance evaluations of the equipment are to be maintained by the Permit Holder for three years.

 

Audits

The Permit Holder must participate in a review of the radiation protection program annually to ensure compliance with the USDA radiation safety program. RSD will request an audit from Permit Holders or others involved in the location radiation safety program. The audits promote safety awareness and interaction between Permit Holders, the LRPO, and the Radiation Safety Division, and helps identify problem areas.

 

Inspections

The Radiation Safety Division (RSD) inspects each location where x-ray producing equipment is used. These inspections seek to identify and correct problems with radiation safety compliance. Inspections are usually done by appointment, with RSD Health Physicists acting as the inspectors. Inspectors compare the scope of x-ray activities against the Permits at the location. Inspectors look for additional physical and administrative compliance with this “comprehensive guidance and requirements” document. A report is transmitted to the location management, and other appropriate officials. If the report lists recommendations or cites violations, RSD works with the location management to resolve these report findings.

 

PART 4: ADDITIONAL REQUIREMENTS FOR ANALYTIC X-RAY EQUIPMENT

 

Hazard

Analytical x-ray equipment (diffractometers and laboratory x-ray fluorescent analyzers) can cause serious injuries, usually burns to the fingers and hands. Such accidents occur during repair and alignment of the equipment. Exposure hazards may also be associated with leakage or scatter radiation. To prevent exposures, instruments are designed with hood enclosures, interlocks, and beam shielding which should not be modified from the original manufacturer’s specifications.

 

Training

Additional training requirements apply for analytic equipment (and other x-ray equipment that produce high dose-rates). A Permit Holder is required to have a college degree at the bachelor level, (or equivalent training and experience in physical, chemical, or biological sciences or in engineering). The Permit Holder shall have received instruction and training in the principles and practices of radiation safety and in the performance and operation of the x-ray equipment.

All users must have specific training that is commensurate with the scope of assigned duties and proposed activities, so that they know how to operate analytical equipment and understand the hazards.

A competent training authority includes:

  • a college or university,
  • a manufacturer’s training course, or
  • some other professionally administered training organization.

Previous experience in school or in previous employment may be considered as qualifying training. Training assistance may also be available from the Radiation Safety Division.

 

Posted Documents

The following documents should be placed near the controls of each analytical x-ray unit:

  • written operating instructions
  • emergency procedures
  • Appendix A: general safety checklist (found at the end of this document)

 

Survey Meter

The Permit Holder must have access to a Geiger-Mueller (GM) detector with a radiation survey to be done whenever a new sample is placed in the beam, the experimental setup is changed, or equipment is replaced.

 

Dosimetry

Equipment operators must have individual radiation dosimeter badges.

 

Sign

There must be an additional sign posted next to each tube-head saying, "Caution High-Intensity X-ray Beam,"

 

Log

Equipment operators must maintain a log that includes date, operator, beam voltage and current, and time on and off.

 

Additional Safety Precautions

Since exposure of x-rays to the eyes may cause cataracts, it is recommended that safety
glasses be worn whenever instruments are modified or aligned.

Since electric capacitors in analytical x-ray equipment can kill a person even when the instrument is turned off, only a qualified technician or engineer should do maintenance or repairs.

 

 

APPENDIX A: GENERAL SAFETY CHECKLIST

for Analytic Equipment (X-ray Diffraction / Fluorescence)

Machine Identification:

Manufacturer:_______________________________Model:_____________________

Permit
Holder: ____________________________________Telephone:__________________

The Permit Holder and approved associate users must demonstrate an understanding of the operation of the machine before starting unsupervised work.

A fail-safe light must be visible to the operator indicating when x-rays are being produced.

Observe the current and voltage meters and use a survey meter to verify beam status.

Prevent access to the primary beam with interlocks, barriers, or administrative controls.

Do not operate the equipment with removed covers, shielding, or tube housings.

Do not operate the equipment with modified shutters, collimators, or beam-stops.

Do not override the safety interlock unless RSD approves a written procedure.

Do not use the safety interlock to turn the machine off; use the main switch.

Use a calibrated GM survey meter to verify shielding effectiveness and monitor radiation levels.

Wear personnel dosimetry when working with the equipment.

When changing samples, turn OFF the machine, or close the primary tube safety shutter.

Check radiation scatter with a survey meter after each realignment.

Secure unused ports to prevent accidental exposures.

Use key control of the equipment to secure it from unauthorized use.

Stop the primary beam by secured shielding that cannot be readily displaced.

Keep a log that includes date, operator, beam voltage and current, and time on and off.

Notify RSD if there is a concern regarding personnel radiation exposure

 

 

APPENDIX B: GENERAL SAFETY CHECKLIST

for Cabinet Equipment (X-ray Cabinet Equipment and Baggage Scanners)

Machine Identification:

Manufacturer:_______________________________Model:_____________________

Permit
Holder:________________________________Telephone:__________________

The Permit Holder and approved associate users must demonstrate an understanding of the operation of the machine before starting unsupervised work.

A fail-safe light must be visible to the operator indicating when x-rays are being produced.

Observe the current and voltage meters to verify beam status.

Prevent access to the primary beam with interlocks, barriers, or administrative controls.

Do not use the safety interlock to turn the machine off; use the main switch.

Do not override the safety interlock unless RSD approves a written procedure.

When changing samples, turn OFF the machine..

Do not modify the built-in shielding.

Secure cabinet units through a unit key control or room lock.

Notify RSD if there is a concern regarding personnel radiation exposure.