Answer to Question #8929 Submitted to "Ask the Experts"

Category: Radiation Basics — Radiation Shielding

The following question was answered by an expert in the appropriate field:


I've been told that some linear accelerators contain depleted uranium in their shielding materials, but that modern linacs do not. We have Varian 2100 series linacs with 6-18 MV energies. What models or types of accelerators contain depleted uranium?


Depleted uranium (DU) is a byproduct of the nuclear fuel enrichment process. It is abundant and inexpensive. The chemical and physical properties of DU make it ideal for several applications. It is 67% denser than lead, has a high melting point (2070° F, 1132° C), and has a tensile strength comparable with that of most steels. Since it is cheaper than tungsten and denser than lead, it is an ideal compact shielding material for applications where space is a premium. DU metal and DU-metal alloys are commonly used as shielding and collimator material in industrial radiographic imaging and gauging devices and in medical diagnostic and therapeutic devices that contain radiation sources or medical linear accelerators.

However, as I mentioned above, there are more expensive alternatives to DU and in the light of costs and regulatory issues regarding disposal of "radioactive" material, hospitals or industries that use such devices may opt for buying devices that do not contain DU.

To determine what types and models of accelerators contain DU, I suggest you ask the manufacturer of these accelerators directly.

Kamran Vaziri, PhD

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 19 March 2010. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.