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Re: shielding of a accelerator facility
One problem that comes to mind is capture gammas. The neutrons are not slowed down very much by the lead. Then, when they reach the
concrete, they are slowed down. When the thermal neutrons are captured, there are hi energy gammas emitted. If there's no lead to shield
them, this could result in hi dose rates. See NCRP 38, "Protection Against Neutron Radiation."
Before spending a lot of money installing an accelerator in a facility where it can't be used, a qualified person should perform a detailed
design calculation.
The opinions expressed are strictly mine.
It's not about dose, it's about trust.
Bill Lipton
liptonw@dteenergy.com
David W Lee wrote:
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>
> Carmen: Check "Health Physics" April 1992, Vol. 62, No. 4, pp.
> 359--362. Best regards David
>
> At 04:15 AM 04/07/2000 -0500, you wrote:
> >Hello,
> >
> >Does anybody know of any problem in having a 18MV accelerator for
> >radiotherapy treatments in a bunker (shielded room) whose walls are
> >made of lead + concrete?. That is, neutrons get first to the lead shield
> >and then to the concrete, and not the other way round, which is most
> >common among shielded bunker doors (in fact neutrons and fotons get
> >first to a paraffin layer and then to the lead).
> >
> >Thanks in advance.
> >
> >Carmen Conte
> >cconte@correu.gencat.es
> >************************************************************************
> >The RADSAFE Frequently Asked Questions list, archives and subscription
> >information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html
>
> DAVID W. LEE, CHP
> Los Alamos National Laboratory
> Radiation Protection Services
> Radiological Engineering Team Leader
> ESH-12, MS K483
> Los Alamos, NM 87545
> PH: (505) 667-8085
> FAX: (505) 667-9726
> lee_david_w@lanl.gov
>
> --=====================_1721384265==_.ALT
> Content-Type: text/html; charset="us-ascii"
>
> <html>
> <font size=3>Carmen: Check "Health Physics" April 1992,
> Vol. 62, No. 4, pp. 359--362. Best regards David<br>
> <br>
> <br>
> At 04:15 AM 04/07/2000 -0500, you wrote:<br>
> <blockquote type=cite cite>Hello,<br>
> <br>
> Does anybody know of any problem in having a 18MV accelerator for<br>
> radiotherapy treatments in a bunker (shielded room) whose walls are<br>
> made of lead + concrete?. That is, neutrons get first to the lead
> shield<br>
> and then to the concrete, and not the other way round, which is
> most<br>
> common among shielded bunker doors (in fact neutrons and fotons get<br>
> first to a paraffin layer and then to the lead).<br>
> <br>
> Thanks in advance.<br>
> <br>
> Carmen Conte<br>
> cconte@correu.gencat.es<br>
> ************************************************************************<br>
> The RADSAFE Frequently Asked Questions list, archives and
> subscription<br>
> information can be accessed at
> <a href="http://www.ehs.uiuc.edu/~rad/radsafe.html"; eudora="autourl">http://www.ehs.uiuc.edu/~rad/radsafe.html</a></font></blockquote><br>
>
> <br>
> <font size=3>DAVID W. LEE, CHP<br>
> Los Alamos National Laboratory<br>
> Radiation Protection Services<br>
> Radiological Engineering Team Leader<br>
> ESH-12, MS K483<br>
> Los Alamos, NM 87545<br>
> PH: (505) 667-8085<br>
> FAX: (505) 667-9726<br>
> lee_david_w@lanl.gov<br>
> </font></html>
>
> --=====================_1721384265==_.ALT--
>
> ************************************************************************
> The RADSAFE Frequently Asked Questions list, archives and subscription
> information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html
************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html