[ RadSafe ] Ongoing Criticalities Inside Leaking Fukushima Daiichi Unit 2

[John Ahlquist]

It is bothersome that the anonymous GLG Expert Contributor says it is 
“unequivocal” that on-going criticalities are producing more I-131 at Unit 2.   
From my reading of the TEPCO graphs, the I-131 to Cs-137 ratio changes in both 
directions. For example from April 20-22 the ratio changed from around 5 to 
nearly 1 on Unit 4.  Does this mean more Cs-137 is being produced?  I doubt it.  
We are given log scales, no error bars and no discussion on measurement or 
sample collection quality.  The physics and chemistry of release and migration 
of the stew at risk are complex as stated in Bob Hearn’s note.  For credibility, 
the expert contributor should identify him or herself and provide further 
information leading to the unequivocal ranking.
 
John Ahlquist
 
-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Bob Hearn
Sent: Sunday, May 01, 2011 7:55 PM
To: The International Radiation Protection (Health Physics) MailingList
Subject: Re: [ RadSafe ] Ongoing Criticalities Inside Leaking
FukushimaDaiichi Unit 2
 
The I-131 / Cs-137 ratios or absolute concentrations are not adequate to
make any inference regarding criticality or production rate. These
radioisotopes may be released at varying rates with no criticality from fuel
in defected cladding depending on the nature of cladding defects,
temperature, pressure, fuel burn history, etc. We do not even know for sure
how much of the source term for these materials is the spent fuel versus
that in the reactor vessel.
 
These is an entire area of study on radioisotope release from BWR reactor
fuel, dating from the earlier days of GE's A/y-lambda modeling for fuel
warranty validation, and further advanced in more recent decades. These
sparse observations do not provide adequate characterization for any of the
speculation raised in this thread.
 
btw: How is "fresh" I-131 distinguished from any other state of I-131?
 
Bob Hearn
pedigreed expert
 
----- Original Message -----
From: "Randy Parker" <randy at atomicwizard.com>
To: "'The International Radiation Protection (Health Physics) MailingList'"
<radsafe at health.phys.iit.edu>
Sent: Sunday, May 01, 2011 9:17 PM
Subject: Re: [ RadSafe ] Ongoing Criticalities Inside Leaking
FukushimaDaiichi Unit 2
 
 
> Greetings!
>
> Viewing the graphical data for the samples from the six units, I see:
>
> Unit 1 has I-131 in the range of 50 to 500 Bq/cc, decreasing relative to
> Cs-137 by a (very approximate) factor of 20 in 20 days.
>
> Unit 2 has I-131 in the range of 50 to 800 Bq/cc, not decreasing relative
> to
> Cs-137 until 4/22/2011, then decreasing relative to Cs-137 by a (very
> approximate) factor of 5 in 6 days.
>
> Unit 3 has I-131 in the range of 2 to 20 Bq/cc, decreasing relative to
> Cs-137 by a (very approximate) factor of 3 in 12 days until 4/18/2011,
> then
> increasing relative to Cs-137 by a (very approximate) factor of 10 in 8
> days.
>
> Unit 4 has I-131 in the range of 0.06 to 20 Bq/cc, decreasing relative to
> Cs-137 by a (very approximate) factor of 20 in 20 days.
>
> Unit 5 has I-131 in the range of 0.05 to 1.1 Bq/cc, decreasing relative to
> Cs-137 by a factor of 2 (or less) in 20 days.
>
> Unit 6 has I-131 in the range of 0.08 to 0.9 Bq/cc, maintaining a roughly
> constant level relative to Cs-137.
>
> If any of these 6 reactors is presumed to be making new I-131, why not
> pick
> Unit 3?
>
> The only conclusion I can derive from these graphs is "insufficient data".
> The data that I need are those that would give a production RATE of the
> fission isotopes.  These results are for water concentration, but they
> provide no clue about total quantities without some way to measure the
> total
> volume of the water represented by each sample.  Since they are water
> samples, they give no clue as to the amount of I-131 potentially released
> by
> gaseous pathways.  Also, I'm certain there would be other fission products
> present such as I-133 which (with a shorter half-life) would more clearly
> indicate an on-going fission process.  Since I don't know why these are
> not
> plotted, I can draw no conclusion from such information.
>
> If I were to speculate on the information I actually have, I would
> speculate
> that the author of the article prefers speculation...
>
> Not a pedigreed "expert", but my opinion -
> Randy Parker
>
>
>