Monday, September 29, 2014

Krypton-85: Beta Decay in Our Environment



I'm confused. Why would the EPA consider regulating Krypton-85 after trying to raise the allowable radionuclide levels for drinking water?

Silverstein, Ken (2014, June 13) EPA Hits Nuclear Power With Kryptonite. Forbes, http://www.forbes.com/sites/jamesconca/2014/06/13/epa-hits-nuclear-power-with-kryptonite/


The EPA has been encouraging higher levels of radionuclides so something must be especially problematic about Krypton-85 levels or effects.

I searched a bit to see how high atmospheric krypton levels might actually be. I found an interesting study from 1997:
Anthony Turkevich, Lester Winsberg, Howard Flotow, and Richard M. Adams (1997, April 10). The radioactivity of atmospheric krypton in 1949–1950. Proc. Natl. Acad. Sci. USA Vol. 94, pp. 7807–7810, July 1997

ABSTRACT The chemical element krypton, whose principal source is the atmosphere, had a long-lived radioactive content, in the mid-1940s, of less than 5 dpm per liter of krypton.

In the late 1940s, this content had risen to values in the range of 100 dpm per liter. It is now some hundred times higher than the late 1940 values.

This radioactivity is the result of the dissolving of nuclear fuel for military and civilian purposes, and the release thereby of the fission product krypton-85 (half-life 5 10.71 years, fission yield 5 0.2%). The present largest emitter of krypton-85 is the French reprocessing plant at Cap-de-la-Hague.
By 1997, Krypton levels had risen to "some hundred times" what levels had been in the late 1940s!

One has to wonder how much krypton Fukushima dumped into the environment given all noble gas inventory was believed vented from reactor units 1-3. For example, Stohl et al used several methods to compute the xenon levels released in this published study, resulting in very high results:
Andreas Stohl, Petra Seibert, Gerhard Wotawa (2012) The total release of xenon-133 from the Fukushima Dai-ichi nuclear power plant accident. Journal of Environmental Radioactivity 112 (2012) 155e159, http://zardoz.nilu.no/~andreas/publications/222.pdf

The accident at the Fukushima Dai-ichi nuclear power plant (FD-NPP) on 11 March 2011 released large amounts of radioactivity into the atmosphere. We determine the total emission of the noble gas xenon- 133 (133Xe) using global atmospheric concentration measurements. For estimating the emissions, we used three different methods: (i) using a purely observation-based multi-box model, (ii) comparisons of dispersion model results driven with GFS meteorological data with the observation data, and (iii) such comparisons with the dispersion model driven by ECMWF data. From these three methods, we have obtained total 133Xe releases from FD-NPP of (i) 16.7 _ 1.9 EBq, (ii) 14.2 _ 0.8 EBq, and (iii) 19.0 _ 3.4 EBq, respectively.

These values are substantially larger than the entire 133Xe inventory of FD-NPP of about 12.2 EBq derived from calculations of nuclear fuel burn-up. Complete release of the entire 133Xe inventory of FD-NPP and additional release of 133Xe due to the decay of iodine-133 (133I), which can add another 2 EBq to the 133Xe FD-NPP inventory, is required to explain the atmospheric observations. Two of our three methods indicate even higher emissions, but this may not be a robust finding given the differences between our estimates.
Where there is high xenon there will be high krypton. The fuel in Fukushima reactor units 1-3 were purged of noble gasses.

Reading up on Krypton-85 forces one to recognize how incredibly radioactive our atmosphere has become.

What are the consequences of higher Krypton-85 in the atmosphere? Well, its beta decay of 0.687 MeV cannot be good for living organisms that inhale Krypon-85 with their oxygen. For comparison, Tritium's beta decay is 0.018590 MeV (see Wikipedia here)[Tritium is especially bad biologically since it binds with oxygen]

At Enenews, commentator "nuclear pollution" suggested that Krypton-85 build up in the atmosphere could contribute to climate change:

September 29, 2014 at 1:22 pm · Reply
Krypton 85 and CLIMATE CHANGE: “If confirmed this would imply that a changing concentration of krypton-85 could affect to some extent the earth’s climate.”http://www.rivm.nl/bibliotheek/rapporten/500116003.pdf

“One of the radionuclides deserving specific attention is krypton-85, a gaseous fission product (with a half-life of 10.5 years) that is emitted during the reprocessing of spent fuel. It accumulates in the atmosphere. The Kr-85 activity in air showed a regular increase in the last decades (see Figure 2.2, Wingera et al., 2005).” http://www.pbl.nl/sites/default/files/cms/publicaties/500116003.pdf
Krypton-85 decay of beta particles is likely to impact eco-systems in complicated ways. I can only hope we survive our careless engineering.


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