After some investigation, we can now confirm that the Kauai Monitoring Station in Hawaii broadcast yet another Radiation Alert recently (see graph at right), commencing toward midnight of June 29th and continuing into the early morning hours of June 30th.
This most recent Alert was triggered by a detection of over 100 CPM (Counts per Minute) for a sustained period of almost 15 minutes, followed by lower, yet elevated radiation levels for another half hour, making this the longest detection period yet for the Kauai station (clear sky this time – no rain). Background radiation for that station approximates 37 CPM, so these sustained levels were 2 to 3 times normal. Again, our best judgment is that the source of this radiation is probably Fukushima, perhaps from recent “releases” – we will try to correlate.
This detection by the Kauai station brings up an interesting and related story. A few days before the recent alert, the station operator was remounting the external probe of the Geiger counter under the eaves of the structure, and unwittingly scanned the roof shingles themselves, only to discover an elevated reading at a sustained rate of easily twice normal background. Moving the probe in closer proximity to the shingled roof returned more frequent audible clicking, confirming the shingles were the source.
So the question is, “Why are these roof shingles emitting radiation – is it because of contamination over time by rainfall precipitating it own radioactive particles, or are the shingles themselves ‘hot’?” To answer this, the station operator scanned a pile of surplus shingles in storage that had never been exposed to the rain, and found them to also set off the Geiger counter. So while we do not think of shingles as being radioactive, because they are often “composition”, of stone-based products in part, any one sample can be slightly radioactive. This story serves as a lesson – when scanning captured rainwater for potential radioactive contamination, do not harvest it off any stone-based roofing material lest you get a false signal, or else you will be finding yourself contacting Miami Roofing Contractors in any minute.