However, when total yield of individual test devices is considered,
there have been changes of considerable magnitude in the program since
1961.
The changes upward have been dictated by need, and were made as
experience was gained.
The slide shows in a general way the step-up in
maximum yields of underground test devices by fiscal years.
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we moved upward in 1964 to Bilby
with a yield of about 235 kilotons, then on to Halfbeak in 1966 with about
350kilotons, to Greeley in 1967 with about 870 kilotons, and to Boxcar in
1968 with about 1300 kilotons.
The yield figures must be approximations
where any appreciable fusion contribution is concerned, since post-shot
radiochemistry analysis to determine thermonuclear yield is very difficult.
It has been the Commission's policy to step up yields on a careful and
prudent basis so ground motion effects, in particular, can be extrapolated
on a reasonable basis to future events, rather than take a chance of some
unexpected and possibly damaging effect coming along with any radical escalation of yield.
DOE ARCHIVES
Obviously, as yields have increased, depths required for containment
have increased also.
The first underground tests designed for containment
were in mined horizontal shafts.
A little later, some so-called safety ex-
periments were conducted in drilled vertical shafts not designed for containment, but to increase earth capture of radionuclides.
back to 1957 and 1958.
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