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Nuclear Proving Grounds and stick charts

After WW2 the USA needed to develop and test its nuclear technology. It set up two proving grounds.

Nevada Proving Ground

The Nevada Proving Ground was only 65 miles from Las Vegas and gamblers could watch the mushroom clouds from the casinos and hotels. Most of the 928 tests were under ground but 100, including the notorious ‘Dirty Harry;’ test, were atmospheric. and winds  carried the fallout of these  to the west. The town of St. George was particularly badly affected and there were  increases in  leukaemia, lymphoma, thyroid cancer, breast cancer, melanoma, bone cancer, brain tumours, and gastrointestinal tract cancers. Over 200,00 cases of thyroid cancer were believed to have been caused [see this post].  Nuclear Test Participation certificates were issued to the people who took part in testing [see post]

Pacific Proving Ground

Only low yield weapons were tested in Nevada. Most of the big bangs took place in the Pacific Proving Ground [1946-62], on the Enewetok and Bikini Atolls in the Marshall Islands. A few of the later tests were conducted on Christmas Island and Johnston Atoll.


A total of 105 atmospheric and underwater tests were conducted in the Marshall Islands. This was only 14% of the total number of tests but accounted for 80% of the megatonage, The estimated total yield of the Marshall Islands tests was about 210 megatons, including the 15 Mt Castle Bravo shot on Bikini in 1954. The Castle Bravo bomb got out of control and produced over twice the expected yield, spreading radioactive contamination over several of the Marshall Islands atolls and a large area of the Pacific.


An atomic stick chart

The Marshall Islands are known for the stick charts charts their navigators created to help them sail between their 29 atolls and 5 islands. These are spread over a huge area of sea and navigation was a non trivial problem. I have made a stick chart to clarify the geography and identify the atolls that the USA used for military purposes. There is  more about stick charts in a separate post.


The Enewetok and Bikini [the swimsuit was named after the atoll] atolls were the ones used for testing. Kwajalien is still used by the USA as the the Ronald Reagan Ballistic Missile Defense Test Site. Majuro is the capital of the Marshall Islands. To give some idea of scale; it is 539 miles from Bikini to Ebon, the same distance as from London to Leipzig. The circular calculator in the bottom left is a Time Conversion Computer [see this post].

Testing began on Bikini  in 1946 with the Crossroads tests Two 21 kiloton atomic bombs were detonated. ‘Able’ was an atmospheric test [video] and ‘Baker” an underwater test [video]. The Baker bomb was exploded at a depth of 27 meters in the middle of a small fleet of ex WW2 vessels. The dangers of radioactivity were not fully understood then and sailors were sent to try a scrub ‘clean’ the highly contaminated vessels.

Testing then moved to Enewetok Atoll for the Sandstone, Greenhouse and Ivy series of tests. After that testing took place on both Enewetok and Bikini until  Operation Dominic in 1962 which involved 36 bombs being detonated above and near Johnston Atoll and Christmas Island.

Both Enewetok and Bikini remain heavily contaminated. Bikini is now a UNESCO World Heritage site. The natives of the Marshall Islands suffered form American operations in the Pacific Proving Ground, but not as badly as the natives of Utah and the mid west suffered from the operations in the Nevada Proving Ground.

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Nuclear Explosions since 1945

Nuclear Explosions

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October 15, 2015 · 2:18 pm

Nuclear Test Participation Certificates

These certificates were issued to people who participated in US nuclear weapon testing at the Nevada and Pacific test sites.

Operation Ivy Nuclear Test Certificate 1952

Operation Ivy involved two tests. The first, Mike, was the first successful full-scale test of a multi-megaton thermonuclear weapon (“hydrogen bomb”). It was detonated on Elugelab Island yielding 10.4 megatons, almost 500 times the yield of the bomb dropped on Nagasaki. Eight megatons of the yield was from fast fission of the uranium tamper, creating massive amounts of radioactive fallout. The detonation left an underwater crater 6,240 ft (1.9 km) wide and 164 ft (50 m) deep where Elugelab Island had been.

Operation Plumbbob Nuclear Test Certificate 1957

Operation Plumbbob was a series of nuclear tests conducted in 1957, at the Nevada Test Site. It was the biggest, longest, and most controversial test series in the continental United States. It involved 27 explosions, some of which were in the atmosphere or on the surface. Plumbbob released 58,300 kilocuries (2.16 EBq) of radioiodine (I-131) into the atmosphere. This produced total civilian radiation exposures amounting to 120 million person-rads of thyroid tissue exposure (about 32% of all exposure due to continental nuclear tests). Statistically speaking, this level of exposure would be expected to eventually cause between 11,000 and 212,000 excess cases of thyroid cancer, leading to between 1,000 and 20,000 deaths. In addition to civilian exposure, troop exercises conducted near the ground near shot Smoky exposed over three thousand servicemen to relatively high levels of radiation. A survey of these servicemen in 1980 found significantly elevated rates of leukemia: ten cases, instead of the baseline expected four.

You can read more about the health consequences of surface testing at the Nevada site in this post.

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When the USA military ‘dirty bombed’ Americans

Between 1951 and 1992 928  nuclear tests took place at the Nevada Test Site [NTS]. One hundred of these were above ground. The last atmospheric test detonation at the Nevada Test Site was “Little Feller” of Operation Sunbeam, on 17 July 1962.


The NTS is only 65 miles [105 km] from Las Vegas and the mushroom clouds from the above ground detonations were clearly visible from the city. However, above ground tests were only conducted when the wind was from the west and fallout would not affect LV or California.  Cities to the east of the NTS were not so protected. The city of St. George, Utah was the worse affected by fallout from the NTS.

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From the mid-1950s through 1980 the city and southern Utah reported marked increases in cancers, such as leukaemia, lymphoma, thyroid cancer, breast cancer, melanoma, bone cancer, brain tumours, and gastrointestinal tract cancers. The 1953 detonation of the  32 kiloton “Dirty Harry” bomb generated a tremendous amount of fallout.  Winds carried fallout 135 miles (217 km) to St. George, where residents reported “an oddly metallic sort of taste in the air.” ”

Claudia Peterson has a vivid memory from her 1950s childhood in southern Utah. She remembers watching a glowing orange ball move off the western horizon while she rocked back and forth in her swing set the summer she was four, and walking past piles of dead lambs during lambing season. Some had two heads, and others had no legs. Peterson remembers men in tidy, black suits visiting her classroom at East Elementary School in Cedar City with Geiger counters—and feeling a sense of pride that she lit up the counter when they waved it in front of her face. They told her it was from dental x-rays, but she knew she had never had one. She recalls sixth grade when one of her schoolmates died of leukemia, and eighth grade when bone cancer took first her friend’s leg and then his life.”              National Geographic

In a 1997 report  it was determined that ninety atmospheric tests at the NTS had deposited high levels of radioactive iodine-131  across a large portion of the contiguous United States, especially in the years 1952, 1953, 1955, and 1957—doses large enough to produce tens of thousands of cases of thyroid cancer. By 2014  28,880 claims for compensation had been approved for a total compensation of $1.9 billion.

nevada test fallout

Iodine-131 Fallout From the Nevada Test Site ”

Rain, wind, and the food supply spread Iodine 131 from these tests across the United States, with the largest deposits immediately downwind of the test site and the lowest on the West Coast, upwind of the site. Exposure to released iodine occurred mainly during the first two months following a test. After that I 131 disintegrated to harmless levels. Because I 131 accumulates in the thyroid gland, the National Cancer Institute estimates that the fallout may have caused up to 212,000 cases of thyroid cancer in people who were exposed. The average cumulative thyroid dose to approximately 160 million people who lived in the country during testing was about two rads, about five times the radiation dose emitted by a mammogram. A rad is the measurement unit for the amount of radiation the body absorbs. The federal government recommends medical monitoring for people who have been exposed to ten rads or more.

Americans were exposed to varying levels depending on their residence, age, and food consumption. People who lived in Western states to the north and east of the site, such as Colorado, Idaho, Montana, South Dakota, and Utah, had the highest per capita thyroid doses, ranging from 9 to 16 rads. And children between three months to five years old in these high fallout areas probably received three to seven times the average dose for the population in their county because they had smaller thyroids and tended to drink more milk than adults.  Milk was a major exposure vehicle because I 131 fell on pasture grasses and then was consumed by cows. But an estimated 20,000 people who drank goats’ milk during testing were at an even greater risk because it concentrates Iodine 131 more than cows’ milk. Thyroid doses to these individuals could be 10 to 20 times greater than to residents of the same county, who were the same age and gender, and drank an equal amount of cows’ milk. Other pathways included inhaling contaminated air or ingesting tainted leafy vegetables, cottage cheese, and eggs.National Geographic

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