48 © The Containment of Underground Nuclear Explosions
Camphor:
June 29, 1971, horizontal tunneltest,
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,
fess than 20 kilotons, radioactivity detected off-site.
March 31, 1984, vertical shaft test, 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, 19719 0... ee 360 Ci
Diagonal Line, 1971...........0.00.0.....00., 6,800
Riola, 1980.6... ee 3,100
Agni, 1984.00 690
Late-time Seeps:
Kappeli, 1984. 00. eee 12
Tierra, 1984 20 eee 600
Labquark, 1986 0.0... eee 20
Bodie, 19869 26... cece eee 52
Controlled Tunnel Purgings:
Hybla Fair, 1974.00. 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 two of the cases was the radioactivity
detected outside the geographic boundary of the
NevadaTestSite.
Hybla Goid, 1977... eee. 0.005
Miners Iron, 1980 ..............0.... 0... .000200.. 0.3
Huron Landing, 1982 ..................... . .. 280
Mini Jade, 1983.0... eee {
Milf Yard, 1985 2.00... 5.9
Diamond Beech,1985 .......................2.0... 1.4
Misty Rain, 1985 .............0..0..00..00-- 00, 63
Mighty Oak, 1986.......................0000- 36,000
Mission Ghost, 1987° ..............0......0.00..000. 3
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
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-
Operational 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 higherthe yield, the less chance there
is that a vertical drill hole test will release radioactivity.27
quently, neither of these tests are considered conVertical Drill Hole Tests
As discussed previously, vertical drill-hole tests
commonly use a stemming plan with six sanded
gypsum plugsor three epoxy plugs. Approximately
50 percent of the vertical drill hole tests show all
radiation being contained below thefirst plug. In
some cases, radiation above the plug maynot signify
plug failure, but rather may indicate that radioactive
material has traveled through the medium aroundthe
plug.
108 tests from 1970-19887 ............... 00.0005. 5,500
Total since Baneberry: 54.000 Ci
Major pre-1971 releases:
Platte, 1962 00. eee 1,900,000 Ci
Eel, 1962 ....... eee 1,900,000
Des Moines, 1962...................... 11,000,000
Baneberry, 1970 .....................00.. 6,700,000
26 others from 1958-1970 ....... ........ 3,800,000
Total: 25,300,000 Ci
Other Releases for Reference
NTS Atmospheric Testing 1951-1963: .. 12,000,000,000 Ci
1 Kiloton Aboveground Expiosion:......... 10,000,000
Chernobyl (estimate):.........0...00...-. 81,000,000
4R+12 values apply only to containment failures, others are at time of
release.
oThe Camphor failure includes 140 Ci from tunnel purging
CBodie and Mission Ghost aiso had dnill-back releases
dManyof these operational releases are associated with tests that were not
announced.
SOURCE. Office of Technology Assessment, 1989
Horizontal Tunnel Tests
There have been no uncontrolled releases of
radioactive material detected offsite in the 31 tunnel
tests conducted since 1970. Furthermore, all but one
test, Mighty Oak, have allowed successful recovery
27 Higheryield tests are more likely to produce a containment cage and result in the formation ofa collapse crater. As discussed earlier in this chapter
‘twhy nuclear explosions remain contained,’’ such features contribute to the containmentof the explosion.