ounce). Construction of the first PIPPA commenced at Calder Hall in March 1953. For cost reasons PIPPA was to operate in such a way that there would be a higher proportion of plutonium-240 present with the plutonium-239 product than in the Windscale-produced material. Since plutonium-240 is prone to spontaneous fission, this increased the risk of criticality accident and a fizzle that would reduce the yield. Nuclear testing was required to gauge the effect of an increased proportion of plutonium-240. The Royal Navy was unable to provide the level of support it had for the Operation Hurricane test in the time available, so the Montebello Islands were ruled out. The search for an alternative site on the mainland in the vicinity of the Woomera Rocket Range had already begun in June 1952. Surveys of the area were carried out by Len Beadell, the surveyor at the Long Range Weapons Establishment (LRWE). Harry Pritchard, the Chief Superintendent there, loaned a Bristol Sycamore helicopter for the purpose. A site, originally given the codename X200 but later renamed Emu Field, was selected. It was an isolated dry, flat clay and sandstone expanse in the Great Victoria Desert north west of Woomera, South Australia. A natural claypan known as the Dingo Claypan provided a ready-made airstrip. In August, Sir William Penney, the Chief Superintendent Armament Research (CSAR) at the British Ministry of Supply, and the head of the British atomic weapon development effort, notified W. A. S. Butement, the Chief Scientist at the Australian Department of Supply, of his intention to visit the site before the Hurricane test. Butement warned Penney that it was very remote, and that Beadell and his companions might well have been the first non-Aboriginal people to see the area. Sir John Cockcroft, the director of the Atomic Weapons Research Establishment, personally lodged a formal request for a feasibility study with the Prime Minister of Australia, Robert Menzies, at a meeting on 4 September. Other matters discussed included the attendance of Butement and Leslie Martin, the Australian Defence Scientific Adviser, as Australian observers at the Hurricane test, the creation of the Australian Atomic Energy Commission, and the supply of Australian uranium to the UK. Cockcroft reported to Sir Roger Makins at the Foreign Office that Menzies had agreed in principle to Penney's reconnaissance of the Emu Field site. Penney flew in to the Dingo Claypan in a Royal Air Force (RAF)