Environmental Geiger Counter shielded with lead

In the natural world, there is a small amount of environmental radiation. So, in order to measure the radiation of the sample itself, you need to measure in a radiation shielded environment. To block environmental radiation, you need lead shielding. In high background radiation, you cannot measure radiation lower than the fluctuation of the background. To perform a significant measurement, you have to set up radiation shielding environment, measure background radiation level in it first, and if you are to measure radiation lower than that, you have to prepare radiation source sample for control, and measure, compare, and check repeatedly.
Even with lead shielding, there will be gamma ray from 212Pb, its main peak at 238.6keV, gamma rays penetrate the lead shielding, and characteristic X-ray of lead around 80keV emitted when gamma ray from the sample hits the lead shielding. 80keV characteristic X-ray can be suppressed considerably with cadmium and lead inner shielding, but cadmium being poisonous and difficult to handle, 1mm copper inner shielding in 5cm thick lead block shielding might be common and practical.


Handling lead plate

  • Lead plates are available on the internet shopping, or DIY shops.
  • Be careful not to touch lead plates with bare hand casually, better wrap them with packing tape etc.
  • Keep your sample in plastic bag etc.

Verify Geiger Counter shielding effect of the lead plate

Let's see measurement results with and without lead plate.

First, measure background radiation. Showed 0.053〜 0.054μSv/h measured with HORIBA PA-1000.
鉛なし.JPG

Next, measure with a lead plate wrapped with packing tape under iMetry. Dose dropped to 0.039μSv/h from normal background (approx. 0.054μSv/h).
鉛下置き.jpg

Then, measure with a lead plate wrapped with packing tape on iMetry. Dose also dropped to 0.038μSv/h from normal background (approx. 0.054μSv/h).
鉛上置き.jpg

Try obtaining radiation spectrum of K40 with Yasasho (Low sodium salt)

  • You may need 10 bags (1kg) of Yasashio for quick measurement.
  • You can place iMetry on a lead plate, then Yasashio on the iMetry to block background radiation.
  • If you place an 5mm thickness aluminum plate, effect of beta rays from K40 can be blocked, better for K40 spectrum identification.

  • 最終更新:2013-06-14 14:24:24

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