Re: Fallout timing

[Jacques.Read@eh.doe.gov]

Somebody mentioned that the early 1960s were the time of maximum fallout.  This
is very true.  President Eisenhower declared a nuclear weapons test moritorium
on October 31, 1958.  The Soviet Union followed suit in November, 1958.
However, in September, 1961, lasting through the Spring of 1962, the Soviets
conducted a series of very large yield tests - each  in the many tens of
megatons TNT fission equivalent.  The US responded with a series of low-yield
underground tests in Yucca Flat --  nine tests in 1961 and sixty-two in 1962.
The Limited Test Ban Treaty, outlawing atmospheric tests was signed on August 5,
1963.  Nixon signed the Threshold Test Ban Treaty on July 3, 1974, which limited
underground tests to under 150 kilotons.

 I was a post-doc helping run a research radiochemical  and nuclear spectroscopy
laboratory on the ninth floor of Chandler Lab, Columbia University, Broadway and
117th Street, in the spring of 1962.  During a rain shower as the cloud from one
of the Soviet tests passed by,  all our counters went mad, and background went
up to several mR/hr.  In later discussions with our opposite members from
Aldermasten, while I was at Livermore, I was told that a British airliner
arriving from the orient on a polar route during this period had to be
decontaminated before they could let the passengers off - its surface was many
R/hr.  As a first approximation, the bulk of the  Pu and fission products in the
world fallout came down out of the hundreds of megatons of fission in the 1961-2
Soviet test series.



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