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The Clean And Environmentally Safe Advanced Reactor (CAESAR), a nuclear reactor concept that would use steam as a moderator to control delayed neutrons, will potentially be able to burn U is also used as a radiation shield – its alpha radiation is easily stopped by the non-radioactive casing of the shielding and the uranium's high atomic weight and high number of electrons are highly effective in absorbing gamma rays and x-rays.It is not as effective as ordinary water for stopping fast neutrons.Doppler broadening of U-238's neutron absorption resonances, increasing absorption as fuel temperature increases, is also an essential negative feedback mechanism for reactor control.Around 99.284% of natural uranium's mass is uranium-238, which has a half-life of 1.41 By December 2005, the only breeder reactor producing power was the 600-megawatt BN-600 reactor at the Beloyarsk Nuclear Power Station in Russia.A tamper which surrounds a fissile core works to reflect neutrons and to add inertia to the compression of the Pu-239 charge.As such, it increases the efficiency of the weapon and reduces the critical mass required.The Soviet Union's test of the "Tsar Bomba" in 1961 produced "only" 50 megatons of explosive power, over 90% of which came from fusion, because the U been used instead, the yield of the "Tsar Bomba" could have been well-above 100 megatons, and it would have produced nuclear fallout equivalent to one third of the global total that had been produced up to that time.The decay chain of U is commonly called the "radium series" (sometimes "uranium series").
Also, Japan's Monju breeder reactor is planned to be started, having been shut down since 1995, and both China and India have announced plans to build nuclear breeder reactors.
For example, an estimated 77% of the 10.4-megaton yield of the Ivy Mike thermonuclear test in 1952 came from fast fission of the depleted uranium tamper.
Because depleted uranium has no critical mass, it can be added to thermonuclear bombs in almost unlimited quantity.
Beginning with naturally occurring uranium-238, this series includes the following elements: astatine, bismuth, lead, polonium, protactinium, radium, radon, thallium, and thorium.
All are present, at least transiently, in any uranium-containing sample, whether metal, compound, or mineral.