• absorption cross s
  • This reaction has a quite small absorption cross section, making heavy water a good neutron moderator, and relatively little tritium is produced. (wikipedia.org)
  • Pu-240 does have a moderate thermal neutron absorption cross section, so that Pu-241 production in a thermal reactor becomes a significant fraction as large as Pu-239 production. (wikipedia.org)
  • Small amounts of tritium are liberated when 9 4Be nuclei absorb low energy neutrons in the three-step nuclear reaction 9 4Be + n → 4 2He + 6 2He , 6 2He → 6 3Li + β−, 6 3Li + n → 4 2He + 3 1H Note that 6 2He has a half-life of only 0.8 seconds, β− is an electron, and 6 3Li has a high neutron absorption cross-section. (wikipedia.org)

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  • fast neutron
  • In the most important reaction for natural production, a fast neutron (which must have energy greater than 4.0 MeV) interacts with atmospheric nitrogen: Worldwide, the production of tritium from natural sources is 148,000 terabecquerels per year. (wikipedia.org)
  • uranium
  • Plutonium (94Pu) is an artificial element, except for trace quantities resulting from neutron capture by uranium, and thus a standard atomic weight cannot be given. (wikipedia.org)
  • It contained 45,000 graphite blocks weighing 400 short tons (360 t) used as neutron moderators, and was fueled by 6 short tons (5.4 t) of uranium metal and 50 short tons (45 t) of uranium oxide. (wikipedia.org)
  • They discovered significant neutron multiplication in natural uranium, proving that a chain reaction might be possible. (wikipedia.org)
  • Fermi estimated that a fissioning uranium nucleus produced 1.73 neutrons on average. (wikipedia.org)
  • fragments
  • Because of their tremendous penetrating ability, neutrons can be very damaging to the human body, a fact well known by the U.S. military, which is developing a bomb designed to kill people (but preserve property) by emitting large quantities of lethal neutron fragments. (ratical.org)
  • reaction
  • Typical emission rates for alpha reaction neutron sources range from 1×106 to 1×108 neutrons per second. (wikipedia.org)
  • High-energy neutrons can also produce tritium from lithium-7 in an endothermic (a net heat consuming reaction) reaction, consuming 2.466 MeV. (wikipedia.org)
  • In order to efficiently convert the heat produced by the Nuclear Reaction into electricity, the water that moderates the neutron and cools the fuel elements is contained at pressures 150 times greater than atmospheric pressure. (nuclearinfo.net)
  • thermal
  • Therefore, it works as a neutron reflector and neutron moderator, effectively slowing the neutrons to the thermal energy range of below 0.03 eV, where the total cross section is at least an order of magnitude lower - exact value strongly depends on the purity and size of the crystallites in the material. (wikipedia.org)
  • beta
  • Beta radiation can be emitted from many substances released by nuclear bombs and power plants, including strontium 90 and tritium. (ratical.org)
  • energy
  • Neutron source variables include the energy of the neutrons emitted by the source, the rate of neutrons emitted by the source, the size of the source, the cost of owning and maintaining the source, and government regulations related to the source. (wikipedia.org)
  • Also contained in the nucleus are neutrons, which have no electrical charge but which are endowed with a "binding energy" that keeps the nucleus together. (ratical.org)
  • The low energy of tritium's radiation makes it difficult to detect tritium-labeled compounds except by using liquid scintillation counting. (wikipedia.org)
  • For applications in proposed fusion energy reactors, such as ITER, pebbles consisting of lithium bearing ceramics including Li2TiO3 and Li4SiO4, are being developed for tritium breeding within a helium cooled pebble bed (HCPB), also known as a breeder blanket. (wikipedia.org)
  • therefore
  • This is because atomic nuclei are generally kept apart because they contain positive electrical charges and therefore repel each other. (wikipedia.org)
  • The heaviest element possible in the universe would therefore be the one with the highest atomic mass of all nuclei located above this half-life limit. (historyrundown.com)
  • physics
  • The term Atomic Number is defined in nuclear physics as the number of protons in a nucleus and is given the symbol Z . From your chemistry you will remember that this number also defines the position of an element in the Periodic Table of Elements . (wikibooks.org)
  • half life
  • While tritium has several different experimentally determined values of its half-life, the National Institute of Standards and Technology lists 4,500 ± 8 days (12.32 ± 0.02 years). (wikipedia.org)
  • moderator
  • Even so, cleaning tritium from the moderator may be desirable after several years to reduce the risk of its escaping to the environment. (wikipedia.org)