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

Radiation Shielding Design

X-RAY ROOM 2A02B

9/30/2022

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 September 30th, 2022 VA Central California - Fresno, CA X-Ray Room 2A02B

Shielding Design Summary

Shielding calculations were performed for the new x-ray system that will be installed in X-Ray Room 2A02B 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. Unless noted, all shielding must extend from the floor to a height of 7 feet.

Chest Bucky / Office Wall - Wall A. The Chest Bucky / Office Wall requires 2.38 mm lead directly behind the image receptor. The 2.38 mm lead must extend a minimum of 1 foot past each vertical edge of the image receptor, from the floor to a height of 7 feet. The remainder of the wall requires 1.58 mm lead shielding.

Chapel Wall - Wall B. The Chapel Wall requires 1.58 mm lead shielding.

Control Wall / Window - Wall C. The Control Wall requires 0.79 mm lead shielding.

The Control Window must also be at least 0.79 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 1 - Wall D. Hallway Wall 1 does not require additional shielding. The existing two layers of 5/8” gypsum wallboard (≈ 28 mm total) will provide adequate shielding.

Cross-Table / Hallway Wall 2 - Wall E. The Cross-Table / Hallway Wall 2 requires

0.79 mm lead shielding.

Note: The specified shielding applies to both the hallway wall and door. The specified amount of shielding will adequately shield the hallway as well as the higher occupied medical support room beyond.

Floor: The Floor does not require additional shielding. The existing 4” concrete slab will provide adequate shielding.

Note: The Floor requires at least 1.36 mm lead equivalence directly below the table.

According to NCRP Report No. 147, a shielding equivalence of 0.85 mm lead can be considered already in place by the attenuation of the grid, detector, and image receptor supporting structures (Xpre). For the primary beam shielding calculation, the contribution of Xpre was considered in addition to the existing 4” concrete slab.

Ceiling: The Ceiling does not require additional shielding. The existing 4” 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 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 patients per 24 hours was provided by the facility, but was considered to be imaged in 8 hours for the purposes of this shielding design. The provided workload was modified for a 40 hour work week to make 140 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 Rad-Table Rad-Chest Total

Radiographic System X-Ray See NCRP 147 140 350 84 434 Digital Radiography (DR) will be used

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

Chest Bucky / Office Wall A Primary Uncontrolled 1 2.36 2.06 Lead Chest Bucky / Office Wall A Secondary Uncontrolled 1 1.37 1.15 Lead Chapel Wall B Secondary Uncontrolled 1 1.37 0.94 Lead Control Wall / Window C Secondary Controlled 1 1.30 0.50 Lead Hallway Wall 1 D Secondary Uncontrolled 1/5 5.49 15.10 GWB Cross-Table / Hallway Wall 2 E Primary Uncontrolled 1 7.47 0.46 Lead Cross-Table / Hallway Wall 2 E Secondary Uncontrolled 1 6.48 0.18 Lead Floor N/A Primary Uncontrolled 1 4.42 1.36 Lead Floor N/A Secondary Uncontrolled 1 3.35 31.55 Concrete Ceiling N/A Secondary Uncontrolled 1 2.59 40.30 Concrete

Notes:

1The specified shielding applies to both the hallway wall and door.

2The specified amount of shielding will adequately shield the hallway as well as the higher occupied medical support room beyond.

All shielding extends from the floor to a height of seven feet unless otherwise noted.

4" Concrete None

Summary of Shielding Calculations VA Central California - Fresno, CA

X-Ray Room 2A02B September 30th, 2022

28 mm GWB 0.79 mm Lead

Type of X-Ray Machine Room ID Patients Per Week Workload Information

(mA-Minutes/week)

None

28 mm GWB 0.79 mm Lead1,2

28 mm GWB 0.79 mm Lead2

4" Concrete None3

3The Floor requires at least 1.36 mm lead equivalence directly below the table. According to NCRP Report No. 147, a shielding equivalence of 0.85 mm lead can be considered already in place by the attenuation of the grid, detector, and image receptor supporting structures (Xpre). For the primary beam shielding calculation, the contribution of Xpre was considered in addition to the existing 4” concrete slab. Please see the Outline of Required Shielding for additional details regarding Xpre.

Shielding Specifications Calculated

Existing Shielding Required ShieldingShielding

6" Concrete 2.38 mm Lead 6" Concrete 1.58 mm Lead

28 mm GWB 1.58 mm Lead

4" Concrete

28 mm GWB None

Hallway

Control Area

Hallway

Chapel

Office

Scatter Radiation

Control Wall / Window - Wall C.

The Control Wall requires 0.79 mm lead shielding. The Control Window must also be at least 0.79 mm lead equivalence and be at least 1 foot by 1 foot in size. See the Outline of Required Shielding for additional information.

Floor: The Floor does not require additional shielding. The existing 4” concrete slab will provide adequate shielding. See the Outline of Required Shielding for additional information.

Ceiling: The Ceiling does not require additional shielding. The existing 4” concrete slab will provide adequate shielding.

0.79 mm Lead Placement

1.58 mm Lead Placement

2.38 mm Lead Placement

Chest Bucky / Office Wall - Wall A. The Chest Bucky / Office Wall requires 2.38 mm lead directly behind the image receptor. The 2.38 mm lead must extend a minimum of 1 foot past each vertical edge of the image receptor, from the floor to a height of 7 feet. The remainder of the wall requires 1.58 mm lead shielding.

Chapel Wall - Wall B.

The Chapel Wall requires

1.58 mm lead shielding.

Hallway Wall 1 - Wall D.

Hallway Wall 1 does not require additional shielding.

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

Cross-Table / Hallway Wall 2 - Wall E. The Cross-Table / Hallway Wall 2 requires 0.79 mm lead shielding.

Note: The specified shielding applies to both the hallway wall and door.

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