[ RadSafe ] Re: Thorium in gas lamps -gamma cal for Ge detectors Cs-137 in wood ash why such variability?

Stewart Farber farbersa at optonline.net
Sat Jun 24 12:23:16 CDT 2006

Dear Dr. Parthasarathy,

Thanks for awarding me an honorary doctorate. :-)

In terms of Cs-137 in wood ash from mature hardwoods as measured in my little study mentioned earlier, the magnitude of the variability is NOT accounted for  by the average Cs-137 deposition in the US.

While overall average Cs-137 soil deposition according to DOE EML [formerly HASL]  measurments from the 1950s to the 1970s in various regions of the US varied by a factor of about 4 at the max from hi to low, there was a variation in Cs-137 in woodash measured in my study from 300 pCi/kg ash to 25,000 pCi/kg ash. This approximately 100 fold variation in Cs-137 in specific areas with only a 3 fold variation in overall Cs-137 areal deposition is apparently due to:

1) Wide variations in stable K in soil from one area to another. 
There is an inverse relationship between stable K in soil and Cs-137 uptake. Higher K, lower Cs-137 uptake. Lower K, high Cs-137 uptake. This has been documented in countless studies of uptake of Cs-137 by plants.

2) Wide variations in stable Cs in soil. 
Counterintuitively, the higher the stable Cs level in soil, THE HIGHER THE Cs-137 UPTAKE per unit Cs-137 areal deposition. This mechanism of a higher transfer factor of Cs-137 from soil to plant is well documented in the literature and is suggested from graphs of the data of Cs-137 in wood ash and the data available as to stable Cs in soil in the areas of wood ash measurments. The mechanism is that high levels of stable Cs bind up the exchange sites of soil minerals for Cs-137 as it is deposited to the soil.  Thus if the soil minerals are bound up with stable Cs, when carrier free fallout Cs-137 was deposited during the periods of active fallout during open air testing, the carrier free Cs-137 was subsequently available for uptake from soil,  rather than being bound to the soil. 

It's interesting on how major an impact high stable Cs in soil and high stable K can reduce the uptake to plants of unit concentration of Cs-137 deposition to soil.

Stewart Farber, MS Public Health
203 367-0791
PS: See you at the HPS Meeting in Providence ["It's Divine!"]
  ----- Original Message ----- 
  From: parthasarathy k s 
  To: Stewart Farber ; LNMolino at aol.com ; radsafe at radlab.nl 
  Cc: Stewart Farber ; radproject at aol.com 
  Sent: Friday, June 23, 2006 11:59 PM
  Subject: Thorium in gas lamps -gamma cal for Ge detectors Cs-137 in wood ash why such variability?

  Dear Dr Farber,

  Very interesting piece of work. What is the reason for such wide variability? It is not likely to be due to the presence of abnormal quantities of Cs-137  in the soil.Any thing known about the kinetics of the isotope in different plants? We know that Brazil nut trees absorb significant quantities of barium and along with it radium;this leads to the accumulation of high concentration of alpha activity in Brazil nuts. This food is known to be the most radioactive.

  I recall you referred to Cs-137 in wood ash in one of your earlier postings. Such information needs to be publicized widely so that public will  appreciate the intricacies in the interpretation of environmental survey data. How little we know about the miracles of nature?

  I remember once researchers in India got a single sample of fish from an effluent discharge point containing significantly higher concentration of Cs-137. There was no reason to suspect the analytical methodology used as the team was competent. The presence of this outlayer sample could not be explained. though  I felt that the sample must have picked up some contamination from the lab. a view that must have been derided as blasphemous! 

  Dr. Merryl Eisenbud once referred to the presence of uranium in peeches grown near  a Uranium enrichment facility. Mnay jumped to the conclusion that the source was the enrichment facility. Later someone demonstrated that uranium is present in appreciable quantities in cultivated farms far away from the industrial unit. The  uranium originated from the phophatic fertilizers used in culitvated farms. Public unnecessarily implicated the enrichment facility.

  I shall geatly appreciate receiving a copy of your final paper on the topic. If it is not in lectronic form can you send  a scanned copy. The material will be very useful while addressing physicians, engineers and technologists not involved in nuclear field. Informing them will be very useful as public will accept them as unbiassed specialists

  K.S.Parthasarathy Ph.D

  (Formerly, Secretary, Atomic Energy Regulatory Board, India)


  Raja Ramanna Fellow

  Strategic Planning Group

  Board of Research in Nuclear Sciences

  Department of Atomic Energy

  GN 18, Vikram Sarabhai Bhavan

  Mumbai 400094, INDIA


  91+22 25555327 (O)

  91+22 2 5486081(O)

  91+22 2 7706048(R)

  9869016206 ( Mobile)


  ----- Original Message ----
  From: Stewart Farber <farbersa at optonline.net>
  To: LNMolino at aol.com; radsafe at radlab.nl
  Cc: Stewart Farber <radproject at optonline.net>; radproject at aol.com
  Sent: Friday, 23 June, 2006 10:51:19 PM
  Subject: Re: [ RadSafe ] Thorium in gas lamps -gamma cal for Ge detectors

  Hi all,
  In terms of using a Thorium lantern mantle as a check source, you can also 
  use them to do a quick  two point energy cal on a germanium gamma detector.

  In the absence of other known energy check sources which might not be 
  available to you at the time, there are many easily seen gamma peaks to the 
  Th series present in a lantern mantle. Just select the 583 keV peak from 
  Tl-208 [30.9% abund] and the 2.615 MeV peak from Tl-208 [35.8% abund] center 
  your cursor on each of these two major peaka, set the peak energy to the 
  known major peak,  and voila your detector is ready to identify unknown 
  peaks by energy on subsequent counts.

  I used this technique to cal a portable Ge[Li] detector and MCA I had been 
  sent [without check sources] to try out back in the early 1980s. Did an 
  energy cal using the lantern mantle, took a bucket of [cold] wood ash out of 
  my Hearthstone free standing woodstove [a GREAT! unit] after returning home 
  from a trip,  and  counted the wood ash  [wrapped the detector in plastic 
  and inserted it into a bucket of ash to get good geometry] while I went out 
  for pizza on a Friday evening.  Came home to find dozens of peaks from the U 
  and Th decay series and ONE MAJOR PEAK that dwarfed all other peaks and had 
  exceeded the counts full scale.

  After expanding counts full scale from 512 counts to 32K counts full scale 
  [and all other peaks moved to the baseline in doing this], I moved the 
  cursor on the MCA display over to the one remaining large peak, and  found 
  the large peak had an energy of 661.6 keV.  Thus it was obvious woodash 
  contained major concentrations of fallout related Cs-137 which I later 
  verified to be typically 10,000 to 20,000 pCi Cs-137 per kg of ash in New 
  England, 25,000 pCi/kg in northern Florida, and about  300 pCi/kg in 
  California. Years later after having some quantitative gamma spec 
  measurements made of the first three wood ash samples from New England, I 
  authored a Feature Article to the HPS Newsletter:

  "Preliminary Study of Cs-137 in Wood Ash and Its Implications for BRC, Waste 
  Disposal, and Dosimetry", Health Physics Society Newsletter, Vol. 18[4]; 
  Feature Article, Pages 1-5, 1990

  This article called for scientists all over the US to make wood ash Cs-137 
  measurements in calibrated systems since the first quantitative sample from 
  my fireplace in Northern Vermont had Cs-137 measured at about 20,000 pCi/kg. 
  A mesurement near Vermont Yankee in southern VT over 100 miles distant from 
  my home showed Cs-137 at about 2,000 pCi/kg and this kind of variability of 
  Cs-137 in wood ash needed to be documented to understand spatial variability 
  and avoid false claims of nuclear facility impacts. These subsequent 
  measurments made by a dozen or more labs and research centers, with data 
  sent to me, resulted in a paper I prepared and presented "Cesium-137 in 
  Wood Ash -Results of Nationwide Survey, Presented at the Annual Meeting of 
  the Health Physics Society, Washington, DC, 1991.

  But of relevance to the original thread, all these subsequent measurements 
  of Cs-137 in wood ash started with one measurment using a portable, 
  hand-held Ge[Li] detector with a basic energy cal done with a Thorium 
  lantern mantle!!

  Stewart Farber, MS Public Health

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