Comments on: A University Graduate Student Measures A Few Granite Samples http://solidsurfacealliance.org/blog/2008/08/25/a-university-graduate-student-measures-a-few-granite-samples/ Everything you need to know about the granite/Radon/radiation issues. For more info, go to forum.solidsurfacealliance.org Sun, 09 Jan 2011 21:09:16 +0000 http://wordpress.org/?v=2.8.4 hourly 1 By: Administrator http://solidsurfacealliance.org/blog/2008/08/25/a-university-graduate-student-measures-a-few-granite-samples/comment-page-1/#comment-74 Administrator Fri, 29 Aug 2008 16:43:08 +0000 http://solidsurfacealliance.org/blog/2008/08/25/a-university-graduate-student-measures-a-few-granite-samples/#comment-74 Gary, Thanks for the comments. I am unaware of any uR/hr (micro Roentgen per hour) versus cpm comparisions from Steve. All I read was the cpm readings that he reported. I also didn't see any reference to a Gieger Mueller tube (Geiger Counter) in his response. Could you point out where either or us used a GM tube that might have over responded? I see where I compared our small scintillator reading with his larger scintillator readings, but surely you aren't saying that the scintillators are over responding. From the research I have done, his 2" x 2" scintillation crystal can only be surpassed by a larger crystal or a HPGE type detector. I would say his cpm readings are very accurate unless you can point to a flaw in his methodology. If you have any questions for Steve, ask them and I'll forward them on. Thanks. . Gary,

Thanks for the comments.

I am unaware of any uR/hr (micro Roentgen per hour) versus cpm comparisions from Steve. All I read was the cpm readings that he reported. I also didn’t see any reference to a Gieger Mueller tube (Geiger Counter) in his response.

Could you point out where either or us used a GM tube that might have over responded? I see where I compared our small scintillator reading with his larger scintillator readings, but surely you aren’t saying that the scintillators are over responding.

From the research I have done, his 2″ x 2″ scintillation crystal can only be surpassed by a larger crystal or a HPGE type detector. I would say his cpm readings are very accurate unless you can point to a flaw in his methodology.

If you have any questions for Steve, ask them and I’ll forward them on.

Thanks.

.

]]> By: Gary http://solidsurfacealliance.org/blog/2008/08/25/a-university-graduate-student-measures-a-few-granite-samples/comment-page-1/#comment-72 Gary Fri, 29 Aug 2008 15:35:29 +0000 http://solidsurfacealliance.org/blog/2008/08/25/a-university-graduate-student-measures-a-few-granite-samples/#comment-72 Using a large (2" by 2") sodium iodide (NaI) detector is an effective way to quickly locate areas or items with a higher level of radioactivity. Because the detector medium is a solid, rather that a gas (as in a GM tube), there are a lot more atoms available for a gamma to interact with. Also the volume of the detector is greater. Steve compares results between granite surveyed with the same method, which is valid. However, comparing results in CPM from his SPA-3 or equivalent detector with microRad/hour (uR/hr) from a GM detector is not. His detector will over respond (read high) to low level radiation from radon daughters. An uncompensated GM tube will also over respond. Thus while his method is much more 'sensitive' and can detect small differences better that your GM tube. It is not any more accurate. Using a large (2″ by 2″) sodium iodide (NaI) detector is an effective way to quickly locate areas or items with a higher level of radioactivity. Because the detector medium is a solid, rather that a gas (as in a GM tube), there are a lot more atoms available for a gamma to interact with. Also the volume of the detector is greater. Steve compares results between granite surveyed with the same method, which is valid. However, comparing results in CPM from his SPA-3 or equivalent detector with microRad/hour (uR/hr) from a GM detector is not. His detector will over respond (read high) to low level radiation from radon daughters. An uncompensated GM tube will also over respond. Thus while his method is much more ’sensitive’ and can detect small differences better that your GM tube. It is not any more accurate.

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