Nodular cast iron - contg. lanthanide(s) with high absorption cross=section for neutrons, and suitable for mfg. contains for spent nuclear fuel elements

摘要

The iron contains 2-4% C, 1-3% Si, and, all maxima, 0.5% Mn, 0.1% P, 0.025% Mg, 2% Ni, 0.8% Mo; and also 0.05-0.8% lanthanides with high absorption cross-section for neutrons. The pref. iron contains a ferritic matrix and 3.3-3.8% C, 1.8-2.5% Si, and, all maxima, 0.2% Mn, 0.08% P, 0.025% Mg; plus 0.08-0.5% Gd or Sm, and possibly other lanthanides, the rest being iron and trace impurities. The nodular iron is pref. used as containers for the storage and transport of spent fuel elements removed from nuclear reactors. The sulphur content of the molten iron is pref. reduced to below 0.01% before adding the lanthanides. The mfr. of screens, walls etc. 100 mm or more in thickness, blocking the passage of beta- and gamma-rays and neutrons, esp. thermal neutrons.