Talk:Nuclear fallout

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Seven Ten Rule

I have rewritten this section. The previous writeup said a number of things that are not supported by the source document. I found a few online references (e.g. https://emilms.fema.gov/IS3/FEMA_IS/is03/REM0504050.htm) that also make unsupported inferences or factual errors about the data in the source document.

I'm not sure it needs to be mentioned in this section, but the "seven ten rule" is not the same exponential relation that describes decay of individual radionuclides: that relation describes an exponential decrease in radioactivity from a linear increase in time. The "seven ten rule" describes a geometric decrease in radiation dose from a geometric increase in time. — Preceding unsigned comment added by Echawkes (talk • contribs) 23:29, 3 December 2018 (UTC)

Hello Echawkes, the entire Seven-Ten Rule section is fukacta. Yes, the key line is a direct quote from the reference, but the reference is wrong. The updated explanation you found of the Seven-Ten Rule in a more recent FEMA document [1] has an arithmetically correct example. The Kearny book (and the government documents he lifted from) describe the decrease in radiation in chunky terms because it assumes that the reader has only basic math skills. You are correct, radioactive decay is an exponential function. Half-life is a well defined function in the form p(t) = p(0)e^(-rt). The problem is that half-life is defined only for a single isotope. Fallout, such as it is, is a million parts radioactive dirt (mostly light elements) and one part Plutonium nastiness. If I have the time, I will derive the formula, not that we would publish it.

What is more to the point is that three quarters of what is written above is false. I would go so far as to say pseudoscience. In the 1950s we tested ground burst. They might be used against missile silos. They will never be used against industrial or strategic targets. It's a waste of the bomb. Air bursts use the power of the device more efficiently. As long as the fireball doesn't touch the ground, there will not be local fallout. We made air bursts over Japan (2000' altitude). There was no significant fallout. All of the hand wringing is for naught. The bomb proper will blast itself into the stratosphere and spread all over the earth, but we're talking about warheads that weigh 375 lbs.

Take for example the comment about gamma radiation. Yes, it's a photon. Photons from your phone are low energy. They won't hurt you. Gamma radiation is by definition ionizing radiation with energy in excess of 100KeV. From radioactive decay a photon can have an energy as high as 8MeV. That will shit sure hurt you. The alpha and beta particles can be stopped by paper. Rhadow (talk) 01:08, 5 December 2018 (UTC)

If the rule is, "With each seven-fold increase in time since detonation, there is a ten-fold reduction in radiation," then the math is:

${\text{radiation}}_{t}=10^{\log _{10}({\text{radiation}}_{1})-1.183\times \log _{10}({\text{time}})}$

I suspect that the rule of thumb came from an engineer who plotted radiation v time on log-log paper and derived the seven-ten rule.

The result of this formula, in case anyone want to discuss it, is as follows:

- At 1 hour since blast, radiation = 1000 {for example}

- At 7 hours 100

- At 49 hours 10

- At 343 hours 1

- At 2401 hours 0.1

I hope this we never need this knowledge. Rhadow (talk) 17:28, 5 December 2018 (UTC)

Your formulation of the mathematical relationship looks right to me. Thank you for providing it. Although, to nitpick a little, the relationship is between dose rate and time, not between radiation and time.

I don't understand why you claim "what is written above is false... or pseudoscience." There was certainly fallout from the bombings at Hiroshima and Nagasaki - I don't think there is any scientific controversy about that. Your comment about gamma radiation is basically correct, but doesn't contradict the ORNL reference's statement that exposure to gamma rays can be reduced by shielding. You weren't specific about what else you think is wrong. If you think the data or the math is wrong, please state why, and/or cite a reference to support your assertion.

I don't understand why you say that the FEMA web page is more accurate. Most of the content of the FEMA page you linked to looks the same as the ORNL publication cited in the article. I've been assuming that the FEMA page is based on the ORNL publication, but I don't know for sure, since it doesn't cite any references.

Further, I disagree that the FEMA page is more correct. Its statement that "The exposure rate must be expressed in the same unit as the time increase" is nonsense: the relation is exactly the same, regardless of the exposure rate units.

Echawkes (talk) 03:52, 9 December 2018 (UTC)

Hello Echawkes, we are generally in agreement. That's a good thing. On the topic of fallout in Hiroshima and Nagasaki, I found only one article in a quick search. Yes, there was black rain [2]. There is no discussion of local fallout because the air bursts were high enough that the fireball did not touch the ground, a condition necessary to create large amounts of fallout. There is global fallout from high altitude bursts, but it is limited to a small multiples of the mass of the device, not thousand of tons.

My comments about pseudoscience were about the talk, not the article. For example, one editor claimed that gamma radiation was less harmful because it was mass-less photons. Gamma radiation that penetrates lead scares me more than an alpha particle that can be stopped by paper.

You are correct about the units, as long as the units are proportional to one another, as the Roentgen, Gray, and Sievert, and hour, minute, and second are. It is astounding that the government prints this sort of stuff. Rhadow (talk) 17:37, 20 December 2018 (UTC)

Tiger-like structure?

The article states that nuclear fallout "is orange in colour and has a tiger-like structure." Tiger-like structure? What is that supposed to mean? --2601:18A:C500:C00:21BA:160B:F3A0:8DED (talk) 03:31, 9 June 2021 (UTC)

Nuclear fallout is exclusively a product of nuclear weapons

Mess created from Chernobyl is not fallout. It is a special type of radiological contamination.

There is a huge difference between fallout and reactor contamination, both chemically and in sense of radioisotopic content, which in the end produces different effects on biological organisms.

Nuclear reactor accidents have no place in this article and mentioning them seems like pure antinuclear scaremongering. Lajoswinkler (talk) 18:25, 14 February 2024 (UTC)

Move discussion in progress

There is a move discussion in progress on Talk:Fallout (disambiguation) which affects this page. Please participate on that page and not in this talk page section. Thank you. —RMCD bot 21:04, 1 June 2024 (UTC)

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