36 © The Containment of Underground Nuclear Explosions
Photo creat Swoas met wry
Blanca containmentfailure, 1988.
kilotons. The first few tests after Rainier. however,
were detonated at greater depths than this formula
requires because it was more convenient to mine
tunnels deeper in the Mesa. It was not until
““Blanca,’’ October 30, 1958, that a test was
conducted exactly at 300 (yield)feet to test the
depth scale. The containment of the Blanca explosion, however, was unsuccessful and resulted in a
surface venting of radioactive material. As a consequence, the depth scale was modified to include the
addition of a few hundred feet as a safety factor and
thus became: 300 (yield)? *‘plus-a-tew hundredfeet."
Today, the general depth of burial can be anpros
mated by the equation:
Depth = 400 (yield) ©.
where depth is measured in feet and vicid in
kilotons.'* The minimum depth of burial. however,
is 600 feet.'5 Consequently, depths of bunal van
from 600 feet for a low-yield device, to about 2.100
feet for a large-yield test. The depth is scaled to the
'2**Public Safety for Nuclear Weapons Tests,"’ United States Environmental Protection Agency, January, 1984.
3The 600-foot depth was chosen as a minimum after a statistical study showed that the likelihood of a seep of radioactive maternal ly the surtse cor
explostons buned 600 feet or more was about 1/2 as great as for explosions at less than 500 feet. even if they were buried at the same wane depen in
each case.