Lead Codes – Get to Know the Codes and Equivalences

Why Do We Use Lead?

Depending on the application, the radiation source’s output, and the environment’s layout, an energy-attenuating material will be required to ensure appropriate radiation protection is put in place to prevent those involved in the area from being exposed to the radiation when they are not supposed to be.

Traditionally, the use of lead sheeting for radiation shielding is due to its high density and malleability which makes it perfect for use in stopping radiation and as a building material that is used to cover all nooks and crannies. Although there are many materials denser than lead, this metal is cost-effective and readily available, which is why you won’t find gold in your shielding products anytime soon. This is also why lead has been used for soakers, chimneys, and gutter work in roofing by roofers for centuries. If only it wasn’t toxic to ingest!

What are Lead Codes?

Given that lead is the industry standard for radiation protection, the metal is used as a reference point to measure how much protection is needed for a particular area. Introducing, code system:

Many of our customers frequently ask us “what lead code do I need?” with regard to their radiation protection requirements, and rightfully so! Without knowing this information, you could quite easily obtain products that don’t satisfy the requirements of that project or end up paying for more than what you need.

For any work that involves radiation shielding, there will be a radiation protection advisor (RPA) involved that will deem the amount of protection needed for a given location surrounding the radiation source. The way that they will measure this level of protection is by allocating a code. For example, a wall may be specified in the RPAs report to have code 3 protection up to 2m tall. This means that you will need at least 1.32mm of lead or equivalent to stop the radiation sufficiently enough for the room to be deemed safe for operation. Each code of lead has a different thickness of lead assigned to it, each approximately 0.5mm in difference.

Why is the Use of Lead Codes Important?

If we only use lead for radiation shielding, then why can’t we just state the thickness of lead required rather than assigning a code?

The answer to this question is that lead isn’t the only material used in radiation shielding. Depending on the application, there are several alternatives that may provide more cost-effective or just more suitable for the purpose. A great example of this is lead glass. Obviously, lead itself isn’t transparent, so if we want to see the patient being imaged or observe the radioactive isotope without being exposed to ionising radiation, then we will need an alternative.

Lead glass is a special compound containing lead (no surprises here) that has a slight yellow hue but is entirely transparent. Just like lead, the thicker the lead glass is, the better it is at attenuating radiation. But 1.8mm of lead glass isn’t going to give you the same amount of radiation protection as 1.8mm of lead. In fact, to achieve a lead equivalence of 1.8mm (1.8mm Pb), the lead glass would have to be 6-7mm thick.

This is why different lead codes are important to the radiation protection industry. There are many common materials used to prevent radiation leakages such as concrete and specialised materials such as Knauff safeboards, but without lead codes, we wouldn’t know how much to use to give us the correct amount of protection for the job.

So What Does the Term ‘Lead Code’ Mean?

As we have already mentioned, different codes determine the thickness of lead metal necessary to prevent radiation in a given application from passing through. As the code gets higher, e.g, code 3 to code 4, so does the thickness of the lead. The greater the thickness, the further the radiation has to travel through the material, therefore dissipating its energy, and stopping it in its tracks.

This correlation between code and lead thickness can be translated easily for all materials, tested and documented by professional physicists. Each material used in radiation shielding can be tested under certain conditions to determine what thicknesses are needed to provide the same amount of protection as 1mm of lead, therefore allowing people to determine how much of that material will be necessary to achieve a certain code.

This is why we use the term ‘lead equivalence’, denoted by the units ‘mm Pb’. For example, you will often see your protection level for a product written out as ‘code 4, 1.8mm Pb’, meaning your product is rated for code 4 protection, equating to 1.8mm of lead. For the non-chemists out there, Pb is the atomic symbol of lead.

Commonly Used Codes

Code 3 – Veterinary and Dental applications
Code 4 – X-ray rooms
Codes 5 & 6 –  CT rooms.

Here is a chart to use when referring to lead codes and lead thicknesses.

Lead Code Table

What Code Lead Do I Need?

Although it is a legal requirement to get a radiation protection adviser to determine the right lead equivalence necessary to protect a room from radiation leakage, we can give you a vague idea of what codes are generally used for different applications.

Veterinary and Dental Practices

Vets and dentists fall pretty low in terms of radiation protection since the machines used in these practices are fairly low energy and used infrequently compared to their hospital counterparts. Code 3 lead is generally what is applied to these sorts of X-ray rooms, however, this may be more or less than what is necessary depending on the distance of the protection from the X-ray source.

X-ray Rooms

Conventional X-ray rooms used in hospitals are generally of higher specification than they are in Vets and Dentists. Code 4 lead is often suitable for these rooms.

CT Rooms

CT rooms are moving even further up the spectrum of radiation shielding as the application time of a CT is much higher than a conventional X-ray for radiography. Code 5 and code 6 are common lead equivalences used in these areas.

Nuclear and Industrial Applications

If you hadn’t already guessed, some of the heaviest lead jobs are involved in nuclear and industrial applications. The radiation that we deal with in these works is much higher energy and is under constant emission unlike X-ray rooms and CT rooms. Upwards of code 7 and code 8 lead sheets can be used in these areas. In fact, Raybloc has done doors with lead as thick as 20mm.

Here is a chart to refer to lead equivalences and the codes assigned to these thicknesses.

Final Words

There are many different purposes for lead metal. Roofers use roofing lead flashing for soakers, gutters, dormers etc. for roof cladding given it is waterproof and highly flexible. Outside of the roofing industry, rolled lead sheets can also be used in the manufacturing of lead-lined boards, panels, doors, and frameworks to enable a room to be completely radiation shielded from the inside out. Lead flashings are used to fill the gaps between boards so that there are absolutely no gaps in the lead work.

One thing is essential in all of this lead-lining work, the correct lead code you need is used to diagnose the radiation shielding for every part of the room, and this code is implemented at a minimum width at each and every point that the RPA report has specified. Using the wrong code could lead to radiation leakage or paying more than you need to.

F.A.Q.s

What are lead codes thicknesses?

Lead code thicknesses refer to the depth of lead associated with each code. For example, code 3 has a thickness of 1.32mm Pb. Lead sheets are available in different codes to suit your application. They can be purchased in rolls per square meter.

Why are lead codes important?

Knowing the correct code for your radiation shielding project will ensure you are providing enough protection for the job. Wrong lead equivalences could lead you to overpay for your project, or worse, cause you to fail to meet the criteria specified by an RPA.

What are the different codes of lead?

In radiation shielding, we use codes between code 3 (lowest lead equivalence) and code 8 (highest lead equivalence before reverting back to mm). Their lead equivalences are as follows: Code 3 – 1.32mm Pb, Code 4 – 1.80mm Pb, Code 5 – 2.24mm Pb, Code 6 – 2.65mmPb, Code 7 – 3.15mm Pb, Code 8 – 3.65mm Pb.

Which lead code do I need for my project?

To know what code to use, consult a radiation protection advisor (RPA) to specify this for your work. This will ensure that you receive the correct amount of protection by obtaining a report that will denote where lead shielding is required, and the amount for each area.

 

Need help and advice on lead lining installation? Download our eBook for a comprehensive guide.

Lead Lined Wall Panelling
Do not skip corners when it comes to radiation protection. It is what shields you, your staff, and your patients from harmful radiation. There is no compromise when it comes to people’s lives.

Call today to speak to one of our x-ray protection experts on 01902 633383 or email enquiries@raybloc.co.uk

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