Can you place it 2cm above a banana so we can see the negative control?
Can you place a lead sheet between the detector and the watch for additional verification?
To give you some context, here's Table 4 from GK Gillmore et al. (2012) from Environment International; 45: 91-81. He's the same professor from Kingston University who published the report that caused a resurgence in anxiety around radium watches in 2018 (see links below). As you can see, for wristwatches, measurements 2 cm above crystal usually range 0.5-20 uSv/hour range, with 20 uSv/hour being really atypical and high (it was a military watch from the 1940s).
The articles posted below I believe are mainly sensationalist. The conclusion from the study is that the radiation levels are acceptable, particularly from later watches post-1950s and non-military watches. Pocket watches are larger and so more radium = higher risk. They concluded the emitted radon levels were the greater concern.
https://www.hodinkee.com/articles/new-report-shows-radium-dials-might-pose-serious-danger
https://www.northampton.ac.uk/news/wwii-military-watches-potentially-pose-serious-cancer-risk/
https://wornandwound.com/new-study-warns-against-radium-dialed-watches/
To be clear though....135 uSv/hour is extremely high. That's > 1000 mSV annual exposure at the wrist. You'd likely get a substantial total body dose from that as well...If that reading is true, I'd suggest getting rid of the watch.
But I doubt that's an accurate reading.
Steel (at a greater thickness than lead) will do the trick too! 馃槈
From US Dep't Commerce Nat'l Bureau of Standards
Steel (at a greater thickness than lead) will do the trick too! 馃槈
From US Dep't Commerce Nat'l Bureau of Standards
Commercial radiation detectors use a sodium iodide detector that only detects gamma or x-ray particles. It won't detect alpha radiation, and tritium emits 100% alpha emissions. Radium is ~96% alpha with 4% gamma. The gamma is what we worry about and that's what your probably measuring with your detector.
Just to be clear, as far as you know: top- quality Geiger counters measure just gamma...or gamma and alpha? And, if a device only measures gamma, that's not an accuracy liability for measuring radium watches?
Just to be clear, as far as you know: top- quality Geiger counters measure just gamma...or gamma and alpha? And, if a device only measures gamma, that's not an accuracy liability for measuring radium watches?
Most commerical detectors (e.g. Radex) only detect gamma. You need specialised devices to measure alpha, and usually the devices that measure alpha only measure alpha, not gamma and alpha. Reason being that we generally "don't care" about alpha radiation, given it only penetrates a few millimetres away from the source. The large alpha particles are block by air, the watch case, and skin. It is believed to largely be biologically harmless (as long as you don't ingest an alpha emitter).
Generally if you have a radium watch, you only care about the gamma emissions. That's why tritium started being used in the 70s. Tritium emits 100% alpha, so it's considered much safer (and its half-life is 12 years, so this also contributes to the "safety").
Most commerical detectors (e.g. Radex) only detect gamma. You need specialised devices to measure alpha, and usually the devices that measure alpha only measure alpha, not gamma and alpha. Reason being that we generally "don't care" about alpha radiation, given it only penetrates a few millimetres away from the source. The large alpha particles are block by air, the watch case, and skin. It is believed to largely be biologically harmless (as long as you don't ingest an alpha emitter).
Generally if you have a radium watch, you only care about the gamma emissions. That's why tritium started being used in the 70s. Tritium emits 100% alpha, so it's considered much safer (and its half-life is 12 years, so this also contributes to the "safety").
