ernal_student said:
Note: the writer modified this later to the equivalent of "the value won't go up significantly".
And even that I modified to "Ups, my statement may have been bogus" - since the official report shows us that there were BIG C137-releases (10% of the whole number) even three weeks after the tsunam.
Regarding the "only airborne releases count":
Let's take a look at the first INES classification (which were also taken as the official release numbers and since then updated): http://www.nisa.meti.go.jp/english/files/en20110412-4.pdf
The first page states
"Nuclear and Industrial Safety Agency (NISA) estimated the total amount of discharged radioactive materials from the reactors of Fukushima Dai-ichi NPS to the air"
Further let's take a look at the INES manual:
http://www-pub.iaea.org/mtcd/publications/pdf/ines-2009_web.pdf
On page 15 it says the following:
Two methods are given for assessing the radiological significance of a
release, depending on the origin of the release and hence the most appropriate
assumptions for assessing the equivalence of releases. If there is an atmospheric
release from a nuclear facility, such as a reactor or fuel cycle facility, Table 2
gives conversion factors for radiological equivalence to
131
I that should be used.
The actual activity of the isotope released should be multiplied by the factor
given in Table 2 and then compared with the values given in the definition of
each level. If several isotopes are released, the equivalent value for each should
be calculated and then summed (see examples 5–7). The derivation of these
factors is explained in Appendix I.
If the release occurs during the transport of radioactive material or from
the use of radiation sources, D2
values should be used. The D values are a level
of activity above which a source is considered to be ‘dangerous’ and has a
significant potential to cause severe deterministic effects if not managed safely
and securely. The D2
value is “the activity of a radionuclide in a source that, if
uncontrolled and dispersed, might result in an emergency that could reasonably
be expected to cause severe deterministic health effects” [5]. Appendix III lists
D2
values for a range of isotopes.
So, where's the problem now? The problem is that NSC, NISA, the government, etc. want everybody to understand the situation. Which includes laymen. You can't give laymen a table of released fission products and expect them to grasp how serious the release now was - since there are isotopes (like Xenon) which have minor impact and others (like Strontium) which are very dangerous.
It would be best to present the public ONE number - the higher the number, the bigger the environmental concern. That's easy to understand, for nearly everybody. For that purpose IAEO invented the I131-conversion. Take the whole release, convert it into one number. That's by no means a measure to cover up big accidents. It's an honest effort in making radiological consequences understandable for the greater public.
But now there's a problem with that iodine conversion. Apparently, the IAEO guys thought that there's only ONE major release path - the aerial release. There's no conversion chart for releases to the sea, only one for airborne releases. And so they only count the airborne numbers...
