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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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Certified Health Physicist
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