Posted: January 4, 2014 by: Dan

A lot of concern has been expressed about recent reports and videos showing high levels of radiation on a beach in Half Moon Bay, just South of Pillar Point Harbor. It has been attributed to Fukushima. Local officials have been quoted as saying they donʻt know what it is, but donʻt worry about it. See local story.

Here is what we have learned so far: The radioactive areas of the beach seem to be associated with dark sand below the high tide level. The levels detected are about 5 to 10 times what you would normally expect to find on a beach.

The radionuclides are in the NORM class of radioactive substances, not from Fukushima. NORM stands for Naturally Occurring Radioactive Material. We put a sample in a Multichannel Analyzer and found Radium 226 and Thorium 232. See the measured spectra below.

If the sand were contaminated by radiation from Fukushima it would show Cesium 137. See spectra below from contaminated area of Fukushima Prefecture. The same instrument is identifying Cesium 137 rather than Radium and Thorium.

The picture below is a geiger counter measuring the activity in a sample bag of the sand. The radiation level is elevated, but roughly equivalent to some granite counter top material from Brazil.

Whether this material is naturally occurring at this beach or not remains a question. There are also reports that a pipeline was once at this location. We hope the State will do further testing to determine the origin and full nature of the hot spots on the beach. But we are confident that it is not related to Fukushima, based on the spectral signature. We expect more news later today.

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