Shielding Guides

August 5, 2025

Author: Max Haydon

Radiation Protection in X-Ray Room Design: What’s the Difference Between Primary and Secondary Radiation Barriers?

Why Radiation Barriers Are Critical to Safe Design?

In any diagnostic imaging environment, whether it’s a busy general radiology suite or a compact veterinary clinic, radiation protection is the foundation of safety. From general X-ray to CT and PET-CT procedures, controlled zones must be carefully designed to limit exposure to ionising radiation for patients, staff, and members of the public.

One of the most critical principles in shielding design is the correct classification of primary and secondary radiation barriers. At Raybloc, we manufacture and install shielding solutions, including lead-lined doorsets, shielded internal windows, and operator control screens, engineered to meet UK compliance standards and tailored to meet Radiation Protection Advisor (RPA) requirements.

What Are Primary and Secondary Barriers in Radiation Shielding?

Radiation barriers are classified based on their relationship to the X-ray beam:

Primary barriers are surfaces intended to intercept the useful (primary) beam directly from the X-ray tube.
Secondary barriers are designed to shield against scattered radiation and leakage radiation, which occur as the beam interacts with patients, detectors, and room components.

This classification directly impacts the type of material, thickness, and placement of shielding used, making accurate classification essential for safe, compliant, and cost-effective design.

Primary Radiation Barriers

Primary barriers are those surfaces expected to receive direct exposure from the X-ray beam. They are designed to attenuate the full intensity of the primary beam and are usually required in procedures such as general radiography or fluoroscopy.

Primary vs Secondary Radiation Barriers -Two same-sized rooms can require very different shielding layouts depending on beam direction.

Typical locations for primary barriers include:

Walls in radiation controlled areas where the beam is directed horizontally
Floors under ceiling-mounted C-arms or vertical bucky stands
Dedicated barrier walls in interventional rooms where beam orientation is fixed

CT rooms, however, are an exception. The X-ray tube in CT systems rotates 360°, meaning the direct beam does not consistently strike any particular surface. As a result, CT room walls are typically classified as secondary barriers, as per guidance in NCRP Report No. 147 and AAPM Task Group 108.

Common Materials for Primary Shielding:

Lead-lined plasterboard or plywood (typically 1.32 mm – 3.55 mm Pb equivalent)
High-density concrete or brick (thickness based on workload and beam orientation)
Chevron lead bricks (used in nuclear medicine or high-dose applications for lead equivalences greater than 7 mm Pb)

Secondary Radiation Barriers

Secondary barriers are designed to attenuate scattered and leakage radiation rather than the primary beam. Although scatter and leakage are less intense than the primary beam, cumulative exposure over time can pose a health risk, making secondary shielding equally essential.

Secondary barriers typically protect:

Operator control booths
Corridors and adjacent rooms
Doors and observation windows
Ceilings and floors between imaging rooms and occupied levels

Raybloc’s X-ray control screens, lead-lined doorsets, and internal windows are purpose-built for these secondary barrier applications, meeting the shielding specifications outlined in site-specific RPA assessments.

Common Secondary Shielding Products:

Lead-lined doors (typically 1.32 – 3.55 mm Pb)
Shielded observation windows using SCHOTT RD 50® lead glass
Raybloc operator screens (fixed and mobile models)
Shielded plasterboard or plywood panels
Brick or concrete (in sufficient thickness based on calculated dose)

Understanding the Differences: Primary vs. Secondary Protective Shielding

Aspect	Primary Barrier	Secondary Barrier
Radiation Type	Direct beam	Scatter and leakage
Positioning	In line with beam path	Outside the direct beam path
Lead Thickness (typical)	1.32 – 3.55 mm Pb (diagnostic); up to 25 mm Pb in high-energy or PET rooms	1.32 – 3.55 mm Pb or equivalent
Examples	Fixed wall behind bucky stand	Observation window or control room wall
Determining Factors	Beam direction, use factor (U)	Occupancy (T), workload (W), distance (d)

Design calculations rely on the U-W-T-d method:

U = Use Factor (how often a beam hits a surface)
W = Workload (how many exams per week)
T = Occupancy factor (who’s on the other side and for how long)
d = Distance from the X-ray source

These are assessed by a qualified Radiation Protection Advisor (RPA) who will generate the final shielding report, typically using models aligned with NCRP Report No. 147 and UK IRR17 guidelines.

Shielding Materials and Construction

Raybloc offers a variety of radiation shielding materials that can be specified based on the application and classification of each barrier:

Lead-Lined Plasterboard and Plywood

Supplied with lead bonded to the rear face
Standard sheet sizes: 2400 mm x 600 mm
Used in walls and ceilings for both primary and secondary protection

Lead Chevron Bricks

Ideal for bespoke installations and high-radiation zones like nuclear medicine where lead equivalence requirements exceed 7mm Pb.
Dry-fit assembly for flexibility and reusability

Lead-Lined Doorsets

Available up to 20 mm Pb equivalence
Fire rated to BS EN 1634-1 for up to 60 minutes
Optional integrated flush warning lights

Lead Glass and Internal Windows

Made with SCHOTT RD 50® lead glass (starting at 1.80 mm Pb)
Smart switchable options for privacy and infection control
Framed in FSC-certified timber or metal as required
Available with Sense-X® mood lighting technology

Operator Screens

Fixed and mobile X-ray screens designed for scatter protection in fluoroscopy, dental CBCT, and emergency X-ray suites
Available with Sense-X® mood lighting technology

Common Applications in Medical and Veterinary Facilities

Radiation shielding isn’t one-size-fits-all. Raybloc solutions are installed in a wide range of environments, including:

NHS and private hospitals (radiology, oncology, urgent care)
Veterinary imaging suites
Dental CBCT rooms
Interventional radiology and fluoroscopy suites
PET-CT and nuclear medicine facilities (requiring specialist shielding)

Each site requires a custom shielding strategy, balancing radiation protection, patient access, and spatial design.

Avoiding Misclassification: A Critical Step in Compliance

Misclassifying a barrier, such as designing a wall as a secondary barrier when it receives direct radiation, can result in unsafe exposure levels and non-compliance with IRR17. Conversely, over-engineering a wall as a primary barrier when it only needs scatter protection can inflate project costs unnecessarily.

Raybloc works closely with contractors, hospital Trusts, architects, and RPAs to ensure each barrier is correctly classified and constructed, using technical drawings, RPA-approved calculations, and certified materials.

Why Raybloc? Expertise You Can Trust

With over 25 years of experience in radiation shielding, Raybloc is a trusted partner for shielding across healthcare, research, veterinary, and industrial settings. All our products are:

Manufactured in-house using CNC precision and hand-built craftsmanship
RPA-tested for compliance with UK shielding requirements
Fire-rated and certified, including Declarations of Performance
Backed by technical documentation, installation support, and post-completion service.

FAQs

How do I know which walls need primary shielding?

A qualified RPA will perform a shielding assessment, analysing beam direction, equipment type, use factors, and occupancy levels to determine primary barrier locations.

Can Raybloc products be used for both primary and secondary shielding?

Yes. Raybloc offers flexible products in various lead thicknesses, suitable for both types of radiation exposure.

How thick should lead be in primary barrier walls?

Typical diagnostic applications range from 1.32 mm to 3.55 mm Pb. High-energy or PET areas may require up to 25 mm Pb, subject to RPA assessment.

Can I use standard plasterboard for secondary shielding?

No. Standard materials do not attenuate ionising radiation effectively. Use certified shielding products, such as lead-lined panels or tested concrete/brick constructions.

What is the RPA’s role in room shielding?

The RPA performs shielding calculations, reviews layout drawings, and specifies thicknesses to ensure radiation exposure remains below legal dose limits in accordance with IRR17.

Does Raybloc help with compliance documentation and certifications?

Absolutely. We provide all test data, fire ratings, and DoPs needed for building control and RPA submission.

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Max Haydon

Head of Business Development at Raybloc (X-Ray Protection) Ltd

"I’m Max, one of the Haydon brothers carrying on the family legacy of Raybloc alongside Founder (and Father), Sean Haydon. My late grandfather, Leonard Street - fondly nicknamed “Gangy” by me and my brothers - founded Raybloc alongside my dad, and their dedication to precision, proactivity, and continuous improvement inspires everything I do.

With a Master’s in Physics with Medical Physics from the University of Nottingham, I’m serious about creating valuable content for our customers but always keep things human and approachable. The most rewarding part of my job? Knowing that Raybloc’s radiation shielding systems make healthcare environments safer, improve patient experiences, and support NHS staff in reducing waiting times. It’s a great feeling to know the work we do has such a positive impact.

Outside of work, I’m usually strumming my guitar, singing along to The Beatles, or creating original music inspired by 60s and 70s legends. Looking ahead, I’m passionate about expanding Raybloc into new industries and forging partnerships with people who share our mission to make meaningful change."