Underground blasts were also culprits

Fallout researchers have focused their attention on above-ground nuclear testing at the Nevada Test Site from the 1950s through the early '60s. However, a 1996 report says hundreds of underground tests also spewed radiation.

Besides the danger to workers at the NTS, more than 50 of the tests released enough radioactive material that some made its way off the sprawling test site.

The report is "Radiological Effluents Released From U.S. Continental Tests 1961 through 1992," produced by the U.S. Department of Energy in August 1996 and available at a DOE Web site, www.nv.doe.gov.

U.S. above-ground testing ended in 1962. However, since 1961, radioactive material escaped from 433 tests, "some of which have simultaneous detonations" where several explosions would go off at once, the report says.

"However, only 52 of these are designated as having offsite releases," according to the report.

The "Palanquin" test of April 14, 1965, blew radiation out of a crater, and 23,000 picocuries of gross beta activity per cubic meter of air was detected offsite at the populated community of Clark Station, Nev., the report says. At Highway 6, an uninhabited location offsite, eight miles east of the Tonapah Test Range Road, the reading was 87,000 picocuries per cubit meter of air.

Stone Cabin Ranch, Nev., also off the Nevada Test Site, had the greatest gamma radiation exposure, at 3 milliroentgens per hour. The report adds that the highest radioactive iodine concentration in milk was "11,000 picocuries per liter at Martin Ranch near Eureka, Nev.; no children present."

Fallout at 0.03 milliroentgens per hour was detected as far as Council, Idaho, about 500 miles away.

In the Baneberry test of Dec. 18, 1970, "gross fission products" blew out of the underground test and were detected off the Nevada Test Site.

Part of the fallout cloud drifted over Nevada, Utah and Wyoming, while "another fraction (of the cloud) moved toward California."

Maximum radioactivity detected offsite was 3,400 picocuries of Iodine-133 per cubic meter of air at Stone Cabin Ranch, Nev. Maximum iodine level detected offsite was 810 picocuries of radioactive I-131 per liter of milk at the McCurdy Ranch near Beatty, Nev., it says.

"Venting occurred from a fissure near surface ground zero" 3 1/2 minutes after the blast, says the report. "The effluent venting rate steadily decreased with time, but visible vapor continued to emanate from the fissure for 24 hours after the detonation."

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