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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Castle Bravo | 8/9 | https://en.wikipedia.org/wiki/Castle_Bravo | reference | science, encyclopedia | 2026-05-05T13:10:17.178423+00:00 | kb-cron |
==== Total yield and fission yield energy budgets ==== Following the higher-than-expected yields throughout Operation Castle (48.2 Mt total yield to the expected 23 Mt), US policy on thermonuclear testing in the Pacific changed. In 1956, Operation Redwing was conducted on an "energy budget", limiting the total testing yield to 20 Mt, and specifically limiting the fission yield, contentiously divided between Los Alamos Scientific Laboratory and University of California Radiation Laboratory at Livermore. While some very "dirty" fission weapons were tested, this also began the usage of the "materials substitution method", where the fission product fallout-producing uranium-238 tamper was replaced with a "clean" lead tamper, at the cost of halving the yield.
==== 15 megaton yield standard ==== In 1958, during preparation for Operation Hardtack I, the second round of thermonuclear testing since Castle, President Eisenhower established an unwritten rule that no single American test could exceed the 15 Mt yield of Castle Bravo. His successor, John F. Kennedy, adhered to this standard, even following the 50 Mt Soviet Tsar Bomba test in 1961 and pressure from the Department of Defense, Atomic Energy Commission, and the Livermore laboratory. Following the 1963 Partial Nuclear Test Ban Treaty against non-underground tests, American testing continued underground, with the largest yield in the 1971 Grommet Cannikin test at 5 Mt.
=== Impact on scientific direction ===
==== Fission energy ====
The US government's attempts at public relations damage control focused around the existing language of the Atoms for Peace initiative launched four months prior, expanding to the concept of the "peaceful thermonuclear atom". Speaking at a conference six months later, Lewis Strauss, the chair of the Atomic Energy Commission and a primary influence in the crash program of hydrogen bomb development, famously promised a peaceful era of nuclear energy:
It is not too much to expect that our children will enjoy in their homes electrical energy too cheap to meter, will know of great periodic regional famines in the world only as matter of history, will travel effortlessly over the seas and under them and through the air with a minimum of danger and at great speeds, and will experience a lifespan far longer than ours, as disease yields and man comes to understand what causes him to age. This is the forecast for an age of peace. The Soviet Union had already announced electrical grid connection of the Obninsk Nuclear Power Plant on 27 June. The United States would achieve this briefly with the BORAX-III reactor in 1955 and permanently with the Shippingport Atomic Power Station in 1957.
==== Fusion energy ====
===== Energy from conventional yields =====
In 1957, hydrogen bomb architect Edward Teller and other Livermore weapons scientists proposed a gigawatt-level electrical plant, based on steam generation from 1 megaton bombs dropped every 12 hours into a 1,000 ft cavity. American research on such plants continued throughout the Cold War.
===== Energy from minimal yields =====
Livermore scientist John Nuckolls began a "hectoton group" (100 tons) at the laboratory, investigating ways to remove the fission primary and inventing the concept of low-yield implosions of deuterium-tritium pellets i.e. inertial confinement fusion.
== Weapon history ==
The Soviet Union had previously used lithium deuteride in its Sloika design (known as the "Joe-4" in the U.S.), in 1953. It was not a true hydrogen bomb; fusion provided only 15–20% of its yield, most coming from boosted fission reactions. Its yield was 400 kilotons, and it could not be infinitely scaled, as with a true thermonuclear device. The Teller–Ulam-based "Ivy Mike" device had a much greater yield of 10.4 Mt, but most of this also came from fission: 77% of the total came from fast fission of its natural-uranium tamper. Castle Bravo had the greatest yield of any U.S. nuclear test, 15 Mt, though again, a substantial fraction came from fission. In the Teller–Ulam design, the fission and fusion stages were kept physically separate in a reflective cavity. The radiation from the exploding fission primary brought the fuel in the fusion secondary to critical density and pressure, setting off thermonuclear (fusion) chain reactions, which in turn set off a tertiary fissioning of the bomb's 238U fusion tamper and casing. Consequently, this type of bomb is also known as a "fission-fusion-fission" device. The Soviet researchers, led by Andrei Sakharov, developed and tested their first Teller–Ulam device in 1955. The publication of the Bravo fallout analysis was a militarily sensitive issue, with Joseph Rotblat possibly deducing the staging nature of the Castle Bravo device by studying the ratio and presence of tell-tale isotopes, namely uranium-237, present in the fallout. This information could potentially reveal the means by which megaton-yield nuclear devices achieve their yield. Soviet scientist Andrei Sakharov hit upon what the Soviet Union regarded as "Sakharov's third idea" during the month after the Castle Bravo test, the final piece of the puzzle being the idea that the compression of the secondary can be accomplished by the primary's X-rays before fusion began. The Shrimp device design later evolved into the Mark 21 nuclear bomb, of which 275 units were produced, weighing 17,600 pounds (8,000 kg) and measuring 12.5 feet (3.8 m) long and 58 inches (1.5 m) in diameter. This 18-megaton bomb was produced until July 1956. In 1957, it was converted into the Mark 36 nuclear bomb and entered into production again.
== Health impacts ==