Leslie Martin believed that the safety committee should always be present for bomb tests. The attendance of all members at Mosaic G1 was agreed at the fourth meeting of the AWTSC on 10 January 1956:
The Chairman was of the opinion that the whole of the Committee should be present at the trials and as it was not feasible to accommodate them on Narvik for any length of time, they should be located at Onslow with the rest of the mainland party. The Secretary was instructed to arrange for the accommodation of up to seven Safety Committee members at Onslow and to provide 2 vehicles for their use. Fast transport was also required to the Islands when the tests were on.
Members of the committee arrived at Onslow on 14 May, a onepub town on the mainland that was the departure point for test personnel to get to the Monte Bello Islands. They were quickly transferred to Narvik to witness the test and hurriedly met to discuss some of its worrying aspects, notably the enigmatic but definite hints about ‘light elements’ being used as ‘a boost’. This seemed to suggest a fusion weapon, something that the UK prime minister Anthony Eden had mentioned in a cable to Menzies the year before.
Light elements, particularly lithium and the isotopes of hydrogen called deuterium and tritium, are associated with fusion (thermonuclear) bombs, while the heavy elements uranium and plutonium are associated with fission bombs (although heavy water containing deuterium also was used for early fission weapons, for different reasons). However, it is possible to increase the explosive power of a fission bomb by initiating nuclear reactions among light elements to raise the temperature at the centre of the bomb quickly and by a great deal. The Royal Commission noted that:
the Committee members wanted to know which elements would be used and the quantity of each. The information was ultimately given by [operational commander Commodore Hugh] Martell and was said to have been restricted to their own use. What information was given is not recorded but as the firing proceeded, they were evidently satisfied with that information.
Mosaic G1, the smaller of the two Mosaic bombs, was detonated on 16 May. The members of the safety committee watched the explosion from the deck of the Narvik. Soon after G1, they departed the remote northwest but would be back just over a month later. Mosaic G2, the biggest device ever tested in Australia, would be detonated next.
Early signs of discord between the AWRE and the Australians were evident in the lead-up to Mosaic G2. The climatic conditions were so fragile and the window of opportunity so limited that when the AWTSC started to question aspects of the safety of Mosaic, Commander Martell (standing in for Penney, who did not attend Mosaic) was greatly displeased. The Australians believed that the safety committee gave them more power than was understood by the British, specifically the power of veto up to the moment of firing. As John Symonds observed, ‘The Operational Commander [Martell] had been given full responsibility for the operation on the UK side. The fact that the AWTSC had power to veto the operation was subsequently a surprise to the Operational Commander and caused him concern during the final stages of the actual test period’.
The AWTSC had been set up to hold such a veto, although exactly how it could actually stop the British carrying out a test was never explained or tested. The Royal Commission later found that despite the effective power of veto, the AWTSC ‘was not provided with sufficient information to discharge its function properly for the Mosaic series’. Another cause for both concern and fury for Martell was the firm direction from Howard Beale that the G2 test should not take place on a Sunday, for religious reasons, which was an Australian Government, not an AWTSC, requirement. The AWTSC was under considerable pressure from the Australian Government to ensure that Australia asserted itself in this first test series.
The deadlock was overcome when Martell and Adams provided the committee with a bit more information. G2 was detonated just after 10 am on 19 June. Earlier assurances from the British authorities had suggested that neither Mosaic device would be more than two and a half times Hurricane, suggesting an upper limit of about 62.5 kilotonnes. G2 may in fact have been a 98-kilotonne monster, although none of the Australians, including Leslie Martin, knew this at the time. (It should be noted that 98 kilotonnes remains a disputed figure. While it has been accepted by many authors, such as Robert Standish Norris and Joan Smith, others, such as Zeb Leonard, have suggested that there is no evidence that it was anything other than 60 kilotonnes, the figure recorded by the Royal Commission.) Nevertheless, the AWTSC knew it was big.
Martin prepared an upbeat if somewhat confused report onboard the Narvik which was sent to the prime minister. He suggested that the radiation cloud had moved out to sea, and also that some low-level radiation had spread eastwards across the Western Australian coast, towards the centre of the continent. ‘From analysis of the detailed data available to us the Safety Committee has satisfaction in reporting that the safety measures were completely adequate. There was absolutely no hazard to persons or damage to livestock or other property.’ The report made the rather strange statement that ‘the fallout on the NW coast was harmless in the extreme’. The Royal Commission later described this report as ‘misleading’, and Martin’s safety assurances as ‘grossly misleading and irresponsible’.
As previously discussed, Beale sent out a frantic ‘please explain’ to the safety committee at Monte Bello after a miner called Stewart Stubbs at Marble Bar, hundreds of kilometres away, detected high levels of radiation on two Geiger counters on 20 June. He used Geiger counters because he was involved in uranium exploration. In drizzling rain, Stubbs detected radiation that was ‘off the scale’, according to his testimony at the Royal Commission. He didn’t keep it to himself but radioed the airport at Port Hedland and spoke to someone whom he believed to be ‘a British scientist’. (He told the Royal Commission that he thought the name of the person was Penney, although Sir William was not at Monte Bello for Mosaic.) To whom exactly he spoke is unclear, but somehow his Geiger counter readings were provided to a journalist, who wrote a story that sparked public disquiet. According to the Royal Commission report, there was no official fallout monitoring station at Marble Bar, and therefore the degree of contamination there will never be known, ‘but if drizzling rain occurred, fallout contamination would have been greater than for dry conditions’.
One of the main roles of the AWTSC was to establish a network of monitoring stations around Australia, and eventually 60 stations were created, including in all state and territory capitals. However, their efficacy is open to debate. The safety committee oversaw an almost comical array of sticky paper that didn’t work when it rained, air pumps that measured airborne contamination but were regularly clogged by dust, battery-powered dosimeters with batteries that were usually dead, and other totally ineffectual methods for detecting and measuring radioactivity. Even for the times, these methods were inadequate. The 1984 Kerr Report on the aftermath of the British tests found that the ‘wearing of film badges (dosimeters) was so erratic and, in some cases, the measuring of doses so arbitrary, that… little weight can be placed on the validity of records as an index of long-term dose commitment’. The report noted, too, that when Mosaic G2 was about to be detonated, the AWRE supplied the AWTSC with 50 sets of fallout deposition monitoring equipment, but they deployed only 28 sets. Whether this was due to lack of time or lack of interest was not noted. The AWTSC also used aerial surveys by low-flying planes to obtain fallout measurements. The Royal Commission found that these readings would have to be multiplied by 10 to accurately reflect the contamination on the ground. But, as author Joan Smith wrote, ‘the Atomic Weapons Tests Safety Committee used the actual readings to give assurances to the public about the level of fallout from the tests’. Exactly why is unclear. It’s likely they did not want to upset the British or fuel public fears. They were also not in possession of all the information that the British had.