[ RadSafe ] " Technology to detect radiation has progressed "

[Jim Hardeman]

George --
 
You hit the proverbial nail on the proverbial head -- the highest priority for use of handheld (and fixed portal) radionuclide identification systems these days seems to be detection of HEU and WgPu. For HEU in particular, there seems to be a large potential for "false positives" -- and each one of those false positives is going to result in a LOT of effort to properly adjudicate. God forbid that there should also be a concurrent neutron hit ...
 
Jim

>>> "Geo>K0FF" <GEOelectronics at netscape.com> 8/24/2007 12:33 >>>
Hi Jim, I have spent considerable time on the telephone discussing this very 
issue with SAIC, as their GR-135 does a similar thing with Fiestaware/U-Ore 
etc.

First it should be recognized that each of these manufacturers use a 
different algorithm to attempt to nail down certain isotopes, all of which 
are proprietary, and only discussed in general terms.

The more isotopes in the library, the more chance of a false reading.

SAIC generally looks for a *PAIR* of unique peaks before the software will 
give a positive analysis, but in some cases, only one will suffice if it is 
essentially uncluttered by interference peaks.

The more complex the mixture of isotopes ( multitude of peaks), the harder 
it is to make a positive ID.
Any system can identify a Cs-137 source, if all alone.

Fiesta Ware and other Uranium glazed pottery comes in two flavors. That made 
before WW2, contains purified Uranium with the natural mixture of 
U-235/U-238 intact (~.711% '235). This kind has a high 185 keV peak and will 
be identified as U-235, as the SNM ( special nuclear material) has a very 
high priority in the use of these instruments.

Generally all U bearing products for consumer use made after WW2 contain 
purified Depleted Uranium ( reduced U-235 proportion ~.2%). This may or may 
not be detected as DU.

These products contain Uranium chemically separated from its daughters in 
both cases, and do not therefore presently contain Radium.

Uranium ORE in its natural equilibrium state contains Radium and Ra 
daughters also. The Radium is identified as such by some combination of Ra 
and daughter peaks (a secret). Ra-226 is identified as NATural  U, seldom as 
Ra-226.

Here is an interesting report concerning false positive reading from the 
best of today's pony-and-shoot ID'ers.:
http://www.ortec ( http://www.ortec/ )-online.com/papers/la_ur_03_4020.pdf

There is no question that we are far from perfect in our technology, but the 
push is one, and the public may or may not ever
gain knowledge of the true state of the art ( as it should be).

One newly developed isotope Identifier, designed at LANL, is available under 
the brand name Quantrad Ranger Plus. In the $20,000 USD price range, it has 
a NaI(Tl) Gamma sensor and two He3 neutron sensors. The software is awesome, 
very adaptive, and will make a positive ID in as few as 2 or 3 seconds, 
depending only on the quality of the signal presented to it. Most other 
units have a fixed count time. I have personally used these and like them a 
lot, although they tend more towards the point-and-shoot.

As an industry, we are only a few months away from pocket Rad pager/ 
Cellphone combinations that will make the man on the street merely a mobile 
platform from which information is fed to a central control. Someone 
mentioned the lack of any Alpha-Beta detection in these units. Quite 
correct, and this too will have to be addressed. I myself was in Oak Ridge 
with mobile Gamma detectors at the time of the Sr-90 spill a few years back. 
Naturally, I could have driven through a foot of it and not detected 
anything ( pure beta emitter). Pure beta emitters are somewhat rare, but 
there are a number of them in everyday use: Sr-90, H-3, C-14, P-32 et. al.

The software/hardware will come up to speed, because it MUST come up to 
speed. We ( the USA) as a nation seem to be unable or unwilling generally 
embrace the high tech arts.

H1-B visas anyone?

George Dowell




----- Original Message ----- 
From: "Jim Hardeman" <Jim_Hardeman at dnr.state.ga.us>
To: "RADSAFE Mailing List" <radsafe at radlab.nl>
Sent: Friday, August 24, 2007 5:54 AM
Subject: Re: [ RadSafe ] " Technology to detect radiation has progressed "


Steven --

Good point. Even the best gamma spectroscopy algorithm is going to make an 
erroneous identification, and if the user has only enough training to 
blindly assume that the nuclide ID is correct, you can get yourself into a 
world of trouble. As an example, we were evaluating one of the new (I'm not 
going to use any brand names) rad-pager / nuclide ID combination units a 
while back -- in addition to the standard NaI probe used to DETECT elevated 
radiation, the unit also uses a small CZT detector to IDENTIFY the 
radionuclide(s) present.

One of my standard acceptance tests is to look at a red / orange FiestaWare 
platter -- makes a great check source w/ a contact radiation level of ~50 
uR/hr. I placed this unit on top of the platter and set it to count -- it 
took 10 minutes to acquire a spectrum (vs. 1 for more of the handheld units 
we use) and then only identified U-235 -- where most other units I've used 
would either return U-Nat or both U-238 and U-235 in roughly the correct 
proportions w/ a 1-minute count.

This instrument is being marketed to law enforcement folks -- folks who 
would normally wear only a rad pager, and then would have to call someone 
else to back them up w/ nuclide identification. I'm not sure, however, that 
at slightly elevated radiation levels even the most qualified gamma 
spectroscopist could make an accurate assessment. The only thing preventing 
these things from hanging on every street cop is the COST. I shudder to 
think what would happen should a similar mis-identification occur in the 
field ...

Jim Hardeman
Jim_Hardeman at dnr.state.ga.us 

>>> Steven Dapra <sjd at swcp.com> 8/23/2007 21:17 >>>
Aug. 23


At 09:12 AM 8/23/07 -0500, Geo>K0FF wrote:

>----- Original Message ----- From: <nssihou at aol.com>
>To: <idias at interchange.ubc.ca>; <neildm at id.doe.gov>; <sjd at swcp.com>;
><brent.rogers at ansto.gov.au>; <radsafe at radlab.nl>
>Sent: Thursday, August 23, 2007 6:17 AM
>Subject: Re: [ RadSafe ] " Technology to detect radiation has progressed "
>
>>
>>Most scrap yards now have radiation monitors and check metal as it enters
>>the site. Unfortunately, the radioactive material is not always seen if
>>shielded by a lot of other steel scarp. 


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