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Bismuth 214 Fukushima Boundary
Today's reports from TEPCO includes a high radiation alarm which was discovered to have 214Bi (Bismuth 214) int he amount of: 1.2 × 10 ^ - 7 Bq/cm3 which TEPCO claimed to be naturally occurring and evidenced no abnormality in several categories of their report.

I don't know enough about the various radioisotopes to judge their claim but found some interesting physics discussions on 214Bi.

Question: I have a question regarding the measurement of 226Ra by gamma spectroscopy. I've seen that some labs use the 214Bi line, while some use the 214Pb line to measure 226Ra in equilibrium. Are there significant advantages to the use of either line?
Answer: As you know, both 214Bi and 214Pb emit measurable gamma rays, and both can be useful in the indirect determination of 226Ra, a precursor in the decay chain that produces the lead and bismuth progeny. The 214Pb emits lower-energy photons than does the 214Bi, the three most abundant gamma rays from the lead being at 242 keV (7.43 percent), 295 keV (19.3 percent), and 352 keV (37.6 percent). The dominant gamma rays from 214Bi are more in number and higher in energy than the lead gamma rays; the range of useful energies is from about 600 keV to about 2.5 MeV. The bismuth gamma ray of highest yield is at 609 keV (46.1 percent); there is a gamma ray at 1.12 MeV (15.1 percent) and one at 1.765 MeV (15.4 percent). The others have individual yields no higher than about 5 percent.
Source: https://hps.org/publicinformation/ate/q7546.html

Evaluation of decay data of radium-226 and its daughters
just pm me if needed.
I presented this information @Fairewinds with this note: "today's TEPCO report notes Bismuth 214 detected at a Fukushima boundary post - can you explain in a report what that could mean? TEPCO claims no abnormality, but I found some interesting science including decay data of radium 226 and it's daughter products, which you probably know includes 214Bi" and they replied:

"good question and thanks for sharing the report! According to Arnie, Bismuth 214 is a intermediate decay product from U238 with a 19 Minute half life - of course U238 is present inside of nuclear reactors but is also a naturally occurring isotope, and therefor it would be difficult to tell for certain the origin."

My take - far too little information from TEPCO about this event.
just pm me if needed.

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