Operation Mosaic
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Operation Mosaic was a series of two British
The purpose of the tests was to explore increasing the
The
At the time of the
Background
During the early part of the
Britain thereby became the third nuclear power after the United States and the Soviet Union,
Purpose and site selection
In thinking about thermonuclear designs, the British scientists at the
The need for speed dictated the location. The
This was a sensitive matter; there was an agreement with Australia that no thermonuclear testing would be carried out there.[11] The Australian minister for supply, Howard Beale, responding to rumours reported in the newspapers,[15] asserted that "the Federal Government has no intention of allowing any hydrogen bomb tests to take place in Australia. Nor has it any intention of allowing any experiments connected with hydrogen bomb tests to take place here."[16] While a boosted fusion weapon is not a hydrogen bomb, the tests were indeed connected with hydrogen bomb development.[17]
The
Preparations
Like Operation Hurricane before it, the test was a Royal Navy responsibility. Planning commenced in February 1955 under the
On 18 July 1955 a five-man mission headed by Martell that included Adams, Menaul and
A small fleet of ships was assembled for Operation Mosaic. HMS Narvik began a refit at
They were augmented by RAN vessels, designated Task Group 308.2. The
Only a small party of
G1
Adams arrived at the Montebello Islands on 22 April, and was sufficiently impressed with the progress of works to schedule a scientific rehearsal for 27 April. A second scientific rehearsal was held on 2 May, followed by a full dress rehearsal on 5 May. The fissile material was delivered by an RAF Hastings to Onslow, from whence it was collected by HMS Alert on 11 May, and delivered to the Montebello Islands the following day. Strongly advise not showing Safety Committee any significant weapon details, but would not object to their seeing outside of cabled ball in centre section. They could be told that fissile material is at centre of large ball of high explosive and that elaborate electronics necessary to get symmetrical squash. No details of explosives configuration or inner components must be revealed. Appreciate that the position is awkward for you and that you must make minor concessions.[41]
Rather than stonewall, Adams and Martell disclosed the same information that had been given to Menzies, on condition that they kept it to themselves. This mollified them, and the G1 test went ahead.
The results of the test were mixed. The yield was between 15 and 20 kilotonnes of TNT (63 and 84 TJ), as had been anticipated,[44] although the mushroom cloud rose to 21,000 feet (6,400 m) instead of 14,000 feet (4,300 m) as predicted.[45] Valuable data was obtained. The implosion system had performed flawlessly, but the boosting effect of the lithium deuteride had been negligible; the process had not been fully understood.[44] HMS Diana, about 6 miles (9.7 km) from ground zero, was quickly decontaminated, and sailed for Singapore on 18 May.[35] The fallout cloud initially moved out to sea as predicted, but then reversed direction and drifted across northern Australia.[46] Tests on the aircraft at Onslow had detected signs of radioactive contamination from G1, indicating that some fallout had been blown over the mainland.[47]
G2
The results of G1 meant that a natural uranium tamper could be used in G2 without exceeding the planned 80 kilotonnes of TNT (330 TJ) limit agreed to with the AWTSC. (One of 100 kilotonnes of TNT (420 TJ) was used for safety purposes.) Scientific rehearsals for G2 were held on 28 and 31 May, followed by a full rehearsal on 4 June. The fissile core for the device was delivered to Onslow by RAF Hastings on 6 June, and once again was couriered to the Montebello Islands by HMS Alert. Then followed a period of waiting for suitable weather conditions.[21] The idea was to avoid, as far as possible, fallout being blown over the mainland. At this time of year winds at low altitudes were mainly subject to coastal influences, but above 10,000 feet (3,000 m) the prevailing winds were from the west. What was required was an interval during which the prevailing wind pattern was interrupted.[48]
These were not common at this time of the year; at the start of Operation Mosaic, it had been estimated that conditions favourable for G2 would occur only three days per month. In fact, since Narvik had arrived in March, not a single day had been suitable. And good weather conditions alone were insufficient; the meteorologists had to accurately forecast them. To allow Narvik to return to the UK and refit for Operation Grapple, the first test of a British hydrogen bomb, 15 July was set as the terminal date for Mosaic. As the deadline approached, William Cook, the scientist in charge of the hydrogen bomb project at Aldermaston, determined that in view of the results of G1, G2 was now more important than ever. He agreed that, if necessary, Grapple, could be delayed to conduct G2.[21] With time running short, the test procedures were altered to allow for a break in the weather to be exploited, with an earlier firing time and a shorter countdown.[49]
Another complication was safety. While the test of a larger device would normally mandate a larger safety area, Beale announced that G2 was going to be smaller than G1.[47][50][51] To avoid embarrassing him, the safety area was not enlarged, and no official announcement was made to the contrary.[47] The weather improved on 8 June, and Martell ordered the countdown to begin the following day, but Beale objected to a test being carried out on a Sunday. During Operation Totem there was an agreement that no tests would be conducted on Sundays. Mosex considered that matter in London, and directed Martell not to test on 10 June. The following 48 hours were unsuitable. On 17 June the meteorologists predicted a break in the weather and Martell ordered the countdown to recommence. Weather balloons indicated that conditions were stable between 5,000 and 24,500 feet (1,500 and 7,500 m), with an anomaly between 19,000 and 24,500 feet (5,800 and 7,500 m) that was not considered significant.[52]
G2 was detonated from a tower on Alpha Island at 02:14 UTC (10:14 local time) on 19 June. It produced a yield of 60 kilotonnes of TNT (250 TJ), making it the largest nuclear device ever detonated in Australia.
The cloud rose to 47,000 feet (14,000 m), considerably higher than the predicted 37,000 feet (11,000 m).[14] The procedure for collecting samples was far more limited than that of G1. A Land Rover was landed from a Landing Craft Assault (LCA) and driven by a party wearing protective clothing to within 400 feet (120 m) of ground zero to collect samples and recover the blast measurement equipment. Another sortie was made to collect film badges from Hermite Island, and Maddock collected a sample from the G2 crater.[55] The Canberra sent to fly through the cloud had trouble finding it, and only after some searching located it about 80 miles (130 km) from where it was supposed to be. The following day, the Canberra sent to track the cloud and collect more samples could not locate it at all.[56] The bulk of the fallout drifted over the Arafura Sea, but owing to different winds at different altitudes, part of it again drifted over the mainland.[57]
As fallout was detected over northern Australia by monitoring stations, in combination with Beale's announcement that G2 would be smaller than G1, an impression was generated that something had gone horribly wrong.
Aftermath
By the 1980s the radioactivity had decayed to the point where it was no longer hazardous to the casual visitor, but there were still radioactive metal fragments.[62] The island remained a prohibited area until 1992.[63] A 2006 zoological survey found that the wildlife had recovered.[64] As part of the Gorgon gas project, rats and feral cats were eradicated from the Montebello Islands in 2009, and birds and marsupials were transplanted from nearby Barrow Island to Hermite Island.[63] Today, the Montebello Islands are a park. Visitors are advised not to spend more than an hour per day at the test sites, or to take relics of the tests as souvenirs.[63] A pyramid-shaped obelisk marks the site of the G2 explosion on Alpha Island.[65]
Summary
Name | Date time (UTC) | Local time zone
|
Location
|
Elevation + height | Delivery | Yield | References | Notes |
---|---|---|---|---|---|---|---|---|
G1 | 16 May 1956 03:50 | AWST (+8 hrs) | Trimouille Island, Montebello Islands, Western Australia 20°23′S 115°33′E / 20.38°S 115.55°E | 4 m (13 ft) + 31 m (102 ft) | tower, weapons development | 15 kt | [42] | lithium deuteride
|
G2 | 19 June 1956 02:14 | AWST (+8 hrs) | Alpha Island, Montebello Islands, Western Australia 20°25′S 115°32′E / 20.41°S 115.54°E | 8 m (26 ft) + 31 m (102 ft) | tower, weapons development | 60 kt | [42][53] | Boosted fission with lithium deuteride and natural uranium tamper |
Notes
- ^ Gowing 1964, pp. 108–111.
- ^ Jones 2017, pp. 1–2.
- ^ Gowing & Arnold 1974a, pp. 181–184.
- ^ Cathcart 1995, pp. 24, 48, 57.
- ^ Jones 2017, p. 25.
- ^ Arnold & Smith 2006, p. 47.
- ^ Paul 2000, pp. 196–197.
- ^ Gowing & Arnold 1974b, pp. 500–501.
- ^ Baylis 1995, pp. 160–163, 179–185.
- ^ Arnold & Smith 2006, pp. 82–86.
- ^ a b c d Arnold & Smith 2006, pp. 106–110.
- ^ Leonard 2014, p. 209.
- ^ Arnold & Smith 2006, pp. 52–53, 89.
- ^ a b c McClelland 1985a, p. 233.
- ^ "No Hydrogen Bomb Tests". The Canberra Times. Vol. 30, no. 8, 772. Australian Capital Territory, Australia. 16 February 1956. p. 1. Retrieved 28 May 2017 – via National Library of Australia.
- ^ "We Bar H-Bomb Test Here So Britain Seeks Ocean Site". The Argus (Melbourne). Victoria, Australia. 19 February 1955. p. 1. Retrieved 28 May 2017 – via National Library of Australia.
- ^ a b c Arnold & Smith 2006, pp. 109–112.
- ^ a b Symonds 1985, p. 310.
- ^ a b McClelland 1985b, pp. 478–479.
- ^ Arnold & Smith 2006, p. 301.
- ^ a b c Arnold & Smith 2006, pp. 124–126.
- ^ "Maralinga nuclear testing. Mosaic tests: were they H-bombs?". The Canberra Times. Vol. 59, no. 17, 900. Australian Capital Territory, Australia. 1 October 1984. p. 12. Retrieved 28 May 2017 – via National Library of Australia.
- ^ Symonds 1985, pp. 314–315.
- ^ a b c Arnold & Smith 2006, p. 112.
- ^ Arnold & Smith 2006, pp. 111–112.
- ^ Sainsbury, A. B. (25 February 1999). "Obituary: Vice-Admiral Sir Hugh Martell". The Independent. Archived from the original on 24 May 2022. Retrieved 5 August 2018.
- ^ Boyes 2015, p. 198.
- ^ Symonds 1985, p. 314.
- ^ Arnold & Smith 2006, p. 113.
- ^ a b c d e Arnold & Smith 2006, pp. 115–117.
- ^ McClelland 1985a, p. 262.
- ^ Djokovic 2016, pp. 2–3.
- ^ a b c Symonds 1985, pp. 323–329.
- ^ a b c d e Arnold & Smith 2006, p. 121.
- ^ Kainikara & Burns 2016, pp. 145–148.
- ^ a b Symonds 1985, pp. 333–335.
- ^ "WA Govt to discuss demand for A-test ban". Tribune. No. 946. New South Wales, Australia. 9 May 1956. p. 3. Retrieved 8 August 2018 – via National Library of Australia.
- ^ a b Arnold & Smith 2006, pp. 122–124.
- ^ McClelland 1985b, pp. 481–482.
- ^ McClelland 1985b, pp. 482–483.
- ^ a b c "Britain's Nuclear Weapons - British Nuclear Testing". Nuclear Weapons Archive. Retrieved 4 August 2018.
- ^ McClelland 1985a, pp. 264–266.
- ^ a b Arnold & Smith 2006, pp. 124–125.
- ^ McClelland 1985a, pp. 245–246.
- ^ Symonds 1985, pp. 337–342.
- ^ a b c Arnold & Smith 2006, pp. 125–126.
- ^ Symonds 1985, p. 319.
- ^ McClelland 1985a, p. 246.
- ^ "No Risks In A Bomb Test". The Canberra Times. Vol. 30, no. 8, 858. Australian Capital Territory, Australia. 28 May 1956. p. 1. Retrieved 9 August 2018 – via National Library of Australia.
- ^ Symonds 1985, pp. 351–352.
- ^ Symonds 1985, pp. 346–351.
- ^ a b Leonard 2014, pp. 210–212.
- ^ Leonard 2014, p. 218.
- ^ McClelland 1985a, pp. 266–267.
- ^ McClelland 1985a, p. 253.
- ^ a b Symonds 1985, pp. 351–355.
- ^ "Inquiry on Atomic Cloud Ordered". The Canberra Times. Vol. 30, no. 8, 891. Australian Capital Territory, Australia. 22 June 1956. p. 1. Retrieved 9 August 2018 – via National Library of Australia.
- ^ Symonds 1985, pp. 356–357.
- ^ Arnold & Smith 2006, pp. 133–137.
- ^ Cherry, Sorenson & Phelps 2012, pp. 427–428.
- ^ Cooper, Lokan & Williams 1983, p. 6.
- ^ a b c "Montebello Islands". Department of Parks and Wildlife. Retrieved 25 February 2017.
- ^ Maryan & Bush 2007, pp. 247–251.
- Sydney Morning Herald. 22 September 2012. Retrieved 2 July 2017.
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- OCLC 31241690.
- Cherry, Simon R.; Sorenson, James A.; Phelps, Michael E. (2012). Physics in Nuclear Medicine (fourth ed.). Philadelphia: Elsevier/Saunders. OCLC 727303207.
- Cooper, Malcolm B.; Lokan, Keith H.; Williams, Geoffrey A. (1 November 1983). The Radiological Status of the Monte Bello Islands: May 1983 (PDF) (Technical report). Yallambie, Victoria: Australian Radiation Laboratory. Archived from the original (PDF) on 26 March 2016. Retrieved 18 December 2013.
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- Kainikara, Sanu; Burns, David, eds. (2016). "RAAF Involvement in Nuclear Testing" (PDF). Pathfinder. 7 (232). Air Power Development Centre: 145–148. ISSN 1836-7712. Retrieved 5 April 2020.
- Leonard, Zeb (22 May 2014). "Tampering with History: Varied Understanding of Operation Mosaic". Journal of Australian Studies. 38 (2): 205–219. S2CID 144611309.
- Maryan, Brad; Bush, Brian (28 February 2007). "Rediscovery of Aprasia rostrata on the Montebello Islands". The Western Australian Naturalist. 25 (4): 247–251. ISSN 0508-4865. Retrieved 20 February 2017.
- OCLC 60240750. Archived from the original(PDF) on 31 March 2019. Retrieved 8 August 2018.
- OCLC 60240751. Archived from the original(PDF) on 31 March 2019. Retrieved 8 August 2018.
- Naval Intelligence Division (June 1956). Australia Station Intelligence Summary (PDF) (Report). Royal Australian Navy. Retrieved 7 August 2018.
- Paul, Septimus H. (2000). Nuclear Rivals: Anglo-American Atomic Relations, 1941–1952. Columbus, Ohio: Ohio State University Press. OCLC 43615254.
- Symonds, J. L. (1985). A History of British Atomic Tests in Australia. Canberra: Australian Government Publishing Service. OCLC 18084438.