Few of them know porphyry floor makes it a place with a background radiation well above the world average. This is well known among people who deal with radiation detection so last weekend I decided to go there and check it out.
An above-the-average background is actually quite common in Rome where the dose rate in air averages at about 0.20-0.25 µSv/h.
Just entering the “Roma Termini” underground station the read went up to about 0.30 µSv/h, so that was an encouraging start.
But of course the target was the square in Vatican City.
Actually the dose rate I measured wasn’t as high as in some alley of Orvieto (a notorious high natural background location) but it was still between 0.25 and 0.30 µSv/h across the square and the “colonnato” and slightly higher than that at the end of the square opposite to the Basilica towards Via della Conciliazione.
After surveying the area I needed to find a spot where to record a spectrum for a reasonably long time. I didn’t fancy the idea of spending an hour standing still as in Orvieto so the spot was carefully chosen in order to allow me to sit down relatively comfortably for the entire acquisition time.
Science is a matter of priorities…
90 minutes were required to get close to 900K counts. No surprises from the peaks, U238 and Th232 plus progeny and K40. Average dose rate 0.36 µSv/h.
Here’s the exact position from Google Maps.
https://www.google.com/maps/place/41%C2 ... 12.4578139
So this is how "hot" Saint Peter's Square is, now you know.
Massimo
