Re: Disposal of Medical Linac Targets

[William V Lipton <liptonw@DTEENERGY.COM>]

Since this is NOT NRC licensed material, state regulations would apply.  You'd have to consult them to determine what

is "exempt."  Also keep in mind that, even if the material is exempt, the exemption probably does not apply to

disposal.



To perform a characterization of the components, you'd have to determine the radionuclide mix for each major

component.  This can be done in two ways.



1.  If you have a good idea of the materials in the target and the exposure history, you could perform a calculation,

using a program such as ORIGEN.  If different components have different material mixtures, you'd have to perform a

separate calculation for each mixture.



2.  You could send samples for laboratory analysis.  Again, you'd need a separate sample for each material mixture.



Once you had the radionculide mix, you could estimate the radionuclide activities from the dose rates, using a

program such as Microshield.



The opinions expressed are strictly mine.

It's not about dose, it's about trust.

Curies forever.



Bill Lipton

liptonw@dteenergy.com





alstonchris@netscape.net wrote:



> Does anyone care to offer opinions/experience to these folks?

>

> Cheers

> cja

>

> >Date:    Thu, 14 Nov 2002 10:10:33 -0600

> >From:    "William Kowalsky, Ph.D." <KowalsW@STFRAN.COM>

> >Subject: Hot Targets

> >

> >Jayne Knoche <knochej@HOTMAIL.COM> wrote:

> >

> >>Our old Clinac 20 has been disassembled for parts storage.  The target &

> >>scattering foils measure around 0.06 mrem/hr immediately adjacent.  (That's

> >>the activation remaining several months after last use.)  This radioactivity

> >>is enough that I can't ignore it, even though it's not a major problem.

> >>

> >>My immediate problem is deciding whether I can treat these objects as

> >>sources with exempt quantities, or whether I have to label them, etc.  The

> >>problem is that the regulations are written in terms of activity, but my

> >>survey meter gives dose equivalent rate.  Without knowing the mix of

> >>nuclides resulting from the activation, I don't know how to convert.

> >

> >If Jayne has a problem then it seems to me that all of us therapy physicists

> >have a problem.  We (almost) all have high energy machines with hot targets.

> >I for one do not keep any records of the radioactive sources in the bowels of

> >my 1800 and 21EX.  Perhaps the fact that we produce the activity ourselves

> >rather than purchasing it makes us exempt, just like homebrew software does

> >not have to have FDA clearance.

> >

> >Bill K.

>

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