Nuclear weapons testing

Because of their destruction and fallout, testing has seen opposition by civilians as well as governments, with international bans having been agreed on.

The first nuclear device was detonated as a test by the United States at the Trinity site in New Mexico on July 16, 1945, with a yield approximately equivalent to 20 kilotons of TNT.

The most recent confirmed nuclear test occurred[update] in September 2017 in North Korea.

[4][5] A theme has generally been that even though simulations cannot fully replace physical testing, they can reduce the amount of it that is necessary.

[6] Hydronuclear tests study nuclear materials under the conditions of explosive shock compression.

They are the only type of tests allowed under the interpretation of the Comprehensive Nuclear-Test-Ban Treaty tacitly agreed to by the major atomic powers.

[8][9] Subcritical tests continue to be performed by the United States, Russia, and the People's Republic of China, at least.

The test gave a good approximation of many of the explosion's effects, but did not give an appreciable understanding of nuclear fallout, which was not well understood by the project scientists until well after the atomic bombings of Hiroshima and Nagasaki.

The fallout plume spread high levels of radiation for over 100 miles (160 km), contaminating populated islands in nearby atoll formations.

Though they were soon evacuated, many of the islands' inhabitants suffered from radiation burns and later from other effects such as increased cancer rate and birth defects, as did the crew of the Japanese fishing boat Daigo Fukuryū Maru.

One crewman died from radiation sickness after returning to port, and it was feared that the radioactive fish they had been carrying had made it into the Japanese food supply.

The United States responded in 1962 with Operation Dominic, involving dozens of tests, including the explosion of a missile launched from a submarine.

The only acknowledged nuclear power that claims never to have conducted a test was South Africa (although see Vela incident), which has since dismantled all of its weapons.

Israel is widely thought to possess a sizable nuclear arsenal, though it has never tested, unless they were involved in Vela.

In total nuclear test megatonnage, from 1945 to 1992, 520 atmospheric nuclear explosions (including eight underwater) were conducted with a total yield of 545 megatons,[21] with a peak occurring in 1961–1962, when 340 megatons were detonated in the atmosphere by the United States and Soviet Union,[22] while the estimated number of underground nuclear tests conducted in the period from 1957 to 1992 was 1,352 explosions with a total yield of 90 Mt.

In US context, it was decided during the Manhattan Project that yield measured in tons of TNT equivalent could be imprecise.

These treaties were proposed in response to growing international concerns about environmental damage among other risks.

Most countries have signed and ratified the Partial Nuclear Test Ban, which went into effect in October 1963.

[47] The 1996 Comprehensive Nuclear-Test-Ban Treaty (CTBT) bans all nuclear explosions everywhere, including underground.

For that purpose, the Preparatory Commission of the Comprehensive Nuclear-Test-Ban Treaty Organization is building an international monitoring system with 337 facilities located all over the globe.

These "Annex 2 States" participated in the negotiations on the CTBT between 1994 and 1996 and possessed nuclear power or research reactors at that time.

The mushroom cloud from the Castle Bravo thermonuclear weapon test in 1954, the largest nuclear weapons test ever conducted by the United States
Four major types of nuclear testing: 1. atmospheric, 2. underground , 3. exoatmospheric, and 4. underwater
Subcritical experiment at the Nevada National Security Site
The Phoenix of Hiroshima (foreground) in Hong Kong Harbor in 1967, was involved in several famous anti-nuclear protest voyages against nuclear testing in the Pacific.
The 6,900-square-mile (18,000 km 2 ) expanse of the Semipalatinsk Test Site (indicated in red), attached to Kurchatov (along the Irtysh river ). The site comprised an area the size of Wales . [ 20 ]
In 1954 the Castle Bravo fallout plume spread dangerous levels of radiation over an area over 100 miles (160 km) long, including inhabited islands.
Because of concerns about worldwide fallout levels, the Partial Test Ban Treaty was signed in 1963. Above are the per capita thyroid doses (in rads ) in the continental United States resulting from all exposure routes from all atmospheric nuclear tests conducted at the Nevada Test Site from 1951 to 1962.
Over 2,000 nuclear tests have been conducted in over a dozen different sites around the world. Red Russia/Soviet Union, blue France, light blue United States, violet Britain, yellow China, orange India, brown Pakistan, green North Korea, and light green (territories exposed to nuclear bombs). The black dot indicates the location of the Vela incident .
"Baker Shot", part of Operation Crossroads , a nuclear test by the United States at Bikini Atoll in 1946
Graph of nuclear testing
Graph of nuclear testing
Atmospheric 14 C Bomb pulse , New Zealand [ 33 ] and Austria . [ 34 ] The New Zealand curve is representative for the Southern Hemisphere, the Austrian curve is representative for the Northern Hemisphere. Atmospheric nuclear weapon tests almost doubled the concentration of 14 C in the Northern Hemisphere. [ 35 ]