Measurement and Analysis of Induced Activities in Concrete Components Irradiated by 14-MeV Neutrons

The principal components of concrete were irradiated by 14-MeV neutrons for measurement of their induced activities to verify the activation calculation code THIDA-2 and its related cross-section library CROSSLIB. The observed radioactive nuclides, whose half-lives range from minutes to years, were ²⁸Al, ²⁹Al, ²⁷Mg, ⁴⁴K, ⁴¹Ar, ⁵⁶Mn, ⁴²K, ²⁴Na, ⁴³K, ⁴⁸Sc, ⁴⁷Sc, ⁴⁷Ca, ⁴⁶Sc, ⁵⁴Mn, and ²²Na, Experimental and calculated results were compared. Good agreement was obtained within ±20%, for ²⁸Al, ⁵⁶Mn, ⁴²K, ²⁴Na, ⁴⁸Sc, ⁴⁷Ca, ⁴⁶Sc, and ⁵⁴Mn with well-estimated production cross sections. Large differences were also observed, however, ranging in value from −50 to +100%, for the other nuclides. The cross-section values near 14 MeV for these nuclides were replaced with the cross-section data measured at the Fusion Neutronics Source at the Japan Atomic Energy Research Institute. Recalculation was performed using the newly estimated group cross sections derived from these data, and agreement between experiment and calculation was improved to within ±20%. From this experimental study, it was proved that the uncertainties of the activation cross-section values could satisfactorily explain the discrepancies of the induced activity calculation.