The Most Radioactive Room in My House

[Go-Figure]

Hi Folks,
I have a few samples on the way, but none of them made it for the weekend, so I decided to do something different.
I had problems with attachments the first time I tried to post this, hopefully this time around will be better!

Right beside the room when I usually do my tests there's a bathroom. Bathrooms are often the most radioactive rooms of the house, and this one is the most radioactive of them as far as my house is concerned. I knew that since my first tests with the Geiger counter, but I wanted to have more quantitative data on the matter.
What makes the room more radioactive than those around are ceramic tiles covering the floor and part of the walls.
I first recorded a 14 hours background, taking a 30 minutes count with my Geiger at the same time.

Here's the read of the Geiger. The average is 59.33 CPM.

This is the background spectrum. All expected peaks from U238 and Th232 decay chain, plus K40 are there.

Background Bathroom - 14 Hours - Counts x Bin - No Shield - 0.045 Clean - 03-08-19.png (6.46 KiB) Viewed 156 times

You can compare it with the spectrum of the room right next to it where I usually do my tests (below). Peaks are the same, but the one above is definitely more bumpy.

Background Stanza Fondo - 12 Hours - Counts x Bin - No Shield - 0.045 Clean - 27-07-19.png (5.79 KiB) Viewed 156 times

Then I placed the scintillator at contact with the tiles and took another 20 hours spectrum. I was a bit worried the detector could fall from where I put it (see Steven? I am taking good care of it) and I certainly couldn't stay there the whole time, so I made sure it couldn't move much...

And the results 20 hours later is showed below both in counts per bin and energy per bin. Again, all expected peaks from U238 and Th232 decay chain, plus K40 are there. So many in fact it was hard to label them all without making the presentation look too crowded (click to enlarge).

The quantitative analysis reveals the level of exposure inside the bathroom is 20-25% higher than in the next room. The result I get from the Geiger counter read + correction (based on average energy per count of my background spectrum vs the average energy per count of Cs137, which is what the Geiger is calibrated for) gives a pretty similar results: 0.125 µSv/h vs 0.132 µSv/h.
Assuming a weighting factor equal to 1 the Gy can be converted in Sv with a ratio 1:1.

The close proximity to the tiles added very little to the energy of the spectrum compared with what I got in the middle of the room, a difference of just 1 CPS and 0.007 µGy/h.

I also tested the tiles at contact with the Mirion PDS100G, over a 7992 seconds measure the result was 0.119 µSv/h vs 0.138 µSv/h from the GS spectrum. A 15% difference, not too bad.

The spectrum from the PDS is in logarithmic view (no background subtraction here).

As a bonus, I also conducted a Radon test in that bathroom over the last couple of weeks with a weekly average of 127 Bq/m^3, while the daily average went from a maximum of 235 Bq/m^3 to a minimum of 50 Bq/m^3 when the windows was open (I couldn't ask people not to use that particular bathroom for two entire weeks!), a reminder of how ventilation plays a role in Radon concentration inside a room. In the next room the read never gets higher than 60 Bq/m^3.

So that's it for the most radioactive room of my house, nothing dangerous but a measurable difference compared with the other rooms at the same floor.
Now you know all there's to know about my bathroom. Well, as far as radiation is concerned...

Massimo

[Svilen]

Nice job done again! And some equipment that made me a little jealous :)

[Go-Figure]

Nice job done again! And some equipment that made me a little jealous :)

I made that bathroom completely inaccessible for almost 48 hours, but in the end the fun was worth it. Well, for me at least, other people in the house might disagree with it...

[elemental]

I have read with interest this post from Go-Figure, so decided to run a preliminary experiment
of my own.

The results are shown below, and the next step is to enhance the lower energy levels.

As a background, our house was built in the 1980's above the Willunga Slate quarry in
South Australia.

The bathroom/toilet forms part of the old building which has a Willunga slate floor.

The outside walls have been hand made with hollow cement blocks covered by seashells and
rock pieces. The internal lower metre of the external wall has been reinforced with concrete.

The internal walls are covered floor to ceiling with modern wall tiles.

As can be seen the results are very similar to those obtained by Go-Figure, so I will
soon be undertaking some more sampling.

[Go-Figure]

Hi there!
Good to know something I did here produced consequences in South Australia! :)
Yeah, results looks similar, your calibration seems to be going a bit off above 1000 keV, maybe you can try a calibration with a Th232 source or with the bathroom itself, the peaks from K40 at 1460 and Tl208 at 2614 are clearly spottable.
You can call me Massimo by the way!

[elemental]

Hi Massimo

I know my calibration was a bit off, I used only a quick Cs
Source. I plan to run it again in the next few days but do a better calibration with either a thorium mantle or a radium card.

Thanks for your comments, much appreciated,

Cheers and regards
Gary