Test No. 6
{{short description|Sixth Chinese nuclear test, 1967}}
{{Infobox Nuclear weapons test
|name =Test No. 6
|picture =Test6 1967.gif
|picture_description =Test No.6, 3.3 megatons.
|country =China
|test_site =Lop Nur Test Base
|period =June 17, 1967
|number_of_tests = 1
|test_type =Atmospheric
|device_type =Fusion
|max_yield = {{convert|3.3|MtonTNT|lk=in}}
|previous_test =596
|next_test =16th test
}}
Test No. 6 is the codename for China's first full-scale test of a two-staged thermonuclear device, on 17 June 1967, yielding 3.3 megatons of TNT. It followed the first two-stage thermonuclear test, at a smaller 122 kt yield, in December 1966. It was the sixth nuclear test that was carried out by the People's Republic of China, and represented the completion of the "second bomb" i.e. thermonuclear bomb component of the "Two Bombs, One Satellite" program. With these two tests, China became the fourth nation to develop thermonuclear weapons, following the US, USSR, and UK.
Development
= Background =
The goal of China was to produce a thermonuclear device of at least a megaton in yield that could be dropped by an aircraft or carried by a ballistic missile. Several explosions to test thermonuclear weapon designs, characteristics and yield boosting preceded the thermonuclear test.{{cite web |date=September 26, 2003 |title=China's Nuclear Weapon Development, Modernization and Testing |url=http://www.nuclearthreatinitiative.org/db/china/wnwmdat.htm |url-status=dead |archiveurl=https://web.archive.org/web/20111008195804/http://www.nuclearthreatinitiative.org/db/china/wnwmdat.htm |archivedate=October 8, 2011 |accessdate=November 4, 2011 |publisher=Nuclear Threat Initiative}}
China was motivated to pursue nuclear weapons in part due to the First and Second Taiwan Strait Crises in 1955 and 1958. The United States had threated nuclear attacks on the People's Liberation Army in each, and stationed nuclear weapons in Taiwan during and after the second crisis.
China had also received extensive technical help from the Soviet Union to jump-start their nuclear program. In June 1958 the Soviet Union supplied a 10 MW heavy-water research reactor (HWRR-I) and a 25 MeV cyclotron to the Beijing-based China Institute of Atomic Energy. Crucially, in 1958, Soviet experts helped design a lithium deuteride production plant at Baotou (Plant 212). However, by 1960, the rift between the Soviet Union and China had become so great that the Soviet Union ceased all assistance to China and refused to help the Chinese government with their nuclear program.
Unlike the US or USSR thermonuclear weapons programs, Chinese nuclear facilities were at the time limited to production of highly enriched uranium and lithium deuteride, and so were not able to use the slightly different properties of weapons-grade plutonium and tritium.
= Thermonuclear weapons program =
Peng Huanwu, as director of the Ninth Academy of the Second Ministry of Machine Industry, initially led China's thermonuclear weapons program. Beginning in 1963, they spent a year investigating the "layer-cake" model, for which they had received some information on the Soviet design (sloika), first tested in RDS-6s in 1953. After a year they concluded that this design could not be scale to achieve the megaton yields of the thermonuclear weapons so far tested by the US, USSR, and UK.
From 1964 to 1965, thermonuclear weapons development was restarted from scratch. The Ninth Academy scoured foreign scientific literature and news reports, including all issues of the New York Times and Pravda since 1945, to no avail. However, Zhou Guangzhao pointed out magazine photographs of nuclear missiles, which were generally in the shape of a long cylinder, indicating different physical principles to the large spherical layer-cake.
From September 1965, Yu Min, Cai Shaohui, and over 50 other researchers gathered in Shanghai, to focus on rapid theoretical development of the hydrogen bomb. Yu Min held a lecture series on the layer-cake bomb, and in doing so realized its flaw was its slow production of tritium from lithium deuteride i.e. Jetter cycle. Work proceeded for almost 100 days, using both digital computers and manual calculation. At one point, programmer Liu Yuqin accidentally entered a "light nuclear materials" (presumably lithium deuteride and its fusion products{{Citation needed|date=June 2025}}) value 20 times too large, and astonished the researchers with a three megaton yield. This mistake allowed them to focus on the problem of increasing the light nuclear material density.
On 29 October, Yu and Cai discussed the problem while walking a field trail after dinner. and decided to explore less physical but more ideal models for compression of the secondary. Yu Min subsequently devised a "sophisticated structure" to maximize one form of energy delivered to the secondary (presumably X-rays{{Citeneed|date=June 2025}}). From 1 November, simulations on the J501 computer showed that a one-megaton bomb was feasible with this design.
In China this design has become known as the {{Ill|Yu Min configuration|zh|于敏构型}} (于敏构型, Yú Mǐn gòu xíng). The Chinese government claims that although it is a multi-stage thermonuclear weapon design, it is distinct from the Teller-Ulam design assumed to be used by the other four thermonuclear nations, allowing further miniaturization, and that together these two comprise the only feasible thermonuclear weapon designs.{{Cite web |title=全球氢弹仅两种 “于敏构型”是其一 _大公网 |url=http://www.takungpao.com/news/232108/2019/0117/236598.html |archive-url=https://web.archive.org/web/20190125103518/http://www.takungpao.com/news/232108/2019/0117/236598.html |archive-date=2019-01-25 |access-date=2023-10-14 |website=www.takungpao.com |url-status=live}}
= Thermonuclear testing =
Despite a theoretically sound multi-stage thermonuclear weapon design, the Chinese government chose to first test the layer-cake design as China's third nuclear test. All testing occurred at Lop Nur salt lake. It was codenamed "596L", as it was based on China's first nuclear device, "596", a fission implosion bomb, but with an extra layer of lithium deuteride represented by the "L". The weapon was tested on 9 May 1966, dropped from a Xi'an H-6 bomber, and yielded approximately 220 kt.
Next, a small-scale test of the two-stage thermonuclear design was planned, codenamed "629". This was significant delayed by at least three unstated technical problems in the nuclear primary system. Another problem was that the "energy transport system" key to the Yu Min configuration may accidentally trigger the primary. The development was also obstructed by the outbreak of the Cultural Revolution in May 1966. Instead of an air drop, a tower test was to be used for more precise measurements. To minimize fallout from ground contamination, a 50 meter circle was paved with concrete and a 230 meter radius circle with crushed stones. The device yield was also reduced by the use of less thermonuclear material and a lead tamper, designed for 100 kilotons. The test took place on 28 December 1966, yielding 122 kilotons, and validating the staged thermonuclear design.
Following the successful 629 test, full efforts were devoted to a full-scale hydrogen bomb test as "Test No. 6", codenamed "639". It was decided to cannibalize the materials from the backup thermonuclear project, "658", which would have been a three-staged layer-cake design capable of reaching one megaton, similar to the British backup design Orange Herald Large, and originally intended for a test on 1 October 1967. In the fervor of the Cultural Revolution, the Ninth Academy eagerly competed against Peng Huanwu's prediction that France would test its first hydrogen bomb in 1967, and moved the speculative 639 test date from October to July.
Test
The device, codenamed "639", was detonated at Lop Nur Test Base, or often dubbed as Lop Nur Nuclear Weapon Test Base, in Malan, Xinjiang, on 17 June 1967.{{Cite web |last=Zhang |first=Hui |date=2024-04-11 |title=The short march to China’s hydrogen bomb |url=https://thebulletin.org/2024/04/the-short-march-to-chinas-hydrogen-bomb/ |access-date=2024-04-15 |website=Bulletin of the Atomic Scientists |language=en-US |archive-date=2024-04-11 |archive-url=https://web.archive.org/web/20240411142418/https://thebulletin.org/2024/04/the-short-march-to-chinas-hydrogen-bomb/ |url-status=live }} With successful testing of this two-stage thermonuclear device, China became the fourth country to have successfully developed a thermonuclear weapon after the United States, Soviet Union and the United Kingdom. It was dropped from a Xian H-6 (Chinese manufactured Tu-16) of the 36th Air Division and was parachute-retarded for an airburst at 2960 meters.{{Cite journal |last=Allen |first=Kenneth W. |date=2 May 2022 |title=PLA Air Force Bomber Force Organization |url=https://www.airuniversity.af.edu/Portals/10/CASI/documents/Research/CASI%20Articles/2022-05-02%20PLAAF%20Bomber%20Organization.pdf |journal=China Aerospace Studies Institute |location=Air University, Montgomery, Alabama |access-date=2024-04-15 |archive-date=2022-11-18 |archive-url=https://web.archive.org/web/20221118095602/https://www.airuniversity.af.edu/Portals/10/CASI/documents/Research/CASI%20Articles/2022-05-02%20PLAAF%20Bomber%20Organization.pdf |url-status=live }} The bomb was a two-stage device with a boosted highly enriched uranium primary and natural uranium tamper. The yield was 3.3 megatons.
The film of the prior 1966 tests have been released, as well as an unidentified later test.{{Citation|last=wolfkinler|title=中国的核试验1966|date=2013-04-08|url=https://www.youtube.com/watch?v=nra9fWC-pQc&t=8m40s |archive-url=https://ghostarchive.org/varchive/youtube/20211221/nra9fWC-pQc |archive-date=2021-12-21 |url-status=live|accessdate=2018-01-24}}{{cbignore}}
It was a fully functional, full-scale, two-stage hydrogen bomb, tested just 32 months after China had made its first fission device. It remains to date the fastest of any country to successfully develop this capability.
Aftermath
Following his death in 2019, Yu Min became the first deceased recipient of the Medal of the Republic, awarded by Xi Jinping and the Standing Committee of the National People's Congress.{{Cite web |title=（受权发布）中华人民共和国主席令（第三十四号） |url=http://www.xinhuanet.com/2019-09/17/c_1125006548.htm |archive-url=https://web.archive.org/web/20200325060842/http://www.xinhuanet.com/2019-09/17/c_1125006548.htm |archive-date=2020-03-25 |accessdate=2019-09-17 |work=新华网 |url-status=live}} {{webarchive|url=https://web.archive.org/web/20200325060842/http://www.xinhuanet.com/2019-09/17/c_1125006548.htm}}
Gallery
File:ChinaTest6 3.jpg
File:ChinaTest6 2.jpg
File:ChinaTest6 1.jpg
File:Test 6 China.ogg
See also
References
= Citations =
{{Reflist}}
= Sources =
{{refbegin}}
; Books
- Norris, Robert, Burrows, Andrew, Fieldhouse, Richard. Nuclear Weapons Databook, Volume V, British, French and Chinese Nuclear Weapons. San Francisco, CA: Westview Press, 1994. {{ISBN|0-8133-1612-X}}.
{{refend}}
Category:Cold War weapons of China
Category:Chinese nuclear weapons testing
Category:1967 in military history