Re: Chernobyl

[kmq@cosmail1.ctd.ornl.gov (Kim McMahan)]

At 11:23 AM 9/25/96 -0500, Franz Schoenhoefer wrote:

>Sigurdur said most of all to be said. I want to add only some few words:
>According to some news report only two out of ten neutron surveillance
>instruments within the sarcophargus indicated an enhanced neutron flux.
>According to the same reports no increase in gamma radiation was observed
>neither inside nor outside. No radionuclide release was observed. For me
>this would be a clear indication that no chain reaction could have occurred
>and that it was a malfunction of two instruments. 

And before that, Paul Skierkowski posted a Reuters news release that stated:
>"The main reason is leakage under the sarcophagus of rainwater, which speeds up
>neutrons."


Does anyone have any idea what type of neutron detectors they're using? It
seems perfectly plausible to me that rainwater would moderate whatever
spectrum there is, and the detectors might be more sensitive in the lower
energy range, thereby causing an "increase" in the response. If the two
detectors that showed the increase were located in an area where rainwater
could accumulate, and the other detectors weren't, the pieces fall together.

So, I don't think "detector malfunction" is necessarily the conclusion that
should be drawn. It could just be the same over-response problem many of our
own neutron detectors have when they are calibrated in a high energy neutron
spectrum and used in a lower energy environment.

Neither do I think neutrons "speed up" going through rainwater. I'd hate to
concede that the print media got the story right for once ;-)

Kim McMahan, CHP
Office of Radiation Protection
External Dosimetry Group
Oak Ridge National Laboratory
e-mail: mcmahankl@ornl.gov