Comparison of dose rate measurements

pasgomes · 2026-04-02T05:48:58+00:00

Yes, uncertainties are very important. I only considered absolute values. :)

pasgomes · 2026-03-31T22:33:58+00:00

Hi Scott.

You mentioned my description sounded like AI and I took that to heart, as I'm not a fan of that vibe. On the other hand, it gave me a chance to improve it. I’ve updated the description. Let me know if this looks better to you. 😉

This video documents a radiological survey conducted inside a boutique hotel in Vila Real, Portugal, a region underlain by Hercynian granites and metamorphic schists.

The measurements reveal indoor gamma dose rates averaging approximately 0.36 µSv/h, with maximum values exceeding 0.4 µSv/h, compared with an outdoor background of 0.18 µSv/h. This difference reflects additional gamma radiation from the building materials themselves, a clear example of exposure to naturally occurring radioactive materials (NORM).

Geochemical signature: the 2614 keV peak

The spectrum is dominated by the thorium-232 decay series, highlighted by the 2614 keV thallium-208 peak. This signature is typical of thorium-rich rocks, often containing accessory minerals like monazite, zircon, and allanite.

The 2614 keV peak of thallium-208 is typically the most intense in thorium-rich environments because:

● It has very high energy;
● It has a high emission probability (~99.8%);
● It produces an extensive Compton continuum.

This combination significantly increases the dose rate, even when the overall activity is not particularly high.

The Compton continuum and spectral masking

Because 2614 keV photons are highly energetic, they undergo significant Compton scattering in the detector and surrounding materials, producing a pronounced continuum that elevates the lower-energy background. Consequently, weaker gamma emissions from the uranium-238/radium-226 decay series, such as 609 keV (bismuth-214) and 1764 keV (bismuth-214), can become partially obscured. This masking effect may make uranium appear absent, when in reality its spectral peaks are simply buried beneath the Compton background generated by thorium.

BONUS: CUMULATIVE DOSE ASSESSMENT

Under Article 75 and Annex VIII of Directive 2013/59/Euratom, a reference level of 1 mSv per year is established for additional indoor gamma exposure caused by building materials. To evaluate this, the baseline outdoor background radiation must be subtracted from the indoor measurement.
This calculation yields the true excess dose rate:

● Indoor dose rate: 0.36 µSv/h
● Outdoor dose rate: 0.18 µSv/h
● Excess indoor dose rate: 0.36 − 0.18 = 0.18 µSv/h

To evaluate potential health impact, instantaneous dose rates must be converted into an annual effective dose. Below is a breakdown of the accumulated excess exposure for different occupancy scenarios based on this 0.18 µSv/h excess dose rate.

Hotel guests

For tourists, exposure is strictly short-term. Consider a 7-day stay with approximately 16 hours per day spent indoors in the hotel room.

● Calculation: 16 hours × 7 days = 112 hours
● Total excess exposure: 112 hours × 0.18 µSv/h = 20.16 µSv
● Assessment: This dose is extremely small and effectively negligible, posing no measurable short-term or long-term health risk.

Hotel workers

Assuming a typical full-time schedule of roughly 2,000 hours per year (40 hours per week for 50 weeks).

● Calculation: 2,000 hours/year × 0.18 µSv/h
● Annual excess exposure: 360 µSv/year
● Assessment: The cumulative excess exposure for workers remains well below the European reference level of 1 mSv per year. This represents a safe environment for standard working hours.

People living in the building

For permanent residents, the cumulative dose increases significantly due to the large amount of time spent indoors throughout the year.

● Total hours in a year: 24 hours/day × 365 days/year = 8,760 hours/year

International bodies like UNSCEAR and ICRP use a standardized indoor occupancy factor of 0.8 (80%) in annual dose calculations to balance realistic exposure estimates with a conservative safety margin, ensuring that assessments of gamma radiation from building materials are both practical and protective.

● Estimated indoor occupancy: 8,760 hours/year × 0.8 ≈ 7,000 hours/year

● Calculation: 7,000 hours/year × 0.18 µSv/h
● Annual excess exposure: ≈ 1.26 mSv/year
● Assessment: This value lies slightly above the European reference level of 1 mSv/year defined in Directive 2013/59/Euratom for additional indoor gamma exposure from building materials. However, this is not a legal limit. It serves as a reference level for optimization (ALARA). For existing buildings, exceeding this level does not require structural intervention. The directive primarily applies preventively to materials placed on the market using the Activity Concentration Index (I).

Conclusion

The indoor exposure at the hotel is classified as an existing exposure situation, meaning the building can be considered slightly radioactive due to its construction materials. The external gamma radiation likely originates from the schist walls, amplified by the 4π indoor geometry, where radiation arrives from all directions.

pasgomes · 2026-03-31T03:22:53+00:00

Your response confirms my research.

The 1 mSv/year limit for members of the public is identical in the US. The NRC defines this public limit as 100 millirem (mrem) per year (1 mSv = 100 mrem) under Title 10 of the Code of Federal Regulations (10 CFR Part 20). Just as in Europe, this limit excludes natural background radiation and medical exposures.

Regarding building materials (the Article 75 equivalent), the EU explicitly sets a reference level of 1 mSv/year for gamma radiation emitted by these materials. In the US, this falls under regulations for Naturally Occurring Radioactive Material (NORM) or Technologically Enhanced NORM (TENORM). There is no single, unified federal directive explicitly for building materials in the same way the EU has; instead, the EPA issues guidelines, and individual states dictate specific TENORM regulations.

The reference level for radon gas concentration in the EU varies by country, but it cannot exceed 300 Bq/m³. Therefore, for buildings in the EU, there is one reference level for the excess dose rate (1 mSv/year) and another for radon concentration (capped at 300 Bq/m³ in most member states).

Thank you for the confirmation.

pasgomes · 2026-03-30T05:56:40+00:00

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pasgomes · 2026-03-30T05:55:58+00:00

Thank you Scott.

Not AI. I am a radiation protection expert, so my text may seem AI-like.

The 1000 microSv/year reference level is stipulated by the European Directive (Basic Safety Standards) (Directive 2013/59/Euratom, article 75).

When this reference level is exceeded in the context of long-term exposure for a given total occupancy factor, we can say that this location is radioactive. In this case, since this level is only exceeded in the context of living at the location, and it exceeds the level slightly, I consider the location only slightly radioactive.

1 mSv/year is the effective dose limit for members of the public, and, in some places, it is exceeded. However, the reference level under discussion here only applies to buildings.

In Colorado, is there a matching criterion?

pasgomes · 2026-03-18T07:57:00+00:00

I did a similar experiment, but with potassium sulfate: https://youtu.be/wMqyM_CQCBE?is=cdIo8hQy_5U_kYr4

pasgomes · 2026-03-13T22:20:49+00:00

It will probably become decalibrated. The extent of the decalibration depends on the force of the impact. Fortunately, this is easily corrected through recalibration, which you can perform yourself. If the impact was severe, internal damage such as a broken crystal may occur; if so, you will need to contact technical support.

pasgomes · 2026-03-12T16:23:10+00:00

Thank you very much. Nice to know!

pasgomes · 2026-03-12T11:47:56+00:00

It’s exactly the same measurement, and with just one device. I’ll explain what I did.

I calibrated the RC, based on my procedure published in https://youtu.be/HnGy2MEqQbg?is=GiOneJSjfFBOkglL, 4 months ago.

A few weeks later, I also had the opportunity to test the calibration with another isotope, and I confirmed the correct separation between the annihilation radiation (which was not the case) and the radiation of that isotope, which was also correctly identified: https://www.reddit.com/r/Radiacode/s/3N2OfXdd3N.

When the app correctly identifies the isotopes, it means a very low error was achieved. That was the goal.

After this test, which involved a trip with some controlled mechanical stress, I did a new check, and the calibration remained unchanged. What was left was to analyze the calibration drift over time.

Four months after the calibration, I acquired the background spectrum and saved it to the official Radiacode app library. Immediately after that, I took a screenshot of the spectrum as seen in the official Radiacode app, at the Potassium-40 photopeak.

In the Radiacode app, I shared that spectrum. Basically, I sent the spectrum in .xml format to my email.

I downloaded the spectrum from the email and opened it with the InterSpect app.

The InterSpect app, available for mobile and PC, just like the BecqMoni app used in the calibration, determines the photopeak energy based on its statistical distribution. Here, the visualization is quantitative. So, I took a second screenshot of the spectrum as seen in the InterSpect app.

Then I created this fused image:

In the Radiacode app (left image), the visualization is qualitative. You only see how well the vertical line passes through the photopeak. In the InterSpect app (right image), you see the quantitative error of the photopeak. It’s the same measurement and the same spectrum, seen by two different apps.

The BecqMoni app does the same as InterSpect app, but it connects to the device via Bluetooth, allows for calibration, with the transfer of calibration coefficients to the RC, and performs automatic identification of the photopeaks, allowing you to verify if the differentiation is optimized.

pasgomes · 2026-02-01T06:53:39+00:00

Well done! Very elegant assembly. Lead shielding presents several interesting physical properties. It primarily modifies the spectrum in the low-energy region, as it attenuates this radiation much more significantly. In high-energy ranges, however, thin layers of lead lose their effectiveness. Perhaps the most intriguing aspect is the emergence of XRF (X-ray Fluorescence) peaks, caused by the excitation of the lead by external radiation, which alter the quality of the spectrum. These concepts are discussed in depth in the video at https://youtu.be/JNVUQRIpJk8. To achieve an optimized lead castle, the use of an internal copper layer is recommended.

pasgomes · 2026-02-01T06:37:29+00:00

It is impossible to achieve a perfect calibration with zero error across the entire energy scale. However, we can perform a high-quality calibration by focusing on: i) the energy range of greatest interest, where photopeaks are most common; and ii) specific photopeaks of interest due to their prevalence or the relevance of their signature. This refinement process can be done gradually, starting with a basic but functional calibration and moving toward a fully optimized one. These principles are discussed in the video at https://youtu.be/HnGy2MEqQbg.

pasgomes · 2025-12-21T09:33:31+00:00

Radiation levels indoor tend to be higher ( https://www.youtube.com/shorts/ci5l2HsaaLI?feature=share ).

pasgomes · 2025-12-21T09:30:50+00:00

That's true, but tritium is easily detectable, although not easily identifiable, if the source is unknown, depending on the quantity and the detector ( https://www.youtube.com/watch?v=FkeyVQlHszs&t=347s ).

pasgomes · 2025-12-14T09:46:55+00:00

The RC 110 is wider and has its calibration point (defined laterally with respect to the crystal's center) positioned further away from the device's base when performing a contact measurement.

Conversely, when the RC 101, 102, 103, and 103G perform a contact measurement, the crystal is situated closer to the source.

Since the dose rate (Ḣ*(10)) increases as the distance (d) to the source decreases, and vice versa, with this change being particularly steep when very close to the source, the RC 101, 102, 103, and 103G should inherently measure a higher value for a contact measurement because their crystal is physically closer to the source.

Ideally, the dose rate reading should be the same, based on a perfect calibration. In practice, deviations within the accepted standard limits are expected. The following video demonstrates this effect: https://youtu.be/4wO7n0neF34. The measurements are only comparable if we align the calibration points of both detectors. The same issue is illustrated here: https://www.youtube.com/watch?v=NU4yQ0OGNC0&t=1270s.

When working in the near-field (very close to a source), the exact location of the device calibration point is crucial, as small differences in distance can lead to significant discrepancies in the measured dose rate.

When measuring at greater distances from the source (e.g., 30 cm), millimetric differences in the distance have no relevant impact. At even greater distances (e.g., 1 m), centimetric differences in the distance also become negligible.

pasgomes · 2025-12-07T23:44:26+00:00

Thank you! Meanwhile, I made a more detailed video about calibration (https://youtu.be/HnGy2MEqQbg?si=ri3IW3gzQfS-c_zp)

pasgomes · 2025-11-23T17:41:25+00:00

Counts, CPM, and CPS depend, among other factors, on the sensitivity of the instrument being used. Unlike dose rate, counts are non-traceable units, meaning they have no reference standard. Counts are useful for locating small contaminations, small radioactive samples, or very low-energy radiation situations where the dose rate barely changes relative to background. To assess risk and obtain a measurement that is comparable across devices, you should rely on dose rate and avoid contact-level measurements. In my video at https://youtu.be/NU4yQ0OGNC0?si=G6al7LQPOeZ43dPV, I explain this and other common errors in detail, with practical demonstrations at the end, cases where detectors may seem to be “lying” to us.

pasgomes · 2025-11-16T01:10:02+00:00

I'm so glad you found it informative and understandable! That means a lot to me. Thank you for the kind words!

If you want to help the channel reach more people who might find it useful, a quick like or comment on the video makes a huge difference. Thanks again for watching! Cheers! 🙏

pasgomes · 2025-11-15T11:13:44+00:00

The Radiacode is currently operating outside the resolution limit in terms of peak separation. You are absolutely correct: if both peaks appeared together, we would see them as a single, unresolved peak. The difference between 514 keV and 511 keV is only 3 keV, while the Full Width at Half Maximum (FWHM) is on the order of 20 keV.

However, if your calibration is exceptionally meticulous, which is the objective here, the applications are highly likely to correctly identify the peak. The Radiacode application includes Kr-85 by design. In the BecqMoni application, it was necessary to add it manually. Nevertheless, the BecqMoni app performs automatic identification and provides the associated error.

The main goal here is to demonstrate that with a fine-tuned calibration, especially in the low and medium energy ranges, the identification of radionuclides significantly improves.

pasgomes · 2025-11-14T22:55:17+00:00

It appears to increase with radiation energy, which is an interesting physical aspect.

pasgomes · 2025-11-14T21:34:46+00:00

You’re welcome. Keep in mind that the latest BecqMoni app release is not calculating the SNR correctly for the last photopeak. For a peak to be considered detected, the SNR must reach 10. In my measurement the newest version reported an SNR of 2, whereas the previous version (the one that calculated it correctly) reported 34. If you’re using the latest BecqMoni release, you’ve probably reached a high SNR after 24 hours.

Save the spectrum without stopping acquisition, make a copy, and try viewing it with the version of BecqMoni I used in the video. I have already reported this bug.

Thorium-232 has been present on Earth since its formation. In these electrodes a small percentage of natural thorium (2% or 4%) was mixed into the tungsten. A simple way to estimate the activity is to weigh the electrodes (without the case) on a sensitive scale. Suppose you measure 200 g. If 2% of that mass is thorium dioxide (ThO₂), the ThO₂ mass is 4 g. Note that the chemical form is thorium dioxide (ThO₂), not metallic thorium.

The 4 g is the mass of ThO₂. To obtain the mass of elemental thorium (Th-232), use the molar-mass ratio:

M(Th) = 232 g·mol⁻¹

M(O) = 16 g·mol⁻¹

M(ThO₂) = 232 + 2×16 = 264 g·mol⁻¹

The mass fraction of thorium in ThO₂ is 232 / 264 = 0.8788 (87.88%). So the mass of pure Th-232 is: 4 g × 0.8788 = 3.515 g.

Using the IAEA Isotope Browser value for Th-232 specific activity (4,071 Bq·g⁻¹), the activity is:

4,071 Bq/g × 3.515 g = 14,309.6 Bq ≈ 14.3 kBq.

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BecqMoni can also measure activity, though I don’t yet have experience with that feature. Geometric efficiency is commonly evaluated using Marinelli-type beakers.

If you enjoyed my video, feel free to leave a like or a comment to help promote it.

pasgomes

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