Small-Scale Test Proved Radioactivity Can Be Dispersed : Nevada Reactor Blown Up in ‘60s

A little-known, intentional explosion of a small experimental nuclear reactor in Nevada 20 years ago proved that radioactive products like those released by the nuclear accident in the Soviet Union can be carried over nearby areas and dumped on others much farther away, depending on atmospheric forces.

It also demonstrated that fission byproducts from nuclear reactors can be absorbed into the food chain and consumed in such things as milk.

Fallout from the experiment at Jackass Flats, Nev., was found as far away as the Newhall-Fillmore area of Southern California, according to Stewart Black, a radiation biologist who was with the U.S. Public Health Service in Nevada at the time of the experiment.

Airborne Caprice

The capriciousness of atmospheric forces on airborne radioactive particles was demonstrated by the fact that many other areas much closer to the reactor showed no signs of increased radiation, added Black, who is now the chief of the dose assessment branch of the U.S. Environmental Protection Agency’s Environmental Monitoring Systems Laboratory in Las Vegas.

“There are a lot of atmospheric processes that operate on the radioactive particles,” Black said, adding that “a little rain,” for example, is all it takes to carry the particles to the ground.

The Nevada experiment in January, 1965, was part of a program of the old Atomic Energy Commission aimed at developing nuclear rockets for use in space, a goal that was abandoned in the 1970s.

Black said scientists wanted to learn what would happen during a runaway chain reaction in a small reactor.

“What they did was withdraw the control rods as fast as they could,” he said. The control rods are used to absorb neutrons emitted by splitting atoms. When the rods are inserted into the fuel, the reaction declines because some of the neutrons can no longer split other atoms, and when the rods are withdrawn, the reaction increases.

Performed as Expected

The reactor did just what the scientists had expected.

“It exploded” because of rapidly rising pressures that were too great for the reactor to contain, he said.

The amount and type of radioactive byproducts were limited by the fact that the reactor--tiny when compared to today’s giant power plants--had been running for only a few hours. Some of the more troublesome byproducts, such as cesium and strontium, had not been formed in significant quantities because of the briefness of the operation, Black said.

According to a U.S. Public Health Service report, dated Aug. 6, 1965, 74 milk samples were obtained from two ranches in the Amargosa Desert, along the Nevada-California border, 16 miles to the west, and from 14 locations in Southern California.

“None of the 74 samples collected contained detectable quantities of fresh fission products,” the report said, indicating that if any radioactive material reached those areas, it was too widely distributed to be eaten in any concentrated way by grazing cattle.

‘Fresh Fission’

However, the report notes that “natural vegetation samples from Saticoy, Fillmore and Newhall areas” in Southern California “contained fresh fission products.”

Those were the only areas contaminated by the experiment beyond the test grounds where the reactor was located, and the amount was only slightly above normal background radiation, Black said.

In an effort to learn more about how radioactive atoms are taken up by the food chain, the Public Health Service put bales of hay a mile and a half away from the reactor. Later, Black said, “we fed the hay to cows.”

The result was a very slight contamination of the milk.

Safe Level of Picocuries

“The maximum we found was about 500 picocuries per liter of milk,” Black said. He added that the maximum permissible limit for milk is 70,000 picocuries. (A curie is a measurement of the rate of radioactive decay, and a picocurie is one-trillionth of a curie.)

The level of contamination would have been much greater for a large reactor like the one in Chernobyl in the Soviet Union, especially if the reactor had operated for a long period of time.

For the most part, the limited amount of radiation released by the explosion 20 years ago jumped over the area to the west of the reactor, and some of it landed in Southern California.

But why Newhall?

Black speculated that the radioactive cloud traveled through the lower atmosphere and landed in the Newhall-Fillmore area because it simply hit the hills.