ISOCS

[atomicarcheologist]

I have been hearing about the ISOCS equipment being used in D&D applications for open field work.  There has been discussion of using the data obtained as survey data and also as sample data.  Is any one familiar with this approach?  Is it becoming prevalent or am what I hearing isolated cases, and if so what is the trend from those usages?

[atomicarcheologist]

I'm more interested in hearing of others experiences with ISOCS as a tool for doing D&D surveys in open field areas.  I am wondering about the usage of this equipment to replace meter scan and static readings.  I am attempting to verify what I have been told about the usage of the data obtained by ISOCS in lieu of taking soil samples.  Any knowledgeable  interface with this system would be appreciated.

[Rennhack]

I helped with the FSS Report for Yankee Rowe.  They used ISOCS in lieu of scanning in some survey units, they then also took soil samples.

RSCS worked closely with the NRC to get the technique approved.  -- They also used a truck monitor (array of ISOCS/Gamma Spec devices) to free release truck loads of soil.

If you are interested in more details, please contact RSCS:

Eric L. Darois, CHP
Executive Director
Radiation Safety and Control Services, Inc.
800 525-8339
603-778-2871 X29 (outside of USA)

[Khak-Hater]

The use of gamma spec detectors for open field applications predates ISOCS and was actually its forerunner.  Right after I got out of the Navy in '94, I sat in on a Canberra technical presentation/sales pitch by Frasier Bronson on sourceless calibration modelling for geometry correction for open field scans.  It inspired my Masters Thesis based on similar measurements that I performed on components in 3019 at ORNL in '95. 

They were conducting these open field measurements in the field at the time and were "in development" of the ISOCS application for other geometries (e.g., boxes, drums, etc.).  Bear in mind that they also had drum counters at that time, but those were calibrated with actual "blank" drums with sources distributed throughout them to simulate material distribution within the drum.  They came out with ISOCS [i.e., generic sourceless geometry correction calibration] a few years later.  Open field scans is its simplest and oldest application.

If you need more information on the history of the process or its technical details please contact me directly or go straight to the horse's mouth and contact Canberra [Their information may be more accurate but mine may sound like less of a sales pitch].

Hope this was helpful,

MGM

[Laning]

Answer 1. ISOCS does not replace scanning applications. Its designed for fixed point measurements.

Answer 2. Acceptance of the ISOCS technology depends on the regulatory agency you're dealing with. There's definitely some modeling voodoo that will need to be accepted by whomever has the responsibility for approving the data. I've found quite a few State Regulators unwilling to accept the ISOCS data alone in lieu of samples. My recommendation is to ask the question up front to whatever regulating agency you're dealing with.

[Rennhack]

Answer 1. ISOCS does not replace scanning applications. Its designed for fixed point measurements.

Answer 2. Acceptance of the ISOCS technology depends on the regulatory agency you're dealing with. There's definitely some modeling voodoo that will need to be accepted by whomever has the responsibility for approving the data. I've found quite a few State Regulators unwilling to accept the ISOCS data alone in lieu of samples. My recommendation is to ask the question up front to whatever regulating agency you're dealing with.

If I remember correctly, NJ was one of those states that does not like ISOCS.  -- As Mr Laning stated, you DO need to get your regulators buy-off on any technique you decide to use.

[atomicarcheologist]

A couple of questions

Rennhack  what statisical protocol was used to determine the soil sampling frequency in accordance with the  ISOCS technology?

Lanning  Why can't ISOCS data be used in lieu of scan data since it can look at many square meters simultaneously?

[Rennhack]

The soil samples were taken in a tradilional triangular patern, based on the standard MARSSIM approach of using the sigma of the historical data, etc.  The soil sample techniqui was right out of the manual, nothing changed.

As I said, they used it just to replace scanning in some locations. (They took static measurement with the isocs at overlaping locations).

[Llama]

I guess I had better weigh in. Mike is right we used soil sampling techniques IAW MARSSIM. We elected to use ISOCS however in lieu of scanning. We presented a Technical Based Document to the regulators defining the process prior to performing the surveys. The process was based on performing a series of fixed-point measurements in an overlapping pattern. We used 90 and 180 degree columination in the measurements depending on the proximety to the ISFSI. The modeling was developed for a 15cm soil depth with the premise that all the activity existed at the edge of the field-of-view to determine the EMC for Class 1 units. We used this methodology since it would present the least efficient situation and would be the most conservative. Additionally we surrogated the nuclide-specific measurements for the Hard-to-Detect radionuclides, where applicable. For Class 2 units we set the investigation levels at any plant-related activity identified. Investigations were performed with a combination of hand-held instrumentation (SPA-3) and soil sampling. We used the ISOCS software provided, however, one of our Engineers developed a script that took the measurement data from the local laptop and generated a report. The script then sent the report to our server which allowed the Engineers access to "real-time" scan data. Measurements could either be initiated locally in a peer-to-peer configuration or remotely using our wireless system. The regulators and the State agreed with our methodology and allowed us to use ISOCS. We did perform SPA-3 scans in areas where ISOCS was inaccessable (i.e. woods and hilly terrains). Did I miss anything Mike?

[Llama]

As a footnote to my last post. We used ISOCS in lieu of scanning, however, I believe that ISOCS could also be used in lieu of sampling. Since the methodology of using ISOCS instead of sampling is unique, a Technical Basis Document would have to be developed, backed by empirical data, much the same as when we proposed using it for scanning.

[Llama]

IIRC nobody has set that precedent yet,...

It's new ground,...

I've never known that to deter you 

btw: You going home this weekend?

[Rennhack]

Did I miss anything Mike?

I think that sums it up.

[atomicarcheologist]

As a footnote to my last post. We used ISOCS in lieu of scanning, however, I believe that ISOCS could also be used in lieu of sampling. Since the methodology of using ISOCS instead of sampling is unique, a Technical Basis Document would have to be developed, backed by empirical data, much the same as when we proposed using it for scanning.

Since you were able tu use ISOCS for scanning data accumulation purposes, I am thinking that you were shooting a much larger site than  1 square meter.  What size area did you look at on a per acquisition basis and what was the duration? 
Were you sampling only surface material or did you take below surface samples and to what depth?   If you sampled below surface, what protocol would you use to identify the sites for sampling at depth?

[Llama]

Since you were able tu use ISOCS for scanning data accumulation purposes, I am thinking that you were shooting a much larger site than  1 square meter.  What size area did you look at on a per acquisition basis and what was the duration? 
Were you sampling only surface material or did you take below surface samples and to what depth?   If you sampled below surface, what protocol would you use to identify the sites for sampling at depth?

ISOCS measurements were taken at a distance of 2 meters from the target surface, with a 90 degree collimator, yielding a nominal field-of-view surface area of 12.6 m². The model was developed for the area at a depth of 15 cm. and the soil density was adjusted for moisture content. The EMC was adjusted for a potential 1 m² area of elevated activity at the edge of the field-of-view. This was accomplished by applying a mean offset geometry correction factor derived by comparing MDC values for the entire field-of-view against a 1 m² at the edge of the field-of-view. The count times for the ISOCS measurements were adjusted to meet the a-priori MDAs set for the nuclides in the library, typically this was 600 seconds. Each open land area survey was comprised of scans and soil sampling performed to a depth of 15 cm. After backfilling operations in the industrial area were complete, we preformed a subsurface survey consisting of statistical sampling locations based on a triangular grid with a random start point. The samples were taken to a depth of 3 meters or refusal, whichever came first. Biased samples were also performed; however, they were taken to depths of up to 6 meters.

[Laning]

Llama,

Based on my original post implying ISOCS was relegated to fixed point measurements, I stand very corrected. Thanks for the information and the education.

Question: If I understand correctly, you were able to view 12.6 m2 of land per shot. Typical count time/per shot was 600 sec. Assuming a 2000 m2  survey unit, it would require ~159 shots for a 100% scanning coverage required of a Class 1 unit. So thats 159 shots x 10 min/ea = 1590 mins/60 min= 26.5 hrs of pure count time to complete scanning. Accounting for time to move from location to location 159 times...lets say 5 mins/per move; thats another 13.25 hrs.

Am I correct in assuming it took about a week to scan a Class 1 unit using ISOCS? Or am I once again showing my ignorance for all the world to see??

Thanks-Eric

[atomicarcheologist]

Llama,

600 seconds, that seems nominal for a count of that large an area, with a radius of 2 M.  Especially since most soil samples that I submit to labs for gamma spec on a Canberra type probe setup are for 600 seconds and 1800 if there are any questions regarding peaks.  Did you find that you had to do recounts for assessment of identified peaks?  I am beginning to think that with this distance setup, 15 cm depth, and count time you must have been dealing with MFP and excluded U235 during the a priori MDA considerations.

[Llama]

Eric,

You're numbers are correct, however, we were fortunate to have 4 ISOCS units. The Techs. would have them source checked and in the field by daylight. We would assay until just before dark when they would bring them in and perform a post source check. We had a awesome group of Techs.! The average time for a Class 1 open land area scan was 2 days, or less.

AA,

We didn't have to perform recounts for the assessment of identified peaks. The Canberra software performed very well and we tailored our library for the nuclides present. We did perform recounts rarely when there was a large temperature swing during the day resulting in a FWHM drift. We did exclude U235 and only considered the LTP listed nuclides. By using ISOCS we performed considerably fewer investigations due to the presence of NORM.

[atomicarcheologist]

Llama,

My mistake, my mistype.  I meant to ask about recounts for unidentified peaks.  I have heard that the temperature, humidity, etc. deviation during the shift, electronic noise, etc. had detremental effects on the data acquisition.  How would you account for low energy gamma isotopes that would be attentuated by the combination of soil and air during the compilation of your instrument library?

[Llama]

Llama,

My mistake, my mistype.  I meant to ask about recounts for unidentified peaks.  I have heard that the temperature, humidity, etc. deviation during the shift, electronic noise, etc. had detremental effects on the data acquisition.  How would you account for low energy gamma isotopes that would be attentuated by the combination of soil and air during the compilation of your instrument library?

We found that temperature and humidity did have an effect, albeit not often. In addition to the daily QC checks, each assay report was reviewed with respect to the K-40 peak to identify indications where amplifier drift impacted the nuclide identification process. If appropriate, recounts were performed where the drift impacted the ID process. The isotopes in our library, for the most part, had relatively robust gamma energies. This fact, along with the massimetric efficiency and density corrections, allowed us to adequately identify the nuclides in our library. Exceptions such as Am and Cm were addressed by treating them as HTD and accounting them by laboratory analysis. Should unidentified peaks appear on the report, the Engineer would provide resolution by identifying the peaks using the Kocher Tables.If the unidentified peak(s) was/were not resolved a recount was ordered.

[atomicarcheologist]

Since all the discussion to this point has been from a single site, I am concludint that this application is an isolated case.  Are there other sites using ISOCS? 

[Rennhack]

Since all the discussion to this point has been from a single site, I am concludint that this application is an isolated case.  Are there other sites using ISOCS? 

Or the people that use it don't read the forums.  (Am I allowed to say that?)

Didn't Fernald also use ISOCS?  They called it their "Real Time" Team.  Thats 2 out of 2 D&D's I visited in the last 2 years that used it.

I'm not sure who was in charge of it at Fernald.  But I can try to get some names, a know a few people that were there.

[stownsend]

They used it at BNL also. I wasn't the operator but was the HP for the soil remediation in 2000.

[atomicarcheologist]

Four sites out of all those undergoing D&D with open field applications.  That's not too bad.  Is anyone aware of any sites using this technology for buildings?

[atomicarcheologist]

No one has any knowledge of building D&D applications of ISOCS?  I am surprised as I have heard of this as well as the open field usage.  I have heard of this technology being used to determine waste stream allocation of material, has any one else?

[Rennhack]

No one has any knowledge of building D&D applications of ISOCS?  I am surprised as I have heard of this as well as the open field usage.  I have heard of this technology being used to determine waste stream allocation of material, has any one else?

It's used for everything.  You have to remember that not everyone that reads these forums are comfortable posting messages.