{"id":12465,"date":"2016-08-04T17:48:41","date_gmt":"2016-08-04T17:48:41","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=12465"},"modified":"2022-10-17T13:23:00","modified_gmt":"2022-10-17T13:23:00","slug":"boron-10","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/glossary\/boron-10\/","title":{"rendered":"Boron 10"},"content":{"rendered":"
Natural boron<\/strong> consists primarily of two stable isotopes<\/strong>, 11<\/sup>B (80.1%) and \u00a010<\/sup>B (19.9%)<\/strong>.\u00a0In nuclear industry boron is commonly used as a neutron absorber<\/strong> due to the high neutron cross-section<\/a> of isotope \u00a010<\/sup>B<\/strong>. Its (n,alpha) reaction<\/strong> cross-section for thermal neutrons<\/a> is about 3840 barns<\/strong> (for 0.025 eV neutron). Isotope \u00a011<\/sup>B\u00a0has absorption cross-section for thermal neutrons about 0.005 barns (for 0.025 eV neutron). Most of (n,alpha) reactions of thermal neutrons are 10B(n,alpha)7Li<\/strong> reactions accompanied by 0.48 MeV gamma emission<\/a>.<\/p>\n <\/a><\/p>\n Moreover, isotope 10<\/sup>B has a high (n, alpha) reaction cross-section along the entire neutron energy spectrum<\/a>. The cross-sections of most other elements become very small at high energies, as in the case of cadmium<\/a>. The cross-section of 10<\/sup>B\u00a0decreases monotonically with energy. For fast neutrons,<\/strong> its cross-section is on the order of barns<\/strong>.<\/p>\n Boron, as the neutron absorber, has another positive property. The reaction products<\/strong> (after a neutron absorption), helium and lithium, are stable isotopes<\/strong>. Therefore there are minimal problems with decay heating of control rods or burnable absorbers used in the reactor core.<\/p>\n On the other hand production of helium may lead to a significant increase in pressure (under rod cladding) when used as the absorbing material in control rods<\/a>. Moreover, 10<\/sup>B is the principal source of radioactive tritium in the primary circuit of all PWRs<\/a> (which use boric acid as a chemical shim) because reactions with neutrons can rarely lead to the formation of radioactive tritium via:<\/p>\n 10B(n,2x alpha)3H<\/strong>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0threshold reaction (~1.2 MeV)<\/p>\n and<\/p>\n 10B(n,alpha)7Li(n,n+alpha)3H<\/strong>\u00a0 \u00a0threshold reaction (~3 MeV).<\/p>\n See also: Tritium<\/a><\/p>\n<\/div><\/div>