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| Fig. 1: Castle Bravo nuclear weapon test on March 1, 1954. (Source: Wikimedia Commons) |
In 1945, the US began to regularly perform nuclear-explosion testing. [1] This taught the United States a significant amount about nuclear weapons and demonstrated its ability to produce highly effective weapons of mass destruction. Despite the potential dangers and drawbacks, nuclear testing remained an essential part of the US nuclear weapons program for almost half a century because it provided scientist with answers to paramount questions, and helped them ensure the reliability of devices that, if defective, could cause unintended catastrophic harm.
People began considering restrictions around nuclear testing in the mid-1950s as they saw more of the dangers associated with testing these weapons. [2] In 1954, the US' thermonuclear explosive test of "Castle Bravo" had a yield of 15 megatons (see Fig. 1). A megaton is equivalent to one million tons of TNT and is a unit of explosive power that is used primarily to measure the power of nuclear weapons. A TNT equivalent is a value that represents the amount the mass of the charge needs to be multiplied by in order to get the same blast wave propagation. [3] By convention, one ton of TNT is equivalent in energy to 4.184 × 109 joules (J). Thus one megaton is equivalent to 4.184 × 1015 J, and fifteen megatons are equal to 6.276 × 1016 J. This was the yield of "Castle Bravo," (which was much larger than expected). Its fallout led to the death of a Japanese fisherman. Following a US-Soviet moratorium on nuclear tests from 1958 to 1961, the Soviet Union performed thirty atmospheric tests in just sixty days. The US responded by completing forty tests in the next six months. [2] After this, the main barrier preventing bans on nuclear tests were concerns of verification capabilities. In 1963, following the Cuban Missile Crisis, the United States, the United Kingdom, and Soviet Union all signed the Limited Nuclear Test Ban Treaty. [4] This prohibited nuclear-explosion testing in the atmosphere, space, and sea - though allowed for continued testing underground. In 1974, the US and Soviets agreed to limit the size of underground explosions under the terms of the Threshold Test-Ban Treaty. [2] The Threshold Test-Ban Treaty set a maximum yield of 150 kilotons and relied on seismic verification.
In order for a comprehensive test ban to become a reality, both sides felt they needed better verification to identify when tests occur. In 1976, the Conference on Disarmament commissioned a group of scientists to look into possible solutions; they continued to make progress on this for the next eighteen years. [2] In 1988, the US and USSR both agreed to take part in the Joint Verification Experiment, where both countries agreed to do on-site testing at the one another's testing facilities to help verify the size of underground nuclear tests - something inconceivable not long before. [2] In 1991, the Soviet Union declared a unilateral moratorium on nuclear testing, and the US conducted its final nuclear weapons test the following year. Negotiations for the Comprehensive Nuclear Test Ban Treaty (CTBT) began in 1994; President Clinton was the first to sign the treaty two years later, although its ratification was blocked by a 48-51-1 Senate vote in 1999. The objections largely centered around whether the stockpile could be maintained long-term without any real testing. [2] The Science-Based Stockpile Stewardship Program (SSP) was previously established by the Clinton Administration and has since strived to maintain the safety and reliability of the nation's nuclear stockpile without relying on explosive testing. [1] This, of course, has been done in numerous ways: performing annual assessments of weapons, extending the life of old ones, dismantling retired ones, etc.
Today, scientists and designers use supercomputer modeling to carry out checks on all the possible conditions that can affect nuclear explosives. [5] According to Bruce T. Goodwin, principal associate director at Livermore for weapons programs of Lawrence Livermore National Laboratory, "We have a more fundamental understanding of how these weapons work today than we ever imagined when we were blowing them up." Laboratories like Livermore are the ones that verify the safety and reliability of the nuclear stockpile to the president. [5] A greater understanding of the process behind a thermonuclear explosion allows scientists to understand how and why these weapons work, much more so then they could before.
The United States has come a long way from its original days of testing nuclear weapons. We are able to use supercomputers to create realistic models of what occurs inside a nuclear explosion and learn from them like never before. [5] Maintaining nuclear devices is of the utmost importance and, although there are high risks and many factors in play, the hope is that the US can continue to use scientific disciplines and technological advances to do so while refraining from resuming nuclear explosive testing.
© Nick Barber. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] M. L. Adams, "Stockpile Stewardship Past, Present, and Future," AIP Conf. Proc. 1596, 115 (2014).
[2] E. Ifft, "The Comprehensive Nuclear-Test-Ban Treaty and US security," Nonproliferation Review 23, 385 (2016).
[3] R. Panowicz, M. Konarzewski, and M. Trypolin, "Analysis of Criteria for Determining a TNT Equivalent," J. Mech. Eng. 63, 666 (2017).
[4] V. W. Sidel and B. S. Levy, "Proliferation of Nuclear Weapons: Opportunities for Control and Abolition," Am. J. Public Health 97, 1589 (2007).
[5] D. E. Hoffman, "Supercomputers Offer Tools for Nuclear Testing and Solving Nuclear Mysteries," Washington Post, 1 Nov 11.
