Re: Emission of cesium 137 -REPLY: Cs volatility/ Industrial Boiler Comparison

[RADPROJECT@aol.com]

In a message dated 98-06-27 01:50:00 EDT, you write:

<< Also, most steel plants in the more advanced countries have pretty
 decent pollution control systems.   I have a difficult time imagining that
 there was no dust collection system in place.   It is possible that it was
 bypassed.   However, if one was in place and operating, it would mean that
 there is several thousand pounds of highly contaminated dust - even if the
 system was only 50% efficient (modern ones have a much higher collection
 efficiency).   This would present a serious personnel hazard from both
 external exposure and potential internal deposition to plant workers.  >>

At the high temperatures present in a blast furnace it is likely any Cs-137
present would have been going up the stack in gaseous form. Several years ago
I  had called for a survey of Cs-137 in woodash after writing a feature
article in the HPS Newsletter [see Farber, S, "Preliminary Study of Cs-137
Uptake by Trees and its implications for BRC, Waste Disposal and dosimetry",
Vol. XVIII, No. 4, p. 1-5] I completed a survey of Cs-137 in domestic
fireplace or woodstove woodash which was presented at the HPS annual meeting
in Washington in 1991 [Farber, S and Hodgdon, A, Cs-137 in Woodash -Results of
Nationwide Survey". This paper and the nationwide news coverage it prompted
["Wood Ash - the unregulated radwaste?" - Science News] resulted in several
studies of Cs-137 in typical large kraft paper mills which burn vast amounts
of wood waste and "black liquor" solids. These studies were quietly performed
by the paper industry central research division.

The research at these paper mills showed that greater than 90% of the Cs-137
in wood [and in one case about 98%]was volatilized and lost up the stacks of
these mills given the very high temperatures in industrial boilers, and the
remaining fly ash and bottom ash were quite depleted of Cs. The activity
balance documented in these studies indicates that each of the 100 large kraft
paper mills in the US is releasing more airborne Cs-137 than the average
nuclear plant. A blast furnace must operate at temperatures even higher than a
commercial boiler.

This low residual Cs-137 in industrial woodash from paper mills stands in
sharp contrast to the woodash from home burning of wood which showed Cs-137
concentrations as high as 30,000 pCi/kg [ 1000 Bq/kg] of ash. The Sr-90
content of woodash is even higher than Cs-137 in a few measurements I made.
This is to be expected because the transfer factors for Sr vs. Cs from soil to
wood are quite higher and Sr is quite refractory vs. Cs.  The fascinating
thing is woodburners --who happen to be quite environmentally conscious --
commonly use the woodash from their home fireplaces as a soil amendment
[because of its potassium content]  in their "organic farming" practices. It
is clear that this practice leads to a buildup of Cs-137 in soil. Dose
calculations bound the dose from Cs-137 after many years of domestic use as a
soil additive at about 1 mR per year with the dose from Sr-90 being perhaps 10
times higher.  When I posed the tongue in cheek question in my HPS paper:
"Woodburners and organic farmers -Is it time to kiss your ash goodbye?"
newspapers and magazines were beating down my door to report on the issue.
Organic Gardening magazine, with a monthly paid circulation of just over
1,000,000 subscribers, published by Rodale Press, wrote one lengthy article on
woodash radioactivity. They reported to their environmentally aware, generally
anti-nuclear readers that radiation doses from using woodash in their gardens
with elevated levels of  Cs-137 was no big concern since it only resulted in
annual doses of a few mR vs. 360 mR/yr WBDE per NCRP-93!! If this point of
view were universally adopted by the environmental community it would have to
impact some of the dogmatic positions that theoretical doses from nuclear
waste disposal of  less that 1 mR/yr were some kind of obstacle to facility
licensing and operation.

Stewart Farber, MSPH
Consulting Scientist
Public Health Sciences
19 Stuart St.
Pawtucket, RI 02860

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