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Re: shielding
>References: <6b1923f8.356e2452@aol.com>
>Date: Thu, 4 Jun 1998 11:02:27 -0400
>Reply-To: Medical Physics Mailing List <MEDPHYS@LISTS.WAYNE.EDU>
>Sender: Medical Physics Listserver <medphys@lists.wayne.edu>
>From: "Dr. Robert Dixon" <rdixon@RAD.BGSM.EDU>
>Subject: Re: shielding
>To: MEDPHYS@LISTS.WAYNE.EDU
>
>Charles,
>The 2 mR/wk limit is all you need to use for design since you don't have
>a continuous radiation source.
>It is a common misconception that there is a 2 mR PER hr limit on
>instantaneous dose rate. Some state regs(following the NRC) do say no
>more than 2 mR IN ANY ONE hour, but since the accelerator beam is on
>only for about a minute for each field even if the measured
>instantaneous exposure rate is well above 2 mR/hr you would still be
>under the 2 mR in any one hour limit. If you design for 2 mR/wk it is
>clear that you will be well under 2 mR in any one hour. For anyone who
>would wish to argue with me about this, I further submit that since the
>accelerator beam is pulsed, that even if you measured 2 mR/hr with a
>survey meter, the instantaneous exposure rate would really be about
>1,000 mR/hr, so every accelerator in the country probably exceeds
>2mR/hr. I rest my case.
>Bob Dixon
>Charles Narayanan wrote:
>>
>> I have a linear accelerator designed for 2mr/wk shielding criteria. The
>> administration wants to know whether they can build an office above the
>> ceiling which is also designed for 2mr/wk.
>> what other factors will come into play. no skyshine involved at the present
>> time. Also is there an instantaneous dose limit involved. In other words can
>> one sit above the ceiling 8 hrs/day. Is there anything else I need to worry
>> about.The primary barrier thicknesscomes to about 8feet of concrete at the
>> present time.I am thinking of using high density(240or 304lbs/c.ft)Any
>> thoughts.
>> Charles Narayanan.
>>
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