trinity

aigardening / stusontier 07/2025

Einstein’s famous 1905 equation revealed to all physicists that huge amounts of energy are bound up in the atomic nucleus.

In 1933 Leo Szilard realised that a nuclear chain reaction would work if  a ‘fissile’ material could be found where one neutron could split a  nucleus, releasing energy and more neutrons.

To make a bomb millions of times more powerful than conventional explosives...

....all the scientists needed to do was isolate enough fissile material, and assemble it together into a critical mass quickly enough before it blew itself apart again.

— Crystal Lambert

Pu-239

Plutonium (Pu) was used in the first nuclear bomb, a man-made element  with 94 protons. The "239" isotope with 145 neutrons was found to  fission with fast neutrons - ideal for nuclear weapons. Three nuclear  reactors were built at Hanford to irradiate uranium 238 with neutrons -  via nuclear alchemy of neutron capture and electron emission the uranium  was transmuted to neptunium and then plutonium. 6 kg of weapons grade  metal was chemically separated from over 24 tonnes of uranium .

72% of the uranium for the Manhattan project came from the Belgian Congo, where the US government purchased about 6,000 tonnes of ore through British intermediaries, with most of the remainder coming from Canada.

In order for scientists to be able to calculate the optimum air-burst altitude for the Hiroshima and Nagasaki attacks to inflict maximum damage and casualties, the Trinity bomb was exploded at the top of a 30 m tall tower.

The Trinity test explosion in New Mexico converted only about 1 kg of this Pu-239 to energy - the remaining 5 kg of unfissioned plutonium were vaporised in the debris cloud.

This configuration close to the ground meant that more than 5000 tons of desert soil was blasted into the air as dust mixed with volatile radioactive fission products and the more refractory unfissiled plutonium.

— Crystal Lambert

In the instants after the detonation, the desert sand was swept up into the fireball where it melted.

Tiny droplets aggregated into bigger droplets that became too heavy to remain suspended and fell as a rain of molten glass.

The 100 m wide crater immediately after the blast was a

"lake of green jade [ ] the glass takes strange shapes - lopsided marbles, knobbly sheets a quarter-inch thick, broken, thin-walled bubbles, green, wormlike forms."

Both green and red Trinity glass (trinitite) were found in abundance at the site, with small amounts of black glass - spectroscopic analysis suggested that green trinitite contained material from the bomb's support structure, while red trinitite contained material originating from copper electrical wiring.

The glass was (and is) still mildly radioactive, from Cs-137, Am-241, Ba-133, Co-60, Eu-152, Eu-154 and Eu-155

Now illegal to remove from the site, most of the trinitite was bulldozed and buried by the United States Atomic Energy Commission in 1953, when the site was "cleaned".

Most of the material was lifted into the atmosphere and deposited within about 400 km downwind of the test site, contaminating wide areas of soil to the south of Santa Rosa.

6kg

The fallout was tracked across America as far as the Atlantic Ocean, although the public was not told

“We were grabbing the white flakes, and putting it all over ourselves, pressing it on our faces”

“We were grabbing the white flakes, and putting it all over ourselves, pressing it on our faces”

Young teenager Barbara Kent said that several hours after the atomic bomb went off on July 16, 1945, she and some friends in Ruidoso, New Mexico - a part of Lincoln County - noticed white flakes drifting down from a big cloud in the sky.

"The strange thing, instead of being cold like snow, it was hot. And we all thought, ‘Well, the reason it’s hot is because it’s summer.’ We were only thirteen; we didn’t know any better.”

Following the detonation, a radioactive contaminant was encountered in paper strawboard material used by the Eastman Kodak Company for packaging photographic sensitive films.

This paper board was manufactured in a mill situated at Vincennes, Indiana, on the Wabash River, about 2,000 km to the east. A run of strawboard, produced on August 6, 1945, showed this new and unusual type of radioactive contaminant. X-ray film packed with this board developed fogged spots after about two weeks' exposure. 

Measurements of the contaminated spots of strawboard showed no alpha-activity but fairly strong beta-activity, ruling out naturally radioactive materials.

Radiochemical studies indicated that the material was the rare-earth isotope Ce-141

... pointing to the conclusion that the radioactive contaminant was an artificially radioactive material which found its way into the mill through the river water. 

The accepted explanation is

derived from the Trinity bomb detonation in New Mexico three weeks earlier

that it was a wind-borne fission product

that it was a wind-borne fission product

In addition to the unfissioned material, the fallout contained large quantities of fission products, including

strontium-90 cesium-137 iodine-131

strontium-90 cesium-137 iodine-131

with half lives of 29 years, 30 years and 8 days respectively

The cesium-137 activation was still easily measurable in a survey made in 1992 by EG&G for the DOE to map the fallout plume.

63 radionuclides in total have been studied for dose estimates, including highly biologically active ones

63 radionuclides in total have been studied for dose estimates, including highly biologically active ones

Pu-239 is radioactive with a half-life of about 24,000 years

about 1 kg of this highly active plutonium isotope will still remain in the upper layers of the New Mexico desert soil in 100,000 years time

Although the Manhattan scientists took precautions to avoid radiation exposure to themselves, there were no precautions nor contemporary (or subsequent) studies about civilian exposure, with the authorities concerned about alarming the public.

In New Mexico, radiation-containing dust landed on vegetables and cattle and contaminated the drinking water supply of rainwater collected from roofs  in large cisterns or holding tanks.

Most locals also grew most of their own food and raised livestock for meat. The densest part of the fallout pattern followed a northeast track, some 400 km long and 300 km wide. A central corridor of approximately 80 by 30 km wide received the brunt of the radiation, with observed values ranging from seven to more than 100 mSv per hour (the dose limit for a certified radiation worker is 20 mSv in any one year).

100 mSv per hour

Localised hotspots recorded even higher values

The heaviest fallout settled on Chupadera Mesa, thirty miles from the detonation point. Here, cattle received severe burns from beta radiation particles, that looked similar to a sunburn. They were later purchased by the scientists at Los Alamos for further observation.

The test remained highly secretive

General Leslie Groves had previously drafted a press release for the New York Times to explain the incident, and the Manhattan Project leaders launched a premeditated campaign to downplay the early-morning loud explosion or bright light that people had witnessed, including individuals from cities as far away as Albuquerque and El Paso.

Nearly half-a-million people were living within a 200 km radius of the explosion, with some less than 18 km away.

Most of these civilians would still have been asleep when the bomb detonated just before dawn.

The press release explained that a large cache of ammunition and pyrotechnics had exploded during the night, but that no one had been killed or injured.

It also explained that due to weather conditions, there was a possibility that nearby citizens might be forced to evacuate.

Such an evacuation never occurred - presumably since it would have panicked the public

Retrospectively, given the amount of radioactive fallout generated by the explosion, an evacuation might well have been the best course of action.

New Mexico has the highest percentage of Hispanic and Latino Americans in the US, and the second-highest percentage of Native Americans.

The state is home to one–third of the Navajo Nation, 19 federally recognized Pueblo communities and three federally recognized Apache tribes.

The area has been inhabited for tens of thousands of years - human footprints discovered recently at White Sands National Park next to the Trinity site date back 23,000 years.

When planning and carrying out the nuclear bombing of New Mexico, the government took no precautions to protect the local civilian population from the effects of the Trinity test.

It concealed the nuclear nature of the explosion until the bombing of Hiroshima and Nagasaki 3 weeks later, by which time the fallout had settled over the region and been inhaled, ingested and absorbed.

In some families, cancer became prevalent across generations, especially thyroid cancers typical of radiation exposure to iodine 131. No studies were made - at the time or for many decades afterwards, not even basic records of cancer incidence were kept.

 “Our 90% UIs suggest that as many as 1,000 or as few as 290 cancers have already occurred or are projected to occur in the future that would not have occurred in the absence of residential radiation exposure from Trinity fallout. Most of the excess cancers are projected to have occurred or will occur among residents of Guadalupe, Lincoln, San Miguel, Socorro, and Torrance counties in 1945.”

70 years later, work to quantify the effects concluded -

Most of these 290-1000 deaths occurred among children under the age of 12

Most of these 290-1000 deaths occurred among children under the age of 12