Thursday, 25 August 2016

Nuclear power plants cause climate change by emitting Krypton-85, not

"Nuclear news"

Is not a nuclear news site. It's a site full of junk written by keen antinuclear power activist Christina MacPherson / Noel Wanchope (They are the same person). Any lie or fabrication about nuclear power is repeated by nuclear news and sent out to her followers. The criteria for publication here is antinuclear good, pronuclear ignored. To some people nuclear news is a nutty site. To others it's a hero site. It's remarkable how similar it is in choice of story to mainstream newspapers like The Guardian: pronuclear all but banned, almost any antinuclear story published.

Let's look at one claim Christina makes on her site, for example the myth that

krypton-85 is responsible for climate change
Google gives 97 hits for this meme on Christina MacPherson's website:

Krypton-85 is a very rare radioactive gas found in earth's atmosphere and mostly originating from nuclear power. In particular it leaks out when spent fuel is reprocessed. Krypton is an inert gas, and does not react chemically with other atoms. It occurs in mono-molecular form, AKA: single atoms. Because it has made no bonds there is no polarization to speak of in the molecule and it has no radiative forcing effect.

The basis of this anti-nuke claim (Krypton-85 made by nuclear power causes climate change) originated decades ago from a speculative academic paper. The researchers said that if a lot more krypton-85 was made (tens, hundreds of times as much?), then it might have an effect. Krypton-85 decays with a ½-life = 10¾ years. When it decays it produces a positively charged ion and a negatively charged electron (beta-ray). The anti-nuke theory goes this atmospheric ionization causes climate change. Let's look at the numbers.

  1. There's a small amount of Kr-85. In 2009, the total amount of Kr-85 in the atmosphere was estimated at 5500 PBq due to human sources. This is 0.38 tonnes of Kr-85 in 5,140 trillion tonnes of air (making up all earth's atmosphere). 0.000000000074 ppm, or 0.000074 ppt (parts per trillion).
  2. The atmosphere is positively charged (overall). Earth has an overall negative charge. This is why lightning happens.
  3. An average bolt of lightning carries a negative electric current of 40 kiloamperes (kA) (although some bolts can be up to 120 kA), and transfers a charge of five coulombs and energy of 500 MJ, or enough energy to power a 100-watt lightbulb for just under two months. There are estimated to be around 2,000 lightning storms active around the globe at one time creating over 100 strikes per second. i.e. 500 coulombs discharged per second on earth.
  4. 5500 Pbq means, each second 5.5 × 1018 positive ions are made by Kr-85, and the same number of electrons. This is the number of Kr-85 decays happening. About 5.5 ÷ 6.241 coulomb. = 0.88 coulomb. This assumes all the negative ions are lost. Negative charge is not lost. All beta-rays are captured in the atmosphere. So there is no net charge contribution to the atmosphere from krypton-85. A beta ray (electron) can travel about 2 metres in air before it collides with an air molecule.
  5. Krypton-85 makes about 0.88 coulomb of positive and negative charge (per second). Each second, about 500 coulombs of charge in the atmosphere is neutralized by lightning.
  6. There has to be far more Kr-85 in the atmosphere for it to affect climate in any measurable way. Even then climate scientists dispute the effect of ionization, which is said to cause cloud formation, which either cools or warms depending on whether these are in the upper or lower atmosphere.
  7. I almost forgot. Significant buildup of Kr-85 will not happen because doubling the amount emitted (mostly by nuclear fuel reprocessing plants) will not double the amount in the atmosphere. This is because of its 10¾ year ½-life.

Alert observers may notice I already covered this once. I was completely baffled when I discovered this antinuclear power meme. It holds a kind of ghoulish fascination for me. As in: just how daft can hard-core anti-nukes get?


RationalWiki: Krypton-85 and climate change

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