Ductwork for Oncology Room

If it is just xray machines, you should be ok above ceiling or side wall with regular galvanized duct, but supported with seismic Ip=1.5. However, MRI's are a different story - nothing metal is allowed near the machine. This biggest thing is calculating the various heat loads from the xray machines, autoclaves, computers, etc.

The properties of metals and metal alloys can be changed by neutron bombardment. One effect known as neutron embrittlement is a major concern for pressure retaining nuclear reactors. However; these effects occur over long periods of time at high exposure and high temperatures. Gamma, alpha, and beta exposure can also cause changes to polymers and ceramics that can be unwanted.

Gamma and X-Ray are electromagnetic wave type radiation that are indistinguishable from each other except for their source. Gamma coming from the nucleus of an atom and X-Ray for the electron cloud. The levels of exposure that any heating ventilation and air conditioning (HVAC) components are likely to see in an oncology treatment room are not likely to cause any material changes. The levels of ionizing radiation that would be required to cause detrimental effects to materials would probably cause some quite detrimental effects to patients as well. Also; those exposures are generally focused on the treatment area and are timed, so any exposure to equipment is intermittent.

Alpha, beta, and neutron are particles ejected from radioactive elements and isotopes as they decay. Alpha and beta might be used in seed type treatment, where a small seed of an alpha or beta emitter is placed in close proximity to cancerous cells. Because the particles (alpha and beta) do not travel far in air it is unlikely any equipment will be exposed. Neutrons can travel quite a distance, especially high energy neutrons. I do not know if they are used in Nuclear Medicine, but again, the level and duration of exposer that could cause material property changes would not be beneficial to the patient.

After having said all his I must warn against the use of Teflon tape or other components made with Teflon. Teflon, as it turns out, for all its wonderful uses does not stand up to radiation exposure. In nuclear power plants, even non radiation areas its use is not allowed.

I have used this data as a reference for imaging enclosures:

http://www.hps.org/publicinformation/ate/q5496.html

From there, you may be able to drill down and find information specific to your design. Hope this is of some use.

Thank you for your comments, we will proceed with gal duct.

Oncology is using different isotopes, not only for Xray. The nature of the radiation is mostly very concentrated to small parts to be treated. The most spread could occur on treatment of larger surfaces e.g. skin. The vicinity to the isotopes is the only point to be considered. Since metals can also store radioactive energy. Exposure= dose X time. I should discuss this item with the medical and safety staff. If you have their consent, you are good to go.

Exposure= dose X time.

Dont forget distance

I work in an oncology center with 4 "bunkers". Over the years and during several renovations the duct work has been refitted. We went from faced fiberglass duct to standard metal ductwork. The radiation did not damage any of the material uses.

The key how ever is to stop any radiation from "leaking" out of the room penetrations. If the room has a maze entry run the duct work down the maze and out of the room just above the entry door. If not be sure that the duct penetration is as far from the source as possible and if the unit is an accelerator make sure that the penetration is not in line with the beam. Also configured the ductwork as it exits the room in a dog leg configuration so that it can shielded with lead sheet of sufficient thickness, this shielding can be either inside the room or out. Make sure that you get the design checked out by a Radiation Safety Officer or a certified Medical Physicist of the institute or company.

Once construction is complete and the unit to deliver the radiation is in place and functioning, be sure to have a radiation leakage survey done to verify that all levels outside the room are with approved limits.

Bob

Thanks to all the extra comments, they are all excellent, our gal metal design is complete ready for submission to the medical and mechanical consultants.