Effect of heat treatment on neutron attenuation characteristics of high density concretes (HDC)

In nuclear reactor and fuel cycle facilities, apart from ordinary concrete (2300 kg/m3) various special types of concrete of density varying in range 3600-4600 kg/m3have been effectively employed to achieve less shielding thickness. Radiation attenuation in concrete mainly depend on types of aggregate used; water to cement ratio, elemental composition and moisture content apart from density of concrete. In addition to this, operating temperature also plays a vital role in deciding its shielding properties due to loss of water content and microcracking. The effect of heat on neutron attenuation properties of HDC upon heat exposure is the scope of the study in this paper. Four types of concrete made of granite and having hematite and steel shots as aggregate were prepared with density varying from 2300 to 4300 kg/m3and exposed to 120 °C for durations (14, 28 and 56 days). Neutron Attenuation Factor (NAF) was obtained from experimental study and compared with results obtained with neutron transport calculations. The results of this study clearly indicate that the sustained and cyclic heat treatment at 120 °C up to 56 days reduced the neutron attenuation factor by a factor of two.