48 @ The Containment of Underground Nuclear Explosions
June 29, 1971, horizontal tunnel test,
Camphor:
Diagonal Line:
Riola:
Agrini:
less than 20 kilotons, radioactivity detected only on-site.
November 24, 1971, vertical shaft test,
less than 20 kilotons, radioactivity detected off-site.
September 25, 1980, vertical shaft test,
less than 20 kilotons, radioactivity de-
tected off-site.
March 31, 1984, vertical shafttest, less
than 20 kilotons, radioactivity detected
only on-site.
Table 3-1—Releases From Underground Tests
(normalized to 12 hours after event*)
All releases 1971-1988:
. Containment Failures:
Camphor, 1971 00. ee cee 360 Ci
Diagonal Line, 1971.................. 00 eee 6,800
Riola, 1980.6... eee eee 3,100
Agni, 1984 0000 eee 690
Late-time Seeps:
Kappeli, 1964.6... 00. eee wea 12
Tierra, 1984 2.0 ees 600
Labquark, 1986 0... eee 20
Bodie, 19869 00. eee eens 52
Controiled Tunnel Purgings:
Hyola Fair, 1974.00.00... eee. 500
These are the only tests (out of more than 200)
where radioactive material has been unintentionally
released to the atmosphere due to containment
failure. In only twoofthe cases was the radioactivity
detected outside the geographic boundary of the
NevadaTest Site.
There have, however, been several other instances
where conditions developed that were not expected.
For example, during the Midas Myth test on
February 15, 1984, an unexpected collapse crater
occurred above the test tunnel causing injuries to
personnel.In addition,the tunnel partially collapsed,
damaging experimental equipment. During the Mighty
Oak test on April 10, 1986, radioactive material
penetrated through two of the three containment
vessels. Experimental equipment worth $32 million
was destroyed and the tunnel system ventilation
required a large controlled release of radioactive
material (table 3-1). In the case of Midas Myth, no
Hybla Gold, 1977... 00. eee 0.005
Miners iron, 1980 ..................-.020-00-. . 0.3
Huron Landing, 1982 ......0..0........0...000. 280
Mini Jade, 1983... eee {
Mili Yard. 1985.00... eee eee . 59
Diamond Beech,1985 .....000 60 ee 1.1
Misty Rain, 1985 ....6..... 0. ee eee 63
Mighty Oak, 1986 .........0..0.0..00.000.0.. 36,000
Mission Ghost, 1987© 0.0.0... ee 3
Operational Releases:
108 tests from 1970-19887... §,500
Total since Baneberry: 54,000 C:
Major pre-1971 releases:
Platte, 1962.00. eee 1,900,000 Ci
Eel, 1962 20. eee 1,900,000
Des Moines, 1962..........0........... 11,000,000
Baneberry,1970..................00.0--. 6,700,000
26 others from 1958-1970 ................ 3,800,000
Total: 25,300,000 C,
Other Releases for Refarance
NTS Atmospheric Testing 1951-1963: .. 12,000,000,000 Ci
1 Kitoton Aboveground Explosion: ......... 10,000,000
Chernobyl (estimata}:..........0....-.00. 81,000,000
4R+12 values apply only to containment failures, others are at time of
release
radioactive material was released (in fact, all radioactive material was contained within vessel 1). In the
case of Mighty Oak, the release of radioactive
material was intentional and controlled. Conse-
°The Camphortailure inctudes 140 Ci from tunnel purging
CBodie and Mission Ghost aiso nad dril-back releases
tainmentfailures by the CEP.
All three of the vertical drill hole tests that
released radioactive material through containment
failure were low yield tests of less than 20 kilotons.
In general, the higher the yield, the less chance there
quently, neither of these tests are considered conVertical Drill Hote Tests
As discussed previously, vertical drill-hole tests
commonly use a stemming plan with six sanded
gypsum plugs or three epoxy plugs. Approximately
50 percent of the vertical drill hole tests show all
radiation being contained below the first plug. In
somecases, radiation abovethe plug may notsignify
plug failure, but rather may indicate that radioactive
material has traveled through the medium around the
plug.
Many of these operational releases are associated with tests that were not
announced
SOURCE. Office of Technology Assessment, 1989
is that a vertical drill hole test will release radioactiv-
ity.27
Horizontal Tunnel Tests
There have been no uncontrolled releases: of
radioactive material detected offsite in the 31 tunnel
tests conducted since 1970. Furthermore, al but one
test, Mighty Oak, have allowed successful recovery
2" Higheryield tests are more likely to produce a contammentcage and result in the formation of a collapse crater. As discussed carlier in this chapter
““why nuclear explosions remain contained,’’ such features contribute to the contaunmentof the explosion.