Re: [Geology2] 🔴 Elevated Radiation Levels Detected at CA Beach 🔴
On 1/5/2014 2:32 AM, John Rasmussen wrote:
Cesium 137 has a half-life of 30.17 years and decays primarily (95%) with beta radiation. Beta particles are electrons given off by the isotope as it decays. Radioactivity is practically gone after 10 half-lives. In the case of Cesium 137 this would be about 302 years. Beta radiation is easily stopped with a sheet of paper. So very little of this radiation would reach a human body that was wearing clothes. ...
John,
It is not the beta emission from the 95% branching ratio that can be problematic, unless you wear the cesium on your skin or ingest it. That 95% branch produces Ba-137m, with a relatively short life. Thus, a sample of Cs-137, through its decay daughter, emits a 662 keV gamma (85%), plus some soft X-rays from the inner atomic shells. These are both penetrating and potentially harmful in large fluxes.
That being said, Victor's numbers do not suggest either a reason for alarm or the possibility that these signals originated in Japan. There is a subway entrance in New York where the granite bench is above 2 mrem/hr, which is the limit for a 40 hour work week for a radiation worker, which is double the allowance for the general public. That is also about 2,000 times the average background level in most of the country, yet the starfish and subway riders around New York are not suffering a mysterious die off or sprouting extra heads. Neither is there a public health outcry in the decades since this entrance was constructed. Note the alarming videos were reporting levels in the MICROrem/hr range.
The background level here in Kansas is around 10-12 microrem/hr. I can easily find levels of 3-5 times that by wandering near brick or concrete construction.
The valence of Cs makes it soluble, with chemical properties very similar to the other alkali metals, such as sodium and potassium. That means that the Cs they are expecting to reach us in 2014 will be dissolved and highly diluted in the sea water. It will not so much wash ashore as do the washing. I doubt that a Geiger counter or survey meter would be able to detect it. You would need a gamma ray spectrometry system to do that. There is a lot of water in the Pacific ocean.
Ironically, Cs-137 is the most popular source for calibrating commercial survey meters, i.e. converting counts/minute to mrem or microrem.
Chuck
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