How much radiation exposure in the US was caused by the 105 nuke tests in the Pacific?

Question

Between 1947 and 1962 the US conducted 105 tests of nuclear weapons in the "Pacific Proving Grounds". I'm wondering how much radiation exposure resulted on the west coast of the US. These were part of the 1056 nuclear bombs that the US has ignited over the years (most underground, but two notably in Japanese cities).

So how much radiation exposure in the US was caused by the 105 nuke tests in the Pacific? Should the inhabitants of the West coast have taken iodine pills?

I'd also like to know how much fallout these bombs produced, as compared to the reactor steam releases in Japan, 2011.

Answer 1

There are a lot of works contained in proceedings related to the IAEA, but one very interesting publication is a study of deposition of long lived isotopes as monitored at Tsukuba since 1956. The period of study includes all of the nuclear weapons testing period, and also capturing the Chernobyl accident. The report cited the total deposited activity (in Bq/m^2) for the year, and essentially shows that the deposition at it's highest for Cs-137 is ~2x10^3 Bq/m^2 for the year, in the early 60's (Bq=Becquerel=1 decay/second). After the testing stopped, this amount gradually decreased, spiking high for the year 1986 (Chernobyl), and then decreasing again.

You could make the crude approximation that the activity is uniformly dispersed in the atmosphere due to the prevailing winds causing dilution and mixing, so that sites world wide would note a similar deposition of radionuclides over time.

If one makes a further rough approximation that the Fukushima releases are about a tenth that of the Chernobyl releases, which is a number cited in the news media, one could expect about one tenth of 100 Bq/m^2 for long-lived isotopes, or 10 Bq/m^2 for the year. This may be incorrect, as the values cited for release of Cs-137 are pretty disparate in published reports, with some citing significantly more release of Cs-137 (up to and exceeding the Chernobyl levels). It's probably still a little too soon to tell.

Citation: Hirose, et. al: Analysis of the 50-year records of the atmospheric deposition of long-lived radionuclides in Japan, Applied Radiation and Isotopes, Volume 66, Issue 11, November 2008, Pages 1675-1678

Answer 2

It's difficult to compare becuase of different distance and time scales. But Iodine 131 fallout from Nevada tests caused doses of 10mGray - 200mGray (1-20Rad) across the central and north eastern US, 10mGray is about 8 X-rays or 1 CT-scan.

Generally bomb fallout contains more of the short lived highly active isotopes which are distributed further by the effects of the bomb. Reactor fires generally disperse fallout more slowly and so many isotopes have decayed before they reach the environment