meltdown math

Does it help to say "the radiation was 1000 times normal" without saying where and for how long, or how it compares to everyday differences e.g. in visiting the mountains, taking a plane ride, or getting an X-ray?

radiation sources

In that context it might be useful to list here some numbers for various kinds of everyday exposure to ionizing radiation in terms of both exposure rate and of total dose, where one equivalent Joule (J) of absorbed energy per kilogram (kg) of target mass is also known as 1 Sievert (Sv) or 100 Röntgen equivalents for man (rem). We might start with total doses of different types of radiation for various events.

Table 1: Various ionizing radiation doses

Activity	Absorbed dose [μJ/kg]	Equivalent Dose [μSv]	Equivalent Dose [rem]
dental X-ray	10	10	0.001
foot/arm X-ray	10	10	0.001
cosmic rays for year		270	0.027
earth bkgd. for year		280	0.028
mammogram	3,000	3,000	0.3
airline crew for year		9,000	0.9
GI X-ray series	14,000	14,000	1.4
nuclear worker for year		20,000	2
poisoning effects		1,000,000	100

radioactive transport

This might be good place for notes on the expected reduction with distance of radiative dose, and of air-borne and water-borne contamination as well. They might help answer questions about how much you should worry about stuff happening down the road, and/or on the other side of the planet.
For instance, radiation from a localized specimen will fall off as one over distance squared (or faster if there are absorbers in the way). Thus if the dose rate is one rem/hour at 1 meter away, at 10 meters away it will be 0.01 rem/hour or less. That means that if the source of radioactivity stays put, distance between you and it will have a very powerful effect.

On the other hand, lateral transport of radioactive materials away from a point e.g. on the earth's surface may at best result in concentrations that fall off as one over distance. If the flow is not radially outward but unidirectional, the fall-off will be greater for those out of the flow path but less for those in that path. Thus if the outflow of radioactive stuff gives a 1% concentration a kilometer away from the source, the average concentration 10 kilometers away should be only down to 0.1%.

effects of radiation

Similarly the risks of ill-affect associated with the various types of exposure might be of interest to folks who want to decide for themselves what is useful information and what is not. Short of the somatic damage caused by very large (e.g. ≈ 1 equivalent J/kg) doses of radiation, radiation might e.g. increase one's chance to get cancer but by how much?

Estimates e.g. for the effect of 1-rem computer tomography (CT) scans might be something like 4 cases of cancer (developing after a decade or more) for every 10,000 scans. Thus the odds of getting cancer from a CT scan may be less than the odds of throwing 11 coins at once and finding that all of them have landed heads up, i.e. less than 1 in 2¹¹ = 2048 times. If you need the scan, that chance may be one you can afford to take but regardless it should probably be your call.