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Re: DeGaussing and Radiation Lore
Maybe off topic but contrubuting to history and lore of radiation work.....read on if you dare or delete if you must.
Jim & Brian,
I agree. But, this magnetic thing sounds a bit like "X-files" I'd suspect that its not the nails but other things (iron pipes, desks and such) in the walls. Maybe Dana Scully and Fox Mulder know the answer. The "truth is out there."
Jim Dunlap's story reminded me of different scientific explanation of the fate of x and gamma rays that is too precious not to share. Its all true of course, I got it from a Navy Chief.
A long, long time ago, the Navy had a nuclear medicine technology course at the Bethesda Naval Hospital campus. I was very fortunate to attend this great school while a student at Prince George's Hospital's nuclear medicine technology program. Every Friday we would take an exam. Tests were given around 1100 hrs leaving the afternoon for instructors to grade tests and "prepare" for future classes.....yeah right! Students were encouraged to hit the library and work on next week's assignments....double yeah! right!..... Everyone knows that as a student, your first task was get your exam grade! The ever professional and all knowing instructors could sense the tension among the students and their solution was to have a "Review Board" at the Petty Officer's Club on Friday afternoons.
Now in those days (mid '70s), the enlisted Clubs were not the "iced tea and crumpets, Evian water, fruit juice, yogurt muffin and politically correct establishments we have today. Beer was cheap, the snacks high chloesterol and higher in fat. The entertainment especially chosen by the Club Manager to assure good morale and high club profits, ie.,....... a cheap band with lots of dancing girls in mini skirts and boots that were made "for walkin'." Bob Hope, eat your heart out! We'd grab some front row seats, pull up a couple of tables and huddle around the instructors listening to the instructor's exam "debrief" between numbers. We paid very close attention of course. To what, I won't say.
One afternoon a young sailor medic drifted over to the table. He very politely asked one of the salty instructors what the little silver "thingie" was we were all wearing. Realizing that this kid was well into his cups and as green as a too fresh banana, Chief looks down at his dosimeter and says "You mean this thing?"
"Ah, yahhh Chief."
"Well son, let me give you some instruction." says the Chief, un-clipping his dosimeter.
Now, in the good old days, before cut backs and base closings, military dosimeters were things to behold, if not worship, as works of art. Polished stainless steel, all metal, a flip top, and a little window on the front. They were beautiful. Probably designed by Raymond Lowey. Robust... sailor proof. They would survive an A- blast even if the wearer was toast. (Hey, someone has to determine your "terminal dose" and record it your dosimetry record!!) They were not that cheap junk we use today. Wearing one was a matter of prestiege. When you wore one, people knew you were really someone important, maybe a doctor, a scientist or at least someone who risked their life to protect yours. It was a badge of respect.
Chief continued with a most solemn expression and in a reverent, hushed, tone, leaning close to the lad.
"This son, is a dosimeter. All of us work with radiation. You know x-rays and such. Its dangerous that stuff, radiation ..... " (A just the right length pause to let this thought sink slowly in... ) Chief continued. " Here's how they work. You see this hole in the front? Well that's the aperture. X-rays come in through that little slot. On the inside (pulling out the film pack) is the collector. The collector has a special top secret coating that attracts the x-rays to it and traps them inside this case. The case is made of silver so we don't get radiation exposure. Works the same way fly paper catches flies."
The kid, fumbling with his bottle of Bud, weaving from side to side and eyes now as big as saucers stammers, "Doesn't it ever wear out or get full of radiation?"
"Sure," says Chief, with a sly Chiefy smile, as he flips open the dosimeter and taps it on the side of the pop corn bowl. "What a good question. When that happens we jus' open this little hatch and we empty them into a trash or butt can or what ever is handy."
Its true!!! I swear it. I heard if from a Chief Petty Officer.
Sometime I'll tell you about the stray gamma ray! :)
Just my story!!
Jim Myers
Respond to.... jhm@nrc.gov
>>> "Brian Rees Lab" <brees@lanl.gov> 01/28 8:34 AM >>>
Jim,
I occupied an office that had previously housed a powerfull magnet. The
metal studs contained enough residual magnetism to affect a serious effect
on my computer monitor. I never did get the fields measured though. Moving
the monitor around caused effects that would have been pretty fun in the
days prior to urinalysis!
Brian Rees
brees@lanl.gov
-----Original Message-----
From: Jim Dunlap <jim.dunlap@guardian.brooks.af.mil>
To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
Date: Wednesday, January 27, 1999 1:28 PM
Subject: Re: DeGaussing an MRI suite
> Are you pledging a fraternity? Periodically, a bunch of guys from one
> of the ivy league schools send a letter to Ann Landers describing some
> far-out, fabricated situation for her to reply to. She's pretty good,
> most of the time, about figuring out it was a joke. Your question
> reminded me of one I occasionally would get when teaching the
> 'uninitiated' lay person; viz., "What happens to the residual medical
> x-rays that aren't absorbed." My initial response was, "They bounce
> off of the patient, settle to the floor of the diagnostic radiology
> suite following patient exposure, and eventually are either swept up
> by the janitor or evaporate, but if you need to enter the room it's
> O.K.. because they'll just bounce off of you." Then I would tell them
> the truth. With regard to your question, I really don't have an
> answer, except to say I've never heard of residual "static magnetic".
> (Thats kind of catchy. Sort of like the internal dosimetry tables
> that Ken Skrable developed which have been referred to as the "Scrable
> Tables"). As an aside, but just a peculiar a phenomenon: I was once
> involved in a case with a hot cell where high-dose gamma sources were
> handled remotely, in which the thick glass window, after MANY years of
> exposure, 'shattered', due to being 'supersaturated' with electrons,
> but remained in the solid physical form. This apparently was because
> the glass was acting as a capacitor, and finally became
> 'supersaturated', and "exploded", similar to what happens when
> 'radiation trees' are produced when a piece of plastic is exposed to a
> very narrow beam of high energy electrons. So, maybe your question is
> valid. I too would be interested in an accurate discussion of this.
> Thanks.
>
> jim.dunlap@guardian.brooks.af.mil
>
>
>______________________________ Reply Separator
_________________________________
>Subject: DeGaussing an MRI suite
>Author: radsafe@romulus.ehs.uiuc.edu at guardian
>Date: 1/26/99 5:09 PM
>
>
>Has anyone has any experience in dealing with the residual static magnetic
>fields that remain in an MRI suite after a unit is removed?
>
>The residual fields can reach 2 mT. This is too low to be a real health
>concern, but it's enough to cause problems for electronics and its enough
to
>upset people.
>
>Degaussing is theoretically possible, but I can't find anyone who has
actually
>done it.
>
>
>John Moulder (jmoulder@its.mcw.edu)
>
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