Lead door for Oncology radiation treatment room 5

[JGBJGB]

Hi
I have been asked to assist with the design and manufacture of a sliding lead door in front of an Oncology radiation treatment room. I have searched for some info on the internet but did not find adequate information. Can anyone assist please?
Regards
Johan

 

[CorBlimeyLimey]

What information are you looking for?
Size, weight, type of slide arrangement, type of Lead, Thickness of door or lead, ..... ?

 

[JGBJGB]

Hi

The typical specification (lead alloy type/thickness, boron wax?, gaps allowed etc.) - the room entrance is about 2m wide by 2,3m high.) I have been to a treatment room where they have a door installed, but obviously one can not see what is in it. It is driven by a CAME BK1800 motor.

Regards

 

[CorBlimeyLimey]

Do a search in Google for lead lined doors for plenty of leads.

In particular look at

http://www.radiationproducts.com/cad.htm

for some Acad drawings which might help.

 

[drawoh]

JGBJGB,

You may want to read up on the reason for lead.

When I took a physics course way back in college, we played around with some radioactive sources. The thing that shields you from radiation is mass. A kilogram of cotton candy will work as well as a kilogram of lead. The advantage of lead is that you need less of it, and it will not get eaten while you are not looking.

Definitely contact someone who works with radioactive sources to confirm this. I am trying to remember back thirty years here.

JHG

 

[TheTick]

A kilogram of cotton candy will work as well as a kilogram of lead.

Actually, it depends more on density. For that matter, much depends on the size of the nuclei of the shielding material.

Different materials are suitable for shielding different types of radiation.

Heavy nucleus elements like lead are good for shielding gamma radiation. Compounds with lots of hydrogen are good for lowing neutron radiation, Boron absorbs slow neutrons. Beta and alpha radiation can be stopped by a layer of cloth.

Word for the day: tenth-thickness
If you do not understand this term you should proceed no further.

"Customer satisfaction, while theoretically possible, is neither guaranteed nor statistically likely.--E.L. Kersten

http://www.EsoxRepublic.com

 

[BobPE]

a post worthy of a star my dear friend TheTick...and words of wisdom...tenth-thickness, IF YOU DO NOT UNDERSTAND THIS TERM (FIND AN ENGINEER THAT DOES)!!!!

BobPE

 

[nbucska]

I wonder if raw barite (BaSO4) would not be cheaper ?

<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032

 

[drawoh]

Tick,

Thanks. I sure am glad I qualified what I said there.

JHG

 

[ccw]

Hi JGBJGB,

In our business, because the lead *might eventually get eaten* (so they say), it is usually fully enclosed in a stainless or low carbon steel (field weldable) skin. Since this skin usually offers a reliable structure, the skin is usually assumed or designed to have all the load bearing capability, with the lead just along for the ride like water or sand. There are a few companies like National Lead, etc. that will melt and pour the lead into your steel cavitiy for a price.

A few tricks: The structure will be heated above 600F before pouring to assure the liquid lead does not freeze out and create voids during pouring (gas torches, etc). Therefore, design the structure to assure adequate heating of all the confinement surface can occur. Low carbon steel behaves better than stainless during heating and cooling, but would require painting. Make sure the steel confinement boundary is seal welded because the pour liquid lead is thin enough to find leak holes like water. Also the liquid lead is much heavier than water, so there will be significant hydraulic and/or hydrostatic forces against the steel confinment during the pour. Sometimes internal bracing or struts are required to maintain the shape, without distortion. Make sure the bracing does not provide any straight through unshielded paths. Lead shrinks during cooling, so usually it is done in stages (the no. of stages can be dictated by the capacity of the melt ladle.) There should be tell-tale or vent holes as well as fill holes that are seal welded after the pour stage or complete pour has cooled. Design the hole closures so that the weld does not generate lead fumes. Make sure threaded sockets or handling grips are included in the steel confinement/structure design to support the door during installation.

Check with the building engineer about specific siesmic requirements for structural support of non-structural heavy weight objects in the building.

Check with a bona fide health physicist and/or the OEM of the radiation sources in the room to determine the thickness required to attain attenuation of the sources to the levels desired on the protected side of the door. The protected side levels are always fractions of the source level, but never get to zero. Once you know the radiation source intensity, energy, and flux, and the target attenuation, for simple cases you can use the 1/10 rule - thickness required to attenuate the radiation dose 10 times from published shielding material characteristic tables. We use a computer modeling program like Micro-Shield to verify the minimum shielding thickness required for more complex and distributed radiation sources and/or mixed material. The steel material of the confinement also adds to the attenuation.

There are other materials that have higher density than lead and may be used in special cases such as tungsten, or spent uranium. The boron spec. indicates that you may have a mixed neutron/gamma radiation source or there may be secondary emission effects. Neutron flux can wander around corners, while gamma flux is usually considered straight line. Neutron shielding is usually a laminated thickness of absorption material with the lead or primary shielding material.

As a starting point, determine the thickness and material of the wall that the door goes in, if it is designed by others. Be careful, if the wall is concrete. There are admixtures for concrete that may have been used to increase the shielding performance over regular construction grade concrete. The door, when closed, should provide the same shielding performance as the wall.

CCW

 

[nbucska]

as CCW pointed out, lead may be eaten and it is certainly
damaging the environment. Barite may even be eaten without
any problem.

<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032

 

[HamishMcTavish]

Please bear in mind that it is not just 'thickness' of the lead on the door that you need to worry about but the elimination of any shine path, especially at the edges. What are your walls constructed of and have you designed an entrance maze? Have you considered the 3 dimensional picture...what is above or below your facility and does the floor/ceiling provide appropriate shielding.

I did a search on google for 'radiation shielding design' and found the enclosed which might help you

http://www.radiology.mcg.edu/seaapm/Symposium2005.htm

Attenuation of radiation depends on the "cross-section" provided by the shielding material for the type and energy of the radiation you are trying to shield against.

Regards, HM

No more things should be presumed to exist than are absolutely necessary - William of Occam

 

[arto]

There's an old shielding design book by Ted Rockwell that came in handy for calculating shield effect of different isotopes for shipping containers.