Shielding Design X-Ray Room 2A02B.pdf

Radiation Shielding Design Calculations March 21st, 2018 Facility X-Ray Room XX

Radiation Shielding Design

R/F ROOM 2A25B

10/10/2022

VA CENTRAL CALIFORNIA

2615 E. CLINTON AVE.

FRESNO, CA 93703

Jeremy L. Corwin, MHP, DABHP Medical Physicist jeremy@corwinhp.com mailto:jeremy@corwinhp.com

Radiation Shielding Design Calculations October 10th, 2022 VA Central California - Fresno, CA R/F Room 2A25B

Shielding Design Summary

Shielding calculations were performed for the new x-ray system that will be installed in R/F Room 2A25B at VA Central California in Fresno, California.

A summary table of shielding calculations is at enclosure 1. An annotated floorplan with shielding requirements is at enclosure 2. The following is a detailed explanation of the required shielding on each wall.

Outline of Required Shielding

The following shielding specifications are the minimum amount of shielding required to reduce radiation exposures to below the current regulatory limits. Installation of shielding that is thicker than specified below is acceptable. All wall shielding must extend from the floor to a height of 7' 0" unless otherwise noted.

Chest Bucky / Recovery Room Wall - Wall A. The Chest Bucky / Recovery Room Wall requires 1.58 mm lead shielding.

Office Walls - Wall B. The Office Walls require 1.58 mm lead shielding. The shielding is located on the wall adjacent to the recovery room and also the wall near the locker room.

Locker Room Wall - Wall C. The Locker Room Wall does not require additional shielding. The existing two layers of 5/8” gypsum wallboard (≈ 28 mm total) will provide adequate shielding.

Control Wall / Window - Wall D. The Control Wall requires 1.58 mm lead shielding.

The Control Window must also be at least 1.58 mm lead equivalence and be at least 1 foot by 1 foot in size. Please note that the x-ray exposure switch must be mounted in such a manner that it is impossible for an operator to make exposures from an unprotected area. This can be accomplished by placing the switch at a permanent position at least 40 inches from the edge of the control area. Also, there should be at least 7.5 square feet of unobstructed floor space in the control area.

Hallway Wall - Wall E. The Hallway Wall requires 1.58 mm lead shielding.

Note: The specified amount of shielding will adequately shield the hallway as well as the higher occupied ultrasound control room beyond.

Hallway Door - Wall F. The Hallway Door requires 1.58 mm lead shielding.

Note: The specified amount of shielding will adequately shield the hallway as well as the higher occupied ultrasound control room beyond.

Ultrasound Wall - Wall G. The Ultrasound Wall requires 1.58 mm lead shielding.

Exterior Wall - Wall H. The Exterior Wall does not require additional shielding. The existing 304 mm of concrete will provide adequate shielding.

Floor: The Floor requires 0.79 mm lead shielding directly below the table, extending one foot past each edge laterally in which the table travels. The approximate location of the lead in the floor is provided in the enclosed floor plan. The remainder of the floor does not require additional shielding as the existing 101 mm concrete slab will provide adequate shielding.

Ceiling: The Ceiling does not require additional shielding. The existing 101 mm concrete slab will provide adequate shielding.

Methods and Assumptions

The shielding requirements above were based on the following information:

The proposed x-ray system is a radiographic / fluoroscopic system with a table and an upright image receptor. The facility will use Digital Radiography (DR). Calculations were performed for a DR system.

For the purpose of shielding calculations, the maximum allowable exposure limit for controlled areas is 0.10 mGy/week while the limit for uncontrolled areas is 0.02 mGy/week.

The maximum workload of 28 radiographic-only patients in addition to 2 R/F patients per 8 hours was provided by the facility. The provided workload was modified for a 40 hour work week to make 140 radiographic-only and 10 R/F patients/week. This modified workload was used for the shielding calculations.

The occupancies of surrounding areas are noted on the enclosed summary table of shielding calculations and the annotated floorplan.

The primary reference for these shielding calculations is NCRP Report 147, Structural Shielding Design for Medical X-Ray Imaging Facilities.

Please note the following:

These shielding recommendations are based on information provided by the facility at the time of this shielding design. If changes occur regarding the occupancy of surrounding areas, the type of x-ray system being used, or an increase in workload, additional shielding may be required.

California Radiation Control Regulations require that all x-ray machines be registered with the State of California, Department of Public Health. The Radiation Machine Registration can be completed online by following the link below.

https://cdph-rhb.powerappsportals.us/

It is believed that Los Angeles County and San Diego County are the only counties that require submission of shielding designs to their respective health departments.

Please check with your local county health department to determine if shield design plans need to be submitted for approval before construction begins.

Please keep a copy of this shielding plan at your facility indefinitely.

Thank you for allowing us to perform your shielding calculations. If you have any questions, please call me at (360) 736-6066.

Jeremy L. Corwin, MHP, DABHP Medical Physicist

CORWIN HEALTH PHYSICS INC

Enclosures:

Summary of Shielding Calculations Annotated Floorplan Appendix A - Recommendations for Shielding Penetrations Appendix B - Schedule of Commercial Lead Shielding https://cdph-rhb.powerappsportals.us/

Average kVp Radiography Fluoroscopy Total

Rad / Fluoro R/F Room 2A25B See NCRP 147 140 10 365 130 495

Wall Wall Primary or Type of Occupancy Distance to Description Description Secondary Occupancy Factor Occupied Area (m) Thickness (mm) Type

Chest Bucky / Recovery Room Wall A Primary Uncontrolled 1/20 2.13 0.98 Lead Chest Bucky / Recovery Room Wall A Secondary Uncontrolled 1/20 1.22 0.36 Lead Office Walls B Secondary Uncontrolled 1 2.74 0.78 Lead Locker Room Wall C Secondary Uncontrolled 1/20 4.11 6.12 GWB Control Wall / Window D Secondary Controlled 1 2.29 0.43 Lead Hallway Wall E Secondary Uncontrolled 1 4.27 0.55 Lead Hallway Door F Secondary Uncontrolled 1 6.25 0.36 Lead Ultrasound Wall G Secondary Uncontrolled 1/2 3.05 0.54 Lead Exterior Wall H Secondary Uncontrolled 1/40 1.83 13.88 Concrete Floor N/A Primary Uncontrolled 1 3.35 145.70 Concrete Floor N/A Secondary Uncontrolled 1 3.35 60.33 Concrete Ceiling N/A Secondary Uncontrolled 1 2.59 68.44 Concrete

Notes:

All wall shielding must extend from the floor to a height of 7' 0" unless otherwise noted.

1The specified amount of shielding will adequately shield the hallway as well as the higher occupied ultrasound control room beyond.

2In addition to the existing 101 mm of concrete in the floor, a layer of 0.79 mm lead shielding is required directly below the table. This shielding must extend laterally at least 1' 0" beyond each edge of the table.

Summary of Shielding Calculations VA Central California - Fresno, CA

R/F Room 2A25B October 10th, 2022

28 mm GWB None

Type of X-Ray Machine Room ID Rad Only Patients Per Week

Workload Information (mA-Minutes/week)

R/F Patients Per Week

The weekly workload information above was calculated using the designated workload values from NCRP Report No. 147, Table 4.7.

101 mm Concrete None

28 mm GWB 1.58 mm Lead

None

304 mm Concrete None

1.58 mm Lead1

28 mm GWB 1.58 mm Lead1

101 mm Concrete 0.79 mm Lead2

Shielding Specifications Calculated

Existing Shielding Additional Recommended ShieldingShielding

28 mm GWB 1.58 mm Lead 28 mm GWB 1.58 mm Lead 28 mm GWB 1.58 mm Lead

101 mm Concrete

28 mm GWB 1.58 mm Lead 28 mm GWB

Ultrasound Room

Exterior

Hallway

Locker Room

Recovery Room

Office Control Area Ultrasound Control Room

Locker Room Wall - Wall C.

The Locker Room Wall does not require additional shielding.

The existing two layers of 5/8” gypsum wallboard ( 28 mm total) will provide adequate shielding.

Hallway Wall - Wall E.

The Hallway Wall requires

1.58 mm lead shielding.

Hallway Door - Wall F.

The Hallway Door requires

1.58 mm lead shielding.

Ultrasound Wall - Wall G.

The Ultrasound Wall requires 1.58 mm lead shielding.

Chest Bucky / Recovery Room Wall - Wall A. The Chest Bucky / Recovery Room Wall requires 1.58 mm lead shielding.

Office Walls - Wall B.

The Office Walls require

1.58 mm lead shielding.

Floor: The Floor requires 0.79 mm lead shielding directly below the table, extending one foot past each edge laterally in which the table travels. The remainder of the floor does not require additional shielding as the existing 101 mm concrete slab will provide adequate shielding.

1.58 mm Lead Placement

0.79 mm Approximate location of Lead Placement in Floor

Scatter Radiation

Control Wall / Window - Wall D.

The Control Wall requires 1.58 mm lead shielding. The Control Window must also be at least 1.58 mm lead equivalence and be at least 1 foot by 1 foot in size. See the Outline of Required Shielding for additional information.

Exterior Wall - Wall H.

The Exterior Wall does not require additional shielding.

The existing 304 mm of concrete will provide adequate shielding.

Ceiling: The Ceiling does not require additional shielding. The existing 101 mm concrete slab will provide adequate shielding.

Appendix A – Recommendations for Shielding Penetrations

Shielding Screw/Nails: Penetrations made by screws/nails do not require lead “tabs” to cover the top of the screws/nails. The steel nails/screws generally attenuate radiation equally, or more effectively than the lead displaced by the screws/nails.

Shielding Joints: The joints between lead sheets should be constructed so that their surfaces are in contact with an overlap of not less than 1 cm. This can be accomplished by using lead battens, or by using drywall that is manufactured with the lead sheet extending beyond the edge of the drywall for adequate overlap.

Shielding Penetrations: Air conditioning ducts, electrical conduit, plumbing, and other infrastructure will penetrate shielded walls, floors, and ceilings. The shielding of the x-ray room shall be so constructed that the protection is not impaired by these openings or by service boxes, etc., embedded in barriers. The duct/conduit shielding thickness shall be equivalent to the displaced shielding thickness. Below are general shielding details for duct/pipe penetrations into a shielded surface where H is the diameter of the penetration.

1. Straight pipe/conduit penetration: Situations where there is a straight pipe/conduit penetrating a lead shielded surface require lead to line (wrap) the pipe/conduit twice the distance as the diameter/thickness of the pipe or conduit. See Detail 1 below.

Detail 1:

2. Curved elbow penetration: Situations where there is a curved pipe/conduit penetrating lead shielding requires lead to line (wrap) to line the entire top/backside of the elbow and pipe for 3 times the distance of the diameter of the opening. See Detail 2 below.

Detail 2:

3. Flat Panel Penetrations (electrical panels etc.). Flat panel penetrations can be shielded by either wrapping the entire structure (panel/box) being installed or by shielding behind the panel/box. If the lead shielding is installed behind the panel, the lead must extend beyond each side of the panel (penetration) by twice the thickness of the wall. For example, if the wall is 4 inches thick, the lead shielding must extend 8 inches beyond each edge of the cut-out section of the wall.

4. 90 degree elbow running out of the wall: Situations where there is a 90 degree elbow penetrating a lead shielded surface requires lead to line the top of the elbow up to the 90 degree turn, and then the back side of the pipe for twice the distance of the diameter/thickness of the pipe PLUS the thickness of the wall. See Detail 3 below:

Detail 3:

The above recommendations and details are adequate for shielding most common shielding penetrations. There may be exceptions where these methods are not appropriate for providing adequate radiation protection. Please contact Corwin Health Physics if there are other questions on how to appropriately shield a space.

Reference: The primary reference for these recommendations is NCRP Report 147.

Appendix B – Schedule of Commercial Lead Shielding

Thickness (mm)

Thickness (inches)

Weight in Pounds per Square Foot (PSF)

0.79 1/32 2

1.00 5/128 2.5

1.19 3/64 3

1.58 1/16 4

1.98 5/64 5

2.38 3/32 6

3.00 -- 7.5

3.17 1/8 8

3.97 5/32 10

4.76 3/16 12

5.55 7/32 13

6.35 1/4 16

8.47 1/3 20

9.52 3/8 24

12.70 1/2 30

19.05 3/4 45

25.40 1 60