[ RadSafe ] Deadly embrace: NRC policy can expose childrentoradioactivity, by retired........

[Dale Boyce]

A patient given 400 mCi of I-131 would have already had a thyroidectomy and 
a smaller ablation dose previously. I-131 uptake would be only a few percent 
in metastatic disease.

The old 30 mCi rule was based on a nominal 2 mrem/hr at 1 meter. So the 
initial dose rate for 400 mCi would be about 27 mrem/hr at 1 meter. The 
references I have seen for iodine elimination say the elimination half-life 
is significently less than a day, but from past experience 24 hours is a 
good rule of thumb.

So using the NUREG 1556 method the dose to the family member estimate would 
be:

27 mrem/hr * 24 h /ln(2) * 0.25 occupancy = 234 mrem

plus lets say 10% is bound and has an effective half-life of 7.7 days 
(biological and physical half-lives considered)

2.7 * 7.7 * 24 / ln(2)* 0.25 = 180 mrem

so 234 + 180 = 414 mrem

well under the 500 mrem value for release with instruction.

Dale


----- Original Message ----- 
From: "Perrero, Daren" <Daren.Perrero at illinois.gov>
To: "Steven Dapra" <sjd at swcp.com>; <radsafe at radlab.nl>
Sent: Tuesday, January 06, 2009 9:01 AM
Subject: RE: [ RadSafe ] Deadly embrace: NRC policy can expose 
childrentoradioactivity, by retired........


If we are assuming a point source exposure to 400 mCi of I-131 than the
gamma constant and distance formula would tell us that the dose at 10
feet would go as follows:

Gamma Constant = 0.283 microR/h per microCi at 1 meter. For 400,000
microCi that comes to a dose rate of 113 milliR/h which then gives us
2,700 milliR for the 24 period at 1 meter (3.3 feet).

Unfortunately there are significant errors encountered by going with the
simplified assessment above.  Medical physicists will tell you that
treated patients are not point sources and that a treatment dosage of
400 milliCi does not equal a 400 milliCi source in the thyroid.  Thyroid
update is more likely to be between 10 percent and 35 percent (we're
talking about treating unhealthy thyroids after all) depending on the
disease being treated.  Also, occupancy factors vary widely but can
easily go from 1/8 to 1/3.  One quarter is used in most cases.
Biological excretion is a huge term reducing factor during the first 24
hours as well.  Many hospitals will ask the patient to 'hang around'
until the first urination when a great deal of the unincorporated source
term is 'disposed' in the very early phase (first 8 hrs).  The single
biggest source of exposure is sleeping with patient, so most precautions
are driven by reducing that factor to the maximum extent practicable. A
search for authors Jeffry Siegel and Mike Stabin will provide some well
documented analysis of the counter point to Peter Crane's argument if
you'd like to dive into the subject further.

Daren Perrero
The opinions expressed are mine, all mine....
I'm with the government, I'm here to help you.
Daren.Perrero(a)Illinois.gov

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of Steven Dapra
Sent: Saturday, January 03, 2009 6:07 PM
To: radsafe at radlab.nl
Subject: Re: [ RadSafe ] Deadly embrace: NRC policy can expose
childrento radioactivity, by retired........

Jan. 3

         The PDF link posted by Celia is an article of approximately 600

words written by Peter Crane, a retired NRC counsel.  It was published
in
the New Hampshire Sentinel Source, the online edition of the Keene (NH)
Sentinel.

         Crane claims that the NRC instituted a "deregulation" of I-131,

and did so "at the behest of providers and insurers, eager to cut costs
and
increase profits."  (Presumably Crane means health care providers.)  He
says that (unspecified)  "international safety standards" call for
hospitalizing patients given more than 30 millicuries of I-131, but that
in
the US, patients are being sent home with "as much as 400 millicuries of

I-131 in their systems."

         Let us assume that a patient is sent home with 400 millicuries,

and that a family member is within 10 feet of this patient at all
times.  In 24 hours what will the exposure be to that family member?

Steven Dapra
sjd at swcp.com


At 03:50 PM 1/3/09 +0000, Celia wrote:
>In the news - FYI
>
>celia


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