Linear Accelerator Shielding

[lkjh345]

For a current project I will be designing a concrete shielding enclosure for a linear accelerator in an Oncology Clinic.

Has anyone designed such a sheilding enclosure?

If so, any pointers?

Who provided the recommendation for floor/wall/roof thickness and density of concrete requirements? The accelerator supplier? or did the coordinating proffesional (in my case the architect) have to hire an outside consulatant to perform the neccesary calculations, and provide recommendations for the concrete thickness and density.

Thank You.

 

[Taro]

In my experience, the architect hired a nuclear physicist consultant to provide shielding recommendations. Based on the physicist's recommendations, we worked with a ready-mix supplier to develop a ultra-heavyweight concrete mix so that the thickness of the walls and slabs was feasible. If I remember correctly, ordinary concrete needed a thickness of about 6 feet. The heavyweight concrete got the thickness down to 3 feet.

 

[JD2]

HAVE DONE SEVERAL OF THESE THINGS IN THE PAST. IN MY EXPERIENCE, IT WAS PART OF THE PACKAGE PROVIDED BY THE MACHINE MANUFACTURER/SUPPLIER (AS WELL AS DRAWINGS WHICH INDICATED ALL OF THE LITTLE "WE GOTTA HAVE" THINGS FOR THE MACHINE LIKE ANCHORAGES, BLOCKOUTS, PITS, ETC.) THE MACHINE MANUFACTURER/SUPPLIER HIRED THE PHYSICIST WHO, ALONG WITH THE MACHINE MANUFACTURER, DETERMINED THE TYPE OF SHIELDING (WHETHER CONCRETE, LEAD, ETC.) TO BE USED AND ITS THICKNESS ALONG WITH THE PHYSICIST'S ANALYSIS ASSUMPTIONS AND REQUIREMENTS, AND PROVIDED THESE TO THE ARCHITECT WHO IN TURN PROVIDED IT TO ME. THIS WAS THE STARTING POINT FOR DISCUSSIONS OR DESIGN REQUIREMENTS SUCH AS CONCRETE DENSITY, DIFFERENT TYPES OF SHIELDING, RESTRICTIONS ON AIR CONTENT, ETC.

THE LAST CONCRETE ONE I DID, WE WERE GIVEN WALL THICKNESSES OF 7' WITHIN A 10' WIDTH FROM THE ISOCENTER OF THE MACHINE (6' FOR THE CEILING/ROOF) AND 4'0" EVERYWHERE ELSE. DENSITY FOR THE CONCRETE WAS ONLY SLIGHTLY HIGHER THAN NORMAL CONCRETE - ABOUT 165 PCF. SOMEONE IN THE CHAIN DETERMINED THAT, IN THIS INSTANCE, IT WOULD BE CHEAPER TO PROVIDE THE LARGER QUANTITIES OF LIGHTER WEIGHT CONCRETE THAN TO PROVIDE HEAVY WEIGHT CONCRETE.

 

[SperlingPE]

Coordinating professional hired the consultant.
Check with your project owner. Find out what kind of contract he has with the supplier. The supplier could provide this information.

 

[271828]

I've also done 4-5 of these and my experience goes along with JD2's. The contractors didn't want to consider heavyweight concrete. I think that messed up their trucks.

 

[lkjh345]

All:

Thank you for your comments and advice. I apppreciate it.

 

[concretemasonry]

Depending on the size and shape of the enclosure, it is possible to get solid concrete block manufactured to very high densities using very dense iron aggregates or even steel shavings.

The block work well for interior applications depending on the logistics and timing relative to the equipment installation. Usually, they are made 4" or 6" thick to provide a convenient weight. They are laid in a multi-wythe solid wall using running bond and starting alternate wythes with 1/2 high units.

Just as with concrete, it is necessary to recognize the logistics in obtaining the natural or processed aggregates.

Dick

 

[Prepakt1]

Prepakt was involved in the design of this stuff in the past
I believe that that this type of biological screening was made by placing Iron pyrites, lead or steel pellets in forms (sometimes by hand to avoid voids}and then intruding a concretre mixture into the pellets. Way before my time but we may have some specs somewhere if you you dont find any other suitable source of info.

Intrusion Prepakt /marineconcrete.com

 

[jt12]

When I've done nuclear shielding, we usually had the option of concrete of `X' thickness or steel of 1/4*X thickness. When you start looking at the amount of floor space you are loosing for concrete, it may make sense in the big picture to go with something denser?