Optimism in the new lab prompted UCRL to even propose a class of such "small weapons" making use of the material, dubbing it as the "Geode". Skepticism from Los Alamos notwithstanding, Edward Teller remained interested in the concept, and he and Ernest Lawrence experimented with such devices in the early 1950s at the UCRL, ( University of California Radiation Laboratory, later Lawrence Livermore National Laboratory). Post war, Los Alamos physicists continued research on the subject at low priority while a Monte-Carlo simulation in December 1949 : 258 showed that the core could in principle work and result in a weapon considerably smaller than the MK 5, strong skepticism arose as the inherently low efficiency of the fuel would not improve even remotely as theoretically envisioned when a hollow core and boosting were incorporated, and a proposed test of such a core in an MK 4 high-explosive assembly was ultimately stricken from the preliminary shot schedule of operation Greenhouse. The predicted energy yield was around 1 kilotonne of TNT (4.2 TJ), if the core operated as originally expected the first rough estimate for the behaviour of the "hydride" bomb appeared in 1944, when James Conant forecasted that 1 kt of energy would be obtained from about 9 kg of UD 3. It was realised that the end result would be a fizzle instead of full-scale detonation of the device. In all, neutron moderation sharply reduced the efficiency of the weapon before the inertial confinement failed. : 258 In reality the result was that the slower neutrons delayed the reaction time too much by reducing the number of fission generations accomplished especially as the core expanded to reach its snowplow region (where all nuclear reactions cease), more neutrons could escape from the turbulent surface of the core, and before enough energy (for military applications) could be produced. At the same time, due to the moderating effect of deuterium, the compression requirements are (at least in principle) relaxed somewhat, which would permit assembly of additional fissile material in the core, as well as a radial-implosion assembly, which was much simpler and compact than the one destined for the MK 3. The result should have been a lower required critical mass, concordantly reducing the amount of pure 235U or 239Pu needed for a weapon explosion. The heavy hydrogen (deuterium) in uranium deuteride (UD 3) or plutonium deuteride (PuD 3) moderates (slows down) the neutrons, thereby increasing the nuclear cross section for neutron absorption. UD 3) in one version, and a BeO tamper with 8.45 kg of active material in another. A composite lead and B 4C tamper was envisioned, with about 10.5 kg of active material (i.e. It made use of uranium deuteride particles coated with paraffin (to reduce the pyrophoricity of UD 3) and boron-10 carbide (B 4C) wax distributed uniformly throughout the solid core. The "autocatalytic" design that emerged from this early research was "Elmer", the discontinued radial-implosion Mark 2 weapon. All other nuclear weapons programs have relied on fast neutrons in their weapons designs.ĭuring early phases of Manhattan Project, in 1943, uranium deuteride was investigated as a promising bomb material it was abandoned by early 1944 as it turned out such design would be inefficient. Both tests produced a yield comparable to 200 tons of TNT each, and were considered to be fizzles. Two uranium deuteride fueled bombs are known to have been tested, the Ruth and Ray test shots during Operation Upshot–Knothole. The nomenclature is used in a manner similar to the term "hydrogen bomb", where the latter employs deuterium and occasionally tritium. While the "hydride" might erroneously imply that the isotope used is hydrogen, only deuterium has been used for the bomb pits. The term hydride for this type of weapons has been subject to misunderstandings in the open literature. Bomb efficiency was adversely affected by the cooling of neutrons since the latter delays the reaction, as delineated by Rob Serber in his 1992 extension of the original Los Alamos Primer. Unlike all other fission-based weapon types, the concept relies on a chain reaction of slow nuclear fission (see neutron temperature). It used deuterium, an isotope of hydrogen, as a neutron moderator in a uranium-deuterium ceramic compact. The uranium hydride bomb was a variant design of the atomic bomb first suggested by Robert Oppenheimer in 1939 and advocated and tested by Edward Teller.
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