Tuesday, March 22, 2011

Massive Xenon 133 plume at our doorstep

Xenon 133 is one of the radioactive noble gases that offers proof of uranium decay.  It has a half-life of 5.2 days.  To become stable, this gas will discharge a beta ray with an energy of about .233 Million electron volts and decay into its stable daughter product cesium 133.  In about 30 days, activity will drop to about 1%.

Now, being able to visually recognize this plume provides only part of the equation in terms of what our exposures will be.  We also need to understand the concentration (in Becquerel) to determine an absorbed dose.

Occupational exposure limits set by the NRC are at 1 x 10-4 μCi/mL of air.  Since i don't have a value in becquerel, it's quite impossible to get an accurate estimation.  Before anyone decides to panic, keep in mind that counts per minute readings along the west coast have stayed within normal background limits, so concentrations of Xenon 133 are likely negligible.

Namie, Fukushima Prefecture [located 20km from Fukushima] is now reading 1600 times normal background.  It rained in that area last night, so that probably has a lot to do with it.  That works out to about 140 rem per year - an absolutely unlivable value, 280 times above the recommended maximum permissible dose for the general population.

Tokyo and Yokohama readings are within normal limits according to today's data.

Update:  Apparently, the above was a theoretical simulation based on an assumed isotope releases and actual values can't be confirmed.  Explanation as follows:


  1. I'm writing from New Mexico USA. My friends and I have been having discussions as to the number of spent fuel rods in storage at the Fukushima Daiichi nuclear plant. We have seen reports of as many as 600,000 and as few as 12,000. Could you give us clarification?

  2. This should help clarify your question -


    60 rods per assembly, so it comes out to about 281,000 total distributed throughout the site?

    The total amount currently residing in the spent fuel pool is open for speculation. If i get reliable info i will be sure to share asap

  3. When you say "counts per minute readings along the west coast have stayed within normal background limits", do you mean the west coast of the Philippines or the USA?
    And which part of the west coast?

  4. U.S. west coast. All sensors in these states have not exceeded 30 cpm as of an hour ago. Nominal. No alarm bells until 130, and if it's a transient reading then no big deal.

    Here's someone streaming readings from vegas -


    Another from west LA -