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RE: A Question for Power Reactor Types and others with portal monitors.



The radionuclide used in about 95% of the nuclear

medicine scans is Tc-99m, not Tc-99 which is a beta

emitter.  The concentration of Mo-99, with a half-life

of 2.75 days,  that is allowed to be administered to

is 0.15 microcuries per millicurie of Tc-99m.  I have

never seen any Mo-99 concentrations in patient doses. 





As your mention, the real issues is how sensitive is

your detectors.  If a patient is given a bone scan

with 30 mCi of Tc-99m, after 3 days there may still be

7 microcuries of activity present.  



Tl-201 is only used for heart scans.  While it is has

a half life of 3 days, there are Tl-202 and Tl204

contaminates.  However, you do not retain thallium

chloride.  





--- "Sewell, Linda" <LMS1@PGE.COM> wrote:

> Greetings All,

> 

> Nuclear Medicine patients have been an issue at

> power plants for years since most of us have portal

> monitors at the exit to our protected area, not just

> the radiologically controlled areas.  We've had 16

> folks in our "portal pass" program in the past year

> and we employee approximately 1100 people. 

> 

> We have found that Tc-99 alarms our portals for 1-3

> weeks.  I think it really depends on how much Mo-99

> there is as a contaminant.  

> 

> Tl-201 is typically less than a week but is

> dependent on what it's being used for.  

> 

> I-123 used for thyroid scans is gone pretty quickly,

> within a few days.  

> 

> I-131 for partial or complete thyroid ablation is a

> problem for 1 - 3 MONTHS and a dose rate issue for

> closely located co-workers for a few days.

> 

> We are starting to see F-18 and Ga-67 a bit now, but

> don't really have any good data yet.  

> 

> Another one that is generally only an issue if your

> lower energy thresholds are set below 80 KeV or so

> are the prostate cancer seeds.  The I-125 seeds are

> fairly straightforward but the Pd-103 seeds have a

> significant Zn-65 contaminant which can cause

> problems.  If the monitors "see" that low, the seeds

> are an issue for 1-3 years. 

> 

> Several of our workers have indicated that they were

> setting off the incoming gate alarms at our local

> landfill.

> 

> A common thread throughout which confuses the matter

> is that the folks doing the tests routinely tell the

> people that we'll never see it or that it will be

> gone in just a day or two.  The bottom line is, as

> well all know, if you start off with a BUNCH of

> activity (millicuries) you still have a BUNCH of

> activity (from a portal or gate monitor standpoint) 

> even after 7-10 half-lives.

> 

> Regarding Peter's issue on homeland security, it's a

> very valid point.  As I recall, I think the current

> plan is to start having nuc med groups issue the

> equivalent of our "portal pass" that indicates that

> the person has had a nuclear medicine treatment. 

> Also, if homeland security sticks with the FEMA

> alarm setpoints of 1 uCi that will reduce the

> impacts.  Most power plants set their portals to

> alarm at somewhere around 100 nCi.

> 

> Hope this provided some useful information.

> 

> Linda

> 

> Linda Sewell, CHP

> Dosimetry Supervisor

> Diablo Canyon Power Plant

> MS 119/1/122

> PO Box 56

> Avila Beach, CA 93424

> 805.545.4315 (voice)

> 805.545.2618 (fax)

> mailto:lms1@pge.com

> 

> 

> -----Original Message-----

> From: owner-radsafe@list.Vanderbilt.Edu

> [mailto:owner-radsafe@list.Vanderbilt.Edu]On Behalf

> Of

> Peter.Vernig@MED.VA.GOV

> Sent: Tuesday, April 06, 2004 12:26 PM

> To: Radsafe@list.Vanderbilt.Edu

> Subject: A Question for Power Reactor Types and

> others with portal

> monitors.

> 

> 

> Group,

> 

> I have been pondering the issue of Nuclear Medicine

> patients setting off

> Homeland Security radiation detectors.

> 

> There apparently have been scattered incidents so

> far but NRC published an

> information notice on it suggesting a verbal

> explanation and a business card

> be given to patients that could set off such alarms.

> 

> I did an impromptu, very quick and VERY dirty test

> using about 850 uCi of

> Tc-99m behind my back [to simulate in the body

> rather than a point source

> and set off waste alarms at about ten feet (3m).

> 

> Among the challenges in trying to inform patients

> and security personnel is

> how long a patient may set off an alarm.  We have

> had personnel here receive

> a heart study using Tl-201, usual dose 4 or 5 mCi,

> trip our waste alarm at

> "almost a month" after the procedure.  

> 

> I am slow on the uptake but I just realized this is

> something I have heard

> about at power plants and DOE facilities using

> portal monitoring systems.

> Can any of you out there give me any information

> about how long people that

> have had NM studies continue to trip portal

> monitors.  Any publications that

> address this?

> 

> 

> Any opinions expressed in this message are mine

> alone and do not necessarily

> represent those of the Eastern Colorado VA Health

> Care System, The

> Department of Veterans Affairs, or the United States

> Government.

> 

> Peter G. Vernig

> Radiation Safety Officer, VA Eastern Colorado Health

> Care System, 1055

> Clermont St. Denver, CO 80220, ATTN:  RSO MS 115;

> peter.vernig@med.va.gov;

> personal peter_vernig@hotmail.com; 303.399.8020 ext.

> 2447, FAX: 303.393-5026

> Alternate fax 303-377-5686

> "...whatever is true, whatever is noble, whatever is

> right, whatever is

> pure, whatever is lovely, whatever is admirable, if

> anything is found to be

> excellent or praiseworthy, let your mind dwell on

> these things."

> Paul of Tarsus

> 

>

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=====

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"Those who have not known the joy of standing up for a great cause of justice have not known what makes living worthwhile."

Paul Painleve, regarding the Dreyfus Affair, 1895



-- John

John Jacobus, MS

Certified Health Physicist

e-mail:  crispy_bird@yahoo.com



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