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Virginia Administrative Code
Title 12. Health
Agency 5. Department of Health
Chapter 481. Virginia Radiation Protection Regulations
10/21/2020

12VAC5-481-3450. Shielding and Safety Design Requirements.

A. Each therapeutic radiation machine subject to 12VAC5-481-3420 or 12VAC5-481-3430 shall be provided with such primary or secondary barriers as are necessary to ensure compliance with 12VAC5-481-640 and 12VAC5-481-720.

B. Facility design information for all new installations of a therapeutic radiation machine or installations of a therapeutic radiation machine of higher energy into a room not previously approved for that energy shall be submitted for agency approval prior to actual installation of the therapeutic radiation machine. At a minimum, facility design information shall include:

1. All therapeutic radiation machines.

a. Basic facility information including name, telephone number, and agency registration number of the individual responsible for preparation of the shielding plan; name and telephone number of the facility supervisor; and the street address, including room number, of the therapeutic radiation machine facility. The plan shall also indicate whether this is a new structure or a modification to an existing structure.

b. The primary areas where all wall, floor, and ceiling areas are struck by the useful beam.

c. The secondary barriers where all wall, floor, and ceiling areas do not have primary barriers.

2. Therapeutic radiation machines less than or equal to 150 kV (photons only). In addition to the requirements listed in subdivision 1 of this subsection, therapeutic radiation machine facilities that produce only photons with a maximum energy less than or equal to 150 kV shall submit shielding plans that contain, at a minimum, the following additional information:

a. Equipment specifications, including the manufacturer and model number of the therapeutic radiation machine, as well as the maximum technique factors;

b. Maximum design workload for the facility including total weekly radiation output, expressed in gray (rad) or air kerma at one meter; total beam-on time per day or per week; average treatment time per patient; and the anticipated number of patients to be treated per day or per week;

c. A facility blueprint or drawing indicating scale (0.25 inch equals 1 foot is typical); direction of north; normal location of the therapeutic radiation machine's radiation port; the port's travel and traverse limits; general direction of the useful beam; locations of any windows and doors; and location of the therapeutic radiation machine control panel. If the control panel is located inside the therapeutic radiation machine treatment room, the location of the operator's booth shall be noted on the plan and the operator's station at the control panel shall be behind a protective barrier sufficient to ensure compliance with 12VAC5-481-640;

d. The structural composition and thickness or lead or concrete equivalent of all walls, doors, partitions, floor, and ceiling of the room concerned;

e. The type of occupancy of all adjacent areas inclusive of space above and below the room concerned. If there is an exterior wall, the distance to the closest areas where it is likely that individuals may be present shall be included; and

f. At least one example calculation that shows the methodology used to determine the amount of shielding required for each physical condition (e.g., primary, secondary, and leakage barriers; restricted and unrestricted areas; and entry doors) and shielding material in the facility:

(1) If commercial software is used to generate shielding requirements, the software used and the version and revision date shall be identified.

(2) If the software used to generate shielding requirements is not in the open literature, quality control sample calculations to verify the result obtained with the software shall be submitted.

3. Therapeutic radiation machines over 150 kV. In addition to the requirements listed in subdivision 1 of this subsection, therapeutic radiation machine facilities that produce photons with a maximum energy in excess of 150 kV or electrons, or both, shall submit shielding plans that contain, at a minimum, the following additional information:

a. Equipment specifications including the manufacturer and model number of the therapeutic radiation machine, gray (rad) at the isocenter, and the energy and type of radiation produced (e.g., photon, electron). The target to isocenter distance shall be specified;

b. Maximum design workload for the facility including total weekly radiation output, expressed in gray (rad) at one meter; total beam-on time per day or per week; the average treatment time per patient; and the anticipated number of patients to be treated per day or per week;

c. Facility blueprint or drawing, including both floor plan and elevation views, indicating relative orientation of the therapeutic radiation machine; scale (0.25 inch equals 1 foot is typical); type, thickness, and minimum density of shielding material; direction of north, locations and size of all penetrations through each shielding barrier (ceiling, walls, and floor); and details of the door and maze;

d. The structural composition and thickness or concrete equivalent of walls, doors, partitions, floor, and ceiling of the room concerned;

e. The type of occupancy of all adjacent areas inclusive of space above and below the room concerned. If there is an exterior wall, the distance to the closest areas where it is likely that individuals may be present shall be included;

f. Description of all assumptions that were used in shielding calculations including, but not limited to, design energy (e.g., room may be designed for 6 MV unit although only a 4 MV unit is currently proposed), workload, presence of integral beam-stop in unit, occupancy and use of adjacent areas, fraction of time that useful beam will intercept each permanent barrier (walls, floor, and ceiling), and "allowed" radiation exposure in both restricted and unrestricted areas; and

g. At least one example calculation that shows the methodology used to determine the amount of shielding required for each physical condition (e.g., primary, secondary, and leakage barriers; restricted and unrestricted areas; small angle scatter; entry doors; and maze), and shielding material in the facility.

(1) If commercial software is used to generate shielding requirements, the software used and the version and revision date shall be identified; and

(2) If the software used to generate shielding requirements is not in the open literature, quality control sample calculations to verify the result obtained with the software shall be submitted.

4. Neutron shielding. In addition to the requirements listed in subdivision 3 of this subsection, therapeutic radiation machine facilities that are capable of operating above 10 MV shall submit shielding plans that contain, at a minimum, the following additional information:

a. The structural composition, thickness, minimum density, and location of all neutron shielding material;

b. Description of all assumptions that were used in neutron shielding calculations including, but not limited to, neutron spectra as a function of energy, neutron fluence rate, absorbed dose and dose equivalent (due to neutrons) in both restricted and unrestricted areas;

c. At least one example calculation that shows the methodology used to determine the amount of neutron shielding required for each physical condition (e.g., restricted and unrestricted areas, entry doors, and maze), and neutron shielding material utilized in the facility.

(1) If commercial software is used to generate shielding requirements, the software used and the version and revision date shall be identified; and

(2) If the software used to generate shielding requirements is not in the open literature, control sample calculations to verify the result obtained with the software shall be submitted.

d. The methods and instrumentation that will be used to verify the adequacy of all neutron shielding installed in the facility.

Statutory Authority

§§ 32.1-12 and 32.1-229 of the Code of Virginia.

Historical Notes

Derived from Volume 22, Issue 25, eff. September 20, 2006; amended, Virginia Register Volume 32, Issue 17, eff. June 5, 2016.

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